Marrow-derived Progenitor Research Articles

Abstract 5765: Tumor-elicited myeloid progenitors promote metastasis through induction of mesenchymal to epithelial transition

Abstract Malignant primary tumor cells colonize in target organs to form dormant micrometastasis. In some cases, the micrometastases progress to macrometastasis resulting in more than 90% of human cancer related deaths. However, the cellular and molecular regulators of metastatic initiation and progression remains poorly understood. Using a variety of metastatic tumor models we show that recruited bone marrow-derived myeloid progenitor cells comprise a significant fraction of the metastatic lung as compared to the primary tumor that predominantly have infiltrated macrophages. Specific depletion of the myeloid progenitor cells did not affect primary tumor growth but significantly impaired lung metastases. Global gene expression profiling of the CD11b+GR1+ myeloid progenitor cells identified potential pro-metastatic mediators. We have characterized one such mediator that promotes lung metastasis via promoting mesenchymal to epithelial transition (MET) of disseminated tumor cells. Our data suggests that this transition favors enhanced proliferation and survival of disseminated tumor cells so that they can successfully form functional metastases. RNAi-mediated acute suppression of this mediator in the bone marrow markedly inhibited lung metastases. Taken together, these findings illustrate the critical roles of the myeloid progenitors in metastasis and suggest the potential impact of targeting bone marrow cells and MET pathways in metastatic disease. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 5765.

Endothelial Dysfunction in the Perioperative Setting

Although perioperative macrovascular events (eg, myocardial infarction, stroke) are readily evident, their absolute incidence remains relatively low. In contrast, microvascular dysfunction and its role in perioperative morbidity is not easily measured. Microvascular dysfunction is likely to have a greater impact on noncardiovascular complications (eg, wound healing and end-organ failure), through impaired perfusion, than that which is readily appreciated. Inflammation and oxidative stress, such as that induced by surgical trauma, disrupts endothelial homeostasis thereby decreasing the bioavailability of nitric oxide. This predisposes blood vessels to vasoconstriction, inflammation, leukocyte adhesion, thrombosis-factors that contribute to perioperative cardiovascular events at both macrovascular and microvascular level. Current clinical strategies applicable to the perioperative setting that improve microvascular health include preoperative exercise therapy, pharmacologic interventions (eg, statins, newer beta-blockers) and attempts to stimulate mobilization and homing of bone marrow-derived endothelial progenitor cells. Many of these strategies are still in their infancy and large prospective trials that investigate the impact of these therapeutic options on postoperative outcome are eagerly awaited.

A Novel Role of Estrogen in Diabetic Wound Healing: Improved Function of Bone Marrow-Derived Endothelial Progenitor Cells

A Novel Role of Estrogen in Diabetic Wound Healing: Improved Function of Bone Marrow-Derived Endothelial Progenitor Cells

In vivo implantation of a functional tissue engineered stentless pulmonary valve using bone-marrow-derived mesenchymal stem cells and circulating endothelial progenitor cells

Purpose: We investigated the functional potential of poly-4-hydroxybutyrate (P4HB) scaffolds by determining the most suitable thickness and ratio of co-cultured progenitor cells for construction of pulmonary leaflets and annular sewing ring in tissue engineered (TE) stentless PV. Methods: Melt-blown fibronectin (FN)-coated P4HB scaffolds of varying thickness were seeded with different percentages of characterized ovine bone marrow-derived mesenchymal stem cells (MSC) and peripheral blood-derived endothelial progenitor cells (EPC) for 21 days in a laminar flow system. Results: HE α-SMA+ cells were found both on the surface and in the interstitium evidenced by IHC. Immunoblotting revealed increased expression of α-SMA+. Hence, autologous TE stentless PV using 220µM for PV leaflet covered with 100µM for annular sewing ring was successfully placed in PV position. The neo-tissue integrity allowed secure anastomosis with adequate tensile strength. Echocardiography demonstrated normal biventricular function, and adequate leaflet coaptation with trivial central regurgitation. Conclusion: This demonstrates the successful creation of an anatomically functional, autologous TE stentless PV using sequentially seeded progenitor cell sources. This suggest the importance of scaffold thickness and ratio of seeded cells in the suturability of TE stentless PV.

