Extracellular matrix particle treatment induces digit regeneration in soft-tissue preserved amputation (SPA) model of adult mice

Background In mouse classic amputation model, second phalanx (P2) is incapable of regeneration. Extracellular matrix (ECM) solution has shown limited ability to induce digit regeneration in classical amputation model of the murine digit. However, the effect of solid ECM particles on bone regeneration is not well understood due to difficulties in treating solid particles in classical amputation model. Methods We examined the regenerative effects of ECM particles in mice digit by establishing a soft tissue preserved amputation (SPA) model on P2, through removing the amputated bone whilst preserving soft tissue. ECM particles implanted into the amputation site and wrapped in the preserved soft tissues. Bone regeneration was assessed by morphological examination and micro-CT scans. Results We observed bone regeneration in the SPA model; specifically, new bone formed at the P2 distal end. Implantation of ECM particles exerted a pro-regenerative effect, characterized by increased bone volume and decreased bone density. Moreover, the ECM induced the formation of free-floating bone, further supporting its role in bone regeneration. Combined treatment with ECM particles and bone morphogenetic protein 2 (BMP2) resulted in a significant increase in bone volume. Conclusions We demonstrate that soft tissue preservation at the amputation site can overcome the intrinsic regenerative limitationsl. Using SPA model, we found that ECM particles have a proven ability to promote bone regeneration, and that the combination of ECM particles with BMP2 further enhances bone regeneration. These findings underscore the therapeutic promise of ECM-based strategies, for clinical translation in non-regenerative finger injuries.