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sketch of muscle cells

Losing muscle to fat: misdirected fate of a multipotent stem cell drives LGMD2B

Fibro/adipogenic precursors (FAPs) control the onset and severity of disease in limb-girdle muscular dystrophy type 2 (LGMD2B)

Fibro/adipogenic precursors (FAPs) control the onset and severity of disease in limb-girdle muscular dystrophy type 2 (LGMD2B). a) Healthy and/or pre-symptomatic LGMD2B muscle contains resident FAPs. b) After myofiber injury, inflammatory cells invade and trigger FAP proliferation. c) In symptomatic LGMD2B muscle, there is a gradual accumulation of extracellular AnxA2, which prolongs the pro-inflammatory environment, causing excessive FAP proliferation. d) Blocking aberrant signaling due to AnxA2 buildup blocks FAP accumulation and thus preventing adipogenic loss of dysferlinopathic muscle. Credit: “Fibroadipogenic progenitors are responsible for muscle loss in limb girdle muscular dystrophy 2B.” Published online June 3, 2019, in Nature Communications. Marshall W. Hogarth, Aurelia Defour, Christopher Lazarski, Eduard Gallardo, Jordi Diaz Manera, Terence A. Partridge, Kanneboyina Nagaraju and Jyoti K. Jaiswal. https://rdcu.be/bFu9U.

Research led by faculty at Children’s National published online June 3, 2019, in Nature Communications shows that the sudden appearance of symptoms in limb-girdle muscular dystrophy type 2 (LGMD2B) is a result of impaired communication between different cell types that facilitate repair in healthy muscle. Of particular interest are the fibro/adipogenic precursors (FAPs), cells that typically play a helpful role in regenerating muscle after injury by removing debris and enhancing the fusion of muscle cells into new myofibers.

LGMD2B is caused by mutations in the DYSF gene that impair the function of dysferlin, a protein essential for repairing injured muscle fibers. Symptoms, like difficulty climbing or running, do not appear in patients until young adulthood. This late onset has long puzzled researchers, as the cellular consequences of dysferlin’s absence are present from birth and continue through development, but do not impact patients until later in life.

The study found that in the absence of dysferlin, muscle gradually increases the expression of the protein Annexin A2 which, like dysferlin, facilitates repair of injured muscle fiber. However, increasing Annexin A2 accumulates outside the muscle fiber and drives an increase in FAPs within the muscle as well as encourages these FAPs to differentiate into adipocytes, forming fatty deposits. Shutting down Annexin A2 or blocking the adipocyte fate of FAPs using an off-the-shelf medicine arrests the fatty replacement of dysferlinopathic muscle.

“We propose a feed-forward loop in which repeated myofiber injury triggers chronic inflammation which, over time, creates an environment that promotes FAPs to accumulate and differentiate into fat. This, in turn, contributes to more myofiber damage,” says Jyoti K. Jaiswal, MSc, Ph.D., a principal investigator in the Center for Genetic Medicine Research at Children’s National and the study’s senior author.

“Adipogenic accumulation becomes the nucleating event that results in an abrupt decline in muscle function in patients. This new view of LGMD2B disease opens previously unrealized avenues to intervene,” adds Marshall Hogarth, Ph.D., the study’s lead author.

Joyti Jaiswal

“We propose a feed-forward loop in which repeated myofiber injury triggers chronic inflammation which, over time, creates an environment that promotes FAPs to accumulate and differentiate into fat. This, in turn, contributes to more myofiber damage,” says Jyoti K. Jaiswal, MSc, Ph.D.

A research team led by Jaiswal collaborated with Eduard Gallardo and Jordi Diaz Manera, of Hospital de la Santa Creu in Barcelona, Spain, to examine muscle biopsies from people with LGMD2B who had mild to severe symptoms. They found that adipogenic deposits originate in the extracellular matrix space between muscle fibers, with the degree of accumulation tied to disease severity. They found a similar progressive increase in lipid accumulation between myofibers predicted disease severity in dysferlin-deficient experimental models. What’s more, this process can be accelerated by muscle injury, triggering increased adipogenic replacement in areas that otherwise would be occupied by muscle cells.

“Accumulation and adipogenic differentiation of FAPs is responsible for the decline in function for dysferlinopathic muscle. Reversing this could provide a therapy for LGMD2B, a devastating disease with no effective treatment,” predicts Jaiswal as the team continues research in this field.

Promising off-the-shelf drugs include batimastat, an anti-cancer drug that inhibits the extracellular matrix enzyme matrix metalloproteinase. This drug reduces FAP adipogenesis in vitro and lessens injury-triggered lipid formation in vivo. In experimental models, batimastat also increases muscle function.

