Nephrology

little girl in hosptial corridor

A growing list of factors that impact CKD severity for kids

little girl in hosptial corridor

Myriad biological and societal factors can impact the occurrence and accelerate progression of chronic kidney disease for children of African descent – including preterm birth, exposure to toxins during gestation and lower socioeconomic status – and can complicate these children’s access to effective treatments.

Myriad biological and societal factors can impact the occurrence and accelerate progression of chronic kidney disease (CKD) for children of African descent – including preterm birth, exposure to toxins during gestation and lower socioeconomic status – and can complicate these children’s access to effective treatments, according to an invited commentary published in the November 2018 edition of American Journal of Kidney Diseases.

Clinicians caring for “these vulnerable children should be mindful of these multiple competing and compounding issues as treatment options are being considered along the continuum from CKD to kidney failure to transplantation,” writes Marva Moxey-Mims, M.D., chief of the Division of Nephrology at Children’s National Health System.

The supplemental article was informed by lessons learned from The Chronic Kidney Disease in Children (CKiD) longitudinal study and conversations that occurred during the Frank M. Norfleet Forum for Advancement of Health, “African Americans and Kidney Disease in the 21st Century.”

African American children represent 23 percent of the overall population of kids with CKD in the CKiD study. While acquired kidney diseases can get their start during childhood when the diseases betray few symptoms, the full impact of illness may not be felt until adulthood. A number of factors can uniquely affect children of African descent, heightening risk for some kids who already are predisposed to suffering more severe symptoms. These include:

  • Preterm birth. African American children make up 36 percent of patients in CKiD with glomerular disease, which tends to have faster progression to end-stage renal disease. These diseases impair kidney function by weakening glomeruli, which impairs the kidneys’ ability to clean blood. Patients with a high-risk apolipoprotein L1 (APOL1) genotype already are at higher risk for focal segmental glomerulosclerosis (FSGS) and CKD. Researchers hypothesize that preterm birth may represent “a second hit that facilitates the development of glomerular damage resulting from the high-risk genotype.” According to the Centers for Disease Control and Prevention, 1 in 10 U.S. infants in 2016 was born preterm, e.g., prior to 37 weeks gestation.
  • APOL1 genotype. Compared with children who had a low-risk genotype and FSGS, children with a high-risk genotype had higher rates of uncontrolled hypertension, left ventricular hypertrophy, elevated C-reactive protein levels and obesity.
  • Human immunodeficiency viral (HIV) status. About 65 percent of U.S. children with HIV-1/AIDS are African American. In a recent nested case-control study of children infected with HIV in the womb, infants with high-risk APOL1 genotypes were 3.5 times more likely to develop CKD with viral infection serving as “a likely second hit.”
  • Access to kidney transplant. African American adults experience a faster transition to end-stage renal disease and are less likely to receive kidney transplants. African American children with CKD from nonglomerular diseases begin renal replacement therapy 1.6 years earlier than children of other races, after adjusting for socioeconomic status. Their wait for dialysis therapy was 37.5 percent shorter. However, these African American children waited 53.7 percent longer for transplants. Although donor blood types, genetic characteristics and other biological factors each play contributing roles, “these findings may reflect sociocultural and institutional differences not captured by socioeconomic status,” Dr. Moxey-Mims writes.

To alleviate future health care disparities, she suggests that additional research explore the impact of expanding services to pregnant women to lower their chances of giving birth prematurely; early childhood interventions to help boost children’s educational outcomes, future job prospects and income levels; expanded studies about the impact of environmental toxicities on prenatal and postnatal development; and heightened surveillance of preterm infants as they grow older to spot signs of kidney disease earlier to slow or prevent disease progression.

“Clinicians can now begin to take into account genetics, socioeconomic status and the impact of the built environment, rather than blaming people and assuming that their behavior alone brought on kidney disease,” Dr. Moxey-Mims adds. “Smoking, not eating properly and not exercising can certainly make people vulnerable to disease. However, there are so many factors that go into developing a disease that patients cannot control: You don’t control to whom you’re born, where you live or available resources where you live. These research projects will be useful to help us really get to the bottom of which factors we can impact and which things can’t we prevent but can strive to mitigate.”

The article covered in this post is part of a supplement that arose from the Frank M. Norfleet Forum for Advancement of Health: African Americans and Kidney Disease in the 21st Century, held March 24, 2017, in Memphis, Tennessee. The Forum and the publication of this supplement were funded by the Frank M. Norfleet Forum for Advancement of Health, the Community Foundation of Greater Memphis and the University of Tennessee Health Science Center.

Marva Moxey Mims

Making the case for a comprehensive national registry for pediatric CKD

Marva Moxey Mims

“It’s of utmost importance that we develop more sensitive ways to identify children who are at heightened risk for developing CKD.,” says Marva Moxey-Mims, M.D. “A growing body of evidence suggests that this includes children treated in pediatric intensive care units who sustained acute kidney injury, infants born preterm and low birth weight, and obese children.”

Even though chronic kidney disease (CKD) is a global epidemic that imperils cardiovascular health, impairs quality of life and heightens mortality, very little is known about how CKD uniquely impacts children and how kids may be spared from its more devastating effects.

That makes a study published in the November 2018 issue of the American Journal of Kidney Diseases all the more notable because it represents the largest population-based study of CKD prevalence in a nationally representative cohort of adolescents aged 12 to 18, Sun-Young Ahn, M.D., and Marva Moxey-Mims, M.D., of Children’s National Health System, write in a companion editorial published online Oct. 18, 2018.

In their invited commentary, “Chronic kidney disease in children: the importance of a national epidemiological study,” Drs. Ahn and Moxey-Mims point out that pediatric CKD can contribute to growth failure, developmental and neurocognitive defects and impaired cardiovascular health.

“Children who require renal-replacement therapy suffer mortality rates that are 30 times higher than children who don’t have end-stage renal disease,” adds Dr. Moxey-Mims, chief of the Division of Nephrology at Children’s National. “It’s of utmost importance that we develop more sensitive ways to identify children who are at heightened risk for developing CKD. A growing body of evidence suggests that this includes children treated in pediatric intensive care units who sustained acute kidney injury, infants born preterm and low birth weight, and obese children.”

At its early stages, pediatric CKD usually has few symptoms, and clinicians around the world lack validated biomarkers to spot the disease early, before it may become irreversible.

While national mass urine screening programs in Japan, Taiwan and Korea have demonstrated success in early detection of CKD, which enabled successful interventions, such an approach is not cost-effective for the U.S., Drs. Ahn and Moxey-Mims write.

According to the Centers for Disease Control and Prevention, 1 in 10 U.S. infants in 2016 was born preterm, prior to 37 weeks gestation. Because of that trend, the commentators advocate for “a concerted national effort” to track preterm and low birth weight newborns. (These infants are presumed to have lower nephron endowment, which increases their risk for developing end-stage kidney disease.)

“We need a comprehensive, national registry just for pediatric CKD, a database that represents the entire U.S. population that we could query to glean new insights about what improves kids’ lifespan and quality of life. With a large database of anonymized pediatric patient records we could, for example, assess the effectiveness of specific therapeutic interventions, such as angiotensin-converting enzyme inhibitors, in improving care and slowing CKD progression in kids,” Dr. Moxey-Mims adds.

