Engineering a cell-free bone regeneration platform using osteogenically primed MSC-EVs and nHAp-enriched IPN hydrogels.

AIMS: This study aimed to enhance the osteoinductive potential of mesenchymal stem cell-derived extracellular vesicles (MSC-EVs) by integrating them into a nano-hydroxyapatite (nHAp)-enriched hydrogel scaffold for bone regeneration applications.

MATERIALS &

METHODS

EVs were isolated from naïve and osteogenically primed MSCs and characterized for morphology, cargo content, and cytocompatibility. Their uptake and osteoinductive activity were assessed in vitro using MC3T3 cells within a 3D interpenetrating network (IPN) hydrogel. The most effective EV formulation was incorporated into an nHAp - IPN hydrogel scaffold and evaluated both in vitro and in a murine subcutaneous implantation model.

RESULTS

Primed MSC-EVs showed elevated calcium, ALP activity, and osteogenic/angiogenic mRNAs (Runx2, Vegf-a) compared to naïve EVs, with comparable size and morphology. Both EV types were internalized efficiently without cytotoxicity. In combination with nHAp, primed EVs enhanced ALP activity, calcium deposition, and in vivo mineralization. Histological analysis confirmed scaffold biocompatibility and mineralized tissue formation.

CONCLUSIONS

Osteogenically primed MSC-EVs significantly improved the osteoinductive performance of nHAp-based hydrogels, supporting their potential as a cell-free therapeutic strategy for bone tissue engineering.