Association of myostatin deficiency with collagen related disease-umbilical hernia and tippy toe standing in pigs.

Herein, we investigate the high incidence of umbilical hernia and tippy-toe standing and their underlying changes in gene expression and proliferation in myostatin knockout (MSTN-/-) pigs. Thirty-six male MSTN-/- pigs were generated by somatic cell nuclear transfer (SCNT). These pigs presented a considerably high incidence of tippy-toe standing and umbilical hernia (69.4% and 61.1%, respectively). The tendon to body weight ratio was significantly lower than wild-type pigs (0.202 ± 0.017 vs 0.250 ± 0.004, respectively). The crimp length of the MSTN-/- tendon was significantly longer than that of wild-type pigs. The expression of MSTN and the activin type IIB (ACVR2B) was detected in the tendon and linea alba of MSTN-/- pigs. MSTN treatment significantly increased the phosphorylation of Smad2/3 in both tendon and linea alba fibroblasts. Type I collagen (Col1A) and Scleraxis (Scx) expression levels in the tendon and linea alba of MSTN-/- pigs were significantly lower than those in wild-type in vivo, whereas and cyclin-dependent kinase inhibitor 1 (p21) expression levels were higher. Treatment of tendon and linea alba fibroblasts with recombinant MSTN increased Col1A and Scx and decreased p21 expression in vivo. Moreover, there was a significant increase in fibroblast proliferation after treatment. The results indicated that MSTN regulates collagen expression and proliferation in tendon and linea alba fibroblasts; thus, MSTN deficiency causes collagen-related pathological features in MSTN-/- pigs. Hence, MSTN could be used as a therapeutic target for treating UH and tendon abnormalities.