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

Correlation between basic fibroblast growth factor immunostaining of stromal cells and stromelysin-3 mRNA expression in human breast carcinoma

We examined the localization of basic fibroblast growth factor (bFGF) in a series of human breast carcinomas using immunohistochemistry. Staining was observed in tumour cells in 15 out of 54 (28%) tumours and in the adjacent stroma in 34 out of 54 (63%) tumours examined. No correlation was observed between positive staining of these two compartments. The relationship between bFGF staining and expression of the metalloprotease stromelysin-3, and between bFGF and microvessel density, was examined. A statistically significant correlation (P < 0.003) was observed between bFGF staining of the stromal compartment and high expression of stromelysin-3 (ST-3; MMP-11) metalloprotease mRNA by stromal cells. In contrast, no correlation was observed between bFGF and intratumour microvessel density (IMD). These results raise the possibility that bFGF may be involved in the induction of stromelysin-3 mRNA expression in breast cancer stroma.

Cell-associated activation of latent transforming growth factor-beta by calpain

Transforming growth factor-beta (TGF-beta) is normally secreted in a latent form, and plasmin-mediated proteolytic cleavage of latency-associated peptide (LAP), a component of latent TGF-beta complex that makes the complex inactive, activates latent TGF-beta. In the present study, we investigated the possible involvement of calpain, one of the cysteine proteases, in the activation of latent TGF-beta. When recombinant latent TGF-beta was incubated with calpain (1-10 u/ml) in a test tube, calpain cleaved LAP and released mature TGF-beta from the latent complex. When calpain was applied to cultured bovine capillary endothelial (BCE) cells, a low concentration of calpain (0.05-0.1 u/ml) inhibited the migration and proliferation of the cells, and these inhibitory effects were abrogated by anti-TGF-beta antibody as well as by calpain inhibitor peptide, but not by alpha2-antiplasmin, a specific inhibitor of plasmin. Active TGF-beta was detected in the conditioned medium of BCE cells collected in the presence of calpain. Chemical cross-linking of (125)I-calpain to BCE cells followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis indicated that calpain bound to the cell surface through chondroitinase ABC-sensitive proteoglycan. In addition, treatment of the BCE cells with chondroitinase ABC abrogated the inhibitory effect of calpain on the migration of these cells. Our data thus suggest that calpain is able to activate latent TGF-beta through a mechanism independent of plasmin. This activation is efficient in the presence of cells, and calpain binds to the cell surface via proteoglycan and activates latent TGF-beta, which is targeted to the same surface.

Receptor-independent role of urokinase-type plasminogen activator in pericellular plasmin and matrix metalloproteinase proteolysis during vascular wound healing in mice

It has been proposed that the urokinase receptor (u-PAR) is essential for the various biological roles of urokinase-type plasminogen activator (u-PA) in vivo, and that smooth muscle cells require u-PA for migration during arterial neointima formation. The present study was undertaken to evaluate the role of u-PAR during this process in mice with targeted disruption of the u-PAR gene (u-PAR-/-). Surprisingly, u-PAR deficiency did not affect arterial neointima formation, neointimal cell accumulation, or migration of smooth muscle cells. Indeed, topographic analysis of arterial wound healing after electric injury revealed that u-PAR-/- smooth muscle cells, originating from the uninjured borders, migrated over a similar distance and at a similar rate into the necrotic center of the wound as wild-type (u-PAR+/+) smooth muscle cells. In addition, u-PAR deficiency did not impair migration of wounded cultured smooth muscle cells in vitro. There were no genotypic differences in reendothelialization of the vascular wound. The minimal role of u-PAR in smooth muscle cell migration was not because of absent expression, since wild-type smooth muscle cells expressed u-PAR mRNA and functional receptor in vitro and in vivo. Pericellular plasmin proteolysis, evaluated by degradation of 125I-labeled fibrin and activation of zymogen matrix metalloproteinases, was similar for u-PAR-/- and u-PAR+/+ cells. Immunoelectron microscopy of injured arteries in vivo revealed that u-PA was bound on the cell surface of u-PAR+/+ cells, whereas it was present in the pericellular space around u-PAR-/- cells. Taken together, these results suggest that binding of u-PA to u-PAR is not required to provide sufficient pericellular u-PA-mediated plasmin proteolysis to allow cellular migration into a vascular wound.

Stimulation of cell-surface urokinase-type plasminogen activator activity and cell migration in vascular endothelial cells by a novel hexapeptide analogue of neurotensin

To investigate if neurotensin (NT) could induce activation of urokinase-type plasminogen activator (uPA) in vascular endothelial cells, we utilized the acetyl-NT (8-13) analogue, TJN-950, in which the C-terminal leucine is reduced to leucinol. TJN-950 inhibited the binding of 125I-NT to membranes of newborn rat brains and of COS-7 cells transfected with rat NT receptor cDNA, but at 10(4) higher doses than NT (8-13). However, TJN-950 was as effective as NT in inducing the fibrinolytic activity in bovine vascular aortic and human umbilical vein endothelial cells, and enhanced the migration of vascular endothelial cells. Moreover, administration of TJN-950 induced neovascularization in the rat cornea in vivo. TJN-950 had no effect on expression of uPA, plasminogen activator inhibitor-1 or uPA receptor mRNA. The binding of 125I-TJN-950 to cell membranes was blocked by unlabeled uPA and TJN-950, but not the amino-terminal or 12-32 fragment of uPA. TJN-950 may enhance uPA activity in vascular endothelial cells by interacting with the uPA receptor, resulting in induction of angiogenesis.

Intracellular precursor interleukin (IL)-1alpha, but not mature IL-1alpha, is able to regulate human endothelial cell migration in vitro

The human umbilical vein endothelial cell (HUVEC) has a finite lifespan in vitro, and senescent HUVEC contain elevated levels of the negative growth regulator interleukin (IL)-1alpha. IL-1alpha is translated as a signal peptide sequence-less cytosolic 31-kDa precursor (IL-1alpha p), which undergoes proteolytic activation to release the mature carboxyl terminus 17-kDa protein (IL-1alpha m). Both the IL-1alpha p and IL-1alpha m proteins are biologically active as exogenous cytokines. Interestingly, only IL-1alpha p contains a nuclear localization sequence between residues 79 and 85. To further study the role of intracellular IL-1alpha in the regulation of human endothelial cell function, a spontaneous HUVEC transformant was stably transfected with IL-1alpha p, IL-1alpha m, and the IL-1alpha p K82N mutant, which attenuates the nuclear traffic of IL-1alpha p. Interestingly, the IL-1alpha p transfectants were found to have a lower migratory potential than either IL-1alpha m or IL-1alpha p K82N transfectants, and the addition of the IL-1 receptor antagonist did not alter the migration of these cells. Immunofluorescence microscopy demonstrated that only the IL-1alpha p transfectants exhibited prominent staining for beta-catenin-associated cell-to-cell contacts, as well as pronounced vimentin intermediate filaments and actin cytoskeleton staining. These data suggest that IL-1alpha p, and not IL-1alpha m, may function as an intracellular regulator of the migratory capacity of the human endothelial cell and that the nuclear localization sequence present within IL-1alpha p may be involved in regulating this function.

