Number Of Hematopoietic Progenitor Cells Research Articles

Aberrant Regulation of Hematopoiesis by T Cells in BAZF-Deficient Mice

The BAZF (BCL-6b) protein is highly similar to the BCL-6 transcriptional repressor. While BCL-6 has been characterized extensively, relatively little is known about the normal function of BAZF. In order to understand the physiological role of BAZF, we created BAZF-deficient mice. Unlike BCL-6-deficient mice, BAZF-deficient mice are healthy and normal in size. However, BAZF-deficient mice have a hematopoietic progenitor phenotype that is almost identical to that of BCL-6-deficient mice. Compared to wild-type mice, both BAZF-deficient and BCL-6-deficient mice have greatly reduced numbers of cycling hematopoietic progenitor cells (HPC) in the BM and greatly increased numbers of cycling HPC in the spleen. In contrast to HPC from wild-type mice, HPC from BAZF-deficient and BCL-6-deficient mice are resistant to chemokine-induced myelosuppression and do not show a synergistic growth response to granulocyte-macrophage colony-stimulating factor plus stem cell factor. Depletion of CD8 T cells in BAZF-deficient mice reverses several of the hematopoietic defects in these mice. Since both BAZF- and BCL-6-deficient mice have defects in CD8 T-cell differentiation, we hypothesize that both BCL-6 and BAZF regulate HPC homeostasis by an indirect pathway involving CD8 T cells.

Effects of Chromatin-Modifying Agents on CD34+ Cells from Patients with Idiopathic Myelofibrosis

Idiopathic myelofibrosis (IM) is likely the consequence of both the acquisition of genetic mutations and epigenetic changes that silence critical genes that control cell proliferation, differentiation, and apoptosis. We have explored the effects of the sequential treatment with the DNA methyltransferase inhibitor, decitabine [5-aza-2'-deoxycytidine (5azaD)], followed by the histone deacetylase inhibitor, trichostatin A (TSA), on the behavior of IM CD34(+) cells. Unlike normal CD34(+) cells where 5azaD/TSA treatment leads to the expansion of CD34(+) cells and marrow-repopulating cells, treatment of IM CD34(+) cells results in a reduction of the number of total cells, CD34(+) cells, and assayable hematopoietic progenitor cells (HPC). In IM, HPCs are either heterozygous or homozygous for the JAK2V617F mutation or possess wild-type JAK2 in varying proportions. Exposure of IM CD34(+) cells to 5azaD/TSA resulted in a reduction of the proportion of JAK2V617F-positive HPCs in 83% of the patients studied and the reduction in the proportion of homozygous HPCs in 50% of the patients. 5azaD/TSA treatment led to a dramatic reduction in the number of HPCs that contained chromosomal abnormalities in two JAK2V617F-negative IM patients. IM is characterized by constitutive mobilization of HPCs, which has been partly attributed to decreased expression of the chemokine receptor CXCR4. Treatment of IM CD34(+) cells with 5azaD/TSA resulted in the up-regulation of CXCR4 expression by CD34(+) cells and restoration of their migration in response to SDF-1. These data provide a rationale for sequential therapy with chromatin-modifying agents for patients with IM.

Aberrant Regulation of Hematopoiesis by T cells in BAZF-Deficient Mice (B7)

Abstract The BAZF (BCL6b) protein is highly similar to the BCL6 transcriptional repressor. While BCL6 has been characterized extensively, relatively little is known about the normal function of BAZF. In order to understand the physiological role of BAZF, we created BAZF-deficient mice. Unlike BCL6-deficient mice, BAZF-deficient mice are healthy and normal in size. However BAZF-deficient mice have a hematopoietic progenitor phenotype that is almost identical to that of BCL6-deficient mice. Compared to wild-type mice, both BAZF-deficient and BCL6-deficient mice have greatly reduced numbers of cycling hematopoietic progenitor cells (HPC) in the bone marrow and greatly increased numbers of cycling HPC in the spleen. In contrast to HPC from wild-type mice, HPC from BAZF-deficient and BCL6-deficient mice are resistant to chemokine-induced myelo-suppression and do not show a synergistic growth response to GM-CSF plus Stem Cell Factor. Depletion of CD8 T cells in BAZF-deficient mice reverses several of the hematopoietic defects in these mice. Since both BAZF- and BCL6-deficient mice have defects in CD8 T cell differentiation, we hypothesize that both BCL6 and BAZF regulate HPC homeostasis by an indirect pathway involving CD8 T cells.

