Expression and control of vascular endothelial cells: proliferation and differentiation by fibroblast growth factors

Nanoparticular delivery system for a secretoneurin derivative induces angiogenesis in a hind limb ischemia model

Common therapeutic strategies for peripheral arterial disease often fail to re-establish sufficient blood flow within legs and feet of patients for avoiding critical limb ischemia, what is characterized by a substantial risk for amputation. The neuropeptide secretoneurin induces angiogenesis in models of limb and myocardial ischemia and might be a promising tool in the treatment of patients without the option of revascularization therapy for severe ischemia. Within this manuscript, the biologically active part of secretoneurin was identified, modified by induction of a cysteine residue to gain higher stability against enzymatic degradation and further packed into S-protected thiolated chitosan nanoparticles, which enable intra-muscular application of secretoneurin. Secretoneurin nanoparticles restored blood flow in a mouse hind limb ischemia model within one week, whereas control particles did not. In vitro testing also revealed the angiogenic, antiapoptotic and proliferative effects of the new secretoneurin derivate, as tested in primary human umbilical vein endothelial cells. With the work from this study we provide a new promising tool for treatment of peripheral arterial disease.

Inhibition of endogenous VEGF impedes revascularization and astroglial proliferation: roles for VEGF in brain repair

Vascular endothelial growth factor (VEGF) is upregulated following injury to the CNS. Our previous work has shown that exogenous application of VEGF promotes angiogenesis, blood-brain barrier permeability, and astroglial mitogenicity in the traumatized brain. To develop a model that could link endogenously secreted VEGF to brain tissue repair, a specific neutralizing antibody to VEGF was infused by osmotic minipump directly into the neocortex and striatum for up to 1 week. Tissues adjacent to the infusion/wound site were analyzed for specific vascular and astroglial protein markers and proliferation, necrosis/apoptosis (via TUNEL staining), VEGF, the VEGF receptors flt-1 and flk-1, and bFGF expression using immunohistochemistry and semi-quantitative RT-PCR. Neutralization of native VEGF caused significant decreases in angiogenic activity, astroglial proliferation, and nestin immunoexpression, while vascular and astroglial degeneration was substantially increased, resulting in much larger wound cavities when compared to controls. The hindrance of brain tissue repair occurred despite an increase in bFGF expression at the wound sites. VEGF appears to be an integral factor in CNS wound healing that is essential for vascular endothelial proliferation and survival and may also be necessary for astroglial proliferation and maintenance during the repair of brain injury.

Cyclic AMP and acidic fibroblast growth factor have opposing effects on tight and adherens junctions in microvascular endothelial cells in vitro

Endothelial adherens junctions (AJ) and tight junctions (TJ) are important determinants of vascular permeability and cell morphology. Here, we investigate their regulation, in primary human placental microvascular endothelial cell (HPMEC) cultures, by either aFGF plus heparin (ECGS) or elevated cAMP. The proliferation of HPMEC was weakly stimulated by ECGS, while cAMP was inhibitory. ECGS had little effect on transendothelial resistance (TER), but increased macromolecular permeability, whereas cAMP induced a twofold increase in TER and reduced macromolecular permeability. Ultrastructurally, ECGS-treated HPMEC exhibited an "activated" phenotype typified by proliferating cells, with poorly organized cell-cell junctions, whereas cAMP-treated cells appeared quiescent and markedly flattened with extended paracellular junctions, resembling endothelium in situ. The expression and localization of junctional molecules, F-actin, and junctional phosphotyrosine were examined by confocal microscopy and immunoblotting. Junctional molecules in ECGS-treated cells were less organized at lateral membranes than in control cells, whereas in cAMP-treated cells, they were highly localized at continuous contacts. These differences correlated with the intensity of junctional phosphotyrosine, being lowest with cAMP treatment. In the AJ of ECGS-treated and control cells, beta-catenin predominated but in cAMP-treated cells, gamma-catenin/plakoglobin was enriched. In addition, cAMP upregulated junctional expression of VE-cadherin and PECAM-1 and increased the levels of the TJ molecules occludin and ZO-1. The expression levels of junctional components, and their tyrosine phosphorylation, play an important role in dynamic regulation of endothelial cell-cell junctions.

