Functional Characterization of a Novel Hematopoietic Stem Cell and Its Place in the c-Kit Maturation Pathway in Bone Marrow Cell Development

Abstract

While the majority of purified pluripotential hematopoietic stem cells (PHSC) express c-Kit, the receptor for steel factor, we have phenotypically and functionally separated a distinct class of PHSC that does not express c-Kit. In contrast to c-Kit-positive (c-Kit(pos)) PHSC, the c-Kit-negative (c-Kit(neg)) PHSC do not proliferate in response to multiple hematopoietic growth factors in vitro and do not radioprotect or form macroscopic spleen colonies (CFU-s) when transplanted into lethally irradiated recipients. However, the c-Kit(neg) PHSC show delayed or slow reconstitution kinetics when cotransplanted with radioprotective bone marrow cells. c-Kit(neg) PHSCs cells can give rise to c-Kit(pos) cells with CFU-s activity, radioprotective activity, and PHSC activity. Thus, constitutive hematopoiesis is maintained by c-Kit(pos) PHSCS cells that are recruited from a more primitive quiescent c-Kit(neg) PHSC population, which represents a critical developmental stage in definitive hematopoiesis.

Storage of unprocessed G-CSF-mobilized whole blood in a modified Leibovitz's L15 medium preserves clonogenic capacity for at least 7 days

“…Fresh CD34-positive cells with either a Thy-1 pos , c-kit low/neg , AC133 pos or CD38 neg phenotype are enriched for more primitive progenitor cells. [44][45][46][47][48][49][50] Adhesion molecules like L-selectin, VLA-4 and VLA-5, and the chemokine receptor CXCR4 are likely associated with engraftment. [51][52][53] No significant changes occurred in the expression of early markers after 7 days under all conditions.…”

Ectopic Pregnancy Rates with Day 3 Versus Day 5 Embryo Transfer: A Retrospective Analysis

“…Twenty-one long-insert-enriched cDNA libraries with insert ranges from 2-8 kb (Piao et al 2001) were generated from preimplantation embryos (unfertilized egg, fertilized egg, two-cell embryo, four-cell embryo, eight-cell embryo, morula, and blastocyst), ES cells (Anisimov et al 2002) and EG cells (Matsui et al 1992), trophoblast stem (TS) cells (Tanaka et al 1998), adult stem cells (e.g., neural stem/progenitor [NS] cells) (Galli et al 2002), mesenchymal stem (MS) cells (Makino et al 1999), osteoblasts (Ochi et al 2003), and hematopoietic stem/progenitor (HS) cells (Ortiz et al 1999), their differentiated cells, and newborn organs (e.g., brain and heart) (see Protocol S1 and Dataset S1 for methods, full list of libraries, and references). In total, 249,200 ESTs (170,059 cDNA clones: 114,437 59 ESTs and 134,763 39 ESTs) were generated and assembled together with public data into a gene index (see Materials and Methods; Protocol S1).…”

Different subsets of primary chronic myeloid leukemia stem cells engraft immunodeficient mice and produce a model of the human disease

“…These range from cells with rapid but transient myeloid-restricted differentiation potential and limited or no self-renewal capacity 23,24 to long-term repopulating cells with additional lymphoid differentiation options, delayed activation in vivo and variable abilities for self-renewal. [25][26][27][28] Experiments with xenografted human cells suggest that human hematopoiesis produces an equivalent hierarchy of transplantable cells that are likewise distinguishable by differences in their phenotypes, differentiation potential and their ability to sustain production of differentiated progeny. 7,[29][30][31][32][33] The present findings suggest that chronic phase CML clones contain a similar hierarchy of primitive transplantable cells.…”