Fig. 1. Acvr1^R206H/+ skeletal muscle tissue does not repair properly after injury.

a Prior to injury, fibers from skeletal muscle tissue from Acvr1^R206H/+ mice are slightly smaller compared to control tissue. b–e Control and Acvr1^R206H/+ mice were subjected to Tibialis Anterior (TA) injury with CTX. Representative images of H&E staining of skeletal muscle sections at timepoints after injury. b At 5 DPI, control muscle shows fibers with centralized nuclei, a sign of repairing fibers. Acvr1^R206H/+ muscle appears fibrotic with fewer repairing fibers. c At 10 DPI, control muscle has continued to repair, while Acvr1^R206H/+ muscle tissue appears more fibrotic and muscle damage persists. d, e At 21 DPI, control muscle had fully repaired, while ectopic bone with adjacent regions of mature cartilage (as shown by Alcian blue hematoxylin/orange G stain) was present in Acvr1^R206H/+ muscle. Scale bar = 200 µm for a–c images; 500 µm for d images; 100 µm for e image; 20 µm for all inset images. f Representative µCT image of HO in Tibialis Anterior (TA) muscle (circled in yellow). Scale bar = 5 mm. g Quantification of fiber size (normalized cross-sectional area; CSA) of regenerating fibers (µm²) during regeneration (timepoints are indicated on graphs). n = 3–5 mice for each timepoint. Statistical significance was determined by student’s t-test; *p < 0.05.