The pathophysiologic mechanisms operative in fibrotic pulmonary disease are presently unclear. Since this heterogeneous group of disorders is typically characterized by a substantial accumulation of fibrillar type I collagen in the lung interstitium, it is reasonable to postulate that derangements in the regulation of this secreted protein in pulmonary fibroblasts contribute significantly to this process. Although it has been possible to examine isolated fibroblastic populations from normal vs. fibrotic lungs, analyses of the production of procollagen have been largely equivocal due in part to a) the heterogeneity of the cultures and b) a focus at the protein level which does not easily distinguish between synthesis and degradation. Accordingly, we have proposed a study of collagen gene regulation at both transcriptional and translational levels in fibroblasts from normal human lung as well as in freshly isolated subpopulations sorted from fibrotic lung biopsies. Using plasmids containing various regulatory elements of the human alpha1(I) collagen gene, we will examine the feedback regulatory effect of type I procollagen propeptides in type I collagen synthesis. By transfecting normal human lung fibroblasts in the presence of transforming growth factor-beta, a known stimulator of extracellular matrix (ECM) in vivo and in vitro, we will determine which regions of the alpha1(I) gene are responsible for transcriptional and translational activation of collagen synthesis. In fibrotic or TGF-beta-treated lung fibroblasts demonstrating high levels of type I procollagen synthesis, we will investigate coordinate regulation of type I and a novel collagen, FCL-1, which is known to be induced by ECM. The distribution of FCL-1 will be ascertained by immunofluorescence and in situ hybridization in normal and fibrotic lung, and its expression will be determined at both transcriptional and translational levels in cells derived from these tissues. These experiments, which directly address the regulatory properties of 2 collagen genes, should elucidate basic mechanisms of collagen production observed in fibrotic lung disease.
| Fouser, L; Sage, E H; Clark, J et al. (1991) Feedback regulation of collagen gene expression: a Trojan horse approach. Proc Natl Acad Sci U S A 88:10158-62 |
| Fouser, L; Iruela-Arispe, L; Bornstein, P et al. (1991) Transcriptional activity of the alpha 1(I)-collagen promoter is correlated with the formation of capillary-like structures by endothelial cells in vitro. J Biol Chem 266:18345-51 |
