Angiotensin-converting enzyme (CD143) marks hematopoietic stem cells in human embryonic, fetal, and adult hematopoietic tissues

Previous studies revealed that mAb BB9 reacts with a subset of CD34(+) human BM cells with hematopoietic stem cell (HSC) characteristics. Here we map B89 expression throughout hernatopoietic development and show that the earliest definitive HSCs that arise at the ventral wall of the aorta and surrounding endothelial cells are BB9(+). Thereafter, BB9 is expressed by primitive hernatopoietic cells in fetal liver and in umbilical cord blood (UCB). BB9(+)CD34(+) UCB cells transplanted into nonobese diabetic/severe combined immunodeficient (NOD/SCID) mice contribute 10-fold higher numbers of multilineage blood cells than their CD34(+)BB9(-) counterparts and contain a significantly higher incidence of SCID-repopulating cells than the unfractionated CD34(+) population. Protein microsequencing of the 160-kDa band corresponding to the BB9 protein established its identity as that of somatic anglotensin-converting enzyme (ACE). Although the role of ACE on human HSCs remains to be determined, these studies designate ACE as a hitherto unrecognized marker of human HSCs throughout hematopoietic ontogeny and adulthood

Differentiation of human embryonic stem cells to HOXA+ hemogenic vasculature that resembles the aorta-gonad-mesonephros

The ability to generate hematopoietic stem cells from human pluripotent cells would enable many biomedical applications. We find that hematopoietic CD34+ cells in spin embryoid bodies derived from human embryonic stem cells (hESCs) lack HOXA expression compared with repopulation-competent human cord blood CD34+ cells, indicating incorrect mesoderm patterning. Using reporter hESC lines to track the endothelial (SOX17) to hematopoietic (RUNX1C) transition that occurs in development, we show that simultaneous modulation of WNT and ACTIVIN signaling yields CD34+ hematopoietic cells with HOXA expression that more closely resembles that of cord blood. The cultures generate a network of aorta-like SOX17+ vessels from which RUNX1C+ blood cells emerge, similar to hematopoiesis in the aorta-gonad-mesonephros (AGM). Nascent CD34+ hematopoietic cells and corresponding cells sorted from human AGM show similar expression of cell surface receptors, signaling molecules and transcription factors. Our findings provide an approach to mimic in vitro a key early stage in human hematopoiesis for the generation of AGM-derived hematopoietic lineages from hESCs

A role for angiotensin-converting enzyme in the characterization, enrichment, and proliferation potential of adult murine pituitary colony-forming cells

Recently, we described a rare cell type within the adult murine pituitary gland with progenitor cell hallmarks (PCFCs). PCFCs are contained exclusively within a subpopulation of cells that import fluorescent ß-Ala-Lys-N-AMCA (7-amino-4-methylcoumarin-3-acetic acid). Herein, we investigate the utility of cell surface molecules angiotensin-converting enzyme (ACE) and stem cell antigen-1 (Sca-1) to further enrich for PCFCs. ACE and Sca-1 were expressed on 61% and 55% of AMCA+CD45–CD31– cells, respectively, and coexpressed on 38%. ACE+Sca-1+AMCA+ cells enriched for PCFCs by 195-fold over unselected cells. ACE+AMCA+ cells enriched for PCFCs by 170-fold, and colonies were twofold larger than for AMCA+ selection alone. Conversely, ACE–-selected cells reduced both colony-forming activity and size. Notably, colonies generated from AMCA+ cells obtained from ACEnull mice were 2.7-fold smaller than for wild-type mice. These data identify ACE as a previously unrecognized marker of PCFCs and suggest that ACE is functionally important for PCFC proliferation. Anatomically, the cells that imported AMCA and expressed ACE were situated in the marginal epithelial cell layer of the pituitary cleft and in the adjacent subluminal zone, thus supporting previous proposals that the luminal zone is a source of precursor cells in the adult pituitary.Diana A. Lepore, Vanta J. Jokubaitis, Paul J. Simmons, Kelly N. Roeszler, Ralph Rossi, Karl Bauer and Paul Q. Thoma