Transforming growth factor-β1 appears to play important roles in normal wound healing by increasing synthesis of extracellular matrix components. However, the role of transforming growth factor-β1 in the production of excessive scar tissue by fibroblasts from stenotic lesions of the larynx has not been evaluated. We examined the effect of transforming growth factor-β1 on the steady-state messenger RNA levels of elastin, α2(I) procollagen, and lysyl oxidase (the enzyme that cross-links both of these structural proteins) in cell cultures of diploid human fibroblasts established from fetal skin, newborn foreskin, and an adult laryngeal stenotic lesion. Time-course and dose-response experiments demonstrated that treatment with 500 pmol/L transforming growth factor-β1 for 20 hours induced maximal levels of mRNA for elastin (7- to 59-fold) and α2(I) procollagen (1.7- to 2.4-fold) in all three cultures of fibroblasts. Transforming growth factor-β1 also increased levels of lysyl oxidase mRNA in fibroblasts cultured from newborn foreskin (2.4-fold) and a stenotic lesion (10-fold) but had minimal effects on the fibroblasts cultured from fetal skin (1.1-fold), which constitutively expressed high levels of lysyl oxidase mRNA. Furthermore, the fibroblast culture established from a laryngeal stenotic lesion responded with the highest fold-induction for all three mRNAs. Inhibition of mRNA synthesis by acti-nomycin D showed that transcription was required for transforming growth factor-β1 induction of elastin, α2(I) procollagen, and lysyl oxidase mRNA in all three cultures of fibroblasts. Inhibition of protein synthesis by cycloheximide showed that translation was required for maximal induction by transforming growth factor-β1 of elastin mRNA but had no observable effect on α2(I) procollagen mRNA in all three cultures of fibroblasts. In addition, translation was required for maximal induction of the iysyl oxidase mRNA by transforming growth factor-β1 in the fibroblasts cultured from a stenotic lesion but not for fibroblast cultures established from fetal and adult skin. These results show that transforming growth factor-β1 coordinately increases mRNA levels for the structural extracellular matrix proteins collagen and elastin, as well as for the cross-linking enzyme, lysyl oxidase. These data also support the hypothesis that transforming growth factor-β1 may contribute to the formation of laryngeal stenotic lesions.
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