Cardiovascular Research

Cardiovascular Research 2003 57(3):816-823; doi:10.1016/S0008-6363(02)00776-9
© 2003 by European Society of Cardiology

This Article Abstract FREE Full Text (PDF) E-letters: Submit a response Alert me when this article is cited Alert me when E-letters are posted Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to My Personal Archive Download to citation manager Request Permissions Disclaimer Google Scholar Articles by Nakul-Aquaronne, D. Articles by Frelin, C. Search for Related Content PubMed PubMed Citation Articles by Nakul-Aquaronne, D. Articles by Frelin, C. Social Bookmarking          What's this?

Copyright © 2003, European Society of Cardiology

Coexpression of endothelial markers and CD14 by cytokine mobilized CD34⁺ cells under angiogenic stimulation

Danièle Nakul-Aquaronne, Jacques Bayle and Christian Frelin^*

Institut de Pharmacologie Moléculaire et Cellulaire du CNRS, 660 route des Lucioles, 06560 Valbonne, France

^* Corresponding author. Tel.: +33-4-9395-7755; fax: +33-4-9395-7708. frelin{at}ipmc.cnrs.fr

Received 14 August 2002; accepted 11 November 2002

	Abstract

Top Abstract 1. Introduction 2. Methods 3. Results 4. Discussion References

 
Objective: A subset of adult peripheral blood leukocytes functions as endothelial progenitor cells that incorporate into the vasculature in animal models of neovascularization. The basic mechanisms by which differentiation proceeds are still unclear. This study analyses the in vitro differentiation of cytokine mobilized, human CD34⁺ cells. Methods: Granulocyte-monocyte colony stimulating factor mobilized human CD34⁺ cells were isolated and grown in culture in the presence of vascular endothelial growth factor (50 ng/ml) and basic fibroblast growth factor (10 ng/ml). Their differentiation was followed using cytological and immunohistochemical techniques. Fibronectin-coated culture dishes or three-dimensional cultures were used. Results: CD34⁺ cells grown on fibronectin-coated dishes differentiated along the granulocytic and monocytic/macrophage lineages with no evidence for an endothelial cell differentiation. CD14⁺ macrophages appeared in long-term culture and then acquired endothelial cell markers such as VE-cadherin, the endothelial form of NO synthase and the von Willebrand factor. Yet they were unable to form tubular structures in Matrigel^®. Only typical macrophages were observed in Matrigel^®. Conclusion: Angiogenic stimulation of CD34⁺ precursor cells leads to cells that expressed mixed macrophage and endothelial cell properties. They could represent an intermediate phenotype in the pathway that leads to mature endothelial cells.

KEYWORDS bFGF, basic fibroblast growth factor; BSA, bovine serum albumin; GM-CSF, granulocyte macrophage colony stimulating factor; MGG, May-Grünwald Giemsa; NOS, NO synthase; PBS, phosphate buffered saline; VEGF, vascular endothelial growth factor

	1. Introduction

Top Abstract 1. Introduction 2. Methods 3. Results 4. Discussion References

 
Angiogenesis and vasculogenesis are two processes involved in the formation of blood vessels. Vasculogenesis is fundamental for the development of a primary vasculature in the embryo [1–3]. The earliest site of vasculogenesis is the yolk sac where extraembryonic mesodermal cells differentiate into blood islands composed of hematopoietic and endothelial cells. The close association of the hematopoietic and endothelial lineages has led to the hypothesis that they arise from a common precursor, the hemangioblast. It is now supported by experimental evidence: posterior mesodermal VEGFR-2⁺ (vascular endothelial growth factor receptor 2) cells have the capacity to differentiate into endothelial and hematopoietic cells [4]. In the same way, blast cell colonies from embryonic stem cell-derived embryoid bodies contain the common precursor of the hematopoietic and endothelial lineages [5]. The interconnections between these two systems suggest important inductive relationships [6]. As a matter of fact, a VEGFR-2-mediated signal is required for the migration and expansion of hematopoietic/endothelial progenitors [7].

