Das dermale Kompartiment von Altersflecken und die Wirkung von Advanced Glycation End Products (AGEs) auf dermale Fibroblasten

Senile lentigo (SL) lesions from 12 subjects were morphologically analyzed by light and electron microscopy in comparison to unaffected skin. The epidermis from SL revealed morphological features like hyperpigmentation of basal keratinoytes and the formation of elongated rete ridges. S100 positive melanocytes in the stratum basale were not markedly increased, indicating that the hyperpigmentation is predominantly due to changes in the melanin synthesis, distribution or turn-over, respectively. Quantification of epidermal cells expressing the proliferation marker Ki67 did not exhibit an increase of this parameter in SL, indicating that at least in the established lesion cell proliferation is not enhanced. We further focused on the dermal compartment and observed granulated cells which were more abundant in SL. Electron microscopical and histochemical analysis revealed that the granulation of these cells is based on melanosomes, mostly present in large melanosomal complexes. Immunohistochemistry using antibodies against CD68 and factor XIIIa demasked these melanophages predominantly as factor XIIIa positive dermal dendrocytes, which were about 6 times more abundant than CD68 positive macrophages. In SL an increased number of melanophages are found compared with unaffected skin from the same subject. These melanophages are identified as factor XIIIa positive dermal dendrocytes. Advanced glycation end products (AGEs) arise from a complex non-enzymatic reaction of proteins with reducing sugars. In vivo AGE-modified proteins accumulate in several tissues like the dermal skin. To study the effects of AGEs in culture we conducted a genome-wide microarray analysis to compare the gene expression profiles of primary human dermal fibroblasts obtained from skin biopsy specimens from eight individual subjects of different age. Of the 305 genes that passed filtering criteria, further in silico analysis revealed that 30 were differentially expressed between AGE-BSA treated and non-treated fibroblasts. These genes included heme oxygenase 1 (HO-1), NADPH oxidase 4 (NOX4), thioredoxin reductase, NAD(P)H dehydrogenase quinone 1, peroxisome proliferative activated receptor α and glutamate-cysteine ligase modifier subunit, all of which are involved in electron transport or regulation of the cellular redox homeostasis. Subsequently, microarray data were validated applying semi-quantitative RT-PCR. The results verified that HO-1, an anti-oxidative enzyme, and the superoxide producing NOX4 are highly regulated in a contrary manner in virtually all assayed samples. We conclude that AGEs alter the redox state of dermal fibroblasts thereby modulating the expression of redox sensitive genes.