Abstract 166: p66Shc Deletion Increases Tissue Regeneration After Ischemia
Background. Oxidative stress plays a pivotal role in ischemia and ischemia/reperfusion injury. p66Shc−/ − mice exhibit both lower oxidative stress and decreased tissue damage following hindlimb ischemia. Moreover, we found that H2O2 inhibits in vitro myogenic differentiation, suggesting that oxidative stress may regulate skeletal muscle regeneration. In this report, we investigated whether tissue regeneration that follows acute hindlimb ischemia was altered in p66Shc−/ − mice.
Methods and results. Hindlimb ischemia was induced by femoral artery dissection and the adductor muscles were examined 2–35 days after surgery. In keeping with lower tissue damage, histological analysis of p66Shc−/ − mice showed proportionately lower levels of regenerating myofibers. Interestingly, muscle regeneration started earlier (at 7 days, regenerating myofibers/mm2 ±SE: wt=37±13; −/ −=154±53, p<0.01) and was completed faster than in the wt control (at 21 days, regenerating myofibers/mm2 ±SE: wt=175.5±62.9; −/ −=31±17, p<0.02). Unlike ischemia, cardiotoxin injury induced similar skeletal muscle damage in p66Shc−/ − and wt mice. However, in keeping with the regenerative advantage observed after ischemia, p66Shc−/ − mice regenerated faster and, 7 days after cardiotoxin injection, regenerating area was 63%±23 larger than wt (p<0.02). It has been shown that the majority of skeletal muscle regeneration after damage is carried out by a resident population of myogenic stem cells called satellite cells (SC). Since no difference between p66Shc wt and −/ − mice was found in blood flow recovery after ischemia, SC were examined. Immunohisto-chemical analysis showed a similar SC number in wt and −/ − mice. However, in vitro cultured p66Shc−/ − SC displayed an higher proliferation rate (% of BrdU+ SC ±SE: wt=33±5; −/ −=45±3, p<0.02) and, afterwards, differentiated faster than the wt counterpart. Furthermore, when exposed to sublethal H2O2 doses, p66Shc−/ − SC were resistant to H2O2-induced inhibition of differentiation. Finally, myogenic conversion induced by MyoD overexpression was more efficient in p66Shc−/ − fibroblasts compared to wt.
Conclusions. The present work demonstrates that p66Shc plays a crucial role in the regenerative pathways activated by acute ischemia.