Effects of melatonin on the expression of type I collagen and type III collagen in hypertrophic scar of rabbit ear

Objective To observe the effect of melatonin on the expression of type Ⅰ collagen and type Ⅲ collagen in hypertrophic scar of rabbit ears. Methods The animal model of hypertrophic scar of rabbit ears was established, and the experimental group of melatonin and the blank control group were set up. Experimental group: intraperitoneal injection of 5.0 mg/kg melatonin every day; blank control group: intraperitoneal injection of equal amount of saline daily. After 6 weeks of rearing, cicatricial tissue and fixed specimen were collected. The thickness of the scar was measured by hematoxylin-eosin (HE) staining and the percentage of the area of collagen was measured by Sirius red staining. Results On the forty-second day, the degree of scar hyperplasia in the experimental group was significantly lower than that in the control group. The thickness of scar tissue in the experimental group was (920.30±227.56) μm, and the thickness of the control group was (1 033.10±263.59) μm. The scar hyperplasia in the control group was stronger than that in the experimental group (P=0.000). The content of type Ⅰ collagen in experimental group was (0.115±0.051)%, and the content of type Ⅰ collagen in control group was (0.148±0.043)%, the content of type Ⅰ collagen in the experimental group was lower than that of the control group (P=0.026). The content of type Ⅲ collagen in experimental group was (0.145±0.041)%, while that in control group was (0.121±0.034)%, the content of type Ⅲ collagen in the experimental group was higher than that of the control group (P=0.013). Conclusion The results indicate that melatonin can reduce scar proliferation through regulating the proportion of collagen type Ⅰ and type Ⅲ. Key words: Melatonin; Hypertrophic scar; Collagen