Subpopulations Of Bone Marrow Cells Research Articles

Abstract 4207: microPET/CT imaging of the mobilization of CD11b+ cells

Abstract Objectives: Mobilization of immune cells is often associated with prognosis and treatment response for many diseases. The objective of this study was to test whether mobilization of CD11b+ myeloid cells could be noninvasively imaged by PET/CT. Methods: Anti-mouse CD11b antibody was labeled with 64Cu. Immunocompetent mice with 12-o-tetradecanoylphorbol-13-acetate (TPA)-induced acute inflammation in the ears, lipopolysaccharide (LPS)-induced inflammation in the lung, mice bearing 3 different syngeneic murine tumors (4T1 mammary carcinoma, CMS4 sarcoma, and CT26 colon carcinoma), and mice bearing ID8 ovarian cancer undergoing photothermal therapy were imaged with [64Cu]-labeled anti-CD11b. microPET-CT imaging and biodistribution were obtained at 24 h after intravenous injection of the radiotracer. Subpopulations of bone marrow cells, cells from spleen, and cells from the disease sites were analyzed by flow cytometry and/or immunohistochemistry (IHC) staining. Results: 64Cu-labeled anti-CD11b bound specifically to CD11b+ myeloid cells. microPET-CT images showed significantly higher uptake of 64Cu-DOTA-anti-CD11b antibody at the inflammatory sites and tumors undergoing photothermal therapy. In addition, microPET-CT images also revealed mobilization of CD11b+ cells from bone marrow to secondary lymphoid organs (spleen and/or lymph nodes). Interestingly, mice bearing 4T1 carcinoma displayed a markedly different imaging/distribution pattern compared to mice bearing CMS4 and CT26 tumors, characterized by a significant increase in blood pool and liver activities with corresponding reduction in the uptake of the radiotracer in the bone marrow and the spleen in different stages of tumor development. These findings were evaluated in the context of flow cytometry and IHC analyses. Conclusions: The differential distribution pattern of 64Cu-labeled anti-CD11b in different disease models could be attributed to mobilization of CD11b+ cells. PET/CT may be used to image systems response of immune cells to disease development and treatments. (Supported in part by the John S. Dunn Foundation) Citation Format: Qizhen Cao, Qian Huang, Chun Li. microPET/CT imaging of the mobilization of CD11b+ cells. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4207.

Bone marrow cell characteristics associated with patient profile and cardiac performance outcomes in the LateTIME-Cardiovascular Cell Therapy Research Network (CCTRN) trial

Although several preclinical studies have shown that bone marrow cell (BMC) transplantation promotes cardiac recovery after myocardial infarction, clinical trials with unfractionated bone marrow have shown variable improvements in cardiac function. To determine whether in a population of post-myocardial infarction patients, functional recovery after BM transplant is associated with specific BMC subpopulation, we examined the association between BMCs with left ventricular (LV) function in the LateTIME-CCTRN trial. In this population, we found that older individuals had higher numbers of BM CD133(+) and CD3(+) cells. Bone marrow from individuals with high body mass index had lower CD45(dim)/CD11b(dim) levels, whereas those with hypertension and higher C-reactive protein levels had higher numbers of CD133(+) cells. Smoking was associated with higher levels of CD133(+)/CD34(+)/VEGFR2(+) cells and lower levels of CD3(+) cells. Adjusted multivariate analysis indicated that CD11b(dim) cells were negatively associated with changes in LV ejection fraction and wall motion in both the infarct and border zones. Change in LV ejection fraction was positively associated with CD133(+), CD34(+), and CD45(+)/CXCR4(dim) cells as well as faster BMC growth rates in endothelial colony forming assays. In the LateTIME population, BM composition varied with patient characteristics and treatment. Irrespective of cell therapy, recovery of LV function was greater in patients with greater BM abundance of CD133(+) and CD34(+) cells and worse in those with higher levels of CD11b(dim) cells. Bone marrow phenotype might predict clinical response before BMC therapy and administration of selected BM constituents could potentially improve outcomes of other future clinical trials.

Long-Term Survivors after Stem Cell Transplantation in Multiple Myeloma: Bone Marrow Minimal Residual Disease, PET/CT and Immunological Status

