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Gustavo Nino

New method may facilitate childhood respiratory research

Gustavo Nino

“The use of CRC is a potentially powerful translational approach to shed light on the molecular mechanisms that control airway epithelial immune responses in infants and young children. This novel approach enables us to study the origins of respiratory disease and its chronic progression through childhood and beyond,” observes Gustavo Nino, M.D., a Children’s pulmonologist and study senior author.

A new method perfected by a team at Children’s National Health System may help expand research into pulmonary conditions experienced by infants and children, an understudied but clinically important age group. The study describing the new technique was published in the December 2017 print edition of Pediatric Allergy and Immunology.

Using conditionally reprogrammed cells (CRCs), a technique that enables indefinite proliferation of cells in the lab, the team was able to produce cell cultures that have a number of advantages over standard cultures and that may make it easier and more efficient to conduct research into pediatric respiratory immune responses.

The epithelial cells that line human airways are crucial in controlling immune responses to viruses, allergens and other environmental factors. The function and dysfunction of these airway epithelial cells (AECs) play a key role in asthma, cystic fibrosis and other pulmonary conditions, many of which begin in early life.

To generate enough of these cells for research, scientists culture AECs from primary nasal and bronchial cell samples. Cells derived from adults have fueled research leading to new therapies and the discovery of key biomarkers. But little comparable research has been conducted in infants. Airway sampling in premature infants has not been reported, likely to due to airway size limitations and underlying comorbidities. Similarly, sampling in infants is limited by the need for bronchoscopy and sedation.

“A major barrier has been the lack of a good system to culture epithelial cells, since airway sampling in infants and children is a challenge,” says co-lead author, Geovanny F. Perez, M.D., co-director of Children’s Severe Bronchopulmonary Dysplasia Program. “We needed a better way to culture cells in this age group.”

While primary AECs do not survive long in the lab, that hurdle was recently overcome by a process that generates CRCs from the primary AECs of adults, making it possible to quickly generate cell cultures from specimens.

In this study, the Children’s team adapted that approach, producing CRCs from primary AECs of neonates and infants. The CRC induction successfully enabled AEC cultures from infants born prematurely and from bronchial specimens of young children.

Geovanny Perez

“A major barrier has been the lack of a good system to culture epithelial cells, since airway sampling in infants and children is a challenge,” says co-lead author, Geovanny F. Perez, M.D., co-director of Children’s Severe Bronchopulmonary Dysplasia Program. “We needed a better way to culture cells in this age group.”

“We found that the CRCs have longer cell life and greater proliferation ability than standard cultures of epithelial cells. They preserved their original characteristics even after multiple experiments. And, they presented an innate immune response similar to that seen in primary human epithelial cells during viral respiratory responses in children,” says Dr. Perez.

“The use of CRC is a potentially powerful translational approach to shed light on the molecular mechanisms that control airway epithelial immune responses in infants and young children. This novel approach enables us to study the origins of respiratory disease and its chronic progression through childhood and beyond,” observes Gustavo Nino, M.D., a Children’s pulmonologist and study senior author.

The authors note that further studies are needed to define more precisely the differences and similarities in the immune responses of CRC and non-CRC derived from primary AEC. However, they conclude that CRC represents a new, effective method to study AEC innate immune responses in infants.

In addition to Drs. Perez and Nino, Children’s Center for Genetic Medicine Research co-authors include Co-Lead Author S. Wolf; Lana Mukharesh; Natalia Isaza Brando, M.D.; Diego Preciado, M.D., Ph.D.; Robert J. Freishtat, M.D., M.P.H.; Dinesh Pillai, M.D.; and M. C. Rose.

Financial support for this research was provided by the National Institute of Allergy and Infectious Diseases under grant number R21AI130502; Eunice Kennedy Shriver National Institute of Child Health and Human Development under grant number HD001399; National Heart, Lung and Blood Institute under grant number HL090020; and National Center for Advancing Translational Sciences under grant number UL1TR000075.

Zhe Han, PhD

Key to genetic influence of APOL1 on chronic kidney disease

Zhe Han

Drosophila melanogaster nephrocytes share structural and functional similarities with human renal cells, making the fruit fly an ideal pre-clinical model for studying how the APOL1 gene contributes to renal disease in humans.

Using the Drosophila melanogaster pre-clinical model, a Children’s National Health System research team identified a key mechanism by which the APOL1 gene contributes to chronic kidney disease in people of African descent. The model exploits the structural and functional similarities between the fruit fly’s nephrocytes and renal cells in humans to give scientists an unprecedented ability to study gene-to-cell interactions, identify other proteins that interact with APOL1 in renal disease, and target novel therapies, according to a paper published November 18 in the Journal of the American Society of Nephrology.

“This is one of the hottest research topics in the kidney field. We are the first group to generate this result in fruit flies,” says Zhe Han, Ph.D., a senior Drosophila specialist and associate professor in the Center for Cancer & Immunology Research at Children’s National. Han, senior author of the paper, presented the study results this month during Kidney Week 2016, the American Society of Nephrology’s annual gathering in Chicago that was expected to draw more than 13,000 kidney professionals from around the world.

The advantages of Drosophila for biomedical research include its rapid generation time and an unparalleled wealth of sophisticated genetic tools to probe deeply into fundamental biological processes underlying human diseases. People of African descent frequently inherit a mutant version of the APOL1 gene that affords protection from African sleeping sickness, but is associated with a 17- to 30-fold greater chance of developing certain types of kidney disease. That risk is even higher for individuals infected with the human immunodeficiency virus (HIV). Drosophila renal cells, called nephrocytes, accurately mimic pathological features of human kidney cells during APOL1-associated renal disease.

“Nephrocytes share striking structural and functional similarities with mammalian podocytes and renal proximal tubule cells, and therefore provide us a simple model system for kidney diseases,” says Han, who has studied the fruit fly for 20 years and established the fly nephrocyte as a glomerular kidney disease model in 2013 with two research papers in the Journal of the American Society of Nephrology.

In this most recent study, Han’s team cloned a mutated APOL1 gene from podocyte cells cultured from a patient with HIV-associated nephropathy. They created transgenic flies making human APOL1 in nephrocytes and observed that initially the transgene caused increased cellular functional activity. As flies aged, however, APOL1 led to reduced cellular function, increased cell size, abnormal vesicle acidification, and accelerated cell death.

“The main functions of nephrocytes are to filter proteins and remove toxins from the fly’s blood, to reabsorb protein components, and to sequester harmful toxins. It was surprising to see that these cells first became more active and temporarily functioned at higher levels,” says Han. “The cells got bigger and stronger but, ultimately, could not sustain that enhancement. After swelling to almost twice their normal size, the cells died. Hypertrophy is the way that the human heart responds to stress overload. We think kidney cells may use the same coping mechanism.”

The Children’s research team is a multidisciplinary group with members from the Center for Cancer & Immunology Research, the Center for Genetic Medicine Research, and the Division of Nephrology. The team also characterized fly phenotypes associated with APOL1 expression that will facilitate the design and execution of powerful Drosophila genetic screening approaches to identify proteins that interact with APOL1 and contribute to disease mechanisms. Such proteins represent potential therapeutic targets. Currently, transplantation is the only option for patients with kidney disease linked to APOL1.

“This is only the beginning,” Han says. “Now, we have an ideal pre-clinical model. We plan to start testing off-the-shelf therapeutic compounds, for example different kinase inhibitors, to determine whether they block any of the steps leading to renal cell disease.”