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Myogenic precursor cell (MPC) transplantation is a good strategy to introduce dystrophin expression in muscles of Duchenne muscular dystrophy (DMD) patients. Insulin-like growth factor (IGF-1) promotes MPC activities, such as survival, proliferation, migration and differentiation, which could enhance the success of their transplantation. Alternative splicing of the IGF-1 mRNA produces different muscle isoforms. The mechano growth factor (MGF) is an isoform, especially expressed after a mechanical stress. A 24 amino acids peptide corresponding to the C-terminal part of the MGF E domain (MGF-Ct24E peptide) was synthesized. This peptide had been shown to enhance the proliferation and delay the terminal differentiation of C 2 C 12 myoblasts. The present study showed that the MGFCt24E peptide improved human MPC transplantation by modulating their proliferation and differentiation. Indeed, intramuscular or systemic delivery of this synthetic peptide significantly promoted engraftment of human MPCs in mice. In vitro experiments demonstrated that the MGF-Ct24E peptide enhanced MPC proliferation by a different mechanism than the binding to the IGF-1 receptor. Moreover, MGF-Ct24E peptide delayed human MPC differentiation while having no outcome on survival. Those combined effects are probably responsible for the enhanced transplantation success. Thus, the MGF-Ct24E peptide is an interesting agent to increase MPC transplantation success in DMD patients.

These results suggest that IGF-1 or bFGF coinjection with human myoblasts increased their proteolytic activities and consequently their migratory capacity. This study may help to develop approaches that will reduce the number of injection sites for the treatment of Duchenne muscular dystrophy patients.