Enhanced endothelialization and microvessel formation in polyester grafts seeded with CD34+ bone marrow cells

Blood ◽  
2000 ◽  
Vol 95 (2) ◽  
pp. 581-585 ◽  
Author(s):  
Vishwanath Bhattacharya ◽  
Peter A. McSweeney ◽  
Qun Shi ◽  
Benedetto Bruno ◽  
Atsushi Ishida ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Progenitor Cells ◽  
Vascular Graft ◽  
Bone Marrow Cells ◽  
Venous Blood ◽  
Immunomagnetic Bead ◽  
Composite Grafts ◽  
Cd34 Cells ◽  
Marrow Cells

The authors have shown accelerated endothelialization on polyethylene terephthalate (PET) grafts preclotted with autologous bone marrow. Bone marrow cells have a subset of early progenitor cells that express the CD34 antigen on their surfaces. A recent in vitro study has shown that CD34+ cells can differentiate into endothelial cells. The current study was designed to determine whether CD34+ progenitor cells would enhance vascular graft healing in a canine model. The authors used composite grafts implanted in the dog's descending thoracic aorta (DTA) for 4 weeks. The 8-mm × 12-cm composite grafts had a 4-cm PET graft in the center and 4-cm standard ePTFE grafts at each end. The entire composite was coated with silicone rubber to make it impervious; thus, the PET segment was shielded from perigraft and pannus ingrowth. There were 5 study grafts and 5 control grafts. On the day before surgery, 120 mL bone marrow was aspirated, and CD34+ cells were enriched using an immunomagnetic bead technique, yielding an average of 11.4 ± 5.3 × 106. During surgery, these cells were mixed with venous blood and seeded onto the PET segment of composite study grafts; the control grafts were treated with venous blood only. Hematoxylin and eosin, immunocytochemical, and AgNO3staining demonstrated significant increases of surface endothelialization on the seeded grafts (92% ± 3.4% vs 26.6% ± 7.6%; P = .0001) with markedly increased microvessels in the neointima, graft wall, and external area compared with controls. In dogs, CD34+ cell seeding enhances vascular graft endothelialization; this suggests practical therapeutic applications.

The Hemoglobin-Haptoglobin Receptor (CD163) Is Expressed by a Subpopulation of Erythroid and Granulo-Macrophagic Progenitors and Can Be Stimulated in Vitro and in Vivo by Physiological and Pharmacological Ligands to Stimulate Hematopoiesis

Blood ◽  
2012 ◽  
Vol 120 (21) ◽  
pp. 1221-1221
Author(s):  
Kathryn Matthews ◽  
Nicole Worsham ◽  
Neeta Rugg ◽  
Jose A. Cancelas ◽  
David Bell
Keyword(s):  
Bone Marrow ◽  
Progenitor Cells ◽  
Bone Marrow Cells ◽  
Fold Increase ◽  
Hematopoietic Progenitor ◽  
Human Cd34 ◽  
Cd34 Cells ◽  
Marrow Cells

