Tag Archive for: Jyoti Jaiswal

illustration of laser damaging the plasma membrane

The microscopic world of cell healing: A window into future therapies

illustration of laser damaging the plasma membrane from Advanced Science coverUnraveling how cells mend after injury serves as a key to unlocking potential therapies. Recent findings from the Center for Genetic Medicine Research at Children’s National Hospital offered surprising insights into the cell’s healing mechanisms by illuminating the intricate cellular responses to various types of injuries.

The study, featured on the back cover of the latest issue of Advanced Science, found that cells respond in distinct ways depending on the type of injury, such as a traumatic muscle tear that creates a large injury or tiny holes in the cell membrane caused by pathogenic proteins. Daniel Bittel, DPT, Ph.D., a research postdoctoral fellow at the Center for Genetic Medicine Research, said that cells are routinely injured from even everyday activities, such as walking up a flight of stairs.

“Injuries often involve damage to the plasma membrane,” Bittel said. “We wanted to investigate how healing happens at the subcellular level to better understand diseases and develop targeted therapies. We were especially curious about muscle cells because, interestingly, healthy ones get stronger the more that they are injured.”

The fine print

Using the center’s unique, custom-built microscope, the research team zoomed in on the process of cellular healing to watch how cells activate repair after injuries. Using a laser to damage the plasma membrane, they mimicked mechanically induced trauma. They also used a pathogen-derived protein to create nanoscale pinprick injuries in a cell’s plasma membrane that resemble those that are seen after strenuous muscle exertion.

Then, they watched as cells went to work within seconds, engaging healing mechanisms tailored to the type of injury. In the case of a cell facing numerous pinpricks along the cell membrane, it immediately deployed the endocytic pathway used by the cells to eat and drink. This process helped remove the injurious agents and the tiny holes they made. However, with a larger mechanical injury, the cells demonstrated patience, allowing the plasma membrane to seal before clearing up the damage by the same endocytic pathway.

 The big picture

The paper is part of an ongoing body of research on cell injury that will inform future investigations into a wide range of pediatric health issues including muscular dystrophies, injuries to neurons, orthopedic injuries from sports and other mechanical damage to tissues.

Jyoti Jaiswal, M.Sc., Ph.D., senior investigator at the Center for Genetic Medicine Research, said this work is foundational in the development of new therapies. “Knowing where the problem lies will help us figure out what therapy will work best and target the therapy to address the specific deficit,” he said. “This work will pave the way to help tailor therapies and tackle diseases more effectively.”

RSV infected infant cells

$2.13M grant accelerates treatments for kids with Down syndrome experiencing respiratory viruses

RSV infected infant cells

Children’s National Hospital received a combined $2.13 million award from the National Institutes of Health’s (NIH) National Heart, Lung and Blood Institute to better understand the mechanisms of severe viral respiratory infections in patients with Down syndrome and to develop new diagnostic tools and innovative precision medicine approaches for this vulnerable population.

“We have a unique opportunity to discover novel targets that can treat severe viral respiratory infections, including SARS-CoV-2,” said Gustavo Nino, M.D., M.S.H.S., D’A.B.S.M., principal investigator in the Center for Genetic Medicine at Children’s National. “Part of the award will help us accelerate the development of these novel approaches to prevent severe respiratory infections caused by SARS-CoV-2 and other viruses like respiratory syncytial virus infection (RSV) in children and adults with Down syndrome.”

Lower respiratory tract infections are a leading cause of hospitalization and death in children with Down syndrome. Those children have a nine times higher risk for hospitalization and mortality due to respiratory viruses that cause lower respiratory tract infections.

Chromosome 21, which is an extra chromosome copy found in patients with Down syndrome, encodes four of the six known interferon receptors, leading to hyperactivation of interferon response in Down syndrome. With the central role of interferons focused on antiviral defense, it remains puzzling how interferon hyperactivation contributes to severe viral lower respiratory tract infections in children with Down syndrome. This is an area that the researchers will explore to better manage and treat viral lower respiratory tract infections in these patients, with the support of NIH’s INCLUDE initiative. INCLUDE provides institutions with grants to help clinical research and therapeutics to understand and diminish risk factors that influence the overall health, longevity, and quality of life for people with Down syndrome related to respiratory viruses.

