OBJECTIVETo explore the endothelial progenitor cell markers and biological characteristics of human CD133 umbilical cord blood cells( EPC).

METHODSCD133+ cells were enriched from human umbilical cord blood by immunomagnetic sorting, and cultured with EGM-2MV medium containing epidermal growth factor, vascular endothelial growth factor and fibroblast growth factor 2. The percentage of CD133+ cells in cord blood monocytes, the growth curve and growth characteristics of primary EPCs were measured by flow cytometry and immunochemistry method. Weibel-Palade body was observed with transmission electron microscope. The mixture of EPCs and human stomach cancer cell line GC7901 were injected into athymic mice to observe the tumor growth and vascularization.

RESULTSThe percentage of CD133+ cells in cord blood monocytes was 0.91%, and after sorting, the percentage of CD133+ cells was raised to 85.52%. The cultured cells showed a typical spindle-shaped morphology in 3 post-culture days (PCD) and areas of clusters of cobblestone-like cells in 10 PCD. The number of EPC increased from 7 PCD on, peaked on 17 PCD. Obvious amplification and clone-like growth on 7 PCD were observed by light microscope. Typical Weibel-Palade body was observed in the cells under transmission electron microscope. Tumor forming experiment in athymic mice showed that the tumor size of EPC group was larger than that of control with smaller necrosis area and more and larger blood vessels. Immuno-fluorescent staining showed many human vWF antigen-positive endothelial cells being involved in the tumor vascularization.

CONCLUSIONImmunomagnetic sorting can efficiently enrich EPC from human umbilical cord blood. Our data support that the EPC may contribute to angiogenesis, speed up vascularization of ischemic tissue.