Idiopathic pulmonary fibrosis (IPF) comprises a heterogeneous group of lung disorders characterized by diffuse and often progressive lung fibrosis which can result in eventual respiratory failure. Despite intensive investigation on various aspects of IPF in man and the study of various animal models that mimick the human disease, the mechanisms responsible for the excessive accumulation of lung collagen in IPF have not been elucidated. In previous studies examining collagen biosynthesis in lung fibroblasts from patients with IPF we found that these cells exhibited biosynthetic heterogeneity when maintained in long term cultures. While certain cell lines displayed elevated rates of collagen production which were maintained for multiple generations, other produced excessive collagen only at early passage and returned towards normal values during subsequent sub-culturing. We propose the hypothesis that IPF exhibits pathogenetic heterogeneity regarding the mechanisms that result in the increased expression of collagen genes. We will utilize the extensive resources of molecular biology available to us to examine at the molecular level the validity of this hypothesis and to further understand the regulation of expression of collagen genes in normal and IPF lung fibroblasts. Specifically, we will examine intrinsic alterations in the regulation of Type I collagen gene expression by transient transfection experiments, examination of the chromatin structure in the 5' flanking region to the alpha 1 (I) collagen gene and identification of the transcriptional regulatory sequences in the human pro alpha 1 (I) gene; and to study the effects of three potent extrinsic modulatory factors (TGF beta, gamma IFN and TNF) on the expression of alpha 1 (I) collagen gene and its regulation. We have previously shown that these factors cause potent stimulation (TGF beta) and inhibition (gamma IFN and TNF) of fibroblast collagen production. The mechanisms of extrinsic modulation will be investigated by transient transfection with promoter constructs that have insertions or deletions and identification of putative DNA binding regions in collagen genes, and measurement of DNA binding proteins that may exert regulatory activity in these cells. Although we acknowledge that studying animal models or fibroblasts would be a simpler task, we have chosen to study the human disease encouraged by the availibility of powerful molecular probes for human collagen genes and of large numbers of IPF lung cell lines.
