Mineralized osteoblast-derived exosomes integrated on a polysaccharide-protein conjugated biomaterial promote bone regeneration by transferring the regulatory miRNAs

Exosomes derived from bone progenitor cells have the advantage of being cell-free non-immunogenic cargo delivery vehicles. In the present study, exosomes are isolated from MC3T3-E1 cells both before (GM-Exo) and after 14 days of mineralization (DM-Exo) and it was observed that DM-Exo, accelerate the process of differentiation in the recipient cells more prominently. The exosome small RNA sequencing revealed that miR-204-5p, miR-221-3p, and miR-148a-3p are among the highly upregulated miRNAs that target the function of Sox11, Timp3, and Ccna2 in the host cells, thereby enhancing the activity of osteoblastic genes. To enhance the bioavailability of the exosomes, they are encapsulated in a chitosan-collagen composite hydrogel that serves as a bioresorbable extracellular matrix (ECM). The exosome-laden scaffold (DM-Exo+Scaffold) enhances bone regeneration in critical sized calvarial bone defects within 8 weeks of implantation in rats. The shelf-life of the DM-Exo+Scaffold indicates that the bioactivity of exosomes in the polymer matrix is intact till 30 days. Integration of mineralized cell-derived exosomes on an ECM represents a bioresorbable matrix with a cell-free method for promoting new bone formation through the transfer of miRNA cargo, which can be further explored as personalized bone regeneration therapy.