Connecting allied health professionals in pediatric nephrology

With the meeting in Washington this year, Children’s National Health System will be the local host, a distinct honor for an academic medical center that treats hundreds of nephrology patients each year, says pediatric Nephrologist Asha Moudgil, M.D., who directs Children’s kidney transplant service.

Pediatric nephrology is a relatively small specialty worldwide, encompassing just a few hundred doctors in the U.S. For each allied health field that provides collaborative care with these physicians – including nutrition, child-life, psychology and social work – the numbers of providers are even smaller. There are no national meetings for these individual subspecialty fields and no venues to meet new like-minded colleagues or learn about new research or protocols.

Six years ago, the American Society of Pediatric Nephrology (ASPN) aimed to help resolve this dilemma by launching a new multidisciplinary symposium that brings together allied health professionals of all kinds within pediatric nephrology.

Each year, the “ASPN Multidisciplinary Symposium” changes locations, allowing the meeting to target different regional groups of allied health professionals based on geography. With the meeting in Washington this year, Children’s National Health System will be the local host, a distinct honor for an academic medical center that treats hundreds of nephrology patients each year, says pediatric Nephrologist Asha Moudgil, M.D., who directs Children’s kidney transplant service.

There are multiple advantages to having the symposium in Washington, Dr. Moudgil explains. One is access to Children’s experts in this field, who have a wealth of experience in managing issues that affect patients who live in the greater Washington area. For example, the keynote address scheduled for the meeting’s opening night will be delivered by Jennifer Verbesey, M.D., Children’s surgical director of pediatric kidney transplantation, focusing on living donation in minority populations. Living kidney donors and recipients who are minorities have unique issues that can affect organ longevity, explains Dr. Moudgil, which may not be well known by all clinicians.

Children’s speakers also focus prominently in the main session on the second day, including:

  • Angela Boadu, RD, LDN/LD, a registered dietitian, and Kaushalendra Amatya, Ph.D., a psychologist, are giving a talk about nutrition and the psychosocial aspects of obesity
  • Surgeon Evan Nadler, M.D., director of Children’s Bariatric Surgery Program, is speaking about bariatric surgery before and after transplantation
  • Nurse Practitioner Christy Petyak, CPNP-PC, and Social Worker Heidi Colbert, LICSW, CCTSW, NSW-C, are leading breakout sessions about the practical aspects of immunosuppressive therapy and resources for uninsured patients
  • Amatya, the Children’s psychologist, also is leading a breakout session on internalizing psychological disorders in pediatric renal patients and
  • Registered Dietitian Kristen Sgambat, Ph.D., RD, and Dr. Moudgil are co-leading a breakout session on nutritional challenges and enteral supplementation in chronic kidney disease.

Another advantage to holding the meeting in the nation’s capital is its close proximity to government research and federal regulatory agencies, such as the Food and Drug Administration (FDA) and the National Institutes of Health (NIH). Speakers from both agencies will be present, talking about how the FDA approves medicines for pediatric patients and offering details about the NIH’s rare disease program.

Besides the abundance of more formal knowledge-sharing, Dr. Moudgil adds, there will be plenty of opportunities for attendees to network, making connections within and outside their own respective fields.

“This is a platform for making long-term professional relationships,” Dr. Moudgil says. “Even if you’re the sole clinician representing your specialty at your own institution, you’ll be able to connect with other specialists at institutions across the country. You’re not only acquiring new information, you’re acquiring a group of colleagues you can connect with this year and those professional relationships can extend far into the future.”

Making the grade: Children’s National is nation’s Top 5 children’s hospital

Children’s National rose in rankings to become the nation’s Top 5 children’s hospital according to the 2018-19 Best Children’s Hospitals Honor Roll released June 26, 2018, by U.S. News & World Report. Additionally, for the second straight year, Children’s Neonatology division led by Billie Lou Short, M.D., ranked No. 1 among 50 neonatal intensive care units ranked across the nation.

Children’s National also ranked in the Top 10 in six additional services:

For the eighth year running, Children’s National ranked in all 10 specialty services, which underscores its unwavering commitment to excellence, continuous quality improvement and unmatched pediatric expertise throughout the organization.

“It’s a distinct honor for Children’s physicians, nurses and employees to be recognized as the nation’s Top 5 pediatric hospital. Children’s National provides the nation’s best care for kids and our dedicated physicians, neonatologists, surgeons, neuroscientists and other specialists, nurses and other clinical support teams are the reason why,” says Kurt Newman, M.D., Children’s President and CEO. “All of the Children’s staff is committed to ensuring that our kids and families enjoy the very best health outcomes today and for the rest of their lives.”

The excellence of Children’s care is made possible by our research insights and clinical innovations. In addition to being named to the U.S. News Honor Roll, a distinction awarded to just 10 children’s centers around the nation, Children’s National is a two-time Magnet® designated hospital for excellence in nursing and is a Leapfrog Group Top Hospital. Children’s ranks seventh among pediatric hospitals in funding from the National Institutes of Health, with a combined $40 million in direct and indirect funding, and transfers the latest research insights from the bench to patients’ bedsides.

“The 10 pediatric centers on this year’s Best Children’s Hospitals Honor Roll deliver exceptional care across a range of specialties and deserve to be highlighted,” says Ben Harder, chief of health analysis at U.S. News. “Day after day, these hospitals provide state-of-the-art medical expertise to children with complex conditions. Their U.S. News’ rankings reflect their commitment to providing high-quality care.”

The 12th annual rankings recognize the top 50 pediatric facilities across the U.S. in 10 pediatric specialties: cancer, cardiology and heart surgery, diabetes and endocrinology, gastroenterology and gastrointestinal surgery, neonatology, nephrology, neurology and neurosurgery, orthopedics, pulmonology and urology. Hospitals received points for being ranked in a specialty, and higher-ranking hospitals receive more points. The Best Children’s Hospitals Honor Roll recognizes the 10 hospitals that received the most points overall.

This year’s rankings will be published in the U.S. News & World Report’s “Best Hospitals 2019” guidebook, available for purchase in late September.

child in wheelchair with mom

Potential to replace race as a risk factor for kidney-transplant failure

child in wheelchair with mom

Right now, more than 100,000 adult and pediatric patients in the U.S. are waiting for a life-saving kidney donation. Thirteen of them die each day while awaiting a transplant. However, a significant portion of kidneys from deceased donors are discarded because they literally don’t make the grade – a scoring system known as the kidney donor profile index (KDPI) that aims to predict how long a donor kidney will last in an intended recipient based on a variety of factors, including the donor’s age, size and health history.

Ethnicity and race are also part of that scoring system, explains Marva Moxey-Mims, M.D., FASN, chief of the Division of Nephrology at Children’s National Health System. That’s partly because research over the years has suggested that kidneys from certain racial groups, including African-Americans, may not have the same longevity as those from other groups.

But race might not be the right marker to consider, Dr. Moxey-Mims counters. More recent studies have shown that a particular gene known as APOL1 might better predict risk of kidney-transplant failure. APOL1 high-risk variants are associated with a wide range of kidney diseases, with retrospective studies suggesting that they could be a key cause of failure in some donated kidneys. Although this gene is found almost exclusively in people of recent African descent, only about 13 percent of that population has high-risk APOL1 variants that might cause kidney problems.

