Objective   To investigate the effect of endothelial progenitor cells (EPCs) on the growth of C6 glioma cells in vitro.    Methods   EPCs were obtained from the spleen of healthy SD rats with density gradient centrifugation and adherence screening. The obtained EPCs were identified through morphologic characteristics

specificity to DiI-acLDL uptaking and Lectin binding

and positive expressions of CD34 and CD31 by immunofluorescence assay. The EPCs-conditional medium was added into the convention medium of C6 glioma cells to assess its effect on the proliferation of glioma cells. After cultured for 36 or 48 h with the EPCs-conditional medium or conventional medium (control)

MTT assay was employed to measure the cell proliferation and flow cytometry was used to detect the cell cycle.    Results   In 10 d after culture

the attached cells presented a “line-like” structure

and the adherent cells were double positive to DiI-acLDL uptaking and FITC-UEA-1 binding by direct flourescence staining under a laser scanning confocal microscope. Those cells were differentiated EPCs

and expressed wholly expressed CD34 and CD31. MTT assay showed that the OD value of each group at both the 2 time points were increased with the increasing of EPCs content in conditioned medium. The OD value of the group containing 50% of EPCs conditional medium of 36 h(2.018±0.220) and 48 h (2.388±0.448) was markedly higher than those of the control group (1.163±0.103

1.106±0.174) with significant difference (P0.01). The results of flow cytometry showed that the multiplication of experimental group is higher than control ones [(34.650±1.492)% vs (29.587±2.504)%

P＜0.05].    Conclusion   The EPCs can promote the proliferation of the C6 glioma cells in vitro

which may be through various angiogenic cytokines secreted by the cells.