Figure 2.

Ablation of Pax7⁺ MPCs in mice results in a complete lack of a muscle regenerative response 1 week after HLI. (A) Muscle regeneration was examined by staining for embryonic myosin heavy chain (eMHC, red) and endothelial cells (CD31, green), top, and for centralized myonuclei by H&E, bottom. (B–D) Quantification of centralized myonuclei (B) and eMHC (C) demonstrates a complete lack of regenerative response to ischemia. Quantification of CD31 area (D) demonstrates an increase in endothelial area relative to muscle area in Pax7^Δ mice (n = 3–4 per group). (E,F) 1 week after HLI surgery, there was a significant increase in the number of Pax7⁺ cells per high power field in the ischemic TA of Pax7^WT mice but not in muscle of Pax7^Δ mice. Compared to resting muscle, there was a 10-15-fold increase in the number of Pax7⁺ cells in injured Pax7^WT muscle, consistent with activation of satellite cells following injury (n = 3 per group). Scale bar = 100 μm. All data shown are means +/− SEM. **p < 0.01; ***p < 0.001, by 2-sided t-test.