“Instead of putting all African-American donor kidneys in one proverbial ‘bucket,’ we might be able to use this gene to determine if they truly carry a higher risk of early failure,” Dr. Moxey-Mims says.

To more definitively confirm whether this gene could be used as a proxy for heightened kidney-failure risk, Dr. Moxey-Mims and colleagues across the country are participating in the APOL1 Long-Term Kidney Transplantation Outcomes Network (APOLLO) study, she and Dr. Barry Freedman explain in a perspective published online April 27, 2018, in Clinical Journal of the American Society of Nephrology. The APOLLO study will tap people accessing the hundreds of transplant centers scattered across the nation, prospectively genotyping deceased and living African-American kidney donors as well as kidney-transplant recipients to assess whether they carry high-risk APOL1 gene variants. Living donors and transplant recipients will be followed for years to gauge how their kidneys fare over time.

The researchers, Dr. Moxey-Mims explains, hope to answer whether the APOL1 high-risk gene variants in donor kidneys could replace race as a risk factor when calculating the KDPI score and whether recipients’ own APOL1 gene variants impact transplant failure risk. They also hope to better understand the risk to living donors. “If a living donor has an increased risk of kidney failure,” she adds, “he or she can make a more educated decision about whether to donate a kidney.”

Dr. Moxey-Mims plays a pivotal role as the chair of the study’s steering committee, a group made up of the study’s principal investigators at all 13 clinical sites and the Data Coordinating Center, as well as the program officials from the National Institutes of Health funding institutes (National Institute of Diabetes and Digestive and Kidney Diseases, National Institute of Allergy and Infectious Diseases, and National Institute on Minority Health and Health Disparities). She will play a key part in helping to ensure that the study stays on track with recruitment goals, as well as publicizing the study at national meetings.

The study also includes a Community Advisory Council, a group made up of stakeholders in this study: 26 African-Americans who either have donated a kidney, received a kidney donation, are on dialysis awaiting a kidney transplant, or have a close relative in one of those categories. This group has helped to steer the study design in multiple ways, Dr. Moxey-Mims explains. For example, they have worked with study leaders to simplify the language on consent forms, helped to delineate which data study participants might want to receive when the study is completed, and helped to publicize the study in their communities by giving talks at churches and other venues.

Eventually, Dr. Moxey-Mims says APOLLO study researchers hope that clarifying the role of the APOL1 gene in kidney-transplant failure could lead to fewer discarded kidneys, which could boost the number of available kidneys for patients awaiting transplants.

“Down the road, the pool of patients awaiting transplant might have access to more kidneys because available organs aren’t getting a bad score simply because the donor is African-American,” she says. “We hope this might shorten the wait for some patients and their families who are desperate to get that call that a kidney is finally available.”

Financial support for research reported in the post was provided by the National Institutes of Health under grant numbers R01 DK084149, R01 DK070941 and U01 DK116041.

pill bottles and pills

New treatment approach shows promise for patients with stage IV Wilms tumor

The study assessed the benefit of adding two additional chemotherapy agents, cyclophosphamide and etoposide, to the treatment regimen for patients with incomplete lung nodule response or tumor loss of heterozygosity (LOH) at chromosomes 1p and 16q, both associated with interior outcomes in previous studies.

Wilms tumor, which first develops in the kidneys, is the fifth most common cancer in children under 15 years old. While overall outcomes for patients with Wilms tumor are excellent, patients with metastatic disease, with the lung as the most common site of spread, fare worse than patients with localized disease. That’s why a new study showing significantly improved survival rates for patients with stage IV Wilms tumors with lung metastases is making waves in the pediatric oncology community.

The study, “Treatment of Stage IV Favorable Histology Wilms Tumor With Lung Metastases: A Report From the Children’s Oncology Group AREN0533 Study” – recently published in the Journal of Clinical Oncology with Jeffrey Dome, M.D., Ph.D., vice president for the Center for Cancer and Blood Disorders at Children’s National Health System, as the senior author – assessed whether lung radiation therapy, part of the standard treatment in combination with chemotherapy drugs, can be avoided for patients with complete lung nodule response after six weeks of chemotherapy. Conversely, the study assessed the benefit of adding two additional chemotherapy agents, cyclophosphamide and etoposide, to the treatment regimen for patients with incomplete lung nodule response or tumor loss of heterozygosity (LOH) at chromosomes 1p and 16q, both associated with interior outcomes in previous studies. The results show that:

  • The new approach to therapy resulted in a 4-year overall survival rate of 96 percent, compared to 84 percent on the predecessor study.
  • About 40 percent of patients with Wilms tumor and lung metastases can be spared initial upfront lung radiation and still have outstanding survival. This will decrease the long-term risk of heart toxicity and breast cancer.
  • Patients with incomplete lung nodule response after six weeks of therapy with cyclophosphamide and etoposide had significantly better 4-year event-free survival: 89 percent compared with 75 percent that was expected based on historical data.
  • Intensification of therapy for patients with LOH at 1p and 16q was highly effective: 4-year event-free survival rate improved from 66 percent on the previous study to 100 percent.

“These findings will change clinical practice and improve survival for patients with Wilms tumor whose cancer has spread to the lungs” said Dr. Dome. “The risk-adapted approach to treatment based on tumor biology and tumor response provides a framework for future studies as we come one step closer to achieving 100 percent survival without treatment-associated side effects.”

Love is in the air and, for parasites, inside our bodies

Michael H. Hsieh

As featured in a PBS video, schistosome worms form lifelong bonds and females produce thousands of eggs daily only when they live inside human hosts, says Michael H. Hsieh, M.D., Ph.D.

“Love is in the air, the sea, the earth and all over and inside our bodies,” the PBS Valentine’s Day-themed video begins. As the public television station notes, what humans consider romance can look vastly different for creatures big and small, including serenading mice, spiders who wrap their gifts in silk and necking giraffes.

The “spooning” parasites segment of the video is where viewers see research conducted by Michael H. Hsieh, M.D., Ph.D., director of the Clinic for Adolescent and Adult PedIatric OnseT UroLogy at Children’s National Health System, and video filmed in his lab.

Schistosomiasis, a chronic infection with schistosome worms, is a distinctly one-sided love affair. As shown in Dr. Hsieh’s video clips, the male worm is shorter and fatter and equipped with a groove, a love canal where the longer, thinner female lodges, enabling the pair to mate for decades. This lifelong bond and the thousands of eggs it produces daily can only occur when the worms are inside the human host, Dr. Hsieh says.

While the video stresses Valentine’s Day romance, there are few rosy outcomes for humans who are the subject of the schistosome worms’ attention.

“Heavily and chronically infected individuals can have lots of problems,” Dr. Hsieh says. “This is a stunting and wasting health condition that prevents people from reaching their growth potential, impairs their academic performance and leaves them sapped of the energy needed to exercise or work. It truly perpetuates a cycle of poverty, particularly for affected children.”

Even the potential bright spot in this sobering story, the ability of the body’s immune system to fend off the parasitic worms, is only partly good news.

Schistosome worms have co-evolved with their human hosts, learning to take advantage of human vulnerabilities. Take the immune system. If it kicks too far into overdrive in trying to wall off the eggs from the rest of the body, it can interfere with organ function and trigger liver failure, kidney failure and early onset of bladder cancer, he says.

