Ex Vivo Expansion of Human Umbilical Cord Blood CD34+ Cells in a Collagen Bead—Containing 3-Dimensional Culture System

Self-renewal of stem cells depends on several critical factors, including the hematopoietic microenvironment, interactions with supporting stromal cells, features of the extracellular matrix, hematopoietic growth factors, and cytokines. Our study investigated the role of artificial 3-dimensional microenvironments as a means of replicating a more physiologic milieu in expansion of cord blood CD34+ cells. In the 3-dimensional model, hematopoietic cells inside collagen beads are exposed to cytokines added to a culture medium. We found that amplification of CD34+ cells with a clonogenic assay, fluorescenceactivated cell sorter analysis, and bone marrow repopulation of NOD/SCID mice showed greater clonogenic ability of cells cultured by the 3-dimensional method compared with the 2-dimensional method. The present study demonstrated that 3-dimensional matrix support may be useful for extended periods in expansion and preservation of stem cells or progenitor cells in vitro.