Cell Growth and Cell Cycle in Nifedipine-Reactive Human Gingival Fibroblasts

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The objective of the present study was to characterize the differences in cell cycle between nifedipine responder (NIFr) and non-responder (NIFn) gingival fibroblasts. The progression of S and G2/M phases in NIFr was greater than those in NIFn in the presence of 10% fetal calf serum. NIFn cells possessed more p38 MAPK activity in resting state and more sensitive to NIF in expression of p38 MAPK. The percentage of ATF-2 phosphorylation treated by Anisomysin or IBMX (3-isobutyl-1-methylxanthine) in NIFn cells was greater than those in NIFr cells. Since p38 MAPK, that might exist and play an important role on the depression of cell cycle progression, these results suggest NIFn cells have less mitotic activity than NIFr cells. Thus, fibroblasts in NIFn might be depressed cell cycle progression resulting in lesser amount of fibroblasts present in gingival tissue. Nifedipine (NIF) did not alter any change on mRNA expression of cyclins A, B1, D1, E in both of NIFr and NIFn. However, a greater number of NIFr than NIFn cells underwent progression to S and G2/M phases from G0/G1 phase in the presence of basic fibroblast growth factor (bFGF). mRNA expression of cyclins A, B1, D1, E and CDKs 1, 2, 4, 6 in the presence of 10 ng/ml bFGF was generally greater in NIFr cells than NIFn cells. These results indicate that NIFr cells may be more susceptible to growth factors such as bFGF with a resultant increase in expression of cyclins and CDKs in NIFr cells compared with NIFn cells.