Autocrine activities of basic fibroblast growth factor: regulation of endothelial cell movement, plasminogen activator synthesis, and DNA synthesis

Low-energy diode laser irradiation reduced plasminogen activator activity in human periodontal ligament cells

BACKGROUND AND OBJECTIVE

The plasminogen activator (PA)-plasmin proteolytic system is implicated in the degradation of the extracellular matrix in inflammation. Since human periodontal ligament (PDL) cells produced high PA activity in response to mechanical stress, excessive mechanical stress to PDL cells such as occlusal trauma may induce collagen breakdown through activation of the PA-plasmin system. As low-energy laser irradiation has anti-inflammatory effects, we examined the effects of low-energy laser irradiation on the PA-plasmin system in stretched PDL cells in vitro.

STUDY DESIGN/MATERIALS AND METHODS

Human PDL cells obtained from healthy premolars were mechanically stretched and Ga-Al-As low-energy laser was irradiated (830 nm, 3.95 to 7.90 J/cm2) to the stretched cells.

RESULTS

PDL cells showed a marked elevation in PA activity in response to stretching, which was significantly inhibited by a laser irradiation in a dose-dependent manner (55-86%, p < 0.001). This effect could involve transcriptional events of tissue type (t) PA gene.

CONCLUSION

These results suggests that laser irradiation may reduce collagen breakdown around the PDL associated with traumatic occlusion.

Oversulfated fucoidan inhibits the basic fibroblast growth factor-induced tube formation by human umbilical vein endothelial cells: its possible mechanism of action

We have previously demonstrated that chemically oversulfated fucoidan (OSF) but not native fucoidan (NF) effectively suppresses the tube structure formation by human umbilical vein endothelial cells (HUVEC) on the basement membrane preparation, Matrigel. In this study, using more defined systems where basic fibroblast growth factor (bFGF) induces the tube formation by HUVEC on collagen gel, we investigated the mechanism responsible for the inhibition of angiogenesis by OSF in vitro. Unlike NF and desulfated fucoidan (desF), OSF potently inhibited the bFGF-induced HUVEC migration and tube formation. ELISA for tissue-type plasminogen activator (t-PA) and plasminogen activator inhibitor-1 (PAI-1) in the culture media indicated that OSF increased the bFGF-induced release of PAI-1 antigen, but not of t-PA antigen. Analyses of the binding of bFGF to HUVEC surfaces and the following protein tyrosine phosphorylation revealed that OSF could promote the cell binding and autophosphorylation of 140 and 160 kDa receptors. In heparitinase-treated HUVEC, contrarily, the bFGF binding and PAI-1 release were decreased by OSF. These results suggest that OSF is a highly sulfated unique polysaccharide that can promote the binding of bFGF to the heparan sulfate molecules required for binding to the high affinity receptors with tyrosine kinase activity. The resultant increase in PAI-1 release may play a key role for the prevention of cell migration accompanied by matrix proteolysis.

Expression of the 37-kDa laminin binding protein in murine lung tumor cell correlates with tumor angiogenesis

Expression of the 37-kDa laminin binding protein (37LBP), a precursor protein of the 67-kDa laminin receptor, correlates well with the biological aggressiveness of cancer cells. Previously, we have established murine lung cancer cell lines T11 and T15, in which 37LBP expression was remarkably diminished, and reported that the mean survival time of the T11 and the T15-recipients was significantly prolonged compared with that of the control cell lines (P29 and T42). In the present study, immunohistochemical findings of the tumors demonstrated that the microvessel density in the T11 (28. 1+/-7.2/mm(2)) and in the T15 tumor (29.7+/-6.5/mm(2)) were significantly lower than that observed in P29 (46.3+/-8.7/mm(2)) or in T42 (50.5+/-4.4/mm(2)). Expression of vascular endothelial growth factor (VEGF) was repressed in T11 and T15 compared with its expression in P29 and T42. It was also shown that conditioned media of T11 and T15 cells exhibited significantly reduced proliferation and migration of the capillary endothelial cells. These results suggest that decreased expression of 37LBP in antisense-RNA transfectant may relate to its low tumorigenicity, and that this effect may be partly caused by the diminished tumor angiogenesis of murine lung cancer.

Remodeling of coronary artery lesions due to Kawasaki disease: comparison of arteriographic and immunohistochemical findings

Since the original report of Kawasaki disease in 1967 more than 150,000 cases have been reported in Japan. Although there have been no nationwide epidemics in Japan since 1987, more than 6,000 newly diagnosed cases are reported every year, and the number has been increasing year by year despite the decreasing birth rate. The etiology of the disease is still unknown. High dose intravenous gammaglobulin is currently used during the acute phase in 84% of the patients in Japan with a concomitant decrease in coronary arterial sequelae. However, 7-13% of the patients still have persistent coronary artery aneurysms after the acute stage. The aneurysms are seen mostly in the proximal coronary arteries, and are often associated with aneurysms in the distal coronary artery segments (Figure 1A, 2A). Most of the patients show a decrease in the size of aneurysms soon after the acute phase (Figure 1B). However, the aneurysms may progress to obstructive lesions even after initial regression (Figures 1C, D, 2B). Such obstructive lesions may cause sudden death or myocardial infarction. Long term follow-up of coronary artery lesions has revealed several characteristic features, including progressive localized stenosis (Figure 1D), extensive recanalizations (Figure 2D) and development of collateral arteries. Progressive increases in aneurysm size and the appearance of new aneurysms in the late phase have also been reported. The basic mechanisms of the coronary arterial remodeling in Kawasaki disease have not yet been elucidated. Only recently has immunohistochemical staining in formalin-fixed specimens become feasible. This is a major technical breakthrough since it is almost impossible to obtain fresh frozen specimens of coronary artery lesions of Kawasaki discase. In this paper, we compare immunohistochemical findings in coronary artery lesions with the corresponding coronary angiographic findings, and attempt to make inferences as to the mechanism of remodeling both in early and late phases of the disease based on the expression of vascular growth factors.

Expression of vascular endothelial growth factors and their receptors during osteoblast differentiation

Endochondral bone formation is regulated by systemically and locally acting growth factors. A role for vascular endothelial growth factor (VEGF) in this process has recently been proposed, because inactivation of VEGF inhibits endochondral bone formation via inhibition of angiogenesis. Despite the known effect of VEGF as specific endothelial growth factor, its effects on osteoblast differentiation have not been studied. We, therefore, examined the expression of VEGF-A, -B, -C, and -D and their receptors in a model of osteoblast differentiation using the mouse preosteoblast-like cell line KS483. Early in differentiation, KS483 cells express low levels VEGF-A, -B, and -D messenger RNA, whereas during mineralization, KS483 cells express high levels. In addition, expression of the VEGF receptors, VEGFR1, VEGFR2, and VEGF165R/neuropilin, coincided with expression of their ligands, being maximally expressed during mineralization. VEGF-A production during osteoblast differentiation was stimulated by insulin-like growth factor I that enhances osteoblast differentiation and was inhibited by PTH-related peptide that inhibits osteoblast differentiation. Furthermore, continuous treatment of KS483 cells with recombinant human VEGF-A stimulated nodule formation. Although treatment of KS483 cells with soluble FLT1, an agent that blocks binding of VEGF-A and -B to VEGFR1, did not inhibit nodule formation, this observation does not exclude involvement of VEGFR2 in the regulation of osteoblast differentiation. As it is known that VEGF-A, -C, and -D can act through activation of VEGFR2, other isoforms might compensate for VEGF-A loss. The expression pattern of VEGFs and their receptors shown here suggests that VEGFs play an important role in the regulation of bone remodeling by attracting endothelial cells and osteoclasts and by stimulating osteoblast differentiation.

Roles of two VEGF receptors, Flt-1 and KDR, in the signal transduction of VEGF effects in human vascular endothelial cells

Vascular endothelial growth factor (VEGF) is a principal regulator of vasculogenesis and angiogenesis. VEGF expresses its effects by binding to two VEGF receptors, Flt-1 and KDR. However, properties of Flt-1 and KDR in the signal transduction of VEGF-mediated effects in endothelial cells (ECs) were not entirely clarified. We investigated this issue by using two newly developed blocking monoclonal antibodies (mAbs) against Flt-1 and KDR. VEGF elicits DNA synthesis and cell migration of human umbilical vein endothelial cells (HUVECs). The pattern of inhibition of these effects by two mAbs indicates that DNA synthesis is preferentially mediated by KDR. In contrast, the regulation of cell migration by VEGF appears to be more complicated. Flt-1 regulates cell migration through modulating actin reorganization, which is essential for cell motility. A distinct signal is generated by KDR, which influences cell migration by regulating cell adhesion via the assembly of vinculin in focal adhesion plaque and tyrosine-phosphorylation of focal adhesion kinase (FAK) and paxillin.