Preliminary Study of Pre-Metastatic Niche (PMN) in Nonmetastatic Nodes for the Assessment of Metastasis Risk in Breast Cancer (BC).

Abstract Bone marrow-derived hematopoietic progenitor cells (HPCs) seem to participate in early spread of cancer cells by forming a peculiar and highly organized micro-environment called PMN. Identifying such HPCs in the PMNs is emerging as a key step in assessing risk of metastasis.In this preliminary study we analysed 294 axillar nodes (271 pN0 and 23 pN1a) obtained from 30 pts undergone surgery for breast ductal invasive carcinoma in the period 1998-2000.Pts mean age was 61.2 years (range 45-79); 9 pts (30%) were premenopausal and 21 (70%) postmenopausal; 13 pts (43.3%) had ER+, 10 (33.3%) PR+; MIB1 was ≤ 25% in 22 pts (73.3%), >25% in 6 (20%), unknown in 2 pts. After a median follow-up of 81.27 mos (range 12–136), 14 pts are disease-free, 9 pts dead of metastatic disease. Involved sites were: 1 loco-regional, 7 bone, 3 lung, 4 liver, 1 brain.Samples were fixed in 10% neutral buffered formalin for 12-72 hrs and included in paraffin at 56°C; 4 mm thick sections were pre-treated in microwave owen in 10 mM citric acid, pH 6.0 and incubated overnight with the following poly/mono-clonal antisera: VEGF-R1 (Santa Cruz Biothechnology 1:400),CD 133(Abgent 1:80),CD 117 (DAKO 1:500),CD-34 (DAKO 1:50).Clusters of immunoreactive cells were evident with CD 117 and CD 34 in all nodes.A different degree of immunopositivity was found with VEGR-R1 and CD 133 antibodies for different sites of metastasis; in particular, the cases spread in lungs, liver and central nervous system were more immunoreactive, compared to those with bone localization. All nodes classified as pN1a showed no immunoreactivity.The prognostic significance of HPCs in PMN needs to be further investigated, especially in node-negative BCs. The immunomorphologic aspect of the lymph node microenvironment could have significant clinical implications, in order to optimize BC therapeutic strategies. Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 6024.

17-P029 Inflammatory regulation of bone marrow-derived endothelial progenitor cells during tissue repair using a mouse model of type 2 diabetes

17-P029 Inflammatory regulation of bone marrow-derived endothelial progenitor cells during tissue repair using a mouse model of type 2 diabetes

Roles of endothelial progenitor cells on tumor angiogenesis and its potential clinical value

Recent studies using different animal models of cancer suggest the importance of bone marrow-derived endothelial progenitor cells (EPC) in tumor vascularization and growth. EPC level in peripheral blood is increased in response to certain signals or cytokines secreted by tumor, and they recruit into the neovas-cular bed of tumor tissues. Furthermore,clinical studies show that changes in EPC levels might predict the effi-cacy of anticaneer drugs including antiangiogenic agents. On the basis of these observations, EPC has potential diagnostic and therapeutic roles for malignant tumor. Key words: Stem cells ; Neovascularization,pathologic ; Neoplasms ; Therapy ;

Construction and identification of the rat recombinant plasmid PCMV/ho-1 and its expression in the endothelial progenitor cells derived from the bone marrow

Objective To construct a kind of bone marrow-derived endothelial progenitor cells (EPCs) in which heine oxygenase-1(ho-1)gene is highly expressed. Methods ho-1 gene was amplified by RT-PCR,and ligated into the PCMV vector. Then the recombinant plasmid was transferred into EPCs. The expression of ho-1 was detected by immunohistochemistry staining. Results(1)Restrictive diges-tion,RT-PCR, plasmid colony gel electrophoresis, and sequencing revealed the successful construction of expression plasmid pCMV/ho-1 ,which was mediated via lipofectamine2000 ; (2) It was confirmed that the isolated ceils derived from bone marrow were EPCs which were characterized by morphology,immunohisto- chemistry stain of CD133, CD34 and Vwf antibody, and double staining of LDL-UEA after VEGF induc- tian;(3) The enhanced green fluorescence could be seen by fluorescence microscopy in pCMV/ho-1-transfected EPCs. lmmunostaining with ho-1 in engineered cells was strong positive after three generations. Conclusion The recombinant eukaryotic expression vector pCMV/ho-1 has been constructed and stably expressed efficiently in EPCs. The method was practical. Key words: Heme oxygenase-1 ; Endotheliapregenitor Cells; Transfectian

Exercise Ameliorates The Adhesiveness Of Bone Marrow-derived Endothelial Progenitor Cells Post Acute Myocardial Infarction.