Regulation of myeloid progenitor cell proliferation/survival by IL-31 receptor and IL-31

Interleukin (IL)-31 is a recently discovered helical cytokine. Its receptor consists of a ligand-specific IL-31 receptor (IL-31R) subunit and a receptor chain that is shared with Oncostatin M (OSM), called OSM-Rbeta. Because OSM-Rbeta-deficient animals have reduced hematopoietic progenitor cells (HPC) and OSM has effects on and is involved in homeostasis of HPC, we studied whether IL-31 and IL-31R play a role in hematopoiesis. IL-31R(-/-) mice and their littermate wild-type (WT) controls were assessed for absolute numbers and cycling status of bone marrow and spleen HPC (colony-forming unit granulocyte macrophage [CFU-GM], burst-forming unit erythroid [BFU-E], colony-forming unit granulocyte, erythrocyte, macrophage, megakaryocyte). Recombinant IL-31 was evaluated for stimulation, enhancement, or inhibition of colony formation by HPC, and for survival-enhancing effects on HPC subjected to growth-factor withdrawal and delayed addition of grown factors. Hematopoietic stem cells (HSC) from WT and IL-31R(-/-) mice were compared for competitive repopulating capacity in lethally irradiated congenic mice. IL-31R(-/-) mice demonstrated significantly decreased absolute numbers and cycling status of immature subsets of HPC in bone marrow bone and spleen compared to WT mice. There were no significant differences in absolute numbers of more mature subsets of WT and IL-31R(-/-) bone marrow CFU-GM. WT but not IL-31R(-/-) bone marrow CFU-GM responded to synergistic stimulation by combinations of cytokines. While IL-31 had neither colony-stimulating, -enhancing, or -inhibiting activity for bone marrow HPC, it did enhance survival of these HPC in the context of delayed addition of growth factors. No significant differences were detected in competitive repopulating HSC activity between WT and IL-31R(-/-) bone marrow cells. IL-31R is involved in positive regulation of absolute numbers and cycling status of immature subsets of HPC in vivo. While IL-31 in vitro does not modulate proliferation of HPC, it does enhance their survival, which may contribute to effects on cycling and numbers of HPC in vivo. Under steady-state conditions, loss of IL-31R on HPC does not appear to influence the activity of competitive repopulating HSC. These results with HPC may be of future utility for manipulation of hematopoiesis in a preclinical setting.

The mediator complex functions as a coactivator for GATA-1 in erythropoiesis via subunit Med1/TRAP220

The Mediator complex forms the bridge between transcriptional activators and RNA polymerase II. Mediator subunit Med1/TRAP220 is a key component of Mediator originally found to associate with nuclear hormone receptors. Med1 deficiency causes lethality at embryonic day 11.5 because of defects in heart and placenta development. Here we show that Med1-deficient 10.5 days postcoitum embryos are anemic but have normal numbers of hematopoietic progenitor cells. Med1-deficient progenitor cells have a defect in forming erythroid burst-forming units (BFU-E) and colony-forming units (CFU-E), but not in forming myeloid colonies. At the molecular level, we demonstrate that Med1 interacts physically with the erythroid master regulator GATA-1. In transcription assays, Med1 deficiency leads to a defect in GATA-1-mediated transactivation. In chromatin immunoprecipitation experiments, we find Mediator components at GATA-1-occupied enhancer sites. Thus, we conclude that Mediator subunit Med1 acts as a pivotal coactivator for GATA-1 in erythroid development.

Immune Mobilization of Autologous Peripheral Blood Progenitor Cells: IL-2 with GM-CSF and G-CSF Results in Effective Mobilization without Delay in Engraftment.

