LONG-TERM SUN EXPOSURE ALTERS THE COLLAGEN OF THE PAPILLARY DERMIS - COMPARISON OF SUN-PROTECTED AND PHOTOAGED SKIN BY NORTHERN ANALYSIS, IMMUNOHISTOCHEMICAL STAINING, AND CONFOCAL LASER-SCANNING MICROSCOPY

Background: Long-term solar irradiation produces both morphologic and functional changes in affected skin. Because collagen is the major str uctural component of skin, any alteration in its production or degrada tion could have profound effects on cutaneous functional integrity. Ob jective: Our purpose was to investigate alterations in the production and morphology of collagen fibers brought about by long-term sun expos ure. Methods: We compared collagen and collagenase gene expression and collagen immunohistochemical staining and used confocal laser scannin g microscopy for morphologic examination of dermal collagen fibers in photodamaged compared with sun-protected skin from the same persons. R esults: Despite a large increase in elastin messenger RNA in sun-damag ed skin, collagen and collagenase gene expression remained essentially unchanged. However, striking alterations in the papillary dermis of p hotoaged skin were found, which revealed large, abnormally clumped ela stic fibers and deformed collagen fibers of various diameters, replaci ng the normal architecture of the papillary dermis. Conclusion: Our da ta provide evidence for normal collagen gene expression in sun-damaged skin and suggest that degradation and remodeling of collagen take pla ce in the papillary der mis accompanied by deposition of other matrix components, predominantly abnormal elastic fibers.