Exercise Ameliorates The Adhesiveness Of Bone Marrow-derived Endothelial Progenitor Cells Post Acute Myocardial Infarction.

Mechanisms Underlying the Effects of Leukocyte Apheresis with a Fiber Filter in a Rat Model of Dextran Sulfate Sodium-Induced Colitis

While several clinical trials have suggested that leukocytapheresis (LCAP) by filtration can benefit patients with active ulcerative colitis, the mechanisms underlying these benefits are largely unknown. The aim of this study was to address the mechanisms that may underlie the therapeutic effects of LCAP using a dextran sulfate sodium-induced colitis model in rats. Treatment with the active column, but not the sham column, improved disease severity by down-regulating pro-inflammatory events, including the cell-proliferative responses and inflammatory cytokine and reactive oxygen production, as well as by up-regulating protective events, including hepatocyte growth factor production, bone marrow-derived endothelial progenitor cell induction, and colonic blood flow levels, which were mediated predominantly by calcitonin gene-related peptide. The improvement was also associated with the increase of Ki-67 labeling in the colonic epithelium. In conclusion, the LCAP procedure was used in a dextran sulfate sodium-induced colitis model in rats under extracorporeal circulation conditions. This approach down-regulated pro-inflammatory events and up-regulated protective events in association with disease improvement. These data suggest that LCAP is feasible in animals and should shed light on the mechanisms of LCAP in clinical settings.

D013 PPAR-alpha is essential for microparticleinduced differentiation of bone marrow-derived endothelial progenitor cells and in vitro angiogenesis

Bone marrow-derived endothelial progenitor cells (EPCs), present in the systemic circulation, are augmented in response to tissue ischemia, and incorporate into sites of neovascularization. They possess the ability to differentiate into endothelial cells (ECs). Microparticles (MPs), small fragments generated from the plasma membrane, are able to activate the angiogenic program of ECs through mRNA transfer. Also, Peroxisome Proliferator-Activated Receptor (PPAR) alpha agonists increase cardiac progenitor differentiation. Here, we have studied the effects of circulating MPs obtained from PPARalpha wild type (WT) and knock-out (KO) mice on EPC differentiation and in vitro capillary-like tube formation of ECs. MPs were obtained from blood of mice, and MP sub-populations were characterized by flow cytometer. EPCs were isolated from WT mice using density gradient separation. Isolated cells were cultured in the absence or presence of MPs from PPARalpha WT or KO mice for 7 days. Then, expression of specific markers of EPCs (Sca-1/Flk-1) were analysed by flow cytometry or dual binding of FITC-labeled BS I lectin and Dil-acetylated-LDL by confocal microscopy. Also, ECs were isolated from WT mice aorta. The effects of 24 hours incubation with MPs from PPARalpha WT or KO mice on in vitro angiogenesis were assessed by capillary-like tube formation assay on Matrigel. Circulating MPs from PPARalpha mice were mainly derived from platelets and leucocytes. MP levels were not significantly different between strains. Only MPs from PPARalpha WT mice harbored PPARalpha. Incubation of EPCs with MPs from PPARalpha WT, but not from KO mice, increased significantly the number of differentiated EPCs. Incubation of ECs with PPARalpha WT-derived MPs increased capillary-like tube formation of ECs. By contrast, deletion of PPARalpha markedly inhibited in vitro tube formation of ECs. Our results suggest that the presence of PPARalpha in MPs, not only stimulates EPCs differentiation, but also favored in vitro angiogenesis of ECs. These findings provide a new alternative approach for cell therapy of cardiovascular pathologies associated with impaired angiogenesis that might include injection of EPCs treated with PPARalpha MPs. Supported by Fondation de France.