Effect of fibroblast growth factor saporin mitotoxins on human bladder cell lines

Mitotoxins targeted via high-affinity growth factor receptors on the cell surface are a potential means of anticancer therapy. We have evaluated the effect of a chemically conjugated (FGF2-SAP) and a fusion protein (rFGF2-SAP) mitotoxin containing FGF-2 and saporin on normal (FHs 738B1) and malignant bladder cell lines (HT1197, TCCSUP, EJ-6, and RT4). The FGF-saporins demonstrated potent cytotoxicity in malignant bladder cell lines with an ID50 range of 0.13-13.6 nM, whereas cells derived from normal fetal bladder (FHs 738B1) were less sensitive to FGF2-saporins (ID50 > 100 nM). Greater than a 100-fold difference in cytotoxicity between FGF-saporins and unconjugated saporin was observed. Assessment of cellular FGF-2 content and secretion showed that FHs 738B1 and TCCSUP contained and secreted significantly more FGF-2 compared to other cell lines tested. (125)I-FGF-2 receptor binding studies showed the presence of high-affinity (pM) FGF receptors on all bladder cell lines. Cross-linking studies revealed the presence of a major receptor-ligand complex of 90 kDa on FHs 738B1 and 160-170 kDa on the other bladder cell lines. All cell lines studied, except RT4, expressed solely FGFR-1. These studies demonstrate that FGF2-saporins have antiproliferative activity on human bladder cancer cell lines. However, the number of high-affinity FGF receptors, and FGF-2 cellular content and secretion are not absolute determinants of cellular sensitivity to FGF2-saporins.

Urokinase but not tissue plasminogen activator mediates arterial neointima formation in mice

To define the role of the plasminogen activators (PAs) tissue PA (t-PA) and urokinase PA (u-PA) in vascular wound healing, neointima formation and reendothelialization were evaluated after electric or mechanical arterial injury in mice with a single or combined deficiency of t-PA (t-PA-/-) and/or u-PA (u-PA-/-). In both models, neointima formation and neointimal cell accumulation were reduced in u-PA-/- and in t-PA-/-/u-PA-/- arteries but not in t-PA-/- arteries. The electric injury model was used to characterize the underlying cellular mechanisms. Topographic analysis of vascular wound healing in electrically injured wild-type and t-PA-/- arteries revealed a similar degree of migration of smooth muscle cells from the noninjured borders into the necrotic center. In contrast, in u-PA-/- and t-PA-/-/u-PA-/- arteries, smooth muscle cells accumulated at the uninjured borders but failed to migrate into the necrotic center. Cultured u-PA-/- but not t-PA-/- smooth muscle cells also failed to migrate in vitro after scrape wounding. Proliferation of smooth muscle cells was not affected by PA deficiency. Reendothelialization after electric injury was similar in all genotypes. In situ analysis revealed markedly elevated u-PA zymographic activity, mRNA, and immunoreactivity in smooth muscle cells, endothelial cells, and leukocytes within 1 week after injury, eg, when cells migrated into the wound. Thus, u-PA plays a significant role in vascular wound healing and arterial neointima formation after injury, most likely by affecting cellular migration.

Fibronectin modulates endothelial response to HIV type 1 Tat

The normal function of the endothelium is impaired in HIV-1 infection. Disturbances of the local cytokines as well as the release of HIV-1 Tat by infected mononuclear cells play a role in endothelial dysfunction. We studied the effects of Tat on the human endothelial ECV cell line. In this system, Tat inhibited cell proliferation only in the presence of fibronectin as a culture substrate, whereas it did not modulate plasminogen activator activity, cell migration, or synthesis of fibronectin. Because amino acids 49-57 contains a nuclear translocation sequence, we also evaluated the potential intracellular role of Tat in tat-transfected ECV cells. tat transfectants showed inhibition of cell growth, unaffected cell migration and plasminogen activator activity, and a significant induction of the expression of fibronectin.

Urokinase and tissue-type plasminogen activator are required for the mitogenic and chemotactic effects of bovine fibroblast growth factor and platelet-derived growth factor-BB for vascular smooth muscle cells

The present study was undertaken to evaluate in vitro the relative importance of tissue-type plasminogen activator (t-PA) and urokinase-type plasminogen activator (u-PA) in the mitogenic and chemotactic potential of bovine fibroblast growth factor (bFGF) and platelet-derived growth factor (PDGF)-BB for smooth muscle cells (SMC). Aortic SMC were isolated from transgenic mice showing single inactivations of the t-PA, u-PA, plasminogen activator inhibitor-1, or urokinase-type plasminogen activator receptor (u-PAR) genes. With regard to serum-induced proliferation, all cell types showed similar responses. However, SMC isolated from t-PA-deficient mice did not proliferate or migrate in response to PDGF, whereas SMC isolated from u-PA-deficient animals appeared to be much less sensitive to bFGF than the cells isolated from the other animals. Supplementation of cells from deficient animals with exogenous murine t-PA or u-PA restored the normal response of the growth factors with regard to both migration and proliferation. The mitogenic and chemotactic responses of bFGF were specifically inhibited in u-PAR-deficient cells or in wild-type SMC, cultured in the presence of antibodies to u-PAR. The role of u-PA and t-PA in bFGF and PDGF-induced growth and migration of SMC was not dependent on plasmin generation and activity as demonstrated by the inactivity of epsilon-aminocaproic acid and aprotinin. A 4-5-fold increase in the steady-state levels of u-PA and t-PA mRNA and proteins were observed after 24 h of incubation of the cell cultures with bFGF and PDGF-BB, respectively. These results therefore indicate that, at least in vitro, t-PA is an important element of the activity of PDGF-BB with regard to the proliferation and migration of SMC whereas u-PA is a key factor in the effect of bFGF on SMC.

Urokinase plasminogen activator induces smooth muscle cell migration: key role of growth factor-like domain

We defined the role of urokinase plasminogen activator (uPA) and its growth factor-like domain (GFD) in stimulating smooth muscle cell (SMC) migration. Recombinant uPA (r-uPA) stimulated migration approximately 3-fold whilst the recombinant uPA mutant containing an altered GFD (r-uPAmut) was ineffective. Both uPA variants bound to the same high affinity receptor in a competitive manner. FGF-2- and PDGF-BB-induced migration was also dependent on uPA, their effects being antagonized by addition of a uPA-neutralizing antibody or the r-uPAmut. Thus r-uPA is chemotactic for SMC and stimulation of cell migration by PDGF-BB and FGF-2 is dependent on uPA. The GFD of uPA is essential for its chemotactic effects.

