Fig. 2: Morphological manifestations of skeletal muscle contusion in wild-type mice and PD-1^−/− mice.

(a) HE staining results. (b) Comparison of regenerated muscle fiber diameter at 14 days after injury. Data are mean ± SD, n (WT) = 3, n (PD-1^−/−) = 3. *Compared with WT14, P < 0.05.