Abstract Introduction: Multiple myeloma (MM) is considered an incurable disease. Best results are obtained with autologous stem cell transplantation (ASCT). The achievement of complete remission (CR) is the crucial step for a prolonged survival. Unfortunately, even with the use of new regimens, the vast majority of patients will ultimately relapse. In fact, with conventional chemotherapy, ASCT or allogeneic stem-cell transplantation (alloSCT), only 1‰, 10% and 15%, respectively are alive and in continued CR beyond 10 years in the best circumstances. The aim of the present research was to evaluate the proportion of patients in long-term CR after stem-cell transplantation, describing the different aspects related to minimal residual disease (MRD) and immunological correlative studies. Methods: We analyzed the medical records of 160 patients who underwent single melphalan-based ASCT from March 31th 1994 to December 31th 2010, allowing at least 5 years of follow up from diagnosis (median follow-up of 8 years), as well as 58 patients who had received an alloSCT over a 28-year period. Bone marrow (BM) samples from the alive CR patients beyond 5 years were analyzed to assess MRD using multiparameter flow cytometry (MFC) with Euroflow 8-color consensus panel. Serum free-light chains (FLC) and immunoglobulin heavy/light chains (HLC) (The Binding Site) were assayed by immunonephelometry. A whole-body PET/CT (Siemens) was also performed to evaluate extramedullary and bone disease. Furthermore, a detailed panel of surface cell markers by MFC was also developed to evaluate B, T and NK cell compartments, among other immune cell subpopulations in BM and/or peripheral blood. Results: Twenty patients (20/160; 12.5%) were alive and in continuous CR after ASCT beyond 5 years; nine (5.7%) remained in CR for more than 10 years. In the alloSCT group, 6 out 58 patients (10.3%) were in CR beyond 5 years (3 of them for more than 10 years). Remarkably, two patients were in CR after 20 and 28 years after ASCT and alloSCT, respectively. Fourteen long survivors after ASCT (70%) had received maintenance therapy. These regimens were mainly interferon (8 patients), followed by thalidomide (3) or thalidomide plus bortezomib (3). None patient showed increased uptake of FDG by PET/CT suspicious of MM activity, neither in bone lesions nor previous plasmacytomas. However, in the vast majority of patients (16/22; 72.7%) there were stable lytic lesions, usually with sclerotic borders. Unspecific findings, particularly lymph nodes with unspecific FDG uptake, were described in 28.6%. Fourteen out of 20 patients after ASCT (70%) and 2 after alloSCT (33.3%) showed oligoclonal bands (OB) in serum and/or urine, differents from the original monoclonal paraprotein by immunofixation. Among the 22 evaluated patients, all but 2 were negative by MFC for MRD in BM. These two patients were in stable CR, with evidence of OB in serum, considering the clone found unrelated to the original one. The aberrant plasma cell population (CD38+/++, CD56+, CD27-, CD19-, CD45-, CD81-, CD117+) was found to a frequency of 0.09% and 0.004% BM cells. Other 4 patients showed a population of plasma cells with some aberrant markers expression; two of them also showed OB. All patients showed normal serum FLC ratio except one patient after alloSCT. Levels of IgG and IgA HLC were also normal, except in one patient each. Six patients had higher IgM HLC ratio than normal, all of them showing OB. We also investigated whether T cell clonal expansion could be also involved. Indeed, patients with OB showed a higher diversity of TCR Vb over-represented, preferentially 13.1 and 17, suggesting a potential oligoclonal expansion of the T cell response. Characterization of TCR repertoire of the long survivors also indicated a higher involvement of the CD8+ compared to CD4+ T cells. In BM, the expression of the co-inhibitory receptor PD-1 on CD8+ T cells was elevated in active MM compared to MGUS and long survivors suggesting that exhausted PD1+CD8+ T cells increase in active MM and recover to normal levels in long survivors. Conclusions: There are a small proportion of long-term survivors after SCT in MM. MRD studies are negatives, but some false positives could be observed by MFC when OB are present. PET invariably showed metabolic CR with stable bone lesions. Our results support that oligoclonal humoral and cellular responses may play an important role in the disease control over the years. Disclosures No relevant conflicts of interest to declare.

Murine Sca1(+)Lin(-) bone marrow contains an endodermal precursor population that differentiates into hepatocytes.

The direct differentiation of hepatocytes from bone marrow cells remains controversial. Several mechanisms, including transdifferentiation and cell fusion, have been proposed for this phenomenon, although direct visualization of the process and the underlying mechanisms have not been reported. In this study, we established an efficient in vitro culture method for differentiation of functioning hepatocytes from murine lineage-negative bone marrow cells. These cells reduced liver damage and incorporated into hepatic parenchyma in two independent hepatic injury models. Our simple and efficient in vitro protocol for endodermal precursor cell survival and expansion enabled us to identify these cells as existing in Sca1+ subpopulations of lineage-negative bone marrow cells. The endodermal precursor cells followed a sequential developmental pathway that included endodermal cells and hepatocyte precursor cells, which indicates that lineage-negative bone marrow cells contain more diverse multipotent stem cells than considered previously. The presence of equivalent endodermal precursor populations in human bone marrow would facilitate the development of these cells into an effective treatment modality for chronic liver diseases.

Endothelial progenitor cells, defined by the simultaneous surface expression of VEGFR2 and CD133, are not detectable in healthy peripheral and cord blood.

Circulating endothelial cells (CEC) and their progenitors (EPC) are restricted subpopulations of peripheral blood (PB), cord blood (CB), and bone marrow (BM) cells, involved in the endothelial homeostasis maintenance. Both CEC and EPC are thought to represent potential biomarkers in several clinical conditions involving endothelial turnover/remodeling. Although different flow cytometry methods for CEC and EPC characterization have been published so far, none of them have reached consistent conclusions, therefore consensus guidelines with respect to CEC and EPC identification and quantification need to be established. Here, we have carried out an in depth investigation of CEC and EPC phenotypes in healthy PB, CB and BM samples, by optimizing a reliable polychromatic flow cytometry (PFC) panel. Results showed that the brightness of CD34 expression on healthy PB and CB circulating cells represents a key benchmark for the identification of CEC (CD45neg/CD34bright/CD146pos) respect to the hematopoietic stem cell (HSC) compartment (CD45dim/CD34pos/CD146neg). This approach, combined with a dual-platform counting technique, allowed a sharp CEC enumeration in healthy PB (n = 38), and resulting in consistent CEC counts with previously reported data (median = 11.7 cells/ml). In parallel, by using rigorous PFC conditions, CD34pos/CD45dim/CD133pos/VEGFR2pos EPC were not found in any healthy PB or CB sample, since VEGFR2 expression was never detectable on the surface of CD34pos/CD45dim/CD133pos cells. Notably, the putative EPC phenotype was observed in all analyzed BM samples (n = 12), and the expression of CD146 and VEGFR2, on BM cells, was not restricted to the CD34bright compartment, but also appeared on the HSC surface. Altogether, our findings suggest that the previously reported EPC antigen profile, defined by the simultaneous expression of VEGFR2 and CD133 on the surface of CD45dim/CD34pos cells, should be carefully re-evaluated and further studies should be conducted to redefine EPC features in order to translate CEC and EPC characterization into clinical practice.