However, Dr. Hsieh and other schistosomiasis researchers are working on ways to positively harness the human immune response to schistosome worms, including developing diagnostics, drugs and vaccines. He says he and his colleagues would “love” to eliminate schistosomiasis as a global scourge.

antibodies-illustration

Detecting and treating dnDSA early preserves allograft function

antibodies-illustration

Monitoring and treating de novo donor-specific antibodies (dnDSA) before they could cause graft damage helped to decrease dnDSA in a majority of pediatric kidney transplant recipients at Children National Health System and prevented graft failure in the first few years.

Development of de novo donor-specific antibodies (dnDSA) is known to cause graft failure. Therefore, a protocol aimed at prospective monitoring and treating dnDSA – before they can cause graft damage – was developed for kidney transplant recipients at Children National Health System. This helped to decrease dnDSA in 76 percent of pediatric patients and prevented graft failure in the first few years, indicates a longitudinal cohort study published online Jan. 22, 2018, in Pediatric Transplantation. However, the benefit of preserving function of transplanted kidneys came at a price: Heightened hospitalization rates for infection.

An estimated 20 percent to 30 percent of children develop dnDSA and many of these patients go on to develop allograft failure after three to six years, write the study authors.

Clinical signs of graft failure due to antibodies appear too late to safeguard long-term graft survival. According to the study authors, developing earlier methods to detect dnDSA offers the opportunity to intervene before irreversible graft injury occurs.

“Children’s National Health System instituted a routine protocol that standardizes monitoring and treatment of dnDSA,” says Asha Moudgil, M.D., FASN, associate chief of the Division of Nephrology at Children’s National and the study’s senior author. “We followed this protocol as we monitored and treated all children younger than 19 who received a kidney transplant at Children’s National from Jan. 1, 2008, to Dec. 31, 2013.”

After transplant, these children were monitored for development of dnDSA at six months and then yearly. Upon detection of DSA, these children underwent kidney biopsy to assess for acute rejection. Additionally, monitoring was intensified to every two months.

“Our patients did not have a statistically significant increase in graft loss or dysfunction, suggesting that early and targeted treatment of dnDSA may benefit patients,” says Asha Moudgil, M.D., FASN.

Sixty-seven of the 72 children who received kidney transplants during that six-year period were included in this retrospective analysis. Their mean age was 14.1 years. Acute cellular rejection was treated according to a prespecified protocol.

  • The team treated de novo DSA with high-dose intravenous immunoglobulin (IVIG) if antibody titers were low and added two doses of rituximab to that treatment regimen if antibody titers were high.
  • If either C1q binding of immunodominant DSA was present or C4d+ were seen on biopsy, six sessions of plasma exchange were added to the above protocol.
  • Kids who were resistant to such treatment approaches received an additional four doses of IVIG monthly.

Nearly 39 percent of the children developed dnDSA within a median of 1.36 years. Ten of these 26 children had increased creatinine, 12 had new onset proteinuria and six had newly diagnosed hypertension at the time the dnDSA was detected. The multivariate analysis found that the coefficient of variance of tacrolimus, which measures adherence to immunosuppressive drugs, was the only statistically significant predictor for developing dnDSA.

DSA-positive patients had a higher rate of admissions (1.23 hospital admissions for infectious- or immunosuppressive-related side effects per patient, compared with 0.59 hospital admissions for the DSA-negative patients), which the study team attributes to aggressive treatment of dnDSA.

“Our patients did not have a statistically significant increase in graft loss or dysfunction, suggesting that early and targeted treatment of dnDSA may benefit patients,” Dr. Moudgil adds. “There was a higher risk of treatment-related complications, however, and this risk must be balanced against the short-term benefit of prolonging allograft function.”

Study co-authors include Olga Charnaya, M.D., a Children’s fellow when the study was designed and the article was drafted, now at Johns Hopkins; and Children’s Nephrologist, Shamir Tuchman, M.D.

Lisa M. Guay-Woodford, M.D

Internationally renowned pediatric nephrologist named to NIH advisory council

Lisa M. Guay-Woodford, M.D

Pediatric nephrologist Lisa M. Guay-Woodford, M.D., has been named to a three-year term as adviser serving on the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) Kidney, Urologic and Hematologic Diseases subcouncil.

Dr. Guay-Woodford, Director of the Center for Translational Science at Children’s National, is an internationally recognized expert in the mechanisms that modulate the clinical severity of certain inherited renal disorders, such as autosomal recessive polycystic kidney disease. She holds the Richard L. and Agnes F. Hudson Professorship in Health Services Research at Children’s National.

NIDDK, like other grant-awarding institutes within the National Institutes of Health (NIH), looks to its advisory councils for feedback on procedures that govern staff and manage its grant portfolios. The institute, the fifth largest at the NIH, supports clinical research about internal medicine and related subspecialties for many of the most common chronic health conditions.

“It is a tremendous honor to be asked to serve on this important council. I look forward to providing advice and perspective on the exciting portfolio of NIDDK-funded projects,” Dr. Guay-Woodford says.

Zhe Han

Research led by Zhe Han featured on cover of JASN, leading kidney disease journal

Journal of the American Society of Nephrology September 2017 cover

Coenzyme Q10, one of the best-selling nutrient supplements to support heart health also could be beneficial for kidney health, according to research conducted in transgenic fruit flies that was led by Zhe Han, Ph.D., associate professor at Children’s Center for Cancer and Immunology Research.

Nephrocytes, filtration kidney cells in Drosophila, require the Coq2 gene for protein reabsorption, toxin sequestration and critical cell ultrastructure.  Silencing the Coq2 gene results in aberrantly localized nephrocyte slit diaphragms and deformed lacunar channels, Han and co-authors found. Nephrocytes closely resemble the podocytes of the human kidney.

The research team’s paper, published online April 2017, this fall was featured on the cover of Journal of the American Society of Nephrology, the No. 1 kidney disease journal.

“I am honored that the JASN editors chose to feature my lab’s work on the cover of this prestigious journal,” Han says. “This underscores the utility of our gene-replacement approach, which silenced the fly homolog in the tissue of interest – here, the kidney cells – and provided a human gene to supply the silenced function.”

pill bottles and pills

Enhancing pediatric nephrology clinical trial development

Fewer than 50 percent of pharmaceuticals approved by federal authorities are explicitly approved for use in kids, and even fewer devices are labeled for pediatric use.

When children develop kidney disease, it can play out in dramatically different ways. They can experience relatively mild disorders that respond to existing treatments and only impact their lives for the short term. Children also can develop chronic kidney disease that defies current treatments and can imperil or end their lives.

Fewer than 50 percent of pharmaceuticals approved by federal authorities are explicitly approved for use in kids, and even fewer devices are labeled for pediatric use. Congress has offered incentives to manufacturers who study their treatments in children, but the laws do not require drug makers to demonstrate statistical significance or for the clinical trial to improve or extend children’s lives.

To overcome such daunting obstacles, the American Society of Pediatric Nephrology established a Therapeutics Development Committee to forge more effective public-private partnerships and to outline strategies to design and carry out pediatric nephrology clinical trials more expeditiously and effectively.

