Injectable conductive micro-cryogel as a muscle stem cell carrier improves myogenic proliferation, differentiation and in situ skeletal muscle regeneration

Volumetric muscle loss (VML) results in the impediment of skeletal muscle function, and there were still great challenges in cell delivery approach with the minimally invasive operation to repair muscle defects. To deliver cells to the VML defects site efficiently, the injectable conductive porous nanocomposite microcryogels based on gelatin (GT) and reduced graphene oxide (rGO) were designed and prepared. The microcryogels were loaded with myoblasts to form an injectable cell delivery system and show the ability to protect cells during injection. Conductive microcryogel with 4 mg/mL rGO (GT/rGO4) enhanced C2C12 cell proliferation and myogenic differentiation during 3D culture compared with pure gelatin microcryogel. In a mice VML model, injection of microcryogel loaded with muscle-derived stem cells into the injury site significantly improved the generation of new muscle fibers and blood vessels, and anti-inflammatory properties. The results show that injectable biodegradable conductive microcryogel can be used as muscle stem cell carriers with the potential to maintain cell activity and deliver cells to defective sites, thereby in situ enhancing skeletal muscle regeneration. STATEMENT OF SIGNIFICANCE: Volumetric muscle loss overwhelms the regenerative capacity of skeletal muscle, which results in severe damage to muscle tissues. In the treatment of volumetric muscle loss, conductive niche and muscle stem cells are needed to alleviate excessive scar formation and inflammation to improve muscle regeneration. Injectable gelatin/reduced graphene oxide based nanocomposite microcryogel can enhance the differentiation of seeded muscle stem cells. The improved repair of volumetric muscle loss was achieved via reducing collagen deposition and inflammation in the injected region through the microcryogel cell-delivery therapy, suggesting great potential of the injectable microcryogel as a cell carrier in soft tissue repair.