Pharmacokinetics and pharmacodynamics of recombinant FGF-2 in a phase I trial in coronary artery disease

Fibroblast growth factor-2 (FGF-2) is a heparin-binding protein capable of inducing angiogenesis in multiple animal models of chronic ischemia. The pharmacokinetics and pharmacodynamics of a single dose of recombinant FGF-2 (rFGF-2) administered by intracoronary or intravenous infusion were evaluated in a Phase I trial in 66 patients with severe coronary artery disease. rFGF-2 displayed biphasic elimination with a mean studywide distribution t1/2 of 21 minutes and a mean apparent terminal elimination t1/2 of 7.6 hours. Systemic exposure to rFGF-2 was comparable following intracoronary or intravenous administration. Peak plasma concentration and area under the concentration-time curve increased proportionally with dose, indicating linear pharmacokinetics over the dose range examined (0.33 to 48.0 micrograms/kg). Greater systemic exposure was observed when heparin was administered closer to rFGF-2 infusion, consistent with slower clearance of heparin/rFGF-2 complexes. Infusion of rFGF-2 was associated with changes in acute hemodynamics. While a clear PK/PD dose-response relationship was not established, a trend toward hypotension and tachycardia with higher rFGF-2 doses was observed.

Basic fibroblast growth factor release by human coronary artery endothelial cells is enhanced by matrix proteins, 17beta-estradiol, and a PKC signaling pathway

Endothelial cell function is regulated by interactions among cells, the extracellular matrix (ECM), and soluble mediators. We investigated this interaction by examining the effect of 17beta-estradiol (E2) on release of basic fibroblast growth factor (FGF-2) by human coronary artery endothelial cells (HCAEC) cultured on ECM proteins. After estrogen-depleted HCAEC were treated with E2 for 2 h, the conditioned media and cell layers were evaluated by immunoblot or ELISA for FGF-2. Release of FGF-2 into conditioned media was enhanced 10-fold compared to that on plastic and a further 2.4-fold by E2. As FGF-2 release from cells into the media increases, there is a corresponding decrease in the cellular content of FGF-2. By ELISA, FGF-2 release increased 406, 179, and 262%, on type IV collagen, laminin, or fibronectin, respectively. HCAEC cultured on type I collagen did not show E2-enhanced FGF-2 release by ELISA or immunoblot analysis. No changes were noted in HCAEC release of lactate dehydrogenase, tested as a control protein for cellular integrity. The estrogen receptor antagonist ICI182,780 blocked E2-induced, but not basal, FGF-2 release. Increased FGF-2 release occurred via a cycloheximide-insensitive pathway. Neither brefeldin-A nor genistein inhibited E2 enhancement of FGF-2 release by HCAEC cultured on fibronectin. However, the protein kinase C inhibitor calphostin C inhibited the E2-augmented FGF-2 release. These data show that E2 enhances FGF-2 release by HCAEC cultured on basement membrane proteins in the absence of wounding. This action requires the estrogen receptor and PKC activity, but does not require new protein synthesis, endoplasmic reticulum-to-Golgi-mediated secretion, or protein tyrosine phosphorylation. E2-enhanced FGF-2 release could contribute to the cardioprotective effects of estrogen.