“We have seen how other pediatric subspecialties, such as cancer and arthritis, have leveraged similar consortia to address mutual concerns and to facilitate development of new therapeutics specific to those diseases,” says Marva Moxey-Mims, M.D., chief of the Division of Nephrology at Children’s National Health System and a founding committee member. “As a group, we aim to collectively identify and remedy the most pressing needs in pediatric nephrology. As just one example, the committee could help to increase the number of sites that host research studies, could expand the pool of potential study volunteers and could lower the chances of duplicating efforts.”

A paper summarizing their efforts thus far, “Enhancing clinical trial development for pediatric kidney diseases,” written by Dr. Moxey-Mims and 15 co-authors, was published online Aug. 30 by Pediatric Research. The journal’s editors will feature the review article in the “Editor’s Focus” of an upcoming print edition of the publication.

The committee is comprised of academic pediatric nephrologists, patient advocates, private pharmaceutical company representatives and public employees at the Food and Drug Administration and the National Institutes of Health. But it is likely to grow in size and in stakeholder diversity.

Already, committee members have learned that they achieve better results by working together. Early communication can avoid flaws in designing clinical trials, such as overestimating the volume of clinical samples that can feasibly be collected from a small child, or that could misinterpret the type of data needed to secure federal approval.

While public and private investigators took similar approaches to clinical trial design, academic investigators were more conceptual as they summarized their study design Road Map. Industry representatives, by contrast, included more granular detail about study organization and milestones along the path toward regulatory approval.

According to the study authors, both groups understand the critical role that patients and families can play in early research study design, such as accelerating patient recruitment, bolstering the credibility of research and helping to translate research results into actual clinical practice.

“We are pleased to have created a forum that allows participants to share valuable viewpoints and concerns and to understand how regulations and laws could be changed to facilitate development of effective medicines for children with kidney disease,” says Dr. Moxey-Mims. “We hope the relationships and trust forged through these conversations help to speed the development and approval of the next generation of therapies for pediatric renal disease.”

A close-up of Dr. Marva Moxey Mims at Children's National.

Children’s National welcomes Marva Moxey-Mims, M.D., renowned nephrologist, as incoming Division Chief

A close-up of Dr. Marva Moxey Mims at Children's National.

Marva Moxey-Mims, M.D., a leading expert in chronic kidney disease and glomerular disease who has conceptualized and overseen multicenter clinical studies aimed at improving chronic kidney disease treatment, has been named Chief of Pediatric Nephrology at Children’s National Health System.

Dr. Moxey-Mims comes to Children’s National from the National Institute of Diabetes and Digestive and Kidney Diseases at the National Institutes of Health where she served as Deputy Director for clinical science and oversaw a research portfolio that included clinical trials for kidney disease and genitourinary dysfunction in adults and children. As Pediatric Nephrology Division Chief, Dr. Moxey-Mims plans to add new staff and restructure a division already ranked among the nation’s leaders by U.S. News & World Report in order to carve out dedicated time for research and improve care for children with kidney disease.

”Children’s National is honored to welcome Dr. Moxey-Mims as the new leader for our talented nephrology team,” says Robin Steinhorn, M.D., senior vice president of the Center for Hospital-Based Specialties. “She brings unparalleled expertise in this field, is a member of a number of influential national committees and has authored more than 90 scientific publications, including peer-reviewed articles and book chapters. Under her guidance, Pediatric Nephrology at Children’s is well-positioned to continue to lead the nation in clinical care and research.”

“I want to inspire the division,” Dr. Moxey-Mims says. “I want the faculty to be happy in their work here and to look forward to coming to work every day. I want them to have enough time to pursue their academic interests, so clinicians not only continue to provide excellent patient care but also can conduct research. All of the staff has potential projects in mind; it’s just a matter of finding the time to do them.”

From a pragmatic standpoint, Children’s pediatric nephrologists will start with what is feasible: Continuing and expanding current cross-disciplinary research projects.

“There are some research projects that will be important to pursue, but we just don’t have the building blocks in place right now to move in that specific direction,” Dr. Moxey-Mims says. “However, continuing ongoing collaborations with our colleagues in neonatology, oncology, hematology and urology are reasonable places to start. I agree with the cliché that success breeds success. If we have an established collaboration and can build on it, that is how we start expanding our research enterprise.”

To that end, the division is in the early stage of joining an existing consortium that is studying four types of glomerular disease, conditions caused by varying mechanisms that often lead to kidney failure. “Information that is gathered will inform care going forward,” she says. “Part of what is being done in these studies is obtaining a better understanding of how disease progresses in different groups of children and adults and quantifying the impact of varying treatment approaches. It’s very exciting for Children’s National to be a new player in this.”

Dr. Moxey-Mims received her undergraduate degree from McGill University in Montreal and her medical degree from Howard University in Washington, D.C. She completed her pediatric residency and clinical pediatric nephrology training at Children’s National and from 1994 to 1999 worked at Children’s National as a staff nephrologist.

“Returning to Children’s has been a wonderful homecoming,” Dr. Moxey-Mims says. “I wanted to return to the hospital setting and have direct exposure to patients. I missed that. In this new role, I can participate in patient care, as well as foster an environment that spurs even more research. It’s really the best of both worlds.”

little girl with cancer

New approach improves pediatric kidney cancer outcomes

little girl with cancerWilms tumor, also known as nephroblastoma, is the most common pediatric kidney cancer, typically seen in children ages three to four. Compared to patients with unilateral Wilms tumors, children with bilateral Wilms tumors (BWT) have poorer event-free survival (EFS) and are at higher risk for later effects such as renal failure. The treatment of BWT is challenging because it involves surgical removal of the cancer, while preserving as much healthy kidney tissue as possible to avoid the need for an organ transplant.

A new Children’s Oncology Group (COG) study published in the September issue of the Annals of Surgery demonstrated an exciting new approach to treating children diagnosed with BWT that significantly improved EFS and overall survival (OS) rates after four years when compared to historical rates. Jeffrey Dome, M.D., Ph.D., Vice President of the Center for Cancer and Blood Disorders at Children’s National Health System, was co-senior author of this first-ever, multi-institutional prospective study of children with BWT.

Historically, patients with BWT have had poor outcomes, especially if they have tumors with unfavorable histology. In this study, Dr. Dome and 18 other clinical researchers followed a new treatment approach consisting of three chemotherapy drugs before surgery rather than the standard two drug regimen, surgical removal of cancerous tissue within 12 weeks of diagnosis, and postoperative chemotherapy that was adjusted based on histology.

The study found that preoperative chemotherapy expedited surgical treatment, with 84 percent of patients having surgery within 12 weeks of diagnosis. The new treatment approach also vastly improved EFS and OS rates for patients participating in the study. The four-year EFS rate was 82.1 percent, compared to 56 percent on the predecessor National Wilms Tumor Study-5 (NWTS-5) study. The four-year OS rate was 94.9 percent, compared to 80.8 percent on NWTS-5.

“I am very encouraged by these results, which I believe will serve as a benchmark for future studies and lead to additional treatment improvements, giving more children the chance to overcome this diagnosis while sparing kidney tissue,” says Dr. Dome.

