FIGURE 2.

AA treatment stimulates satellite cell activation and proliferation during muscle regeneration. The data are representative of those obtained in experiments on TA muscles from five mice. a, H&E-stained serial cross-sections from mouse TA muscle treated with different dosages of AA at post-injury day 3. b, cross-sectional areas of regenerated myofibers in PBS control (Con) and 30 mm AA-treated TA muscle 7 days after CTX injury were measured by Image-Pro Plus based on H&E staining of CTX-injured TA muscle sections. c, representative image of sections from TA muscles, injected CTX and treated with AA for 3 days, immunostained for Pax7 (red), MyoD (green), and nuclei (DAPI; blue). Right panel shows merged image with DAPI. d, quantification of Pax7⁺ and MyoD⁺ cells. The histogram represents the percentage of cells retaining Pax7⁺ and MyoD⁺ in each subpopulation (≥2000 cells/condition). e, representative image of Pax7 and MyoD staining and quantification of Pax7⁺/MyoD⁺ cells 1 day post-injury with or without 30 mm AA treatment (≥300 cells each). f, quantification of Pax7⁺ and MyoD⁺ cells in sections of 30 mm AA-injected TA muscles 2, 3, and 5 days (d) after muscle damage. g, representative images of MyoD (red) and BrdU (green) immunostaining 3 days post-injury showing the percentage of BrdU⁺ cells in the MyoD⁺ cell population (≥300 cells each). h, double staining for Pax7 and MyoD in expanded satellite cells from single fibers isolated from gastrocnemius muscle and cultured for 48 h. i, 1st panel shows the expression of Pax7 and MyoD in TA muscles damaged for 3 days treated with different dosages of AA. The other two panels show the expression level of Pax7, MyoD, and embryonic MHC (eMHC) protein levels in 30 mm AA-treated TA muscles 2, 3, and 5 days post-injury. GAPDH protein served as a loading control. Scale bar, 50 μm. More than five pairs of mice were used for each experiment. Data are presented as mean ± S.E. (error bars; *, p < 0.05; **, p < 0.01; ***, p < 0.001).