An in vitro model for the study of human bone marrow angiogenesis: role of hematopoietic cytokines

Simulation of Soluble and Bound VEGF-stimulated in vitro Capillary-like Network Formation on Deformed Substrate

Capillary plexus cultivation is crucial in tissue engineering and regenerative medicine. Theoretical simulations have been conducted to supplement the expensive experimental works. However, the mechanisms connecting mechanical and chemical stimuli remained undefined, and the functions of the different VEGF forms in the culture environment were still unclear. In this paper, we developed a hybrid model for simulating short-term in vitro capillary incubations. We used the Cellular Potts model to predict individual cell migration, morphology change, and continuum mechanics to quantify biogel deformation and VEGF transport dynamics. By bridging the mechanical regulation and chemical stimulation in the model, the results showed good agreement between the predicted network topology and experiments, in which elongated cells connected, forming the network cords and round cells gathered, creating cobblestone-like aggregates. The results revealed that the capillary-like networks could develop in high integrity only when the mechanical and chemical couplings worked adequately, with the cell morphology and haptotaxis driven by the soluble and bound forms of VEGF, respectively, functioning simultaneously.

Aberrant expression of proatherogenic cytokines and growth factors in human umbilical vein endothelial cells from newborns of type 2 diabetic women

Objectives:

This study reports the levels of cytokines, chemokines, and growth factors previously identified as taking part in the pathology of atherosclerosis in human umbilical vein endothelial cells derived from mothers with type 2 diabetes and compares them with those in human umbilical vein endothelial cells derived from healthy mothers under normal glucose conditions.

Methods:

Cytokine analysis measures of human umbilical vein endothelial cell lysates were obtained using a multiple analyte profiling (xMAP) assay based on magnetic bead-based technology, using the MAGPIX instrument. The correlation between cytokines, chemokines, and growth factors was examined statistically in human umbilical vein endothelial cells derived from mothers with type 2 diabetes.

Results:

This study showed that the expression of proinflammatory cytokine interleukin-1 alpha was significantly greater in human umbilical vein endothelial cells derived from mothers with type 2 diabetes than those derived from healthy mothers. The protein level of granulocyte colony-stimulating factor was higher in human umbilical vein endothelial cells derived from mothers with type 2 diabetes than those derived from healthy mothers. A significant positive correlation was demonstrated between the protein expression of granulocyte colony-stimulating factor and granulocyte-macrophage colony-stimulating factor in human umbilical vein endothelial cells derived from mothers with type 2 diabetes.

Conclusion:

Diabetes evokes a persistent inflammatory phenotype in human umbilical vein endothelial cells, as indicated by the enhanced production of cytokines and growth factors under normal glucose conditions.

Effect of granulocyte colony-stimulating factor on bone marrow: evaluation by intravoxel incoherent motion and dynamic contrast-enhanced magnetic resonance imaging

OBJECTIVE

To report our experience with the use of intravoxel incoherent motion (IVIM) magnetic resonance imaging (MRI) and dynamic contrast-enhanced (DCE)-MRI in bone marrow before and after administration of granulocyte colony-stimulating factor (GCSF). Moreover, a small series of patients with bone metastases from breast cancer have been evaluated by IVIM DW-MRI and DCE-MRI before and after GCSF administration.

MATERIALS AND METHODS

We studied with IVIM-MRI and DCE-MRI 14 patients with rectal or uterine cervix cancer studied before and 4-18 days after administration of GCSF; the second MR examination was obtained after three chemotherapy courses. IVIM perfusion fraction (f), pseudo-diffusion coefficient (D*), true diffusion coefficient (D) and apparent diffusion coefficient (ADC) as well area under the curve at 60 s (AUC60) were calculated for bone marrow before and after GCSF administration. Moreover, two different IVIM parametric maps (i.e., ADC and ADC_low) were generated by selecting two different intervals of b values (0-1000 and 0-80, respectively). Furthermore, four patients affected by pelvic bone metastases from breast adenocarcinoma who received GCSF administration were also qualitatively evaluated for evidence of lesions on ADC maps, ADC_low maps and DCE-MRI.

RESULTS

ADC, D, D*, f and AUC60 values were significantly higher in hyperplastic bone marrow than in untreated bone marrow (p values < 0.0001, < 0.0001, < 0.001, < 0.001, < 0.0001, respectively). All bone metastases were clearly differentiable from hyperplastic bone marrow on ADC_low maps, but not on ADC maps and DCE-MRI.

CONCLUSION

MR functional imaging techniques, such as DW-, IVIM DW- and DCE-MRI are effective tools in assessing the response of bone marrow to the administration of growth factors. Although an overlap between signal of hyperplastic bone marrow and lytic bone metastases can occur on ADC maps and DCE-MRI, evaluation of ADCl_ow maps by IVIM DW-MRI could permit to differentiate hyperplastic bone marrow from lytic bone metastases. Further studies are needed to confirm our data.

Hematopoietic growth factors and tumor angiogenesis

Angiogenesis is regulated by numerous "classic" factors such as vascular endothelial growth factor (VEGF) and many other endogenous "non-classic"peptides, including erythropoietin (Epo), and granulocyte-/granulocyte macrophage colony stimulating factor (G-/GM-CSF). The latter play an important regulatory role in angiogenesis, especially under pathological conditions and constitute a crosslink between angiogenesis and hematopoiesis. This article reviews studies on the ability of hematopoietic cytokines to affect several endothelial cell functions in tumor angiogenesis. These findings in all these studies support the hypothesis formulated at the beginning of this century that a common ancestral cell, the hemangioblast, gives rise to cells of both the endothelial and the hematopoietic lineages.

