Image analysis of dermal collagen changes during skin aging

OBJECTIVE: To determine progressive quantitative, directional and textural changes in dermal collagen as a function of age and sex and to estimate the ir evolutive function of age and sex and to estimate their evolutive trend with appropriate regression models. STUDY DESIGN: Ninety-six samples of abdominal skin fi om autopsy cases were analyzed. The ages ranged from 3.5 months to 86 years. Picro-Sirius-staine d slides were examined by polarizing microscopy, and spatial density, direc tional features and texture of collagen were measured by computerized image analysis. Nonlinear regression models were built to estimate evolutive cha nges with respect to age. The relationship between spatial orientation of c ollagen bundles and age was best modeled by RESULTS: The evolutive patterns of dermal thickness and spatial density of collagen bundles correspond to a second-order polynomial model with it prog ressive in crease from childhood to middle age and a relatively sharp decre ase after the seventh decade. The evolution of textural pattern of dermal c ollagen, defined by gradient analysis, depicts a sort of inverted U. Its co mplexity is vied 25-50 years and increases progressively after the sixth de cade. The horizontal or orientation of collagen bundles with intermingled f ascicles oriented in other directions, shown by young individuals, is progr essively simplified with aging. In elderly subjects, collagen bundles have a horizontal orientation. No significant sex-related differences were found . CONCLUSION: Dermal collagen changes related to aging are apparently indepen dent of sex, at least in abdominal skin, and show characteristic curvilinea r evolutive trends defined by decreased dermal thickness in the elderly, de crease in the spatial density of collagen bundles and increase in textural heterogeneity of the dermis. Progressive simplification in the orientation of collagen bundles leading to a predominant horizontal disposition followe d a linear trend. These changes could contribute to providing a substantial morphologic basis to age-associated biomechanical alterations in the skin.