Angiogenesis occurs during development and post-natal life. It results from the proliferation, migration and remodeling of differentiated endothelial cells derived from preexisting blood vessels. It has recently been proposed that new vessels might also be formed from circulating endothelial progenitor cells. These cells have been isolated from CD133⁺ or CD34⁺ cell subsets. They acquire characteristic properties of endothelial cells such as expressions of VEGFR-2, Tie-2 receptor, CD31, E-selectin, endothelial constitutive nitric oxide synthase (NOS3). They bind selectively the lectin Ulex europaeus agglutinin-1 and incorporate acetylated low-density lipoproteins [8–11]. Most importantly, injection of isolated CD34⁺ cells or cultivated endothelial precursor cells accelerates blood-flow restoration in diabetic mice [12], improves neovascularization in ischemic hind limbs [13] and cardiac function [14,15]. In this study we analyzed differentiation of cytokine mobilized human CD34⁺ cells in the presence of endothelial cell mitogens. Results show appearance of typical CD14⁺ macrophages with unexpected endothelial cell markers.

	2. Methods

Top Abstract 1. Introduction 2. Methods 3. Results 4. Discussion References

 
2.1 Specimens
The study included 11 specimens of GM-CSF (granulocyte macrophage-colony stimulating factor) cytokine-mobilized leukapheresis products from patients with various hematological disorders (chronic myeloïd leukemia, Hodgkin's disease, chronic lymphocytic leukemia, multiple myeloma, acute myelomonocytic leukemia, Ewing's sarcoma, and lymphoma). Although this cohort was not homogenous, results obtained were homogenous and independent of the disease considered. Mononuclear cells were isolated by density gradient centrifugation over Ficoll-Paque^® (density 1.077 g/ml) (Pharmacia Biotech, Uppsala, Sweden) for 30 min at 600xg. Two additional washes were performed at 300xg and 200xg for 10 min in phosphate-buffered saline (PBS; Amresco, Solon, OH, USA) supplemented with 0.5% bovine serum albumin (BSA; Life Technologies, Karlsruhe, Germany) to remove platelets. Mononuclear cells were suspended in PBS supplemented with 0.5% BSA and 0.6% anticoagulant citrate dextrose-formula A. All procedures followed were in accordance with institutional guidelines and the principles outlined in the Declaration of Helsinki.

2.2 Positive selection of CD34⁺ cells by magnetic cell sorting
After blocking the Fc receptor, isolated mononuclear cells were indirectly magnetically labeled using a monoclonal hapten-conjugated CD34 antibody (QBend 10, mouse isotype IgG1) and an anti-hapten antibody coupled to microbeads (CD34 Progenitor Cell Isolation kit, Miltenyi Biotec, Bergisch Gladbach, Germany). The cells were then processed through a MACS magnetic separation column (Miltenyi Biotec) to obtain purified CD34⁺ cells.

2.3 Culture of human CD34⁺ cells
Isolated CD34⁺ cells were seeded into 35-mm culture dishes coated with 0.1 mg/ml fibronectin from bovine plasma (Sigma, St. Louis, MO, USA). The cultures were performed in Iscove's Modified Dulbecco's Medium (BioWhittaker, Walkersville, MD, USA) supplemented with 10% fetal bovine serum (Life Technologies), 10 µg/ml bovine insulin (Sigma), 2 mmol/l L-glutamine and 100 U/ml penicillin–streptomycin. Recombinant human vascular endothelial cell growth factor (VEGF; 50 ng/ml, PeproTech, Rocky Hill, NJ, USA) and recombinant human basic fibroblast growth factor (bFGF; 10 ng/ml; Life Technologies) were used as growth factors. Cultures were incubated at 37 °C in 5% CO₂. Media were changed twice a week.

Three-dimensional gels were prepared with Matrigel^® (Becton Dickinson) at a 1:2 dilution in PBS and at 150 µl/cm² of growth surface. Brain capillary endothelial cells [16] were used as controls.

