Fig. 2. Apoptosis markers and cell cycle. Annexin V (early apoptotic) and annexin V-propidium iodide (PI; late apoptotic) positive cells after exposure to increasing concentrations (100, 250 μM) of ropivacaine for 24 h (A ). Cell cycle phases (G⁰/G¹, S, G²/M) of mesenchymal stem cells exposed to 100 and 250 μM ropivacaine for 24 h indicative of cell cycle arrest (B ). Expression patterns of the G¹phase regulatory proteins p16^INK4a, p27^Kip1, and proliferative cell nuclear antigen in whole cell lysates after exposure to increasing concentrations (100, 250 μM) of ropivacaine (C ). *Significantly different from CTL. #Significantly different from 100 μM. Data are mean (SD); n = 4 (A ) and n = 6 (B  and C ). CTL = control without treatment; PCNA = proliferative cell nuclear antigen; ROPI = ropivacaine.