Role of fibroblast growth factor-2 in human brain: a focus on development

Trophic factors have gained a great degree of attention as regulators of neural cells proliferation and differentiation as well as of brain maturation. Very little is known, however, about their effects on human immature nervous system. In this paper, data on expression of fibroblast-growth factor-2 and its receptors are reviewed and discussed in the light of its possible role in human brain development.

E1A stimulates FGF-2 release promoting differentiation of primary endothelial cells

Basic Fibroblast Growth Factor (FGF-2) is a growth and survival factor and represents one of the most potent differentiation agents of vascular system. In the present study we describe that adenoviral oncoprotein E1A regulates FGF-2 production and determines the acquisition of a pro-angiogenic phenotype in primary bovine aortic endothelial cells (BAEC). Following their transfection, wild type E1A proteins 12S and 13S (wtE1A) stimulated BAEC to differentiate on reconstituted basement membrane matrix (Matrigel). This outcome was paralleled by invasion and migration enhancement in wtE1A-transfected cells. This stimulating effect was absent with the E1A mutant dl646N. Accordingly, zymography and RT - PCR analyses showed that matrix metalloproteinase-9 protein- and mRNA-levels increased following wtE1A transfection. Interestingly, wtE1A-transfected BAEC showed FGF-2 mRNA- and protein-levels higher than controls. Further, FGF-2 neutralization reduced the amount of MMP-9 released in the supernatant of E1A-transfected cells and strongly inhibited BAEC differentiation, thus suggesting that wtE1A activates BAEC by a mechanism, at least partially, dependent on a FGF-2 autocrine/paracrine loop.

Novel method for the quantitative assessment of cell migration: a study on the motility of rabbit anterior cruciate (ACL) and medial collateral ligament (MCL) cells

A novel method of quantitating cell migration has been proposed for the potential utilization of tissue engineered scaffolds. Applying Alt's conservation law to describe the motion of first passage ACL and MCL cells, we have developed a quantitative method to assess innate differences in the motility of cells from these two ligamentous tissues. In this study, first passage ACL and MCL cells were cultured from four mature New Zealand white rabbits. One side of the cell monolayer was scraped completely away to create a wound model. The cell moved into the cell-free area, and cell density profiles were analyzed at 6 h and 12 h. Values of the random motility coefficient (mu) were then estimated by curve fitting the 6 h and 12 h data to a mathematical model, derived from the conservation law of cell flux. During 6 h of incubation in medium supplemented with 1% FBS, MCL cells (mu(MCL) = 4.63 +/- 0.65 X 10(-6) mm(2)/sec) were significantly (p < 0.05) more mobile than ACL cells (mu(ACL) = 2.51 +/- 0.31 X 10(-6) mm(2)/sec). At 12 h, the MCL cells also appeared to move faster (mu(ACL) = 4.39 +/- 0.63 X 10(-6) mm(2)/sec, mu(MCL) = 6.59 +/- 1.47 X 10(-6) mm(2)/sec), but the difference was not statistically significant (p = 0.18). Exposure of the cells to growth factors PDGF-BB or bFGF for 6 h had no significant effect on the migration of the ACL and MCL cells. However, exposure of the ACL cells (p < 0.05) and the MCL cells (p = 0.19) to 1 ng/mL of PDGFBB for 12 h enhanced their migration. Incubation with a high concentration (100 ng/mL) of PDGF-BB or bFGF at concentrations tested (1 or 100 ng/mL) for 12 h, produced little or no migratory stimulation on these ligament cells. Our findings support the previous qualitative observations made by numerous investigators. The novel methodology developed in this study may provide a basis for tissue engineering, and the results may be applied to tissue reconstruction techniques of the knee ligaments.

PAI-1 gene expression is regionally induced in wounded epithelial cell monolayers and required for injury repair

Induced expression of plasminogen activator inhibitor type-1 (PAI-1), a major negative regulator of pericellular plasmin generation, accompanies wound repair in vitro and in vivo. Since transcriptional control of the PAI-1 gene is superimposed on a growth state-dependent program of cell activation (Kutz et al., 1997, J Cell Physiol 170:8-18), it was important to define potentially functional relationships between PAI-1 synthesis and subpopulations of cells that emerge during the process of injury repair in T2 renal epithelial cells. Specific cohorts of migratory and proliferating cells induced in response to monolayer trauma were spatially as well as temporally distinct. Migrating cells did not divide in the initial 12 to 20 h postinjury. After 24 h, S-phase cells were generally restricted to a region 1 to 2 mm from, and parallel to, the wound edge. Proliferation of wound bed cells occurred subsequent to wound closure, whereas the distal contact-inhibited monolayer remained generally quiescent. Hydroxyurea blockade indicated, however, that proliferation (most likely of cells immediately behind the motile "tongue") was necessary for maintenance of cell-to-cell cohesiveness in the advancing front, although the ability to migrate was independent of proliferation. PAI-1 mRNA expression was rapidly up-regulated in response to wounding with inductive kinetics approximating that of serum-stimulated cultures. Differential harvesting of T2 cell subpopulations, based on proximity to the injury site, prior to Northern assessments of PAI-1 mRNA abundance indicated that PAI-1 transcripts were restricted to cells immediately bordering the wound or actively migrating and not expressed by cells in the distal contact-inhibited monolayer regions. Such cell location-specific distribution of PAI-1-producing cells was confirmed by immunocytochemistry. PAI-1 synthesis in cells that locomoted into the wound field continued until injury closure. Down-regulation of PAI-1 synthesis and matrix deposition in renal epithelial cells, stably transfected with a PAI-1 antisense expression vector, significantly impaired wound closure. Transfection of the wound repair-deficient R/A epithelial line with a sense PAI-1 expression construct restored both approximately normal levels of PAI-1 synthesis and repair ability. These data indicate that PAI-1 induction is an early event in creation of the wound-activated phenotype and appears to participate in the regulation of renal epithelial cell motility during in vitro injury resolution.

Cell density-dependent regulation of proteoglycan synthesis by transforming growth factor-beta(1) in cultured bovine aortic endothelial cells

The regulation of vascular endothelial cell behavior during angiogenesis and in disease by transforming growth factor-beta(1) (TGF-beta(1)) is complex, but it clearly involves growth factor-induced changes in extracellular matrix synthesis. Proteoglycans (PGs) synthesized by endothelial cells contribute to the formation of the vascular extracellular matrix and also influence cellular proliferation and migration. Since the effects of TGF-beta(1) on vascular smooth muscle cell growth are dependent on cell density, it is possible that TGF-beta(1) also directs different patterns of PG synthesis in endothelial cells at different cell densities. In the present study, dense and sparse cultures of bovine aortic endothelial cells were metabolically labeled with [(3)H]glucosamine, [(35)S]sulfate, or (35)S-labeled amino acids in the presence of TGF-beta(1). The labeled PGs were characterized by DEAE-Sephacel ion exchange chromatography and Sepharose CL-4B molecular sieve chromatography. The glycosaminoglycan M(r) and composition were analyzed by Sepharose CL-6B chromatography, and the core protein M(r) was analyzed by SDS-polyacrylamide gel electrophoresis, before and after digestion with papain, heparitinase, or chondroitin ABC lyase. These experiments indicate that the effect of TGF-beta(1) on vascular endothelial cell PG synthesis is dependent on cell density. Specifically, TGF-beta(1) induced an accumulation of small chondroitin/dermatan sulfate PGs (CS/DSPGs) with core proteins of approximately 50 kDa in the medium of both dense and sparse cultures, but a cell layer-associated heparan sulfate PG with a core protein size of approximately 400 kDa accumulated only in dense cultures. Moreover, only in the dense cell cultures did TGF-beta(1) cause CS/DSPG hydrodynamic size to increase, which was due to the synthesis of CS/DSPGs with longer glycosaminoglycan chains. The heparan sulfate PG and CS/DSPG core proteins were identified as perlecan and biglycan, respectively, by Western blot analysis. The present data suggest that TGF-beta(1) promotes the synthesis of both perlecan and biglycan when endothelial cell density is high, whereas only biglycan synthesis is stimulated when the cell density is low. Furthermore, glycosaminoglycan chains are elongated only in biglycan synthesized by the cells at a high cell density.

