CLINICAL-FEATURES OF PHOTODAMAGED HUMAN SKIN ARE ASSOCIATED WITH A REDUCTION IN COLLAGEN-VII

Chronically sun-exposed or photodamaged human skin is characterized by a number of clinical features, including wrinkles. However, little is known about the molecular mechanisms that underlie these features, We investigated the hypothesis that the mechanism of wrinkle formation m ay involve ire loss of anchoring fibrils, composed mainly of collagen VII, which are important in maintaining dermal-epidermal junction inte grity. Ten volunteers with moderate to severe photodamage of dorsal fo rearm skin were recruited to the study, Using immunohistochemistry, tr ansmission electron microscopy and in situ hybridization, we compared collagen VII protein and mRNA content of photodamaged forearm skin wit h that of sun-protected hip and upper inner arm skin from the same sub jects, Numbers of anchoring fibrils per linear mu m of basement membra ne (mean+/-SEM) were significantly lower in photodamaged skin (1.79 +/ - 0.10) as compared with sun-protected hip (2.28 +/- 0.11) and upper i nner arm shin (2.21 +/- 0.10) (P<0.01), and similarly keratinocyte exp ression of collagen VII mRNA, quantitated as number of positively stai ned keratinocytes per high power field, was significantly reduced in p hotodamaged skin (6.3 +/- 2.5) as compared with sun-protected hip (20. 0 +/- 5.6) and upper inner arm skill (17.7 +/- 4.9) (P<0.001). Semiqua ntitative assessment of immunohistochemical staining for collagen VII showed a non-significant reduction in photodamaged skin as compared wi th sun-protected skin. We propose that reduced content of collagen VII in photodamaged skin contributes to wrinkle formation by weakening th e bond between the dermis and epidermis.