New nortriterpenoid isolated from anti-rheumatoid arthritic plant, Tripterygium wilfordii, modulates tumor growth and neovascularization

Preparations of Tripterygium wilfordii, "Thunder God vine", have been used in China to treat rheumatoid arthritis. Rheumatoid arthritis, as well as solid tumors, is closely associated with neovascularization. Antiarthritic drugs therefore may modulate tumor growth as well as neovascularization. We found that a compound purified from T. wilfordii, the nortriterpenoid, demethylzeylasteral (TZ-93), inhibited the proliferation of vascular endothelial cells approximately 30 times more effectively than it did for the proliferation of human tumor cells. In in vitro assays using bovine aortic endothelial cells, TZ-93 at non-toxic doses inhibited cell migration, expression of urokinase-type plasminogen activator (uPA) mRNA and uPA activity. Exogenous addition of uPA restored the inhibitory effect of TZ-93 on cell migration. In dorsal air-sac assays in BALB/c mice, the oral administration of 3 mg/kg/day TZ-93 for 5 days partially inhibited, and 30 mg/kg/day almost completely abrogated, the development of capillary networks induced by human hepatoblastoma cells. Similarly, 0.3 mg/kg/day TZ-93 partially inhibited, and 3 or 30 mg/kg/day almost completely blocked, the growth of mouse B16-F10 melanoma cells in a tumor implantation assay. The highest dose of TZ-93 significantly reduced the growth of well-vascularized tumors with volumes of more than 500 mm3. TZ-93 treatment of tumor-bearing mice significantly decreased the density of microvessels in the tumors. We conclude that TZ-93 may be useful in treating highly vascularized and metastatic tumors as well as other angiogenic diseases.

Nitric oxide mediates hyperglycemia-induced defective migration in cultured endothelial cells

PURPOSE

To examine the effects of elevated glucose on the migration and proliferation of vascular endothelial cells in an in vitro wound model and to investigate whether nitric oxide (NO) mediates the effects of elevated glucose.

METHODS

Migration was investigated in monolayers of bovine aortic endothelial cells wounded by scraping and measuring the distance, the number of cells migrating, and the area covered by the migrating cells in the presence of various concentrations of glucose. The effects of NO were evaluated by adding to the cultures NG-monomethyl arginine (NMMA), an inhibitor of NO synthase, or S-nitrosylated penicillamine, which is a slow-release agent of NO. Proliferation was investigated in the presence of various concentrations of serum, glucose, or both.

RESULTS

Elevated glucose levels (16.5 and 27.7 mmol/L) inhibited endothelial cell migration in a dose-dependent manner compared with cells cultured in the presence of 5.5 mmol/L glucose. Inhibition of migration was also observed when wounded mono-layers cultured in 5.5 mmol/L glucose were treated with S-nitrosylated penicillamine, which generates NO. Inhibition of NO synthase by NMMA prevented the inhibition of migration observed in media containing 27.7 mmol/L glucose. Elevated glucose levels did not affect cell proliferation except in the presence of 20% fetal bovine serum.

CONCLUSIONS

An elevated glucose level inhibits endothelial cell migration in an in vitro wound model, and the inhibition appears to be mediated by increased levels of NO.

Adenovirus-mediated gene transfer of basic fibroblast growth factor induces in vitro angiogenesis

To investigate the possibility of adenovirus-mediated gene transfer in the treatment of vascular occlusive diseases, we constructed a replication-deficient recombinant adenovirus vector coding for human basic fibroblast growth factor (bFGF) and examined its effect on the proliferation and differentiation of vascular endothelial cells in vitro. Human umbilical vein endothelial cells (HUVECs) were successfully infected with high efficiency and expressed 18 kD protein which is immunoreactive to anti-bFGF monoclonal antibody. This protein was accumulated mainly in the nuclei of the cells, but was also detected in the culture medium although the complimentary DNA (cDNA) did not contain the classical secreting signal sequence. The proliferation assay of HUVECs infected with bFGF-expressing adenovirus revealed a significant increase in cell number over control. Infection with this virus also enhanced tubular formation of HUVECs on reconstituted basement membrane. Neovascularization and the formation of collateral vessels play important roles in minimizing tissue damage in ischemic disorders. These results imply that the use of bFGF-expressing recombinant adenovirus may be a suitable in vivo gene therapy for ischemic diseases.

Inhibitory effects of hypercholesterolemia and ox-LDL on angiogenesis-like endothelial growth in rabbit aortic explants. Essential role of basic fibroblast growth factor

Hypercholesterolemic (HC) rabbits exhibit suppressed compensatory vascular growth after restriction of arterial supply. However, neovascularization is commonly found in atheromas containing inflammatory cells. We used an in vitro model to determine the effects of hypercholesterolemia on angiogenesis in the absence or presence of inflammatory cells. HC rabbit aortic explants (1 mm2) with or without (n = 90 each) lesion-forming inflammatory cells were cultured in a collagen matrix with serum-free medium. Explant-derived endothelial cell growth was organized into capillary-like microtubes (CLM) that could be videomicroscopically quantified. CLM growth from lesion-free HC explants was significantly reduced to 13 +/- 4% of the value in explants (n = 90) from normocholesterolemic (NC, n = 15) rabbits (P < .001). In contrast, in lesion-containing HC explants, the matrix was invaded by foam cells, and CLM growth was not inhibited. Immunoassayable basic fibroblast growth factor (bFGF, in pg/mL) in the culture medium was significantly lower in lesion-free HC (< 5) than NC explants (11 +/- 2, P < .01) or HC explants with lesions (14 +/- 3). In addition, CLM growth was reduced in NC explants incubated with oxidized LDL (ox-LDL, 50-100 micrograms/mL). Exogenous bFGF (10 ng/mL) reversed the inhibitory effects of hypercholesterolemia and ox-LDL, whereas bFGF-neutralizing antibody (10 micrograms/mL) abolished CLM growth in all groups. In cultured rabbit aortic endothelial cells, ox-LDL reduced DNA synthesis, but this inhibition was reversed by bFGF. We conclude that hypercholesterolemia and ox-LDL inhibit angiogenesis like endothelial growth because of a suppressed availability of endogenous bFGF. Retained responsiveness to exogenous bFGF suggests that inducing bFGF expression at targeted sites may improve collateral growth in hyperlipidemic arterial disease.

Cadmium induces the production of high molecular weight heparan sulfate proteoglycan molecules in cultured vascular endothelial cells

The purpose of the present study is to clarify whether or not cadmium-induced production of heparan sulfate in vascular endothelial cells includes: (1) an increase in the number of heparan sulfate proteoglycan (HSPG) molecules; (2) a formation of longer chains of heparan sulfate; and (3) a binding of more heparan sulfate chains to core proteins. Bovine aortic endothelial cells were cultured and metabolically labeled with [(3)H]glucosamine and [(35)S]sulfate in the presence of cadmium chloride. Radiolabeled HSPGs were separated from more highly charged chondroitin or dermatan sulfate proteoglycans by ion-exchange chromatography and hydrodynamic size of HSPGs was characterized by gel filtration. Heparan sulfate chains were characterized by gel filtration after digestion with either papain or heparitinase. It was found that cadmium increases the incorporation of radioactive precursors into the high molecular weight subclass of HSPGs without a marked change of molecular weight of heparan sulfate chains (approximately 45 kDa). A sodium dodecyl sulfate-polyacrylamide gel electrophoresis of [(35)S]methionine-labeled proteins after heparitinase digestion revealed that the endothelial cells actively produce a HSPG core with a high molecular weight (∼400 kDa), probably a perlecan core and the accumulation was increased by cadmium. HSPGs produced by cadmium-treated endothelial cells enhanced the [(3)H]thymidine incorporation in vascular smooth muscle cells cultured in the presence of basic fibroblast growth factor. It was therefore suggested that vascular endothelial cells after exposure to cadmium produce more perlecan molecules and this alteration may contribute to the antithrombogenic property of vascular wall and the formation of atherosclerosis after exposure to the metal through increase in anticoagulant heparan sulfate chains and stimulation of vascular smooth muscle proliferation, respectively.

