[Effect of prednisolone on apoptosis and cellular infiltration in mdx mouse muscle]

Myonuclear apoptosis might precede the muscular degeneration of Duchenne muscular dystrophy. We examined influence of prednisolone (PSL) on apoptosis in the skeletal muscle of mdx mouse. Amount of apoptotic nuclei of the tibial anterior or quadriceps muscle was assessed by Tdt-mediated dUTP biotin nick end-labeling (TUNEL) method. When nuclei were classed into myonuclei and interstitial ones, apoptotic nuclei were observed mainly in the latter. In comparison between 7 and 33 week-old mice, interstitial apoptosis increased with age in both control and PSL group. Treatment with PSL decreased number of interstitial apoptotic nuclei. To the contrary, apoptotic myonuclei were increased with PSL treatment. Treatment with PSL significantly reduced focal accumulation of infiltrating mononuclear cells, possibly contributing to the suppression of muscle degeneration. Relationship between decrease of interstitial apoptosis and reduced cellular infiltration was unclear yet. Present study showed that PSL differently affected apoptosis between muscle cells and their interstitium.