Evaluation of Arteriolar Smooth Muscle Cell Function in an Ex Vivo Microvascular Network Model

An emerging challenge in tissue engineering biomimetic models is recapitulating the physiological complexity associated with real tissues. Recently, our laboratory introduced the rat mesentery culture model as an ex vivo experimental platform for investigating the multi-cellular dynamics involved in angiogenesis within an intact microvascular network using time-lapse imaging. A critical question remains whether the vessels maintain their functionality. The objective of this study was to determine whether vascular smooth muscle cells in cultured microvascular networks maintain the ability to constrict. Adult rat mesenteric tissues were harvested and cultured for three days in either MEM or MEM plus 10% serum. On Day 0 and Day 3 live microvascular networks were visualized with FITC conjugated BSI-lectin labeling and arteriole diameters were compared before and five minutes after topical exposure to vasoconstrictors (50 mM KCl and 20 nM Endothelin-1). Arterioles displayed a vasoconstriction response to KCl and endothelin for each experimental group. However, the Day 3 serum cultured networks were angiogenic, characterized by increased vessel density, and displayed a decreased vasoconstriction response compared to Day 0 networks. The results support the physiological relevance of the rat mesentery culture model as a biomimetic tool for investigating microvascular growth and function ex vivo.

Enhancing microvascular formation and vessel maturation through temporal control over multiple pro-angiogenic and pro-maturation factors

Therapeutic stimulation of angiogenesis to re-establish blood flow in ischemic tissues offers great promise as a treatment for patients suffering from cardiovascular disease or trauma. Since angiogenesis is a complex, multi-step process, different signals may need to be delivered at appropriate times in order to promote a robust and mature vasculature. The effects of temporally regulated presentation of pro-angiogenic and pro-maturation factors were investigated in vitro and in vivo in this study. Pro-angiogenic factors vascular endothelial growth factor (VEGF) and angiopoietin 2 (Ang2) cooperatively promoted endothelial sprouting and pericyte detachment in a three-dimensional in vitro EC-pericyte co-culture model. Pro-maturation factors platelet-derived growth factor B (PDGF) and angiopoietin 1 (Ang1) inhibited the early stages of VEGF- and Ang2-mediated angiogenesis if present simultaneously with VEGF and Ang2, but promoted these behaviors if added subsequently to the pro-angiogenesis factors. VEGF and Ang2 were also found to additively enhance microvessel density in a subcutaneous model of blood vessel formation, while simultaneously administered PDGF/Ang1 inhibited microvessel formation. However, a temporally controlled scaffold that released PDGF and Ang1 at a delay relative to VEGF/Ang2 promoted both vessel maturation and vascular remodeling without inhibiting sprouting angiogenesis. Our results demonstrate the importance of temporal control over signaling in promoting vascular growth, vessel maturation and vascular remodeling. Delivering multiple growth factors in combination and sequence could aid in creating tissue engineered constructs and therapies aimed at promoting healing after acute wounds and in chronic conditions such as diabetic ulcers and peripheral artery disease.

Pericyte-like progenitors show high immaturity and engraftment potential as compared with mesenchymal stem cells

Mesenchymal stem cells (MSCs) and pericyte progenitors (PPs) are both perivascular cells with similar multipotential properties regardless of tissue of origin. We compared the phenotype and function of the 2 cell types derived from the same bone-marrow samples but expanded in their respective media - pericyte conditions (endothelial cell growth medium 2 [EGM-2]) for PPs and standard medium (mesenchymal stem cell medium [MSM]) for MSCs. After 3 weeks of culture, whatever the expansion medium, all cells showed similar characteristics (MSC markers and adipo-osteo-chondroblastic differentiation potential), although neuronal potential was greater in EGM-2- than MSM-cultured cells. As compared with MSM-cultured MSCs, EGM-2-cultured PPs showed higher expression of the pericyte-specific antigen 3G5 than α-smooth muscle actin. In addition, EGM-2-cultured PPs showed an immature phenotype, with upregulation of stemness OCT4 and SOX2 proteins and downregulation of markers of osteoblastic, chondroblastic, adipocytic and vascular smooth muscle lineages. Despite having less effective in vitro immunosuppression capacities than standard MSCs, EGM-2-cultured PPs had higher engraftment potentials when combined with biomaterials heterotopically-transplanted in Nude mice. Furthermore, these engrafted cells generated more collagen matrix and were preferentially perivascular or lined trabeculae as compared with MSM-cultured MSCs. In conclusion, EGM-2-cultured PPs are highly immature cells with increased plasticity and engraftment potential.

Early use of granulocyte colony stimulating factor improves survival in a rabbit model of chronic myocardial ischemia

BACKGROUND

Granulocyte colony stimulating factor (G-CSF) improves the survival of animals with myocardial infarction by inducing bone marrow stem cell mobilization and homing to infarcted areas. However, its precise mechanisms and direct effects on the ischemic myocardium remain unclear. In this study we investigated the direct effects and mechanisms of G-CSF in a rabbit model of chronic myocardial ischemia.

METHODS

Myocardial ischemia models were created by partial ligation of the left anterior descending coronary artery in Japanese white male rabbits. Rabbits were subcutaneously injected with 10 μg/kg of G-CSF (G-CSF group) or saline (control group) for 6 days after myocardial ischemia. Direct effects of G-CSF were analyzed by immunohistochemistry and terminal dUTP nick end-labeling (TUNEL).

RESULTS

Rabbits in the G-CSF group exhibited 75% survival compared to 40% in the control group (p<0.05). Immunohistochemistry of the ischemic myocardium showed increased homing of CD34+ cells on day 7 post-surgery and more vessels on day 28 post-surgery by anti-von Willebrand factor staining in the G-CSF group compared with the control group. Furthermore, an increased percentage of CD34+ cells were observed in peripheral blood and upregulation of vascular endothelial growth factor expression in ischemic tissue in the G-CSF group compared with the control group. TUNEL showed that the apoptotic index in the ischemic myocardium decreased in the G-CSF group compared with the control group on day 28 post-surgery.

CONCLUSIONS

In addition to increasing stem cell mobilization and homing to ischemic myocardium, G-CSF treatment after myocardial ischemia improves survival by accelerating neovascularization and reducing apoptosis.

