Objective To evaluate the synergistic effects of gelatin methacryloyl (GelMA) hydrogel combined with bone marrow mesenchymal stem cells (BMSC)-derived exosomes (EXO) on the repair of rat calvarial defect.

Methods GelMA hydrogel was prepared, and its microstructure was observed by electron microscopy, and the compressive strength of the hydrogel samples was calculated by an electronic universal testing machine. BMSC-derived exosomes were extracted. Western blotting and electron microscopy were used for verification. Live/dead cell staining was used to examine the effects of GelMA on the survival rate of BMSCs. The calvarial defect models were divided into the NC group, GelMA group and GelMA+EXO group, with 3 animals in each group and observation for 8 weeks. Micro-CT, three-dimensional reconstruction and HE staining were used to confirm the bone defect conditions in each group.

Results GelMA had excellent mechanical properties, capable of withstanding a pressure of 148 kPa and deformation rate of 92%. The EXO extracted from the supernatant of BMSC were observed by transmission electron microscopy to present a typical cup-shaped morphology. Nanoparticle tracking analysis showed that its average particle size was 140 nm. Western blotting detection confirmed the high expression of exosome markers CD63, CD81 and CD9 (P < 0.01), while Calnexin was negative. After co-culture BMSC with GelMA for 5 days, live/dead staining indicated an increase in cell survival rate (P < 0.01). The results of Micro-CT, three-dimensional reconstruction and HE showed that compared with the NC group, the GelMA+EXO group had the most new bones (P < 0.01).

Conclusions GelMA hydrogel combined with BMSC-derived EXO has a synergistic effect on the repair of rat calvarial defect.