Spatiotemporal mapping of immune and stem cell dysregulation after volumetric muscle loss

Volumetric muscle loss (VML) is an acute trauma that results in persistent inflammation, supplantation of muscle tissue with fibrotic scarring, and decreased muscle function. The cell types, nature of cellular communication, and tissue locations that drive the aberrant VML response have remained elusive. Herein, we used spatial transcriptomics on mouse and canine models of VML and observed VML engenders a unique spatial pro-fibrotic pattern driven by crosstalk between fibrotic and inflammatory macrophages and mesenchymal derived cells. The dysregulated response was conserved between murine and canine VML models, albeit with varying kinetics, and impinged on muscle stem cell mediated repair. Targeting this circuit in a murine model resulted in increased regeneration and reductions in inflammation and fibrosis. Collectively, these results enhance our understanding of the cellular crosstalk that drives aberrant regeneration and provides further insight into possible avenues for fibrotic therapy exploration. Spatial gene expression profiling was performed on flash-frozen, OCT embedded muscle tissue from mouse and canine post VML injury. Canine tissues were collected from two animals in different wound locations for a total of three spatial samples. Four replicates were generated for each treatment in mice (vehicle and ITD1) at 7 days post injury, and two replicates were generated for 14 days post injury.