Vascular endothelial growth factor regulates melanoma cell adhesion and growth in the bone marrow microenvironment via tumor cyclooxygenase-2

BACKGROUND

Human melanoma frequently colonizes bone marrow (BM) since its earliest stage of systemic dissemination, prior to clinical metastasis occurrence. However, how melanoma cell adhesion and proliferation mechanisms are regulated within bone marrow stromal cell (BMSC) microenvironment remain unclear. Consistent with the prometastatic role of inflammatory and angiogenic factors, several studies have reported elevated levels of cyclooxygenase-2 (COX-2) in melanoma although its pathogenic role in bone marrow melanoma metastasis is unknown.

METHODS

Herein we analyzed the effect of cyclooxygenase-2 (COX-2) inhibitor celecoxib in a model of generalized BM dissemination of left cardiac ventricle-injected B16 melanoma (B16M) cells into healthy and bacterial endotoxin lipopolysaccharide (LPS)-pretreated mice to induce inflammation. In addition, B16M and human A375 melanoma (A375M) cells were exposed to conditioned media from basal and LPS-treated primary cultured murine and human BMSCs, and the contribution of COX-2 to the adhesion and proliferation of melanoma cells was also studied.

RESULTS

Mice given one single intravenous injection of LPS 6 hour prior to cancer cells significantly increased B16M metastasis in BM compared to untreated mice; however, administration of oral celecoxib reduced BM metastasis incidence and volume in healthy mice, and almost completely abrogated LPS-dependent melanoma metastases. In vitro, untreated and LPS-treated murine and human BMSC-conditioned medium (CM) increased VCAM-1-dependent BMSC adherence and proliferation of B16M and A375M cells, respectively, as compared to basal medium-treated melanoma cells. Addition of celecoxib to both B16M and A375M cells abolished adhesion and proliferation increments induced by BMSC-CM. TNFα and VEGF secretion increased in the supernatant of LPS-treated BMSCs; however, anti-VEGF neutralizing antibodies added to B16M and A375M cells prior to LPS-treated BMSC-CM resulted in a complete abrogation of both adhesion- and proliferation-stimulating effect of BMSC on melanoma cells. Conversely, recombinant VEGF increased adherence to BMSC and proliferation of both B16M and A375M cells, compared to basal medium-treated cells, while addition of celecoxib neutralized VEGF effects on melanoma. Recombinant TNFα induced B16M production of VEGF via COX-2-dependent mechanism. Moreover, exogenous PGE2 also increased B16M cell adhesion to immobilized recombinant VCAM-1.

CONCLUSIONS

We demonstrate the contribution of VEGF-induced tumor COX-2 to the regulation of adhesion- and proliferation-stimulating effects of TNFα, from endotoxin-activated bone marrow stromal cells, on VLA-4-expressing melanoma cells. These data suggest COX-2 neutralization as a potential anti-metastatic therapy in melanoma patients at high risk of systemic and bone dissemination due to intercurrent infectious and inflammatory diseases.

CXCR1 and CXCR2 silencing modulates CXCL8-dependent endothelial cell proliferation, migration and capillary-like structure formation

CXCR1 and CXCR2 are receptors for angiogenic ELR+CXC chemokines and are differentially expressed on endothelial cells; however, their functional significance in angiogenesis remains unclear. In this study, we determined the functional significance of these receptors in modulating endothelial cell phenotype by knocking-down the expression of CXCR1 and/or CXCR2 in human microvascular endothelial cells (HMEC-1) using short-hairpin RNA (shRNA). Cell proliferation, migration, invasion and capillary-like structure (CLS) formation were analyzed. Our data demonstrate that knock-down of CXCR1 and/or CXCR2 expression inhibited endothelial cell proliferation, survival, migration, invasion and CLS formation. Additionally, we examined the mechanism of CXCL8-dependent CXCR1 and/or CXCR2 mediated phenotypic changes by evaluating ERK phosphorylation and cytoskeletal rearrangement and observed inhibition of ERK phosphorylation and cytoskeletal rearrangement in HMEC-1-shCXCR1, HMEC-1-shCXCR2 and HMEC-1-shCXCR1/2 cells. Together, these data demonstrate that CXCR1 and CXCR2 expression plays a critical role in regulating multiple biological activities in human microvascular endothelial cells.

Control of autocrine and paracrine myocardial signals: an emerging therapeutic strategy in heart failure

A growing body of evidence supports the hypothesis that autocrine and paracrine mechanisms, mediated by factors released by the resident cardiac cells, could play an essential role in the reparative process of the failing heart. Such signals may influence the function of cardiac stem cells via several mechanisms, among which the most extensively studied are cardiomyocyte survival and angiogenesis. Moreover, besides promoting cytoprotection and angiogenesis, paracrine factors released by resident cardiac cells may alter cardiac metabolism and extracellular matrix turnover, resulting in more favorable post-injury remodeling. It is reasonable to believe that critical intracellular signals are activated and modulated in a temporal and spatial manner exerting different effects, overall depending on the microenvironment changes present in the failing myocardium. The recent demonstration that chemically, mechanically or genetically activated cardiac cells may release peptides to protect tissue against ischemic injury provides a potential route to achieve the delivery of specific proteins produced by these cells for innovative pharmacological regenerative therapy of the heart. It is important to keep in mind that therapies currently used to treat heart failure (HF) and leading to improvement of cardiac function fail to induce tissue repair/regeneration. As a matter of facts, if specific autocrine/paracrine cell-derived factors that improve cardiac function will be identified, pharmacological-based therapy might be more easily translated into clinical benefits than cell-based therapy. This review will focus on the recent development of potential pharmacologic targets to promote and drive at molecular level the cardiac repair/regeneration in HF.

Perioperative GMCSF limits the proangiogenic plasma protein changes associated with colorectal cancer resection

AIMS

Colorectal resection (CR) increases plasma VEGF levels which may promote residual tumor growth. This study assessed the effect of perioperative GMCSF on plasma levels of sVEGFR1, Ang-1 and Ang-2 and also the impact of post-GMCSF plasma on in vitro endothelial cell (EC) growth and invasion. Ang-2 increases while sVEGFR1 and Ang-1 impede angiogenesis.