2.4 Immunofluorescence staining
Cells were cytospun onto glass slides at 800 rev./min for 10 min and air-dried before 15-min fixation in PBS, 4% paraformaldehyde at 20 °C. After two washes with PBS, they were permeabilized with 0.2% Triton X100 in PBS for 10 min and washed again. After blocking with PBS, 1% BSA, 4% donkey serum (Sigma) for 15 min and with PBS, 1% BSA, 0.4% donkey serum twice for 10 min, cells were analyzed for the expression of CD14 (goat polyclonal IgG), NOS3 (rabbit polyclonal IgG), VE-cadherin (mouse monoclonal IgG1) (all from Santa Cruz Biotechnology, Santa Cruz, CA, USA) or von Willebrand factor (rabbit polyclonal; Sigma). The primary antibodies (1:1000 dilution) were incubated for 90 min and cells were washed twice for 10 min with PBS, 1% BSA, 0.4% donkey serum. Staining was developed with a rhodamine-conjugated donkey anti-goat IgG secondary antibody or a fluorescein-isothiocyanate-conjugated donkey anti-rabbit IgG and anti-mouse IgG secondary antibodies (Santa Cruz Biotechnology) (both at a 1:400 dilution). Following two washes with PBS, 1% BSA, 0.4% donkey serum, the slides were mounted with a permanent mounting medium (Fluoprep^®; BioMérieux).

2.5 Cytohistochemistry
May-Grünwald Giemsa (MGG; Biolyon) stain was used. Cells were fixed and stained with undiluted and with a 1:2 dilution of May-Grünwald in PBS, pH 6.6 for 3-min periods. They were then exposed to Giemsa, diluted to 1:10 in the same buffer, for 15 min, rinsed thoroughly and air-dried. A monocytic esterase stain was performed using the -naphthyl acetate esterase kit (Sigma). Specific inhibition of esterase activity by sodium fluoride was studied. Myeloperoxidase activity was demonstrated using benzidine (Sigma) as substrate. After fixing air dried cytospun cells with 0.5% copper sulfate for 30 s to 1 min at room temperature and leaving to drain, the fixed cells were immersed in the working substrate (4% Giemsa, 0.5% benzidine, 0.5% H₂O₂ 10 vol.) for 20 min in the dark. Matrigel samples were fixed and stained as described for cytospun cells.

	3. Results

Top Abstract 1. Introduction 2. Methods 3. Results 4. Discussion References

 
3.1 In vitro differentiation
GM-CSF-mobilized CD34⁺ cells were isolated from leukapheresis products using positive magnetic bead selection. Cells were seeded onto fibronectin-coated culture dishes in the presence of angiogenic growth factors VEGF (50 ng/ml) and bFGF (10 ng/ml). Attached cells first appeared as single round cells. After 1 day in culture, some cells started to elongate. Most developed cytoplasmic expansions in various directions. Some cells were spindle-shaped. An important anisopoïkilocytosis was noticed after 1 week of culture. Cultures consisted of mixtures of small and large round cells, spindle-shaped cells and cells with multiple and long cytoplasmic expansions. Clusters of cells were present. They formed loose cobblestone-like structures that resembled endothelial cell colonies. The number of clusters and their sizes increased with time in culture. However, cultures never reached complete confluence.

Cells at different stages of in vitro development were first characterized using the classical MGG stain. Freshly isolated CD34⁺ cells appeared as a homogeneous population of blasts with a high nucleocytoplasmic ratio, a diffuse chromatin pattern, visible nucleoli and a basophilic cytoplasm (Fig. 1A). After 7 days, cultures were heterogeneous. They mainly consisted of blasts, myeloblasts and promyelocytes. Few monocytes/macrophages and rare neutrophil polymorphonuclear cells were also present. These different cell types may be seen in close juxtaposition in the same microscope field (Fig. 1B). By 10 days of culture, the number of blasts and myeloblasts decreased. Some monoblasts were still recognized (Fig. 1D) and most of the cell population consisted of mature granular cells and monocytes with or without vacuoles (Fig. 1C).

View larger version (152K): [in this window] [in a new window] [Download PowerPoint slide]   Fig. 1 CD34+ cells differentiate into monocytes and granulocytes in the presence of VEGF and bFGF. CD34+ cells were cultured onto fibronectin for various periods of time and stained with MGG. (A) Freshly isolated CD34+ cells. (B) 7-day-old culture showing numerous blasts (Bl) and myeloblasts (MB), some promyelocytes (PM) and few monocytes/macrophages (Ma). (C, D) 11-day-old cultures showing some monoblasts (Mob) (D), more mature granular cells and monocytes/macrophages (C). Panel D further documents immature cells with cytoplasmic expansions with phagocytosis activity against yeasts. (E, F) 42-day-old cultures showing monocytes and giant multinucleated macrophages.