A total of 189 patients at children’s hospitals, universities and cancer centers in the United States and Canada participated in this study. These patients will continue to be followed for 10 years to track kidney failure rates. This study was funded by grants from the National Institutes of Health to the Children’s Oncology Group.

Patricio Ray

Toward a better definition for AKI in newborns

Patricio Ray

The National Institute of Diabetes and Digestive and Kidney Diseases convened a meeting of expert neonatologists and pediatric nephrologists, including Dr. Patricio Ray, to review state-of-the-art knowledge about acute kidney injury in neonates and to evaluate the best method to assess these patients’ kidney function.

Each year, thousands of infants in the United States end up in neonatal intensive care units (NICUs) with acute kidney injury (AKI), a condition in which the kidneys falter in performing the critical role of filtering waste products and excess fluid from the blood to produce urine. Being able to identify neonates during the early stages of AKI is critical to doctors and clinician-scientists who treat and study this condition, explains Patricio Ray, M.D., a nephrologist at Children’s National Health System.

Without an accurate definition and early identification of newborns with AKI, it is difficult for doctors to limit the use of antibiotics or other medications that can be harmful to the kidneys. Neonates who have AKI should not receive large volumes of fluids, a treatment that can cause severe complications when the kidneys do not properly function.

Until recently, there was no standard definition for AKI, leaving doctors and researchers to develop their own guidelines. Lacking set criteria led to confusion, Dr. Ray says. For example, different studies estimating the percentage of infants in NICUs with AKI ranged from 8 percent to 40 percent, depending on which definition was used. In 2012, a group known as the Kidney Disease Improved Global Outcome (KDIGO) issued practice guidelines for AKI that provide a standard for doctors and researchers to follow. They focus largely on measuring the relative levels of serum creatinine, a protein produced by muscles that is filtered by the kidneys, and the amount of urine output, which typically declines in adults and older children with failing kidneys.

The problem with these guidelines, Dr. Ray explains, is they are not sensitive enough to identify newborns experiencing the early stages of AKI during the first week of life. Newborns can have high serum creatinine levels during the first week of life due to residual levels transferred from mothers through the placenta. Also, because their kidneys are immature, failure often can mean higher – not diminished – urine production.

In 2013, the National Institute of Diabetes and Digestive and Kidney Diseases, part of the National Institutes of Health, convened a meeting of leading neonatologists and pediatric nephrologists – including Dr. Ray – to review state-of-the-art knowledge about AKI in neonates and to evaluate the best manner to assess kidney function in these patients. They published a summary of their discussion online June 12, 2017 in Pediatric Research.

Among other findings, the group concluded that the current definition of AKI lacks the sensitivity needed to identify the early stages of AKI in neonates’ first week of life. They also said that more research was needed to fill this gap.

That’s where Dr. Ray’s current research comes in. Working with fellow Children’s Nephrologist Charu Gupta, M.D., and Children’s Neonatologist An Massaro, M.D., the three clinician-scientists reviewed the medical records of 106 infants born at term with a condition known as hypoxic ischemic encephalopathy (HIE), in which the brain doesn’t receive enough oxygen. Not only does this often lead to brain injury, but it also greatly increases the risk of AKI.

Because these babies had been followed closely in the NICU to assess the possibility of AKI, their serum creatinine had been checked frequently. The researchers found that about 69 percent of the infants with HIE followed at Children’s National never developed signs of kidney failure during their first week of life. These babies’ serum creatinine concentrations dropped by 50 percent or more by the time they were 1 week old, about the same as reported previously in healthy neonates. Another 12 percent of the infants with HIE developed AKI according to the definition established by the KDIGO group in 2012. These infants:

  • Required more days of mechanical ventilation and medications to increase their blood pressure
  • Had higher levels of antibiotics in their bloodstreams
  • Retained more fluid
  • Had lower urinary levels of a molecule that their kidneys should have been cleared and
  • Had to stay in the hospital longer

A third group of the infants with HIE, about 19 percent, did not meet the standard criteria for AKI. However, these babies had a rate of decline of serum creatinine that was significantly slower than the normal newborns and the infants with HIE who had excellent outcomes. Rather, their outcomes matched those of infants with established AKI.

Dr. Ray notes that by following the rate of serum creatinine decline during the first week of life physicians could identify neonates with impaired kidney function. This approach provides a more sensitive method to identify the early stages of AKI in neonates. “By looking at how fast babies were clearing their serum creatinine compared with the day they were born, we could predict how well their kidneys were working,” he says. Dr. Ray and colleagues published these findings July 2016 in Pediatric Nephrology.

He adds that further studies will be necessary to confirm the utility of this new approach to assess the renal function of term newborns with other diseases and preterm neonates. Eventually, he hopes this new approach will become uniform clinical practice.

Zhe Han, PhD

Lab led by Zhe Han, Ph.D., receives $1.75 million from NIH

Zhe Han, PhD

A new four-year NIH grant will enable Zhe Han, Ph.D., to carry out the latest stage in the detective work to determine how histone-modifying genes regulate heart development and the molecular mechanisms of congenital heart disease caused by these genetic mutations.

The National Institutes of Health (NIH) has awarded $1.75 million to a research lab led by Zhe Han, Ph.D., principal investigator and associate professor in the Center for Genetic Medicine Research, in order to build models of congenital heart disease (CHD) that are tailored to the unique genetic sequences of individual patients.

Han was the first researcher to create a Drosophila melanogaster model to efficiently study genes involved in CHD, the No.1 birth defect experienced by newborns, based on sequencing data from patients with the heart condition. While surgery can fix more than 90 percent of such heart defects, an ongoing challenge is how to contend with the remaining cases since mutations of a vast array of genes could trigger any individual CHD case.

In a landmark paper published in 2013 in the journal Nature, five different institutions sequenced the genomes of more than 300 patients with CHD and their families, identifying 200 mutated genes of interest.

“Even though mutations of these genes were identified from patients with CHD, these genes cannot be called ‘CHD genes’ since we had no in vivo evidence to demonstrate these genes are involved in heart development,” Han says. “A key question to be answered: How do we efficiently test a large number of candidate disease genes in an experimental model system?”

In early 2017, Han published a paper in Elife providing the answer to that lingering question. By silencing genes in a fly model of human CHD, the research team confirmed which genes play important roles in development. The largest group of genes that were validated in Han’s study were histone-modifying genes. (DNA winds around the histone protein, like thread wrapped around a spool, to become packed into a higher-level structure.)

The new four-year NIH grant will enable Han to carry out the next stage of the detective work to determine precisely how histone-modifying genes regulate heart development. In order to do so, his group will silence the function of histone-modifying genes one by one, to study their function in the fly heart development and to identify the key histone-modifying genes for heart development. And because patients with CHD can have more than one mutated gene, he will silence multiple genes simultaneously to determine how those genes work in partnership to cause heart development to go awry.

By the end of the four-year research project, Han hopes to be able to identify all of the histone-modified genes that play pivotal roles in development of the heart in order to use those genes to tailor make personalized fly models corresponding to individual patient’s genetic makeup.

Parents with mutations linked to CHD are likely to pass heart disease risk to the next generation. One day, those parents could have an opportunity to sequence their genes to learn the degree of CHD risk their offspring face.