Indispensable role of the transcription factor PEBP2/CBF in angiogenic activity of a murine endothelial cell MSS31

Mice lacking the AML1/PEBP2alphaB/CBFa2 gene or PEBP2beta/CBFb gene exhibit a defect in definitive hematopoiesis and die in utero because of hemorrhage in the central nervous system. Hematopoiesis in the embryo is considered to be tightly associated with vascular development. Here we examined whether PEBP2/CBF plays any role in angiogenesis besides that in definitive hematopoiesis. We found that AML1/PEBP2alphaB/CBFa2, PEBP2alphaA/CBFa1, and PEBP2beta/CBFb were expressed in a murine endothelial cell line MSS31. The expression of these molecules as well as the DNA binding activity of PEBP2/CBF were augmented by angiogenic growth factors such as bFGF and VEGF. Moreover, the expression of PEBP2 alpha/CBFa protein in endothelial cells was confirmed at the site of angiogenesis in vivo. To further clarify the role of PEBP2/CBF in angiogenesis, we established permanent transfectants of PEBP2 beta-MYH11 gene, one that interacts with the runt domain of the alpha subunit and deregulates PEBP2/CBF in a dominant interfering manner. Proliferation, migration, and tube formation of the PEBP2 beta-MYH11 transfectants were significantly reduced in comparison with those activities of the mock transfectants. These results suggest that transcription factor PEBP2/CBF plays an important role in angiogenesis.

Human rhabdomyosarcoma cells retain insulin-regulated glucose transport activity through glucose transporter 1

We evaluated the expression of glucose transporter (glut) isoforms and its function in RD cells, human rhabdomyosarcoma, which retain the potential to differentiate into muscle. Gluts 1, 3, and 4 were expressed in RD cells, as detected by reverse-transcription polymerase chain reaction and immunocytochemistry. Supraphysiological concentration (1 microM) of insulin treatment increased 2-deoxy glucose transport by up to 1.68-fold together with concomitant tyrosine phosphorylation of the insulin receptor beta subunit and of insulin receptor substrate 1. Suppression of glut 1 mRNA by 38% by antisense oligonucleotide transfection led to a reduction of basal and insulin-stimulated 2-deoxy glucose transport by 38 and 55%, respectively. Suppression of gluts 3 and 4 by antisense oligonucleotide transfection did not affect both basal and insulin-stimulated 2-deoxy glucose transport. Thus, glut 1 accounts for the major part of basal and insulin-stimulated glucose transport in RD cells. Next, we transfected expression vectors carrying human gluts 1 and 4 cDNAs into RD cells to add further support for the role of glut 1 in glucose transport. Overexpression of glut 1 stimulated basal and insulin-stimulated 2-deoxy glucose transport by 1.66- and 1.43-fold, respectively. Glut 4 overexpression did not affect basal and insulin-stimulated 2-deoxy glucose transport. Western blot analysis using glut 1 antibody showed that glut 1 was redistributed from intracellular membrane to plasma membrane. These observations support the notion that RD cells, with the potential to differentiate into muscle, retain insulin responsiveness. As human muscle cell lines are not available at this point, RD cells can serve as a useful alternative to human muscle for studies related to insulin signal transduction and glucose transport.

Both FGF1 and bcl-x synthesis are necessary for the reduction of apoptosis in retinal pigmented epithelial cells by FGF2: role of the extracellular signal-regulated kinase 2

Retinal pigmented epithelial (RPE) cells are of central importance in the maintenance of neural retinal function. Changes in the RPE cells associated with repair activities have been described as metaplasia, while RPE cell apoptosis is responsible for the development of a variety of retinal degenerations. We investigated the regulation of the anti-apoptotic properties of the fibroblast growth factors (FGF) 2 in serum-free cultures of RPE cells. In the absence of serum, confluent stationary RPE cells died by apoptosis via a caspase 3-dependent pathway. The addition of FGF2 greatly reduced apoptosis over a 7-day culture period. We demonstrated the involvement of an autocrine loop involving endogenous FGF1 in the mechanisms that govern FGF2-induced resistance to apoptosis by showing: (1) higher levels of apoptosis in cells treated with antisense FGF1 oligonucleotide or after neutralization of excreted FGF1; (2) the long-term activation of FGFR1 and of ERK2, (3) the inhibition of FGFR1 and ERK2 activation and an increase in apoptosis if excreted FGF1 was neutralized. FGF2 also increased the de novo synthesis and the production of Bcl-xl before the onset of apoptosis. Both inhibition of ERK2 activation, which decreased Bcl-xl synthesis, and downregulation of Bcl-x by antisense oligonucleotide treatment inhibited the survival-promoting activity of FGF2. Thus, FGF2-induced cell survival is a progressive adaptive phenomenon involving ERK2 activation by excreted FGF1 and ERK2-dependent Bcl-x production.

Basic fibroblast growth factor synthesis by human peritoneal mesothelial cells: induction by interleukin-1

Peritoneal mesothelial cells are uniquely located to regulate cellular events in the peritoneal cavity and are an important source for various cytokines and growth factors. This study was conducted to analyze the capacity of human peritoneal mesothelial cells (HPMCs) to synthesize and release basic fibroblast growth factor (bFGF) and to characterize its regulation by inflammatory cytokines. HPMCs constitutively synthesized and released considerable amounts of bFGF as detected by a specific immunoassay. Almost 80% of bFGF (1547 +/- 173 pg/10(5) cells) was localized intracellularly. Approximately 20% of the bFGF (357 +/- 27 pg/10(5) cells) was associated with extracellular matrix components on the HPMC surface. Small amounts of bFGF (<1%) were detectable in tissue culture supernatants (8.4 +/- 1.4 pg/10(5) cells). Treatment of HPMCs with interleukin-1beta (IL-1beta; 1 ng/ml) resulted in a significant increase in bFGF production. The intracellular bFGF content showed a rapid but only transient increase, which was significant above background levels after 24 hours (41% increase; P < 0.05). This increase in intracellular bFGF concentration was associated with an induction of the release of bFGF. Within 96 hours, the release of bFGF to the cell surface and into the supernatant increased by 58% (564 +/- 52.4 pg/10(5) cells; P < 0.01) and by 214% (26.4 +/- 3.2 pg/10(5) cells; P < 0.001), respectively. Neither tumor necrosis factor-alpha nor interferon-gamma affected bFGF synthesis by HPMCs. Stimulation of HPMCs with IL-1beta increased steady-state levels of bFGF-specific mRNA. Immunohistochemical analyses of peritoneal tissue revealed constitutive expression of bFGF by HPMCs. This in situ expression proved to be most pronounced in areas of serosal inflammation in activated HPMCs. Our study demonstrates that HPMCs synthesize and release significant amounts of bFGF and that the expression of this growth factor is significantly up-regulated by the proinflammatory cytokine IL-1beta. The data support the view that HPMCs are key regulators of abdominal disease processes such as peritonitis, peritoneal fibrosis, or peritoneal tumor metastasis.

Alterations of blood vessel development by endothelial cells overexpressing fibroblast growth factor-2

A close relationship exists between angiogenesis and the formation of vascular lesions. The development of the vascular system in the chick embryo chorioallantoic membrane (CAM) may thus represent a model to study the effects of the deregulation of endothelial cell behaviour. Alterations of the developing vascular tree of the CAM were observed after exposure to murine aortic endothelial (MAE) cells overexpressing human fibroblast growth factor-2 (FGF2) cDNA (pZipFGF2 MAE cells), or to their conditioned medium (CM). pZipFGF2 MAE cells injected into the allantoic sac or applied on to the CAM of day 8-9 chick embryos induce neovascularization and the appearance of haemangioma-like lesions. This activity was not prevented by anti-FGF2 antibodies. The CM from pZipFGF2 MAE cells was also active when adsorbed into a gelatin sponge and applied on to the CAM, both in the absence and in the presence of anti-FGF2 antibodies. No effects on vessel development were exerted by parental MAE cells, FGF2-transfected NIH 3T3 fibroblasts, or their conditioned media. In vitro, pZipFGF2 MAE cell CM caused parental MAE cells to invade fibrin gels and to undergo morphogenesis on Matrigel. This activity was not mimicked by recombinant FGF2 nor affected by anti-FGF2 antibodies, and depended on a M (r) approximately 45 000 heat-labile heparin-binding factor. Size exclusion chromatography of pZipFGF2 MAE cell CM demonstrated that the in vitro activity co-purified with an in vivo angiogenic capacity. Thus, FGF2 overexpression in mouse endothelial cells induces the production of an angiogenic activity distinct from FGF2, which may contribute to the genesis of angioproliferative lesions.

