Hereditary gingival fibromatosis (HGF) is a fibrotic enlargement of the gingiva. HGF gingiva contains large amounts of collagen and other extracellular matrix (ECM) molecules. In vitro, HGF fibroblasts produce greater amounts of the ECM components fibronectin (FN) and type 1 collagen than normal human gingival (GN) fibroblasts. Transforming growth factor beta (TGF beta) is a cytokine important in regulating tissue repair and regeneration after injury, and stimulating fibroblast proliferation and the production of FN and collagens. The objective of this study was to determine whether HGF fibroblasts produce TGF beta and, with the use of neutralizing antibodies to TGF beta isoforms, if their increased expression of FN and type 1 collagen is under autocrine TGF beta control. The HGF strains produced greater amounts of TGF beta1 and TGF beta2 (P < or = 0.003) as well as FN (P < or = 0.04) and type 1 collagen (P < or = 0.03) (measured by specific ELISA) than the GN strains. Treatment of HGF fibroblasts with anti-TGF beta1, beta2, or beta3, as well as a combination of all 3 antibodies, decreased their FN production by up to 60% (P < or = 0.04), and was able to decrease FN production by HGF fibroblasts to the levels of the GN fibroblasts. When used alone, the neutralizing antibodies decreased type 1 collagen production by the HGF fibroblasts by up to 40% (P = 0.014), and treatment with all 3 antibodies caused decreases of up to 55% (P = 0.0005). The results suggest that autocrine stimulation by the increased amounts of TGF beta isoforms made by HGF fibroblasts contributes to their increased production of FN and type 1 collagen.