Cell kinetics of mechanically stimulated rat oral epithelia

Objective: To study cell kinetics of rat gingival (GE), sulcular (SE) and junctional (JE) epithelia in the steady-state and after application of mechanical pressure. Design: Elastic bands were inserted between first and second maxillary molars of 8-week-old male rats, which were labelled with H ³ TdR and killed in groups of six to seven animals together with equal-sized groups of labelled control animals at intervals between 1 and 168 h. Autoradiographs were used to determine epithelial cell proliferation on the pressure side of M1 by calculating the percentage of ³H TdR-labelled cells (PLC) in the basal (BL) and suprabasal (SL) layers of GE, SE and JE and to estimate median cell cycle (MCC) duration of BL cells by plotting mean and median grain counts against time. Results: ³H TdR-labelled cells were present in SL of SE and JE 1-12 h after isotope injection suggesting that the BL might be not the only source of progenitor cells for JE as they might also be derived through migration from adjacent SE. Application of pressure significantly (ANOVA, P < 0.05) reduced PLC in BL of GE, SE and JE indicating a decrease of cell proliferation after 1-12 h in response to pressure. In steady-state, the MCC durations of BL cells of GE, SE and JE were 39, 14 and 9 h, respectively. After application of pressure, they increased significantly (χ²-test, P < 0.05) to 48, 44 and 34 h, respectively. Conclusions: Sustained pressure may lead to reduction of proliferative activity of these epithelia inducing slower progression of progenitor cells through the cell cycle.