The tumor-suppressing activity of angiostatin protein resides within kringles 1 to 3

Angiostatin protein, which comprises the first four kringle domains of plasminogen, is an endogenous inhibitor of angiogenesis that inhibits the growth of experimental primary and metastatic tumors. Truncation of Angiostatin K1-4 to K1-3 retained the activity of Angiostatin. We recombinantly expressed full-length human Angiostatin protein corresponding to the first four kringle domains of human plasminogen and a truncated form of the Angiostatin protein, kringles 1-3. Purified recombinant Angiostatin K1-3 and K1-4 proteins inhibited the formation of experimental B16-BL6 lung metastases by greater than 80% when administered at 30 nmol/kg/day. We demonstrate for the first time that Angiostatin protein, consisting of the first three kringle domains of human plasminogen, has in vivo biological activity in this assay indistinguishable from that of the full-length Angiostatin K1-4 protein and that the fourth kringle of plasminogen, when linked in sequence to K1-3, plays no direct role in the antitumor activity of Angiostatin.

Autocrine FGF-2 is responsible for the cell density-dependent susceptibility to apoptosis of HUVEC : A role of a calpain inhibitor-sensitive mechanism

To elucidate the factors affecting endothelial susceptibility to apoptosis, we studied the effects of cell density on endothelial cell apoptosis induced by deprivation of serum and fibroblast growth factor-2 (FGF-2/basic FGF). On deprivation, more cells became apoptotic in a dense culture (5 x 10(2) cells/mm(2)) than in a sparse culture (1 x 10(2) cells/mm(2)) of human umbilical vein endothelial cells. FGF-2, hepatocyte growth factor, and vascular endothelial cell growth factor, but not insulin-like growth factor-I, decreased apoptosis in the dense culture to a level similar in the sparse culture. An anti-FGF-2 antibody significantly increased the apoptosis in the sparse culture, suggesting that the sparse culture was resistant to apoptosis because of the greater autocrine production of FGF-2. Western blot analysis and metabolic labeling revealed that the sparse culture has, in fact, more FGF-2 than the dense culture. The steady state level of mRNA for FGF-2 was not significantly different between the dense and sparse cultures. Among a panel of inhibitors for 2 major cytoplasmic proteolytic enzymes, calpain inhibitors increased FGF-2 in the dense culture, but proteasome inhibitors did not. Our findings demonstrate that cell density affects endothelial survival by regulating autocrine FGF-2 production through a calpain inhibitor-sensitive mechanism.

Tensional forces in fibrillar extracellular matrices control directional capillary sprouting

During angiogenesis, anastomosing capillary sprouts align to form complex three-dimensional networks of new blood vessels. Using an endothelial cell spheroid model that was developed to study endothelial cell differentiation processes, we have devised a novel collagen gel-based three-dimensional in vitro angiogenesis assay. In this assay, cell number-defined, gel-embedded endothelial cell spheroids act as a cellular delivery device, which serves as a focal starting point for the sprouting of lumenized capillary-like structures that can be induced to form complex anastomosing networks. Formation of capillary anastomoses is associated with tensional remodeling of the collagen matrix and directional sprouting of outgrowing capillaries towards each other. To analyze whether directional sprouting is dependent on cytokine gradients or on endothelial cell-derived tractional forces transduced through the extracellular matrix, we designed a matrix tension generator that enables the application of defined tensional forces on the extracellular matrix. Using this matrix tension generator, causal evidence is presented that tensional forces on a fibrillar extracellular matrix such as type I collagen, but not fibrin, are sufficient to guide directional outgrowth of endothelial cells. RGD peptides but not control RAD peptides disrupted the integrity of sprouting capillary-like structures and induced detachment of outgrowing endothelial cells cultured on top of collagen gels, but did not inhibit primary outgrowth of endothelial cells. The data establish the endothelial cell spheroid-based three-dimensional angiogenesis technique as a standardized, highly reproducible quantitative assay for in vitro angiogenesis studies and demonstrate that integrin-dependent matrix tensional forces control directional capillary sprouting and network formation.

Dissociation of mesangial cell migration and proliferation in experimental glomerulonephritis

BACKGROUND

Recently, we documented that following in vivo mesangial cell (MC) ablation in the Thy1 model, reconstitution of the mesangium occurs by a coordinated proliferation and migration of Thy1 (OX-7)-positive cells originating from the hilus and extraglomerular mesangium. We investigated the role of basic fibroblast growth factor (bFGF) in the mediation of these events.

METHODS

Rats were injected with antithymocyte serum and 48 hours later were pulsed with 3H-thymidine to label proliferating cells. Ninety minutes later, a baseline renal biopsy was obtained, and rats were injected with neutralizing anti-bFGF antibodies or control IgG. Sacrificial biopsies were obtained at 96 hours of disease. Using computer image analysis, biopsies from both time points were quantitated for the number of radiolabeled MC (proliferation) and their mean distance from the hilus (migration). The effect of bFGF on the migration of MCs in culture was examined using a chemotactic assay.

RESULTS

At sacrifice, autoradiographs of rats receiving anti-bFGF had significantly fewer radiolabeled MCs as compared with rats receiving control IgG (8.7+/-1.9 vs. 14.7+/-3.5, P = 0.0001), yielding an overall 40% reduction in proliferation. There was no difference, however, in the final distance of radiolabeled MCs from the glomerular hilus in the two groups, indicating that the administration of anti-bFGF did not effect MC migration in this model. In an in vitro chemotactic assay, MCs migrated in response to platelet-derived growth factor (PDGF) BB (20 ng/ml), but did not migrate in response to bFGF at a wide range of concentrations (0.5 to 50 ng/ml).

CONCLUSIONS

These studies demonstrate that bFGF is an important mediator of MC proliferation but that it does not significantly influence MC migration. This is the first demonstration showing that the mediators effecting proliferation can be dissociated from those mediating migration in renal injury.

D-Glucose and insulin stimulate migration and tubular formation of human endothelial cells in vitro

Effects of high D-glucose and insulin on the endothelial cell migration and tubular formation were investigated with the use of ECV304 cells, a clonal human umbilical cord endothelial cell line. Exposure of the cells to high D-glucose resulted in a marked increase in the migration, which was blocked by inhibitors of protein kinase C such as H7 (10 microM) and GF109203X (200 nM). Furthermore, a protein kinase C agonist, phorbol 12-myristate 13-acetate, had an effect similar to that of glucose on ECV304 cells. Glucose stimulation of the migration was additively enhanced by 100 nM insulin, and the insulin effect was found to be unaffected by either PD-98059 or wortmannin, a mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase inhibitor and a phosphatidylinositol 3-kinase inhibitor, respectively. Neither did H7 inhibit insulin stimulation of the migration. In contrast, a combination of high D-glucose and insulin, rather than either one alone, promoted tubular formation, which was inhibited by addition of 10 microM PD-98059. Stimulation of ECV304 cells by the combination of high D-glucose and insulin also caused an activation of MAPK, which was again obliterated by the same concentration of PD-98059. In conclusion, human endothelial cell migration and tubular formation are stimulated by high D-glucose and insulin in different ways. In the former reaction, either is effective, a combination of the two results in an additive effect, and activation of protein kinase C is involved. In contrast, tubular formation will only occur in the presence of a combination of high D-glucose and insulin, and MAPK plays an essential role.

Fibroblast growth factor 2 enhances early stages of in vitro endothelial repair by microfilament bundle reorganization and cell elongation

As endothelial cells convert from quiescent to migrating cells over 8 h along a wound edge, actin microfilaments undergo well-defined sequential changes characterized by an initial random distribution followed by a parallel and then a perpendicular orientation of microfilaments with respect to the wound edge. The latter is associated with subsequent cell migration. We tested the hypothesis that fibroblast growth factor 2 (FGF-2) can enhance the very early stages of wound repair even prior to migration and that FGF-2 enhancement of wound repair is associated with changes in the endothelial actin cytoskeleton. Using an in vitro two-sided wound model, the addition of FGF-2 at the time of wounding enhanced the extent of wound closure over 8 h. Treatment with FGF-2 was associated with significantly longer cells along the wound edge at 4 and 8 h after wounding. When treated with increasing concentrations of neutralizing FGF-2 antibody, the extent of wound closure decreased over 8 h and was associated with a decrease in cell length along the wound edge. Actin microfilaments were localized using rhodamine phalloidin and viewed using laser confocal microscopy. At 4 h after wounding, FGF-2 treatment was associated with significantly more cells along the wound expressing perpendicular microfilaments compared to untreated cells, which suggested a more rapid transition of parallel to perpendicular microfilament distribution. Thus, FGF-2 affects the very early stages of wound repair prior to migration by enhancing wound closure due to the early appearance of perpendicular microfilaments and lengthening of cells along the wound edge.

