Figure 4.

Levels of SMAD4 and miR-431 during regeneration of injured muscles. (A) SMAD4 expression patterns were determined using Western blot analysis in CTX-injured young and old TA muscle tissues for up to 14 d post-injury (DPI). (Top) GAPDH was included as a loading control. RT-qPCR analysis of miR-431 in CTX-injured young and old TA muscle tissues for up to 14 d. (Bottom) Expression levels were measured in triplicate, and the data were normalized to the amount of U6 snoRNA and expressed relative to the normalized value for young TA muscle tissues at day 0. (B) At day 14 after CTX injury, young and old TA muscle tissue sections were stained with antibodies that recognized PAX7 (green) and SMAD4 (red), revealing the colocalization of both antigens in myoblasts localized in old muscle tissues. Bar, 20 µm. (White dotted lines) Muscle fibers. (***) P < 0.001.