Abstract Abstract 1221 The receptor for the hemoglobin (Hb)-haptoglobin (Hp) complex, CD163, is expressed on the surface of a subpopulation of hematopoietic stem/progenitor cells (HPCs) (Matthews et al, 2006). The purpose of the studies presented here were two-fold – to demonstrate that the CD34+CD163+ double positive population could be isolated from normal adult bone marrow cells and these cells were functional as HPCs and, in addition, that these cells could be stimulated in vivo by ligands to CD163 to affect hematopoiesis. To investigate the clonogenic potential of CD34+/CD163+ HPCs, bone marrow CD34+ cells were examined for CD163 co-expression, sorted by fluorescence activated cell sorting (FACS) and plated into colony-forming assays (CFAs). 4.2% ± 1.4% (n=4) of CD34+ cells were found to co-express CD163 and this population consisted of two distinct sub-populations, CD34++ (hi)CD163+ and CD34+(lo)CD163+, each of which represented approximately half of the total CD34+CD163+ population. All three sorted populations (CD34+(all)CD163−, CD34++(hi) CD163+, CD34+(lo)CD163+) were plated into CFAs (n=4) and were assessed for erythroid and myeloid colony formation. The clonogenic efficiency of CD34++(hi)CD163+ had a 2.5-fold increase in the number CFU-E and CFU-GM when compared to both CD34+ (total) CD163− and CD34+(lo) CD163+ cells. In contrast, CD34+(hi an low)CD163+cells produced fewer BFU-E. To determine how the expression of CD163 expression on progenitor cells may play a role in hematopoiesis, we investigated the effects of the natural ligand to CD163 (Hb/Hp) as well as an agonistic antibody to CD163 (TBI 304) on HPCs in vivo. NOD-scid IL2R gammanull (NSG) mice (HuMurine Technologies) were engrafted with human CD34+cells and animals with < 30% human CD45+ cells in the peripheral blood were administered either 2 mg Hb/mouse, or 100 or 500 μg/mouse TBI 304 every 4 days. At study termination (day 14), bone marrow cells (BMC) were examined by flow cytometry and enriched for CD34+ cells for enumeration in CFAs. Hb administration resulted in an increase of human CD34+cells ranging from 4% to 7% of BMC and a corresponding 57% increase in colony-forming cells (CFC) when compared to control (PBS-administered) animals. In contrast, TBI 304 produced a dose dependent decrease in CD34+ and CFC, possibly reflecting a depletion of CD34+/CD163+ cells from overstimulation due to the longer circulating antibody. To investigate this, human CD34+ cell engrafted animals were given a single dose of 10 or 100 μg/mouse of TBI 304 and bone marrow cells were examined on day 7. TBI 304 provided a 3.5-fold increase in human CD34+ cells as well as a 1.8 to 6.7-fold increase in bone marrow erythroid lineage engraftment (huGlyA+, huCD36+ and huCD71+) and a 2-fold increase in erythroid and myeloid colony-forming cells. No overall toxicities were observed with the administration of TBI 304 or Hb. We have demonstrated that CD163 is expressed on a population of CD34+ hematopoietic progenitor cells, these cells have increased hematopoietic progenitor activity in vitro and that administration of physiological or pharmacological agonists of the CD163 receptor can measurably stimulate hematopoiesis in vivo. Disclosures: Matthews: Therapure Biopharma: Employment. Bell:Therapure Biopharma: Employment.

Requirement for p85α Regulatory Subunit of Class IA PI3Kinase and Rac2 GTPase in Myeloproliferative Disease Driven by Activation Loop Mutant of KIT.

Blood ◽  
2007 ◽  
Vol 110 (11) ◽  
pp. 89-89
Author(s):  
Veerendra Munugalavadla ◽  
Emily C. Sims ◽  
Stephen D. Lenz ◽  
Reuben Kapur
Keyword(s):  
Bone Marrow ◽  
Mast Cells ◽  
Progenitor Cells ◽  
Bone Marrow Cells ◽  
Regulatory Subunit ◽  
Activation Loop ◽  
Myeloproliferative Disease ◽  
Hematopoietic Stem ◽  
Marrow Cells