“While many of the other studies focus on intellectual and other disabilities, we are exploring a novel viral respiratory infectious disease mechanism and are doing so by working directly with patients and patient-derived samples,” said Jyoti Jaiswal, M.Sc., Ph.D., senior investigator in the Center for Genetic Medicine Research at Children’s National.

Children with Down syndrome have historically been excluded in research related to airway antiviral immunity, which is a focus of this human-based transformative study to improve the health and survival of patients with Down syndrome. There is a critical need for studies that define targetable molecular and cellular mechanisms to address dysregulated antiviral responses in this patient population.

“The clinical expertise at Children’s National in studying Down syndrome and the work of our team in caring for these patients with respiratory and sleep disorders positions us well to pursue this work,” said Jaiswal. “This is further supplemented by our initial studies that have identified a novel mechanism of impaired airway antiviral responses in these patients.”

Congresswoman Eleanor Holmes Norton (D-DC) also celebrated Children’s National and its NIH research funding benefitting people with Down syndrome.

“I am pleased to congratulate Dr. Nino and staff on being the recipients of the National Heart, Lung, & Blood Institute grant. You were chosen from a competitive group of applicants and should be proud of this notable achievement,” said Norton in a letter. “By receiving this grant, you have demonstrated outstanding promise in your field. It is my hope that this grant will enable you to better the local and global community.”

Injury triggered change in ER calcium of a muscle cell

ER maintains ion balance needed for muscle repair

Injury triggered change in ER calcium of a muscle cell

A new study led by Jyoti Jaiswal, M.Sc., Ph.D., principal investigator at Children’s National Hospital, identifies that an essential requirement for the repair of injured cells is to cope with the extracellular calcium influx caused by injury to the cell’s membrane. Credit: Goutam Chandra, Ph.D.

Physical activity can injure our muscle cells, so their ability to efficiently repair is crucial for maintaining muscle health. Understanding how healthy muscle cells respond to injury is required to understand and treat diseases caused by poor muscle cell repair.

A new study led by Jyoti Jaiswal, M.Sc., Ph.D., principal investigator at Children’s National Hospital, identifies that an essential requirement for the repair of injured cells is to cope with the extracellular calcium influx caused by injury to the cell’s membrane.

This study, published in the Journal of Cell Biology, identifies endoplasmic reticulum (ER) – a network of membranous tubules in the cell – as the site where the calcium entering the injured cell is sequestered. Using limb girdle muscular dystrophy 2L (LGMD2L) patient cells and a model for this genetic disease, the study shows impaired ability of diseased muscle cells to cope with this calcium excess. It also shows that a drug to sequester excess calcium counters this ion imbalance and reverses the diseased cell’s repair deficit.

“The study provides a novel insight into how injured cells in our body cope with calcium ion imbalance during injury,” Dr. Jaiswal explained. “This work also addresses how calcium homeostasis is compromised by a genetic defect that leads to LGMD2L. It also offers a proof of principle approach to restore calcium homeostasis, paving the path for future work to develop therapies targeting this disease.”

According to Dr. Jaiswal, this work also addresses the current lack of understanding of the basis for exercise intolerance and other symptoms faced by LGMD2L patients.

“This study opens the path for developing targeted therapies for LGMD2L and provides a fundamental cellular insight into a process crucial for cell survival,” said Goutam Chandra, Ph.D., research fellow and lead author of this study.

The Center for Genetic Medicine Research at Children’s National is among only a handful across the world to study this rare disease. These findings are unprecedented in providing the mechanistic insights needed to develop treatment for it.

