Effect of low-frequency pulsed electromagnetic fields on activity of rat calvarial osteoblasts through IGF-1R/NO signaling pathway

Abstract

To investigate the effect of low-frequency pulsed electromagnetic fields (PEMF) on the maturation and mineralization of rat cranial osteoblasts in vitro and its relation to IGF-1R/NO signaling pathway. The rat osteoblasts were isolated and cultured in vitro and randomly divided into blank control group, PEMF group, GSK group (IGF-1R blocker) and PEMF+GSK group. The cells were treated with 50 Hz 0.6 mT PEMF for 1.5 h/d. After 3 d of PEMF treatment, the expressions of protein kinase (AKT), inducible nitric oxide synthase (iNOS) and cGMP-dependent protein kinase (PKG) were detected by Western blotting; on 6 d of PEMF treatment alkaline phosphatase (ALP) activity was determined; on 12 d of PEMF treatment the calcification nodule formation was demonstrated by Alizarin red staining. NO level was significantly increased in rat osteoblasts treated with 50 Hz 0.6 mT PEMF for 1.5 h/d. Western blot analysis showed that the expressions of AKT, iNOS and PKG protein in PEMF group were higher than those in the control group (all P<0.01); the ALP activity was increased(P<0.05), and the PEMF group had the largest area of Alizarin red staining (P<0.01). The expressions of AKT, iNOS and PKG protein in GSK group were lower than those in the control group; the ALP activity was decreased (P<0.05), and the GSK group had the least area of Alizarin red staining (P<0.01). The expressions of AKT, iNOS, PKG protein, the ALP activity and the area of Alizarin red staining in PEMF+GSK group were between PEMF group and GSK group. PEMF may enhance the maturation and mineralization of rat cranial osteoblasts in vitro through IGF-1R/NO signaling pathway.