Nitric oxide promotes proliferation and plasminogen activator production by coronary venular endothelium through endogenous bFGF

We reported previously that NO is responsible for the angiogenesis produced by endothelium-dependent vasodilating peptides. To investigate the mechanisms by which NO controls angiogenesis, NO was assessed for the ability to affect cell proliferation and upregulation of urokinase-type plasminogen activator (uPA) induced by basic fibroblast growth factor (bFGF) when added exogenously to or when produced endogenously by coronary venular endothelial cells (CVECs). The treatment of the cells with the NO donor sodium nitroprusside (NaNp) induced uPA upregulation and cell proliferation, which were prevented by anti-bFGF antibodies. Similarly, the NO-dependent mitogenic activity of the vasodilating peptide substance P (SP) was blocked by anti-bFGF antibodies, thus implicating endogenous bFGF in the NO-induced response. NaNp and SP induced bFGF expression as measured by Western blot analysis of CVEC extracts and by differential reverse transcriptase-polymerase chain reaction of bFGF mRNA. SP-induced upregulation of bFGF was prevented by the NO synthase inhibitor N omega-monomethyl-L-arginine. We conclude that NO promotes cell proliferation and uPA upregulation in CVECs by inducing endogenous bFGF and that this pathway mediates the angiogenetic response to the vasoactive neuropeptide SP. This signaling paradigm may provide an important link between shear rate, NO, bFGF, and coronary angiogenesis.

FGF2-stimulated release of endogenous FGF1 is associated with reduced apoptosis in retinal pigmented epithelial cells

Both inhibition of endogenous fibroblast growth factor (FGF) synthesis on nondividing lens epithelial cells and inhibition of secreted FGF1 in confluent quiescent retinal pigmented epithelial (RPE) cells induce rapid cell apoptosis (Renaud et al., 1996, J. Biol. Chem., 271, 2801-2811). In addition several studies demonstrate that exogenous FGF2 can promote retinal cell survival in vitro and in vivo. To determine the possible relationship between exogenous FGF2, endogenous FGF1, and cell survival, we examined the protective effect of a single dose of exogenous FGF2 on long-term culture of quiescent RPE cells after serum withdrawal. After 4 days of culture, a dramatic and sustained upregulation of FGF1 protein expression occurs specifically in response to exogenous FGF2. After addition of FGF2 (20 ng/ml), RPE cells express fourfold more FGF1 after Day 7 than after Day 1 of culture. This phenomenon is FGF2 dose-dependent. In contrast, neither serum nor FGF2 have an effect on total endogenous FGF2 expression. In addition, in response to exogenous FGF2, FGF1 is secreted in significant amounts into the extracellular medium at a rate comparable to FGF1 accumulation within the cell. Furthermore, in the absence of serum, significant increase in cell death occurs on Day 6 of culture, whereas addition of exogenous FGF2 induces a twofold decrease of RPE cell apoptosis. In the presence of exogenous FGF2, addition of a specific anti-FGF1 neutralizing antibody induces a rapid apoptosis of RPE cell cultures. Thus, we speculate that exogenous FGF2 may indirectly prolong cell survival by increasing synthesis and secretion of endogenous FGF1 and that endogenous FGF1, directly in response to exogenous FGF2, may function as an autocrine trophic factor in RPE cells.

The inhibitory effect of heparin for vascular smooth muscle cell proliferation or migration is not mediated by u-PA and t-PA

Previous works suggest the interesting possibility of an effect of heparin on vascular smooth muscle cell (SMC) replication and migration via a selective inhibition of the expression of t-PA and u-PA both of which may play major roles during intimal hyperplasia following endothelial injury. The present study was undertaken to evaluate in vitro the effect of heparin on the growth and migration of aortic SMC isolated from transgenic mice showing single inactivations of the t-PA and u-PA genes comparatively to SMC isolated from control mice. With regard to serum-induced proliferation and migration, all cell types showed similar responses. On control cells, heparin inhibited in a dose-dependent manner the expression of both t-PA and u-PA protein and mRNA. Heparin however, similarly affected the mitogenic and chemotactic activity of FCS for SMC isolated from control, t-PA or u-PA-deficient mice therefore showing that heparin inhibits FCS-induced SMC proliferation via mechanism(s) other than single inhibition of t-PA or u-PA expression by smooth muscle cells.

Dynamic distribution of basic fibroblast growth factor during epulis formation: an immunohistochemical study in an enhanced healing process of the gingiva

Basic fibroblast growth factor (bFGF) is thought to play an important role in wound healing. However, its histological localization, both in normal and pathological conditions in the oral mucosa, has not been well documented. We have studied the immunolocalization of bFGF in normal gingiva and gingival epulis specimens corresponding to different organizing stages. In normal gingiva, bFGF was detected in subpopulations of macrophages, mast cells and most endothelial cells in the lamina propria. Granulation tissue in epulides was histopathologically classified into six organizing stages. In stages 1 and 2, a small number of bFGF-positive macrophages was seen at the periphery of ulcer bases. In stages 3 and 4, histologically characterized by prominent capillary proliferation, large numbers of bFGF-positive macrophages and mast cells were located within granulation tissue. A positive reaction for bFGF was also found in some endothelial cells and in myxoedematous stroma that was rich in heparan sulfate proteoglycan. In stages 5 and 6, when fibrosis was accelerated, bFGF-positive macrophages and mast cells decreased in number and were localized only at the periphery of the fibrous tissue. These findings suggest that maximum amounts of bFGF are synthesized and released from some macrophages and mast cells into the extracellular matrix during neovascularization of granulation tissue.

TGF-beta and the endothelium during immune injury

During immune injury, activation of endothelial cells by inflammatory cytokines stimulates leukocyte adhesion to the endothelium, turns the endothelium from an anticoagulant surface to one that is frankly procoagulant, and results in the release of vasoactive mediators and growth factors. Cytokine activation of endothelial cells also results in increased endothelial cell TGF-beta 1 synthesis and enhanced activation of latent TGF-beta, the latter involving a shift of plasmin production from the apical to subendothelial surface. In cytokine-stimulated endothelial cells, TGF-beta hinders leukocyte adhesion and transmigration via inhibition of IL-8 and E-selectin expression. TGF-beta also profoundly diminishes cytokine-stimulated inducible nitric oxide synthase production and instead augments endothelial nitric oxide synthase expression. Thus, some of the TGF-beta actions on endothelium during immune activation can viewed as immunosuppressive. TGF-beta also influences mechanisms of vascular remodeling during the healing phase of immune injury. It stimulates PDGF-B synthesis by endothelial cells, causes bFGF release from subendothelial matrix, and promotes VEGF synthesis by non-endothelial cells. Together these mediators control angiogenesis, a critical component of the vascular repair phenomenon. Further, endothelial cell derived PDGF-B and bFGF influence the proliferation and migration of neighboring cells. Thus, endothelial cells and TGF-beta actions on the endothelium play important roles both during the initial phase of immune injury and during the later remodeling phase.