We initiated an immune mobilization trial in an attempt to mobilize cytotoxic effector cells, along with CD34+ hematopoietic progenitor cells. A Prospective Phase I trial was initiated using dose escalation of IL-2, in combination with GM-CSF and G-CSF. IL-2 began on Day 0 and continued as a daily SQ injection for 11 days. On Day 7, GM-CSF (7.5 mcg/kg/d) and G-CSF (5 mcg/kg/d) were initiated for 5 days (Days 7–11). On Day 11, leukapheresis was started if the peripheral blood CD34 + cell count was > 5 cells/mcl. The endpoint of collection was ≥ 3 × 106 CD34+ cells/kg. After collection, patients received melphalan (200 mg/m2) followed by infusion of cryopreserved stem cells. Post-transplant GM-CSF began on Day +5 and terminated once the ANC reached 5000 cells/mcl. To date, 9 patients have been treated (myeloma, n = 8; NHL, n = 1) and 7 patients are evaluable. Six patients received IL-2 at Dose Level 1 (6 × 105 IU/m2/d). The remaining 3 patients received IL-2 at Dose Level 2 (1 × 106 IU/m2/d). The MTD of IL-2 has not been reached. One patient (NHL) was removed from the study due to progressive disease. The remaining 8 patients completed the regimen. Toxicities have been mild and have included Grade 2 fever (n=1) on Dose Level 2. All patients were successfully mobilized. The median number of CD34+ cells/kg and MNC/kg collected were 3.4 × 106 (range 2.8 – 4.4 × 106/kg) and 9.5 × 108 (range 0.4 – 1.7 × 109), respectively. Two large volume leukaphereses were required (median; range 1 – 3). Following transplant, the ANC recovered on Day 13 (median; range: 10 – 14 d) and platelets recovered on Day 12 (median; range 0 – 13 d). These preliminary results demonstrate that immune mobilization and collection of an adequate number of hematopoietic progenitor cells is feasible without suppression of hematopoiesis. Toxicities are minimal but the MTD of IL-2 has not yet been reached. Post-transplant engraftment is not delayed. As patient accrual continues, we are currently evaluating the qualitative and quantitative components of the collected cells, including Th1 vs. Th2 cells and the types of dendritic cells mobilized.

PBI-1402: A Non-Toxic Immunorestorative Small Molecule for the Treatment of Anemia.

Erythropoiesis is regulated by an intricated network of transcription factors and other molecules that mediate differentiation of stem cell progenitors into erythroid lineage. PBI-1402 is a non-toxic, well-defined chemo- and radio-protective orally active small molecule which stimulates erythropoiesis. In vivo studies demonstrate that PBI-1402 has an immunorestorative effect in anemia induced by phenylhydrazine or lethal irradiation. In phenylhydrazine-induced anemia, PBI-1402 treated mice had an increased number of hematopoietic progenitor cells compared to the control mice. This increase was more pronounced in the erythroid lineage (BFU-E and CFU-E). In myeloablated mice that received a syngeneic bone marrow transplant, oral treatment with PBI-1402 resulted in a significant increase in peripheral erythrocyte count and hemoglobin concentration. In conclusion, these results indicate that PBI-1402 plays an important role in the formation of red blood cells. Therefore, PBI-1402 may be useful for the treatment of anemia associated with chemotherapy, radiotherapy, bone marrow transplantation and cancer.

Mll partial tandem duplication induces aberrant Hox expression in vivo via specific epigenetic alterations

We previously identified a rearrangement of mixed-lineage leukemia (MLL) gene (also known as ALL-1, HRX, and HTRX1), consisting of an in-frame partial tandem duplication (PTD) of exons 5 through 11 in the absence of a partner gene, occurring in approximately 4%-7% of patients with acute myeloid leukemia (AML) and normal cytogenetics, and associated with a poor prognosis. The mechanism by which the MLL PTD contributes to aberrant hematopoiesis and/or leukemia is unknown. To examine this, we generated a mouse knockin model in which exons 5 through 11 of the murine Mll gene were targeted to intron 4 of the endogenous Mll locus. Mll(PTD/WT) mice exhibit an alteration in the boundaries of normal homeobox (Hox) gene expression during embryogenesis, resulting in axial skeletal defects and increased numbers of hematopoietic progenitor cells. Mll(PTD/WT) mice overexpress Hoxa7, Hoxa9, and Hoxa10 in spleen, BM, and blood. An increase in histone H3/H4 acetylation and histone H3 lysine 4 (Lys4) methylation within the Hoxa7 and Hoxa9 promoters provides an epigenetic mechanism by which this overexpression occurs in vivo and an etiologic role for MLL PTD gain of function in the genesis of AML.

