Neuromuscular Regeneration of Volumetric Muscle Loss Injury
Eszter Mihaly1, Neha Chellu1, Eileen Su1, Dallas E. Altamirano1, Shama R. Iyer2, Warren L. Grayson1 1Johns Hopkins University, Baltimore, MD, 2Marymount University, Arlington, VA
Skeletal muscle is well-adapted to regeneration, as muscle satellite cells differentiate upon injury and replace damaged tissue. However, volumetric muscle loss (VML) is a critical sized defect in which the healing mechanism is overwhelmed, and loss of normal structure and function persists. Transplantation of tissue engineered muscle scaffolds have been evaluated as a potential treatment. Here, we characterize a population of human primary myogenic cells (hPMCs) on an electrospun fibrin scaffold, and demonstrate that they align, fuse, and myogenically mature on the scaffold. We successfully enabled muscle regeneration using these cell seeded-scaffolds upon transplantation into a mouse model of VML injury. However, regeneration of the connection between nerves and muscle is also critical to achieving functional recovery, as long term denervation causes muscle atrophy. A promising avenue is the use of rehabilitative exercise to promote nerve regeneration via the induction of nerve growth factor secretion. We identified a gender-appropriate exercise regimen that improved AChR clustering and neural ingrowth into the injured muscle. In this study, we attempt to further promote neuromuscular regeneration by the use of agrin-treated scaffolds. Agrin is a proteoglycan endogenously secreted by motor nerve terminals to induce AChR clustering on the muscle cell surface and the formation of a functional neuromuscular junction. Various groups have suggested that the agrin-induced AChR clustering mechanism may be influenced by mechanical strain as mediated by YAP signaling, but this has not been well-evaluated. In this study, we evaluated the combinatorial effect of rehabilitative exercise and agrin-treated cell-seeded scaffolds on neuromuscular regeneration.