Oncostatin M induces basic fibroblast growth factor expression in endothelial cells and promotes endothelial cell proliferation, migration and spindle morphology

Oncostatin M (OSM), a pleiotropic cytokine originally isolated from supernatants of the U937 histiocytic lymphoma cell line, has been shown to have regulatory effects on a wide variety of cultured and tumor cells. We investigated the effects of OSM on basic fibroblast growth factor (bFGF) gene expression in bovine arterial endothelial (BAE) cells. Levels of bFGF mRNA transcripts were low in uninduced BAE cells, were maximal at 8 hours of exposure to OSM, and returned to control levels by 24 hours. Induction of bFGF mRNA transcripts by OSM was dose-dependent. Nuclear transcriptional run-on analysis demonstrated that exposure of BAE cells to OSM stimulated bFGF gene transcription. OSM treatment of BAE cells enhanced the synthesis of bFGF protein as determined by ELISA assays. Immunocytochemistry studies demonstrated the presence of low levels of bFGF protein within the cytoplasm in uninduced cells. After stimulation for 8 hours with OSM there was significant staining for bFGF in the cytoplasm. However, 24 hours after exposure to OSM, bFGF antigen was located only within the nuclei. Western blot analysis demonstrated that OSM stimulated predominantly the synthesis of a 22 kDa form of bFGF. In addition, OSM stimulated endothelial cell proliferation and migration as well as acquisition of a spindle shape. Phosphorothioate antisense oligonucleotide directed against bFGF inhibited OSM induced BAE cell proliferation and spindle shape formation but had only a minimal effect on migration. The levels of the 22 kDa form of bFGF were reduced by antisense treatment indicating that OSM induced proliferation and morphology change is likely to be regulated by intracellular bFGF. Our studies suggest that OSM released at sites of vascular injury could stimulate angiogenesis by inducing bFGF synthesis, endothelial cell proliferation and migration.

Lead-induced alteration of heparan sulfate proteoglycans in cultured vascular endothelial cells

We investigated the alterations of heparan sulfate proteoglycans produced by vascular endothelial cells after exposure to lead. Bovine aortic endothelial cells were cultured and metabolically labeled with [3H]glucosamine and [35S]sulfate in the presence of lead chloride at 10 microM. Radiolabeled HSPGs were separated by ion-exchange chromatography and either their hydrodynamic size or the length of heparan sulfate chains were characterized by gel filtration. It was found that lead markedly suppresses the incorporation of the radioactive precursors into HSPGs in the cell layer; the incorporation into chondroitin/dermatan sulfate proteoglycans was decreased by the metal only slightly. The suppression by lead occurred in the low molecular weight subclass of HSPGs rather than the high molecular weight subclass. However, the length of heparan sulfate chains was not changed by the metal. A sodium dodecyl sulfate-polyacrylamide gel electrophoresis of [35S]methionine-labeled proteoglycans after heparitinase digestion showed that there were slightly more HSPG core proteins without a change of the size in lead-treated cell layer. It was, therefore, suggested that vascular endothelial cell layer after exposure to lead has more HSPG core proteins with fewer heparan sulfate chains without a change in length.

Latent transforming growth factor-beta binding protein domains involved in activation and transglutaminase-dependent cross-linking of latent transforming growth factor-beta

Transforming growth factor-beta (TGF-beta) is secreted by many cell types as part of a large latent complex composed of three subunits: TGF-beta, the TGF-beta propeptide, and the latent TGF-beta binding protein (LTBP). To interact with its cell surface receptors, TGF-beta must be released from the latent complex by disrupting noncovalent interactions between mature TGF-beta and its propeptide. Previously, we identified LTBP-1 and transglutaminase, a cross-linking enzyme, as reactants involved in the formation of TGF-beta. In this study, we demonstrate that LTBP-1 and large latent complex are substrates for transglutaminase. Furthermore, we show that the covalent association between LTBP-1 and the extracellular matrix is transglutaminase dependent, as little LTBP-1 is recovered from matrix digests prepared from cultures treated with transglutaminase inhibitors. Three polyclonal antisera to glutathione S-transferase fusion proteins containing amino, middle, or carboxyl regions of LTBP-1S were used to identify domains of LTBP-1 involved in cross-linking and formation of TGF-beta by transglutaminase. Antibodies to the amino and carboxyl regions of LTBP-1S abrogate TGF-beta generation by vascular cell cocultures or macrophages. However, only antibodies to the amino-terminal region of LTBP-1 block transglutaminase-dependent cross-linking of large latent complex or LTBP-1. To further identify transglutaminase-reactive domains within the amino-terminal region of LTBP-1S, mutants of LTBP-1S with deletions of either the amino-terminal 293 (deltaN293) or 441 (deltaN441) amino acids were expressed transiently in CHO cells. Analysis of the LTBP-1S content in matrices of transfected CHO cultures revealed that deltaN293 LTBP-1S was matrix associated via a transglutaminase-dependent reaction, whereas deltaN441 LTBP-1S was not. This suggests that residues 294-441 are critical to the transglutaminase reactivity of LTBP-1S.

Transforming growth factor-beta: vasculogenesis, angiogenesis, and vessel wall integrity

Genetic studies have recently revealed a role for transforming growth factor-beta-1 (TGF-beta 1) and its receptors (TGF-beta Rs I and II as well as endoglin) in embryonic vascular assembly and in the establishment and maintenance of vessel wall integrity. The purpose of this review is threefold: first, to reassess previous studies on TGF-beta and endothelium in the light of these recent findings; second, to describe some of the well-established as well as controversial issues concerning TGF-beta and its regulatory role in angiogenesis; and third, to explore the notion of "context' with respect to TGF-beta and endothelial cell function. Although the focus of this review will be on the endothelium, other vascular wall cells are also likely to be important in the pathogenesis of the vascular lesions revealed by genetic studies.

Lactoferrin as a suppressor of cell migration of gastrointestinal cell lines

The effects of lactoferrin (Lf), an iron-binding glycoprotein, on cell migration were investigated. Lf inhibited the cell migration of three gastrointestinal cell lines (Caco-2 cells, AGS cells, and IEC-18 cells) in vitro. Both iron-saturated (holo) and iron-depleted (apo) Lf showed this inhibitory effect. Chelation of iron in the culture medium by desferrioxamine did not affect the activity of either form of Lf. A pepsin hydrolysate of Lf exhibited effectiveness similar to that of intact Lf. These results demonstrate a novel activity of Lf and suggest a potential role for this molecule in gastrointestinal wound healing, which is independent of its iron-binding capacity.

