Abstract: Objective To study the mechanisms underlying high collagen synthesis of systemic sclerosis skin fibroblasts. Methods The mRNA expression levels of procollagen alpha 1 type 1 （COL1A1） were detected by in situ hybridization to select heterogeneic fibroblast clones, and monoclonal fibroblasts were divided into three groups according to their mRNA levels of COL1A1. Meanwhile, five deletion constructs containing portions of human procollagen gene promoter were ligated into plasmids and used to transfect the three groups of fibroblast clones. The transcription of COL1A1 in these fibroblasts was assessed by transient transfection and luciferase assay. Results Fibroblast clones from both patients and normal controls showed a heterogeneity in the mRNA expression of COL1A1. Patients with systemic sclerosis had a larger proportion of fibroblasts expressing high level of COL1A1mRNA than did normal controls （50% vs 12.5%）. A significant increase was also observed in the mean mRNA levels of COL1A1 in fibroblast clones from patients with systemic sclerosis compared with those from normal controls （6.64 ± 2.48 vs 3.69 ± 2.01, t = 3.690, P < 0.01）. Maximal transcriptional activity was observed with a construct containing COL1A1 promoter from -174 bp to +42 bp in all fibroblast clones. The activities of COL1A1 promoter positively correlated with the mRNA levels of this gene. Conclusions COL1A1 gene might be activated at the transcriptional level in systemic sclerosis fibroblast clones with a high rate of collagen synthesis.

Key words: fibroblasts