Analysis and Characterization of Hematopoietic Progenitor Cells from Fetal Bone Marrow, Adult Bone Marrow, Peripheral Blood, and Cord Blood

Abstract The mechanisms by which hematopoietic progenitor cells are normally anchored in stromal niches and yet can be mobilized by specific growth factors are poorly understood. It is likely, however, that integrins and their extracellular matrix (ECM) ligands play a key role in this process, and recent evidence suggests that integrin function is modulated by signals originating from activated growth factor receptors. We have now examined this further by studying the role of growth factors on α4β1 integrin-mediated adhesion of human CD34+ hematopoietic progenitor cells to specific recombinant fibronectin fragments coated onto tissue culture dishes. Cells were prepared from cord blood and peripheral blood harvests. During a 30-minute adhesion assay a mean of 74% of CD34 cells attached to the so-called H120 fragment of fibronectin, which contains the strongest α4β1 integrin-binding sequence. The level of cell adhesion was significantly reduced by low concentrations of interleukin-3 (IL-3) (2.5 to 10 ng/mL), whereas stem cell factor (SCF ) and granulocyte colony-stimulating factor (G-CSF ) at these concentrations did not affect adherence of the cells. Migratory behavior of CD34 cells was examined using fibronectin fragments adsorbed onto a Transwell filter. The H120 fragment supported much higher levels of cell migration than the H0 fragment of fibronectin, which contains a weak α4β1 integrin binding sequence. Over a 16-hour assay, migration of peripheral blood progenitor cells was increased slightly by SCF and by G-CSF. However, a marked stimulation was observed with IL-3, which significantly increased migration. Similar effects were noted with cord blood cells, although a small proportion of cells were able to migrate in the absence of growth factors. These results indicate that there is a highly selective and functional link between the α4β1 integrin and IL-3/IL-3–receptor that could affect the position of stem and progenitor cells in the marrow stroma and influence their growth and development.

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Evaluation of ex vivo expansion potential of cord blood and bone marrow hematopoietic progenitor cells using cell tracking and limiting dilution analysis

Blood ◽

10.1182/blood.v85.8.2059.bloodjournal8582059 ◽

1995 ◽

Vol 85 (8) ◽

pp. 2059-2068 ◽

Cited By ~ 115

Author(s):

CM Traycoff ◽

ST Kosak ◽

S Grigsby ◽

EF Srour

Keyword(s):

Bone Marrow ◽

Cord Blood ◽

Progenitor Cells ◽

Cell Tracking ◽

Ex Vivo ◽

Hematopoietic Progenitor Cells ◽

Hematopoietic Progenitor ◽

Cells In Culture ◽

Cd34 Cells ◽

Limiting Dilution

In the absence of conclusive assays capable of determining the functionality of ex vivo expanded human hematopoietic progenitor cells, we combined cell tracking with the membrane dye PKH2, immunostaining for CD34, and limiting dilution analysis to estimate the frequency of long-term hematopoietic culture-initiating cells (LTHC-ICs) among de novo-generated CD34+ cells. Umbilical cord blood (CB) and bone marrow (BM) CD34+ cells were stained with PKH2 on day 0 and cultured with stem cell factor (SCF) and interleukin-3 (IL-3) in short-term stromal cell-free suspension cultures. Proliferation of CD34+ cells in culture was tracked through their PKH2 fluorescence relative to day 0 and the continued expression of CD34. As such, it was possible to identify cells that had divided while maintaining the expression of CD34 (CD34+PKH2dim) and others that expressed CD34 but had not divided (CD34+PKH2bright). In all such cultures, a fraction of both BM and CB CD34+ cells failed to divide in response to cytokines and persisted in culture for up to 10 days as CD34+PKH2bright cells. Between days 5 and 7 of culture, CD34+PKH2bright and CD34+PKH2dim cells were sorted in a limiting dilution scheme into 96-well plates prepared with medium, SCF, IL-3, IL-6, granulocyte-macrophage colony-stimulating factor, and erythropoietin. Cells proliferating in individual wells were assayed 2 weeks later for their content of clonogenic progenitors and the percentage of negative wells was used to calculate the frequency of LTHC-ICs in each population. Among fresh isolated BM and CB CD34+ cells, the frequencies of LTHC-ICs were 2.01% +/- 0.98% (mean +/- SEM) and 7.56% +/- 2.48%, respectively. After 5 to 7 days in culture, 3.00% +/- 0.56% of ex vivo-expanded BM CD34+PKH2bright cells and 4.46% +/- 1.10% of CD34+PKH2dim cells were LTHC-ICs. In contrast, the frequency of LTHC-IC in ex vivo expanded CB CD34+ cells declined drastically, such that only 3.87% +/- 2.06% of PKH2bright and 2.29% +/- 1.75% of PKH2dim cells were determined to be initiating cells after 5 to 7 days in culture. However, when combined with a calculation of the net change in the number of CD34+ cells in culture, the sum total of LTHC-ICs in both BM and CB cells declined in comparison to fresh isolated cells, albeit to a different degree between the two tissues.(ABSTRACT TRUNCATED AT 400 WORDS)