Abstract Oncogenic activation-loop mutants of KIT, the receptor for stem cell factor (SCF), are commonly observed in acute myeloid leukemia (AML) and systemic mastocytosis (SM); however, unlike the KIT juxtamembrane mutants (found in patients with gastrointestinal stromal tumors [GISTs]), the activation-loop mutants are commonly insensitive to inhibition by tyrosine kinase inhibitors. Furthermore, little is known about the signaling pathways that contribute to oncogenic KIT-induced transformation in SM or AML. We demonstrate that expression of KITD814V (KIT activation-loop mutant) in primary hematopoietic stem and progenitor cells induces constitutive KIT autophosphorylation, promotes ligand-independent hyperproliferation, skews myeloid differentiation towards the granulocytic lineage, and promotes promiscuous cooperation with multiple cytokines, including G-CSF, M-CSF and IL-3. KITD814V expressing primary mast cells also demonstrated hyperproliferation in response to SCF, IL-3, IL-4 and IL-10. Biochemical analyses of KITD814V expressing cells revealed constitutively elevated levels of phosphatidylinositol-3-kinase (PI3K) and its downstream substrate, the Rho family GTPase Rac. Genetic disruption of p85a, the regulatory subunit of class IA PI-3Kinase, but not of p85β, or genetic disruption of the hematopoietic cell-specific Rho GTPase, Rac2, normalized KITD814V-induced ligand independent hyperproliferation in vitro. Additionally, deficiency of p85α or Rac2 corrected the promiscuous hyperproliferation observed in response to multiple cytokines in both KITD814V expressing stem/progenitor cells as well as mast cells in vitro. Although p85α is hyperphosphorylated and constitutively bound to KITD814V in bone marrow cells in vitro; its physiologic role in transformation in vivo is not known. To address this, we generated a new mouse model to study KITD814V induced transformation in myeloid cells as opposed to previously described models that primarily result in the generation of phenotypes resembling acute lymphocytic leukemia via this mutation. Our results show that transplantation of KITD814V expressing bone marrow cells from C57/BL6 strain of mice into syngeneic recipients results in a fatal myeloproliferative disease (MPD) characterized by leukocytosis, splenomegaly, disruption of the splenic architecture as well as myeloid cell infiltration in the lung and liver. Importantly, in this model, transplantation of KITD814V expressing p85α deficient bone marrow cells rescued the MPD phenotype, including splenomegaly, peripheral blood leukocytosis and the reduced life span associated with the transplantation of KITD814V expressing wildtype bone marrow cells. Treatment of KITD814V-expressing hematopoietic progenitors with either a Rac inhibitor (NC23766) or rapamycin showed a dose-dependent suppression in KITD814V induced growth. Taken together, our results describe the generation of a new murine transplant model to study KITD814V induced transformation and identify p85a and Rac2 as potential novel therapeutic target for the treatment of KITD814V-bearing diseases including SM and AML.

scholarly journals Inhibition of Immature Erythroid Progenitor Cell Proliferation by Macrophage Inflammatory Protein-1α by Interacting Mainly With a C-C Chemokine Receptor, CCR1

Blood ◽  
1997 ◽  
Vol 90 (2) ◽  
pp. 605-611 ◽  
Author(s):  
Shao-bo Su ◽  
Naofumi Mukaida ◽  
Jian-bin Wang ◽  
Yi Zhang ◽  
Akiyoshi Takami ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Cell Proliferation ◽  
Progenitor Cells ◽  
Bone Marrow Cells ◽  
Erythroid Progenitor ◽  
Erythroid Progenitor Cells ◽  
Inflammatory Protein ◽  
Cd34 Cells ◽  
Macrophage Inflammatory Protein ◽  
Marrow Cells

Abstract Several lines of evidence indicate that macrophage inflammatory protein-1α (MIP-1α) modulates the proliferation of hematopoietic progenitor cells, depending on their maturational stages. To clarify the mechanisms for the modulation of hematopoiesis by this chemokine, we examined the expression of a receptor for MIP-1α, CCR1, on bone marrow cells of normal individuals using a specific antibody and explored the effects of MIP-1α on in vitro erythropoiesis driven by stem cell factor (SCF) and erythropoietin (Epo). CCR1 was expressed on glycophorin A-positive erythroblasts in addition to lymphocytes and granulocytes. CCR1+ cells, isolated from bone marrow mononuclear cells (BMMNCs) using a cell sorter, comprised virtually all erythroid progenitor cells in the BMMNCs. Moreover, MIP-1α inhibited, in a dose-dependent manner, colony formation by burst-forming unit-erythroid (BFU-E), but not by colony forming unit-erythroid (CFU-E), in a methylcellulose culture of purified human CD34+ bone marrow cells. Although reverse-transcription polymerase chain reaction (RT-PCR) showed the presence of CCR1, CCR4, and CCR5 transcripts in CD34+ cells in BM, anti-CCR1 antibodies significantly abrogated the inhibitory effects of MIP-1α on BFU-E formation both in a methylcellulose culture and in a single cell proliferation assay of purified CD34+ cells. Although the contribution of CCR4 or CCR5 cannot be completely excluded, these results suggest that MIP-1α–mediated suppression of the proliferation of immature, but not mature erythroid progenitor cells, is largely mediated by CCR1 expressed on these progenitor cells.