Effects of constant magnetic field on proliferation, apoptosis and nitric oxide secretion of rat endothelial pro-genitor cells intervened by C-reactive protein

Objective To investigate the effects of constant magnetic field (CMF) on proliferation, apopto-sis and nitric oxide (NO) secretion of rat bone marrow-derived endothelial progenitor cells (EPCs) intervened by C-reactive protein (CRP). Methods EPCs were isolated from rat bone marrow by density gradient centrifugation and cultured on fibronectin-coated dishes. The cells were divided into five groups, i. e., control group, CRP (12 μg/ml) group, CRP plus CMF (0.1, 0. 5, 1.0 mT) groups. Samples were collected 24 hours after incubation. Cell proliferation was measured by MTT chromatometry. Apoptosis rate was detected by flow-cytometry. NO content of culture medium was measured by nitrate reductase method. Results As compared with control group, cell prolifer-ation in CRP group reduced significantly (0. 265±0. 008 vs 0. 316±0. 011, P < 0.05), NO secretion also de-creased significantly [(22.7±4.5) μmol/L vs (37.6±3.8) μmol/L, P < 0.05], cell apoptosis rate elevated sig-nificantly [(10.8±0. 8) % vs (4.2±0.5)% ,P < 0.05]. Cell proliferation in CRP plus 0. 5 mT or 1.0 mT CMF group (0. 295±0. 009,0. 302±0. 010) were much more than those in CRP group (P<0.05), NO secretion contents [(28.3±4.9) μmol/L, (29.2±5.6) μmol/L]were also much more than those in CRP group (P < 0.05) , apopto-sis rate [(7.4±0.5)% ,(6.9±0.6)%]was significantly lower than that in CRP group (P <0.05). Conclusion CMF at intensity of 0.5 mT and 1.0 mT can antagonize the effects of CR, promote proliferation of EPCs and secretion of NO and inhibit apoptosis rate of EPCs. Key words: Constant magnetic field; Endothelial progenitor cells; C-reactive protein; Cell prolifera-tion; Apoptosis

Abstract 3899: SDF-1α Mediates the Therapeutic Effect of Human Adipose-Derived Stem Cells on Acute Myocardial Infarction Recruiting Bone Marrow-Derived Endothelial Progenitor Cells

Background: Recently, human multipotent adipose-derived stem cells (hMADSs) have been isolated featuring extensive expansion capacity ex vivo. However, little is known about the therapeutic efficacy of hMADS in ischemic heart diseases. We tested the hypothesis that hMADS transplantation may contribute to cardiac functional recovery following myocardial infarction (MI). Methods and Results: Nude rats were either transplanted with hMADSs (5x10 5 /rat, n=10) or PBS (control, n=9) in ischemic myocardium immediately following MI induction. The cardiac function, infarct size and capillary density in the peri-infarct area were evaluated by echocardiography and immunostaining 28 days after surgery. The cardiac function was significantly greater with increased capillary density and reduced fibrosis area in the hMADS group than that in the control group. Next, we examined tissue regeneration in the infarct heart by the transplanted hMADSs. However, remarkable differentiation of hMADSs into any cardiac cell lineages was not detected. To explore another mechanism for the favorable effect of hMADSs, we further examined mRNA expression of cytokines in hMADSs under hypoxic conditions. Although hypoxia decreased the expressions, robust VEGF, bFGF, and SDF-1α expressions were detected in hMADSs. Notably, the stem/progenitor chemokine SDF-1α expression in hMADSs was significantly greater than that in human mesenchymal stem cells that are well known to have a therapeutic effect on ischemic heart diseases. We then focused on SDF-1α /CXCR4 axis and examined the contribution of bone marrow (BM)-derived endothelial progenitor cells (EPCs), that have CXCR4 receptor for SDF-1v, to ischemic myocardium using a Tie2/LacZ BM transplantation nude mouse model. β-gal positive EPCs are frequently observed in ischemic myocardium in the hMADS group compared to the control group. Conclusion: hMADSs exhibit a therapeutic effect on cardiac function following MI with the production of VEGF, bFGF, and SDF-1α demonstrating paracrine effects rather than direct contribution to cardiac regeneration. These findings suggest that transplanted hMADSs and recruited EPCs may synergistically promote angiogenesis playing a role in ischemic myocardium.

