Evidence That More Primitive Hematopoietic Progenitor Cells Are Concentrated within the CD133+Cell Compartment of Cord Blood.

We report the use of the in vitrocobblestone area-forming cell (CAFC) assay to investigate the hematopoietic progenitor cell (HPC) profile of pre-selection, post-selection positive (CD133+) and post-selection negative (CD133−) fractions of cord blood (CB). The CAFC assay provides a qualitative measure of the HPC contained within a given cell population at a given time-point. Briefly, CAFC give rise to cobblestone areas (CA) beneath a stromal cell layer that can be visualized by light microscopy at weekly intervals and their frequencies determined by the use of a limiting dilution strategy. CA that persist in culture for a relatively long period of time are considered to be derived from more primitive, potentially higher quality HPC than those that persist in culture for a shorter period of time. Using this approach, changes within the HPC compartment within a specific cell population can be quantified.