scholarly journals T lymphocyte differentiation in vitro from adult human prethymic CD34+ bone marrow cells.

1993 ◽  
Vol 177 (6) ◽  
pp. 1531-1539 ◽  
Author(s):  
G E Tjønnfjord ◽  
O P Veiby ◽  
R Steen ◽  
T Egeland
Keyword(s):  
Bone Marrow ◽  
T Lymphocyte ◽  
Bone Marrow Cells ◽  
Cell Receptor ◽  
Thymic Tissue ◽  
Adult Human ◽  
Human Cd34 ◽  
Cd34 Cells ◽  
Marrow Cells

Pluripotent lymphohematopoietic stem cells are probably confined to bone marrow cells expressing CD34 surface molecules. To investigate the capacity of adult human CD34+ bone marrow cells to differentiate along the T lymphoid lineage, we plated purified CD34+ cells from healthy adults in liquid culture on adherent thymic stromal cells prepared from HLA- or blood group-mismatched postnatal thymic tissue. We show that purified CD34+CD3-CD4-CD8- bone marrow cells contained progenitors with the ability to differentiate into CD4+ and CD8+ T lymphocytes expressing surface (s)CD3 and T cell receptor alpha/beta in vitro. These progenitors were found in the CD34+CD2+sCD3-CD4-CD8-, CD34+CD7+sCD3-CD4-CD8-, and CD34+CD2+CD7+sCD3-CD4-CD8-, as well as in the CD34+CD2-sCD3-CD4-CD8-, CD34+CD7-sCD3-CD4-CD8-, and CD34+CD2-CD7-sCD3-CD4-CD8- subsets, indicating that T lymphocyte progenitors sensitive to signals mediated by thymic stroma in vitro are not restricted to CD34+ cells already coexpressing early T lymphocyte-associated markers. Finally, we show that T lymphopoiesis was enhanced by c-kit ligand.

scholarly journals Reduced Ischemic Brain Injury by Partial Rejuvenation of Bone Marrow Cells in Aged Rats

2010 ◽  
Vol 31 (3) ◽  
pp. 855-867 ◽  
Author(s):  
Akihiko Taguchi ◽  
Pengxiang Zhu ◽  
Fang Cao ◽  
Akie Kikuchi-Taura ◽  
Yukiko Kasahara ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Progenitor Cells ◽  
Endothelial Progenitor Cells ◽  
Mononuclear Cells ◽  
Bone Marrow Cells ◽  
Aged Rats ◽  
Endothelial Progenitor ◽  
Ischemic Brain ◽  
Marrow Cells

Circulating bone marrow-derived immature cells, including endothelial progenitor cells, have been implicated in homeostasis of the microvasculature. Decreased levels of circulating endothelial progenitor cells, associated with aging and/or cardiovascular risk factors, correlate with poor clinical outcomes in a range of cardiovascular diseases. Herein, we transplanted bone marrow cells from young stroke-prone spontaneously hypertensive rats (SHR-SP) into aged SHR-SP, the latter not exposed to radiation or chemotherapy. Analysis of recipient peripheral blood 28 days after transplantation revealed that 5% of circulating blood cells were of donor origin. Cerebral infarction was induced on day 30 posttransplantation. Animals transplanted with bone marrow from young SHR-SP displayed an increase in density of the microvasculature in the periinfarction zone, reduced ischemic brain damage and improved neurologic function. In vitro analysis revealed enhanced activation of endothelial nitric oxide synthase and reduced activation p38 microtubule-associated protein (MAP) kinase, the latter associated with endothelial apoptosis, in cultures exposed to bone marrow-derived mononuclear cells from young animals versus cells from aged counterparts. Our findings indicate that partial rejuvenation of bone marrow from aged rats with cells from young animals enhances the response to ischemic injury, potentially at the level of endothelial/vascular activation, providing insight into a novel approach ameliorate chronic vascular diseases.