Depletion of Bone Marrow CCSP-Expressing Cells Delays Airway Regeneration

The contribution of bone marrow cells (BMC) in lung repair is controversial. We previously reported a subpopulation of BMC that express Clara cell secretory protein (CCSP). To determine the contribution of endogenous CCSP(+) BMC to airway regeneration, we performed bone marrow transplantation studies using the CCtk mouse, which expresses a thymidine kinase suicide gene under regulation of the CCSP promoter. Mice were transplanted with wild-type or CCtk BMC and treated with ganciclovir to eliminate CCSP(+) cells. After airway injury using naphthalene, mice depleted of CCSP(+) BMC had more inflammatory cells in lung and decreased levels of oxygen in arterial blood. They also had reduced expression of airway epithelial genes and less Clara cells compared to control mice that had intact CCSP(+) BMC and bone marrow derived CCSP(+) cells in the airways. After naphthalene injury, administration of CCSP reproduced the beneficial effect of CCSP(+) BMC by improving recovery of airway epithelium, reducing lung inflammation and increasing oxygen in arterial blood from mice depleted of CCSP(+) BMC. Our data demonstrate that ablation of CCSP(+) BMC delays airway recovery and suggests the beneficial effect of CCSP(+) BMC in lung recovery is in part due to production of CCSP itself.

Selective Migration of Subpopulations of Bone Marrow Cells along an SDF-1α and ATP Gradient.

Both stem cell chemokine stromal cell-derived factor-1α (SDF-1α) and extracellular nucleotides such as adenosine triphosphate (ATP) are increased in ischemic myocardium. Since ATP has been reported to influence cell migration, we analysed the migratory response of bone marrow cells towards a combination of SDF-1 and ATP. Total nucleated cells (BM-TNCs) were isolated from bone marrow of cardiac surgery patients. Migration assays were performed in vitro. Subsequently, migrated cells were subjected to multicolor flow cytometric analysis of CD133, CD34, CD117, CD184, CD309, and CD14 expression. BM-TNCs migrated significantly towards a combination of SDF-1 and ATP. The proportions of CD34+ cells as well as subpopulations coexpressing multiple stem cell markers were selectively enhanced after migration towards SDF-1 or SDF-1 + ATP. After spontaneous migration, significantly fewer stem cells and CD184+ cells were detected. Direct incubation with SDF-1 led to a reduction of CD184+ but not stem cell marker-positive cells, while incubation with ATP significantly increased CD14+ percentage. In summary, we found that while a combination of SDF-1 and ATP elicited strong migration of BM-TNCs in vitro, only SDF-1 was responsible for selective attraction of hematopoietic stem cells. Meanwhile, spontaneous migration of stem cells was lower compared to BM-TNCs or monocytes.

Elucidating the Role of the Endocytic Protein Ap2a2 in Haematopoiesis

The rare subpopulation of quiescent HSCs exists in limited numbers but upon in vivo requirement have the highest proliferative potency. Self-renewal via asymmetrical cell division (ACD) is vital for maintenance of HSC numbers and perturbation of this process can lead to an impaired hematopoietic system, with subsequent blood diseases such as acute leukemia and/or bone marrow failure. How and which HSCs are programmed for ACD remain central and unanswered questions. We have demonstrated that the endocytic protein, Ap2a2 distinguishes an asymmetrical from a symmetrical cell division during HSC mitoses, and when overexpressed enhances mouse HSC activity.Ap2a2 is a component of the Adaptor protein 2 complex that functions in clathrin-dependent endocytosis of receptors and nutrient cargo.The tetracycline-induceable H2B-GFP mouse (Foudi A. et al, Nature Biotech 2009) has revealed functional heterogeneity within the CD150+48- Lin-Sca+Kit+(LSK) HSC population, such that the GFPhigh subpopulation within the CD150+48- LSK is the true Long-Term repopulating HSCs (GFPhigh LT-HSCs). Using this mouse, we have shown that Ap2a2 is not only more highly expressed in the GFPhigh LT-HSCs but that Ap2a2 overexpression increases the fraction of this specific subpopulation from 20% to 60% at plus 20 weeks post-transplantation. To identify novel genes and pathways driving LT-HSC function and self-renewal, we are currently performing comparative gene expression analyses from the subpopulation of Ap2a2-transduced against control, vector-transduced GFPhighCD150+48-LSK LT-HSCs.To further investigate Ap2a2 in haematopoiesis, we have constructed an Ap2a2 conditional knockout mouse (Ap2a2 cKO) line, which has a LacZ reporter expressed from the endogenous Ap2a2 promoter. Our initial expression analyses with tissue LacZ staining shows relative increased staining in subpopulations of bone marrow cells and using a β-galactosidase (β-gal) flow cytometry method co-stained with CD150+48-LSK, have identified β-galhigh and β-gallow subpopulations. This suggests Ap2a2 expression may be an independent marker of LT-HSCs, which we are functionally assessing via comparative LSK -β-galhigh versus -β-gallow versus -β-galnegative transplantation assays. The specific function of Ap2a2 in developmental (Vav-Cre) and adult (Mx-Cre) haematopoiesis is being investigated by respective tissue specific-Cre matings with the Ap2a2fl/flmice.Mechanistically, a recent publication (Ito K. et al, Nature Med 2012) identified the importance of PPAR-δ/β-fatty acid oxidation regulation for both maintenance and ACD ofHSCs. Ap2a2 is a target of PPAR-α (Buroker N. et al Protein J 2012). Our hypothesis states that the role of Ap2a2 in LT-HSCs involves the lipid metabolic pathway, which would uniquely link endocytosis to metabolism. To this end, using our Ap2a2-LacZ reporter mouse, we have shown intense and specific LacZ expression in adipocytes of the bone marrow and other lipid containing organs. In addition, perturbation of Ap2a2 results in altered lipid droplet formation and impaired triacylgylceride storage. We are currently investigating the oxidative phosphorylation, anaerobic glycolysis and fatty acid metabolic effects in the context of altered Ap2a2 expression. DisclosuresNo relevant conflicts of interest to declare.