 
After 20 days of culture, spindle-shaped cells often aligned to form long linear threads that crossed the whole culture dishes. These structures may be interpreted as ongoing tubulogenesis. Cells in these threads were mononuclear cells with a low nucleocytoplasmic ratio characteristic of monocyte/macrophages.

At day 40, most cells were macrophages. They were either isolated or formed intercrossed thread-like structures. Other cells were multinucleated giant cells (about 150 µm diameter) (Fig. 1E and F).

To confirm the presence of macrophages, cultures were inoculated with yeasts and stained with MGG. Fig. 1D (bottom) shows two cells with short cytoplasmic expansions with yeasts inside. On the upper left, a cell produced a pseudopode to phagocytose yeasts. Another instance of phagocytosis is shown at the center of Fig. 2A. Thus, cells identified as immature mononuclear cells and macrophages were capable of phagocytosis.

View larger version (136K): [in this window] [in a new window] [Download PowerPoint slide]   Fig. 2 Cytochemical analysis of CD34+ derived cells cultured onto fibronectin. (A, B) A strong myeloperoxidase activity was associated to some of the blasts and the mature granular cells in 11-day- (A) and 33-day-old (B) cultures. Myeloperoxidase activity appeared as blue–brown granules in granulocytes. (C, D) A positive -naphthyl acetate esterase reaction was associated to monocytic cells. Granulocytes were weakly positive. Esterase activity appeared as brown–black deposits (C). Most of the esterase activity was inhibited by sodium fluoride. The inhibited cells were all from the monocytic lineage (D).

 
3.2 Cytochemical analysis
Cytochemical techniques were then used to further ascertain the granulocytic/monocytic differentiation. A strong positive myeloperoxidase reaction was detected in most of the cells in 11-day-old cultures. For instance, Fig. 2A shows the presence of brown or blue granules in cells identified morphologically as myeloblasts, promyelocytes or myelocytes. Fig. 2B further shows two strongly positive cells with lobulated nuclei characteristic of neutrophils in a 33-day-old culture. These confirmed the granulocytic differentiation that was characterized previously with the MGG stain.

We then used an -naphthyl acetate esterase assay. A sodium fluoride sensitive activity is characteristic of the monocyte lineage. Fig. 2C shows that most cells in 33-day-old cultures were positive. A stronger staining was observed however with cells that were identified as macrophages using MGG (Fig. 2C). Fig. 2D shows that the esterase activity was inhibited by sodium fluoride only in these cells. Cells identified as macrophages in 40-day-old cultures including giant cells and elongated cells that formed threads had a weak myeloperoxidase activity. They showed strong esterase activity, which was inhibited by sodium fluoride. This confirmed their monocytic properties.

Taken together these results suggested that cytokine mobilized CD34⁺ cells mainly differentiated along the granulocytic and monocytic lineages.

3.3 Cell differentiation in three-dimensional gels
A well-known characteristic of endothelial cells is the possibility to form a network of tubular structures when grown in three-dimensional gels. Freshly isolated CD34⁺ cells and CD34⁺ derived cells (at different stages of their in vitro differentiation) were grown on Matrigel^®. Tube formation was never observed. Formation of a dense capillary-like network was however observed with brain capillary endothelial cells. Cells grown on Matrigel^® were harvested and characterized. At day 7, only monoblasts and mature macrophages were observed. At day 13, more macrophages and promonocytes were present. All cells in aged cultures were macrophages. The monocytic lineage was confirmed by a strong esterase activity, which was inhibited by sodium fluoride. Thus, Matrigel^® conditions favored a rapid differentiation of CD34⁺ cells along the monocytic lineage. Results also indicated that mature endothelial cells were not present in our cultures.