scholarly journals G-CSF and/or M-CSF accelerate differentiation of bone marrow cells into endothelial progenitor cells in vitro

2006 ◽  
Author(s):  
Yuming Zhang ◽  
Yasushi Adachi ◽  
Masayoshi Iwasaki ◽  
Keizo Minamino ◽  
Yasuhiro Suzuki ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Progenitor Cells ◽  
Endothelial Progenitor Cells ◽  
Bone Marrow Cells ◽  
Endothelial Progenitor ◽  
Marrow Cells

Lack of evidence for infection of or effect on growth of hematopoietic progenitor cells after in vivo or in vitro exposure to human immunodeficiency virus

Blood ◽  
1990 ◽  
Vol 76 (12) ◽  
pp. 2476-2482 ◽  
Author(s):  
JM Molina ◽  
DT Scadden ◽  
M Sakaguchi ◽  
B Fuller ◽  
A Woon ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Human Immunodeficiency Virus ◽  
Progenitor Cells ◽  
Bone Marrow Cells ◽  
Hematopoietic Progenitor Cells ◽  
Hematopoietic Progenitor ◽  
Immunodeficiency Virus ◽  
Hiv 1 ◽  
Marrow Cells

The pathogenesis of the hematologic abnormalities commonly observed in patients with acquired immunodeficiency syndrome (AIDS) is incompletely understood. We report here that in vitro growth of myeloid (CFU-GM) and erythroid (BFU-E) progenitor cells from six patients with AIDS was not significantly different from that of normal human immunodeficiency virus (HIV) seronegative donors: 25.3 +/- 5 CFU-GM per 5 x 10(4) low density marrow cells and 33.5 +/- 5 BFU-E were observed in AIDS patients versus 32.7 +/- 5 CFU-GM and 42.1 +/- 5 BFU-E in controls. Furthermore, no HIV-DNA in individual colonies (CFU-GM and BFU-E) could be detected using the polymerase chain reaction (PCR) technique, although HIV-1 DNA was detected in peripheral blood mononuclear cells from the same patients. Similarly, normal bone marrow cells exposed in vitro to different isolates of HIV or recombinant purified HIV-1 envelope glycoprotein (gp) 120 did not exhibit any difference in growth of CFU-GM or BFU-E as compared with mock exposed bone marrow cells. HIV- 1 DNA could not be detected by the PCR technique in individual colonies derived from HIV exposed marrow. This study suggests that committed myeloid and erythroid progenitors from AIDS patients are responsive to hematopoietic growth factors in vitro and do not appear to contain HIV- 1 DNA. Also, HIV or its envelope gp did not alter the growth of hematopoietic progenitor cells in vitro. No evidence of HIV infection of progenitor cells could be demonstrated. Impaired hematopoiesis in patients with AIDS may not be related to direct effects of HIV on committed progenitor cells.

Impairment of lymphopoiesis and myelopoiesis in mice reconstituted with bone marrow–hematopoietic progenitor cells expressing SDF-1–intrakine

Blood ◽  
2000 ◽  
Vol 96 (6) ◽  
pp. 2074-2080 ◽  
Author(s):  
Nobuyuki Onai ◽  
Yan-yun Zhang ◽  
Hiroyuki Yoneyama ◽  
Toshio Kitamura ◽  
Sho Ishikawa ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Progenitor Cells ◽  
Bone Marrow Cells ◽  
Hematopoietic Progenitor Cells ◽  
B Lymphopoiesis ◽  
Hematopoietic Progenitor ◽  
Fcm Analysis ◽  
Marrow Cells

