Serum factors involved in human microvascular endothelial cell morphogenesis

Extracellular Vesicles and Thrombogenicity in Atrial Fibrillation

Extracellular vesicles (EVs) are defined as a heterogenic group of lipid bilayer vesicular structures with a size in the range of 30-4000 nm that are released by all types of cultured cells. EVs derived from platelets, mononuclears, endothelial cells, and adipose tissue cells significantly increase in several cardiovascular diseases, including in atrial fibrillation (AF). EVs are engaged in cell-to-cell cooperation, endothelium integrity, inflammation, and immune response and are a cargo for several active molecules, such as regulatory peptides, receptors, growth factors, hormones, and lipids. Being transductors of the intercellular communication, EVs regulate angiogenesis, neovascularization, coagulation, and maintain tissue reparation. There is a large amount of evidence regarding the fact that AF is associated with elevated levels of EVs derived from platelets and mononuclears and a decreased number of EVs produced by endothelial cells. Moreover, some invasive procedures that are generally performed for the treatment of AF, i.e., pulmonary vein isolation, were found to be triggers for elevated levels of platelet and mononuclear EVs and, in turn, mediated the transient activation of the coagulation cascade. The review depicts the role of EVs in thrombogenicity in connection with a risk of thromboembolic complications, including ischemic stroke and systemic thromboembolism, in patients with various forms of AF.

Fatty acids rather than hormones restore in vitro angiogenesis in human male and female endothelial cells cultured in charcoal-stripped serum

Charcoal-stripped serum (CSS) is a well-accepted method to model effects of sex hormones in cell cultures. We have recently shown that human endothelial cells (ECs) fail to growth and to undergo in vitro angiogenesis when cultured in CSS. However, the mechanism(s) underlying the CSS-induced impairment of in vitro EC properties are still unknown. In addition, whether there is any sexual dimorphism in the CSS-induced EC phenotype remains to be determined. Here, by independently studying human male and female ECs, we found that CSS inhibited both male and female EC growth and in vitro angiogenesis, with a more pronounced effect on male EC sprouting. Reconstitution of CSS with 17-β estradiol, dihydrotestosterone, or the lipophilic thyroid hormone did not restore EC functions in both sexes. On the contrary, supplementation with palmitic acid or the acetyl-CoA precursor acetate significantly rescued the CSS-induced inhibition of growth and sprouting in both male and female ECs. We can conclude that the loss of metabolic precursors (e.g., fatty acids) rather than of hormones is involved in the impairment of in vitro proliferative and angiogenic properties of male and female ECs cultured with CSS.

In vitro pre-vascularisation of tissue-engineered constructs A co-culture perspective

In vitro pre-vascularization is one of the main vascularization strategies in the tissue engineering field. Culturing cells within a tissue-engineered construct (TEC) prior to implantation provides researchers with a greater degree of control over the fate of the cells. However, balancing the diverse range of different cell culture parameters in vitro is seldom easy and in most cases, especially in highly vascularized tissues, more than one cell type will reside within the cell culture system. Culturing multiple cell types in the same construct presents its own unique challenges and pitfalls. The following review examines endothelial-driven vascularization and evaluates the direct and indirect role other cell types have in vessel and capillary formation. The article then analyses the different parameters researchers can modulate in a co-culture system in order to design optimal tissue-engineered constructs to match desired clinical applications.

An active form of sphingosine kinase-1 is released in the extracellular medium as component of membrane vesicles shed by two human tumor cell lines

Expression of sphingosine kinase-1 (SphK-1) correlates with a poor survival rate of tumor patients. This effect is probably due to the ability of SphK-1 to be released into the extracellular medium where it catalyzes the biosynthesis of sphingosine-1-phosphate (S1P), a signaling molecule endowed with profound proangiogenic effects. SphK-1 is a leaderless protein which is secreted by an unconventional mechanism. In this paper, we will show that in human hepatocarcinoma Sk-Hep1 cells, extracellular signaling is followed by targeting the enzyme to the cell surface and parallels targeting of FGF-2 to the budding vesicles. We will also show that SphK-1 is present in a catalitycally active form in vesicles shed by SK-Hep1 and human breast carcinoma 8701-BC cells. The enzyme substrate sphingosine is present in shed vesicles where it is produced by neutral ceramidase. Shed vesicles are therefore a site for S1P production in the extracellular medium and conceivably also within host cell following vesicle endocytosis.

