Fig. 4. Regulation of FAP fate by myotubes requires activation of ALK/Smad2 pathway and GLI1 expression in FAPs. (A) FAPs were cultured with MPs (Co-cult) for 10 days in differentiation medium with or without SB431542 that is a specific inhibitor of ALK4, ALK5, and ALK7. Expression of FABP4, PLIN1, COL1A1 and FN1 was measured by quantitative Q-PCR (n=3 donors). (B) FAPs were cultured with Ctrl CM or myotube CM for 1 hour, then total proteins were extracted. Expression levels of phosphorylated Smad2 (P-Smad2), total Smad2 and tubulin were assessed by western-blot. Representative immunoblot is shown (n=3 donors). (C) FAPs were cultured with MPs (Co-cult) for 10 days in differentiation medium with or without cyclopamine that is a specific inhibitor of GLI1 expression. Expression of FABP4, PLIN1, COL1A1 and FN1 was measured by quantitative Q-PCR (n=3 donors). (D) FAPs were cultured with Ctrl CM or myotube CM for 10 days in differentiation medium. Expression of GLI1 was measured by quantitative Q-PCR (n=3 donors). *** P<0.001; ** P<0.01; * P<0.05; p values close to significance are indicated.