Inhibitory mechanisms by which suramin may attenuate neointimal formation after balloon angioplasty

Restenotic neointimal lesions, a major limitation to coronary angioplasty, develop in response to diverse signals and depend on three properties of activated arterial smooth muscle cells (SMCs): proliferation, migration, and abnormal production of extracellular matrix. Most of the pharmacologic approaches targeting specific pathogenic factors facilitating development of restenosis have failed in clinical trials. Our results indicate that the polysulfonated naphthylurea suramin, a "non-specific drug" that interferes with multiple cellular proteins, inhibits neointimal formation in rabbit iliac arteries after balloon-catheter injury administered throughout the critical period of several weeks after the procedure. In vitro studies aimed at dissecting the mechanism(s) underlying the suramin-dependent effect demonstrated that, in addition to an inhibitory effect on SMC proliferation, suramin inhibited fibronectin and elastin deposition and the migration of SMCs through elastin membranes and into scratch gaps of monolayer cultures. We also demonstrated that suramin causes cell-surface accumulation of the elastin binding protein, a receptor that not only anchors SMCs to the extracellular matrix, but also inhibits SMC response to interleukin-1beta (IL-1beta). We conclude that suramin acts as a multitarget inhibitor of SMC activation and has a therapeutic potential as an agent that may attenuate arterial restenosis after angioplasty.

Parathyroid hormone regulates the expression of fibroblast growth factor-2 mRNA and fibroblast growth factor receptor mRNA in osteoblastic cells

We examined the effect of parathyroid hormone (PTH) on basic fibroblast growth factor-2 (FGF-2) and FGF receptor (FGFR) expression in osteoblastic MC3T3-E1 cells and in neonatal mouse calvariae. Treatment of MC3T3-E1 cells with PTH(1-34) (10-8M) or forskolin (FSK; 10-5M) transiently increased a 7 kb FGF-2 transcript with a peak at 2 h. The PTH increase in FGF-2 mRNA was maintained in the presence of cycloheximide. PTH also increased FGFR-1 mRNA at 2 h and transiently increased FGFR-2 mRNA at 1 h. FGFR-3 and FGFR-4 mRNA transcripts were not detected in MC3T3-E1 cells. In cells transiently transfected with an 1800-bp FGF-2 promoter-luciferase reporter, PTH and FSK increased luciferase activity at 2 h and 4 h. Immunohistochemistry showed that PTH and FSK increased FGF-2 protein labeling in the nuclei of MC3T3-E1 cells. PTH also increased FGF-2 mRNA, and FGFR-1 and FGFR-2 mRNA levels within 30 minutes in neonatal mouse calvarial organ cultures. We conclude that PTH and cAMP stimulate FGF-2 mRNA abundance in part through a transcriptional mechanism. PTH also regulated FGFR gene expression. We hypothesize that some effects of PTH on bone remodeling may be mediated by regulation of FGF-2 and FGFR expression in osteoblastic cells.

A novel, quantitative model for study of endothelial cell migration and sprout formation within three-dimensional collagen matrices

Interactions between migratory endothelial cells (ECs) and surrounding extracellular matrix (ECM) are of central importance to vascular growth. Here, we present a new model of EC migration and morphogenesis within three-dimensional ECM termed "radial invasion of matrix by aggregated cells" (RIMAC). In the RIMAC model, single aggregates of defined numbers of bovine aortic ECs were embedded within small, lenticular gels of type I collagen supported by annuli of nylon mesh. Culture of the gels in nutrient media resulted in quantifiable, reproducible, radial migration of ECs into the collagen. The angiogenic proteins basic fibroblast growth factor (bFGF) and vascular endothelial growth factor (VEGF) each stimulated migration of ECs in a concentration-dependent manner. In combination, bFGF and VEGF stimulated migration synergistically. In contrast, transforming growth factor-beta1 inhibited migration of ECs. Low concentrations (0.1-0.5 ng/ml) of VEGF induced ECs to form multicellular sprouts, some of which possessed lumen-like spaces. Mitomycin C, an inhibitor of cell proliferation, did not affect the migration of ECs into collagen induced by 0.5 ng/ml VEGF but moderately inhibited migration induced by 5 ng/ml VEGF. Increasing the density (concentration) of the collagen gel inhibited the migration of single ECs and increased the branching and anastomosis of multicellular sprouts. We conclude that the RIMAC model is a highly efficacious assay for the screening of potentially angiogenic and angiostatic compounds and, moreover, is advantageous for mechanistic studies of vascular morphogenesis.

Mast cells and their mediators in cutaneous wound healing--active participants or innocent bystanders?

Mast cells are traditionally viewed as effector cells of immediate type hypersensitivity reactions. There is, however, a growing body of evidence that the cells might play an important role in the maintenance of tissue homeostasis and repair. We here present our own data and those from the literature elucidating the possible role of mast cells during wound healing. Studies on the fate of mast cells in scars of varying ages suggest that these cells degranulate during wounding, with a marked decrease of chymase-positive cells, although the total number of cells does not decrease, based on SCF-receptor staining. Mast cells contain a plethora of preformed mediators like heparin, histamine, tryptase, chymase, VEGF and TNF-alpha which, on release during the initial stages of wound healing, affect bleeding and subsequent coagulation and acute inflammation. Various additional vasoactive and chemotactic, rapidly generated mediators (C3a, C5a, LTB4, LTC4, PAF) will contribute to these processes, whereas mast cell-derived proinflammatory and growth promoting peptide mediators (VEGF, FGF-2, PDGF, TGF-beta, NGF, IL-4, IL-8) contribute to neoangiogenesis, fibrinogenesis or re-epithelization during the repair process. The increasing number of tryptase-positive mast cells in older scars suggest that these cells continue to be exposed to specific chemotactic, growth- and differentiation-promoting factors throughout the process of tissue remodelling. All these data indicate that mast cells contribute in a major way to wound healing. their role as potential initiators of or as contributors to this process, compared to other cell types, will however have to be further elucidated.

Dual activities of 22-24 kDA basic fibroblast growth factor: inhibition of migration and stimulation of proliferation

Basic fibroblast growth factor (FGF2) is synthesized as four isoforms with molecular weights of 24, 22.5, 22, and 18 kDa, with each of the three higher molecular weight forms (hmwFGF2) produced by the initiation of translation at one of three upstream CUG codons. We have shown that bovine arterial endothelial cells export the high molecular weight forms of FGF2 (hmwFGF2) in a 17beta-estradiol-dependent manner (Piotrowicz et al., 1997, J Biol Chem 272:7042-7047). To determine whether the hmwFGF2 forms affected cell behavior after release, we evaluated the effect of recombinant hmwFGF2 on the growth and migration of endothelial cells and mammary carcinoma cells (MCF-7). Treatment with the recombinant protein resulted in the inhibition of endothelial cell migration by 45% and MCF-7 cell migration by 70%. HmwFGF2-dependent inhibition was observed when endothelial cell migration was stimulated by 18 kDa FGF2 or vascular endothelial growth, and MCF cell migration was stimulated with insulin-like growth factor. In each case, inclusion of an antibody against the 55 amino acid amino terminal end of 24 kDa FGF2 abrogated the inhibition of migration, while antibodies to the 18 kDa FGF2 domain had no effect. When endothelial cells were cultured under conditions which promoted export of hmwFGF2, a 40% decrease in motility was observed which was reversed by the antibodies to the 24 kDa FGF2. Thus, both recombinant and endogenously produced hmw-FGF2 are capable of inhibiting migration. In contrast to the ubiquitous effect on migration, hmwFGF2 had no effect on endothelial cell growth but stimulated MCF-7 growth equally as well as the 18 kDa FGF2 (threefold). Antibodies to the 18 kDa domain of 24 kDa FGF2 blocked the growth-promoting activity of hmwFGF2, but those to the amino terminal end were ineffective. These data suggest that hmwFGF2 has dual activities, an inhibitory effect on cell migration and a growth-stimulating effect. The two activities can be localized to different parts of hmwFGF2: inhibitory activity to the amino terminal 55 amino acids (which are absent from the 18 kDa FGF2) and growth-promoting activity to the 18 kDa domain. Therefore, the ratio of hmwFGF2 and 18 kDa FGF2 in the extracellular space may provide a mechanism of control for angiogenesis and mammary tumor development.

