Objective: To observe the change in expression of vascular endothelial growth factor (VEGF) in serum and wound tissue of rats with electrical burn (EB), and to explore its regulation mechanism in the pathological changes of EB.
Methods: Sixty-four SD rats were divided into normal control group (n = 8) and EB group (n = 56) according to the random number table. Eight rats in EB group were sacrificed at post injury hour (PIH) 6 and on post injury day (PID) 1, 3, 7, 14, 21, and 28, to collect wound muscle tissue and serum samples. Histopathological changes in wound tissue were observed with HE staining. The serum content of VEGF was determined with double-antibody sandwich enzyme-linked immunosorbent assay. The expression level of VEGF in wound tissue was determined with Western blotting. VEGF expression intensity in wound tissue was observed with immunohistochemical staining. The microvessel density (MVD) was calculated. The correlation between VEGF expression intensity and MVD was analyzed. Muscle tissue of calf and serum of the rats in normal control group without any treatment were collected for above-mentioned observations and determinations. Data were processed with one-way analysis of variance and Spearman hierarchy correlation analysis, and LSD-t test was applied for paired comparison.
Results: (1) In EB group, breakage of muscle fiber, heavy infiltration of inflammatory cells, and obvious tissue edema were observed at PIH 6 and on PID 1; new vessels were observed on PID 3; amount of granulation tissue and number of new vessels were found to be increased on PID 7. (2) In EB group, the serum level of VEGF was (43 ± 11) pg/mL at PIH 6, (44 ± 11) pg/mL on PID 1, and (74 ± 27) pg/mL on PID 14, which were all significantly higher than that in normal control group [(15 ± 9) pg/mL, with t values from 4.001 to 5.724, P values all below 0.01]. (3) The protein expression level of VEGF of wound tissue in EB group was higher than that in normal control group (0.21 ± 0.09) at each time point. The protein expression level of VEGF in EB group peaked on PID 7 (0.63 ± 0.13, t = 4.965, P < 0.05). (4) In EB group, strongly positive expression of VEGF was observed in inflammatory cells at early stage and in new vascular endothelial cells at late stage. (5) The expression intensity of VEGF was positively correlated with MVD in wound tissue on PID 3, 7, 14, 21, and 28 in EB group (r(s) = 0.834, P < 0.01).
Conclusions: Different expression levels of VEGF were observed in serum and wound tissue of rats at various stages after EB, and they were closely correlated with different stages of fluid exudation and wound healing process after EB.