Vascular endothelial cell growth factor attenuates actions of transforming growth factor-beta in human endothelial cells

Customizable biomaterials as tools for advanced anti-angiogenic drug discovery

The inhibition of angiogenesis is a critical element of cancer therapy, as cancer vasculature contributes to tumor expansion. While numerous drugs have proven to be effective at disrupting cancer vasculature, patient survival has not significantly improved as a result of anti-angiogenic drug treatment. Emerging evidence suggests that this is due to a combination of unintended side effects resulting from the application of anti-angiogenic compounds, including angiogenic rebound after treatment and the activation of metastasis in the tumor. There is currently a need to better understand the far-reaching effects of anti-angiogenic drug treatments in the context of cancer. Numerous innovations and discoveries in biomaterials design and tissue engineering techniques are providing investigators with tools to develop physiologically relevant vascular models and gain insights into the holistic impact of drug treatments on tumors. This review examines recent advances in the design of pro-angiogenic biomaterials, specifically in controlling integrin-mediated cell adhesion, growth factor signaling, mechanical properties and oxygen tension, as well as the implementation of pro-angiogenic materials into sophisticated co-culture models of cancer vasculature.

TGF-β concentrations and activity are down-regulated in the aqueous humor of patients with neovascular age-related macular degeneration

Controversy still exists regarding the role of the TGF-β in neovascular age-related macular degeneration (nAMD), a major cause of severe visual loss in the elderly in developed countries. Here, we measured the concentrations of active TGF-β1, TGF-β2, and TGF-β3 by ELISA in the aqueous humor of 20 patients affected by nAMD, who received 3 consecutive monthly intravitreal injections of anti-VEGF-A antibody. Samples were collected at baseline (before the first injection), month 1 (before the second injection), and month 2 (before the third injection). The same samples were used in a luciferase-based reporter assay to test the TGF-β pathway activation. Active TGF-β1 concentrations in the aqueous humor were below the minimum detectable dose. Active TGF-β2 concentrations were significantly lower at baseline and at month 1, compared to controls. No significant differences in active TGF-β3 concentration were found among the sample groups. Moreover, TGF-β pathway activation was significantly lower at baseline compared to controls. Our data corroborate an anti-angiogenic role for TGF-β2 in nAMD. This should be considered from the perspective of a therapy using TGF-β inhibitors.

The roles of vascular endothelial growth factor in bone repair and regeneration

Vascular endothelial growth factor-A (VEGF) is one of the most important growth factors for regulation of vascular development and angiogenesis. Since bone is a highly vascularized organ and angiogenesis plays an important role in osteogenesis, VEGF also influences skeletal development and postnatal bone repair. Compromised bone repair and regeneration in many patients can be attributed to impaired blood supply; thus, modulation of VEGF levels in bones represents a potential strategy for treating compromised bone repair and improving bone regeneration. This review (i) summarizes the roles of VEGF at different stages of bone repair, including the phases of inflammation, endochondral ossification, intramembranous ossification during callus formation and bone remodeling; (ii) discusses different mechanisms underlying the effects of VEGF on osteoblast function, including paracrine, autocrine and intracrine signaling during bone repair; (iii) summarizes the role of VEGF in the bone regenerative procedure, distraction osteogenesis; and (iv) reviews evidence for the effects of VEGF in the context of repair and regeneration techniques involving the use of scaffolds, skeletal stem cells and growth factors.

Pathways Regulating Spheroid Formation of Human Follicular Thyroid Cancer Cells under Simulated Microgravity Conditions: A Genetic Approach

Microgravity induces three-dimensional (3D) growth in numerous cell types. Despite substantial efforts to clarify the underlying mechanisms for spheroid formation, the precise molecular pathways are still not known. The principal aim of this paper is to compare static 1g-control cells with spheroid forming (MCS) and spheroid non-forming (AD) thyroid cancer cells cultured in the same flask under simulated microgravity conditions. We investigated the morphology and gene expression patterns in human follicular thyroid cancer cells (UCLA RO82-W-1 cell line) after a 24 h-exposure on the Random Positioning Machine (RPM) and focused on 3D growth signaling processes. After 24 h, spheroid formation was observed in RPM-cultures together with alterations in the F-actin cytoskeleton. qPCR indicated more changes in gene expression in MCS than in AD cells. Of the 24 genes analyzed VEGFA, VEGFD, MSN, and MMP3 were upregulated in MCS compared to 1g-controls, whereas ACTB, ACTA2, KRT8, TUBB, EZR, RDX, PRKCA, CAV1, MMP9, PAI1, CTGF, MCP1 were downregulated. A pathway analysis revealed that the upregulated genes code for proteins, which promote 3D growth (angiogenesis) and prevent excessive accumulation of extracellular proteins, while genes coding for structural proteins are downregulated. Pathways regulating the strength/rigidity of cytoskeletal proteins, the amount of extracellular proteins, and 3D growth may be involved in MCS formation.

