Role of heme oxygenase-1 in differentiation of muscle satellite cells into mature myocytes

Muscle satellite cells are progenitor cells located beneath basal lamina of muscle fiber, which act as precursors for muscle repair. Upon muscle damage they may differentiate into myocytes, so they are considered as candidates for cell-based regenerative therapies. Our aim was to explore the role of heme oxygenase-1 (HO-1), a heme degrading enzyme which displays anti-inflammatory, antiapoptotic and antioxidant acivities, in differentiation of satellite cells

Experiments were performed using two models: i) immortalized myoblast cell line C2C12, stably transduced with retroviral vectors to overexpress HO-1 and ii) primary satellite cells isolated from hindlimb muscle of HO-1+/+, HO-1+/- and HO-1-/- mice. In both models the differentiation was induced by incubating the confluent cell cultures in the presence of 2% horse serum. We demonstrated that overexpression of HO-1 in C2C12 cells protected them against oxidative stress induced by the high concentrations of H2O2 or hemin, and upregulated production of stromal cell derived growth factor (SDF-1), whereas synthesis of major proinflammatory cytokines remained unaffected. Importantly, HO-1 overexpression inhibited differentiation of C2C12 line, as indicated by reduced fusion of cells into myotubes, decreased expression of myogenic regulatory factors (such as MyoD or myogenin), and attenuated activity of creatine phosphokinase. Results of first experiments performed on primary satellite cells, isolated from one month old mice and purified by pre-plate technique, seem to confirm that HO-1 expression may reduce maturation, whereas HO-1 deficiency may cause spontaneous differentiation of even non-confluent cells. Thus, HO-1 might be an important inhibitor of formation of mature myotubes from satellite cells.