Both SDF-1 and CXCR4 disruption are lethal to mice at the embryonic stage and cause abnormalities in B lymphopoiesis, myelopoiesis, cardiogenesis, vasculogenesis, and cerebellar development. To investigate the role of SDF-1 and CXCR4 in hematopoiesis during the adult stage, mice reconstituted with bone marrow–derived hematopoietic progenitor cells transduced with either the SDF-1 or a genetically modified SDF-1–intrakine gene using a retroviral expression vector were analyzed. Flow cytometric (FCM) analysis showed a dramatic reduction of CXCR4 expression on the cells of intrakine-transduced mice, whereas CCR7 and CCR1 expression was unchanged or marginally decreased on splenocytes. Migration of splenocytes and bone marrow cells to SDF-1 was markedly suppressed in intrakine-transduced mice. FCM analysis of bone marrow cells of intrakine-transduced mice exhibited decreased numbers of pro-B (B220+ CD43+), pre-B (B220+CD43−), and immature B (B220+IgM+) cells and a decreased number of granulocytes/myeloid (Gr1+ CD11b+) cells. Impaired B lymphopoiesis and myelopoiesis in intrakine-transduced mice were confirmed by an in vitro colony-forming assay of bone marrow cells. In contrast, B lymphopoiesis and myelopoiesis were enhanced in SDF-1–transduced mice. Interestingly, T-cell maturation in the thymus was impaired both in intrakine- and SDF-1–transduced mice, suggesting that SDF-1 and CXCR4 play an important role in T lymphopoiesis as well as in B lymphopoiesis and myelopoiesis in adults. These results demonstrate an essential role of CXCR4 and its ligand SDF-1 in adult hematopoiesis, and they indicate the intrakine method as a powerful tool for functional analysis of chemokines/chemokine receptors in vivo and as a potential therapeutic approach for acquired immunodeficiency syndrome.

scholarly journals Alpha 4 beta 1 and alpha 5 beta 1 are differentially expressed during myelopoiesis and mediate the adherence of human CD34+ cells to fibronectin in an activation-dependent way

Blood ◽  
1993 ◽  
Vol 81 (2) ◽  
pp. 344-351 ◽  
Author(s):  
JM Kerst ◽  
JB Sanders ◽  
IC Slaper-Cortenbach ◽  
MC Doorakkers ◽  
B Hooibrink ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Progenitor Cells ◽  
Bone Marrow Cells ◽  
Binding Capacity ◽  
Differentially Expressed ◽  
Myeloid Differentiation ◽  
Erythroid Progenitor ◽  
Fibronectin Binding ◽  
Marrow Cells

To study the receptors involved in the interaction between extracellular matrix proteins and hematopoietic progenitor cells, we analyzed the expression of beta 1 integrins on CD34+ bone marrow cells by means of immunoflowcytometry. Alpha 4 beta 1 and alpha 5 beta 1 were expressed, whereas alpha 1 beta 1, alpha 2 beta 1, alpha 3 beta 1, alpha 6 beta 1, and alpha v beta 1 were virtually absent. Furthermore, we assessed the alpha 4 and alpha 5 expression on committed myeloid progenitor cells. These colony-forming cells were detected in the alpha 4 dull fraction and the alpha 5 dull fraction. During myeloid differentiation, both in vivo and in vitro, a differential expression of alpha 4 beta 1 and alpha 5 beta 1 was observed. alpha 5 beta 1 was found to be lost at the myelocytic-metamyelocytic stage, before the loss of alpha 4 beta 1, at the band stage. Functional studies showed no binding of erythroid progenitor-depleted, CD34+ bone marrow cells to fibronectin. However, protein kinase C activation strongly induced fibronectin binding (68% of the cells). Inhibition experiments with specific antibodies and peptides showed the binding to be mediated by both alpha 4 beta 1 and alpha 5 beta 1. Also, colony-forming cells of granulocytes and macrophages were demonstrated to adhere to fibronectin in an activation-dependent way. During granulocyte colony-stimulating factor-induced in vitro maturation, the activation-dependent fibronectin binding capacity is gradually lost. We conclude that: (1) CD34+ bone marrow cells express alpha 4 beta 1 and alpha 5 beta 1; (2) the expression of alpha 4 beta 1 and alpha 5 beta 1 is differentially expressed during myeloid differentiation; and (3) binding of CD34+ bone marrow cells to fibronectin is activation dependent.