Endothelial cell mitogenesis induced by LPA: inhibition by thrombospondin-1 and thrombospondin-2

We examined the effects of thrombospondin-1 (TSP1) and thrombospondin-2 (TSP2) on the uptake of tritiated thymidine by bovine aortic endothelial (BAE) cells in response to two growth factors, basic fibroblast growth factor (bFGF) and lysophosphatidic acid (LPA). bFGF and LPA stimulate cell proliferation through distinct receptors that have convergent signaling pathways. The doses of LPA that trigger proliferation of BAE cells, which have not been reported previously, were 1 to 30 micromol/L, as opposed to the 5 to 100 micromol/L concentrations required to stimulate proliferation of human foreskin fibroblasts. Baseline mitogenic activity and activity stimulated by either bFGF or LPA on BAE cells was inhibited by human TSP1 purified from platelets or a recombinant source with a similar dose response. These results demonstrate that the anti-proliferative effect of platelet TSP1 is not caused by contaminants from the stimulated platelet. Recombinant mouse TSP2 inhibited BAE cell proliferation in response to LPA in a dose range similar to that of TSP1. Inasmuch as TSP2 does not activate latent TGFbeta1 (Schultz-Cherry et al., J Biol Chem 1995;270: 7304), these results show that inhibition of angiogenesis by TSPs is not related to control of activation of TGFbeta. Together, these studies suggest that structural motifs common to TSP1 and TSP2 inhibit endothelial cell proliferation. Furthermore, TSPs inhibit cell proliferation stimulated by two growth factor receptors that act through distinct signaling pathways.

Induction of angiogenesis by lidocaine and basic fibroblast growth factor: a model for in vivo retroviral-mediated gene therapy

A strategy of direct, in vivo retroviral-mediated gene therapy targeting capillary endothelial cells must provide an environment of active angiogenesis. Both lidocaine and basic fibroblast growth factor (bFGF) promote angiogenesis, but the angiogenic response invoked by these substances in normal skeletal muscle has not been fully characterized. We sought to characterize these agents' angiogenic effects in anterior tibialis muscles of male Sprague-Dawley rats. An injection of either 1% lidocaine with 1:100,000 epinephrine or alternate-day injections of bFGF (0.025 or 0.25 microgram) with or without heparin were tested (n = 6 muscles/condition). Rats were sacrificed 4, 7, 10, or 12 days later and muscles were evaluated histologically to determine the number of proliferating cells using 5-bromo-2'-deoxycytidine (BrdC) and evaluated for capillary density using Griffonia simplicifolia I (GSI) lectin. At all time points, lidocaine produced at least 20-fold greater capillary density and cellular proliferation than PBS control (P < 0.0001). Injections of high-dosage bFGF produced more than fivefold greater capillary density than control injections at 7 and 10 days (P < 0.001), and more than twofold greater proliferation at 4, 7, and 12 days (P < 0.001). Capillary density returned to control levels 12 days following bFGF administration, whereas it remained well above control levels for 12 days after lidocaine administration. To confirm that lidocaine can be utilized in gene therapy strategies targeting vascular endothelium and skeletal muscle fibers, concentrated pLJ retrovirus containing cDNA for the heat-stable human placental alkaline phosphatase (hpAP) marker gene was infused into the rat hindlimb vasculature 4 days post-lidocaine administration. Rats receiving pLJhpAP retrovirus demonstrated significant hpAP transgene expression in endothelial cells and myocytes 21 days after the lidocaine injection (n = 6 muscles). In contrast, controls receiving pLJhpAP infusion without prior lidocaine administration failed to demonstrate any hpAP transgene expression. Lidocaine treatment evokes a substantially higher proliferative response than bFGF and, importantly, a durable angiogenic response in skeletal muscle. Thus, lidocaine is an ideal agent to induce angiogenesis in preparation for direct in vivo retroviral-mediated gene therapy targeting vascular endothelium.

The biochemistry of cancer dissemination

The progression of a tumor cell from one of benign delimited proliferation to invasive and metastatic growth is the major cause of poor clinical outcome of cancer patients. Recent research has revealed that this complex process requires many components for successful dissemination and growth of the tumor cell at secondary sites. These include angiogenesis, enhanced extracellular matrix degradation via tumor and host-secreted proteases, tumor cell migration, and modulation of tumor cell adhesion. Each individual component is multifaceted and is discussed within this review with respect to historical and recent findings. The identification of components and their interrelationship have yielded new therapeutic targets leading to the development of agents that may prove effective in the treatment of cancer and its metastatic progression.

Fibroblast growth factor 2 in breast cancer: occurrence and prognostic significance

This paper examines the expression of fibroblast growth factor 2 (FGF-2) in the malignant human breast. Semiquantitative reverse transcriptase-polymerase chain reaction (RT-PCR) was used to assess the level of expression of FGF-2 in a series of 51 patients clinically followed up for a median of 84 months (Luqmani et al, 1992). Immunohistochemistry and Western blotting were used to show that the level of FGF-2 in breast tissues correlated with the amount of FGF-2 mRNA. FGF-2 was present in both malignant and non-malignant breast, although less was expressed in malignant tissues as determined by all three methods. Immunohistochemistry on frozen sections of breast tissue showed expression of FGF-2 in myoepithelial and epithelial cells in non-malignant samples and generally lower or undetectable levels of staining in malignant epithelial cells. The results obtained by immunohistochemistry correlated well with RT-PCR data showing similar levels of FGF-2 and FGF-2 mRNA expression in samples. No correlation was found between FGF-2 mRNA expression and T stage, nodal status or oestrogen receptor status. However, Kaplan-Meier survival plots show that higher levels of FGF-2 are associated with improved overall and disease-free survival. We suggest that FGF-2 expression may have value as a prognostic indicator in breast cancer.

Angiogenesis in Endocrine Neoplasms

Angiogenesis promotes the growth of tumors, because it both facilitates oxygenation and nutrient flow, and removes metabolic waste. During the past two decades, as the importance of tumor vascularity became recognized, angiogenesis and the relationship between blood vessels and tumor progression received increasing attention. It was found that isolated tumor tissues failed to expand beyond few millimeters unless vascularized, whereupon vascularization they exhibited a rapid growth. Extensive research focusing on the relationship between tumor proliferation and the formation of new vessels has initially been undertaken to assess the role of angiogenesis in the progression of breast carcinomas. Significant results emerged from these investigations, and similar studies were extended to other tumor types, such as melanomas, cervical and pulmonary carcinomas, and so on. It is of note that angiogenesis as it relates to endocrine tumors has so far been limited to pituitary neoplasms, thyroid carcinomas, and pheochromocytomas. The purpose of the article is to provide a brief review of angiogenesis and to summarize available data regarding its role in the growth off endocrine neoplasms.

Role of fibrin and plasminogen activators in repair-associated angiogenesis: in vitro studies with human endothelial cells

Angiogenesis, the formation of new blood vessels from existing ones, plays a central role in development and in a number of pathological conditions. Tissue repair-associated angiogenesis usually involves cell invasion into a fibrin structure and the presence of inflammatory cells. In this chapter the role of plasminogen activators in the dissolution of fibrin and the invasion of endothelial cells into a fibrin matrix is described. Tissue-type plasminogen activator is stored in endothelial cells and can be released acutely into the vessel lumen upon stimulation of the endothelium to activate fibrinolysis and to prevent fibrin deposition. At the basolateral side of the cell, urokinase-type plasminogen activator (uPA) bound to a specific cellular receptor is involved in the proteolytic modulation of matrix proteins and cell-matrix interaction. The cytokine tumor necrosis factor-alpha (TNF-alpha) cooperates with the angiogenic factors basic fibroblast growth factor (bFGF) and vascular endothelial growth factor (VEGF) in inducing human microvascular endothelial cells in vitro to invade a three dimensional fibrin matrix and to form capillary-like tubular structures. The formation of these capillary-like tubules requires cell-bound uPA activity.