“Funding this type of basic research enables us to understand which genes are important for heart development and how. With this knowledge, in the near future we could predict the chances of a baby being born with CHD, and cure it by using gene-editing approaches to prevent passing disease to the next generation,” Han says.

US News Honor Roll 2017-18

Children’s National is #1 in Neonatology and Top 10 overall in U.S. News & World Report Survey

US News Honor Roll 2017-18Children’s National is proud to be named #1 in Neonatology in the U.S. News & World Report 2017-18 Best Children’s Hospitals survey. Also, Children’s National was once again named to the coveted Honor Roll, placing them among the Top 10 children’s hospitals in the country.

Being the #1 ranked Neonatology program reflects the quality of care throughout Children’s National because it requires the support and partnership of many other specialties, including cardiology, neurology and surgery. In addition to this honor, Children’s National ranked in the Top 10 in four additional services: Cancer (#7), Neurology and Neurosurgery (#9), Orthopedics (#9) and Nephrology (#10).  For the seventh year in a row, Children’s National has ranked in all ten services, a testament to the pediatric care experts across the organization and their commitment to children and families.

“This recognition is a great achievement for Children’s National, affirming our place as a premier destination for pediatric care, and the commitment of our people, partners and supporters to helping every child grow up stronger,” said Kurt Newman, M.D., President and CEO of Children’s National. “I’m particularly proud of our #1 ranking in Neonatology as, in many ways it reflects the quality of care across our hospital. Treating these tiny patients often encompasses many other specialties, including our Fetal Medicine Institute.”

Children’s National is dedicated to improving the lives of children through innovative research, expert care and advocacy on behalf of children’s needs. In addition to being recognized among the “best of the best” by U.S. News & World Report, Children’s National is a Magnet® designated hospital for excellence in nursing and is a Leapfrog Group Top Hospital. As a top NIH-funded pediatric health system, Children’s National marries cutting-edge research with the highest quality care, to deliver the best possible outcomes for children today and in the future.

Coenzyme Q10

Supplement might help kidney disease

Coenzyme Q10

A research team was able to “rescue” phenotypes caused by silencing the fly CoQ2 gene by providing nephrocytes with a normal human CoQ2 gene, as well as by providing flies with Q10, a popular supplement.

A new study led by Children’s National research scientists shows that coenzyme Q10 (CoQ10), a popular over-the-counter supplement sold for pennies a dose, could alleviate genetic problems that affect kidney function. The work, done in genetically modified fruit flies — a common model for human genetic diseases since people and fruit flies share a majority of genes — could give hope to human patients with problems in the same genetic pathway.

The new study, published April 20 by Journal of the American Society of Nephrology, focuses on genes the fly uses to create CoQ10.

“Transgenic Drosophila that carry mutations in this critical pathway are a clinically relevant model to shed light on the genetic mutations that underlie severe kidney disease in humans, and they could be instrumental for testing novel therapies for rare diseases, such as focal segmental glomerulosclerosis (FSGS), that currently lack treatment options,” says Zhe Han, Ph.D., principal investigator and associate professor in the Center for Cancer & Immunology Research at Children’s National and senior study author.

Nephrotic syndrome (NS) is a cluster of symptoms that signal kidney damage, including excess protein in the urine, low protein levels in blood, swelling and elevated cholesterol. The version of NS that is resistant to steroids is a major cause of end stage renal disease. Of the more than 40 genes that cause genetic kidney disease, the research team concentrated on mutations in genes involved in the biosynthesis of CoQ10, an important antioxidant that protects the cell against damage from reactive oxygen.

Drosophila pericardial nephrocytes perform renal cell functions including filtering of hemolymph (the fly’s version of blood), recycling of low molecular weight proteins and sequestration of filtered toxins. Nephrocytes closely resemble, in structure and function, the podocytes of the human kidney.  The research team tailor-made a Drosophila model to perform the first systematic in vivo study to assess the roles of CoQ10 pathway genes in renal cell health and kidney function.

One by one, they silenced the function of all CoQ genes in nephrocytes. If any individual gene’s function was silenced, fruit flies died prematurely. But silencing three specific genes in the pathway associated with NS in humans – Coq2, Coq6 and Coq8 – resulted in abnormal localization of slit diaphragm structures, the most important of the kidney’s three filtration layers; collapse of membrane channel networks surrounding the cell; and increased numbers of abnormal mitochondria with deformed inner membrane structure.

Journal of the American Society of Nephrology September 2017 cover

The flies also experienced a nearly three-fold increase in levels of reactive oxygen, which the study authors say is a sufficient degree of oxidative stress to cause cellular injury and to impair function – especially to the mitochondrial inner membrane. Cells rely on properly functioning mitochondria, the cell’s powerhouse, to convert energy from food into a useful form. Impaired mitochondrial structure is linked to pathogenic kidney disease.

The research team was able to “rescue” phenotypes caused by silencing the fly CoQ2 gene by providing nephrocytes with a normal human CoQ2 gene, as well as by providing flies with Q10, a readily available dietary supplement. Conversely, a mutant human CoQ2 gene from an patient with FSGS failed to rescue, providing evidence in support of that particular CoQ2 gene mutation causing the FSGS. The finding also indicated that the patient could benefit from Q10 supplementation.

“This represents a benchmark for precision medicine,” Han adds. “Our gene-replacement approach silenced the fly homolog in the tissue of interest – here, the kidney cells – and provided a human gene to supply the silenced function. When we use a human gene carrying a mutation from a patient for this assay, we can discover precisely how a specific mutation – in many cases only a single amino acid change – might lead to severe disease. We can then use this personalized fly model, carrying a patient-derived mutation, to perform drug testing and screening to find and test potential treatments. This is how I envision using the fruit fly to facilitate precision medicine.”

Related resources:
News release: Drosophila effectively models human genes responsible for genetic kidney diseases
Video: Using the Drosophila model to learn more about disease in humans

fruit fly

Studying fruit flies to better understand human kidneys

fruit fly

In his latest study, Zhe Han and co-authors zeroed in on Rab genes to determine their role in fruit fly renal function.

It’s a given that fruit flies and humans are different. Beyond the obvious are a litany of less-apparent distinctions. For example, fruit flies have hemolymph instead of blood. Arranged around a single cardiac chamber, compared with humans’ four-chamber hearts, are a group of cells called nephrocytes that serve the same function as human kidneys, filtering toxins and waste from hemolymph.

But despite the dissimilarities between these two organisms, fly nephrocytes and human kidney cells are similar enough to allow the fruit fly, a common lab model that shares about 60 percent of its DNA with people, to provide insights on kidney disease in people. In a new study in fruit flies led by Zhe Han, Ph.D., principal investigator and associate professor in the Center for Cancer and Immunology Research at Children’s National Health System, researchers identified several new genes thought to be critical for renal function in humans. The findings could lend insight to the inner workings of this organ down to the molecular level and eventually help further the understanding or treatment of kidney disorders.

Han explains that recent research by his group tied 80 fruit fly genes to renal function. Many of these newly identified genes were Rab GTPases, a family of genes that make proteins whose job is to move substances around in cells through membrane-enclosed pouches called vesicles. For example, Rab proteins might put some substances on the path to destruction by moving them into lysosomes, vesicles with enzymes that break down all kinds of biomolecules. Rab proteins might help other substances be reused by steering them into recycling endosomes, vesicles that shuttle biomolecules that are still useful to where they will be used next.

