OBJECTIVETo study the role of the feeder layer cells as niche in the process of expansion of late endothelial progenitor cell in vitro.

METHODSWe cultured mononuclear cells (MNC)from human peripheral blood (PB)on the plate with the feeder layer cells which were irradiated late endothelial progenitor cells(EPC)or human umbilical vein endothelial cells (HUVEC) by EGM-2. After 21 days, the numbers of obtained late EPC colonies were counted separately, and their surface antigen of the late EPC was verified by fluorescence-activated cell sorter (FACS) analysis, and their ability of forming vessel structure with Matrigel in vitro. The differentiation of single stem cell on the feeder layer cell was traced by video-microscopy.

RESULTSAfter 21 days of culture,(40.0±3.9)and(39.3±3.1)late EPC colonies that MNC of a hundred milliliter PB were cultured, respectively, on the feeder layer cells of EPC and HUVEC were much more than (2.0±1.3) colonies cultured on without the feeder layer cells (all P <0.05). These cells also expressed CD31,CD34,eNOS,FLt-1,P1H12,Sendo,VE cadherin,and CD117, as shown by FACS analysis. Furthermore, they formed vessel structure with Matrigel in vitro. The video-microscopy showed the asymmetric cell division was participated by the feeder layer cell during the expansion of single stem cell.

CONCLUSIONThe massive expansion of late EPC can be achieved by the provision of the feeder layer cells, which may be involved in the stem cell asymmetric cell division.