Decreased blood flow rate disrupts endothelial repair in vivo

Both local hemodynamics and endothelial injury have been implicated in vascular disorders including bypass graft failure and atherogenesis, but little is known about the effect of local blood flow conditions on repair of endothelial injury. We decreased blood flow rates and shear stresses in common carotid arteries of rabbits by ligating the ipsilateral external carotid artery. After 24 hours, endothelial cells were less elongated, contained fewer central microfilament bundles, and showed less polarity of the centrosome toward the heart than endothelial cells in unmanipulated carotid arteries. To examine wound repair, we made narrow longitudinal intimal wounds at the time of flow reduction using a nylon monofilament device. In arteries with normal blood flows, endothelial cells at the edge of the wound initially spread and elongated in the direction of the wound. The dense peripheral band of actin was attenuated and central microfilaments became more prominent. Endothelial cells remained in close contact with their neighbors in the monolayer. The centrosome of cells adjacent to the wound was redistributed toward the wound side of the nucleus at 6 and 12 hours. Complete closure occurred by 24 hours, at which time the elongated endothelial cells covering the wound were organized in a herringbone pattern with their downstream ends at the center of the wound. With decreased flow and shear stress, the cells at the wound edge spread less than those in normal vessels at 12 hours after wounding and were randomly oriented and polygonal in shape. Also, re-endothelialization proceeded more slowly and there was a marked reduction of central microfilaments in cells at the wound edge. At 24 hours, the wounds were still open, the endothelial cells covering the central portion of the wound did not maintain intimate contact with their neighbors, and orientation of the centrosome toward the wound was reduced. We hypothesize that loss of cell-cell contact during repair at low flow rates and low shear stress disrupts intercellular communication and results in disruption of cytoskeletal reorganization during repair, thereby slowing the repair process.

Ets-1 regulates angiogenesis by inducing the expression of urokinase-type plasminogen activator and matrix metalloproteinase-1 and the migration of vascular endothelial cells

The coordinate induction of protease activities and cell migration is a principal feature of endothelial cells (ECs) invading the interstitial space in the initial step of angiogenesis. However, the molecular mechanisms of these events are not fully characterized. Ets-1 is a member of the ets gene family of transcription factors, which binds to the Ets binding motif in the cis-acting elements and regulates the expression of certain genes. Four typical angiogenic growth factors, aFGF, bFGF, VEGF, and EGF, induced the expression of ets-1 mRNA in either human umbilical vein endothelial cells (HUVECs), ECV-304 cells (immortalized HUVECs), or human omental microvascular endothelial cells (HOMECs). The expression of ets-1 reached its maximum at 2 hr after factor addition and then decreased to the basal level by 12 hr. For characterization of the role of Ets-1 in angiogenesis, ets-1 antisense and sense oligodeoxynucleotides (ODNs) were constructed. The ets-1 antisense ODN but not sense ODN efficiently blocked the synthesis of Ets-1 protein by human ECs in response to angiogenic growth factors. Moreover, the ets-1 antisense ODN but not sense ODN almost completely abolished the binding of endothelial cell extract to DNA containing the Ets binding motif. The expression of urokinase-type plasminogen activator and matrix metalloproteinase-1 and the migration of ECs in response to growth factors were significantly inhibited by ets-1 antisense ODN but not by sense ODN. Tube formation by HOMECs in type 1 collagen gel stimulated with EGF was abrogated by ets-1 antisense ODN. Finally, the expression of Ets-1 protein in ECs during angiogenesis in vivo was confirmed by an immunohistochemical analysis using a murine angiogenesis model. These results indicate that the induction of ets-1 mRNA is a mutual phenomenon in ECs stimulated with angiogenic growth factors. Ets-1 appears to play an important role in angiogenesis, regulating the expression of proteases and the migration of ECs.

Expression of autocrine motility factor receptor correlates with disease progression in human gastric cancer

Up-regulation of autocrine motility factor receptor (AMF-R) expression has been shown to be associated with invasion and metastasis of experimental tumour systems and human neoplasms. Monoclonal antibodies against AMF-R (gp78) were used to stain 221 primary gastric cancer specimens, and level of expression was examined in relation to pathological stage and prognostic values. In 125 out of 221 (56.6%) patients, gp78 was detected. Expression of gp78 was associated with macroscopic type, lymphatic and venous invasions, and lymph node and peritoneal metastasis. The level of gp78 expression in the cancer specimens was associated with histopathological stage and grade of tumour penetration. Positive gp78 expression was significantly associated with poor prognosis (P < 0.001). This significant relationship remained among patients in stage II and III. The results suggest that gp78 expression could be used as a prognostic marker in gastric cancer patients.

Sex steroids regulate the expression of plasminogen activator inhibitor-1 and its mRNA in fibroblasts derived from uterine endometrium

In order to clarify a role of stromal cells in sex steroidal neovascularization, plasminogen activator inhibitor (PAI)-1 [an inhibitor of tissue-type plasminogen activator (tPA) and urokinase-type plasminogen activator (uPA)] and its messenger ribonucleic acid (mRNA) were analysed in fibroblasts derived from uterine endometrium as a model for endometrial stromal cells under the influence of sex steroids. The determinations were carried out by an enzyme-linked immunosorbent assay (ELISA) and reverse transcription-polymerase chain reaction-Southern blotting, respectively. In the fibroblasts, either estradiol or progestogens (progesterone, medroxy progesterone acetate or 17 alpha-hydroxyprogesterone) induced expressions of PAI-1 and its mRNA, and their combination further increased their expression by approximately twofold. PAI-1 from endometrial stromal cells under the influence of sex steroids might contribute to endometrial neovascularization through its effect on endothelial cells in endometrial vessels.

Angiogenic and inflammatory responses following skeletal muscle injury are altered by immune neutralization of endogenous basic fibroblast growth factor, insulin-like growth factor-1 and transforming growth factor-beta 1

Injured skeletal muscle degeneration comprises early microvascular changes and inflammatory cell infiltration, possibly under the control of several growth factors. We have studied the role of basic fibroblast growth factor (bFGF), insulin-like growth factor-1 (IGF1), and transforming growth factor beta-1 (TGF beta 1), by injecting specific anti-growth factor neutralizing antibodies into mouse extensor digitorum longus muscle at the time of injury (denervation and devascularization). Four days later, at the height of damaged myofiber phagocytosis, we assessed quantitatively revascularization, phagocytic activity, and inflammation. The immune neutralization of bFGF reduced the number of capillaries, macrophages and mast cells, and delayed necrotic myofiber phagocytosis. The immune neutralization of IGF1 or TFG beta 1 promoted muscle revascularization, macrophage infiltration and necrotic myofiber phagocytosis. While IGF1 neutralization reduced the number of mast cells and did not modify that of T-cells or neutrophils, TGF beta 1 neutralization increased the number of all of these cells. This study strongly suggests differing roles for bFGF, IGF1 and TFG beta 1 in angiogenic and inflammatory responses during muscle degeneration, apart from their known effects on the behaviour of myogenic cells.