Basic fibroblast growth factor-mediated lymphangiogenesis of lymphatic endothelial cells isolated from dog thoracic ducts: effects of heparin

We have attempted to evaluate whether, similar to the angiogenesis of blood vessels, cultures of lymphatic endothelial cells (LEC) isolated from dog thoracic ducts have an ability to induce lymphangiogenesis in response to basic fibroblast growth factor (bFGF), then to examine the effects of heparin on the bFGF-mediated morphogenesis. The effects of bFGF and/or heparin on the proliferation and migration of the LEC were evaluated by changing the number of the subconfluent cells and by wound migration assay, respectively. The effects of the agents on invasion and tube formation of the LEC into a three-dimensional collagen gel and on collagen gel induced tube formation of the LEC were also investigated by a phase-contrast microscope and an electron microscope. The bFGF (10 ng/ml) caused a significant induction of proliferation and migration of the LEC, the induction of which was augmented dose-dependently by an additional treatment with heparin ranging from 1 to 100 microg/ml. The bFGF produced invasion and tube formation of the LEC into a three-dimensional collagen gel. The bFGF also facilitated to form capillary-like tubes of the LEC between two layers of collagen gels. Heparin (10 microg/ml) accelerated both processes of bFGF-mediated lymphangiogenesis of the LEC. These findings suggest that the cultured LEC isolated from dog thoracic ducts have an ability to form lymphatic capillary-like tubes in response to bFGF and that heparin accelerates dose-dependently the process of the bFGF-mediated neovascularization of lymph vessels.

Immunohistochemical localization of acidic fibroblast growth factor in normal human enterochromaffin cells and related gastrointestinal tumours

Acidic fibroblast growth factor (aFGF) is a member of the structurally related heparin-binding growth factor family. The best studied members of this family are aFGF and basic FGF (bFGF), which are potent mitogens and differentiation factors for mesoderm-derived cells, including fibroblasts. This study was designed to verify the immunohistochemical expression of aFGF in normal human endocrine cells of the gut and in related endocrine tumours. We examined normal gastrointestinal mucosa from seven different subjects and 41 gut endocrine tumours from different sites, including stomach, duodenum, and small and large intestine, using an aFGF polyclonal antibody with no cross-reactivity for bFGF. We localized aFGF in a fraction of serotonin-producing enterochromaffin (EC) cells of the normal gut, while it was absent in gastrin (G), CCK, secretion (S), somatostatin (D) and glicentin (L) cells. aFGF immunoreactivity was also expressed in serotonin producing EC cell tumours, but not in other functional types of gut endocrine neoplasms investigated, including gastric ECL cell, duodenal somatostatin and gastrin cell, and rectal L cell tumours. A positive correlation was found between expression of aFGF and the amount of tumour fibrous stroma, suggesting that aFGF may be involved in proliferation and activity of stromal fibroblasts.

Effect of basic fibroblast growth factor on normal tympanic membrane

PURPOSE

Basic fibroblast growth factor (bFGF) is mitogenic for the cell types that constitute the tympanic membrane and has been shown to potentiate tympanic membrane healing. The purpose of this study is to investigate the direct effect of bFGF application on normal tympanic membrane.

MATERIALS AND METHODS

bFGF was applied to the normal tympanic membrane of 10 guinea pigs via either the external auditory external canal or the middle ear. The drug (400 ng) was delivered on days 0, 1, and 2. The contralateral ear was used as a control. The effects were assessed on day 3.

RESULTS

The cumulative area and the average area of blood vessel in each session of TM was greater after bFGF application than placebo. The number of vessels remained unchanged. A proliferation of keratinocytes was observed.

CONCLUSION

These results suggest that bFGF induces a vasodilatation in the tympanic membrane thereby increasing blood supply. This might explain the acceleration of healing of TM perforations after bFGF application.

