Expression of decorin and collagens I and III in different layers of human skin in vivo: a laser capture microdissection study.

Extracellular matrix (ECM) organization is a complex process that requires the coordinated efforts of many molecules. For the regulation of collagen fiber diameter, the proteoglycan decorin appears to be of major relevance. To investigate the role of decorin in the process of (photo-)aging in more detail, full-thickness punch biopsies were isolated from human buttock skin. Single exposure with two minimal erythemal doses of solar simulated irradiation caused down-regulation of decorin mRNA in young (n = 5) and old subjects (n = 5) after 24 h. Interestingly, decorin mRNA was elevated with age. To test the hypothesis that a decreased collagen-to-decorin-ratio impairs collagen structure we also investigated collagens I and III gene expression. Both were down-regulated with increasing age and after single UV-irradiation. As determined by laser capture microdissection-quantitative real time-Polymerase chain reaction (n = 11), decorin is mostly present in the reticular dermis while being absent from the papillary dermis. Minor expression was also observed in the epidermis. However, in contrast to full-thickness skin biopsies age-dependent changes in collagens I, III, and decorin expression could not be observed with this methodology indicating technical limitations. Together with our finding that collagens I and III mRNA are similarly expressed in the reticular and papillary dermis and are down-regulated by UV, our studies support the idea of a major role of decorin in ECM organization. Altered expression of decorin mRNA in the different dermal strata and a decrease in the collagen-to-decorin ratio inflicted by both age and ultraviolet irradiation possibly affect collagen bundle diameter and subsequently the mechanical properties of human skin.

Novel aspects of intrinsic and extrinsic aging of human skin: beneficial effects of soy extract.

Biochemical and structural changes of the dermal connective tissue substantially contribute to the phenotype of aging skin. To study connective tissue metabolism with respect to ultraviolet (UV) exposure, we performed an in vitro (human dermal fibroblasts) and an in vivo complementary DNA array study in combination with protein analysis in young and old volunteers. Several genes of the collagen metabolism such as Collagen I, III and VI as well as heat shock protein 47 and matrix metalloproteinase-1 are expressed differentially, indicating UV-mediated effects on collagen expression, processing and degradation. In particular, Collagen I is time and age dependently reduced after a single UV exposure in human skin in vivo. Moreover, older subjects display a lower baseline level and a shorter UV-mediated increase in hyaluronan (HA) levels. To counteract these age-dependent changes, cultured fibroblasts were treated with a specific soy extract. This treatment resulted in increased collagen and HA synthesis. In a placebo-controlled in vivo study, topical application of an isoflavone-containing emulsion significantly enhanced the number of dermal papillae per area after 2 weeks. Because the flattening of the dermal-epidermal junction is the most reproducible structural change in aged skin, this soy extract appears to rejuvenate the structure of mature skin.

Tight control of matrix metalloproteinase-1 activity in human skin.

Chronic ultraviolet irradiation leads to photoaging in human skin, which is associated with degradation of connective tissue. This is partly due to the fibroblast collagenase (matrix metalloproteinase 1 [MMP-1]). Using complementary DNA array technique we demonstrate that after UV irradiation, MMP-1, MMP-3 and the tissue inhibitor of matrix metalloproteinase 1 (TIMP-1) are time-dependently induced on the messenger RNA level in dermal fibroblasts in vitro and in vivo in human buttock skin. This increase in gene expression is paralleled by an increase of latent and active MMP-1 protein after low-dose UV-A exposure in vitro. In vivo the concentration of latent MMP-1 in suction blister fluids peaks 24 h after irradiation with 2 minimal erythema doses of solar simulated radiation. However, only a small proportion of MMP-1 in vitro (5.5 +/- 1.5%) and in vivo is active, whereas the majority of MMP-1 remains in its inactive proform. Interestingly, in suction blister fluid the concentration and duration of TIMP-1 expression exceeds that of MMP-1. Taken together, these data indicate that MMP-1 activity is tightly regulated transcriptionally and posttranscriptionally. Furthermore, the pronounced individual differences in all targets investigated provide a possible explanation for the different susceptibility of individuals to UV exposure and, thus, to the clinical features of photodamage.

Influence of flavonoids and vitamins on the MMP- and TIMP-expression of human dermal fibroblasts after UVA irradiation.

UV irradiation leads to distinct changes in skin connective tissue by degradation of collagen, for example. Many of these alterations in the extracellular matrix are mediated by MMPs (matrix metalloproteinases) with reduced content of their antagonist TIMPs (tissue inhibitors of metalloproteinases). Potential candidates to reduce MMP activity in the skin after solar stimulation were examined. The influence of vitamin C, vitamin E and the flavonoids AGR (alpha-glucosylrutin) and 8-prenylnaringenine on the MMP and TIMP expression was investigated. Human dermal fibroblasts were incubated with these additives and irradiated with UVA [10 J cm(-2)]. The gene expression of MMP-1 (collagenase-1) and TIMP-1, the protein expression of MMP-1, MMP-2 (gelatinase-A), TIMP-1 and TIMP-2 as well as the enzyme activity of MMP-1 and MMP-2 were examined. AGR and vitamins C and E were shown to reduce MMP expression and activity, whereas 8-prenylnaringenine appeared to be responsible for the opposite effect. None of the substances considerably influenced the TIMP levels. AGR represented the most effective additive in reducing the collagenase protein expression to 60% and may be useful to level out the MMP activity in the skin after sun exposure. Furthermore, no protein expression of MMP-8, MMP-9, MMP-12 and MMP-13 could be detected.