Angiogenic gene-modified myoblasts promote vascularization during repair of skeletal muscle defects

Vascularization is thought to be a principle obstacle in the reconstruction of skeletal muscle defects. Long-term survival of reconstructed skeletal muscle is dependent on good vascularization. In this study, we upregulated angiogenic gene expression in myoblasts in an attempt to promote vascularization during repair of skeletal muscle defects. Skeletal myoblasts were isolated and expanded from newborn male Sprague-Dawley (SD) rats. The cells were transfected with human vascular endothelial growth factor 165 (VEGF-165) or human stromal cell-derived factor 1 (SDF-1), using Lipofectamine™ 2000 transfection reagent, prior to seeding onto calf collagen scaffolds. Gene and protein overexpression was verified by ELISA, RT-PCR and western blot analysis. Cell-seeded scaffolds were transplanted into back muscle defects in female SD rats. At weeks 2, 4 and 8 after transplantation, Y chromosome detection was used to observe the survival of growth factor-producing cells within the scaffolds in vivo. Capillary density was investigated using microvessel density detection, haematoxylin and eosin (H&E) staining and immunohistochemical staining. We found that vascularization was enhanced by transfected myoblasts compared with non-transfected myoblasts. In addition, VEGF-165 and SDF-1 had a synergistic effect on vascularization during repair of skeletal muscle defects in vivo. In conclusion, we have combined myoblast-seeded collagen sponge with gene therapy, resulting in a promising approach for the construction of well-vascularized skeletal muscle.