METHODS

Fifty-nine CR cancer patients were randomized to 7 perioperative doses of GMCSF or saline for 3days prior and 4days after CR. Blood samples were taken pre-drug (PreRx) and on several postoperative days (POD). Protein levels were assessed and PreRx and POD 5 plasma added to EC cultures after which branch point formation (ECBPF) and invasion (ECI) were measured.

RESULTS

sVEGFR1 levels were significantly higher on POD 1 and POD 5 in both groups but the GMCSF POD 5 level was twice the control value (p=0.002). Ang-2 levels were higher on PODs 1 and 5 in both groups (p<0.05) but the control POD 5 value (vs. GMCSF) was greater (p=0.03). Ang-1 decreases were noted in all (p=not significant, ns). The control group POD 5 ECBPF was 35.8% greater than Pre Rx (p=0.001) while the GMCSF result was 18.0% lower (p=ns); the control POD 5 median percent change from baseline was greater than the GMCSF result(p=0.008). The POD 5 ECI was +12.2% for the control group vs. baseline (p=ns) and -17.2% for the GMCSF group (p=ns): the control median percent change was greater than in the GMCSF group(p=0.045).

CONCLUSION

CR-related plasma changes are proangiogenic (>Ang-2) and anti-angiogenic (>sVEGFR1); the net effect is promotion of in vitro ECBPF. GMCSF limits the proangiogenic changes (higher POD 5 sVEGFR1 levels and lower Ang-2 elevations, lower POD 5 ECBPF and ECI). The clinical import of these effects is unclear; perioperative GMCSF has anti-angiogenic plasma effects that may limit tumor growth. Further investigation is warranted.

In vitro Differentiation Potential of Mesenchymal Stem Cells

SUMMARY: Mesenchymal stem cells (MSCs) represent a class of multipotent progenitor cells that have been isolated from multiple tissue sites. Of these, adipose tissue and bone marrow offer advantages in terms of access, abundance, and the extent of their documentation in the literature. This review focuses on the in vitro differentiation capability of cells derived from adult human tissue. Multiple, independent studies have demonstrated that MSCs can commit to mesodermal (adipocyte, chondrocyte, hematopoietic support, myocyte, osteoblast, tenocyte), ectodermal (epithelial, glial, neural), and endodermal (hepatocyte, islet cell) lineages. The limitations and promises of these studies in the context of tissue engineering are discussed.

Perioperative sargramostim (recombinant human GM-CSF) induces an increase in the level of soluble VEGFR1 in colon cancer patients undergoing minimally invasive surgery

INTRODUCTION

Experimentally, laparotomy is associated with increased tumor growth. In humans, abdominal surgery is associated with immunosuppression and elevated plasma VEGF levels that might stimulate tumor growth early after surgery. Avoidance of these surgery-related changes and their consequences may be advantageous. Granulocyte-macrophage colony stimulating factor (GMCSF) is a non-specific immune system up-regulator that has also been associated, experimentally, with increased release of soluble VEGF Receptor 1 (sVEGFR1) which is an endogenous inhibitor of VEGF. This study's purpose was to determine the impact of perioperatively administered recombinant human GMCSF (rhu-GMCSF) on both immune function and plasma sVEGFR1 levels in colorectal cancer patients.

METHODS

This randomized placebo-controlled study included 36 colorectal cancer patients who underwent minimally invasive resection (17 GMCSF, 19 Placebo). Patients received 7 subcutaneous injections of either rhu-GMCSF, 125 microg/m2, or saline on preoperative days 3, 2 and 1 and on postoperative days (POD) 1, 2, 3 and 4. A number of immune parameters were followed and plasma levels of soluble VEGF Receptor 1 (sVEGFR1) and VEGF were determined.

RESULTS

The total WBC, neutrophil, eosinophil, and monocyte counts were significantly higher after surgery in the GMCSF group; no differences were noted for the other immune parameters. In the GMCSF group, median plasma sVEGFR1 levels were significantly elevated on POD 1 (188.1 pg/ml), and on POD 5 (142.8 pg/ml) when compared to pre-GMCSF levels (0 pg/ml) (p-value<0.05 for all comparisons). In the placebo group, the POD5 median sVEGFR1 level (116.3 pg/ml) was elevated and of borderline significance (p=0.05) vs the pre-treatment result (0 pg/ml). Of note, both groups had significantly elevated median plasma VEGF levels on POD 5 (Control 435.7 pg/ml; GMCSF 385.3 pg/ml) when compared to their preoperative results (Control 183.3 pg/ml, p=0.0013; GMCSF 171.5 pg/ml, p=0.0055).

CONCLUSIONS

Perioperative GMCSF was not associated with an immune function benefit in this study, however, such treatment leads to increased plasma sVEGFR1 levels. Colorectal resection, with or without GMCSF, was also associated with increased VEGF levels postoperatively. Increased plasma levels of sVEGFR1 after surgery might limit the pro-angiogenic tumor stimulatory effects of VEGF. Further study of GMCSF's impact on angiogenesis appears warranted.

ERYTHROPOIETIN ENHANCES ANGIOGENESIS IN AN EXPERIMENTAL CYCLOSPORINE A-INDUCED NEPHROTOXICITY MODEL IN THE RAT

1. Erythropoietin (EPO) is a hormone regulating the proliferation and differentiation of erythroid precursor cells. The hypothesis that haematopoietic and endothelial cells share a common haemanglioblast progenitor among others is based on the finding that both cell lineages express cell surface antigens, such as CD31 and CD34. 2. In the present study, we investigated the angiogenic potential of recombinant human erythropoietin on cyclosporine A (CsA)-induced nephrotoxicity in the rat kidney and compared it with the effect of basic fibroblast growth factor (bFGF), a well-known angiogenic factor. 3. Rats were divided into five groups: A (control), B (EPO treated), C (CsA treated), D (CsA + EPO treated) and E (CsA + bFGF treated). Mouse anti-human CD31 and CD34 antibodies were used to evaluate the kidney vessels present in histological preparations. 4. Glomerular and peritubular capillaries in Group B (EPO) were increased compared with the control (Group A; P < 0.05). Reduction of the same kidney vessels (glomerular and peritubular capillaries) in Group C (CsA; P < 0.05) compared with controls was observed, whereas in Groups D (CsA + EPO treated) and E (CsA + bFGF treated), capillaries were increased compared with Group C (CsA; P < 0.05). 5. Erythropoietin has a significant angiogenic effect in rat kidney with CsA-induced nephrotoxicity, similar to the effect of the other angiogenic factor bFGF.