In addition to Jaiswal, Hogarth, Gallardo and Diaz Manera, other study co-authors include Aurelia Defour, Christopher Lazarski, Terence A. Partridge and Kanneboyina Nagaraju, all of Children’s National.

Financial support for research described in this post was provided by the Muscular Dystrophy Association under awards MDA477331 and MDA277389, the National Institute of Arthritis and Musculoskeletal and Skin Diseases under award R01AR055686 and the National Institutes of Health under awards K26OD011171, R24HD050846 and P50AR060836.

Pediatric Neurology Update Attendees

Pediatric neurologists get a primer on the state of ASD research and care

Pediatric Neurology Update Attendees

Neurologists who attended the 2019 Pediatric Neurology Update received a broad look at autism spectrum disorders, ranging from biology to clinical care and advocacy.

Autism spectrum disorders (ASD) took center stage for the afternoon sessions of the annual Pediatric Neurology Update in April. The meeting, hosted by the Center for Neuroscience and Behavioral Medicine at Children’s National Health System, brings together 150-plus pediatric neurologists each year to discuss critical research and clinical care of pediatric neurological conditions.

Led by the Center for Autism Spectrum Disorders Director Lauren Kenworthy, Ph.D., the afternoon’s slate of presentations sought to give broad perspective of the current state of ASD research and treatment best practices.

“We know that the brain is different in autism, but many times we continue to define autism by behavioral traits,” Dr. Kenworthy told the crowd in her introduction. “Sitting between the brain and behavior often is cognition – how do you understand your world and interpret it?”

The afternoon’s presentations were organized to provide the audience with a clear picture of many facets of ASD research and treatment. Highlights included:

  • Joshua Corbin, Ph.D., director of the Center for Neuroscience Research, offered “New Insights into the Neurobiologic Underpinnings of Autism,” which mapped out some of the biological mechanisms of autism.
  • Adelaide Robb, M.D., and Dr. Kenworthy presented current clinical care outlines, with Dr. Robb focusing on pharmacological therapies and Dr. Kenworthy sharing successful strategies to improve executive functioning and day to day task management for school-aged children.

Attendees also received a taste of two current “hot topics” in autism research and care:

  • Kevin Pelphrey, Ph.D., presented recent findings on “Gender Differences in Autism Spectrum Disorders: Girls with Autism” calling attention to the fact that the current diagnostic standards may not capture some female-associated phenotypes of ASD.
  • Julia Bascom of the Autistic Self Advocacy Network brought the autistic person’s point of view to the table via her presentation: “Autism: Society and Government Challenges and Solutions,” which focused on her organization’s efforts to improve inclusivity in advocacy and research, which she sums up as, “Nothing about us without us.”

The session concluded with a real-world focused “Autism-Friendly Hospital Roundtable,” of six panelists from the clinical, advocacy, community and technology fields, who are all involved in hands-on practices to improve medical experiences for autistic children and adults.

  • CASD’s Yetta Myrick talked about her work to engage families of autistic children in discussions of research and clinical care programs, including the start of CASD’s first-ever Stakeholder Advisory Board.
  • Julia Bascom talked about some of the less-often discussed challenges for many autistic people who seek medical services.
  • Kathleen Atmore, Psy.D., and Eileen Walters, MSN, RN, CPN, provided an overview of Beyond the Spectrum, the clinical service at Children’s National that coaches providers and families in techniques to reduce the stress of routine medical visits for patients with autism and other developmental disabilities.
  • Amy Kratchman, director of the LEND Family Collaboration at Children’s Hospital of Philadelphia, talked about some of the autism-friendly strategies underway at her institution.
  • Michael O’Neil, JD, MBA, founder and CEO of the GetWell Network, Inc., previewed how GetWell and Children’s National are partnering on a new tool that harnesses app technology to bring better information to autistic children and their families after a new autism diagnosis.
  • Vijay Ravindran, CEO and co-founder at Floreo, demonstrated how it might be possible to reduce stress and create a calm peaceful autism-friendly environment even in the busiest of waiting rooms, by allowing the patient to escape via virtual reality.

The roundtable showcased how Children’s National and other health care institutions are using evidence-based strategies to improve medical care experiences for autistic people and their families. Ideally any provider, including pediatric neurologists, who cares for people from the autism community, can incorporate any or all of these strategies as a way to meet the unique needs of this patient population.

The content was so timely and relevant to the audience that many attendees stayed past the official end of the meeting to continue discussing best practices with the panelists and each other.