Matrix Metalloproteinase‐1 Production Observed After Solar‐Simulated Radiation Exposure is Assumed by Dermal Fibroblasts but Involves a Paracrine Activation Through Epidermal Keratinocytes¶

Abstract

ABSTRACTChronic exposure of human skin to solar UV radiation leads to serious dermal damages, a hallmark of photoaging. In vivo, acute UV radiation has been shown previously to induce various matrix‐degrading proteases. Among them, matrix metalloproteinase‐1 (MMP‐1) has been suggested to be involved in skin photodamage. The purpose of this study was to investigate the effects of solar‐simulated radiation (SSR) on MMP‐1 production in normal human skin cells. SSR exposure of human skin reconstructed in vitro comprising both a differentiated epidermis and a fibroblast‐populated dermal equivalent led to an increase in MMP‐1 production, which was abolished when epidermis was removed immediately after SSR exposure. In addition, SSR exposure of differentiated keratinocytes grown on an acellular collagen gel did not induce MMP‐1 production. Experiments on cell cultures grown on plastic confirmed that keratinocytes failed, in contrast with fibroblasts, to produce MMP‐1 in response to SSR exposure. However, when conditioned medium from SSR‐exposed keratinocytes was added to human fibroblasts in culture, MMP‐1 production was induced. Altogether, these data show that MMP‐1 production observed after SSR exposure involved the release of soluble epidermal factors, which could modulate its production by dermal fibroblasts.