Keratinocyte growth factor stimulates the growth and activity of epithelial cells via the keratinocyte growth factor receptor. We have recently shown that the growth factor is markedly elevated in cyclosporin A-induced gingival hyperplasia tissue in vivo, but the effects of cyclosporin A on the receptor are not yet known. The present study was therefore carried out to determine whether expression of the keratinocyte growth factor receptor is up-regulated in gingival hyperplasia compared with normal gingiva. Using immunohistochemistry and the reverse-transcribed polymerase chain-reaction, we obtained results which showed that receptor antigen and gene transcript levels were both elevated in gingival hyperplasia tissue. In addition, flow cytometry and the reverse-transcribed polymerase chain-reaction showed that the receptor and mRNA were also higher in gingival epithelial cells following incubation with cyclosporin A in vitro. These findings suggest that the keratinocyte growth factor-receptor pathway of mesenchymal-epithelial interaction could play an important part in the molecular pathogenesis of gingival hyperplasia.