Role of Rho kinase in sphingosine 1-phosphate-mediated endothelial and smooth muscle cell migration and differentiation

The role of sphingosine 1-phosphate (S1P)-induced Rho kinase (ROCK) activation in the angiogenic responses of pulmonary artery-derived endothelial cells (PAEC) and smooth muscle cells (PASMC) was examined. S1P, a biologically active phospholipid that regulates angiogenesis, promoted PAEC chemotaxis and capillary morphogenesis; furthermore, this activity was unaltered by pretreatment with the pharmacological inhibitor of ROCK, H1152. In contrast, S1P (500 nM) significantly inhibited spontaneous PASMC chemotaxis and differentiation; however, this inhibition was eradicated upon H1152 pretreatment. Similarly, PASMCs transfected with ROCK II siRNA diminished S1P-induced inhibition of the development of multi-cellular structures. Analysis by RT-PCR identified the presence of S1P(1) and S1P(3) receptors on both PAECs and PASMCs, while S1P(2) receptor expression was confined to only PASMCs. Consistent with this observation, the S1P(1) and S1P(3) receptor antagonist, VPC23019, virtually abolished the S1P-initiated PAEC differentiation but did not impede the S1P-induced inhibition of PASMC differentiation. However, the S1P(2) receptor antagonist, JTE013, had no effect on S1P-mediated differentiation of PAECs but abolished the S1P-induced inhibition of PASMC function. Co-cultured endothelial and smooth muscle cells differentiated into "neovascular-like" networks, which were significantly inhibited by S1P. The inhibition of co-culture differentiation in both PAECs and PASMCs was negated by H1152 pretreatment. However, when smooth muscle cells were added to S1P-initiated endothelial cell networks, additional S1P treatment did not inhibit the cellular networks generated by these cells. In conclusion, S1P-induced PAEC angiogenic responses are regulated by S1P(1) and/or S1P(3) receptors independent of Rho kinase activation, whereas S1P(2) receptor-mediated curtailment of PASMC function by S1P.

A kinematic model coupling stress fiber dynamics with JNK activation in response to matrix stretching

The role of the actin cytoskeleton in regulating mechanotransduction in response to external forces is complex and incompletely understood. Here, we develop a mathematical model coupling the dynamic disassembly and reassembly of actin stress fibers and associated focal adhesions to the activation of c-jun N-terminal kinase (JNK) in cells attached to deformable matrices. The model is based on the assumptions that stress fibers are pre-extended to a preferred level under static conditions and that perturbations from this preferred level destabilize the stress fibers. The subsequent reassembly of fibers upregulates the rate of JNK activation as a result of the formation of new integrin bonds within the associated focal adhesions. Numerical solutions of the model equations predict that different patterns of matrix stretch result in distinct temporal patterns in JNK activation that compare well with published experimental results. In the case of cyclic uniaxial stretching, stretch-induced JNK activation slowly subsides as stress fibers gradually reorient perpendicular to the stretch direction. In contrast, JNK activation is chronically elevated in response to cyclic equibiaxial stretch. A step change in either uniaxial or equibiaxial stretch results in a short, transient upregulation in JNK that quickly returns to the basal level as overly stretched stress fibers disassemble and are replaced by fibers assembled at the preferred level of stretch. In summary, the model describes a mechanism by which the dynamic properties of the actin cytoskeleton allow cells to adapt to applied forces through turnover and reorganization to modulate intracellular signaling.

Phellinus linteus suppresses growth, angiogenesis and invasive behaviour of breast cancer cells through the inhibition of AKT signalling

The antitumour activity of a medicinal mushroom Phellinus linteus (PL), through the stimulation of immune system or the induction of apoptosis, has been recently described. However, the molecular mechanisms responsible for the inhibition of invasive behaviour of cancer cells remain to be addressed. In the present study, we demonstrate that PL inhibits proliferation (anchorage-dependent growth) as well as colony formation (anchorage-independent growth) of highly invasive human breast cancer cells. The growth inhibition of MDA-MB-231 cells is mediated by the cell cycle arrest at S phase through the upregulation of p27^Kip1 expression. Phellinus linteus also suppressed invasive behaviour of MDA-MB-231 cells by the inhibition of cell adhesion, cell migration and cell invasion through the suppression of secretion of urokinase-plasminogen activator from breast cancer cells. In addition, PL markedly inhibited the early event in angiogenesis, capillary morphogenesis of the human aortic endothelial cells, through the downregulation of secretion of vascular endothelial growth factor from MDA-MB-231 cells. These effects are mediated by the inhibition of serine-threonine kinase AKT signalling, because PL suppressed phosphorylation of AKT at Thr³⁰⁸ and Ser⁴⁷³ in breast cancer cells. Taken together, our study suggests potential therapeutic effect of PL against invasive breast cancer.