Synergistic inhibition in vivo of bone marrow myeloid progenitors by myelosuppressive chemokines and chemokine-accelerated recovery of progenitors after treatment of mice with Ara-C

Selected chemokines suppress proliferation of hematopoietic progenitor cells (HPCs) in vitro; some of these have demonstrated inhibition of myelopoiesis in vivo. Because myelosuppressive chemokines synergize in vitro with other myelosuppressive chemokines, we sought to determine whether additional chemokines active in vitro were myelosuppressive in vivo and whether combinations of myelosuppressive chemokines synergized in vivo to dampen myelopoiesis. We also evaluated three chemokines in vivo for myeloprotection against Ara-C-induced decreases in HPCs. C3H/HeJ mice were used for analysis of in vivo influence of chemokines, with the end points being effects on absolute numbers and cycling status of HPCs. When used alone, CCL2, CCL3, CCL19, CCL20, CXCL4, CXCL5, CXCL8, CXCL9, and XCL1 caused dose-dependent significant decreases in absolute numbers and cycling status of HPCs in vivo. The following combinations of two chemokines resulted in in vivo myelosuppression at concentrations much lower than that induced by each chemokine alone: CCL3 plus either CXCL8 or CXCL4, CXCL8 plus CXCL4, CCL2 plus either CCL20 or CXCL9, CCL20 plus CXCL9, CXCL5 plus either XCL1 or CCL19, XCL1 plus CCL19, and CCL3 plus CCL19. Also, mice injected with CXCL8, CXCL4, or the chimeric CXCL8/CXCL4 protein CXCL8M1 manifested accelerated recovery of absolute numbers of HPCs in response to the toxic effects of Ara-C administration. A number of chemokines shown previously to manifest inhibitory effects in vitro for proliferation of HPCs are now demonstrated to also induce myelosuppression in vivo. Moreover, combinations of low dosages of two myelosuppressive chemokines when administered together demonstrate synergistic suppression in vivo. Additionally, chemokines, including a CXCL8M1 chimeric protein previously shown to manifest enhanced suppression of HPC proliferation in vitro and in vivo, accelerate HPC recovery after treatment of mice with Ara-C. These results may be of use for future clinical utility of chemokines in a myelosuppressive/myeloprotective setting.

Genetic reduction of class IA PI-3 kinase activity alters fetal hematopoiesis and competitive repopulating ability of hematopoietic stem cells in vivo

Class I(A) phosphatidylinositol-3 kinase (PI-3K) is a lipid kinase, which is activated in blood cells by hematopoietic growth factors. In vitro experiments using chemical inhibitors of PI-3K suggest that this kinase is potentially important for hematopoietic stem and progenitor cell (HSC/P) function, and recent studies identify PI-3K as a therapeutic target in treating different leukemias and lymphomas. However, the role of PI-3K in regulating fetal liver or adult hematopoiesis in vivo is unknown. Therefore, we examined PI-3K-deficient embryos generated by a targeted deletion of the p85alpha and p85beta regulatory subunits of PI-3K (p85alpha-/-p85beta+/-). The absolute frequency and number of hematopoietic progenitor cells were reduced in p85alpha-/- p85beta+/- fetal livers compared with wild-type (WT) controls. Further, p85alpha-/-p85beta+/- fetal liver hematopoietic stem cells (HSCs) had decreased multilineage repopulating ability in vivo compared with WT controls in competitive repopulation assays. Finally, purified p85alpha-/-p85beta+/- c-kit+ cells had a decrease in proliferation in response to kit ligand (kitL), a growth factor important for controlling HSC function in vivo. Collectively, these data identify PI-3K as an important regulator of HSC function and potential therapeutic target in treating leukemic stem cells.

Increased immature hematopoietic progenitor cells CD34+/CD38dim in myelodysplasia

Myelodysplastic syndromes (MDS) are clonal disorders affecting hematopoietic progenitor cells (HPC). Despite the relevance of clonal CD34+ cells in developing MDS, only few studies analyze the phenotype of this cell population. The aim of this study was to evaluate phenotypic changes on HPC in MDS that could reflect abnormalities in the differentiation process of stem cells. We analyzed the expression of CD38 and HLA-DR on CD34+ cells by flow cytometry in 36 patients with MDS, as well as in healthy donors (n = 12) and patients with other hematological disorders: non-Hodgkin lymphomas and multiple myeloma, both in complete remission (CR) (n = 32); acute lymphoblastic leukemia in CR (n = 17); de novo acute myeloblastic leukemia (AML) at diagnosis (n = 22) and in CR (n = 37); and AML secondary to MDS at diagnosis (n = 19). Cases with available karyotype were grouped according to the International Prognostic Scoring System (IPSS). Compared to normal BM, the fraction of immature HPC, characterized as CD34+bright, intermediate FSC/SSC, and CD38dim, was significantly increased in high risk MDS and secondary AML, but not in low risk MDS, (P < or = 0.001, P = 0.03, and P = 0.7). De novo AML showed decreased immature HPC. High numbers of immature HPC correlated with higher IPSS risk groups (P = 0.05) and showed significant impact on disease progression (P = 0.03). Our study confirms that evaluation of CD38 expression pattern on HPC is an easy and reproducible test that allows evaluating the immature subset of progenitor cells. Increased immature HPC in high risk MDS and secondary AML may reflect blocked differentiation of CD34+ cells in these diseases.