Rethinking STOP-ROP: is it worthwhile trying to modulate excessive VEGF levels in prethreshold ROP eyes by systemic intervention? A review of the role of oxygen, light adaptation state, and anemia in prethreshold ROP

PURPOSE

To review systemic modifiable factors that might downregulate pathologic levels of vascular endothelial growth factor (VEGF) in prethreshold retinopathy of prematurity (ROP), and thereby reduce the risk of blindness in affected infants.

METHODS

Review of the author's clinical experience as compared to the STOP-ROP study, and discussion and literature review of the potential effects of oxygen supplementation, light adaptation state, and correction of severe anemia on the course of prethreshold retinopathy of prematurity (ROP).

RESULTS

Moderate oxygen supplementation, combined with light adaptation to reduce retinal oxygen consumption and correction of severe anemia, were associated, in the author's experience, with improvement in the clinical course of prethreshold ROP. Withdrawal of these measures was often associated with deterioration of ROP.

CONCLUSION

Systemic measures can be taken that may reduce the risk of blindness in infants with prethreshold ROP. For those infants who require laser treatment for threshold ROP, prior efforts to moderate excessive levels of VEGF may improve the chances of a successful surgical result, by slowing the momentum of the disease.

Actions and therapeutic potential of G-CSF and GM-CSF in cardiovascular disease

Despite their names, the cytokines granulocyte- and granulocyte-macrophage-colony stimulating factor (G-CSF and GM-CSF respectively) have actions far beyond simply stimulating the proliferation of neutrophil and monocyte lineage cells. A comprehensive body of evidence now exists demonstrating that G-CSF and GM-CSF effectively mobilize bone-marrow-derived progenitor cells into the peripheral circulation. These mobilized progenitor cells can be conveniently harvested for use in reconstituting bone marrow by transplantation after myelo-ablative treatment of hematological malignancies. In addition, much evidence has recently emerged to suggest that these cytokines may have multiple direct and indirect beneficial cardiovascular effects--including neovascularization of ischemic myocardium and reducing the extent of myocardial damage after infarction. Based on this knowledge and a strong safety record in hematological applications, a number of early clinical trials have evaluated the use of G-CSF or GM-CSF in patients with both acute and chronic myocardial ischemia. Although the interpretation of these trials is complicated by heterogeneity in study design, small patient numbers and methodological concerns related to appropriate selection and blinding of patients, the results of ongoing larger phase II/III trials should soon be available to determine if these agents will be useful additions to the cardiovascular armamentarium.

Morphology and transfection study of human microvascular endothelial cell angiogenesis: an in vitro three-dimensional model

Microvascular endothelial cells from human neonatal foreskin were grown in vitro until a three-dimensional network of capillary-like structures was formed. All stages of the angiogenic cascade could be observed in this in vitro model, including the formation of an internal lumen. The microscopy focused on morphology, formation of an internal lumen, role of the extracellular matrix, polarity of the cells, and the time-course of the angiogenic cascade. Bright-field microscopy revealed cells arranged circularly side by side and the internal lumen of capillary-like structures was verified by electron microscopy. Immunolabeling revealed a peritubular localization of collagen IV. Reporter gene expression after the formation of capillary-like structures was marginally higher than control expression, but clearly lower than the expression of cells at the stage of proliferation. Highest transfection efficiencies were obtained using vectors with the CMV promoter and the long fragment of the Ets-1 promoter. This is a first study of transfection efficiencies mapped for stages of in vitro angiogenesis. We describe here the morphological features of a long-term in vitro model of angiogenesis of human microvascular endothelial cells that could be used for transfection studies, without the provision of an extracellular matrix substrate. The cells self-create their own extracellular matrix to proliferate and form a three-dimensional network of capillary-like structures with an internal lumen.

Enhanced generation of endothelial cells from CD34+ cells of the bone marrow in rheumatoid arthritis: Possible role in synovial neovascularization

OBJECTIVE

To examine the capacity of bone marrow CD34+ cells to generate endothelial cells, in order to assess the role of bone marrow in neovascularization in the synovium of rheumatoid arthritis (RA).

METHODS

CD34+ cells purified from the bone marrow of 13 patients with active RA and 9 control subjects (7 osteoarthritis [OA] patients and 2 healthy individuals) were cultured in the presence of stem cell factor (10 ng/ml) and granulocyte-macrophage colony-stimulating factor (1 ng/ml). After 18 days of incubation, the generation of endothelial cells was assessed by flow cytometry. The generation of endothelial cells was compared with the degree of vascularization in the synovial tissues and with the microvessel densities in the synovium, as determined by microscopy. The expression of vascular endothelial growth factor receptor 2/kinase insert domain receptor (KDR) messenger RNA (mRNA) in CD34+ cells was examined by quantitative reverse transcription-polymerase chain reaction.

RESULTS

The generation of CD14+ cells from bone marrow-derived CD34+ cells from RA patients was comparable to that from control subjects. However, the generation of von Willebrand factor (vWF)-positive cells and CD31+/vWF+ cells from RA bone marrow-derived CD34+ cells was significantly higher than that from control subjects (P = 0.004 and P = 0.030, respectively). The generation of vWF+ cells from bone marrow CD34+ cells correlated significantly with the microvessel densities in the synovial tissues (r = 0.569, P = 0.021). Finally, RA bone marrow CD34+ cells expressed KDR mRNA at higher levels than OA bone marrow CD34+ cells.

CONCLUSION

These results indicate that RA bone marrow CD34+ cells have enhanced capacities to differentiate into endothelial cells in relation to synovial vascularization. The data therefore suggest that bone marrow CD34+ cells might contribute to synovial neovascularization by supplying endothelial precursor cells and, thus, play an important role in the pathogenesis of RA.