Osteoblast-derived VEGF regulates osteoblast differentiation and bone formation during bone repair

Osteoblast-derived VEGF is important for bone development and postnatal bone homeostasis. Previous studies have demonstrated that VEGF affects bone repair and regeneration; however, the cellular mechanisms by which it works are not fully understood. In this study, we investigated the functions of osteoblast-derived VEGF in healing of a bone defect. The results indicate that osteoblast-derived VEGF plays critical roles at several stages in the repair process. Using transgenic mice with osteoblast-specific deletion of Vegfa, we demonstrated that VEGF promoted macrophage recruitment and angiogenic responses in the inflammation phase, and optimal levels of VEGF were required for coupling of angiogenesis and osteogenesis in areas where repair occurs by intramembranous ossification. VEGF likely functions as a paracrine factor in this process because deletion of Vegfr2 in osteoblastic lineage cells enhanced osteoblastic maturation and mineralization. Furthermore, osteoblast- and hypertrophic chondrocyte-derived VEGF stimulated recruitment of blood vessels and osteoclasts and promoted cartilage resorption at the repair site during the periosteal endochondral ossification stage. Finally, osteoblast-derived VEGF stimulated osteoclast formation in the final remodeling phase of the repair process. These findings provide a basis for clinical strategies to improve bone regeneration and treat defects in bone healing.

Immunoexpression of TGF-β/Smad and VEGF-A proteins in serum and BAL fluid of sarcoidosis patients

Background

The chronic course of pulmonary sarcoidosis can lead to lung dysfunction due to fibrosis, in which the signalling pathways TGF-β/Smad and VEGF-A may play a key role.

Methods

We evaluated immunoexpression of TGF-β₁, Smad2, 3, and 7, and VEGF-A in serum and bronchoalveolar lavage (BAL) fluid of patients (n = 57) classified according to the presence of lung parenchymal involvement (radiological stage I vs. II-III), acute vs. insidious onset, lung function test (LFT) results, calcium metabolism parameters, percentage of BAL lymphocytes (BAL-L%), BAL CD4⁺/CD8⁺ ratio, age, and gender. Immunoexpression analysis of proteins was performed by ELISA.

Results

The immunoexpression of all studied proteins were higher in serum than in BAL fluid of patients (p >0.05). The serum levels of TGF-β₁ (p = 0.03), Smad2 (p = 0.01), and VEGF-A (p = 0.0002) were significantly higher in sarcoidosis patients compared to healthy controls. There were no differences within the sarcoidosis group between patients with vs. without parenchymal involvement, acute vs. insidious onset, or patients with normal vs. abnormal spirometry results. In patients with abnormal spirometry results a negative correlation was found between forced vital capacity (FVC) % predicted value and TGF-β₁ immunoexpression in BAL fluid, and positive correlations were observed between the intensity of lung parenchymal changes estimated by high-resolution computed tomography (HRCT scores) and Smad 2 level in serum.

Conclusions

TGF-β/Smad signalling pathway and VEGF-A participate in the pathogenesis of sarcoidosis. BAL TGF-β₁, and Smad 2 in serum seem to be promising biomarkers with negative prognostic value, but further studies are required to confirmed our observations.

Inhibition of transforming growth factor beta/SMAD signal by MiR-155 is involved in arsenic trioxide-induced anti-angiogenesis in prostate cancer

Prostate cancer is the most common cause of cancer-related deaths in men. Current practices for treatment of prostate cancer are less than satisfactory because of metastasis and recurrence, which are primarily attributed to angiogenesis. Hence, anti-angiogenesis treatment is becoming a promising new approach for prostate cancer therapy. In addition to treating acute promyelocytic leukemia, arsenic trioxide (As₂O₃) suppresses other solid tumors, including prostate cancer. However, the effects of As₂O₃ on angiogenesis in prostate cancer cells, and the underlying molecular mechanisms remain unclear. In the present study, As₂O₃ attenuated angiogenic ability through microRNA-155 (miR-155)-mediated inhibition of transforming growth factor beta (TGF-β)/SMAD signal pathway in human prostate cancer PC-3 and LNCaP cells in vitro and in vivo. Briefly, As₂O₃ inhibited the activations/expressions of both TGFβ-induced and endogenous SMAD2/3. Furthermore, As₂O₃ improved the expression of miR-155 via DNA-demethylation. MiR-155, which targeted the SMAD2-3′UTR, decreased the expression and function of SMAD2. Knockdown of miR-155 abolished the As₂O₃-induced inhibitions of the TGF-β/SMAD2 signaling, the vascular endothelial growth factor secretion and angiogenesis. Through understanding a novel mechanism whereby As₂O₃ inhibits angiogenic potential of prostate cancer cells, our study would help in the development of As₂O₃ as a potential chemopreventive agent when used alone or in combination with other current anticancer drugs.

