Cell cycle analysis and Ki-67 expression in TG1 and OB1 GSCs under different <i>in vitro</i> culture conditions.

<p>(A) TG1 (upper panel) and OB1 (lower panel) GSCs maintained in culture for 1, 9 and 14 days without medium renewal (d1, d9, d14, respectively) or cells obtained after 9 days without medium renewal and subjected to freshly prepared culture medium for 5 days (Q+5) were permeabilized and stained with anti-Ki-67 antibodies conjugated to FITC and propidium iodide (PI). (B-E) Histograms represent the percentage of TG1 (B, C) and OB1 (D, E) cells present in the G1, S, G2/M phases of the cell cycle as well as the percentage of quiescent cells in G0 and of cells showing DNA fragmentation (sub-G1). Cells in the G2/M phase were further distinguished as a function of the Ki-67 proliferation marker expression levels (G2/M high Ki-67 and G2/M low Ki-67). Analysis was performed on cells maintained for 1–14 days without medium renewal (B, D for TG1 and OB1 cells, respectively) or on cells left without medium renewal for 9 days (Q) and re-introduced into freshly prepared culture medium for 1 (Q+1), 2 (Q+2), 3 (Q+3), 4 (Q+4) or 5 (Q+5) days (C, E for TG1 and OB1 cells, respectively).