Mad2 (Mitotic Arrest Deficiency 2) Is Essential for the Synergistic Proliferation Induced by Stem Cell Factor Combined with GM-CSF in Hematopoietic Progenitor Cells, Effects Reflecting the Association of c-kit with Mad2.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 71-71
Author(s):  
Shigeki Ito ◽  
Charlie Mantel ◽  
Myung-Kwan Han ◽  
Seiji Fukuda ◽  
Yoji Ishida ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Progenitor Cells ◽  
Bone Marrow Cells ◽  
Cytokine Signaling ◽  
Mouse Bone Marrow ◽  
Wild Type ◽  
Gm Csf ◽  
Kinetics Of ◽  
Marrow Cells

Abstract Mitotic spindle checkpoint protein, Mad2, is required for proper functioning of the mitotic checkpoint which ensures correct chromosome segregation during cell division. Homozygous Mad2 gene deletion is embryonic-lethal. Mad2 interacts with mitosis-associated molecules such as Mad1 and anaphase promoting complex/cyclosome to ensure proper cell cycle progression. Recently, Mad2 was shown to physically associate with the common beta chain of the GM-CSF receptor which raises the possibility that Mad2 may also be involved in cytokine signaling and regulation of mitosis in hematopoietic progenitor cells. To investigate this, we studied hematopoiesis and cytokine signaling in Mad2-haploinsufficient (+/−) mutant mice (M2MT). Colony formation by granulocyte macrophage progenitor cells (CFU-GM) from bone marrow of wild type (WT) mice is synergistically stimulated in vitro by the combination of stem cell factor (SCF) and GM-CSF. We found that bone marrow CFU-GM from M2MT mice are deficient in the synergistic proliferative/colony formation response in vitro to stimulation with the combination of GM-CSF plus SCF. In contrast, there was no difference in stimulation of CFU-GM formation in response to the individual cytokines, GM-CSF or SCF alone, nor a difference in response to pokeweed mitogen mouse spleen cell conditioned medium between M2MT and WT mice. Because there was no difference in the frequency of c-kit+Sca-1+Lin- (KSL) cells nor a difference in the intensity of c-kit surface expression on KSL cells from wild type and M2MT mice, we considered whether the suppression of the SCF/GM-CSF synergy response was due to a difference in intracellular growth-factor receptor signaling pathways. We found that the kinetics of Erk1/2 phosphorylation signaling differ in M2MT Lin- cells compared to WT Lin- cells and that the duration of Erk1/2 phosphorylation in M2MT cells was at least one half of that in WT Lin- cells. On the other hand, we found no difference in the kinetics of Akt phosphorylation between WT and M2MT Lin- cells suggesting a specificity of involvement of the MAP-kinase pathways. To understand how Mad2 plays a role in SCF/GM-CSF synergy, we tested the physical interaction between Mad2 and c-kit in primary Lin- mouse bone marrow cells. Primary Lin- bone marrow cells from WT mice were expanded in liquid culture with SCF and thrombopoietin for 5 days. We found that Mad2 physically associated with c-kit as indicated by co-immunoprecipitation. These results suggest that Mad2 is required for the SCF/GM-CSF proliferative-synergy response in primary Lin- mouse bone marrow cells and that Mad2 is involved in growth-factor signaling pathways, such as the MAP-kinase cascade, in addition to spindle checkpoint function in primary hematopoietic cells. These effects are likely mediated through Mad2 interaction with c-kit and the beta chain of the GM-CSF receptor.

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