3.4 Coexpression of endothelial and monocyte/macrophage markers
We then analyzed expressions of VE-cadherin, NOS3 and von Willebrand factor. Experiments also included CD14, a marker of activated macrophages. Freshly isolated CD34⁺ cells were negative for all markers tested. After 19 days in vitro, granulocytic cells were negative for all markers tested. Monocytes did not express endothelial cell markers. Some of them were CD14⁺. After 39 days of culture, most macrophages were strongly positive for CD14 (Fig. 3C). Surprisingly, they were also positive for VE-cadherin, NOS3 and von Willebrand factor (Fig. 3). Finally, Fig. 4 documents a clear coexpression of CD14, a macrophage marker, and VE-cadherin, an endothelial cell marker, by the same cells in a 39-day-old culture. All monocyte/macrophages obtained in Matrigel^® cultures were negative for CD14, VE-cadherin, NOS3 or the von Willebrand factor.

View larger version (169K): [in this window] [in a new window] [Download PowerPoint slide]   Fig. 3 Expression of endothelial cell markers by cells derived from CD34+ cells. Cells from 39-day-old cultures were labeled with antibodies directed against VE-cadherin (A), NOS3 (B), CD14 (C) and von Willebrand factor (D).

 

View larger version (87K): [in this window] [in a new window] [Download PowerPoint slide]   Fig. 4 Co-expression of VE-cadherin and CD14 by cultured macrophages; 39-day-old cells were double immunostained for VE-cadherin (A) and CD14 (B).

 

	4. Discussion

Top Abstract 1. Introduction 2. Methods 3. Results 4. Discussion References

 
All results indicated that GM-CSF mobilized CD34⁺ cells were committed to granulocytic and monocytic pathways. The granulocytic differentiation was ascertained by the sequential appearance of myeloblasts, promyelocytes, myelocytes, metamyelocytes, neutrophils and by their characteristic strong myeloperoxidase activity. The monocytic differentiation was ascertained by the sequential appearance of monoblasts, promonocytes, monocytes/macrophages, expressions of CD14 and of a sodium fluoride sensitive esterase activity and active phagocytosis. The absence of mature endothelial cells was indicated by the observation that cells did not form tubular networks in Matrigel^®. These results were surprising for CD34⁺ cells have been reported to give rise to endothelial cells after in vitro stimulation with VEGF and bFGF (see Introduction). An obvious possibility is that endothelial progenitor cells, which comprise only a subset of CD34⁺ cells [17,18], were poorly represented in GM-CSF mobilized leukapheresis products.

It is of interest to note however that macrophages derived from CD34⁺ cells did acquire some properties of endothelial cells. In long-term cultures, cells developed an endothelial-like phenotype characterized by expressions of VE-cadherin, NOS3 and the von Willebrand factor. Cells retained however a clear macrophage phenotype as evidenced by the expression of CD14.

Two groups have recently reported that CD34^–/CD14⁺ macrophages develop an endothelial cell phenotype under angiogenic stimulation [19,20]. This phenotype is characterized by the formation of tubular-like structures in Matrigel^® in addition to the presence of VE-cadherin, NOS3 and the von Willebrand factor. CD14 is lost during this process. It may represent a more mature state of endothelial cells. A simple hypothesis to account for all these results could be that CD34⁺ derived monocytes differentiate into CD14⁺ monocytes, which then express VE-cadherin, NOS3 and the von Willebrand factor. Endothelial-like cells may then lose expression of CD14 and acquire the capacity to form tubular structures in Matrigel^®. The first steps would be observed when CD34⁺ cells were used as starting material. The last steps would be observed when more mature CD34^–/CD14⁺ cells were used as starting material.

Endothelial-like cells were only observed when CD34⁺ cells were grown on fibronectin-coated dishes. No expression of VE-cadherin, NOS3 or the von Willebrand factor could be observed in monocytes that had developed in Matrigel^®. This indicates that the differentiation pathway followed by the cells is dependent on local conditions. Whether endothelial-like cells similar to those observed in our cell culture system exist in vivo is not currently known.

