The effect of nicotine on osteoinduction by recombinant human bone morphogenetic protein 2

Nicotine, one of the constituents of tobacco, is known to have an adverse effect on human health. We sought to clarify the interaction between nicotine and recombinant human bone morphogenetic protein 2 (rhBMP-2) in terms of osteogenesis in vitro and osteoinduction in vivo. Nicotine did not inhibit or stimulate alkaline phosphatase (ALP) activity or the amount of osteocalcin in C2C12 cells in the presence of rhBMP-2 in vitro. Ectopic bone formation using a collagen sponge containing rhBMP-2 was evaluated with and without nicotine after 21 days using radiographic, histological, biochemical, and immunohistochemical analyses. ALP activity in the medium-dose group (2.2 ± 0.9 IU/mg protein; P = 0.047) and the high-dose group (2.0 ± 0.1 IU/mg protein; P = 0.03) was significantly lower than in the control group. The calcium content in the medium-dose group (35.4 ± 12.9 μg/mg tissue; P = 0.0099) and high-dose group (34.8 ± 10.5 μg/mg tissue; P = 0.006) was significantly lower than in the control group. The number of vascular endothelial growth factor-positive cells in the high-dose group (671.9 ± 57.3 cells/mm2; P = 0.03) was significantly lower than in the control group. Results showed that nicotine did not inhibit the stimulatory effect of rhBMP-2 in vitro, but a high dose of nicotine inhibited bone formation in vivo by adversely affecting vascularization.