Increased levels of transforming growth factor beta receptor type I and up-regulation of matrix gene program - A model of scleroderma

Objective. Previously published studies have demonstrated that a majority of systemic sclerosis (SSc) fibroblasts exhibit elevated levels of transforming growth factor 0 type I receptor (TGF beta RI). An experimental model that recapitulates this condition was established in control dermal fibroblasts by titrating the dose of adenovirus vector expressing TGF beta RI (AdTGF beta RI). The present study was undertaken to determine the functional consequences of increased levels of, TGF beta RI in SSc. Methods. Gene array analysis of control dermal fibroblasts transduced with AdTGF beta RI was performed using GeneChip expression arrays. Gene validation was done by Northern blot, quantitative reverse transcriptase-polymerase chain reaction, and Western blot techniques. TGF beta blockade was performed using soluble TGF beta receptor. TGF beta RI kinase/activin receptor-like kinase 5 was inhibited with pharmacologic inhibitors. TGF beta RI and TGF beta RII protein levels and collagen production were examined by Western blotting in primary dermal fibroblasts from 9 SSc patients and 9 healthy adults. Endogenous TGF beta RI levels were suppressed in control and SSc fibroblasts using specific small interfering RNA (siRNA). Results. Global gene analysis indicated that a 2-fold increase in TGF beta RI levels in control fibroblasts resulted in profibrotic changes that closely resembled the phenotype of SSc fibroblasts. A total of 125 genes were up-regulated, including COL1A1, COL1A2, and connective tissue growth factor, and 206 genes were down-regulated. Elevated production of collagen in cells transduced with AdTGF beta RI was dependent on the autocrine TGF beta, but not TGF beta RI kinase activity. Eight of the 9 SSc strains exhibited increased levels of TGF beta RI protein, which correlated with increased collagen synthesis. Treatment of SSc and matched control fibroblasts with siRNA that normalizes TGF beta RI levels reverted collagen protein production in SSc fibroblasts to the levels observed in control fibroblasts. Conclusion. Our findings demonstrate that aberrantly expressed TGF beta RI may drive an autocrine loop involved in the up-regulation of collagen and other matrix-related genes in SSc fibroblasts.