Erythropoietin and hypoxia stimulate erythropoietin receptor and nitric oxide production by endothelial cells

Erythropoietin (EPO), a hypoxia-inducible cytokine, is required for survival, proliferation, and differentiation of erythroid progenitor cells. EPO can also stimulate proliferation and angiogenesis of endothelial cells that express EPO receptors (EPORs). In this study we investigated the EPO response of vascular endothelial cells at reduced oxygen tension (5% and 2%), in particular the effect of EPO on nitric oxide (NO) release. Endothelial nitric oxide synthase (eNOS) produces NO, which maintains blood pressure homeostasis and blood flow. We find that EPOR is inducible by EPO in primary human endothelial cells of vein (HUVECs) and artery (HUAECs) and cells from a human bone marrow microvascular endothelial line (TrHBMEC) to a much greater extent at low oxygen tension than in room air. We found a corresponding increase in eNOS expression and NO production in response to EPO during hypoxia. Stimulation of NO production was dose dependent on EPO concentration and was maximal at 5 U/mL. NO activates soluble guanosine cyclase to produce cyclic guanosine monophosphate (cGMP), and we observed that EPO induced cGMP activity. These results suggest that low oxygen tension increases endothelial cell capacity to produce NO in response to EPO by induction of both EPOR and eNOS. This effect of EPO on eNOS may be a physiologically relevant mechanism to counterbalance the hypertensive effects of increased hemoglobin-related NO destruction resulting from hypoxia-induced increased red cell mass.

Chronic abdominal pain caused by heterotopic ossification with functioning bone marrow: a case report and review of the literature

Heterotopic ossification is rarely seen after midline abdominal surgery. The etiology of heterotopic ossification is unknown. Although it is well recognized that heterotopic ossification may contain osteogenic cells and/or hematopoietic cells, to our knowledge, no case has ever been reported to have histologic evidence of hematopoiesis. We report the occurrence of heterotopic bone with bone marrow showing normal trilineage hematopoiesis in the incision scar of a woman who underwent gastric reduction surgery for the treatment of obesity. The literature regarding heterotopic ossification and extramedullary hematopoiesis is reviewed in this report, and discussion focuses on the mechanism of this pathophysiologic process.

Enhanced effect of vascular endothelial growth factor, thrombopoietin peptide agonist, SCF, and Flt3-L on LTC-IC and reporter gene transduction from umbilical cord blood CD34+ cells

BACKGROUND

Hemangioblastic precursors have been identified that give rise to both endothelial cells and HPCs, suggesting that common growth factor requirements may exist.

STUDY DESIGN AND METHODS

The effect of vascular endothelial growth factor (VEGF) in combination with thrombopoietin peptide agonist (TPOA), Flt-3 L (F), and SCF (S) on long-term culture-initiating cell (LTC-IC), CFU, differentiation, and transduction of cord blood (CB) CD34+ were evaluated up to 4 weeks in culture.

RESULTS

At Week 4, in cultures containing T/F/S and VEGF, the LTC-IC increased 1000-fold (from 37 +/- 8 to 37,012 +/- 14,329) with a frequency of 3.4 in 10,000 cells. In the T/F/S cultures without VEGF, the LTC-IC increased 675-fold (to 25,086 +/- 12,102) with a frequency of one LTC-IC in 10,000 cells. The addition of VEGF significantly increased (p < 0.05) the LTC-IC per 10,000 CB CD34+ cells. Transduction with reporter gene enhanced green fluorescent protein (EGFP), resulted in an increase in EGFP+ CFU at Week 1 and EGFP + LTC-IC at Weeks 1 and 4. The cells maintained their multilineage expression when cultured in conditions for erythroid, myeloid, or megakaryocytic differentiation. Peak percentage EGFP coexpression of GlyA and CD11b was 51 +/- 6 percent and 63 +/- 15 percent, respectively, at Week 2, while CD41a was 34 +/- 17 percent at Week 4.

CONCLUSION

T/F/S and VEGF have an enhanced effect on total LTC-IC output and frequency but do not appear to significantly alter the differentiation or transducibility characteristics of CB HPCs in vitro.

Inhibitory effects of bucillamine on the expression of vascular cell adhesion molecule-1 in human umbilical vein endothelial cells

Bucillamine (BUC) has been found to have beneficial effects in the treatment of rheumatoid arthritis (RA), in which the activation of endothelial cells plays an important role in the pathogenesis. The current studies examined the effect of BUC and its intramolecular disulfide form (BUC-ID) on the expression of adhesion molecules in human umbilical vein endothelial cells (HUVEC) stimulated with tumor necrosis factor-alpha (TNF-alpha). HUVEC (4 x 10(4)/well) were incubated with medium M199 containing heparin and 20% FCS with endothelial cell growth supplement (ECGS) for 24 h in the presence or absence of BUC or BUC-ID, after which the culture medium was replaced with ECGS free medium. Then the cultures were further carried out for additional 24 h with TNF-alpha (10 ng/ml) in the presence or absence of BUC or BUC-ID. BUC-ID, but not BUC, appeared to suppress the expression of VCAM-1 on HUVEC stimulated with TNF-alpha in a dose-response manner at its pharmacologically relevant concentrations (0.3-3.0 microg/ml), whereas only the 3 microg/ml concentration level of BUC-ID had a statistically significant effect, although the effect was relatively small. By contrast, lower concentrations of BUC-ID (1-3 microg/ml) suppressed the secretion of soluble VCAM-1 by HUVEC much more effectively. Of note, at the concentration of 3 microg/ml neither BUC nor BUC-ID significantly influenced the expression of ICAM-1 and E-selectin on TNF-alpha stimulated HUVEC. These results indicate that BUC-ID, but not BUC, specifically downregulates the surface expression of VCAM-1 as well as the release of soluble VCAM-1 by HUVEC stimulated with TNF-alpha. BUC-ID suppressed the production of solubleVCAM-1 by RA bone marrow CD34+ cells stimulated with SCF, GM-CSF and TNF-alpha more effectively than BUC. The data thus suggest that one of the mechanisms of action of BUC involves the inhibition of the activation of endothelial cells.

