Growth factor supplemented Matrigel improves ectopic skeletal muscle formation - A cell therapy approach

Following damage to skeletal muscle, satellite cells become activated, migr ate towards the injured area, proliferate, and fuse with each other to form myotubes which finally mature into myofibers. We tested a new approach to muscle regeneration by incorporating myoblasts, with or without the exogeno us growth factors bFGF or HGF, into three-dimensional gels of reconstituted basement membrane (matrigel). In vitro, bFGF and HGF induced C2C12 myoblas t proliferation and migration and were synergistic when used together. In v ivo, C2C12 or primary i28 myoblasts were injected subcutaneously together w ith matrigel and growth factors in the flanks of nude mice. The inclusion o f either bFGF or HGF increased the vascularization of the gels. Gels supple mented with bFGF showed myogenesis accompanied by massive mesenchymal cell recruitment and poor organization of the fascicles. Samples containing HGF showed delayed differentiation with respect to controls or bFGF, with incre ased myoblast proliferation and a significantly higher numbers of cells in myotubes at later time points. HGF samples showed limited mesenchymal cell infiltration and relatively good organization of fascicles. The use of both bFGF and HGF together showed increased numbers of nuclei in myotubes, but with bFGF-mediated fibroblast recruitment dominating. These studies suggest that an appropriate combination of basement membrane components and growth factors could represent a possible approach to enhance survival dispersion , proliferation, and differentiation of myogenic cells during muscle regene ration and/or myoblast transplantation. This model wi Il help develop cell therapy of muscle diseases and open the future to gene therapy approaches. J. Cell. Physiol. 186:183-192, 2001. (C) 2001 Wiley-Liss, Inc.