In their latest study, published online Feb. 8, 2017 in Cell & Tissue Research, Han and co-authors zeroed in on these Rab genes to determine their role in fruit fly renal function. The researchers accomplished this by using genetic alterations to shut down each gene selectively in fruit fly nephrocytes. They then evaluated these transgenic flies on a number of different characteristics, including ability to effectively filter proteins from the blood, whether toxins placed in their food accumulated in their nephrocytes, how they developed and how they survived.

Their findings readily identified five Rab genes that seemed more important for these functions than the others: Rabs 1, 5, 7, 11 and 35, which all have analogous genes in humans.

Peering into the nephrocytes of flies in which these three Rabs had been silenced, the researchers made critical discoveries. Turning off Rab 7 appeared to block the path toward biomolecules in the cell entering lysosomes. Rather than biomolecules being destroyed, they instead were shuttled to the recycling route. Turning off Rab 11 had the reverse effect; recycling endosomes were drastically reduced, while lysosomes dramatically increased. Turning off Rab 5 had the most striking effect: All vesicles going in or out were blocked – like a cellular traffic jam – filling the cell with biomolecules that had no place to go, Han says.

Han, who has long tracked renal-related mutations in humans, says that no patients with kidney disease have turned up so far with Rab mutations. These genes are critical for functions throughout the body, he explains, so any embryos with these mutations are unlikely to survive. However, he adds, a host of other renal-related genes work in parallel or are controlled by different Rabs. So understanding the role of Rabs in renal function provides some insight into how these genes operate as well as what might happen when the function of these genes goes awry.

Han plans to study how Rabs 5, 7 and 11 fit into networks of renal genes as well as the role of the other Rabs that could play novel roles in the nephrocyte cell trafficking.

“These findings in fly Rabs provide the framework to study the major causes of kidney disease in human patients,” he adds.

Cas9-mediated correction of metabolic liver disease

AAV.CRISPR-SaCas9

In vivo gene correction of the OTC locus in the mouse liver by AAV.CRISPR-SaCas9. Source: Nature Publishing Group copyright 2016.

PDF Version

What’s known

A deficiency of the enzyme ornithine transcarbamylase (OTC) in humans causes life-threatening hyperammonemic crises.  The OTC gene enables the body to make an enzyme that is a critical player in the urea cycle, a process that ensures excess nitrogen is excreted by the kidneys. Left unchecked, accumulating nitrogen becomes a toxic form of ammonia. Infants with OTC deficiency can suffer their first metabolic crisis as newborns. Up to 50 percent die or sustain severe brain injury, and survivors typically need a liver transplant by age 1. Gene therapy could cure OTC deficiency, but currently used viruses, such as adeno-associated virus (AAV), are not optimal in the neonatal setting.

What’s new

A research team led by Children’s National Health System and the University of Pennsylvania reasoned that the newborn liver may be an ideal setting for AAV-mediated gene correction using CRISPR-Cas9 gene editing. They intravenously infused two AAVs into two-day-old mice with partial OTC deficiency. One AAV expressed Cas9 and the other expressed a guide RNA and a donor OTC DNA. This resulted in correction of the mutation in 10 percent of liver cells and increased survival in mice challenged with a high-protein diet, which normally exacerbates disease. After consuming a high-protein diet for one week, the treated newborns had a 40 percent reduction in ammonia compared with the untreated group. The correction appears to last long term. The study “provides evidence for efficacy of gene editing in neonatal onset OTC deficiency,” says Mark L. Batshaw, M.D., Physician-In-Chief and Chief Academic Officer at Children’s National, and a study co-author. “This study provides convincing evidence for efficacy of in vivo genome editing in an authentic animal model of a lethal human metabolic disease,” the research team concludes.

Questions for future research

Q: More than 400 mutations can cause OTC deficiency, and each would require a separate gene-editing approach. Is it possible instead to insert the OTC genome using CRISPR-Cas9 to correct the disorder irrespective of the mutation?
Q: Will such gene editing also work in adult animal models of the OTC disorder?
Q: Do these encouraging results in animals translate to efficacy in infants?

Source: Yang, Y., L. Wang, P. Bell, D. McMenamin, Z. He, J. White, H. Yu, C. Xu, H. Morizono, K. Musunuru, M.L. Batshaw and J.M. Wilson. “A dual AAV system enables the Cas9-mediated correction of a metabolic liver disease in newborn mice.” Published Feb. 1, 2016 by Nature Biotechnology.

Zhe Han

Fruit flies can model human genetic kidney disease

Zhe Han

Zhe Han, Ph.D., has found that a majority of human genes known to be associated with nephrotic syndrome play conserved roles in renal function, from fruit flies to humans.

Drosophila melanogaster, the common fruit fly, has played a key role in genetic research for decades. Even though D. melanogaster and humans look vastly different, researchers estimate that about 75 percent of human disease-causing genes have a functional homolog in the fly.

A Children’s National Health System research team reported in a recent issue of Human Molecular Genetics that the majority of genes associated with nephrotic syndrome (NS) in humans also play pivotal roles in Drosophila renal function, a conservation of function across species that validates transgenic flies as ideal pre-clinical models to improve understanding of human disease.

NS is a cluster of symptoms that signal kidney damage, including excess protein in urine, low protein levels in blood, elevated cholesterol and swelling. Research teams have identified mutations in more than 40 genes that cause genetic kidney disease, but knowledge gaps remain in understanding the precise roles that specific genes play in kidney cell biology and renal disease. To address those research gaps, Zhe Han, Ph.D., a principal investigator and associate professor in the Center for Cancer & Immunology Research at Children’s National, and colleagues systematically studied NS-associated genes in the Drosophila model, including seven genes whose renal function had never been analyzed in a pre-clinical model.

“Eighty-five percent of these genes are required for nephrocyte function, suggesting that a majority of human genes known to be associated with NS play conserved roles in renal function from flies to humans,” says Han, the paper’s senior author. “To hone in on functional conservation, we focused on Cindr, the fly’s version of the human NS gene, CD2AP,” Han adds. “Silencing Cindr in nephrocytes led to dramatic impairments in nephrocyte function, shortened their life span, collapsed nephrocyte lacunar channels – the fly’s nutrient circulatory system – and effaced nephrocyte slit diaphragms, which diminished filtration function.”

And, to confirm that the phenotypes they were studying truly caused human disease, they reversed the damage by expressing a wild-type human CD2AP gene. A mutant allele derived from a patient with CD2AP-associated NS did not rescue the phenotypes.

Thus, the Drosophila nephrocyte can be used to explain the clinically relevant molecular mechanisms underlying the pathogenesis of most monogenic forms of NS, the research team concludes. “This is a landmark paper for using the fly to study genetic kidney diseases,” Han adds. “For the first time, we realized that the functions of essential kidney genes could be so similar from the flies to humans.”

A logical next step will be to generate personalized in vivo models of genetic renal diseases bearing patient-specific mutations, Han says. These in vivo models can be used for drug screens to identify treatments for kidney diseases that currently lack therapeutic options, such as most of the 40 genes studies in this paper as well as the APOL1 gene that is associated with the higher risk of kidney diseases among millions of African Americans.