Biofunctionalization of mineralized collagen with platelet-rich plasma enhances osteogenesis in critical-sized bone defects

Introduction Bone defects caused by fractures, nonunion, tumors, or infections severely impair patient quality of life. Although autologous bone grafting remains the gold standard, its limited donor availability and additional surgical trauma have driven the development of biomimetic substitutes. Mineralized collagen (MC) replicates native bone extracellular matrix but lacks osteoinductive capacity. Platelet‐rich plasma (PRP) is a fibrin matrix enriched with growth factors (e.g., VEGF, PDGF, TGF‐β1, IGF‐1) that promote cell proliferation and osteoblastic differentiation, yet its gel‐like form suffers from poor structural integrity in bone defects. Methods This study investigated whether the combination of PRP and MC produces enhanced effects on osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) and healing of critical‐sized bone defects. PRP + MC composites were prepared by immersing MC scaffolds in PRP and evaluated using rat BMSCs in vitro (proliferation, ALP, Alizarin Red S, RUNX2 qRT‐PCR). In vivo , critical‐sized cylindrical femoral condyle defects (3 mm diameter, 5 mm depth) were created in male SD rats and filled with PRP + MC, MC, PRP, or normal saline. Bone regeneration was analyzed by Micro‐CT at 12 weeks, and histology was performed using H&E, Masson's trichrome, and OPN immunohistochemistry. Results The PRP + MC composite significantly enhanced BMSC proliferation at day 7. ALP activity and mineralization were markedly increased, accompanied by significantly upregulated RUNX2 expression (∼5.6‐fold vs. control). Micro‐CT revealed near‐complete defect filling with high‐density trabecular architecture. Histologically, the composite group exhibited the highest new bone area (∼75%) and OPN expression, with mature lamellar bone and host integration, whereas controls remained dominated by fibrous scar tissue. Discussion PRP + MC represents a biomimetic and cost‐effective strategy for enhancing bone repair. By combining structural scaffolding with biological stimulation, this composite activates RUNX2‐mediated signaling and achieves enhanced regeneration in critical‐sized defects, supporting its preclinical potential as an alternative to autologous bone grafting.