Abstract 1743: Stem/Progenitor Markers Sca-1 versus C-kit and CD31 Determine Angiogenic Potential of Mouse Bone Marrow-derived Endothelial Progenitor Cells

Background: Endothelial progenitor cells (EPCs) have been shown to have angiogenic potential contributing to neovascularization. However, the definition of EPC, including surface marker expression of EPCs promoting vasculo-/angiogenesis in ischemic tissue, remains uncertain. We hypothesized that stem/progenitor (c-kit vs. sca-1) and endothelial cell (EC) markers (CD31) may identify cells with enhanced EPC potential. Methods and Results: Mononuclear cells (MNCs) were isolated from mouse bones, and Lin+ cells were depleted by magnetic cell sorting. Lin- cells were further sorted with the following markers (% of total MNCs) by FACS: c-kit+ (1.87%), sca-1+ (0.6%), c-kit+ /CD31+ (1.1%) and sca-1+ /CD31+ (0.28%). Non-sorted MNCs were used as a control. To examine EC phenotype in culture, cells were labeled with DiI and co-cultured with mature ECs (human microvascular endothelial cells: HMVECs). The percent incorporation of DiI labeled cells into HMVEC tube structures 12 hours after co-culture and BS1-lectin positivity/acLDL uptake were: sca-1+ /CD31+ cells (87 ± 2%) &gt; c-kit+ /CD31+ (79 ± 8%) &gt; sca-1+ (62 ± 8%) &gt; c-kit+ (59 ± 5%) &gt; MNC (50 ± 3% ) . Next, we examined homing capacity of these cells to ischemic myocardium using a mouse myocardial infarction (MI) model. DiI-labeled cells (5x10 4 , IV) were injected to splenectomized mice 3 days after MI, and the hearts were excised 24 hours after the cell injection for histological analysis. Interestingly, the number of recruited/retained DiI-labeled-cells in the MI hearts exactly replicated the findings of the in vitro tube formation assay (cells/HPF): sca-1+ /CD31+ (108 ± 26) &gt; c-kit+ /CD31+ (77 ± 16) &gt; sca-1+ (71 ± 14) &gt; c-kit+ (67 ± 1) &gt; MNCs (48 ± 6) , suggesting that sca-1+ /CD31+ cells might have great functional activities as endothelial precursors. Conclusions: Both stem/progenitor marker Sca-1 and EC marker CD31 expressing EPCs exhibited high potential angiogenic capacity with EC phenotypic features compared with c-kit expressing cells. Our data suggest that Sca-1+ /CD31+ cells may represent EPC-rich cell population, and Sca-1/CD31 could be useful markers to enrich for cells with EPC potential. Ongoing studies will determine the in vivo characteristics of these cells for ischemic tissue repair.

Abstract 3421: Sox2 Converts Human Mesoangioblasts into Nanog-Expressing Multipotent Cells with Enhanced Cardiac Repair

Induced pluripotent cells (iPS) were generated by overexpression of four factors (Oct3/4, Klf4, c-myc and Sox2) in fibroblasts and showed similar characteristic as embryonic stem (ES) cells. In contrast to iPS and ES cells, adult stem cells have a reduced plasticity. Therefore, we investigated whether reconstitution of the four pluripotency genes in adult progenitor cells improves their therapeutic capacity. Circulating mesoangioblasts (cMAB) have been recently identified in peripheral blood and showed distinct marker expression to bone marrow-derived stem cells and endothelial progenitor cells. cMAB are clonally expandable and exhibit high telomerase activity. cMAB expressed the pluripotency genes Oct3/4, KLF4, and c-Myc, whereas Sox2 and another important stemness gene, Nanog was not expressed. Since only Sox2 was absent out of the four pluripotency genes, we hypothesized that Sox2 transduction may be sufficient to induce pluripotency. Sox2 was overexpressed by lentiviral vector. Interestingly, Sox2-tranduced cMAB not only express Sox2 but also re-express the stem cell gene Nanog. Controls confirmed that the constitutively expressed genes, Oct3/4, KLF4, and c-myc, remained present after Sox2 transduction. Sox2-transduced cMAB formed embryoid body-like structures in culture. In order to test whether Sox2-transduced cells may exhibit improved therapeutic potential, we injected Sox2-transduced cMABs into nude mice after acute myocardial infarction. Four weeks after cell therapy with Sox-overexpressing cells, cardiac function was improved compared to mice treated with control cells (LVEDV/weight; 1.34 ± 0.14 vs 1.88 ± 0.02 μl/g, LVEDP; 13.2 ± 1.0 vs 18.7 ± 2.6 mmHg, dp/dt max; 7989 ± 1030 vs 6331 ± 149 mmHg/s, dp/dt min; 6583 ± 683 vs 4792 ± 514 mmHg/s, and Tau; 9.2 ± 0.8 vs 11.6 ± 1.8 ms, respectively). In summary, the complementation of Sox2 in Oct3/4-, Klf4-, and c-myc-expressing cMABs induced Nanog expression and improved the cardiac regeneration capacity of these circulating adult stem cells.