Peritoneal cytokines and adhesion formation in endometriosis: an inverse association with vascular endothelial growth factor concentration

OBJECTIVE

To evaluate inflammatory/angiogenic cytokines-interleukin-1β (IL-1β), IL-6, IL-8, IL-12, interferon-γ (IFN-γ), tumor necrosis factor (TNF), and vascular endothelial growth factor A (VEGF-A)-in the peritoneal fluid of patients with endometriosis in relation to the occurrence and severity of pelvic adhesions and in control women without pelvic pathology.

DESIGN

Case-control study.

SETTING

University research institution and hospital.

PATIENT(S)

Sixty-five women with laparoscopically and histopathologically confirmed endometriosis, including 40 women with pelvic adhesions, and 37 control women without pelvic pathology.

INTERVENTION(S)

Peritoneal fluid aspirated during routine diagnostic laparoscopic examination.

MAIN OUTCOME MEASURE(S)

Cytokines evaluated in the peritoneal fluid via specific enzyme-linked immunosorbent assays.

RESULT(S)

Endometriosis and the revised American Fertility Society score of this disease were associated with statistically significantly increased levels of peritoneal IL-6 and IL-8 whereas the incidence and score of endometriosis-related pelvic adhesions were negatively associated with increased levels of VEGF-A. Notably, the concentration of VEGF-A predicted adhesion development and severity after adjustment for endometriosis severity. The adhesion score also correlated with increased levels of IL-6; however, after adjustment for endometriosis severity, the effect of this cytokine was no longer statistically significant.

CONCLUSION(S)

Increased levels of VEGF-A may be associated with a decreased rate of pelvic adhesion formation in the course of endometriosis.

Angiogenic activity of dentin matrix components

Angiogenesis is key to both the development and regeneration of the dentin-pulp complex.

OBJECTIVE

We hypothesized that proangiogenic signaling molecules sequestered in dentin matrix can be solubilised to induce angiogenic events.

METHODS

Matrix components were extracted from powdered sound human dentin with EDTA and their dose-dependent (0.0001-5 mg/mL) effects examined in endothelial cells in an in vitro angiogenic tube formation assay, proliferation assay, and transcriptional regulation of the VEGF and VEGF-R2 genes.

RESULTS

Lower concentrations of dentin matrix components were found to show proangiogenic activity, whereas higher concentrations suppressed angiogenic activity.

CONCLUSION

This study highlights that the release of dentin matrix components after dental injury can contribute to the angiogenic events that support pulp regeneration.

Specific local cardiovascular changes of Nepsilon-(carboxymethyl)lysine, vascular endothelial growth factor, and Smad2 in the developing embryos coincide with maternal diabetes-induced congenital heart defects

OBJECTIVE

Embryos exposed to a diabetic environment in utero have an increased risk to develop congenital heart malformations. The mechanism behind the teratogenicity of diabetes still remains enigmatic. Detrimental effects of glycation products in diabetic patients have been well documented. We therefore studied a possible link between glycation products and the development of congenital cardiovascular malformations. Furthermore, we investigated other possible mechanisms involved in this pathogenesis: alterations in the levels of vascular endothelial growth factor (VEGF) or phosphorylated Smad2 (the latter can be induced by both glycation products and VEGF).

RESEARCH DESIGN AND METHODS

We examined the temporal spatial patterning of the glycation products Nepsilon(carboxymethyl)lysine (CML) and methylglyoxal (MG) adducts, VEGF expression, and phosphorylated Smad2 during cardiovascular development in embryos from normal and diabetic rats.

RESULTS

Maternal diabetes increased the CML accumulation in the areas susceptible to diabetes-induced congenital heart disease, including the outflow tract of the heart and the aortic arch. No MG adducts could be detected, suggesting that CML is more likely to be indicative for increased oxidative stress than for glycation. An increase of CML in the outflow tract of the heart was accompanied by an increase in phosphorylated Smad2, unrelated to VEGF. VEGF showed a time-specific decrease in the outflow tract of embryos from diabetic dams.

