Hypoxia inhibits osteoblast proliferation.
(A) Osteoblast number counts in the growth medium. MC3T3 osteoblastic cells were cultured in Alpha Minimum Essential Medium, and maintained for different time points as indicated from 4 hr to 72 hr in normoxic (20%O2) or hypoxia (1%O2) condition. (B) Inhibition of HIF-1α expression by siRNA resulted in an increase of osteoblast growth. MC3T3 osteoblastic cells were transfected by siRNA, and cultured under hypoxia for 48 hr. si-control: si-RNA control; si-HIF-1α: si-RNA against HIF-1α. A paired t-test was performed comparing si-control group and si-HIF-1α group. *: A star indicates statistical significance compared to control group.