Abstract 1963: Endothelial Cell-Derived Microparticles Interact with Regenerating Cells and Transfer Biological Information

Apoptosis of endothelial cells (ECs) leads to the development of endothelial dysfunction, which itself is strongly associated with poor cardiovascular prognosis. EC apoptosis can be quantified using flow-cytometry-based enumeration of circulating EC-derived microparticles (EMP) within peripheral blood. Bone marrow-derived endothelial progenitor cells (EPC) contribute to EC regeneration and are an important predictor for cardiovascular mortality. We postulate that EC apoptosis with concomitant release of EMP is an important signal for regenerating cells to initiate EC repair. EMP were generated from human coronary arterial endothelial cells (HCAEC). Proteomic analysis showed that the identified proteins represent cytoskeleton/cytoskeleton-binding proteins, proteins involved in intracellular transport/signalling, and protein folding. In addition, proteins related to apoptosis, proliferation, and migration were identified. HCAEC/EPC were able to incorporate EMP in an annexin I/ phosphatidylserine receptor-dependent way. Incubation of mononuclear cells with EMP lead to an enhanced conversion into early outgrowth EPC. EMP co-incubation also changed the phenotype of cultivated Langerhans-like dendritic cells into an immature phenotype. Co-cultivation of ECs and EPC with EMP prevented TNF-alpha induced cell apoptosis. Migration of EPC was enhanced in response to EMP. Finally, we measured EPC liberation from bone marrow into peripheral blood. Intravenous treatment of C57bl6 mice with EMP enhanced the number of sca-1/flk-1 positive EPC within peripheral blood compared to control. The number of CD31+/Annexin+ EMP and CD34 + /KDR + EPC was determined in 40 patients with coronary artery disease. The number of circulating EMP correlated with EPC function (p&lt;0.001, r=0.601). EMP and EPC seem to substantially interact in an annexin I/PSR dependent way. EMP influence EPC biology in vitro and induces EPC mobilization in vivo. We speculate that the described interaction of EMP with EPC enhance the homing process of EPC within the area of EC damage.

Abstract 3753: Critical Role of Scavenger Receptor-BI Expressing Bone Marrow-Derived Endothelial Progenitor Cells in the Attenuation of Allograft Vasculopathy by Human Apo A-I Transfer

Background: Accelerated endothelial regeneration mediated by enhanced endothelial progenitor cell (EPC) incorporation may attenuate the development of allograft vasculopathy. Hypothesis: We investigated the hypothesis that modulation of EPC biology and attenuation of allograft vasculopathy by increased HDL cholesterol following human apo A-I (AdA-I) transfer requires scavenger receptor (SR)-BI expression in bone marrow-derived EPCs. Methods: Bone marrow transplantations with SR-BI+/+ or SR-BI−/− bone marrow were performed 4 weeks before gene transfer or saline injection. E1E3E4-deleted vectors containing a hepatocyte-specific human apo A-I expression cassette or containing no expression cassette were injected via the tail vein. Two weeks later, a common carotid artery of a female Balb/c donor mouse was transplanted paratopically into male recipient C57BL/6 mice. To analyse EPC incorporation, sex mismatch bone marrow transplantations were performed in female C57BL/6 mice and incorporated EPCs were quantified by in situ hybridization for the murine Y-chromosome. Results: Following AdA-I transfer, the number of circulating EPCs increased 2.0-fold (p&lt;0.0001) at different time-points in C57BL/6 mice transplanted with SR-BI+/+ bone marrow but was unaltered in mice with SR-BI−/− bone marrow. The effect of HDL on EPC migration in vitro requires signaling via SR-BI and extracellular signal-regulated kinases (ERK) and is dependent on increased NO production in EPCs. Human apo A-I transfer 2 weeks before paratopic artery transplantation reduced intimal area at day 21 3.7-fold (p&lt;0.001) in mice with SR-BI+/+ bone marrow but had no effect in mice with SR-BI−/− bone marrow. The number of CD31 positive endothelial cells lining the lumen and the number of incorporated EPCs was increased 3.0-fold (p&lt;0.001) and 9.7-fold (p&lt;0.001), respectively, in AdA-I treated chimeric SR-BI+/+ mice compared to control mice with SR-BI+/+ bone marrow. Endothelial regeneration and EPC incorporation was not increased after AdA-I transfer in chimeric SR-BI−/−mice. Conclusion: Human apo A-I transfer-mediated endothelial regeneration to prevent allograft vasculopathy is strictly dependent on SR-BI expressing bone marrow-derived EPCs.

