Altered collagen metabolism in nifedipine-induced gingival overgrowth

Fibroblasts from nifedipine-induced fibrotic gingiva (NFG) have been characterized with respect to several cellular functions which could contribute to the characteristic clinical overgrowth of the gingiva: collagen synthesis and breakdown, glycosaminoglycan production, fibronectin synthesis, and proliferation. Histologic examination of NFG tissue revealed a hyperplastic epithelium with elongated, branched rete pegs. The connective tissue consisted of densely-packed collagen fibers and numerous enlarged fibroblasts, as well as regions of thinner, disorganized collagen fibers in the vicinity of scattered inflammatory and mast cells. Results of in vitro experiments showed that the fibroblast strains from the fibrotic gingiva (NFG) produced significantly greater amounts of collagen and lower levels of collagenase activity when compared to age- and sex-matched normal human gingival fibroblast strains. The NFG fibroblasts did not produce significantly greater amounts of fibronectin, and their level of glycosaminoglycan production was less than that of the normal fibroblasts. The NFG fibroblasts did not proliferate significantly more rapidly than the normal fibroblast strains. These findings therefore show that there are defects in the regulation of collagen production by NFG fibroblasts in vitro, and suggest that these alterations in collagen metabolism contribute to the over-deposition of collagen in this tissue, rather than hyperproliferation of the fibroblasts or through the production of increased amounts of fibronectin and glycosaminoglycans.