Abstract
Background
CD133 is a newly developed hematopoietic stem cell marker but little is known about its function. Whether CD133+ cell selection provides any advantage over CD34+ selection for hematopoietic stem cell isolation and transplantation is unclear. The present study compared colony formation and endothelial cell differentiation of these two cell types from umbilical cord blood (UCB).
Methods
Mononuclear cells from the same UCB samples were used for both CD133+ and CD34+ cell selection. Cells with 97.1% purity were incubated in semi-solid culture medium containing stem cell growth factor (SCGF) and G-CSF or erythropoietin (EPO). Purified cells were also cultured in M199 containing vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), and insulin-like growth factor-1 (IGF-1).
Results
CD34+ and CD133+ cells produced similar numbers of CFU-GM colonies (median 43.25 and 30.5, respectively; P>0.2). However, a greater than four-fold difference in BFU-E colony formation was observed from CD34+ cells compared with CD133+ cells (median 35 and 8, respectively; P<0.04). CD34+ cells gave rise to endothelial-like cells when stimulated with VEGF, bFGF and IGF-1. CD133+ cells were unable produce this cell type under the same conditions.
Discussion
CD133+ cells produced smaller BFU-E colonies and were unable to differentiate into mature endothelial cells. CD34+ cells contained endothelial progenitors that could differentiate into mature cells of this lineage. Based on these data, it appears that CD133 offers no distinct advantage over CD34 as a selective marker for immunoaffinity-based isolation of hematopoietic stem cells and endothelial progenitor cells.