Trans-fatty acids induce pro-inflammatory responses and endothelial cell dysfunction

Epidemiological data indicate that there is a strong association between intake of trans-18 : 2 fatty acids (TFA) and sudden cardiac death. There is little known about the mechanisms by which TFA exert harmful effects on the cardiovascular system. The present in vitro study is the first to demonstrate the effects of membrane-incorporated C18 : 2 TFA on human aortic endothelial cell (HAEC) function. Trans-18 : 2 fatty acids were incorporated to a greater extent (2-fold) in the phospholipid fraction of endothelial cells than that of cis-18 : 2; furthermore, these fatty acids were enriched to a similar extent in the TAG fraction. Flow cytometric analysis indicated that TFA treatment of HAEC significantly increased the expression of endothelial adhesion molecules, including intercellular adhesion molecule-1 (CD54) and vitronectin receptor (CD51/CD61). Incorporation of TFA into membranes increased HAEC adhesion to fibronectin- or vitronectin-coated plates by 1.5- to 2-fold, respectively. Neutrophil and monocyte adhesion to HAEC monolayers was nearly proportional to adhesion molecule expression. TFA treatment also induced the release of monocyte chemoattractant protein-1 by nearly 3-fold in non-stimulated HAEC. Furthermore, we examined the role of TFA on in vitro angiogenic assays. Chemotactic migration of TFA-treated HAEC toward sphingosine-1-phosphate (SPP) was significantly increased compared with controls. Conversely, capillary morphogenesis of TFA-treated HAEC was significantly inhibited in response to SPP, suggesting that TFA incorporation suppresses endothelial cell differentiation. In conclusion, these in vitro studies demonstrated that TFA play a role in the induction of pro-inflammatory responses and endothelial cell dysfunction.

Inhibition of breast tumor growth and angiogenesis by a medicinal herb: Ocimum gratissimum

Ocimum sp. is a traditionally used medicinal herb, which shows anti-oxidant, anti-carcinogenic, radio-protective and free radical scavenging properties. So far no detailed studies have been reported on its effects on human cancers. Thus, we analyzed its effects on human breast cancer utilizing in vitro and in vivo methodologies. Aqueous extracts were prepared from the mature leaves of Ocimum gratissimum (OG) cultivated devoid of pesticides. Tumor progression and angiogenesis related processes like chemotaxis, proliferation, apoptosis, 3D growth and morphogenesis, angiogenesis and tumor growth were studied in the presence or absence of the extract, and in some experiments a comparison was made with purified commercially available eugenol, apigenin and ursolic acid. Aqueous OG leaf extract inhibits proliferation, migration, anchorage independent growth, 3D growth and morphogenesis and induction of COX-2 protein in breast cancer cells. A comparative analysis with eugenol, apigenin and ursolic acid showed that the inhibitory effects on chemotaxis and 3D morphogenesis of breast cancer cells were specific to OG extract. In addition, OG extracts reduced tumor size and neoangiogenesis in a MCF10 DCIS.com xenograft model of human DCIS. This is the first detailed report showing that OG leaf extract may be of value as a breast cancer preventive and therapeutic agent and might be considered as additional additive in the arsenal of components aimed at combating breast cancer progression and metastasis.

The expression and production of vascular endothelial growth factor in oral mucosa equivalents

Angiogenesis is anticipated during wound healing. Vascular endothelial growth factor (VEGF) is a potent direct angiogenic factor that stimulates endothelial cell migration and proliferation in vitro and angiogenesis in vivo. Ex vivo produced oral mucosa equivalent (EVPOME) grafts have been reported to promote re-vascularization in the underlying tissue after grafting. The aim of this study was to evaluating the following: VEGF mRNA and its protein expression in EVPOME grafts, the protein levels in conditioned media produced by EVPOMEs, and the ability of VEGF to stimulate the growth of microvascular endothelial cells. VEGF mRNA expression and immunoreaction were found in basal and suprabasal layers. VEGF secreted by EVPOME was detected throughout the period of manufacture of the grafts, and became elevated for the first week at an air-liquid interface. Both EVPOME-conditioned media and a medium containing 10ng/mL recombinant human VEGF induced endothelial cell proliferation, while neutralization of VEGF by an antibody blocked cell growth. These results suggest that VEGF secreted by EVPOME grafts might assist initial vascularization after grafting, which is critical to subsequent graft survival.