Thrombopoietin/MPL signaling confers growth and survival capacity to CD41-positive cells in a mouse model of Evi1 leukemia

AbstractEcotropic viral integration site 1 (Evi1) is a transcription factor that is highly expressed in hematopoietic stem cells and is crucial for their self-renewal capacity. Aberrant expression of Evi1 is observed in 5% to 10% of de novo acute myeloid leukemia (AML) patients and predicts poor prognosis, reflecting multiple leukemogenic properties of Evi1. Here, we show that thrombopoietin (THPO) signaling is implicated in growth and survival of Evi1-expressing cells using a mouse model of Evi1 leukemia. We first identified that the expression of megakaryocytic surface molecules such as ITGA2B (CD41) and the THPO receptor, MPL, positively correlates with EVI1 expression in AML patients. In agreement with this finding, a subpopulation of bone marrow and spleen cells derived from Evi1 leukemia mice expressed both CD41 and Mpl. CD41+ Evi1 leukemia cells induced secondary leukemia more efficiently than CD41− cells in a serial bone marrow transplantation assay. Importantly, the CD41+ cells predominantly expressing Mpl effectively proliferated and survived on OP9 stromal cells in the presence of THPO via upregulating BCL-xL expression, suggesting an essential role of the THPO/MPL/BCL-xL cascade in enhancing the progression of Evi1 leukemia. These observations provide a novel aspect of the diverse functions of Evi1 in leukemogenesis.

AB0023 In Vivo Effects of Epratuzumab, A Monoclonal Antibody Targeting Human CD22, on B Cell Function in Human CD22 Knock-In (HUKI) Mice

BackgroundEpratuzumab is a humanized monoclonal antibody that targets the B cell-specific protein CD22 and is currently in Phase 3 clinical trials in patients (pts) with systemic lupus erythematosus (SLE). Epratuzumab...

CXCR4+ and SDF-1+ Bone Marrow Cells Are Mobilized into the Blood Stream in Acute Myocardial Infarction and Acute Ischemia

Cell therapy has shown beneficial effects on ventricular function and tissue regeneration in patients with acute and chronic myocardial infarction, although with diverse grades of variability in the results, possibly by proportion, subtype and cell cycle status. Objective: Identify and phenotypically characterize, via CXCR4 and SDF-1 expression, the bone marrow cell subpopulations that are mobilized into the bloodstream in patients with Acute Myocardial Infarction (AMI) and Acute Ischemia (AI) such as acute angina and Chronic Ischemia (CI) such as chronic stable angina, and also determine the cell cycle status of these cells. Method: Patients with AMI and AI were recruited in the ICCU, and patients with CI in the departments of cardiology and cardiovascular surgery. The quantification of cellular subpopulations was made by cytofluorometry with a FACS caliburcyto fluorometry (Becton Dickinson) with specific FITC-labeled anti human monoclonal antibodies against CD34, CD133, CD117, CD48, CXCR4, SDF-1 and Ki67 (Becton Dickinson). Serum concentration of IL-6 and IL-8 were determined by a sequential solid phase chemiluminescent assay performed in a SIEMENS IMMULITE 1000 Analyzer. Statistical analysis was made with the SPSS version 20.0 for Windows. A p value 3/ml) than that in AI (9.2 ± 1.3 × 103/ml) and CI (6.6 ± 1.1 × 103/ml) patients (p p = 0.22 to 0.39), but interestingly in AMI and AI patients, cells were CXCR4+ in almost half of these mobilized cells, although the proportion was significantly higher in AMI patients (46.8% ± 7.1% to 55.7% ± 6.3% vs 23% ± 1.6% to 28.4% ± 2.1%, p = 0.03 to 0.05). A similar behavior was observed with the Ki67 antibody (29.9% ± 2.1% to 36.1% ± 6.3% vs 10% ± 1.2% to 24% ± 1.1%, p = 0.001 to 0.05). Bivariate analysis of the results showed a significant correlation of the cell proportion in AMI but not in AI and CI patients (p = 0.001 to 0.05; 0.12 to 0.87 and 0.17 to 0.92 respectively). The amount of myocardial tissue infarcted did not show any correlation with the amount of cellular subpopulations mobilized to peripheral blood (r = 0.10 to 0.20; p = 0.21 to 0.64) from the bone marrow. Conclusion: The proportion of cellular subpopulations with regenerative potential mobilized to circulation during an event of Acute Myocardial Infarction is significantly higher than during an event of acute angina and chronic stable angina, with a significant proportion of mobilized cells that expressed CXCR4, most of which were already in some of the cell cycle phases.

