Abstract: Objective To quantify the contents of type I and III collagens and their ratios in normal skin and hypertrophic scar in people of different ages, and to explore the rule and cause of changes. Methods Normal human skin specimens and hypertrophic scar specimens were obtained from spontaneously aborted fetus and people of different ages, including the children and adolescent group(≤18 years), adult group(19-50 years), elderly group(>50 years). The total collagen contents were determined by hydroxyproline method. The ratios of types I and III collagens were examined by immunohistochemistry, and their contents were calculated. Results The difference of the contents of types I and III collagens and their ratios in normal skin were statistically significant among different age groups(P=0.01). Their ratios increased with the increase of age, and the differences were statistically significant among different age groups(P=0.02). The difference of contents of types I and III collagens and their ratios in hypertrophic scars were statistically significant among all groups, also between any two groups(P=0.03). In every age group, the difference of the contents of types I and III collagens and their ratios between normal skin and hypertrophic scar was statistically significant (P=0.02). Conclusion With age increasing, the changes of the ratios of types I and III collagens in the normal skin changes, which results in changes of the tension and elasticity of skin and the healing process after injury. The contents of types I and III collagens and their ratios significantly changes in hypertrophic scars, resulting in different structure of scar from normal skin.

Key words: Age group, Collagen, Hypertrophic scar, Immunohistochemistry, Hydroxyproline