Regulation of fibroblast proliferation and collagen synthesis by cytokines

Fibroblasts are ubiquitous mesenchymal cells which synthesize collagen and other matrix macromolecules for the structural support of connective tissues. They are important in wound repair but also contribute connective tissue proteins to areas of chronic inflammation. In pathological processes such as hepatic cirrhosis, this may become deleterious to the host. Certain fibrotic diseases such as scleroderma and some forms of interstitial pneumonitis and interstitial nephritis are characterized by the presence of prominent mononuclear cell infiltrates. Studies in several laboratories have recently established that mononuclear cells produce soluble mediators capable of regulating several fibroblast functions including migration, proliferation and collagen synthesis. However, many of the studies on the immunoregulation of fibroblasts appear to present contradictory or mutually exclusive data. In this review Bruce Freundlich and his colleagues discuss the difficulties in identifying the factors that regulate fibroblast proliferation and collagen synthesis.