NORMAL AND HYPERTROPHIC SCARS - QUANTIFICATION AND LOCALIZATION OF MESSENGER-RNAS FOR TYPE-I, TYPE-III AND TYPE-VI COLLAGENS

The expression of type I, III and VI collagens was studied in nine nor mal and two hypertrophic scars using slot-blot and in situ hybridizati on techniques. Slot-blot hybridization indicated that the steady-state levels of pro alpha 1(I) and pro alpha 1(III) collagen chain mRNAs we re moderately elevated in two of the nine normal scars, whereas the tw o hypertrophic scars analysed displayed markedly elevated mRNA levels when compared with normal skin. The mRNA levels of alpha 2(VI) collage n chain were only slightly elevated in both types of scars studied. In situ hybridization was most informative when applied to hypertrophic scars. These lesions were characterized by the presence of intense hyb ridization signals for type I and m collagen mRNAs, and a moderate sig nal for type VI collagen mRNA, in nodules which were located in the up per dermis on each side of the original wound. This may explain, in pa rt, why hypertrophic scars rise above the level of the surrounding ski n. The results of the present study are in marked contrast to our prev ious findings on collagen gene expression in keloids and neurofibromas , in which the steady-state levels of type VI and I collagen mRNAs in particular were shown to be elevated. Thus, our results emphasize that distinct molecular mechanisms are operative in the development of cli nically different dermal fibrotic conditions, such as normal and hyper trophic scars, keloids and neurofibromas.