The pattern of cytokine messenger RNA expression in human aortic endothelial cells is different from that of human umbilical vein endothelial cells

Endothelial cells most readily available and most frequently used in investigations of alloimmunity and cytokine expression and function are derived from human umbilical veins. It is unclear whether cells derived from fetal venous tissue are relevant to phenomena related to the adult allograft, especially in areas such as cardiac allograft vasculopathy, a chronic rejection process directed against the coronary arteries. Human aortic endothelial cells (HAECs) were compared to human umbilical vein endothelial cells (HUVECs) for their constitutive expression of poly (A)+ RNA coding for a group of cytokines known to stimulate smooth muscle cell proliferation, including acidic fibroblast growth factor, basic fibroblast growth factor, transforming growth factor alpha, transforming growth factor beta, platelet-derived growth factor A-chain, platelet-derived growth factor B-chain and amphiregulin. Poly (A)+ RNA coding for basic fibroblast growth factor and transforming factor-beta was consistently expressed by all nine isolates of HAECs, but platelet-derived growth factor A- and B-chain were expressed in only six of the nine isolates. In most cases this was related to the presence of transforming growth factor alpha expression. In contrast, HUVECs consistently expressed basic fibroblast growth factor, transforming growth factor-beta, and both platelet-derived growth factor chains. Transforming growth factor alpha expression was never seen in the HUVEC isolates. No endothelial cell isolate expressed mRNA coding for acidic fibroblast growth factor or amphiregulin. There appear to be differences between cytokine gene expression patterns by endothelial cells from different vascular beds.

Epidermal growth factor stimulates vascular endothelial growth factor production by human malignant glioma cells: a model of glioblastoma multiforme pathophysiology

Hypervascularity, focal necrosis, persistent cerebral edema, and rapid cellular proliferation are key histopathologic features of glioblastoma multiforme (GBM), the most common and malignant of human brain tumors. By immunoperoxidase and immunofluorescence, we definitively have demonstrated the presence of vascular endothelial growth factor (VEGF) and epidermal growth factor receptor (EGFr) in five out of five human glioma cell lines (U-251MG, U-105MG, D-65MG, D-54MG, and CH-235MG) and in eight human GBM tumor surgical specimens. In vitro experiments with glioma cell lines revealed a consistent and reliable relation between EGFr activation and VEGF production; namely, EGF (1-20 ng/ml) stimulation of glioma cells resulted in a 25-125% increase in secretion of bioactive VEGF. Conditioned media (CM) prepared from EGF-stimulated glioma cell lines produced significant increases in cytosolic free intracellular concentrations of Ca2+ ([Ca2+]i) in human umbilical vein endothelial cells (HUVECs). Neither EGF alone or CM from glioma cultures prepared in the absence of EGF induced [Ca2+]i increases in HUVECs. Preincubation of glioma CM with A4.6.1, a monoclonal antibody to VEGF, completely abolished VEGF-mediated [Ca2+]i transients in HUVECs. Likewise, induction by glioma-derived CM of von Willebrand factor release from HUVECs was completely blocked by A4.6.1 pretreatment. These observations provide a key link in understanding the basic cellular pathophysiology of GBM tumor angiogenesis, increased vascular permeability, and cellular proliferation. Specifically, EGF activation of EGFr expressed on glioma cells leads to enhanced secretion of VEGF by glioma cells. VEGF released by glioma cells in situ most likely accounts for pathognomonic histopathologic and clinical features of GBM tumors in patients, including striking tumor angiogenesis, increased cerebral edema and hypercoagulability manifesting as focal tumor necrosis, deep vein thrombosis, or pulmonary embolism.

Expression and modulation of the vitronectin receptor on human dermal microvascular endothelial cells

