Effects of mechanical stimulation on cell cycle duration in rat gingival fibroblast progenitor cells

The aim of this investigation was to estimate cell cycle duration in rat gingival fibroblast progenitor cells in steady-state control and during sustained mechanical stimulation. Elastics (0.15 mm thick) were inserted between maxillary M1 and M2 of 8 wk-old male rats which were labelled with H3-TdR and killed in groups of 6-7 animals together with equal-sized groups of labelled control animals at intervals between 1-168 h. Autoradiographs of consecutive mesio-distal sections were used to determine grain counts for H3-TdR-labelled cells in the connective tissue of the gingival papilla between M2 and M3. Median cell cycle times (MCC) were estimated from plots of mean and median grain counts against time. Under steady-state conditions, MCC for heavily-labelled and lightly-labelled paravascular cell populations and for labelled extravascular cells were 144, 76 and 50 h, respectively. Mechanical stimulation caused a significantly faster rate of reduction of total grain counts relative to controls in all three cell populations and a decline of estimated MCC to 115, 50 and 21 h in heavily labelled and lightly labelled paravascular cells and labelled extravascular cells, respectively. These findings indicate that mechanical stimulation induces faster progression of gingival fibroblast progenitor cells through the cell cycle.