The urokinase receptor. A cell surface, regulated chemokine

Mice deficient for the urokinase plasminogen activator (uPA) gene are deficient in the recruitment of T cells and macrophages and succumb to bacterial infections. High levels of uPA or of its receptor (uPAR, CD87) are produced in human cancers and are strong prognostic indicators of relapse. Thus uPA and uPAR have a profound influence on cell migration. This set of molecules is known to regulate surface proteolysis, cell adhesion and chemotaxis. We have investigated the mechanism involved in uPAR-dependent chemotaxis. Chemotaxis is induced through an uPA-dependent conformational change in uPAR which uncovers a very potent chemotactic epitope acting through a pertussis-toxin sensitive step and activating intracellular tyrosine kinases. The epitope is located in the linker region between domain D1 and D2 of uPAR. Binding of uPA transforms uPAR from a receptor for uPA into a pleiotropic ligand ("activated uPAR") for other still unidentified surface molecules. Through these "adaptors", uPAR causes cytoskeletal changes, activation of kinases and directional cell migration. The conformational change can be substituted by cleavage between domain D1 and D2, in an area that can be cleaved by uPA itself at high efficiency.

Prostaglandins regulate the expression of fibroblast growth factor-2 in bone

We examined the effect of PGs, particularly PGF2alpha, on basic fibroblast growth factor-2 (FGF-2) messenger RNA (mRNA) and protein in the rat osteoblastic cell line Py1a and in fetal rat calvariae. Py1a cells expressed multiple FGF-2 mRNA transcripts. PGF2alpha dose-dependently increased the 6-kb transcript at 6 h. The selective PGF2alpha agonist, fluprostenol (Flup), was more potent than PGF2alpha. Phorbol myristate acetate (10(-6) M) also increased a 6-kb mRNA at 6 h. By immunofluorescence microscopy, Flup increased perinuclear staining for FGF-2 protein at 6 h and nuclear labeling at 24 h. Immunogold labeling of calvariae revealed that treatment with Flup for 3 h caused a transition of FGF expression from matrix to cells and an increase in cytoplasmic labeling for FGF-2 protein in periosteal cells and in osteoblasts. After treatment with Flup for 24 h, nuclear labeling was marked in periosteal cells and in osteoblasts, and a further increase in cytoplasmic labeling for FGF-2 was noted in osteocytes, periosteal cells, and osteoblasts. We conclude that PGs can increase FGF-2 mRNA and protein in bone cells. Because the effect of Flup was mimicked by phorbol myristate acetate, we hypothesize that PGs' regulation of FGF-2 is mediated by a PGF2alpha-selective receptor acting through protein kinase C. Hence, effects of PGs on bone remodeling may be mediated, in part, by endogenous FGF-2.

Adenoviral-mediated expression of antisense RNA to fibroblast growth factors disrupts murine vascular development

Fibroblast growth factors (FGFs) are expressed in the developing embryo and are postulated to regulate embryonic and vascular growth. The goal of this study was to elucidate the role of basic fibroblast growth factor (FGF-2) in early murine embryonic cardiovascular development in the mouse embryo. Gestation day 7.5 embryos were harvested and placed in culture, and 12 hr later replication-defective adenovirus (0.5 x 10(6) plaque forming units) encoding either beta-galactosidase or antisense FGF-2 RNA was injected into the sinus venosus of the cultured embryos. Embryos receiving only replication-defective adenovirus expressing the beta-galactosidase gene continued to develop normally over the next 12 hr. In contrast, those receiving adenovirus encoding antisense FGF-2 RNA displayed marked morphogenetic abnormalities, including cessation of growth and abnormal yolk sac vascular development, even though the embryonic hearts continued to beat. Abnormal development of the yolk sac vasculature was confirmed by microangiography and by histologic examination. Coinjection of virus carrying FGF-2 cDNA in the sense orientation reversed the effects of antisense FGF-2 RNA expression. These results confirm the efficacy of the replication-defective adenovirus for targeting gene expression to the developing vasculature and provide evidence for a critical role of FGF in the normal vascular assembly in the early embryo. Cessation of embryonic growth on expression of antisense FGF-2 RNA was most likely attributable to failure of efficient circulation of the early embryonic blood cells from the yolk sac into the embryo.

Modulation of human endothelial cell proliferation and migration by fucoidan and heparin

Fucoidan is a sulfated polysaccharide extracted from brown seaweeds. It has anticoagulant and antithrombotic properties and inhibits, as well as heparin, vascular smooth muscle cell growth. In this study, we investigated, in the presence of serum and human recombinant growth factors, the effects of fucoidan and heparin on the growth and migration of human umbilical vein endothelial cells (HUVEC) in culture. We found that fucoidan stimulated fetal bovine serum-induced HUVEC proliferation, whereas heparin inhibited it. In the presence of fibroblast growth factor-1 (FGF-1), both fucoidan and heparin potentiated HUVEC growth. In contrast, fucoidan and heparin inhibited HUVEC proliferation induced by FGF-2, but did not influence the mitogenic activity of vascular endothelial growth factor (VEGF). In the in vitro migration assay from a denuded area of confluent cells, the two sulfated polysaccharides markedly enhanced the migration of endothelial cells in the presence of FGF-1. Finally, a weak inhibitory effect on cell migration was found only with the two polysaccharides at high concentrations (> or = 100 micro/ml) in presence of serum or combined with FGF-2. All together, the results indicated that heparin and fucoidan can be used as tools to further investigate the cellular mechanisms regulating the proliferation and migration of human vascular cells. Moreover, the data already suggest a potential role of fucoidan as a new therapeutic agent of vegetal origin in the vascular endothelium wound repair.

Protamine inhibits angiogenesis and growth of C6 rat glioma; a synergistic effect when combined with carmustine

Protamine inhibits angiogenesis and blocks endothelial, fibroblast and platelet growth factors. Human and experimental gliomas spread and grow in response to both paracrine and autocrine release of these factors. Our objective was to study the effect of protamine administration on cell proliferation, angiogenesis and tumoral growth of C6 glioma. Additionally, we compared the antitumoral effect of protamine with that of another inhibitor of angiogenesis, suramin, and investigated a potential synergistic antitumoral action of low doses of protamine combined with the antineoplastic carmustine. C6 glioma cells were implanted subcutaneously in Wistar rats. A highly malignant glioma developed in 80% of animals; when the tumour reached a diameter of 1.5 cm, either protamine, suramin, carmustine or protamine plus carmustine were administered in various doses. Tumour parameters were measured and compared between groups. In a dose-dependent manner, protamine reduced tumour volume (P < 0.001), mitotic index (P < 0.05), vascular density (P < 0.05) and cell viability (P < 0.005) of C6 glioma. An ultrastructural study demonstrated membranous inclusions in the cytoplasm of 28% of tumoral and endothelial cells of tumours from animals treated with protamine. The inhibition of tumoral growth produced by moderate doses of protamine was similar to that produced by toxic doses of suramin. The combination of protamine and carmustine had a synergistic curtailing effect on tumoral growth (P < 0.001). Our results indicate that protamine is an effective agent against glioblastoma; in non-toxic doses it could potentiate the antineoplastic effect of nitrosoureas for the treatment of glial tumours.

Human endothelial cell migration is stimulated by urokinase plasminogen activator:plasminogen activator inhibitor 1 complex released from endometrial stromal cells stimulated with transforming growth factor beta1; possible mechanism for paracrine stimulation of endometrial angiogenesis

Human endometrial stromal cell cultures, stimulated for two days with recombinant transforming growth factor beta1 (TGFbeta1; 10 ng/ml), contained conditioned medium concentrations of urokinase plasminogen activator (uPA), plasminogen activator inhibitor 1 (PAI1), and uPA:PAI1 complex. Since a number of cellular effects have been reported to follow a binding of enzymatically inactive uPA to the receptor in different cell types, we studied the influence of uPA:PAI1 complex on human umbilical vein endothelial cells (HUVEC) and human microvascular endothelial cells (HMEC-1). Increasing concentrations of uPA:PAI1 complex as well as free uPA resulted in a dose-dependent stimulation of endothelial cell migration. Stimulation by the complex was of the same magnitude as that of free uPA on a molar basis and reached its maximum at 1 nM in both cell types. PAI1 by itself, however, had no effect on cell migration. The migratory response to both uPA and the uPA:PAI1 complex was inhibited by antibody adhesion to the cell surface receptor for uPA. In addition, we found that TGFss1 had a direct stimulatory effect on migration in both HUVEC and HMEC-1. This response did not, however, involve the binding of uPA to the uPA receptor. Since TGFbetas are expressed in endometrial tissue and reportedly stimulate angiogenesis in other tissues in vivo, though not endothelial cell proliferation in vitro, they may engage in the regeneration of endometrial vasculature indirectly via perivascular cells. We found that the uPA:PAI1 complex, when released from endometrial stromal cells in response to TGFbeta1, stimulated endothelial cell migration. This suggests a possible mechanism for paracrine stimulation of endometrial angiogenesis.

