Figure 3. Calcium oscillations triggered by the PMS depend on calcium entry via the plasma membrane, cytoskeleton and actomyosin contractility.

(A) PMS evokes calcium oscillations in a subpopulation of hMSCs without spontaneous activities (Ctr; control). (B, C) PMS-induced calcium oscillations were inhibited in GdCl₃- or BAPTA-pretreated cells, suggesting the involvement of calcium entry at the plasma membrane. (D, E, F) PMS-induced calcium oscillations were also inhibited in CytoD-, Noc-, or ML-7 pretreated cells, suggesting the involvement of cytoskeleton and actomyosin contractility in the PMS-induced calcium oscillations. Amplitude (G) and frequency (H) of PMS-induced calcium oscillations are inhibited in the presence of inhibitors. PMS, control group with prolonged mechanical stretch only (n = 9); PMS+GdCl₃ (5 µM), an inhibitor of stretch-activated calcium channel was applied 1 hr before stretch (n = 4); PMS+BAPTA (20 µM in the calcium free medium), a calcium chelator was applied before stretch (n = 5); PMS+CytoD (1 µM), an inhibitor of actin filament was applied 1 hr before stretch (n = 5); PMS+Noc (5 µM), an inhibitor of microtubule was applied 1 hr before stretch (n = 4); PMS+ML-7 (10 µM), an inhibitor of MLCK was applied 1 hr before stretch (n = 4). * indicates statistically significant difference from all other groups by the Bonferroni multiple comparison test with p<0.05.