Duchenne muscular dystrophy (DMD) is a deadly genetic disease characterized by a lack of dystrophin expression, resulting in progressive weakening and wasting of skeletal and cardiac muscles. Currently, there is no cure for DMD. The approved hormonal treatments have side effects and delay the disease progression only transiently. The emerging gene correction strategies, although effective in mouse models, are likely to be of limited immediate value to patients due to issues associated with virus-mediated gene therapy. Therefore, new approaches to suppress the disease progression are needed. Myogenic muscle progenitor cells (MPCs), also known as satellite cells, become dysfunctional (reduced proliferation and differentiation capacities) as disease progresses, coincidentally with reduced muscle regeneration, aggravating fatty infiltration, and fibrotic tissue accumulation in skeletal muscle. Mesenchymal stromal cells (MSCs) are non-myogenic progenitors of fibroblasts and adipocytes. We and others have reported that MSCs get activated during the disease progression in DMD and turn into fibroadipogenic progenitors (FAPs) that proliferate, induce MPC dysfunction and contribute to muscle pathology. Our preliminary data indicates that FAPs express markers of adipocyte progenitors, also known as adipose stromal cells (ASCs), the MSCs derived from fat tissue, suggesting ASCs as a source of FAPs. The goal of this application is to test whether DMD pathogenesis can be delayed via depletion of MSC-derived FAPs in the mouse model.
In Aim 1, an inducible genetic ablation of proliferating MSC will be performed using a suicide transgene.
In Aim 2, pharmacological ablation will be performed with a hunter-killer peptide targeting ASCs. We will test if DMD progression, measured as MPC dysfunction, fatty infiltration, fibrotic tissue accumulation, and the resulting loss of skeletal muscle function, can be suppressed by these experimental treatments. We predict that ablation of FAPs derived from MSCs/ASCs from the dystrophic milieu will delay MPC depletion and DMD progression. Information obtained from these studies will help develop new therapeutic approaches for treating muscular dystrophy.
This proposal will investigate mesenchymal stromal cells (MSCs), the non-myogenic progenitor cells that form fibrotic lesions, promote fatty infiltration, and disable myogenic progenitors during Duchenne muscular dystrophy (DMD) progression. Through pharmacologic and genetic approaches in animal models, we will test whether ablation of disease-activated MSCs can have a beneficial effect. This information will be valuable for the development of therapies to delay the progression of muscular dystrophy.
