Diphenylhydantoin (dilantin) gingival hyperplasia: drug-induced abnormality of connective tissue

Confirmation that neither phenotype nor hydroxylation of collagen is altered in overgrown gingiva from diphenylhydantoin-treated patients

Collagens, solubilized by pepsin-digestion of diphenylhydantoin-induced overgrown gingiva, appeared similar to collagens solubilized from inflamed gingiva with regard to: ratio of type I to type III collagen, ratio of alpha1 to alpha2 of type I collagen, and degree of hydroxylation of type I collagen.

Morphological features and functional properties of human fibroblasts exposed to Actinomyces viscosus substances

Connective tissue fibroblasts undergo cytopathic degenerative changes during certain long-term inflammatory diseases such as rheumatoid arthritis and periodontitis. The failure of inflamed tissues to repair properly may result from functional alterations of fibroblasts within the affected tissues. Numerous previous studies indicate that direct cytotoxicity by bacterial or other substances may be responsible for the cellular alterations observed in vivo. We have tested this hypothesis by exposing cultures of human diploid fibroblasts to homogenates of Actinomyces viscosus (a microorganism associated with periodontitis and capable of causing other chronic inflammatory diseases) and analyzing the effects on cell viability, morphology, and function. The cells bind and subsequently engulf relatively large quantities of the bacterial substances. These substances do not appear to be toxic to fibroblasts as determined by 51Cr release and microcytotoxicity assays, although there is a slight but significant decrease in protein synthesis (P less than 0.01) as measured by the incorporation of [14C]proline. However, collagen production was not altered, and the cytopathic alterations observed in diseased tissues in vivo did not occur in the exposed cells. These findings suggest that A. viscosus substances do not directly cause injury to connective tissue fibroblasts in periodontal disease but may, through cell-surface binding, mark these cells for subsequent immune-mediated damage.

The effect of diphenylhydantoin on fibroblasts in vitro

It was found that 0.02 mM was the higher concentration of drug which is not toxic and is compatible with normal cell morphology and growth over a period of a week. Using this concentration of drug there was no consistent stimulation of cell growth. A small increase in cell number was noted, however, in some cultures during the first 24 hours of culture. DpH at a concentration of 0.02 mM in the presence of ascorbic acid decreased collagen prolyl hydroxylation in "old" W1-38 cultures but a concentration of 0.1 mM was required to decrease the values to a similar extent in "young" cultures. A concentration of 0.02 mM DpH had no effect on hydroxylation in an "old" HGF culture. It is speculated that in a responsive individual a reduction of collagen prolyl hydroxylation may play a role in the etiology of DpH-induced gingival enlargement and congenital malformations.

Fibroblast heterogeneity and prostaglandin regulation of subpopulations

The effects of prostaglandin E(2) (PGE(2)) upon the synthesis of protein and DNA, and membrane transport of proline and thymidine, by human diploid fibroblasts were studied. At a concentration range of 1-10 muM, PGE(2) inhibited protein synthesis and membrane transport by 45-50%. Serum-activated DNA synthesis and thymidine transport were also inhibited by approximately 50% in cells made quiescent and synchronous by serum deprivation. To determine whether prostaglandin inhibits some of the cells completely or all of the cells partially, radioautographic and cell-counting experiments were done. In cultures pulse-labeled with [(3)H]thymidine 12-33 hr after serum activation, prostaglandin exposure reduced the number of labeled nuclei by 42%. Sixty-five hours after serum activation, the total cell numbers present in the PGE(2)-exposed cultures were reduced by 25%. Furthermore, in the fibroblast cultures derived from cells previously maintained in 10 muM PGE(2) for 14 days, PGE(2) had no effect on DNA synthesis, indicating that the PGE(2)-sensitive cells had disappeared from the cultures. Thus, PGE(2) appears to inhibit growth and synthesis of a subpopulation of cells while not affecting the remaining insensitive cells. Prostaglandins may play an important role in connective-tissue differentiation and in some pathologic alterations by regulating fibroblast subpopulations.