In conclusion our results confirmed previous findings [19,20] that pointed out complex relationships between monocyte/macrophages and endothelial cells. We show here that an angiogenic stimulation of GM-CSF mobilised CD34+ cells gives rise to cells with mixed macrophage/endothelial cell properties. Whether such cells are present in the human circulation and represent some form of circulating endothelial cells is not known. A more interesting hypothesis is that these cells accumulate in hypoxic tissues and contribute to hypoxic angiogenesis. At least our results indicate that VE-cadherin, NOS3 and the von Willebrand factor should not be considered as specific for endothelial cells.

Time for primary review 33 days.

	Acknowledgements

 
The CNRS and the Fondation de France supported this work.

	References

Top Abstract 1. Introduction 2. Methods 3. Results 4. Discussion References

 

1. Hirashima M., Kataoka S., Nishikawa S., Matsuyoshi N., Nishikawa S.-I. Maturation of embryonic stem cells into endothelial cells in an in vitro model of vasculogenesis. Blood (1999) 93:1253–1263.[Abstract/Free Full Text]
2. Balconi G., Spagnuolo R., Dejana E. Development of endothelial cell lines from embryonic stem cells. A tool for studying genetically manipulated endothelial cells in vitro. Arterioscler Thromb Vasc Biol (2000) 20:1443–1451.[Abstract/Free Full Text]
3. Vittet D., Prandini M.H., Berthier R., et al. Embryonic stem cells differentiate in vitro to endothelial cells through successive maturation steps. Blood (1996) 88:3424–3431.[Abstract/Free Full Text]
4. Eichmann A., Corbel C., Le Douarin N.M. Segregation of the embryonic vascular and hemopoietic systems. Biochem Cell Biol (1998) 76:939–946.[CrossRef][Web of Science][Medline]
5. Choi K., Kennedy M., Kazarov A., Papadimitriou J.C., Keller G. A common precursor for hematopoietic and endothelial cells. Development (1998) 125:725–732.[Abstract]
6. Choi K. Hemangioblast development and regulation. Biochem Cell Biol (1998) 76:947–956.[CrossRef][Web of Science][Medline]
7. Schuh A.C., Faloon P., Hu Q.-L., Bhimani M., Choi K. In vitro hematopoietic and endothelial potential of flk-1^–/– embryonic stem cells and embryos. Proc Natl Acad Sci USA (1999) 96:2159–2164.[Abstract/Free Full Text]
8. Asahara T., Murohara T., Sullivan A., et al. Isolation of putative progenitor endothelial cells for angiogenesis. Science (1997) 275:964–967.[Abstract/Free Full Text]
9. Shi Q., Rafii S., Hong-De Wu M., Wijelath E.S., et al. Evidence for circulating bone marrow-derived endothelial cells. Blood (1998) 92:362–367.[Abstract/Free Full Text]
10. Boyer M., Townsend L.E., Vogel L.M., et al. Isolation of endothelial cells and their progenitor cells from human peripheral blood. J Vasc Surg (2000) 31:181–189.[CrossRef][Web of Science][Medline]
11. Peichev M., Naiyer A.J., Pereira D., et al. Expression of VEGFR-2 and AC133 by circulating human CD34⁺ cells identifies a population of functional endothelial precursors. Blood (2000) 95:952–958.[Abstract/Free Full Text]
12. Schatteman G.C., Hanlon H.D., Jiao C., Dodds S.G., Christy B.A. Blood-derived angioblasts accelerate blood-flow restoration in diabetic mice. J Clin Invest (2000) 106:571–578.[Web of Science][Medline]
13. Kalka C., Masuda H., Takahashi T., et al. Transplantation of ex vivo expanded endothelial progenitor cells for therapeutic neovascularization. Proc Natl Acad Sci USA (2000) 97:3422–3427.[Abstract/Free Full Text]
14. Kocher A.A., Schuster M.D., Szabolcs M.J., et al. Neovascularization of ischemic myocardium by human bone-marrow-derived angioblasts prevents cardiomyocyte apoptosis, reduces remodeling and improves cardiac function. Nat Med (2001) 7:430–436.[CrossRef][Web of Science][Medline]
15. Kawamoto A., Gwon H.C., Iwaguro H., et al. Therapeutic potential of ex vivo expanded endothelial progenitor cells for myocardial ischemia. Circulation (2001) 103:634–637.[Abstract/Free Full Text]
16. Vigne P., Champigny G., Marsault R., et al. A new type of amiloride sensitive cationic channel in endothelial cells from brain microvessels. J Biol Chem (1989) 264:7663–7668.[Abstract/Free Full Text]
17. Yin A.H., Miraglia S., Zanjani E.D., et al. AC133, a novel marker for human hematopoietic stem and progenitor cells. Blood (1997) 90:5002–5012.[Abstract/Free Full Text]
18. Gehling U.M., Ergün S., Schumacher U., et al. In vitro differentiation of endothelial cells from AC133-positive progenitor cells. Blood (2000) 95:3106–3112.[Abstract/Free Full Text]
19. Schmeisser A., Garlichs C.D., Zhang H., et al. Monocytes coexpress endothelial and macrophagic lineage markers and form cord-like structures in Matrigel^® under angiogenic conditions. Cardiovasc Res (2001) 49:671–680.[Abstract/Free Full Text]
20. Fernandez-Pujol B., Lucibello F.C., Gehling U.M., et al. Endothelial like cells derived from human CD14 positive monocytes. Differentiation (2000) 65:287–300.[CrossRef][Web of Science][Medline]