In addition to Dr. Jaiswal and Chandra, the study co-authors include Sreetama Sen Chandra, Ph.D., Davi Mazala, Ph.D., and Jack VanderMeulen, Ph.D., from Children’s National, and Karine Charton, Ph.D., and Isabelle Richard, Ph.D., from Université Paris-Saclay.

muscle cells

Experimental model mimics early-stage myogenic deficit in boys with DMD

muscle cells

Muscle regeneration marked by incorporation of muscle stem cell nuclei (green) in the myofibers (red) in dystrophic muscles with low TGFβ level (upper image), but not with high TGFβ level (lower image). Inflammatory and other nuclei are labeled blue.

Boys with Duchenne muscular dystrophy (DMD) experience poor muscle regeneration, but the precise reasons for this remain under investigation. An experimental model of severe DMD that experiences a large spike in transforming growth factor-beta (TGFβ) activity after muscle injury shows that high TGFβ activity suppresses muscle regeneration and promotes fibroadipogenic progenitors (FAPs). This leads to replacement of the damaged muscle fibers by calcified and connective tissue, compromising muscle structure and function. While blocking FAP buildup provides a partial solution, a Children’s National Hospital study team identifies correcting the muscle micro-environment caused by high TGFβ as a ripe therapeutic target.

The team’s study was published online March 26, 2020, in JCI Insight.

DMD is a chronic muscle disease that affects 1 in 6,200 young men in the prime of their lives. The disorder, caused by genetic mutations leading to the inability to produce dystrophin protein, leads to ongoing muscle damage, chronic inflammation and poor regeneration of lost muscle tissue. The patients experience progressive muscle wasting, lose the ability to walk by the time they’re teenagers and die prematurely due to cardiorespiratory failure.

The Children’s National team finds for the first time that as early as preadolescence (3 to 4 weeks of age), their experimental model of severe DMD disease showed clear signs of the type of spontaneous muscle damage, regenerative failure and muscle fiber loss seen in preadolescent boys who have DMD.

“In boys, the challenge due to muscle loss exists from early in their lives, but had not been mimicked previously in experimental models,” says Jyoti K. Jaiswal, MSc, Ph.D., principal investigator in the Center for Genetic Medicine Research at Children’s National, and the study’s co-senior author. “TGFβ is widely associated with muscle fibrosis in DMD, when, in fact, our work shows its role in this disease process is far more significant.”

Research teams have searched for experimental models that replicate the sudden onset of symptoms in boys who have DMD as well as its complex progression.

“Our work not only offers insight into the delicate balance needed for regeneration of skeletal muscle, but it also provides quantitative information about muscle stem cell activity when this balanced is disturbed,” says Terence A. Partridge, Ph.D., principal investigator in the Center for Genetic Medicine Research at Children’s National, and the study’s co-senior author.

This schematic depicts the fate of injured myofibers in healthy or dystrophic muscle

This schematic depicts the fate of injured myofibers in healthy or dystrophic muscle (WT or mdx experimental models) that maintain low TGFβ level, compared with D2-mdx experimental models that experience a large increase in TGFβ level. As the legend shows, various cells are involved in this regenerative response.

“The D2-mdx experimental model is a relevant one to use to investigate the interplay between inflammation and muscle degeneration that is seen in humans with DMD,” adds Davi A.G. Mázala, co-lead study author.  “This model faithfully recapitulates many features of the complex disease process seen in humans.”

Between 3 to 4 weeks of age in the experimental models of severe DMD disease, the level of active TGFβ spiked up to 10-fold compared with models with milder disease. Intramuscular injections of an off-the-shelf drug that inhibits TGFβ signaling tamped down the number of FAPs, improving the muscle environment by lowering TGFβ activity.

“This work lays the foundation for studies that could lead to future therapeutic strategies to improve patients’ outcomes and lessen disease severity,” says James S. Novak, Ph.D., principal investigator in Children’s Center for Genetic Medicine Research, and co-lead study author. “Ultimately, our goal is to improve the ability of patients to continue to maintain muscle mass and regenerate muscle.”

In addition to Mázala, Novak, Jaiswal and Partridge, Children’s National study co-authors include Marshall W. Hogarth; Marie Nearing; Prabhat Adusumalli; Christopher B. Tully; Nayab F. Habib; Heather Gordish-Dressman, M.D.; and Yi-Wen Chen, Ph.D.

