Effects of pulsed electromagnetic fields on cartilage apoptosis signalling pathways in ovariectomised rats

Abstract

Purpose: The purpose of this study was to determine the effect of exposure to pulsed electromagnetic fields (PEMF) on modulation of the cartilage apoptosis signalling pathway in ovariectomised rats by monitoring the expression of mRNA of X-linked inhibitor of apoptosis protein (XIAP) and Bax.

Methods: Forty-eight female Sprague-Dawley rats (250 ± 50 g) were randomly assigned to one of four groups: ovariectomy with PEMF treatment (PEMF group), ovariectomy with oestradiol (E2) treatment (oestrogen group), ovariectomy control (OVX group) and sham group. The ovariectomy model was prepared by surgical resection of the ovaries. After a three-month intermission, animals in the PEMF and oestrogen groups received treatment for 30 days; then serum 17β-oestradiol levels, chondrocyte morphology, and XIAP and Bax mRNA expression in knee joint cartilage were analysed.

Results: The results showed different chondrocyte formation in each group. Serum E2 content in the PEMF and oestrogen groups was significantly higher than in the OVX group (p < 0.05). The expression of XIAP mRNA in the PEMF and oestrogen groups was significantly up-regulated compared to the OVX group, while that of Bax mRNA was significantly down-regulated (p < 0.05). The correlation between E2 level and expression of Bax mRNA was positive (0.506) and statistically significant (p < 0.001).

Conclusion: These data demonstrate that PEMF can up-regulate XIAP mRNA expression and down-regulate Bax mRNA expression in ovariectomised rats. Changes in XIAP and Bax mRNA expression may be the mechanism by which PEMF therapy affects postmenopausal osteoarthritis.

Fig. 1

a H&E stain of cartilage tissue for the sham group, ×200 magnification Grade 0 (arrows represented the smooth cartilage surface and organised chondrocytes). b H&E stain of cartilage tissue for the PEMF group, ×200 magnification Grade 1 (arrows represented retention of the articular surface layer). c H&E stain of cartilage tissue for the estrogen group, ×200 magnification Grade 1 (arrows represented retention of the articular surface layer). d H&E stain of cartilage tissue for the OVX group, ×200 magnification Grade 2 (arrows represented focal discontinuity of the cartilage superficial zone)

Fig. 2

Effect of PEMF on expression of XIAP and Bax genes in cartilage tissue. The means of △CT for XIAP and Bax expression in the four groups are shown. The expression levels of mRNA were determined using real-time PCR. Real-time PCR analysis showed a significant decrease in XIAP mRNA levels in the PEMF and oestrogen groups, and a significant increase in Bax mRNA levels in the PEMF and oestrogen groups compared to the sham and OVX groups (p < 0.05) (n  = 12 in each group)

Fig. 3

a Simple scatter plot for the correlations of E2 and XIAP. The variables were not approximately normally distributed and have some outliers. b Simple scatter plot for the correlations of E2 and Bax. There was a linear relationship between the E2 level and mRNA expression of Bax