Plasma angiopoietin-1, angiopoietin-2 and Tie-2 in breast and prostate cancer: a comparison with VEGF and Flt-1

BACKGROUND

Angiogenesis is essential for tumour growth and metastasis, and is coordinated by several classes of growth factors mediating their effect through receptors linked, in turn, to tyrosine kinase. These growth factors include angiopoietin-1 (Ang-1), angiopoietin-2 (Ang-2) and vascular endothelial growth factor (VEGF), which act through receptors Flt-1 and Tie-2.

MATERIALS AND METHODS

In order to further determine abnormalities in levels of Ang-1, Ang-2, Tie-2, sFlt-1 and VEGF in human cancer (and their interrelationships), these molecules were measured in plasma from 30 patients with breast cancer, 30 patients with prostate cancer and 12 healthy controls per cancer group.

RESULTS

In breast cancer, levels of Ang-1 (P=0.0005), Ang-2 (P=0.0173), Tie-2 (P=0.0001), and VEGF (P=0.0001) were all significantly raised, and plasma levels of sFlt-1 (P=0.045) were significantly reduced compared with controls. However, in prostate cancer, only levels of VEGF and Tie-2 were significantly higher (both P=0.001). There were no significant differences between levels of any molecule between the two groups of cancer. The only difference between the healthy control groups was lower Ang-1 in the women compared with men. Significant correlations were found between levels of Ang-1 and Tie-2 both in breast (r=0.498, P=0.005) and prostate cancer (r=0.643, P=<0.001). Angiopoietin-1 was also positively correlated with Ang-2 in both breast (r=0.422, P=0.02) and prostate cancer (r=0.543, P=0.002).

CONCLUSIONS

Abnormal levels of Ang-1, Ang-2 and their receptor, Tie-2, are present in breast and prostate cancer, and their interrelationships may be important in the pathophysiology of these conditions.

Erythropoietin as an angiogenic factor

Erythropoietin (Epo) is produced by the fetal liver and adult kidney and is an essential stimulator of erythropoiesis. It has, however, been shown to modulate host cellular signal transduction pathway to perform many other functions. New sites of Epo production have been found, such as the female reproductive organs and central nervous system. This review summarizes the involvement of Epo in the regulation of angiogenesis in both normal and pathological conditions.

Angiogenesis and anti-angiogenesis in hematological malignancies

Although it is well established that the growth of solid tumors requires vigorous neovascularization, it has been assumed that leukemias and other hematological malignancies do not depend on angiogenesis. However, the role of angiogenesis in growth and survival of neoplastic cells of the hematopoietic system has recently been recognized, and provides a rationale for novel therapeutic approaches to hematological malignancy. This review summarizes the literature concerning the relationship between angiogenesis and disease progression of several hematological malignancies. It is becoming increasingly evident that agents that interfere with blood vessel formation also block tumor progression, and, accordingly, antiangiogenic therapy has gained much interest as a potential adjunct to conventional therapy of many hematological malignancies. Recent successful applications of antiangiogenic agents that interfere or block the progression of hematological malignancies are evaluated in light of recent demonstrations of potent angiogenic activity of several hematopoietic growth factors. A novel finding regarding the role of angiogenesis in hematological malignancies, which accounts for many clinical observations as well as the apparent independence of these tumors on marrow vascularity, is presented. The information presented in this review will facilitate the design of future clinical trials using antiangiogenic agents for the treatment of hematological malignancies and will provide a basis for the design of experiments undertaken to define the mechanisms involved, mechanisms that may shed new light on the pathology of hematological malignancies.

Pleiotrophic actions of erythropoietin

Erythropoietin is the prime regulator of red blood cell production. However, recent evidence suggests that the hormone has multiple effects outside the hematopoietic system. Functional receptors have been identified on a wide variety of normal and malignant cell types, and numerous biologic effects of the hormone on these cells have been observed both in vitro and in vivo. These findings are causing a reassessment of the understanding of erythropoietin physiology. Moreover, there are important implications for the use of recombinant erythropoietin in the clinical setting.

Erythropoietin: physiology and pharmacology update

This minireview is an update of a 1997 review on erythropoietin (EPO) in this journal. EPO is a 30,400-dalton glycoprotein that regulates red cell production. In the human, EPO is produced by peritubular cells in the kidneys of the adult and in hepatocytes in the fetus. Small amounts of extra-renal EPO are produced by the liver in adult human subjects. EPO binds to an erythroid progenitor cell surface receptor that includes a p66 chain, and, when activated, the p66 protein becomes dimerized. EPO receptor activation induces a JAK2 tyrosine kinase, which leads to tyrosine phosphorylation of the EPO receptor and several proteins. EPO receptor binding leads to intracellular activation of the Ras/mitogen-activated kinase pathway, which is involved with cell proliferation, phosphatidylinositol 3-kinase, and STATS 1, 3, 5A, and 5B transcriptional factors. EPO acts primarily to rescue erythroid cells from apoptosis (programmed cell death) to increase their survival. EPO acts synergistically with several growth factors (SCF, GM-CSF, 1L-3, and IGF-1) to cause maturation and proliferation of erythroid progenitor cells (primarily colony-forming unit-E). Oxygen-dependent regulation of EPO gene expression is postulated to be controlled by a hypoxia-inducible transcription factor (HIF-1alpha). Hypoxia-inducible EPO production is controlled by a 50-bp hypoxia-inducible enhancer that is approximately 120 bp 3' to the polyadenylation site. Hypoxia signal transduction pathways involve kinases A and C, phospholipase A(2), and transcription factors ATF-1 and CREB-1. A model has been proposed for adenosine activation of EPO production that involves protein kinases A and C and the phospholipase A(2) pathway. Other effects of EPO include a hematocrit-independent, vasoconstriction-dependent hypertension, increased endothelin production, upregulation of tissue renin, change in vascular tissue prostaglandins production, stimulation of angiogenesis, and stimulation of endothelial and vascular smooth muscle cell proliferation. Recombinant human EPO (rHuEPO) is currently being used to treat patients with anemias associated with chronic renal failure, AIDS patients with anemia due to treatment with zidovudine, nonmyeloid malignancies in patients treated with chemotherapeutic agents, perioperative surgical patients, and autologous blood donation. A novel erythropoiesis-stimulating factor (NESP, darbepoetin) has been synthesized and when compared with rHuEPO, NESP has a higher carbohydrate content (52% vs 40%), a longer plasma half-life, the amino acid sequence differs from that of native human EPO at five positions, and has been reported to maintain hemoglobin levels just as effectively in patients with chronic renal failure as rHuEPO at less frequent dosing. The use of rHuEPO and darbepoetin to enhance athletic performance is officially banned by most sports-governing bodies because the excessive erythrocytosis can lead to increased thrombogenicity and can cause deep vein, coronary, and cerebral thromboses.