Diverse signaling pathways regulate fibroblast differentiation and transformation through Rho kinase activation

This study examined the role of agonist-induced Rho kinase (ROCK) involvement in the morphological outcome of pulmonary-derived fibroblasts. Normal human lung fibroblasts (NHLF) spontaneously differentiate into network-like structures in a two-dimensional growth factor reduced Matrigel matrix-based assay. Sphingosine 1-phosphate (SPP), a bioactive phospholipid that regulates angiogenesis, inhibited fibroblast morphogenesis in a dose-dependent manner, virtually eliminating the presence of multi-cellular structures at 500 nM. Pretreatment with the Rho kinase-specific inhibitor, H1152, eradicated the high dose SPP-induced inhibition. Similarly, NHLFs transfected with Rho kinase siRNA prevented SPP-induced inhibition of the fibroblast morphogenesis. Alternatively, transforming growth factor-beta1 (TGF-beta1), a cytokine recognized as a key mediator of wound healing, terminally differentiates NHLF into myofibroblasts as evidenced by the expression of the smooth muscle cell isoform of alpha-actin (alpha-SMA). H1152 suppressed TGF-beta1-induced alpha-SMA expression in a dose-dependent manner. Similarly, treatment with Rho kinase siRNA reduced alpha-SMA expression by greater than 50%. SPP treatment had no effect on TGF-beta1-induced transformation into myofibroblasts, and TGF-beta1 treatment did not alter fibroblast morphogenesis. This study suggests a dual regulatory role for Rho kinase in cellular regulation of fibroblasts in which SPP-induced Rho kinase activation via a G-protein coupled receptor suppresses fibroblast morphogenesis while TGF-beta1-induced Rho kinase activation through a serine/threonine kinase receptor culminates in transformation into myofibroblasts.

Inhibition of sphingosine-1-phosphate- and vascular endothelial growth factor-induced endothelial cell chemotaxis by red grape skin polyphenols correlates with a decrease in early platelet-activating factor synthesis

Vascular endothelial growth factor (VEGF) and platelet-derived lipid sphingosine-1-phosphate (S1P) are two proinflammatory mediators which contribute to angiogenesis, in part through the synthesis of platelet-activating factor (PAF). The red grape skin polyphenolic extract (SGE) both prevents and inhibits angiogenesis in the Matrigel model, decreases the basal motility of endothelial and cancer cells, and reverses the chemotactic effect of S1P and VEGF on bovine aortic endothelial cells (BAECs) as well as the chemotactic effect of conditioned medium on human HT-1080 fibrosarcoma, human U-87 glioblastoma, and human DAOY medulloblastoma cells. Inhibition of VEGF- and S1P-mediated chemotaxis by SGE is associated with a down-regulation of ERK and p38/MAPK phosphorylation and a decreased in acute PAF synthesis. Notably, as do extracellular inhibitors of PAF receptor, SGE prevents S1P-induced PAF synthesis and the resulting activation of the S1P/endothelial differentiation gene-1 cascade. Given the key role of VEGF and S1P in inflammation, angiogenesis, and tumor invasion, SGE may therefore contribute to prevent (or to delay) the development of diseases associated with angiogenesis dysregulation, including cancer. The dual inhibition of S1P- and VEGF-mediated migration of endothelial cell and of serum-stimulated migration of U-87 cells suggests a usefulness of SGE against highly invasive human glioblastoma.

Ganoderma lucidum suppresses angiogenesis through the inhibition of secretion of VEGF and TGF-β1 from prostate cancer cells

Ganoderma lucidum (G. lucidum) is a popular medicinal mushroom that has been used as a home remedy for the general promotion of health and longevity in East Asia. The dried powder of G. lucidum, which was recommended as a cancer chemotherapy agent in traditional Chinese medicine, is currently popularly used worldwide in the form of dietary supplements. We have previously demonstrated that G. lucidum induces apoptosis, inhibits cell proliferation, and suppresses cell migration of highly invasive human prostate cancer cells PC-3. However, the molecular mechanism(s) responsible for the inhibitory effects of G. lucidum on the prostate cancer cells has not been fully elucidated. In the present study, we examined the effect of G. lucidum on angiogenesis related to prostate cancer. We found that G. lucidum inhibits the early event in angiogenesis, capillary morphogenesis of the human aortic endothelial cells. These effects are caused by the inhibition of constitutively active AP-1 in prostate cancer cells, resulting in the down-regulation of secretion of VEGF and TGF-beta1 from PC-3 cells. Thus, G. lucidum modulates the phosphorylation of Erk1/2 and Akt kinases in PC-3 cells, which in turn inhibits the activity of AP-1. In summary, our results suggest that G. lucidum inhibits prostate cancer-dependent angiogenesis by modulating MAPK and Akt signaling and could have potential therapeutic use for the treatment of prostate cancer.

