Intramuscular Delivery of BMP-2 and Increasing Doses of LECT-1 Using Keratin-PEG Gels for Ectopic Tissue Differentiation

Abstract

Producing bone and cartilage in a controlled and localized manner remains a significant challenge in regenerative medicine. This study investigated the ability of keratin- and polyethylene glycol (PEG)-based degradable hydrogels to deliver bone morphogenetic protein 2 (BMP-2) and leukocyte cell-derived chemotaxin 1 (LECT-1; also known as chondromodulin-1) intramuscularly to induce ectopic tissue formation. Adult male CD-1 mice received intramuscular implants of keratin-PEG gels containing a fixed dose of BMP-2 and increasing amounts of LECT-1. After two weeks, implants and surrounding muscle were analyzed using computed tomography (CT) and histology. The results showed that BMP-2 is necessary for forming new bone and cartilage, whereas LECT-1 alone appeared to trigger muscle dedifferentiation without ossification or chondrogenesis. Co-delivery of BMP-2 and LECT-1 enhanced bone and cartilage formation in a dose-dependent manner: higher LECT-1 doses led to proportionally more ectopic cartilage (linear correlation, r2 {approx} 90%), while bone formation peaked at the third LECT-1 dose at approximately twice the volume of the BMP-2-only group. These findings indicate that muscle-resident cells may be capable of reverting and switching to mesenchymal lineages, recapitulating endochondral ossification. The platform offers a promising strategy for growing bone and cartilage autografts within skeletal muscle bundles. Impact StatementThis study presents a novel strategy for inducing ectopic bone and cartilage formation by delivering BMP-2 and LECT-1 from keratin-PEG hydrogels into skeletal muscle. The findings suggest that muscle-resident cells can dedifferentiate and transdifferentiate into mesenchymal lineages, enabling controlled ectopic tissue regeneration. This approach may inform future tissue engineering therapies in which autografts are harvested from within the body, using skeletal muscle as an in vivo tissue incubator.