Priming enhances avian mesenchymal stem cell-derived small extracellular vesicles for post-surgical alveolar bone repair

Background Mesenchymal stem cell-derived small extracellular vesicles (MSC-sEVs) are emerging as cell-free mediators of tissue repair, but their regenerative activity is influenced by parental cell source and conditioning status. This study evaluated whether priming enhances the bone-repair activity of avian MSC-derived sEVs (AMSC-sEVs) in experimental alveolar defect models. Methods Naïve and primed AMSC-sEVs were characterized by tunable resistive pulse sensing, bead-based flow cytometry, small RNA sequencing, and quantitative reverse-transcription PCR. Their local bone-repair activity was examined in rat surgically created periodontal defects and extraction socket defects. Defects received Matrigel alone, naïve AMSC-sEVs, low-dose primed AMSC-sEVs, or high-dose primed AMSC-sEVs. Bone repair was assessed by micro-computed tomography, histology, and histomorphometric quantification of new bone formation. Results Primed AMSC-sEVs showed a smaller mean particle diameter, higher recoverable particle concentration, and enrichment of miRNA cargo associated with osteogenesis, angiogenesis, and bone remodeling. In both alveolar defect models, primed AMSC-sEVs improved mineralized tissue fill and trabecular microarchitecture, with increased bone volume fraction and trabecular thickness and reduced trabecular separation. Histological and histomorphometric analyses confirmed greater new bone formation, with the strongest response observed in the high-dose primed AMSC-sEV group. Conclusions Priming improved the regenerative performance of AMSC-sEVs in experimental alveolar bone repair. These findings support primed AMSC-sEVs as a modifiable cell-free vesicle platform for bone repair and provide a preclinical basis for further development of primed MSC-sEV products in regenerative medicine.