Lysophospholipids in development: Miles apart and edging in

Sphingosine-1-phosphate (S1P) and lysophosphatidic acid (LPA) are endogenous bioactive lipids that participate in the regulation of mammalian cell proliferation, apoptosis, migration, and angiogenesis. These processes are each critical for successful embryogenesis, raising the possibility that lysophospholipid signaling may contribute to normal animal development. In fact, recent studies in developmental model systems have established that S1P and LPA are necessary for diverse developmental programs including those required for morphogenesis of vertebrate reproductive, cardiovascular and central and peripheral nervous systems (PNS), as well as the establishment of maternal-fetal circulation and the immune system. Genetic, morphological, and biochemical characterization of developmental model systems offer powerful approaches to elucidating the molecular mechanisms of lysophospholipid signaling and its contributions to animal development and postnatal physiology. In this review, the routes of S1P and LPA metabolism and our current understanding of lysophospholipid-mediated signal transduction in mammalian cells will be summarized. The evidence implicating lysophospholipid signaling in the development of specific vertebrate systems will then be reviewed, with an emphasis on signals mediated through G protein-coupled receptors of the Edg family. Lastly, recent insights derived from the study of simple metazoan models and implications regarding lysophospholipid signaling in organisms in which Edg receptors are not conserved will be explored.

Inflammatory triggers of lymphangiogenesis

Inflammation is the common denominator to the postnatal events that overlap with lymphatic vessel growth, or lymphangiogenesis. Undoubtedly, inflammation and accompanying fluid overload are cardinal factors in wound healing, lymphedema, the pathogenesis of some forms of lymphangiomatosis, and solid tumor lymphangiogenesis. The assertion that inflammation actually triggers lymphangiogenesis lies in the evidence set forth below that inflammation is the usual precursor to tissue repair and regeneration. Moreover, the panel of pro-inflammatory and anti-inflammatory molecules that orchestrates the inflammatory response abounds with cytokines and chemokines that foster survival, migration, and proliferation of lymphatic endothelial cells. Finally, both interstitial fluid overload and increased demand for removal of leukocytes can benefit from lymphangiogenesis, although the mechanisms controlling the exit of leukocytes from tissues via the lymphatics are practically unknown. The pertinent question actually is how and why inflammation presents with formation of new lymph vessels in liver fibrosis but not in rheumatoid arthritis. One possible explanation is that organ-specific histological and functional properties of the lymphatic endothelium gauge their response to death, survival, and proliferative factors. Alternatively, the decision to remain quiescent, proliferate or regress resides within the stroma microenvironment.

Pleomorphic mammalian tumor-derived bacteria self-organize as multicellular mammalian eukaryotic-like organisms: morphogenetic properties in vitro, possible origins, and possible roles in mammalian `tumor ecologies'

Highly pleomorphic bacteria have regularly been isolated from mammalian tumors and leukemic bloods. Here, it is shown that highly pleomorphic, cell-wall deficient bacteria derived from a mammalian tumor self-organize in vitro into mammalian tissue-like morphogenetic patterns consisting of multicellular tissue-like sheets and capillary-like networks. It is proposed that these pleomorphic mammalian tumor-derived (MTD) bacteria, during morphogenesis, express mammalian tissue morphogenesis-related genes that were acquired through eukaryote-to-prokaryote DNA transfer. Similar pleomorphic MTD bacteria might play important roles as symbiotic multicellular mammalian eukaryotic-like organisms in mammalian 'tumor ecologies' that include malignant and nonmalignant mammalian eukaryotic cells. From a mammalian tumor ecology perspective, eradication of tumors in some mammalian hosts may depend upon the elimination of pleomorphic MTD bacteria self-organized as symbiotic multicellular mammalian eukaryotic-like organisms. Further investigations of the extraordinary mammalian eukaryotic-like multicellularity of these bacteria may yield fundamental insights into the evolution of multicellularity and multicellular development and may challenge basic assumptions regarding cellular evolution.

