We have recently made progress in using 3D cell culture techniques to engineer functional skeletal muscle tissues from human pluripotent stem cells. We will further optimize this technology and apply it to generate contractile muscle tissues using induced pluripotent stem cells (iPSCs) from three LGMD2B patients and two healthy human donors. The resulting iPSC-derived dysferlin-deficient human muscle tissues will be systematically characterized by various structural, functional, and molecular assays.
Our research is focuses on the role of dysferlin in resealing of the skeletal muscle sarcolemmal membrane after that membrane is disrupted.
The rationale behind this proposal is based on the evidence that a key pathogenic feature of dysferlinopathies is the muscle infiltration by fat. Although the origin of this pathogenic event has not been established, the detection of adipogenic progenitors – FAPs – in muscles of the mouse model of dysferinopathies (A/J mice) and patients suggests that these cells can be implicated in the pathogenesis of the disease.
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Macrophages (Mø) are prominent in the inflamed skeletal muscles of patients with dysferlinopathy. Mø are integral to both tissue repair and destruction. Injured skeletal muscle recruits inflammatory, cyto-destructive Mø that transition over time into reparative/regulatory Mø to regenerate and heal. As muscles in patients with dysferlinopathy do not heal, cyto-destructive Mø are likely central to non-resolving inflammation resulting in the loss of muscle fibers. IL-34 and CSF-1 are the principle cytokines that promote Mø survival and proliferation.
Autosomal recessive mutations in the human gene encoding the dysferlin protein (DYSF) are the cause of rare forms of muscular dystrophies known as dysferlinopathies, and more specifically, as limb girdle muscular dystrophy type 2B (LGMD2B) or Miyoshi myopathy (MM). Dysferlin is a 237 kDa type II transmembrane skeletal muscle protein associated with the sarcolemma, where its function appears to be required for efficient muscle contraction and muscle membrane repair.