Microvascular endothelial cells express a variety of cell-surface integrins in vivo and in vitro with varying affinities for matrix proteins. The vitronectin receptor (VnR), a complex of the alpha v and beta 3 integrin chains, is capable of binding to a variety of matrix proteins that are deposited in injured tissues, including vitronectin, fibrinogen, and thrombin. Staining of frozen sections of human skin with antibodies recognizing the VnR and examination by immunofluorescence microscopy demonstrates staining in a vascular pattern suggesting in vivo expression of the vitronectin receptor on endothelial cells. Examination of pure cultures of human dermal microvascular endothelial cells (HDMEC) by flow-cytometric analysis and enzyme-linked immunosorbent assay confirmed that HDMEC also express cell surface VnR complex in vitro. Stimulation of human dermal microvascular endothelial cells in vitro with agents that stimulate protein kinase C resulted in dose- and time-dependent increases in expression of alpha v and beta 3 integrin chains. Additionally, stimulation with basic fibroblast growth factor induced similar increases, but stimulation with transforming growth factor-beta or interleukin-1 alpha failed to increase VnR expression. Increases in cell-surface VnR expression also correlated with an increased ability of microvascular endothelial cells to bind to vitronectin, but not fibronectin-coated surfaces. Although increases in cell-surface expression of beta 3 paralleled increases in expression of cell-surface alpha v, regulation of mRNA expression was distinct for each chain. These data suggests that microvascular endothelial cells express the VnR complex in vivo, that the cell-surface expression of this integrin on dermal microvascular endothelial cells can be regulated, and that this regulation may be important in cell adherence, cell migration, and wound healing.

Induction of avascular yolk sac due to reduction of basic fibroblast growth factor by retinoic acid in mice

Vasculogenesis depends on autocrine secretion of basic fibroblast growth factor (bFGF) from capillary endothelial cells. Retinoic acid (RA) induced avascular yolk sac (AVY) of mouse embryos of dams given 60 mg/kg of RA orally on Day 8 of gestation and sacrificed 3 days later. We studied the localization and transcriptional expression of bFGF and FGF-receptor (flg), heparin-binding growth factor (HBGF) activity, localization of lysosomal enzymes and alpha 1-antitrypsin (AAT), and electron microscopy of the normal mouse visceral yolk sac (VYS) and AVY. bFGF, which is normally present in the endoderm of the VYS of 8-day-old embryos and in all components of the VYS by Day 11 of gestation, was reduced in the AVY. However, in the presence of bFGF in vitro capillary nets were restored in the AVY. The mRNA for bFGF was not detectable in either VYS or AVY, while flg mRNA was detected equally in both organs in Northern blotting. The characteristic distribution pattern of lysosomal enzymes, acid phosphatase, lysozyme, and cathepsin D, and AAT was altered in the AVY. The level of acid phosphatase and AAT was reduced to 10% in the AVY. Electron microscopy revealed a partial or total loss of lysosomal membranes where the contents of lysosomes fused with adjacent lysosomes and the external organelles. These results suggest that vitelline blood vessels are not developed by endogenous autocrine bFGF but by exogenous transcellular bFGF from absorptive endodermal cells. Retinoic acid does not affect the angiogenic capacity of the VYS mesenchyme but destroys lysosomes, which release hydrolytic enzymes, leading to degradation of AAT in the endodermal cells and then digestion of endocytosed bFGF.

Cytoskeleton in TFG-beta- and bFGF-modulated endothelial monolayer repair

Endothelial cell proliferation and migration in vitro is depressed by transforming growth factor beta (TFG-beta) and enhanced by basic fibroblast growth factor (bFGF) treatment. This study examines interactions between cytoskeletal changes and cell proliferation in regenerating endothelial monolayers treated with bFGF, TFG-beta, and both factors. As previously described by others, monolayer regeneration is enhanced by bFGF and reduced by TFG-beta. Endothelial cell morphology is altered by TFG-beta treatment. Cells lose their cobblestone appearance and assume a pleomorphic shape. Actin microfilament staining is modified in both intact and regenerating TFG-beta-treated monolayers as well. There is a loss of dense peripheral band staining and an enhancement in staining intensity of cytoplasmic stress fibers. No such alterations are seen in bFGF-treated cultures. Cell proliferation at the wound edge, as indicated by bromodeoxyuridine incorporation, is inhibited by TGF-beta. Although monolayer repair is modulated by growth factor treatment, centrosome reorientation and microtubule staining patterns are not altered by either factor. Thus these factors appear to have effects on a mechanism(s) other than centrosome reorientation which may be involved in repair of denuded endothelial monolayers.