Hydrogel-integrated exosome mimetics derived from osteogenically induced mesenchymal stem cells in spheroid culture enhance bone regeneration.

Exosomes derived from mesenchymal stem cells (MSCs) offer a promising alternative to traditional cell-based therapies for tissue repair by mitigating risks associated with the transplantation of living cells. However, insufficient osteogenic capacity of exosomes diminishes their potential in bone tissue regeneration. Here, we report novel osteogenically induced exosome mimetics (EMs) integrated into injectable hydrogel carriers for improved bone regeneration. EMs were produced by a serial extrusion of MSCs cultured as spheroids during osteogenic induction. The prepared EMs were chemically anchored on a self-healing hydrogel assembled by guanidinylated hyaluronic acid and silica-rich nanoclays for sustained release of EMs. The administration of hydrogel-integrated EMs into mouse calvarial defects resulted in robust bone tissue regeneration. miRNA sequencing revealed altered expression of specific miRNAs in the EMs related to Wnt/β-catenin and Notch signaling pathways. Our study provides new insights into the development of advanced exosome-based cell-free therapies for bone tissue engineering.