Angiopoietin-1 Supports SRC Activity Acquisition of Human CD34-Bone Marrow Cells.

Abstract

CD34 negative hematopoietic stem cells (CD34− HSCs) were identified in mice and humans. Human HSCs are evaluated as severe combined immunodeficient mouse (SCID)-repopulating cells (SRCs), originally identified by the ability to reconstitute hematopoiesis in nonobese diabetic (NOD)/SCID mouse. CD34− cord blood (CB) cells have been hard to engraft in NOD/SCID mice until recent report of successlul engraftment by intra-bone marrow transplantation (iBMT). However, CD34− bone marrow (BM) cells have not been analyzed precisely. We prepared lineage negative CD34 negative (Lin-CD34−) cells by negative selection using CD2,3,7,14,16,19,20,33,34,36,41,56,127, and GlyA antibody. Lin-CD34− BM cells did not engraft in NOD/SCID mice even by using iBMT (0/6). In the previous study, we reported that Lin-CD34− BM cells were able to differentiate into CD34+ cells accompanied by the emergence of colony forming activity after 7 days of stroma-dependent culture, while SRC activity was not detected. (BMT 28, 587–595, 2001) Here we cultured Lin-CD34− BM cells on stroma cells transfected with human angiopoietin-1 cDNA (AHESS-5), since we detected Tie-2 expression on Lin-CD34− BM cells. AHESS-5 supported induction of CD34 much better than HESS-5 cells or empty vector transfected control cells (EVHESS-5), and the effect was blocked by anti-Tie-2 antibody (Fig.1). Furtheremore, CD34+ cells produced from CD34− BM cells engrafted in NOD/SCID mice (11/12). As previously reported, CD34− CB cells differentiate CD34+ cells and acquire SRC activity by stroma-dependent culture without angiopoietin-1. These results highlighted the characteristic differences of CD34− HSCs of BM from CB and the unique role of BM niche for CD34− HSCs. [Display omitted]