CiteULike    Connotea    Del.icio.us    What's this?

This article has been cited by other articles:

				E. Lucchinetti, S. M. Zeisberger, I. Baruscotti, J. Wacker, J. Feng, K. Zaugg, R. Dubey, A. H. Zisch, and M. Zaugg Stem Cell-Like Human Endothelial Progenitors Show Enhanced Colony-Forming Capacity After Brief Sevoflurane Exposure: Preconditioning of Angiogenic Cells by Volatile Anesthetics Anesth. Analg., October 1, 2009; 109(4): 1117 - 1126. [Abstract] [Full Text] [PDF]

				W. Wojakowski, M. Kazmierski, B. Korzeniowska, and M. Tendera Link between erythropoietin release and mobilization of endothelial progenitor cells in acute myocardial infarction Eur. Heart J., August 1, 2007; 28(15): 1785 - 1786. [Full Text] [PDF]

				A. Casamassimi, M. L. Balestrieri, C. Fiorito, C. Schiano, C. Maione, R. Rossiello, V. Grimaldi, V. Del Giudice, C. Balestrieri, B. Farzati, et al. Comparison Between Total Endothelial Progenitor Cell Isolation Versus Enriched Cd133+ Culture J. Biochem., April 1, 2007; 141(4): 503 - 511. [Abstract] [Full Text] [PDF]

				J. Glod, D. Kobiler, M. Noel, R. Koneru, S. Lehrer, D. Medina, D. Maric, and H. A. Fine Monocytes form a vascular barrier and participate in vessel repair after brain injury Blood, February 1, 2006; 107(3): 940 - 946. [Abstract] [Full Text] [PDF]

				S. M. Bauer, R. J. Bauer, and O. C. Velazquez Angiogenesis, Vasculogenesis, and Induction of Healing in Chronic Wounds Vascular and Endovascular Surgery, July 1, 2005; 39(4): 293 - 306. [Abstract] [PDF]

This Article Abstract FREE Full Text (PDF) E-letters: Submit a response Alert me when this article is cited Alert me when E-letters are posted Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to My Personal Archive Download to citation manager Request Permissions Disclaimer Google Scholar Articles by Nakul-Aquaronne, D. Articles by Frelin, C. Search for Related Content PubMed PubMed Citation Articles by Nakul-Aquaronne, D. Articles by Frelin, C. Social Bookmarking          What's this?

Online ISSN 1755-3245 - Print ISSN 0008-6363

Copyright © 2009 European Society of Cardiology

Oxford Journals Oxford University Press

• Site Map
• Privacy Policy
• Frequently Asked Questions

Other Oxford University Press sites: Oxford University Press Oxford Journals China Oxford Journals Japan American National Biography Booksellers' Information Service Children's Fiction and Poetry Children's Reference Corporate & Special Sales Dictionaries Dictionary of National Biography Digital Reference English Language Teaching Higher Education Textbooks Humanities International Education Unit Law Medicine Music Online Products Oxford English Dictionary Reference Rights and Permissions Science School Books Social Sciences Very Short Introductions World's Classics