Abstract

Activated fibroblasts were derived from the skin of patients with systemic scleroderma (SSc), used as a model for fibrosis. Such cells are characterized by increased production of collagens and other matrix constituents. Increased collagen and fibronectin production has been correlated with similarly elevated mRNA steady-state levels. In the present study we analysed the contribution of transcriptional activity and post-transcriptional transcript stability to the increases in pro-alpha 1(I) collagen and fibronectin mRNA steady-state levels in activated (scleroderma) fibroblasts. Fibroblasts, when cultured in close contact with a three-dimensional collagenous matrix, down-regulate collagen synthesis. Culture of skin fibroblasts from two patients with SSc in three-dimensional collagen lattices, however, showed 4-fold elevated pro-alpha 1(I) collagen mRNA levels over fibroblasts from healthy donors. Transcription of the COL1A1 gene in SSc fibroblasts was induced 2-3-fold over that in controls in both monolayer and lattice cultures, accounting in part for the elevated steady-state level. A 50% decrease in transcription rate in lattice compared with monolayer culture occurred, as in control cells. In contrast, whereas control cells in lattices responded with decreased (50%) pro-alpha 1(I) collagen mRNA stability, in SSc cells these transcripts were found to be more stable (half-life of 5 h compared with 2 h in control cells). Fibronectin steady-state mRNA levels, in contrast, were not significantly regulated by the three-dimensional environment. In SSc fibroblasts, fibronectin mRNA levels were induced 1.5-4.9-fold over controls. In part, this increase appears to be due to elevated transcription, and an increase in fibronectin transcript stability was also detected. We therefore conclude that activated fibroblasts such as those derived from scleroderma patients utilize transcriptional and posttranscriptional mechanisms to maintain increased collagen and fibronectin production, which contribute to the pathogenesis of the disease.