AMD3100 + G-CSF improves hematopoietic progenitor cell (HPC) collection in patients with hodgkin’s disease (HD)

Autologous stem cell transplantation is indicated for patients with HD who have primary refractory disease or who relapse after a first remission. For these patients, as for other patients undergoing autologous transplantation, the number of CD34+ cells infused is a reliable predictor of neutrophil and platelet engraftment, and doses ≥ 5 x 10 6 CD34+ cells/kg are associated with faster count recovery. However, among the 98 patients with HD who have undergone G-CSF-alone mobilization at our institution in the past five years, 22% did not achieve a minimum HPC collection of 2 x 10 6 CD34+ cells/kg in ≤ 5 apheresis procedures, and only 15% achieved a collection ≥ 5 x 10 6 CD34+ cells/kg. AMD3100 mobilizes HPCs by reversibly inhibiting the interaction of CXCR4 and SDF-1α. It has been shown to improve HPC mobilization in patients with multiple myeloma and non-Hodgkin’s lymphoma. Here we present results for the first ten HD patients treated with a mobilization regimen of AMD3100 + G-CSF. To date, ten patients with relapsed (8) or refractory (2) HD have been mobilized with G-CSF (10 ug/kg/d) + AMD3100 (240 ug/kg/d) beginning on day 4. Apheresis was performed 11 hours after each AMD3100 dose. The first dose of AMD3100 produced a median (range) 3.0 (1.9–5.1) fold increase in the number of circulating CD34+ cells. Six patients (60%) achieved a collection of ≥ 5 x 10 6 CD34+ cells/kg, and all patients collected > 2 x 10 6 CD34+ cells/kg (range, 3.6–9.4 x 10 6 CD34+ cells/kg). The median (range) number of apheresis procedures performed per patient was 2 (1–4). No grade II-IV adverse events were ascribed to AMD3100. Eight patients have been transplanted with G-CSF + AMD3100 mobilized cells. All have had prompt and stable engraftment, with median neutrophil recovery at day +9 (9–11) and median platelet recovery at day +20 (15–23). Two patients had very early engraftment, with absolute neutrophil count greater than 100 on day +7. We conclude that AMD3100 + G-CSF is a well-tolerated and effective mobilization regimen in patients with HD. All patients (100%, 95% CI 69%-100%) mobilized with AMD3100 + G-CSF achieved the minimum collection of 2 x 10 6 CD34+ cells/kg, and a significantly higher proportion of patients (60%, 95% CI 26%–88%) achieved the goal collection of ≥ 5 x 10 6 CD34+ cells/kg than did the historical controls (15%). Importantly, the median collection in the first two days of pheresis was 5.4 x 10 6 CD34+ cells/kg, which is significantly better than historical controls, who collected a median 3.0 x 10 6 CD34+ cells/kg in the first two days of pheresis (p=0.014). Our results demonstrate that the mobilization regimen of AMD3100 + G-CSF can improve the number of HPCs collected and decrease the number of days of pheresis in HD patients. This regimen will be pursued further in this patient population.

Hematopoietic progenitor cells (HPC) and immature reticulocytes evaluations in mobilization process: new parameters measured by conventional blood cell counter

Monitoring the timing of leukapheresis in peripheral blood stem cells (PBSC) mobilization is an important clinical decision that requires an accurate analytical tool. The present study assessed hematopoietic progenitor cells (HPC) and immature reticulocyte fraction (IRF) counts provided by a routine automated blood counter as potential parameters for predicting the appropriate time for harvesting. The HPC and IRF values were compared with white blood cell (WBC) and CD34+ cell counts obtained by flow cytometry in 30 adult patients with hematological malignancies undergoing PBSC mobilization. It was observed that there was a significant correlation between HPC counts and CD34(+) cells in peripheral blood counts (r=0.61, P=0.0003) and between the number of HPC and CD34+cells collected by leukapheresis (r=0.5733, P=0.0009). Comparing HPC, IRF, WBC, and CD34+ cells parameters as a sign of hematological recovery showed that the raise in immature reticulocytes counts preceded the increase of WBC (P=0.0002), HPC (P=0.0001), and CD34(+) (P=0.0001) cells in peripheral blood counts. According to our results, HPC and IRF parameters may be integrated into clinical protocols to evaluate the timing of leukapheresis. IRF, as previously demonstrated in bone marrow transplantation, is the earliest sign of hematopoietic recovery in mobilization process.

