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 gi ngival fibroblast progenitor cells in steady-state control and during susta ined mechanical Stimulation. Elastics (0.15 mm thick) were inserted between maxillary M1 and M2 of 8 wk-old male rats which were labelled with H-3-TdR and killed in groups of 6-7 animals together with equal-sized groups of la belled control animals at intervals between 1-168 h. Autoradiographs of con secutive mesio-distal sections were used to determine grain counts for H-3- 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 f or heavily-labelled and lightly-labelled paravascular cell populations and for labelled extravascular cells were 144, 76 and 50 h, respectively. Mecha nical stimulation caused a significantly faster rate of reduction of total grain counts relative to controls in all three cell populations and a decli ne of estimated MCC to 115, 50 and 21 h in heavily labelled and lightly lab elled paravascular cells and labelled extravascular cells, respectively. Th ese findings indicate that mechanical stimulation induces faster progressio n of gingival fibroblast progenitor cells through the cell cycle.