Experimental approaches to derive CD34+ progenitors from human and nonhuman primate embryonic stem cells.

Traditionally, CD34 positive cells are predominantly found in the umbilical cord and bone marrow, thus are considered as hematopoietic progenitors. Increasing evidence has suggested that the CD34+ cells represent a distinct subset of cells with enhanced progenitor activity; CD34 is a general marker of progenitor cells in a variety of cell types. Because the CD34 protein shows expression early on in hematopoietic and vascular-associated tissues, CD34+ cells have enormous potential as cellular agents for research and for clinical cell transplantation. Directed differentiation of embryonic stem cells will give rise to an inexhaustible supply of CD34+ cells, creating an exciting approach for biomedical research and for regenerative medicine. Here, we review the main methods that have been published for the derivation of CD34+ cells from embryonic stem cells; specifically those approaches the human and nonhuman primate stem cells. We summarize current status of this field, compare the methods used, and evaluate the issues in translating the bench science to bedside therapy.