The present study was designed to investigate the expression of type I, III and VI
collagens by a fibroblast cell line initiated from a
hypertrophic scar. The same tissue has previously been demonstrated to display markedly elevated expression of type I and III
collagen mRNAs in vivo. Unexpectedly, slot-blot and Northern hybridizations revealed a barely detectable steady-state level of pro alpha 1(III)
collagen chain
mRNA in cultured
hypertrophic scar fibroblasts. The levels of pro alpha 1(I) and alpha 2(VI)
collagen chain mRNAs were essentially the same in fibroblasts cultured from
hypertrophic scar and in fibroblasts cultured from normal skin. However, Northern blot analyses indicated that the ratio of 5.8 kb to 4.8 kb species of pro alpha 1(I)
collagen mRNA was slightly reduced in fibroblasts originating from the
hypertrophic scar compared to that in normal fibroblasts. When normal fibroblasts were incubated in
conditioned medium from
hypertrophic scar cultures, the expression of pro alpha 1(III)
collagen chain
mRNA decreased to a markedly lower level. Our studies suggest that
collagen synthesis by fibroblasts in
hypertrophic scars is stimulated by humoral factors which are active only in vivo. Furthermore, the results suggest that fibroblasts cultured from
hypertrophic scar display a selective downregulation of different
collagen genes and that this downregulation is exerted through an autocrine mechanism.