Hyperbaric oxygen-stimulated proliferation and growth of osteoblasts may be mediated through the FGF-2/MEK/ERK 1/2/NF-κB and PKC/JNK pathways

We investigated whether the hyperbaric oxygen (O-2) could promote the proliferation of growth-arrested osteoblasts in vitro and the mechanisms involved in this process. Osteoblasts were exposed to different combinations of saturation and pressure of O-2 and evaluated at 3 and 7 days. Control cells were cultured under ambient O-2 and normal pressure [1 atmosphere (ATA)]; high-pressure group cells were treated with high pressure (2.5 ATA) twice daily; high-O-2 group cells were treated with a high concentration O-2 (50% O-2) twice daily; and high pressure plus high-O-2 group cells were treated with high pressure (2.5 ATA) and a high concentration O-2 (50% O-2) twice daily. Hyperbaric O-2 significantly promoted osteoblast proliferation and cell cycle progression after 3 days of treatment. Hyperbaric O-2 treatment stimulated significantly increased mRNA expression of fibroblast growth factor (FGF)-2 as well as protein expression levels of Akt, p70(S6K), phosphorylated ERK, nuclear factor (NF)-kappa B, protein kinase C (PKC)alpha, and phosphorylated c-Jun N-terminal kinase (JNK). Our findings indicate that high pressure and high O-2 saturation stimulates growth-arrested osteoblasts to proliferate. These findings suggest that the proliferative effects of hyperbaric O-2 on osteoblasts may contribute to the recruitment of osteoblasts at the fracture site. The FGF-2/MEK/ERK 1/2/Akt/p70(S6K)/NF-kappa B and PKC/JNK pathways may be involved in mediating this process.