Polymorphism nt7778G/T In Mitochondrial ATP8 Gene Promotes Protective Effect On Reactive Oxygen Species Level In Murine Hematopoietic Cells During Aging

Mitochondria are complex cell compartments characterized by a nuclear genome independent own genome referred to as mitochondrial genome (mtDNA). MtDNA encodes 13 proteins which are part of the five enzyme complexes of the mitochondrial respiratory chain. The respiratory chain is responsible for ATP synthesis and is the main source of reactive oxygen species (ROS) in the cell. During cellular aging, mutations in mtDNA accumulate leading potentially to respiratory chain deficiency. Due to the lack of DNA repair mechanisms within the mitochondrion itself, the mtDNA is especially vulnerable towards ROS. Until now it is not fully understood whether intracellular ROS levels increase with aging in all cell types, and whether this process is due to a potential impaired function of the respiratory chain. Thus, the influence of mtDNA mutations on oxidative stress and aging of hematopoietic cells remains to be investigated. Herein, we compared two conplastic mouse strains differing in one point mutation in the mtDNA affecting the respiratory chain. The C5BL/6Ntac-mtFVB/NJ (mtFVB) strain carries a point mutation at nt7778G/T leading to a D>Y replacement in ATP8 protein, while the control stain C5BL/6Ntac-mtAKR (mtAKR) does not. The targeted protein is part of the F0sub unit of complex V in the respiratory chain and we hypothesize that the mutation affects the transport of protons within the complex V.In our study, we analyzed bone marrow cells of both strains at four different aging stages (3 to 24 months) for ROS and ATP levels by DCFH-fluorescence and luminescence staining, respectively. Additionally, the subpopulations of bone marrow cells were analyzed by flow cytometric immunophenotyping. Further, blood counts of the mice treated with a single dose of 5 Fluorouracil (5-FU, 150mg/kg BW, i.p.) were performed every 3 days during a total time span of 21 days.The mtAKR strain showed increasing levels of ROS ranging from 7.1 x 103 to 12 x 103 relative fluorescence units (RFU) and decreasing levels of ATP (from 0.99 to 0.36 µM) during the measurement time points 3 to 24 months. In comparison, the mtFVB strain showed a significant decrease in ROS levels ranging from 5.5 x 103 to 2.4 x 103 RFU and a significant increase of ATP levels (from 0.23 to 0.64 µM) during the same period. Hematopoietic cells of aged mtFVB mice (24 months) contained significantly more ATP than cells of mtAKR mice. Analysis of bone marrow cell composition of both strains showed an increase of hematopoietic stem cells (LSK cells: lineage-, sca-1+, c-kit+) during experimental time span from 3 to 24 months (mtAKR: from 2.13 to 2.81 % of lineage- cells, mtFVB: from 2.13 to 3.52 %). However, only in the mtFVB strain this increase was significant. Interestingly, the amount of LSK cells was significant higher in mtFVB compared to the mtAKR strain (mtFVB: 2.36 %, mtAKR: 1.23 %) at 6 months. Furthermore, erythroide cells (Ter119+) in mtAKR increased with aging (from 25.22 % to 32.69 %), while the mtFVB strain showed a decreased rate (from 25.88 % to 18.9 %).Blood counts of 3 months old mtFVB mice treated with 5-FU were similar to those of the mtAKR strain in the myelosuppression phase after application, but demonstrated higher regeneration peaks at day 15 in white blood cells (mtAKR: 20.24 x 103/µl, mtFVB: 25.72 x 103/µl), platelets (mtAKR: 2016 x 103/µl, mtFVB: 2848 x 103/µl), neutrophilic (mtAKR: 0.8 x 103/µl, mtFVB: 2.36 x 103/µl) and eosinophilic granulocytes (mtAKR: 0.28 x 103/µl, mtFVB: 0.76 x 103/µl) and lymphocytes (mtAKR: 17.12 x 103/µl, mtFVB: 21.84 x 103/µl).The mtDNA polymorphism in complex V of the respiratory chain in mtFVB strain influences the development of ROS and ATP levels in hematopoietic cells during aging, and seems to have a protective impact concerning ROS and ATP levels in aged mice. Furthermore, the capability of LSK cells to expand with age seems to be enhanced in mtFVB strain. Moreover, the regeneration capacity after 5-FU myelosuppression seems also to be increased in 3 months old mice. Disclosures:No relevant conflicts of interest to declare.

