Pulsed electromagnetic fields protect the balance between adipogenesis and osteogenesis on steroid-induced osteonecrosis of femoral head at the pre-collapse stage in rats

摘要

This study was designed to investigate the effects of pulsed electromagnetic fields (PEMF) on the balance of adipogenesis and osteogenesis on steroid-induced osteonecrosis of the femoral head (OFH) in rats. Forty-two rats were divided into three groups: Steroid group (S, n=16); Steroid+PEMF group (S+P, n=16); and Control group (C, n=10). For groups S and S+P, all rats were first intravenously given 10μg/kg lipopolysaccharide on day 1, and then intramuscularly injected with 20mg/kg methylprednisolone acetate on days 2, 3, and 4, with an interval of 24h. After 4 weeks, the S+P group was treated with PEMF (4.5-ms square pulse, repeated at 15Hz, with a peak of 1.2mT) for 4h a day for the next 8 weeks. Group S was not exposed to PEMF. Group C was chosen as the control group, without steroid use and exposure to PEMF. After 8 weeks of treatment, the histological changes, and mRNA and protein expressions of PPAR-γ2 and Runx2 were measured and analyzed. Compared with the S group, lower incidence of osteonecrosis (31% vs. 69%, P<0.05) and empty osteocyte lacuna rate (36.16±15.34 vs. 59.55±21.70, P<0.01) was observed in the S+P group. Furthermore, PEMF suppressed the expressions of PPAR-γ2 and improved the expressions of Runx2 in the femoral head (P<0.05). All data suggest that PEMF is an effective physiotherapy in the treatment of steroid-induced ONFH, and the possible underlying mechanisms include protecting the balance between adipogenesis and osteogenesis.