OBJECTIVETo study the characteristics of cell cycle and proliferation of CD34+ hematopoietic stem cells in patients with myelodysplastic syndromes (MDS).

METHODSPropidium iodide staining was used to examine cell cycle parameters (G(0)/G(1), S and G(2)/M) of bone marrow mononuclear cells (BMMNCs) while immunofluorescent double staining and FACS techniques were used to measure Ki67 expression in BM CD34+ cells from normal control, patients with MDS, acute myeloid leukemia preceded by MDS (MDS-AML) and primary AML.

RESULTSThere was a statistical up-tendency in G(0)/G(1) phase proportion of BMMNCs whereas a statistical down-tendency in S and G(2)/M phase proportions among normal control, MDS and primary AML. Compared to primary AML, MDS-AML had significantly higher ratios of S (P < 0.05), G(2)/M (P < 0.05) and S + G(2)/M (P < 0.05) phase cells while lower ratio of G(0)/G(1) phase cells (P < 0.05). The proportion of CD34+Ki67+ cells in MDS patients was significantly higher than that in normal control (P = 0.004). So were the percentages of CD34+Ki67+ cells in low-risk [(0.54 +/- 0.49)%, P < 0.05] and high-risk MDS patients [(1.69 +/- 1.66)%, P = 0.022]. Furthermore, there was statistical difference between low-risk and high-risk MDS (P < 0.05). Compared to normal control and primary AML, MDS-patients had the highest proportion of CD34+Ki67+ cells [(16.75 +/- 13.58)%, P < 0.05]. The proportion of CD34+Ki67+ cells in CD34+ cells in MDS patients [(48.50 +/- 20.49)%] was significantly higher than that in normal control [(27.71 +/- 16.04)%, P < 0.01]. So were the low-risk [(51.85 +/- 21.80)%, P = 0.002] and high-risk MDS [(43.93 +/- 18.57)%, P < 0.05]. The proportion of CD34+Ki67+ cells in CD34+ cells in MDS-AML patients [(60.92 +/- 30.12)%] was the highest, and was statistically higher than that in both normal control (P < 0.01) and primary AML patients [(17.01 +/- 15.93)%, P < 0.001]. The proportion of CD34+Ki67+ cells in Ki67+ cells in MDS patients [(4.91 +/- 4.68)%, P < 0.01] was significantly higher than that [(2.43 +/- 2.37)%] in normal controls. In the low-risk MDS group it was (4.11 +/- 3.94)%, (P > 0.05) and in high-risk MDS group it was (5.76 +/- 5.38)%, (P < 0.05).

CONCLUSIONHigh proportion of G(0)/G(1) cells and G(1) phase arrest occurred in MDS. High proliferation capacity of MDS clone, especially that derived from CD34+ cells, might play an important role in the clonal expansion, diseases deterioration and worse prognosis of MDS.