Hyperbaric oxygen therapy accelerates osteoblast differentiation and promotes bone formation

Abstract

OBJECTIVES: Hyperbaric oxygen therapy (HBO) has been used as an adjunctive therapy in the treatment of radiotherapy or bisphosphonate-induced osteonecrosis of the jaw however the effect of HBO on osteoblast formation and mineralisation has not been extensively studied. The current study therefore examined the effects of HBO, elevated pressure or elevated oxygen alone on osteoblast differentiation and bone nodule formation. METHODS: Saos-2 human osteoblast cells were exposed to HBO (2.4 ATA, 97.9% O2, 90 min per day), elevated pressure alone (2.4 ATA, 8.8% O2, 90 min per day) or elevated oxygen alone (1 ATA, 95% O2, 90 min per day) after culturing under normoxic or hypoxic conditions and osteoblast differentiation and bone formation assessed by alkaline phosphatase activity and calcein incorporation. Expression of key regulators of osteoblast differentiation and bone matrix proteins were assessed by quantitative PCR. RESULTS: Daily exposure to HBO accelerated the rate of osteoblast differentiation as determined by increased alkaline phosphatase activity and expression of type I collagen and Runx-2 mRNA during the early stages of culture. HBO also augmented bone nodule formation in hypoxic conditions. HBO had a more pronounced effect on these key markers of osteoblast differentiation than elevated oxygen or pressure alone. CONCLUSIONS: The data from this study shows that daily HBO treatment accelerated the rate of osteoblast differentiation leading to an increase in bone formation. CLINICAL SIGNIFICANCE: These studies add to our understanding of HBO's reparative action in osteonecrotic bone loss. In addition to stimulating angiogenesis HBO may also improve surgical outcomes through a direct beneficial effect on osteoblast differentiation generating a larger bone mass available for reconstruction.