Distribution and expression of type VI collagen in photoaged skin

Background Several of the characteristic clinical features of photoaged ski n, including wrinkling, are thought to be dependent on changes in the derma l matrix brought about by chronic sun exposure. Such changes include reduct ions in collagens I, III and VII, an increase in elastotic material in the reticular dermis and a marked reduction in the microfibrillar glycoprotein fibrillin. Objectives To examine whether type VI collagen, a microfibrillar collagen n ecessary for cell-cell and cell-matrix communication, is affected by the ph otoageing process. Methods Six healthy volunteers with moderate to severe photoageing were enr olled into the study. Immunohistochemistry and in situ hybridization histoc hemistry were used to examine the levels of type VI collagen in photoprotec ted and photoaged sites. Results In photoprotected skin, type VI collagen was concentrated in the pa pillary dermis immediately below the dermal-epidermal junction, around bloo d vessels, hair follicles and glandular structures. The distribution of typ e VI collagen was unchanged in photoaged skin, although we observed an incr ease in the abundance of the alpha3 chain of collagen VI in the upper papil lary dermis, at its junction with the dermal-epidermal junction (P < 0.05). No alterations were observed for any a chain at the mRNA level. Conclusions These studies suggest that chronic sun exposure (photoageing) h as little or no effect on either the distribution, abundance or levels of e xpression of type VI collagen in human skin. Thus, type VI collagen, unlike other matrix components so far studied, appears to be relatively unaffecte d by the photoageing process.