Human bone marrow angiogenesis: in vitro modulation by substance P and neurokinin A

We have previously described a culture system for human bone marrow endothelial cells that organize into capillary tubes associated to pericytes. In the present work, we used this model to assess the angiogenic properties of tachykinins, which have been demonstrated to be involved in neuro-immuno-haematopoietic interactions. The substance P (SP) and neurokinin A (NKA) were similarly potent at increasing in vitro angiogenesis, via NK1 and NK2 receptors respectively. These mediators were not produced by cells in culture, suggesting that in vivo they may be released by nerve fibres in the bone marrow. Therefore, we looked for in situ innervation of the human bone marrow, unknown to date, using immunohistochemistry techniques. As in rodents, arterioles were largely innervated, associated with between one and 10 nerve fibres. Capillary innervation was more restrictive as a unique thin nerve fibre was found in the vicinity of only 6% of these vessels. Finally, no nerve fibres were observed in the vicinity of sinus walls. In conclusion, both in vitro results and the anatomical display of nerve fibres suggest a role in human bone marrow for the vasoactive neuropeptides SP and NKA, which were secreted into a perivascular location. These neural mediators might modulate blood flow in the bone marrow both in the short term by adjusting vascular tone and in the long term by inducing angiogenesis.

Erythropoietin and VEGF exhibit equal angiogenic potential

Erythropoietin (Epo) is a hormone regulating proliferation and differentiation of erythroid cells. The hypothesis that hematopoietic and endothelial cells share a common hemangioblast progenitor among others is based on the finding that both cell lineages express cell surface antigens like CD31 and CD34. In this study we investigated the angiogenic potential of recombinant human erythropoietin (rHuEpo) on endothelial cells derived from human adult myocardial tissue. In addition, we compared the angiogenic potential of rHuEpo to that of other cytokines (VEGF, aFGF) and combinations of growth factors. Samples of myocardial tissue (cardiac auricle) were obtained during coronary bypass surgery, embedded in a fibrin gel matrix, and cultured for 21 days. Capillary sprouting was measured with an eye-piece graticule under an inverted-phase contrast microscope. Tube-forming endothelial cells were characterized by immunohistochemistry and RT-PCR. Using a concentration of 2.5 U/ml, we found that rHuEpo stimulates capillary outgrowth up to 220%, compared to the nonstimulated physiological outgrowth. Epo therefore exhibits the same angiogenic potential on endothelial cells in our in vitro assay as VEGF(165) (230% increase). Erythropoietin stimulates capillary outgrowth in an in vitro angiogenesis assay using adult human myocardial tissue. This implies a role of erythropoietin in vasoproliferative processes. rHuEpo may serve as a direct angiogenic substance in patients with ischemic heart disease.

Angiogenesis in hematologic malignancies and its clinical implications

Angiogenesis is defined as a neoformation of blood vessels of capillary origin. Hematopoiesis is closely linked with angiogenesis, for they share a common ancestor, the hemangioblast. Although it is well established that growth in solid tumors is dependent on angiogenesis, its role in hematologic malignancies has not yet been clarified. In this review, the direct evidence, ie, increased microvessel density, and the indirect evidence, ie, elevated level of angiogenic factors or overexpression of messenger RNA or protein of angiogenic factors, for and against the role of angiogenesis in the development and progression of hematologic malignancies are presented.

In vivo activation of JAK2/STAT-3 pathway during angiogenesis induced by GM-CSF

Besides the regulation of hematopoiesis, granulocyte-macrophage colony-stimulating factor (GM-CSF) induces the expression of a functional program in cultured endothelial cells (ECs) related to angiogenesis and to the their survival in bone marrow microenvironment. ECs express the specific GM-CSF receptor that signals through the recruitment and the activation of Janus kinase (JAK)2 (Soldi et al., Blood 89, 863-872, 1987). We now report that GM-CSF in vivo induces angiogenesis and activates JAK-2 and signal transducers and activators of transcription (STAT)-3. This cytokine has an angiogenetic activity in chick chorioallantoic membrane (CAM) without recruitment of inflammatory cells and induces vessel sprouting from chicken aorta rings. When added to CAM, subnanomolar concentrations of GM-CSF cause a rapid phosphorylation in tyrosine residues of JAK-2 persisting at least for 10 min. Furthermore, we show that signal transducers and activators of transcription (STAT)-3, but not STAT-5, also are phosphorylated for 30 min after GM-CSF stimulation. AG-490, a JAK-2 inhibitor, reduced in a dose-dependent manner the angiogenic effect of GM-CSF in CAM. These findings provide the first evidence that the JAK-2/STAT-3 pathway is activated in vivo and participates in vessel formation triggered by GM-CSF.

The role of angiogenesis in hematologic malignancies

Several reports have highlighted the biologic relevance of angiogenesis in neoplastic disorders and its potential impact on prognosis. In this review, we focus on recent findings about angiogenesis and angiogenetic factors in hematologic malignancies. We summarize the body of evidence supporting the hypothesis that a common progenitor gives rise to cells of both the endothelial and the hematopoietic lineages, and the current knowledge about the involvement of normal stromal cells in bone marrow angiogenesis. We also discuss the methodological aspects of microvessel count as a measure of tumor angiogenesis. Finally, we describe the current therapeutic role of angiogenesis inhibitors and possible future strategies involving these agents.