Financial support for the research described in this post was provided by the National Institutes of Health under award Nos. T32AR056993, R01AR055686 and U54HD090257; Foundation to Eradicate Duchenne; Muscular Dystrophy Association under award Nos. MDA295203, MDA480160 and MDA 477331; Parent Project Muscular Dystrophy; and Duchenne Parent Project – Netherlands.

mitochondria

Molecular gatekeepers that regulate calcium ions key to muscle function

mitochondria

Controlled entry of calcium ions into the mitochondria, the cell’s energy powerhouses, makes the difference between whether muscles grow strong or easily tire and perish from injury, according to research published in Cell Reports.

Calcium ions are essential to how muscles work effectively, playing a starring role in how and when muscles contract, tap energy stores to keep working and self-repair damage. Not only are calcium ions vital for the repair of injured muscle fibers, their controlled entry into the mitochondria, the cell’s energy powerhouses, spells the difference between whether muscles will be healthy or if they will easily tire and perish following an injury, according to research published Oct. 29, 2019, in Cell Reports.

“Lack of the protein mitochondrial calcium uptake1 (MICU1) lowers the activation threshold for calcium uptake mediated by the mitochondrial calcium uniporter in both, muscle fibers from an experimental model and fibroblast of  a patient lacking MICU1,” says Jyoti K. Jaiswal, MSc, Ph.D., a principal investigator in the Center for Genetic Medicine Research at Children’s National Hospital and one of the paper’s corresponding authors. “Missing MICU1 also tips the calcium ion balance in the mitochondria when muscles contract or are injured, leading to more pronounced muscle weakness and myofiber death.”

Five years ago, patients with a very rare disease linked to mutations in the mitochondrial gene MICU1 were described to suffer from a neuromuscular disease with signs of muscle weakness and damage that could not be fully explained.

To determine what was going awry, the multi-institutional research team used a comprehensive approach that included fibroblasts donated by a patient lacking MICU1 and an experimental model whose MICU1 gene was deleted in the muscles.

Loss of MICU1 in skeletal muscle fibers leads to less contractile force, increased fatigue and diminished capacity to repair damage to their cell membrane, called the sarcolemma. Just like human patients, the experimental model suffers more pronounced muscle weakness, increased numbers of dead myofibers, with greater loss of muscle mass in certain muscles, like the quadriceps and triceps, the research team writes.

“What was happening to the patient’s muscles was a big riddle that our research addressed,” Jaiswal adds. “Lacking this protein is not supposed to make the muscle fiber die, like we see in patients with this rare disease. The missing protein is just supposed to cause atrophy and weakness.”

Patients with this rare disease show early muscle weakness, fluctuating levels of fatigue and lethargy, muscle aches after exercise, and elevated creatine kinase in their bloodstream, an indication of cell damage due to physical stress.

“One by one, we investigated these specific features in experimental models that look normal and have normal body weight, but also show lost muscle mass in the quadriceps and triceps,” explains Adam Horn, Ph.D., the lead researcher in Jaiswal’s lab who conducted this study. “Our experimental model lacking MICU1 only in skeletal muscles responded to muscle deficits so similar to humans that it suggests that some of the symptoms we see in patients can be attributed to MICU1 loss in skeletal muscles.”

Future research will aim to explore the details of how the impact of MICU1 deficit in muscles may be addressed therapeutically and possible implications of lacking MICU1 or its paralog in other organs.

In addition to Jaiswal and Horn, Children’s National Hospital Center for Genetic Medicine Research co-authors include Marshall W. Hogarth and Davi A. Mazala. Additional co-authors include Lead Author Valentina Debattisti, Raghavendra Singh, Erin L. Seifert, Kai Ting Huang, and Senior Author György Hajnóczky, all from Thomas Jefferson University; and Rita Horvath, from Newcastle University.

Financial support for research described in this post was provided by the National Institutes of Health under award numbers R01AR55686, U54HD090257 and RO1 GM102724; National Institute of Arthritis and Musculoskeletal and Skin Diseases under award number T32AR056993; and Foundation Leducq.