BMP-2 enhanced new bone formation of calcium phosphate-based composites in mice

Autologous bone grafting, particularly using iliac crest bone grafts, historically been considered the gold standard for bone grafting. However, its limited availability and secondary surgical trauma associated with the procedure have restricted its widespread application.

To investigate the osteogenic potential of calcium phosphate-based composites with or without the addition of bone morphogenetic protein-2 (BMP-2).

The BMP-2/calcium phosphate (CaP)/temperature-sensitive hydrogel (BCT) composite was synthesized, while the CaP/temperature-sensitive hydrogel (CT) composite was prepared as control group. The surface morphology of the composites was observed using scanning electron microscope (SEM). Subsequently, the composites were co-cultured with mouse bone marrow mesenchymal stem cells (BMSCs), and the cell proliferation, alkaline phosphatase (ALP) activity and extracellular matrix (ECM) mineralization were assessed. The composites were injected into the muscle of mice, and the samples underwent hematoxylin and eosin (HE), Masson-trichrome, and safranin and fast green staining. Immunohistochemistry for BMP-2 and type I collagen (ColI) was performed at weeks 8 and 12.

There was no significant difference in cell proliferation between the BCT and CT groups. However, the relative ALP activity and ECM mineralization were significantly higher in BCT group compared to the CT group (P < 0.05). BMP-2 accelerated the osteoinduction process and promoted the formation of more new bone tissue and bone marrow in group BCT. The number of osteocytes and the collagen area ratio were significantly higher in group BCT than that in group CT (P < 0.05).

BMP-2 and CaP synergistically accelerated the initiation of osteoinduction, and promoted increased bone formation. The temperature-sensitive hydrogel made the material injectable, expanding its range of applications. The BCT composite shows promise as an artificial bone material.