AMD3100 + G-CSF Improves Hematopoietic Progenitor Cell (HPC) Collection in Patients with Hodgkin's Disease (HD).

Autologous stem cell transplantation is indicated for patients with HD who have primary refractory disease or who relapse after a first remission. For these patients, as for other patients undergoing autologous transplantation, the number of CD34+ cells infused is a reliable predictor of neutrophil and platelet engraftment, and doses ≥ 5 x 106 CD34+ cells/kg are associated with faster count recovery. However, among the 98 patients with HD who have undergone G-CSF-alone mobilization at our institution in the past five years, 22% did not achieve a minimum HPC collection of 2 x 106 CD34+ cells/kg in ≤ 5 apheresis procedures, and only 15% achieved a collection ≥ 5 x 106 CD34+ cells/kg. AMD3100 mobilizes HPCs by reversibly inhibiting the interaction of CXCR4 and SDF-1α. It has been shown to improve HPC mobilization in patients with multiple myeloma and non-Hodgkin’s lymphoma. Here we present results for the first ten HD patients treated with a mobilization regimen of AMD3100 + G-CSF. To date, ten patients with relapsed (8) or refractory (2) HD have been mobilized with G-CSF (10 ug/kg/d) + AMD3100 (240 ug/kg/d) beginning on day 4. Apheresis was performed 11 hours after each AMD3100 dose. The first dose of AMD3100 produced a median (range) 3.0 (1.9–5.1) fold increase in the number of circulating CD34+ cells. Six patients (60%) achieved a collection of ≥ 5 x 106 CD34+ cells/kg, and all patients collected &gt; 2 x 106 CD34+ cells/kg (range, 3.6–9.4 x 106 CD34+ cells/kg). The median (range) number of apheresis procedures performed per patient was 2 (1–4). No grade II-IV adverse events were ascribed to AMD3100. Eight patients have been transplanted with G-CSF + AMD3100 mobilized cells. All have had prompt and stable engraftment, with median neutrophil recovery at day +9 (9–11) and median platelet recovery at day +20 (15–23). Two patients had very early engraftment, with absolute neutrophil count greater than 100 on day +7. We conclude that AMD3100 + G-CSF is a well-tolerated and effective mobilization regimen in patients with HD. All patients (100%, 95% CI 69%-100%) mobilized with AMD3100 + G-CSF achieved the minimum collection of 2 x 106 CD34+ cells/kg, and a significantly higher proportion of patients (60%, 95% CI 26%–88%) achieved the goal collection of ≥ 5 x 106 CD34+ cells/kg than did the historical controls (15%). Importantly, the median collection in the first two days of pheresis was 5.4 x 106 CD34+ cells/kg, which is significantly better than historical controls, who collected a median 3.0 x 106 CD34+ cells/kg in the first two days of pheresis (p=0.014). Our results demonstrate that the mobilization regimen of AMD3100 + G-CSF can improve the number of HPCs collected and decrease the number of days of pheresis in HD patients. This regimen will be pursued further in this patient population.

Human hematopoietic stem/progenitor‐enriched CD34+ cells are mobilized into peripheral blood during stress related to ischemic stroke or acute myocardial infarction

