In vitro identification of a subpopulation of fibroblasts that produces high levels of collagen in scleroderma patients.

A subpopulation of scleroderma dermal fibroblasts was identified by flow cytometric analysis. Between 15% and 25% of the cells within the scleroderma fibroblast lines had high levels of cytoplasmic granularity, as identified by side light scatter characteristics. Similar fibroblasts composed less than 3% of the cells within the normal fibroblast lines, although greater numbers could be induced through exposure to soluble factors derived from activated mononuclear cells. The granular subpopulation of fibroblasts produced 2-3 times as much procollagen as did the other fibroblasts. These data support the hypothesis that fibrosis in scleroderma may result in part from the activity of an inherently high procollagen-producing subset of normal fibroblasts that is expanded through exposure to immune cytokines.