A small interfering RNA targeting Lnk accelerates bone fracture healing with early neovascularization

Lnk, an intracellular adapter protein, is expressed in hematopoietic cell lineages, which has recently been proved as an essential inhibitory signaling molecule for stem cell self-renewal in the stem cell factor-c-Kit signaling pathway with enhanced hematopoietic and osteogenic reconstitution in Lnk-deficient mice. Moreover, the therapeutic potential of hematopoietic stem/endothelial progenitor cells (EPCs) for fracture healing has been demonstrated with mechanistic insight into vasculogenesis/angiogenesis and osteogenesis enhancement in the fracture sites. We report here, Lnk siRNA-transfected endothelial commitment of c-kit+/Sca-1+/lineage− subpopulations of bone marrow cells have high EPC colony-forming capacity exhibiting endothelial markers, VE-Cad, VEGF and Ang-1. Lnk siRNA-transfected osteoblasts also show highly osteoblastic capacity. In vivo, locally transfected Lnk siRNA could successfully downregulate the expression of Lnk at the fracture site up to 1 week, and radiological and histological examination showed extremely accelerated fracture healing in Lnk siRNA-transfected mice. Moreover, Lnk siRNA-transfected mice exhibited sufficient therapeutic outcomes with intrinstic enhancement of angiogenesis and osteogenesis, specifically, the mice demonstrated better blood flow recovery in the sites of fracture. In our series of experiments, we clarified that a negatively regulated Lnk system contributed to a favorable circumstance for fracture healing by enhancing vasculogenesis/angiogenesis and osteogenesis. These findings suggest that downregulation of Lnk system may have the clinical potential for faster fracture healing, which contributes to the reduction of delayed unions or non-unions.

Suppression of Cytochrome P450 Reductase Enhances Long-Term Hematopoietic Stem Cell Repopulation Efficiency in Mice

BackgroundBone marrow microenvironment (niche) plays essential roles in the fate of hematopoietic stem cells (HSCs). Intracellular and extracellular redox metabolic microenvironment is one of the critical factors for the maintenance of the niche. Cytochrome P450 reductase (CPR) is an obligate electron donor to all microsomal cytochrome P450 enzymes (P450 or CYP), and contributes to the redox metabolic process. However, its role in maintaining HSCs is unknown.ObjectiveTo examine the effects of low CPR expression on HSCs function using a mouse model of globally suppressed Cpr gene expression (Cpr Low, CL mice).MethodsHematopoietic cell subpopulations in bone marrow (BM) and peripheral blood (PB) from WT and CL mice were examined for their repopulation and differentiation ability upon BM competitive transplantation and enriched HSC (LKS+) transplantation. Effects of low CPR expression on hematopoiesis were examined by transplanting normal BM cells into CL recipients. Reactive oxygen species (ROS), cell cycle, and apoptosis in CL mice were analyzed by flow cytometry for DCF-DA fluorescence intensity, Ki67 protein, and Annexin-V, respectively.ResultsThe levels of ROS in BM cells, HPCs and HSCs were comparable between CL and WT mice. In comparison to WT mice, the number of LT-HSCs or ST-HSCs was lower in CL mice while CMPs, GMPs and MEPs in CL mice were higher than that in WT control. Competitive transplantation assay revealed enhanced repopulation capacity of HSCs with low CPR expression, but no difference in differentiation potential upon in vitro experiments. Furthermore, lymphoid differentiation of donor cells decreased while their myeloid differentiation increased under CL microenvironment although the overall level of donor hematopoietic repopulation was not significantly altered.ConclusionsOur studies demonstrate that suppressing CPR expression enhances the repopulation efficiency of HSCs and a low CPR expression microenvironment favors the differentiation of myeloid over lymphoid lineage cells.

Bone Marrow Cells Expressing Clara Cell Secretory Protein Increase Epithelial Repair After Ablation of Pulmonary Clara Cells

We have previously reported a subpopulation of bone marrow cells (BMC) that express Clara cell secretory protein (CCSP), generally felt to be specific to lung Clara cells. Ablation of lung Clara cells has been reported using a transgenic mouse that expresses thymidine kinase under control of the CCSP promoter. Treatment with ganciclovir results in permanent elimination of CCSP+ cells, failure of airway regeneration, and death. To determine if transtracheal delivery of wild-type bone marrow CCSP+ cells is beneficial after ablation of lung CCSP+ cells, transgenic mice were treated with ganciclovir followed by transtracheal administration of CCSP+ or CCSP− BMC. Compared with mice administered CCSP− cells, mice treated with CCSP+ cells had more donor cells lining the airway epithelium, where they expressed epithelial markers including CCSP. Although donor CCSP+ cells did not substantially repopulate the airway, their administration resulted in increased host ciliated cells, better preservation of airway epithelium, reduction of inflammatory cells, and an increase in animal survival time. Administration of CCSP+ BMC is beneficial after permanent ablation of lung Clara cells by increasing bronchial epithelial repair. Therefore, CCSP+ BMC could be important for treatment of lung diseases where airways re-epithelialization is compromised.

Nicotinic Receptor Alpha7 Expression Identifies a Novel Hematopoietic Progenitor Lineage