The hematopoietic and non-hematopoietic stem/progenitor cells harvested directly from the bone marrow (BM) or G-CSF mobilized peripheral blood were demonstrated to play an important role in regeneration of damaged organs (1, 2). Here, we asked if the stroke- or acute heart infarct-related stress triggers mobilization of stem/progenitor-enriched CD34(+)cells from the BM into the peripheral blood, which subsequently could contribute to regeneration of damaged tissues. To address this question the peripheral blood samples were harvested from patients with ischemic stroke during the first 24 h of manifestation of symptoms and on the second and sixth day afterwards or during the first 24 h of acute cardiac pain as well as on the second and sixth day of infarct. We measured in these patients (i) percentage of circulating hematopoietic stem/progenitor-enriched CD34(+) cells in peripheral blood by employing fluorescence activated cell sorter (FACS) and (ii) number of hematopoietic progenitor cells for the granulocyte-monocytic colony-forming unit (CFU-GM) and erythoid burst-forming unit (BFU-E) lineages circulating in peripheral blood. We concluded that stress related to ischemic stroke or acute myocardial infarction triggers the mobilization of hematopoietic stem/progenitor-enriched CD34(+) cells from the BM into peripheral blood. These circulating stem/progenitor-enriched CD34(+) cells may contribute to the regeneration of ischemic tissues, however, this possibility requires further studies.

Hematopoietic Progenitor Cell Mobilization by Granulocyte Colony-Stimulating Factor and Erythropoietin in the Absence of Matrix Metalloproteinase-9

The use of mobilized hematopoietic progenitor cells (HPC) has largely replaced the use of bone marrow HPC for autologous and allogeneic transplantation; however, the mechanisms of HPC mobilization remain unclear. A better understanding of these mechanisms, may allow the development of improved (potentially more rapid and/or higher yield) HPC mobilization strategies, especially for patients who mobilize poorly using current mobilization protocols. Clinically, granulocyte colony-stimulating factor (G-CSF) is widely used to induce HPC mobilization, and evidence suggests that metalloproteinase enzymes released by activated granulocytes play an important role in the G-CSF-induced HPC mobilization. These enzymes may act to disrupt putative cell-cell and/or cell-extracellular matrix interactions within the hematopoietic microenvironment thereby releasing HPC into the blood. Matrix metalloproteinase-9 (MMP-9) appears to be important for G-CSF-induced mobilization. Using an MMP-9 knock-out (KO) mouse model, we investigated the role of MMP-9 in G-CSF and erythropoietin (EPO)-based HPC mobilization at clinically relevant cytokine doses. There were few hematologic or hematopoietic differences between the wild-type and MMP-9KO mice during steady-state hematopoiesis. When treated subcutaneously with EPO (500 U/kg per day) and G-CSF (15 microg/kg per day) for 5 days and assayed on day 6, similarly increased extramedullary hematopoiesis and numbers of HPC in the spleen and blood were observed for both the wild-type and MMP-9KO mice. These data demonstrate that MMP-9 is not required for EPO + G-CSF mobilization and that alternative mobilization mechanisms must be active at clinically relevant cytokine concentrations.

Bone marrow CD34+ progenitor cells in Philadelphia chromosome-negative chronic myeloproliferative disorders – A clinicopathological study on 575 patients

Contrasting the circulating CD34+ hematopoietic progenitor cells (HPCs) in chronic myeloproliferative disorders (CMPDs), scant knowledge is available regarding their quantity in the bone marrow (BM). Therefore, a clinicopathological study was performed on trephine biopsies in 575 patients with CMPDs focused on chronic idiopathic myelofibrosis (CIMF). A comparison with 25 healthy subjects revealed no significant differences in the numbers of HPCs (6 +/- 3/mm2) in polycythemia vera, essential thrombocythemia and advanced fibro-osteosclerotic stages of CIMF. Pre-fibrotic and early-stage CIMF displayed 16 +/- 11 precursors per mm2 BM. Sequential biopsies in this disorder showed a decline in HPCs (10 +/- 6/mm2) with evolving myelofibrosis-myeloid metaplasia (MMM), while in terminal stages acceleration generated an increase (24 +/- 25/mm2). A significant association between the quantity of HPCs and the development of myelofibrosis, splenomegaly, and anemia as well as an increase in peripheral blasts was recognizable in CIMF. Moreover, in all subtypes of CMPDs, a favorable prognosis was significantly associated with a higher number of HPCs in the BM. In conclusion, enhanced inflow of precursors from the BM with subsequent trapping, self-renewal and mobilization by the spleen is assumed to indicate a progressive generalization and worsening of the outcome. This putative pathomechanism is significantly associated with the evolution of MMM.

