An in vitro culture system that supports robust expansion and maintenance of in vivo engraftment capabilities for myogenic progenitor cells from adult mice.

Muscle cell therapy and tissue engineering require large numbers of functional muscle precursor/progenitor cells (MPCs), making the in vitro expansion of MPCs a critical step for these applications. The cells must maintain their myogenic properties upon robust expansion, especially for cellular therapy applications, in order to achieve efficacious treatment. A major obstacle associated with MPCs expansion is the loss of "stemness," or regenerative capacity, of freshly isolated cells, presumably due to the absence of the native cellular niches. In the current study, we developed an in vitro system that allowed for long-term culture and massive expansion of murine MPCs (mMPCs) with the preservation of myogenic regeneration capabilities. Long term in vitro expanded mMPC expressed the myogenic stem cell markers Pax3 and Pax7 and formed spontaneously contracting myotubes. Furthermore, expanded mMPC injected into the tibialis anterior muscle of nude mice engrafted and formed myofibers. Collectively, the method developed in this study can be potentially adapted for the expansion of human MPCs to high enough numbers for treatment of muscle injuries in human patients.