Long-term sun exposure alters the collagen of thepapillary dermis

Background: Long-term solar irradiation produces both morphologic and functional changes in affected skin. Because collagen is the major structural component of skin, any alteration in its production or degradation could have profound effects on cutaneous functional integrity. Objective: Our purpose was to investigate alterations in the production and morphology ofcollagen fibers brought about by long-term sun exposure. Methods: We compared collagen and collagenase gene expression and collagen immunohistochemical staining and used confocal laser scanning microscopy for morphologic examination of dermal collagen fibers in photodamaged compared with sun-protected skin from the same persons. Results: Despite a large increase in elastin messenger RNA in sun-damaged skin, collagen and collagenase gene expression remained essentially unchanged. However, striking alterations in the papillary dermis of photoaged skin were found, which revealed large, abnormally clumped elastic fibers and deformed collagen fibers of various diameters, replacing the normal architecture of the papillary dermis. Conclusion: Our data provide evidence for normal collagen gene expression in sun-damaged skin and suggest that degradation and remodeling of collagen take place in the papillary dermis accompanied by deposition of other matrix components, predominantly abnormal elastic fibers.