Decellularized scaffolds from skeletal muscle are suitable environment for myogenesis in vivo

Background. Skeletal muscle loss secondary to trauma or myopathy may require surgical interventions, i.e. muscle transplant or transposition. Our approach for skeletal muscle tissue engineering is based on a decellularized scaffold derived from a murine skeletal muscle of cadaveric origin. Our goal is the preparation of an implantable scaffold for applications in muscle repair surgical intervention. Methods. We decellularized the Tibialis Anterior (TA) muscle of cadaveric origin from murine hindlimbs. The decellularization process was achieved by incubation of dissected muscles in a detergent solution for different times accordingly to the muscle size. To assess biocompatibility, cell-loaded scaffolds were initially cultured in growth medium (i.e. containing high serum) followed by incubation in a differentiative medium (i.e. containing low serum), and cell viability was assessed by incorporation of the vital dye CMFDA. To replace homologous muscles, we transplanted decellularized scaffolds in vivo, by suturing them to the host tendon extremities following TA removal. The same protocol of transplantation was applied to implants derived from wild type mice in place of the homologous muscle in Nude mice (wt/Nude). With this approach the constructs were analyzed in regard to histocompatibility, bioactivity, degradability, toxicity in vivo at different times from transplantation. Results and discussion. The procedure to produce acellular scaffolds from cadaveric skeletal muscles preserves the extracellular matrix and its anatomical pattern. These scaffolds are suitable for myoblast cell culture in vitro and the cells are viable for several days. Both wt/wt mice and wt/Nude mice transplantation studies demonstrate that scaffolds are biodegradable in vivo in four weeks. Nonetheless, the transplanted acellular scaffold is readily colonized by both inflammatory and myogenic stem cells, as demonstrated by the expression of stem cell markers, followed by the formation of muscle fibers. The latter show centrally located nuclei and express muscle-specific myosin. Our studies represent the first molecular characterization of in vivo bioactivity of scaffolds derived from decellularized muscles and demonstrate that acellular scaffolds represent an innovative tool for the reconstruction of missing muscles.