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The RNA Editing Enzyme ADAR1 Is Required for Survival of Differentiating Hematopoietic Progenitor Cells in Adult Mice.

Blood ◽

10.1182/blood.v112.11.1395.1395 ◽

2008 ◽

Vol 112 (11) ◽

pp. 1395-1395

Author(s):

Feng Xu ◽

Qingde Wang ◽

Hongmei Shen ◽

Hui Yu ◽

Yanxin Li ◽

...

Keyword(s):

Bone Marrow ◽

Progenitor Cells ◽

Rna Editing ◽

Cell Population ◽

Peripheral Blood ◽

Hematopoietic Progenitor Cells ◽

Hematopoietic Progenitor ◽

Hematopoietic Stem ◽

Low Level ◽

Adult Mice

Abstract Adenosine Deaminases Acting on RNA (ADAR) are RNA-editing enzymes converting adenosine residues into inosine (A-to-I) in many double-stranded RNA substrates including coding and non-coding sequences as well as microRNAs. Disruption of the ADAR1 gene in mice results in fetal liver, but not yolk sac, defective erythropoiesis and death at E11.5 (Wang Q et al, Science 2000). Subsequently, a conditional knockout mouse model confirmed these findings and showed massively increased cell death in the affected organs (Wang Q et al, JBC 2004). However, the actual impact of ADAR1 absence on definitive or adult hematopoiesis has not been examined. To define the role of ADAR1 in adult hematopoiesis, we first examined the expression of ADAR1 in different hematopoietic stem/progenitor cell subsets isolated from bone marrow by real-time RT-PCR. ARAR1 was present in hematopoietic stem cells (HSCs) at relatively low level and increased in hematopoietic progenitor cells (HPCs). A series of functional hematopoietic assays were then undertaken. A conditional deletion of ADAR1 was achieved by transducing Lin− or Lin−cKit+ bone marrow cells from ADAR1-lox/lox mice with a MSCV retroviral vector co-expressing Cre and GFP. PCR analysis confirmed the complete deletion of ADAR1 in the transduced cells within 72 hours after the transduction. This system allowed us to evaluate the acute effect of ADAR1 deletion in a specific hematopoietic cell population. Following 4 days of in vitro culture after transduction, the absolute number of Lin− Sca1+ cells in the Cre transduced group was similar to the input number; however the differentiating Lin+ cells significantly decreased whereas both the Lin−Sca1+ and Lin+ cells in the vector (MSCV carrying GFP alone) transduced group increased during culture. Moreover, the colony forming cell (CFC) assay showed much fewer and smaller colonies that contained dead cells from the gene deleted group as compared to those from the control group (p<0.001). The TUNEL assay showed a dramatic increase of apoptosis in the Lin+ population but not in the Lin− cells. Given the mixed genetic background of the ADAR1-lox/lox mice, repopulation of the transduced hematopoietic cells in vivo was examined in immunodeficient mice. Sublethally irradiated (3.5 Gy) NOD/SCID-γcnull recipient were transplanted with either 1.5 × 105 Cre or vector transduced Lin− ADAR1-lox/lox cells. Multi-lineage engraftment in peripheral blood was monitored monthly. While the vector transduced cells were able to constitute more than 90% in multiple lineages of the peripheral blood at 1 to 3 months, Cre-transduced cells were virtually undetectable at all the time points (n=9 to 13, p<0.001). A similar result was found in the hematopoietic organs, including the bone marrow, spleen and thymus. Interestingly, however, the Lin−Sca1+cKit+ cell population was preserved in the Cre transduced group despite the very low level of total donor-derived cells in the bone marrow (n=6 to 7, p<0.01). Consistently, the single cell culture experiment demonstrated that there was no significant difference between ADAR−/− and wild-type HSCs in terms of survival and division during the first 3 days of culture. Taken together, our current study demonstrates nearly absolute requirement of ADAR1 for hematopoietic repopulation in adult mice and it is also suggested that ADAR1 has a preferential effect on the survival of differentiating progenitor cells over more primitive cells.

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