Bone morphogenetic proteins 2, 5, and 6 in combination stimulate osteoblasts but not osteoclasts in vitro

Bone regeneration is required for fracture healing. Various procedures have been used to promote osteogenesis with bone morphogenetic proteins (BMPs). We assessed the effects of BMP-2, BMP-5, and BMP-6 in isolated and combined use on the generation of osteoblasts and osteoclasts by comparing the osteoclastic potency of each on osteoclasts of primary murine bone marrow cells. Subsequently, cells were stained for tartrate-resistant acid phosphatase, and real time PCR analysis of receptor activator of NKκB ligand and osteoprotegerin was conducted. The same combination of BMPs was used to assess their potential to enhance osteoblasts, employing a mineralization assay and real-time PCR analysis of collagen type-1, runx2, and osterix. While BMP-2 alone and the combination of BMP-2 and BMP-5 significantly enhanced osteoclastogenesis, BMP-2, BMP-5, and BMP-6 in combination did not have additional effects. However, the combined use of BMP-2, BMP-5, and BMP-6 had an additive effect on matrix mineralization and osterix expression in osteoblasts. Our study shows that the combination of BMP-2, BMP-5, and BMP-6 stimulates osteoblasts but not osteoclastogenesis. Thus, the synergistic use of various BMPs might improve effective bone regeneration in the clinical setting.