Impact of prednisone on TGF-beta1 and collagen in diaphragm muscle from mdx mice.

The purpose of this study was to assess the impact of prednisone treatment for 8 weeks on the level of transforming growth factor-beta 1 (TGF-beta1), hydroxyproline (HYP) concentrations, and level of the mature, nonreducible collagen cross-link hydroxylysylpyridinoline (HP) in diaphragm muscle from 12-week-old mdx mice. Diaphragm muscle from untreated mdx mice had a significantly higher level of TGF-beta1, HYP, and HP cross-link compared with normal C57BL/10J (control) mice. Prednisone treatment significantly reduced the level of TGF-beta1 and HYP in diaphragm from mdx mice to values similar to control mice, but resulted in a higher level of the HP cross-link compared with untreated mdx mice. These findings indicate that short-term treatment of mdx mice with prednisone can attenuate the fibrotic response in diaphragm muscle, possibly by mediating the level of TGF-beta. Although prednisone was beneficial in preventing collagen accumulation, it resulted in a higher level of the HP cross-link, presumably by decreasing collagen turnover