How inflammatory responses are mechanistically modulated by nicotinic acetylcholine receptors (nAChR), especially by receptors composed of alpha7 (α7) subunits, is poorly defined. This includes a precise definition of cells that express α7 and how these impact on innate inflammatory responses. To this aim we used mice generated through homologous recombination that express an Ires-Cre-recombinase bi-cistronic extension of the endogenous α7 gene that when crossed with a reporter mouse expressing Rosa26-LoxP (yellow fluorescent protein (YFP)) marks in the offspring those cells of the α7 cell lineage (α7lin+). In the adult, on average 20–25 percent of the total CD45+ myeloid and lymphoid cells of the bone marrow (BM), blood, spleen, lymph nodes, and Peyers patches are α7lin+, although variability between litter mates in this value is observed. This hematopoietic α7lin+ subpopulation is also found in Sca1+cKit+ BM cells suggesting the α7 lineage is established early during hematopoiesis and the ratio remains stable in the individual thereafter as measured for at least 18 months. Both α7lin+ and α7lin– BM cells can reconstitute the immune system of naïve irradiated recipient mice and the α7lin+:α7lin– beginning ratio is stable in the recipient after reconstitution. Functionally the α7lin+:α7lin– lineages differ in response to LPS challenge. Most notable is the response to LPS as demonstrated by an enhanced production of IL-12/23(p40) by the α7lin+ cells. These studies demonstrate that α7lin+ identifies a novel subpopulation of bone marrow cells that include hematopoietic progenitor cells that can re-populate an animal’s inflammatory/immune system. These findings suggest that α7 exhibits a pleiotropic role in the hematopoietic system that includes both the direct modulation of pro-inflammatory cell composition and later in the adult the role of modulating pro-inflammatory responses that would impact upon an individual’s lifelong response to inflammation and infection.

Colony-Stimulating Factor-1-Responsive Macrophage Precursors Reside in the Amphibian (Xenopus laevis) Bone Marrow rather than the Hematopoietic Subcapsular Liver

Macrophage precursors originate from and undergo lineage commitment within designated sites of hematopoiesis, such as the mammalian bone marrow. These cells subsequently differentiate in response to stimulation with macrophage colony-stimulating factor-1 (CSF-1). The amphibian bone marrow, unlike that of mammals, has been overlooked as a source of leukocyte precursors in favor of the liver subcapsular region, where hematopoiesis occurs in anurans. Here we report that the bone marrow rather than the liver periphery provides macrophage progenitors to the amphibian Xenopus laevis. We identified the amphibian CSF-1, examined its gene expression in developing and virally infected X. lae vis and produced it in recombinant form (rXlCSF-1). This rXlCSF-1 did not bind or elicit proliferation/differentiation of subcapsular liver cells. Surprisingly, a subpopulation of bone marrow cells engaged this growth factor and formed rXlCSF-1 concentration-dependent colonies in semisolid medium. Furthermore, rXlCSF-1-treated bone marrow (but not liver) cultures comprised of cells with characteristic macrophage morphology and high gene expression of the macrophage marker CSF-1 receptor. Together, our findings indicate that in contrast to all other vertebrates studied to date, committed Xenopus macrophage precursor populations are not present at the central site of hematopoiesis, but reside in the bone marrow.

The Usefulness of CD71 Expression by Flow Cytometry in the Diagnosis of Acute Leukemia.

Abstract 2533CD71 (transferring receptor 1) is an integral membrane glycoprotein that plays an important role in cellular uptake of iron. It is well known as a marker for cell proliferation and activation. Although all proliferating cells in hematopoietic system express CD71, however, CD71 has been considered as a useful erythroid-associated antigen. The expression proportion on nucleated red blood cells was significantly higher than other cells, approximately 80% of all CD71 positive cells were of CD71 positive erythroid cells in normal bone marrow. CD71 was usually considered as the representative marker for differentiating erythroblasts and diagnosing acute erythroid leukemia (AEL) by flow cytometry. At the ISAC 2000 Congress, most experts agreed that at least one or more B, T, myeloid, erythroid and megakaryocytic reagents should be included in the essential panel. The reagents recommended for erythroid cells included CD36, CD71 and glycophorin A (GlyA). However, there was no agreement on how to choose and group these antibodies. In the practical analysis of immune phenotypes of leukemic cells we noted that no CD71 expression was detected on blasts of some cases of AEL with typical morphological and cytochemical findings, but other types of acute myeloblastic leukemia (AML) cells may express CD71. Thus, we speculated that CD71 expression may associate with the abnormal antigen expression resulting from hematopoietic disorders. In this study, we evaluated CD71 expression on different acute leukemia cells in association with a variety of other antibodies. In this study we aimed to define CD71 as a flow cytometric marker for the diagnosis of acute leukemia.Bone marrow samples were collected from 82 newly diagnosed acute leukemia patients as well as 13 normal controls. The diagnosis were made according to the WHO 2008 diagnostic criteria. All 6 cases of AEL were erythroid/myeloid subtype (acute erythroid/myeloid leukemia, M6a). The samples were then analyzed using a four-color flow cytometer with antibody panels against a variety of lymphoid, myelomonocytic, erythroid and megakaryocytic antigens. The antibodies included anti-CD3, CD7, CD10, CD11b, CD13, CD14, CD15, CD16, CD19, CD20, CD33, CD34, CD45, CD56, CD61, CD64, CD71, CD117, GlyA, HLA-DR, IgG, IgM, MPO. Subpopulations of bone marrow cells were gated based on CD45 intensities and side scatter (SSC) value to further analyze the expression of antigens in different cell populations.Positive CD71 expression were identified on bone marrow blast cells of 41 (50%) acute leukemia patients and 9 (69.23%) normal controls. The mean expression level on normal controls was 35.99±19.06%. The mean CD71 expression level on blasts of AML with blasts differentiation at early stage of myelopoiesis (including FAB-M0/M1/M2/M4) was significantly higher than AML with partial differentiation of leukemic cells (FAB-M3/M5) and acuteB lymphoblastic leukemia (B-ALL) (p<0.05), with the mean expression level of 38.78±26.65%, 13.25±8.75% and 10.12±11.65%, respectively, and the latter two lower than normal controls (p<0.05). The percentage of CD71 expression level on blasts of acute megakaryocytic leukemia (FAB-M7) was 80.16±8.23%, significantly higher than normal controls, partial differentiation of leukemic cells (FAB-M3/M5), and B-ALL (p<0.05). The percentage of CD71 expression level on blasts of mixed lineage leukemia was 49.66±22.69%, significantly higher than B-ALL (p<0.05). Positive CD71 expression was found on bone marrow blast cells of 4 (66.67%) AEL cases, with the mean level percentage of 25.68±11.63% that was significantly lower than acute megakaryocytic leukemia (FAB-M7) (p<0.05) and was indifferent from normal controls and other types of acute leukemia. Using CD71 expression levels, we identified different abnormal cell clones simultaneously existing within bone marrow of 2 patients of AML with maturation (FAB-M2) and AEL, implicating the clonal evolution process from normal blasts to leukemic cells.CD71 is an important marker for diagnosing acute leukemia, and is useful for distinguishing the differentiation stages of AML. However, CD71 may not be the specific diagnostic marker for AEL. CD71 is also valuable for the observation of clonal evolution process of acute leukemia, which may be informative to the etiology of leukemia. Disclosures:No relevant conflicts of interest to declare.