Effects of constant magnetic fields on proliferation and migration of endothelial progenitor cells under rapamycin intervention: experiment with rats

To investigate the effects of constant magnetic field (CMF) on proliferation and migration of bone marrow-derived endothelial progenitor cells (EPCs) under rapamycin intervention. EPCs were isolated from rat bone marrow by density gradient centrifugation and cultured on fibronectin-coated dishes. Six days later the attached cells were divided into 5 groups: control group, rapamycin (1 ng/ml) group, and 3 rapamycin + CMF groups (treated with CMF of the doses 0.1 mT, 0.5 mT, and 1.0 mT respectively). Samples were collected 24 hours after incubation. Cell proliferation was measured by MTT chromatometre. EPC migration was detected with modified Boyden chamber assay. The EPC proliferation ability of the rapamycin group, expressed by absorbance, was (0.252 +/- 0.006), significantly lower than that of the control group [(0.328 +/- 0.025), P < 0.05]. The number of migrating EPC was (31 +/- 3) cells, significantly lower than that of the control group [(48 +/- 5), P < 0.05]. The EPC proliferation ability of the rapamycin + CMF 0.5 mT and 1.0 mT groups, expressed by absorbance, were (0.278 +/- 0.008) and (0.280 +/- 0.010) respectively, both significantly higher than that of the control group (both P < 0.05). The migrating EPC number of the rapamycin + CMF 0.5 mT and 1.0 mT groups were (37 +/- 3) and (38 +/- 4) respectively, both significantly higher than that of the control group (both P < 0.05). CMF of the doses of 0.5 mT and 1.0 mT antagonizes the effects of rapamycin on EPCs, increasing the proliferation and migration of EPCs.

Pharmacological approaches to improve endothelial repair mechanisms

Endothelial injury is thought to play a pivotal role in the development and progression of vascular diseases, such as atherosclerosis, hypertension or restenosis, as well as their complications, including myocardial infarction or stroke. Accumulating evidence suggests that bone marrow-derived endothelial progenitor cells (EPCs) promote endothelial repair and contribute to ischemia-induced neovascularization. Coronary artery disease and its risk factors, such as diabetes, hypercholesterolemia, hypertension and smoking, are associated with a reduced number and impaired functional activity of circulating EPCs. Moreover, initial data suggest that reduced EPC levels are associated with endothelial dysfunction and an increased risk of cardiovascular events, compatible with the concept that impaired EPC-mediated vascular repair promotes progression of vascular disease. In this review we summarize recent data on the effects of pharmacological agents on mobilization and functional activity of EPCs. In particular, several experimental and clinical studies have suggested that statins, angiotensin-converting enzyme inhibitors, angiotensin II type 1 receptor blockers, PPAR-γ agonists and erythropoietin increase the number and functional activity of EPCs. The underlying mechanisms remain largely to be defined; however, they likely include activation of the PI3-kinase/Akt pathway and endothelial nitric oxide synthase, as well as inhibition of NAD(P)H oxidase activity of progenitor cells.

Circulating endothelial cells and endothelial progenitor cells in childhood primary angiitis of the central nervous system

Background Primary angiitis of the central nervous system in children (cPACNS) is an inflammatory vasculitis that solely affects the CNS vessels in the absence of a systemic inflammatory process. Circulating endothelial cells (CECs) are increasingly described as biomarkers for tracking vascular injury [1]. Additionally, bone marrow-derived endothelial progenitor cells (EPCs) are thought to play a pivotal role in the regeneration of damaged endothelium. We describe the relationship of CECs and EPCs to clinical and/or radiological disease progression in cPACNS.