1. Highly Porous Foam Scaffolds Imprinted With Human IPSCs Regenerate Skeletal Muscle And Improve Function Following Volumetric Muscle Loss

PURPOSE: Volumetric muscle loss (VML) is a composite loss of skeletal muscle tissue that heals with minimal muscle regeneration. Our present study evaluates a novel, highly porous, 3D-bioprinted scaffold containing human-induced pluripotent stem cell-derived myogenic precursor cells (hiPSC-MPCs) for VML treatment in a murine model. METHODS: To create VML injury, a 4 mm punch biopsy of the gastrocnemius muscle was created in 10-week-old, immunocompromised mice (Rag knockout). Mice were assigned into one of four groups: Sham, VML-only, VML+gelatin-methacryloyl (GelMA scaffold), or VML+hiPSC-MPCs (embedded in 3D scaffold). HiPSCs were derived by differentiating NCRM1 iPS cells for 20-30 days. The 3D scaffolds were implanted onto the wounded muscles and secured with photo-crosslinking. RESULTS: 4-week post-VML injury, fluorescent imaging of injured muscles demonstrated iPSCs within the scaffold and identified newly regenerated muscle tissue in the VML+hiPSC-MPCs group. This group also showed significant reduction in % fibrosis area on gross imaging compared to the acellular-GelMA group (p<0.0001) and VML-untreated group (p<0.05). 8-week post-injury, imaging demonstrated successful integration of hiPSC-MPCs into murine muscle. Functional strength assessment of the posterior compartment of the leg demonstrated an increase in in situ twitch and tetanic force in the hiPSC-MPCs-treated group compared to other groups (p<0.02). CONCLUSION: Our results demonstrate successful integration and de novo muscle formation upon in vivo implantation of hiPSC-MPC-derived muscle scaffold in a mouse gastrocnemius model of VML injury.