Basic fibroblast growth factor is neither necessary nor sufficient for the development of retinal neovascularization

Basic fibroblast growth factor (FGF2) is constitutively expressed in the retina and its expression is increased by a number of insults, but its role in the retina is still uncertain. This study was designed to test the hypothesis that altered expression of FGF2 in the retina affects the development of retinal neovascularization. Mice with targeted disruption of the Fgf2 gene had no detectable expression of FGF2 in the retina by Western blot, but retinal vessels were not different in appearance or total area from wild-type mice. When FGF2-deficient mice were compared with wild-type mice in a murine model of oxygen-induced ischemic retinopathy, they developed the same amount of retinal neovascularization. Transgenic mice with a rhodopsin promoter/Fgf2 gene fusion expressed high levels of FGF2 in retinal photoreceptors but developed no retinal neovascularization or other abnormalities of retinal vessels; in the ischemic retinopathy model, they showed no significant difference in the amount of retinal neovascularization compared with wild-type mice. These data indicate that FGF2 expression is not necessary nor sufficient for the development of retinal neovascularization. This suggests that agents that specifically antagonize FGF2 are not likely to be useful adjuncts in the treatment of retinal neovascularization and therapies designed to increase FGF2 expression are not likely to be complicated by retinal neovascularization.

Neuropilin-1 is a placenta growth factor-2 receptor

Placenta growth factor (PlGF) belongs to the family of vascular endothelial growth factors (VEGFs). It binds to the flt-1 VEGF receptor but not to the KDR/flk-1 receptor which is thought to mediate most of the angiogenic and proliferative effects of VEGF. Three PlGF isoforms are produced by alternative splicing. PlGF-1 and PlGF-3 differ from PlGF-2 since they lack the exon 6 encoded peptide which bestows upon PlGF-2 its heparin binding properties. Cross-linking experiments revealed that 125I-PlGF-2 binds to two endothelial cell surface receptors in a heparin dependent fashion. The binding of 125I-PlGF-2 to these receptors was inhibited by an excess of PlGF-2 and by the 165-amino acid form of VEGF (VEGF165), but not at all by VEGF121 and very marginally if at all by PlGF-1. The apparent molecular weight and the binding characteristics of these receptors correspond to those of the recently identified VEGF165 specific receptor neuropilin-1, and we therefore conclude that neuropilin-1 is a receptor for PlGF-2. The binding of 125I-PlGF-2 as well as the binding of 125I-VEGF165 to these receptors was inhibited by a synthetic peptide derived from exon 6 of PlGF. Furthermore, the binding of 125I-PlGF-2, but not that of 125I-VEGF165, was also inhibited by a synthetic peptide derived from exon 7 of PlGF. These observations indicate that the peptides encoded by these exons probably participate in the formation of the domain which mediates the binding of PlGF-2 to these receptors. We have also determined, using chemically modified heparin species, that the presence of sulfate moieties on the glucosamine-O-6 and on the iduronic acid-O-2 groups of heparin was required for the potentiation of 125I-PlGF-2 binding to these receptors. To determine if PlGF-2 is able to induce biological responses that are not induced by PlGF-1, we compared the effects of PlGF-1 and PlGF-2 on the migration and proliferation of endothelial cells. Both PlGF forms induced migration of endothelial cells. However, there was no quantitative difference between the response to PlGF-2 and the response to PlGF-1. Furthermore, neither PlGF-1 nor PlGF-2 had any effect upon the proliferation of the endothelial cells.

Endogenous FGF1-induced activation and synthesis of extracellular signal-regulated kinase 2 reduce cell apoptosis in retinal-pigmented epithelial cells

Retinal-pigmented epithelial (RPE) cell survival is critical to the maintenance of the function of the neural retinal and in the development of various retina degenerations. We investigated molecular mechanisms involved in this function by assessing apoptosis in RPE cells following serum deprivation. Apoptosis induced by serum withdrawal is lower in aged RPE cells because of higher endogenous acidic fibroblast growth factor (FGF1) synthesis and secretion. These experiments examined several aspects of FGF signaling and the contribution of endogenous FGF1 to activation of the extracellular signal-regulated kinase 2 (ERK2). In aged RPE cells, FGFR1 was rapidly activated, and its autophosphorylation followed the kinetics of endogenous FGF1 secretion, before the onset of apoptosis. ERK2 phosphorylation, activity, and de novo synthesis increased at the same time. In marked contrast, no de novo JNK1 synthesis was observed. MEK1 inhibition resulted in lower levels of ERK2 activation and synthesis and higher levels of apoptosis. Treatment with neutralizing anti-FGF1 or blocking anti-FGFR1 antibodies mimics these effects. Thus, this study strongly suggests that the survival-increasing effect of FGF1 in aged RPE cells is because of an autocrine/paracrine loop in which the ERK2 cascade plays a pivotal role.

Fibroblast growth factors and their receptors

Fibroblast growth factors (FGFs) represent a group of polypeptide mitogens eliciting a wide variety of responses depending upon the target cell type. The knowledge of the cell surface receptors mediating the effects of FGFs has recently expanded remarkably. The complexity of the FGF family and the FGF-induced responses is reflected in the diversity and redundancy of the FGF receptors. In this review, a number of biochemical characteristics and biological properties of the FGF family and its receptors are described and their expression both in normal tissues and in tumours is discussed. Finally we speculate on the targetting of growth inhibition agents to tumours through FGF receptors.

Induction of Ets-1 in endothelial cells during reendothelialization after denuding injury

Ets-1, a transcription factor, is induced in endothelial cells (ECs) during angiogenesis. Here, we investigated the expression of Ets-1 during reendothelialization. When a confluent monolayer of human umbilical vein endothelial cell line, ECV304, was denuded, ECV304 at the wound edge expressed Ets-1. An immunohistochemical analysis revealed that Ets-1 accumulated in migrating cells at the wound edge and returned to basal level when reendothelialization was accomplished. This induction of Ets-1 could be reproduced in in vivo denudation of rat aortic endothelium by a balloon catheter. The induction of Ets-1 in ECs after denudation was regulated transcriptionally, and humeral factors released from injured ECs might not be responsible. Mitogen-activated protein kinase (MAPK) activities were investigated to explore the mechanism of this induction. Although extracellular signal-regulated protein kinase 1/2 (ERK1/2), c-Jun N-terminal kinase 1 (JNK1), and p38 were activated after denudation, the activation of ERK1 and p38 was more rapid and prominent. PD98059, a specific MAPK/ERK kinase (MEK) 1 inhibitor, did not affect the induction of ets-1 mRNA, whereas SB203580, a specific p38 inhibitor, almost completely abrogated its induction. These results indicate that Ets-1 is induced in ECs after denudation through activation of p38. This induction of Ets-1 may be relevant for reendothelialization by regulating the expression of certain genes.

The suppression of fibroblast growth factor 2/fibroblast growth factor 4-dependent tumour angiogenesis and growth by the anti-growth factor activity of dextran derivative (CMDB7)

Our previous studies showed that carboxymethyl benzylamide dextran (CMDB7) blocks basic fibroblast growth factor (FGF-2)-dependent cell proliferation of a human breast epithelial line (HBL100), suggesting its potential role as a potent antiangiogenic substance. The derived cell line (HH9), which was transformed with the hst/FGF4 gene, has been shown to be highly proliferative in vitro and to induce angiogenic tumours in nude mice. We show here that CMDB7 inhibits the mitogenic activities of the conditioned media from HBL 100 and HH9 cells in a dose-dependent manner. When HH9 cells were injected s.c. into nude mice, CMDB7 treatment (300 mg kg(-1) week(-1)) suppressed the tumour take and the tumour growth by about 50% and 80% respectively. Immunohistochemical analysis showed a highly significant decrease, by more than threefold, in the endothelial density of viable tumour regions, together with a significant increase in the necrosis area. This antiangiogenic activity of CMDB7 was further demonstrated by direct inhibition of calf pulmonary artery (CPAE) and human umbilical vein (HUVEC) endothelial cell proliferation and migration in vitro. In addition, we showed that CMDB7 inhibits specifically the mitogenic effects of the growth factors that bind to heparin such as FGF-2, FGF-4, platelet-derived growth factor (PDGF-BB) and transforming growth factor (TGF-beta1), but not those of epidermal growth factor (EGF) and insulin-like growth factor (IGF-1). These results demonstrate that CMDB7 inhibits FGF-2/FGF-4-dependent tumour growth and angiogenesis, most likely by disrupting the autocrine and paracrine effects of growth factors released from the tumour cells.

