Use of uniformly sized muscle fiber fragments for restoration of muscle tissue function

Treatment of extensive muscle loss due to traumatic injury, congenital defects, or tumor ablations is clinically challenging. The current treatment standard is grafting of autologous muscle flaps; however, significant donor site morbidity and graft tissue availability remain a problem. Alternatively, muscle fiber therapy has been attempted to treat muscle injury by transplanting single fibers into the defect site. However, irregularly organized long fibers resulted in low survivability due to delay in vascular and neural integration, thus limiting the therapeutic efficacy. Therefore, no effective method is available to permanently restore extensive muscle injuries. To address the current limitations, we developed a novel method that produces uniformly sized native muscle fiber fragments (MFFs) for muscle transplantation. We hypothesized that fragmentation of muscle fibers into small and uniformly sized fragments would allow for rapid reassembly and efficient engraftment within the defect site, resulting in accelerated recovery of muscle function. Our results demonstrate that the processed MFFs have a dimension of approximately 100 μm and contain living muscle cells on extracellular matrices. In preclinical animal studies using volumetric defect and urinary incontinence models, histological and functional analyses confirmed that the transplanted MFFs into the injury sites were able to effectively integrate with host muscle tissue, vascular, and neural systems, which resulted in significant improvement of muscle function and mass. These results indicate that the MFF technology platform is a promising therapeutic option for the restoration of muscle function and can be applied to various muscle defect and injury cases.