Stem Cell Recruitment After Injury: Lessons for Regenerative Medicine

Tissue repair and regeneration are thought to involve resident cell proliferation as well as the selective recruitment of circulating stem and progenitor cell populations through complex signaling cascades. Many of these recruited cells originate from the bone marrow, and specific subpopulations of bone marrow cells have been isolated and used to augment adult tissue regeneration in preclinical models. Clinical studies of cell-based therapies have reported mixed results, however, and a variety of approaches to enhance the regenerative capacity of stem cell therapies are being developed based on emerging insights into the mechanisms of progenitor cell biology and recruitment following injury. This article discusses the function and mechanisms of recruitment of important bone marrow-derived stem and progenitor cell populations following injury, as well as the emerging therapeutic applications targeting these cells.

Ca2+/NFAT Signaling Regulates the Expression CD38 and ZAP70 in Murine B Cells and Controls B1a Cell Homeostasis

Abstract 183NFAT is a family of highly phosphorylated proteins residing in the cytoplasm of resting cells. Upon dephosphorylation by calcineurin, NFAT proteins translocate to the nucleus where they orchestrate developmental and activation programs in diverse cell types. NFAT is inactivated and relocated to the cutoplasm by a network of several kinases including CK-1, GSK-3 and DYRK. Although identified originally as a major transcriptional regulator in T cells, it is now clear that NFAT transcription factors also possess important roles in other cells of the hematopoietic system including dendritic cells, mast cells, megakaryocytes and B cells.Here we have analyzed the role of NFAT2 in B cell development. Analysis of the role of this family member in hematopoiesis has been complicated by the fact that deletion of this gene is embryonic lethal around ED 13 because of defects in heart valve development. To circumvent this problem we generated mice with a conditional NFAT2 knock out allele (NFAT2fl/fl). In order to achieve NFAT2 deletion limited to the B cell lineage, we bred NFAT2fl/fl mice to CD19-Cre mice, in which the Cre recombinase is expressed under the control of the B cell-specific cd19 promoter.B cells from these mice were isolated using CD19-labeled magnetic beads and subjected to analysis by flow cytometry. While CD19+ splenocytes from conditional NFAT2 knock-out mice occurred in normal numbers, these cells showed significantly reduced expression of CD38 and ZAP70 upon stimulation with anti-IgM antibody as compared to CD19+ splenocytes from wild-type controls. The reduction of these proteins could also be detected in B cells isolated from the peripheral blood and from bone marrow and was confirmed by western blotting and quantitative RT-PCR. CD38 and ZAP70 are well characterized prognostic factors in chronic lymphocytic leukemia (CLL) and their increased expression has been shown to correlate with poor patient survival. Our data indicate that the expression of these markers is at least in part regulated by Ca2+/NFAT signaling and that deregulation of this pathway can contribute to their overexpression in disease.Next we analyzed bone marrow and peritoneal lavages from conditional NFAT knock-out mice by flow cytometry. While we found no significant differences in the abundance of B cell subpopulations in bone marrow, we detected an almost complete absence of CD5+CD43+ B1a cells in the peritoneal cavity, clearly demonstrating the requirement of NFAT2 in the development of this subclass. B1a cells are a phenotypically and functionally distinct population of B cells which are long-lived and typically express CD5, CD43 and high levels of surface IgM together with low surface IgD and CD45 (B220). A human B cell equivalent of the murine B1a cell has been suggested as the leukemic precursor cell in chronic lymphocytic leukemia (CLL). To further delineate the role of NFAT2 in the development of B1a cells we determined the abundance of B1 progenitor cells (B1P) in bone marrow and spleen by FACS analysis. In NFAT2 knock-out mice we observed a significant reduction of the frequency of B220- CD19+ CD93+ B1P cells in bone marrow (0.8% vs. 4.7%) and spleen (0.16% vs. 0.82%) demonstrating that NFAT2 is essential for normal development of this precursor cell population.In summary, our data provide strong evidence that NFAT2 is critical for the expression of CD38 and ZAP70 in B cells and substantially controls B1a cell homeostasis implicating Ca2+/NFAT signaling as a potential target for the treatment of CLL. Disclosures:No relevant conflicts of interest to declare.