To investigate the effect and related mechanism of LED red light irradiation on wound healing in diabetic rats.

Thirty 4-week-old male SD rats were divided into 3 groups, normal wound group, diabetic wound group, and diabetic wound treated with red light group according to the random number table method, with 10 rats in each group. The rats in diabetic wound treated with red light group and diabetic wound group had a high-fat diet for 4 weeks, and the rats in the normal wound group had a normal diet. After 4 weeks, the rats in the diabetic wound treated with red light group and the diabetic wound group were intraperitoneally injected with 10 mg/mL Streptozotocin (STZ) at a dose of 50 mg/kg to make diabetes models and both groups of rats were successfully modeled. After successful modeling, two full-thickness skin defect wounds of 1.5 cm×1.5 cm were made on both sides of the backs of the three groups of rats, and the wounds of the rats were disinfected with alcohol every two days, and the wounds of the rats in the diabetic wound treated with red light group were irradiated with LED red light at energy density of 20 J/cm² for 5 minutes after the disfection, the other two groups of rats were not irradiated with LED red light. On the 7th, 10th, 14th, and 21st days of observation, whether there were rashes, redness, blisters, scalds and other adverse light reactions on the wounds of the rats in the diabetic wound treated with red light group were observed, the wound healing condition of the three groups of rats was observed by naked eye, and the wound healing rate of the three groups of rats was counted. On the 10th day of observation, 2 rats were randomly selected from each group, and the back wound tissue was taken after being sacrificed. After fixation, hematoxylin-eosin staining was performed to observe the condition of new blood vessels and the growth of granulation tissue on the wound surface; the expressions of CD34 and vascular endothelial growth factor (VEGF) in wound tissue of rats in each group were detected by immunofluorescence method. Data were compared with one-way ANOVA and LSD-t test.

On the 7th, 10th, 14th, and 21st days, the rats in the diabetic wound treated with red light group were irradiated with LED red light, and there were no adverse light reactions such as rash, redness, blisters, and burns on the skin. At each observation time point, the wound healing of the normal wound group and the diabetic wound treated with red light group was better than that of the diabetic wound group by naked eye observation, and the wound healing of the normal wound group was slightly better than that of the diabetic wound treated with red light group. On the 7th, 10th, 14th, and 21st days of observation, the wound healing rates of the normal wound group were (34.62±2.116)%, (53.83±7.92)%, (70.20±5.41)%, and (95.65±2.58)%, the wound healing rates of the diabetic wound treated with red light group were (31.76±2.44)%, (50.48±4.54)%, (66.26±11.35)% and (93.96±2.80)%, and the wound healing rates of the diabetic wound group were (23.67±4.18)%, (42.71±3.40)%, (53.77±7.74)%, (84.07±4.43)%, respectively, the differences between the three groups were statistically significant (F=34.69, 10.35, 10.32, 34.40; P<0.05). On the 7th, 10th, 14th, and 21st days of observation, the wound healing rates of the normal wound group and the diabetic wound treated with red light group were always higher than those of the diabetic wound group, and the differences were statistically significant (P<0.05). On the 7th and 10th days of observation, the wound healing rates of the normal wound group were higher than those of the diabetic wound treated with red light group, and the differences were statistically significant (t=2.80, 3.26; P<0.05). On the 14th and 21st days of observation, the wound healing rates of the normal wound group were still higher than those of the diabetic wound treated with red light group, but the differences were no statistically significant (t=1.16, 1.40; P>0.05). On the 10th day of observation, hematoxylin-eosin staining of the wound tissue showed that the normal wound group contained a large number of new capillaries, and the collagen and cells in the granulation tissue were arranged in a tight and orderly manner; the diabetic wound treated with red light group saw some new capillaries, there were lots of collagen and cells in the granulation tissue, but less than that in the normal wound group; while the diabetic wound group had the least amount of new blood vessels, and the cells and collagen in the granulation tissue were sparse. The expressions of CD34 and VEGF were observed by immunofluorescence, the expressions of CD34 and VEGF in the normal wound group were higher than those of the diabetic wound treated with red light group, while the expressions of CD34 and VEGF in the diabetic wound treated with red light group were higher than those of the diabetic wound group.

LED red light can promote the expression of CD34 and VEGF in the wound tissue of diabetic rats, promote angiogenesis, and then promote wound healing.