A functional hierarchy among the CD34+ hematopoietic cells based on in vitro proliferative and differentiative potential of AC133+ CD34bright and AC133dim/-CD34+ human cord blood cells

The 5-transmembrane receptor AC133 is expressed on a subpopulation of human hematopoietic cells that includes the CD34bright cells. We evaluated the developmental potential of AC133+CD34bright and AC133dim/-CD34+ cells isolated from 5 cord blood (CB) samples by studying the in vitro proliferative and differentiative potential of each population in both progenitor and mature cell expansion cultures. Seven-day culture of AC133+CD34bright cells with a cytokine combination favoring primitive progenitor cells causes a significant increase in CD34+, CFU-C and noncycling stem/progenitor cells HPP-Q (High Proliferative Potential-Quiescent), whereas culture of AC133dim/-CD34+ cells shows a limited increase in committed progenitor cells only. HPP-Q cells were not found in freshly isolated AC133dim/-CD34+ nor in expanded CD34+ cells derived from AC133dim/-CD34+ cells. No statistically significant difference was observed between the 1-week expanded AC133+ and the initial AC133+CD34bright cells regarding their clonoge...