Increased circulating hematopoietic and endothelial progenitor cells in the early phase of acute myocardial infarction

AbstractEndothelial progenitor cell (EPC) mobilization has been reported following tissue damage, whereas no data are available regarding the mobilization of hematopoietic progenitor cells (HPCs). We performed the phenotypic and functional analysis of circulating CD34+ progenitor cells in patients with acute myocardial infarction (AMI), assessed from admission up to 60 days, in patients with stable angina pectoris (SA), and in healthy controls (CTRLs). In patients with AMI at admission (T0), the number of circulating CD34+ cells was higher (P < .001) than in CTRLs and became comparable with CTRLs within 60 days. Both the number of CD34+ cells coexpressing CD33, CD38, or CD117 and the number of HPCs was higher (P < .02 for all) in patients with AMI at T0 than in CTRLs, as was the number of hematopoietic colonies (P < .03). Patients with AMI (T0) had a significantly increased number of CD34+ vascular endothelial growth factor receptor 2–positive (VEGFR-2+) cells (P < .002) with respect to CTRLs, including CD34+ CD133+VEGFR-2+ and CD34+ CD117+VEGFR-2+ EPCs. The number of endothelial colonies was higher in patients with AMI (T0) than in CTRLs (P < .05). No significant difference was documented between patients with SA and CTRLs. Spontaneous mobilization of both HPCs and EPCs occurs within a few hours from the onset of AMI and is detectable until 2 months.

Regenerating More Than Muscle in Muscular Dystrophy

Duchenne muscular dystrophy (DMD) is a progressive muscle-wasting disorder of skeletal and cardiac muscle. Mutations in the dystrophin gene produce DMD, but much is still unknown about the pathophysiology of DMD. Dystrophic muscle is defined by replacement of normal myofibers by connective tissue and adipocytes. Normal skeletal muscle is highly regenerative and, in the face of continued degeneration, muscle regeneration in DMD is robust, although insufficient to match the pace of degeneration. The dystrophin protein is a subsarcolemmal, spectrin repeat–containing protein of skeletal muscle myofibers and cardiomyocytes. Dystrophin associates tightly with a constellation of transmembrane proteins forming the dystrophin-glycoprotein complex (DGC). Extracellularly, the DGC binds to laminin 2, and intracellularly, the DGC binds to cytoplasmic γ-actin, a myocyte-specific form of filamin and neuronal nitric oxide synthase (nNOS). Positioned at the plasma membrane, the DGC is a mechanosignaling complex that connects the extracellular matrix with the cytoskeleton, and dystrophin is central to this role.1 When dystrophin is absent, as is the case in DMD, the entire DGC is destabilized. The dissolution of the DGC produces plasma membrane instability associated with increased intracellular calcium and myofiber degeneration. See p 3341 The ongoing and widespread muscle degeneration in DMD produces a number of systemic responses. In the present issue of Circulation , Straino and colleagues2 now show that arteriogenesis is enhanced in mdx mice, a mouse model of DMD. Under ischemic conditions, an increase in hindlimb perfusion was seen in mdx as compared with control mice. As an explanation of increased perfusion, muscle from mdx mice was found to have longer arterioles compared with control muscle. Interestingly, capillary density was not increased, and the observed difference in blood flow was attributed solely to arteriole length differences consistent with enhanced arteriogenesis. Given the prominent regeneration that is a feature of mdx muscle, …

Gene expression profiling in CD34 cells to identify differences between aplastic anemia patients and healthy volunteers

AbstractAn immune pathophysiology for acquired aplastic anemia (AA) has been inferred from the responsiveness of the patients to immunosuppressive therapies and experimental laboratory data. To address the transcriptome of hematopoietic cells in AA, we undertook GeneChip analysis of the extremely limited numbers of progenitor and stem cells in the marrow of patients with this disease. We pooled total RNA from highly enriched bone marrow CD34 cells of 36 patients with newly diagnosed AA and 12 healthy volunteers for analysis on oligonucleotide chips. A large number of genes implicated in apoptosis and cell death showed markedly increased expression in AA CD34 cells, and negative proliferation control genes also had increased activity. Conversely, cell cycle progress–enhancing genes showed low expression in AA. Cytokine/chemokine signal transducer genes, stress response genes, and defense/immune response genes were up-regulated, as anticipated from other evidence of the heightened immune activity in AA patients’ marrow. In summary, detailed genetic analysis of small numbers of hematopoietic progenitor cells is feasible even in marrow failure states where such cells are present in very small numbers. The gene expression profile of primary human CD34 hematopoietic stem cells from AA was consistent with a stressed, dying, and immunologically activated target cell population. Many of the genes showing differential expression in AA deserve further detailed analysis, including comparison with other marrow failure states and autoimmune disease.