The effect of basic fibroblast growth factor on cell cycle in human gingival fibroblasts from nifedipine responder and non-responder

Abstract

It has previously been demonstrated that gingival fibroblasts derived from nifedipine-reactive patients (nifedipine responders) show a greater cell proliferation rate than those from nifedipine non-reactive patients (nifedipine non-responders) in the presence of 1 microM nifedipine. The aim of the present study was to characterize cell cycle differences between nifedipine responder and non-responder fibroblast cells and determine the effect of basic fibroblast growth factor (bFGF) on cell cycle progression. Further, the effect of bFGF on cyclins A, B1, D1, E, and CDKs 1, 2, 4, 6 mRNA expression in responder and non-responder cells was investigated. A population of nifedipine responder cells underwent progression to S and G2/M phases from G0/G1 phase in the presence of 10% fetal calf serum or 10 ng/ml bFGF was greater than nifedipine non-responder cells. 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 nifedipine responder cells than non-responder cells. These results indicate that nifedipine responder cells may be more susceptible to growth factors such as bFGF with a resultant increase in expression of cyclins and CDKs in responder compared with non-responder cells.

Differences of Cell Growth and Cell Cycle Regulators Induced by Basic Fibroblast Growth Factor Between Nifedipine Responders and Non-responders

“…In this study, we examined the effect of bFGF on cell cycle in NIFr and NIFn cells by flow cytometric DNA analysis after bromodeoxyuridine (BrdU, is incorporated into newly synthesized DNA by cells entering and progressing through the S phase of the cell cycle) incorporation. The present result, demonstrating that the proportion of NIFr cells that had undergone the G 1 / S transition in the presence of bFGF significantly increased compared to that in NIFn cells agreed with our previous results (22).…”

“…This figure is a representative data out of four trials. previous study, it was indicated that the proportion of NIFr cells that had undergone progression to the S and G 2 / M phases from the G 0 / G 1 phase in the presence of bFGF was greater than that of NIFn cells (22). However, in the previous study, the S phase cells were not measured precisely, being calculated between the G 0 / G 1 and G 2 / M peaks in the DNA histogram.…”

“…In the previous study, no differences in CDK4 and CDK6 mRNA expressions by bFGF in NIFr and NIFn cells were shown (22). Cyclin D1-CDK4 efficiently phospho- rylates the ser780 in pRB, while cyclins E-CDK2 and A-CDK2 do not (32 In the presence of bFGF, because cyclin E protein levels increase more in NIFr than NIFn cells and pCDK2 and pRB (Ser807/ 811) protein levels in NIFr cells were higher than those in NIFn cells, the portion of G 1 / S transition in NIFr cells was greater than that in NIFn cells.…”

“…The activity of these enzymes is regulated by several mechanisms such as association with regulatory subunits (cyclins), phosphorylation, and de-phosphorylation (20,21). We have reported that the proportion of NIFr that had undergone progression to the -S and G 2 / M phases from the G 0 / G 1 phase in the presence of 10% fetal calf serum (FCS) and 10 ng/ ml bFGF was greater than that of NIFn, and also that expressions of mRNAs for cyclins A; B1; D1; E; and CDKs 1, 2, 4, and 6 were greater in NIFr than NIFn in the presence of bFGF (22).…”

“…Cells (5 × 10 5 ) were seeded into 100 mmφ × 20 mm high dish in DMEM-10 for 48 h and then quiescence was induced for 24 h in DMEM-0.5 (22). Cells were stimulated to reenter the cell cycle by adding fresh medium containing 0.5% FCS and 10 ng / ml bFGF, and incubated for 6,12,18,24,30,36,42, and 48 h. Total cellular proteins were extracted from cells at each incubation period with Tris SDS β-Me sample buffer (Daiichi Pure Chemicals Co., Tokyo).…”