Study on the mechanism of low-frequency electromagnetic field promoting the healing of ischemic foot ulcer in experimental rabbits

Abstract

Objective By modeling ischemic foot ulcers in experimental rabbits, the mechanism of healing in animal models was investigated. Methods Sixty healthy male clean grade New Zealand rabbits were 3 months. The weight range was 2.1-2.5 kg. Randomly draw auording to the number, the experimental rabbits were randomly divided into 4 groups, namely, no ischemia-no ulcer-no intervention group (group A), no ischemia-no ulcer-no intervention group (group B), no ischemia-no ulcer-no intervention group (group C) and no ischemia-ulcer-intervention group (group D), with 15 rabbits in each group. Ischemic foot ulcers experimental rabbit building complete after 24 h, will naturally exposed ischemic foot ulcers in the low frequency electromagnetic field on experimental rabbit 7 d feeding experiment, the experimental rabbits ischemia crus muscle and the ulcer base were collected, and plasma by enzyme-linked immunosorbent assay (ELISA) verification tests in experimental rabbit plasma hypoxia-inducible factor 1 alpha subunit (HIF-1α), matrix metalloproteinases 9 (MMP-9) and soluble leukocyte differentiation antigen 40 ligand 1 (sCD40L1) expression level, while detecting ulcer healing area change, hematoxylin-eosin staining was used to detect and analyzed the pathological changes of ulcerated skin. Measurement data were expressed as mean±standard deviation (Mean±SD), one-way analysis of variance was used for comparison between groups, and LSD method was used for pairwise comparison. Results The concentration of MMP-9 and sCD40L1 in group D were (40.510±10.155) ng/ml and (44.580±19.138) ng/ml, respectively. Concentrations in group C were (93.210±17.838) ng/ml and (318.500±52.680) ng/ml, respectively. Group D was significantly lower than group C, and the difference was statistically significant (P< 0.000 1). The concentrations of HIF-1α in group D was (249.700±71.824) ng/ml, and that in group C was (124.830±20.110) ng/ml. The concentration in group D was significantly higher than that in group C, and the difference was statistically significant (P< 0.000 1). The concentrations of HIF-1α, MMP-9 and sCD40L1 in group B were (181.590±31.927), (78.950±16.652) and (173.670±43.048) ng/ml, respectively. The concentrations of group A were (35.420±9.916), (32.700±6.449) and (47.440±11.831) ng/ml, respectively. The concentration in group B was significantly higher than that in group A, the difference was statistically significant(P<0.000 1). The concentration of HIF-1α in group D was (249.700±71.824) ng/ml, and the concentration of group A was (35.420±9.916) ng/ml. The concentration of group D was significantly higher than that of group A, and the difference was statistically significant (P=0.000 1). The concentration of the MMP-9 in the group D was compared with the concentration of group A, and the difference was not statistically significant (P=0.207). The concentration of sCD40L1 in group D was (44.580±19.138) ng/ml, and that in group A was (47.440±11.831) ng/ml. The difference between group D and group A was not statistically significant(P=0.858). The healing area of ulcer was (1.855±0.394) cm2 in group D and (0.653±0.269) cm2 in group C. Group D was significantly higher than group C, and the difference was statistically significant (P<0.000 1). Hematoxylin-eosin staining results of ulcer skin showed that the epithelial of ischemic foot ulcer was significantly atrophied, hyperkeratinized, and the acinous cell layer was atrophied with a small amount of obvious inflammatory cell infiltration and hyperplasia of small vessels. After intervention, the symptoms were relieved. Conclusion Low frequency electromagnetic fields can promote the expression of HIF-1α in experimental rabbits, inhibit the expression of MMP-9 and sCD40L1, and promote the healing of ischemic foot ulcer. Key words: Foot ulcer; Matrix metalloproteinase 9; Electromagnetic fields; Hypoxia-inducible factor 1, alpha subunit; Rabbits