Irsogladine maleate inhibits angiogenesis in wild-type and plasminogen activator-deficient mice

BACKGROUND

The activation of the zymogen plasminogen to the serine protease plasmin by urokinase-type (uPA) and tissue-type (tPA) plasminogen activators (PA) is an important event in a variety of physiologic and pathophysiologic processes in mammals. Enhanced PA activity occurs during angiogenesis and has been correlated in vitro and in vivo with increased tumor aggressiveness and is an indicator of poor prognosis in a variety of tumors in humans. Preliminary studies suggest that the antiulcer drug irsogladine maleate (IM) diminishes PA activity in vitro and may inhibit angiogenesis in vivo. To define the precise mechanism of angiogenesis inhibition by IM in vivo, we tested the ability of IM to blunt angiogenesis in a mouse cornea neovascularization model performed in wild-type and PA-knockout mice.

METHODS

Three days prior to pellet implantation, groups of C57Bl/6 wild-type, uPA-deficient (upA-/-), and tPA-deficient (tPA-/-) mice received IM (300 mg/kg), IM (500 mg/kg), or vehicle (0.5% carboxymethylcellulose) via oral gavage. After 3 days of treatment, hydron polymer-coated pellets of sucrose aluminum sulfate containing 100 ng of basic fibroblast growth factor (bFGF) were inserted into surgically created pockets in the cornea of each mouse. On postoperative day 6, the neovascularization of each cornea was evaluated by a blinded observer using slit lamp microscopy and photographed. Angiogenesis was quantified by calculating vascular area (mm2) +/- SEM using a modified formula for a half ellipse that incorporates calibrated vessel measurements [Vessel length (mm) x Clock hours x pi x 0.2].

RESULTS

IM treatment (300 and 500 mg/kg/day) resulted in a dose-dependent reduction of angiogenesis in wild-type mice by 21 and 45.3% (P < 0.02, P < 0.001), in tPA-deficient mice by 42.6 and 46% (P < 0.001, P < 0.001), and in uPA-deficient mice by 27.2 and 46% (P < 0.05, p < 0.001), respectively. No quantitative differences in neovascularization were observed in either treatment group between transgenic mouse strains. No toxicity was noted in any group.

CONCLUSION

IM inhibits bFGF-induced angiogenesis in wild-type, tPA-knockout, and uPA-knockout mice. The observation that IM significantly diminishes angiogenesis in both PA-deficient mice and wild-type mice suggests that the mechanism of action of IM may be independent of plasminogen activation.

Fibroblast growth factor-2 (FGF-2) induces vascular endothelial growth factor (VEGF) expression in the endothelial cells of forming capillaries: an autocrine mechanism contributing to angiogenesis

FGF-2 and VEGF are potent angiogenesis inducers in vivo and in vitro. Here we show that FGF-2 induces VEGF expression in vascular endothelial cells through autocrine and paracrine mechanisms. Addition of recombinant FGF-2 to cultured endothelial cells or upregulation of endogenous FGF-2 results in increased VEGF expression. Neutralizing monoclonal antibody to VEGF inhibits FGF-2-induced endothelial cell proliferation. Endogenous 18-kD FGF-2 production upregulates VEGF expression through extracellular interaction with cell membrane receptors; high-Mr FGF-2 (22-24-kD) acts via intracellular mechanism(s). During angiogenesis induced by FGF-2 in the mouse cornea, the endothelial cells of forming capillaries express VEGF mRNA and protein. Systemic administration of neutralizing VEGF antibody dramatically reduces FGF-2-induced angiogenesis. Because occasional fibroblasts or other cell types present in the corneal stroma show no significant expression of VEGF mRNA, these findings demonstrate that endothelial cell-derived VEGF is an important autocrine mediator of FGF-2-induced angiogenesis. Thus, angiogenesis in vivo can be modulated by a novel mechanism that involves the autocrine action of vascular endothelial cell-derived FGF-2 and VEGF.

Activation of the MAP kinase pathway by FGF-1 correlates with cell proliferation induction while activation of the Src pathway correlates with migration

FGF regulates both cell migration and proliferation by receptor-dependent induction of immediate-early gene expression and tyrosine phosphorylation of intracellular polypeptides. Because little is known about the disparate nature of intracellular signaling pathways, which are able to discriminate between cell migration and proliferation, we used a washout strategy to examine the relationship between immediate-early gene expression and tyrosine phosphorylation with respect to the potential of cells either to migrate or to initiate DNA synthesis in response to FGF-1. We demonstrate that transient exposure to FGF-1 results in a significant decrease in Fos transcript expression and a decrease in tyrosine phosphorylation of the FGFR-1, p42(mapk), and p44(mapk). Consistent with these biochemical effects, we demonstrate that attenuation in the level of DNA synthesis such that a 1.5-h withdrawal is sufficient to return the population to a state similar to quiescence. In contrast, the level of Myc mRNA, the activity of Src, the tyrosine phosphorylation of cortactin, and the FGF-1-induced redistribution of cortactin and F-actin were unaffected by transient FGF-1 stimulation. These biochemical responses are consistent with an implied uncompromised migratory potential of the cells in response to growth factor withdrawal. These results suggest a correlation between Fos expression and the mitogen-activated protein kinase pathway with initiation of DNA synthesis and a correlation between high levels of Myc mRNA and Src kinase activity with the regulation of cell migration.

Endothelial cells differentially express functional CXC-chemokine receptor-4 (CXCR-4/fusin) under the control of autocrine activity and exogenous cytokines

Analysis of endothelial cell (EC) chemokine receptor expression by RT-PCR revealed that EC essentially do not express CC-chemokine receptors whereas they express all known CXC-chemokine receptors. Endotheliotropic functions of ligands for CXCR-1, CXCR-2, and CXCR-3 have previously been described. We have consequently performed a detailed analysis of endothelial CXCR-4 expression. CXCR-4 is constitutively expressed by quiescent, resting EC. Cytokine stimulation revealed that bFGF upregulates endothelial CXCR-4 expression, whereas TNF alpha downregulates endothelial CXCR-4 expression. Expression of CXCR-4 mRNA as well as protein is also upregulated in autocrine activated, migrating bovine aortic endothelial cells (BAEC). Furthermore, migrating BAEC preferentially present CXCR-4 on the cell surface as evidenced by cytochemistry and FACS analysis. Lastly, the monospecific CXCR-4 ligand SDF-1 was found to act as a potent inducer of EC chemotaxis. In summary, the data indicate that the CXCR-4/SDF-1 receptor ligand interaction may be an important regulator of activated endothelial cell functions as they occur during vascular remodeling and angiogenesis.

Clotrimazole, an imidazole antimycotic, is a potent inhibitor of angiogenesis

Clotrimazole, an imidazole antimycotic, interferes with the rise in cytosolic Ca2+ and inhibits cell proliferation in a reversible manner. Here we describe the effect of clotrimazole on vascular endothelial cells (ECs). Clotrimazole inhibited the proliferation of ECs stimulated with typical angiogenic growth factors; vascular endothelial growth factor and basic fibroblast growth factor (bFGF). This inhibitory effect of clotrimazole was dose-dependent and the maximal inhibition was observed at a concentration of 10 mM. We did not observe any increase in 51Cr release from ECs during treatment with 10 microM clotrimazole. Moreover, clotrimazole inhibited the basal and bFGF-stimulated migration of ECs. As clotrimazole inhibited two principle components of angiogenesis; the proliferation and migration of ECs, we examined whether clotrimazole inhibited angiogenesis. Tube formation by ECs in type 1 collagen gel was investigated, and clotrimazole was found to be significantly inhibitory. The inhibitory effect of clotrimazole on angiogenesis was further confirmed in an in vivo angiogenesis model of murine Matrigel plug assay. These results demonstrate that clotrimazole is a potent inhibitor of angiogenesis.

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.