Expression of basic fibroblast growth factor mRNA in developing choroidal neovascularization

PURPOSE

Basic fibroblast growth factor (bFGF) is an angiogenic peptide that may be important in the pathogenesis of choroidal neovascularization. We attempted to determine the transcription of the bFGF gene during the development of experimentally induced choroidal neovascularization.

METHODS

Rat bFGF cDNA was inserted in the pBluescript to prepare antisense and sense riboprobes. Multiple krypton laser burns were applied to the posterior poles of the eyes of pigmented rats according to a protocol described for producing subretinal neovascularization in these animals. At intervals of up to 4 weeks after photocoagulation, the eyes were removed and cut into thin sections. The sections were subjected to histopathological analysis, cell proliferation study, or in situ hybridization with digoxigenin (DIG)-labeled single-strand riboprobes synthesized from rat bFGF cDNA.

RESULTS

In normal adult rat retinas, bFGF mRNA expression was mainly observed in the ganglion cell layer and the inner nuclear layer. After laser photocoagulation, proliferation of RPE cells, fibroblast-like cells and cells in the choroid in the lesions were observed. Expression of bFGF mRNA was observed in the lesions 3 days to 2 weeks after laser treatment. Signals of bFGF mRNA were detected in the proliferating RPE-like cells, choroidal vascular endothelial cells and fibroblast-like cells, all of which are essential for neovascularization. However, bFGF mRNA expression was no longer detectable in these cells 4 weeks after photocoagulation.

CONCLUSIONS

Our findings indicate that bFGF is normally transcribed in ganglion cells and the inner nuclear cell layer. During the neovascularization that followed laser photocoagulation, bFGF mRNA expression was detected within the laser lesions. It is thus probable that bFGF acts as a mediator in the neovascularization process.

Integrin regulation by endogenous expression of 18-kDa fibroblast growth factor-2

The three high molecular weight (HMW) forms of fibroblast growth factor-2 (FGF-2) have a distinct intracellular localization and differentially affect cell mobility and growth compared with the fourth 18-kDa form. To characterize further the effects of the 18-kDa and HMW forms of FGF-2, we have examined their ability to modulate integrin expression. Transfected NIH 3T3 cells expressing only 18-kDa FGF-2 exhibited increased cell surface levels of alpha5beta1, whereas cells expressing only HMW FGF-2 exhibited cell surface alpha5beta1 levels similar to parental cells. When cells synthesizing 18-kDa FGF-2 were transfected with a cDNA encoding a dominant negative FGF receptor, alpha5beta1 cell surface levels decreased. Immunoprecipitation of biosynthetically labeled cells indicated that expression of 18-kDa FGF-2 increased the biosynthesis and rate of maturation of alpha5. Northern blot analysis showed that 18-kDa FGF-2 increases the level of the alpha5 subunit mRNA but does not affect beta1 subunit transcript levels. Experiments utilizing luciferase reporter gene activity revealed increased alpha5 promoter activity in cells expressing 18-kDa FGF-2 indicating that the enhanced alpha5 transcript level is due to modulation of the transcription rate. Therefore, interaction of 18-kDa FGF-2 with FGF receptors results in changes in alpha5beta1 biosynthesis and processing. In contrast, endogenous expression of HMW FGF-2 does not mediate this effect.

Basic fibroblast growth factor: an autocrine growth factor for epiphyseal growth plate chondrocytes

Basic fibroblast growth factor (bFGF) is a permissive mitogen for cultured chondrocytes and has been localized in the specific zones of the epiphyseal growth plate. In this study, we demonstrate that bFGF present in cartilage originates from within the cellular constituents of this tissue. Utilizing reverse transcription coupled to the polymerase chain reaction (PCR), bFGF mRNA was found in extracts of cartilage tissue. Immunocytochemical studies revealed that bFGF was present intracellularly in freshly isolated proliferative chondrocytes and in the extracellular matrix (ECM) after 24 h of culture. Western blot analysis of protein extracts from isolated proliferative chondrocytes identified a bFGF immunoreactive species with a molecular weight of approximately 18 kDa. In situ hybridization confirmed the presence of bFGF mRNA in freshly isolated proliferative chondrocytes. The bFGF in the ECM seemed to be sequestered and not available for biological activity, since these cells still required exogenous bFGF for cell proliferation. This sequestered bFGF could be released to stimulate cell proliferation when cultures were treated with plasmin, a proteolytic enzyme. These data support the hypothesis that bFGF is synthesized by chondrocytes and functions as an autocrine/paracrine mitogen via its deposition into the ECM with subsequent release from the ECM of cartilage being a critical step in biological activity. In addition, the study provides further evidence that locally produced bFGF plays an important role in normal growth and development of cartilage tissue.

Sex steroids regulate the expression of plasminogen activator inhibitor-1 (PAI-1) and its mRNA in uterine endometrial cancer cell line Ishikawa

To know the effects of sex steroids on the potentials of growth, invasion, and metastasis with neovascularization of endometrial cancer, the expression of plasminogen activator inhibitor (PAI)-1 [an inhibitor of tissue-type plasminogen activator (tPA) and urokinase-type plasminogen activator (uPA)] and its mRNA in well-differentiated uterine endometrial cancer cell line Ishikawa was determined by an enzyme-linked immunosorbent assay and reverse transcription-polymerase chain reaction-Southern blotting (RT-PCR-SB), respectively, under the influence of sex steroids. In Ishikawa cells, either estradiol or progestins (progesterone, medroxyprogesterone acetate, or 17 alpha-hydroxyprogesterone alone) induced the expression of PAI-1 and its mRNA, and those expressions were increased approximately two-fold by both estradiol and progestin administered together. Therefore, sex steroidal induction of PAI-1 might contribute to the inhibition of invasion and metastasis, concomitantly with the inhibition of neovascularization associated with tPA and uPA activities, in well differentiated endometrial cancer.

Role of plasminogen activator inhibitor in the reciprocal regulation of bovine aortic endothelial and smooth muscle cell migration by TGF-beta 1

Vascular endothelial and smooth muscle cells exhibit reciprocal migratory responses after transforming growth factor (TGF)-beta 1 treatment. Endothelial cells exhibit a decreased migratory rate and smooth muscle cells exhibit an increased migratory rate. Previous studies have demonstrated increases in extracellular matrix and integrin synthesis and expression in response to TGF-beta 1. In this report, we illustrate the roles of plasminogen activator inhibitor in modulating the migratory rates in these two cell types. Endothelial cells appear to require a proteolytic phenotype for rapid migration, whereas vascular smooth muscle cells appear to require an anti-proteolytic phenotype. Modulation of proteinase/anti-proteinase activity ratios was accomplished via TGF-beta 1 induction, addition of exogenous plasminogen activator inhibitor, addition of anti-catalytic antibodies directed against urokinase plasminogen activator, overexpression of plasminogen activator inhibitor utilizing stable transfectants, and the use of vitronectin as a substratum. The reciprocal migratory behaviors exhibited by these two vascular cell types in response to TGF-beta 1 is discussed in the context that these two vascular cell types utilize distinct adhesive and signaling pathways in their interactions with extracellular matrix components and responsiveness to proteolytic activity.