Sphingosine 1-phosphate and cell migration: resistance to angiogenesis inhibitors

Naturally occurring angiogenesis inhibitors can inhibit different steps of the angiogenic process, such as endothelial cell migration. However, the mechanisms underlying this inhibition have not been elucidated. We demonstrate that migration of human umbilical vein endothelial cells induced by the potent endothelial cell chemoattractant sphingosine 1-phosphate is refractory to inhibition by well-characterized angiogenesis inhibitors such as endostatin and plasminogen-related protein-B. Our data support the contention that for effective blockage of tumor-induced angiogenesis, antagonists of both G protein-coupled receptor signaling and receptor tyrosine kinase signaling must be combined.

Sphingosine-1-phosphate markedly induces matrix metalloproteinase and integrin-dependent human endothelial cell invasion and lumen formation in three-dimensional collagen and fibrin matrices

Endothelial cell invasion is a key step in angiogenic blood vessel formation. Sphingosine-1-phosphate (S1P) has been previously reported to play a role in endothelial cell proliferation, survival, migration, and angiogenesis. Here, we examine the ability of S1P to regulate human endothelial cell invasion into three-dimensional collagen or fibrin matrices. We show that S1P potently stimulated human endothelial cell invasion, lumen formation, and branching morphogenesis in collagen, and fibrin matrices, (5- and 15-fold increases in invasion were observed, respectively). The S1P-induced invasion response was pertussis-toxin sensitive and completely dependent on integrins. Addition of integrin blocking reagents revealed that the alpha2beta1 integrin regulated invasion in collagen matrices, while a combination of alphavbeta3 and alpha5beta1 integrins regulated invasion in fibrin. Additionally, the S1P-induced invasion response was dependent on matrix metalloproteinases (MMPs). Tissue inhibitor of metalloproteinase-3 (TIMP-3) was the only physiologic inhibitor of metalloproteinases that completely inhibited the potent stimulation of invasion induced by S1P. In contrast, TIMP-1 had no blocking effect on invasion or morphogenesis, while TIMP-2 and TIMP-4 partially reduced invasion but completely blocked lumen formation events. Collectively, these data reveal a marked ability of S1P to induce metalloproteinase- and integrin-dependent human endothelial cell invasion and morphogenesis in both collagen and fibrin three-dimensional matrices, the two most physiologically relevant matrices for angiogenesis.

Matrix metalloproteinase regulation of sphingosine-1-phosphate-induced angiogenic properties of bone marrow stromal cells

OBJECTIVE

Bone marrow-derived stromal cells (MSC) are able to acquire histological and immunophenotypic characteristics consistent with endothelial cells (EC). In this study we examined the effect of sphingosine-1-phosphate (S1P), a platelet-derived bioactive lysophospholipid that is believed to specifically stimulate EC migration and tube formation, on the angiogenic properties of MSC.

METHODS

MSC were isolated from murine bone marrow and cultured in the presence of diverse angiogenic growth factors. Using a chemotaxis chamber and Matrigel tubulogenesis assay, we measured the extent of MSC migration and capillary-like structure formation. Western blots and zymography were used to assess the levels and activation states of soluble and membrane-bound matrix metalloproteinase (MMP).

RESULTS

We found that S1P strongly induced MSC migration and in vitro capillary-like structure formation. Ilomastat, a broad-spectrum MMP inhibitor, antagonized several angiogenic and S1P-mediated events in MSC. These included 1) the inhibition of S1P-induced tube formation, 2) the inhibition of concanavalin-A (Con-A)-mediated proMMP-2 activation, and 3) the inhibition of S1P- and Con-A-induced caspase-3 activity. Moreover, S1P induced membrane type-1 (MT1)-MMP mRNA and protein expression, but paradoxically antagonized its cell surface proteolytic processing. In addition, anti-angiogenic agents such as Ilomastat, Neovastat, and green tea polyphenol epigallocatechin-3-gallate antagonized the S1P-induced migration of MSC as well as that of transfected COS-7 cells overexpressing the recombinant receptor for S1P, EDG-1.

CONCLUSION

Collectively, our results indicate a crucial role for S1P/EDG-1-mediated angiogenic and survival events in the regulation of microvascular network remodeling by MSC, and may provide a new molecular link between hemostasis and angiogenesis processes.