Activation of type I collagen genes in cultured scleroderma fibroblasts

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Abstract
Fibroblasts cultured from affected skin areas of five patients with cutaneous scleroderma were found to produce increased amounts of collagen when compared with nonaffected control cells. Total RNA was isolated from the cultures and analyzed for its level of proα1(I)collagen mRNA by hybridization of RNA blots with a cloned cDNA probe. The levels of proα1(I)collagen mRNAs relative to total RNA were two‐ to sixfold higher in the samples from affected cells, accounting for the increased synthesis of type I collagen. Cytoplasmic dot hybridizations were performed to measure the cellular content of proα1(I)collagen mRNA: up to ninefold increases in the level of this mRNA per cell were found. Upon subculturing, scleroderma fibroblasts were found to reduce gradually the increased synthesis of collagen to the level of non‐affected controls by the tenth passage. The levels of type I collagen mRNAs were also reduced, but more slowly. The results suggest that in scleroderma fibroblasts the genes for type I collagen are activated at procollagen mRNA level or that they are more stable and that the activating factors are lost during prolonged cell culture because cells from affected areas lose their activated state.

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