Distribution and expression of type VI collagen in photoaged skin

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Abstract
Background Several of the characteristic clinical features of photoaged skin, including wrinkling, are thought to be dependent on changes in the dermal matrix brought about by chronic sun exposure. Such changes include reductions 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 necessary for cell–cell and cell–matrix communication, is affected by the photoageing process. Methods Six healthy volunteers with moderate to severe photoageing were enrolled into the study. Immunohistochemistry and in situ hybridization histochemistry were used to examine the levels of type VI collagen in photoprotected and photoaged sites. Results In photoprotected skin, type VI collagen was concentrated in the papillary dermis immediately below the dermal–epidermal junction, around blood vessels, hair follicles and glandular structures. The distribution of type VI collagen was unchanged in photoaged skin, although we observed an increase in the abundance of the α3 chain of collagen VI in the upper papillary dermis, at its junction with the dermal–epidermal junction (P < 0·05). No alterations were observed for any α chain at the mRNA level. Conclusions These studies suggest that chronic sun exposure (photoageing) has little or no effect on either the distribution, abundance or levels of expression of type VI collagen in human skin. Thus, type VI collagen, unlike other matrix components so far studied, appears to be relatively unaffected by the photoageing process.