Tag Archive for: Jyoti K. Jaiswal

Microscopic visual of a diseased muscle section

Gene therapy offers potential long-term treatment for limb-girdle muscular dystrophy 2B

Microscopic visual of a diseased muscle section

Microscopic visual of a diseased muscle section. Credit: Daniel Bittel.

Children’s National Hospital experts developed a new pre-clinical gene therapy for a rare disorder, known as limb-girdle muscular dystrophy (LGMD) 2B, that addresses the primary cellular deficit associated with this disease. Using a single injection of a low dose gene therapy vector, researchers restored the ability of injured muscle fibers to repair in a way that reduced muscle degeneration and enhanced the functioning of the diseased muscle. The treatment was safe, attenuated fibro-fatty muscle degeneration, and restored myofiber size and muscle strength, according to the study published in the Journal of Clinical Investigation.

With an incidence of less than 1 in 100,000, LGMD2B is a rare disorder caused by a genetic mutation in a large gene called dysferlin. This faulty gene leads to muscle weakness in the arms, legs, shoulder and pelvic girdle. Affected children and adults face trouble walking, climbing stairs and getting out of chairs. Individuals typically lose the ability to walk within years after the onset of symptoms, and often need assistance with everyday tasks such as showering, dressing and transferring.

This study described a new approach that avoids the need for packaging a large gene, like dysferlin, or giving a large vector dose to target the muscles, which are bottlenecks faced in ongoing gene therapy efforts aimed at muscular dystrophies.

“Currently, patients with LGMD2B have no gene or drug-based therapies available to them, and we are amongst the few centers developing therapeutic approaches for this disease,” said Jyoti K. Jaiswal, M.Sc. Ph.D., senior investigator of the Center for Genetic Medicine Research at Children’s National. “We are working to further enhance the efficacy of this approach and perform a longer-term safety and efficacy study to enable the clinical translation of this therapy.”

The genetic defect in dysferlin that is associated with LGMD2B causes the encoded protein to be truncated or degraded. This hinders the muscle fiber’s ability to heal, which is required for healthy muscles. In recessive genetic disorders, like LGMD2B, common pre-clinical gene therapy approaches usually target the mutated gene in the muscle, making them capable of producing the missing proteins.

“The large size of the gene mutated in this disease, and impediments in body-wide delivery of gene therapy vectors to reach all the muscles, pose significant challenges for developing gene therapies to treat this disease,” said Jaiswal.

To overcome these challenges, the researchers found another way to slow down the disease’s progression. The authors built upon their previous discovery that acid sphingomyelinase (hASM) protein is required to repair injured muscle cells. In this current work, the research team administered a single in vivo dose of an Adeno-associated virus (AAV) vector that produces a secreted version of hASM in the liver, which then was delivered to the muscles via blood circulation at a level determined to be efficacious in repairing LGMD2B patient’s injured muscle cells.

“Increased muscle degeneration necessitates greater muscle regeneration, and we found that improved repair of dysferlin-deficient myofibers by hASM-AAV reduces the need for regeneration, causing a 2-fold decrease in the number of regenerated myofibers,” said Daniel Bittel, D.P.T., PhD., research postdoctoral fellow of the Center for Genetic Medicine Research at Children’s National and a lead author of this study.

Sreetama Sen Chandra, Ph.D., who was a research postdoctoral fellow at Children’s National at the time of this study and served as co-lead author, also added that “these findings are also of interest to patients with Niemann-Pick disease type A since the pre-clinical model for this disease also manifests poor sarcolemma repair.”

Children’s National researchers of the Center for Genetic Medicine Research and the Rare Disease Institute (RDI) are constantly pursuing high-impact opportunities in pediatric genomic and precision medicine. Both centers combine its strengths with public and private partners, including industry, universities, federal agencies, start-up companies and academic medical centers. They also serve as an international referral site for rare disorders.

Gene therapy Schematic

Gene therapy Schematic. Credit: Daniel Bittel.

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.