Introduction: Expanded bone damage in defects of critical size demands interventions for the complete regeneration. However, limitations of the previous strategies include reduced availability of autograft donors. The therapeutic efficacy of exosomes has been extensively studied in numerous circumstances such as wound healing, bone and periodontal regeneration.
Aim: This research work aimed to test the efficacy of collagen thermoresponsive hydrogel loaded by BMMSC-derived exosomes on bone regeneration in rats' calvarial critical-size bone defects.
Materials and Methods: Twenty albino rats were allocated into 2 groups, 10 rats each. Group I- collagen hydrogel (COLL), Group II- (COLL+ exosomes). Calvarial critical-size bone defects were surgically created in all groups. The defects in Group I were filled with collagen hydrogel, and in Group II were filled with exosomes-loaded collagen hydrogel. Rats were euthanized after 4 and 8 weeks, and the calvariae were collected and processed. The regenerated bone was evaluated by histology, histomorphometry, and immunohistochemical expression of the bone formation marker osteocalcin.
Results: Analyzing the new bone using histology and histomorphometry revealed an enhanced quantity and pattern of bone formation in defects augmented with collagen hydrogel loaded by exosomes compared to the bare collagen hydrogel group after 4 weeks. However, after 8 weeks no significant difference was detected between groups. Immunohistochemical expression of osteocalcin showed higher values in group II (Coll + exosomes) in comparison to group I collagen hydrogel (COLL).
Conclusion: Bone marrow mesenchymal stem cells derived exosomes loaded collagen thermoresponsive hydrogel provides a precious substitution to cell-based therapy in bone regenerative procedures