[In situ hybridization--an expansion of dermatologic histopathology]

By means of in-situ-hybridization, we are able to detect specifically the mRNAs of defined proteins at a cellular level in frozen sections. This technique not only makes it possible to characterize the biosynthesis of defined proteins at a pretranslational level but can also identify activated cells in their histological surroundings. We employed this technique in order to detect collagen mRNAs in fibrotic diseases of the skin. Using cDNA clones for collagen type I, we proved that in early stages of scleroderma the fibrosis starts in the deep dermis and the subcutaneous fatty tissue. In addition, the regulation of the collagen synthesis seems to be disturbed at a pretranslational level and accompanied by dramatically increased levels of collagen mRNA in fibroblasts. This technique offers objective parameters for collagen mRNA and may be especially useful to estimate the activity of fibrotic diseases in individual patients as well as during therapeutical trials.