Deconstruction of cellular dynamics after treatment of volumetric muscle loss injury with extracellular matrix

Volumetric muscle loss (VML) is an acute loss of a critical volume of skeletal muscle that results in inflammation, fibrotic scarring in muscle tissue, and permanent muscle defects. The cellular and molecular processes that underlie fibrosis induced from VML injury need to be evaluated in larger animal models. Therefore, we used a canine model of VML alongisde treatment with an extracellular matrix (ECM) hydrogel. Treatment with the ECM hydrogel improved muscle regenerative responses and decreased proportions and spatial signatures of fibrotic and inflammatory cell populations. Overall design: For single-nuclear RNA sequencing, samples were collected from biopsy samples of untreated canine skeletal muscle tissues at 0, 7, and 14 days post volumetric muscle loss (VML) injury. Canine tissues from animals at 0, 7, and 14 days post VML were collected for spatial gene expression profiling. Samples wereflash-frozen, OCT embedded, muscle tissue. Canine tissues were collected in different wound locations (mid or edge) in treated samples. There were a total of 4 replicates for untreated samples, 3 untreated samples at 7 days post injury, 3 untreated samples at 14 days post injury, and 4 ECM-treated samples at 14 days post injury.