CONCLUSIONS

From our results, we can conclude that maternal diabetes results in transient and localized alterations in CML, VEGF expression, and Smad2 phosphorylation overlapping with those regions of the developing heart that are most sensitive to diabetes-induced congenital heart disease.

Alpha2-antiplasmin is involved in the production of transforming growth factor beta1 and fibrosis

BACKGROUND

Fibrotic disease occurs in most tissues. Transforming growth factor (TGF)-beta is the major inducer of fibrosis. The fibrinolytic system is considered to play an important role in the degradation of extracellular matrices. However, the detailed mechanism of how this system affects fibrosis remains unclear.

METHODS AND RESULTS

We examined experimental fibrosis in mice with a deficiency of alpha(2)-antiplasmin (alpha2AP), which is a potent and specific plasmin inhibitor. We found that the lack of alpha2AP attenuated bleomycin-induced TGF-beta(1) synthesis and fibrosis. In addition, the production of TGF-beta(1) from the explanted fibroblasts of alpha2AP(-/-) mice decreased dramatically as compared to that in wild-type mice. Moreover, we found that alpha2AP specifically induces the production of TGF-beta(1) in fibroblasts.

CONCLUSION

The lack of alpha2AP attenuated TGF-beta(1) synthesis, thereby resulting in attenuated fibrosis. This is the first report to describe the crucial role that alpha2AP plays in TGF-beta(1) synthesis during the process of fibrosis. Our results provide new insights into the role of alpha2AP in fibrosis.

D-glucose stimulation ofL-arginine transport and nitric oxide synthesis results from activation of mitogen-activated protein kinases p42/44 and Smad2 requiring functional type II TGF-β receptors in human umbilical vein endothelium

Elevated extracellular D-glucose increases transforming growth factor beta1 (TGF-beta1) release from human umbilical vein endothelium (HUVEC). TGF-beta1, via TGF-beta receptors I (TbetaRI) and TbetaRII, activates Smad2 and mitogen-activated protein kinases p44 and p42 (p42/44(mapk)). We studied whether D-glucose-stimulation of L-arginine transport and nitric oxide synthesis involves TGF-beta1 in primary cultures of HUVEC. TGF-beta1 release was higher ( approximately 1.6-fold) in 25 mM (high) compared with 5 mM (normal) D-glucose. TGF-beta1 increases L-arginine transport (half maximal effect approximately 1.6 ng/ml) in normal D-glucose, but did not alter high D-glucose-increased L-arginine transport. TGF-beta1 and high D-glucose increased hCAT-1 mRNA expression ( approximately 8-fold) and maximal transport velocity (V(max)), L-[(3)H]citrulline formation from L-[(3)H]arginine (index of NO synthesis) and endothelial NO synthase (eNOS) protein abundance, but did not alter eNOS phosphorylation. TGF-beta1 and high D-glucose increased p42/44(mapk) and Smad2 phosphorylation, an effect blocked by PD-98059 (MEK1/2 inhibitor). However, TGF-beta1 and high D-glucose were ineffective in cells expressing a truncated, negative dominant TbetaRII. High D-glucose increases L-arginine transport and eNOS expression following TbetaRII activation by TGF-beta1 involving p42/44(mapk) and Smad2 in HUVEC. Thus, TGF-beta1 could play a crucial role under conditions of hyperglycemia, such as gestational diabetes mellitus, which is associated with fetal endothelial dysfunction.

Mechanisms underlying TGF-beta1-induced expression of VEGF and Flk-1 in mouse macrophages and their implications for angiogenesis

TGF-beta induces vascular endothelial growth factor (VEGF), a potent angiogenic factor, at the transcriptional and protein levels in mouse macrophages. VEGF secretion in response to TGF-beta1 is enhanced by hypoxia and by overexpression of Smad3/4 and hypoxia-inducible factor-1alpha/beta (HIF-1alpha/beta). To examine the transcriptional regulation of VEGF by TGF-beta1, we constructed mouse reporters driven by the VEGF promoter. Overexpression of HIF-1alpha/beta or Smad3/4 caused a slight increase of VEGF promoter activity in the presence of TGF-beta1, whereas cotransfection of HIF-1alpha/beta and Smad3/4 had a marked effect. Smad2 was without effect on this promoter activity, whereas Smad7 markedly reduced it. Analysis of mutant promoters revealed that the one putative HIF-1 and two Smad-binding elements were critical for TGF-beta1-induced VEGF promoter activity. The relevance of these elements was confirmed by chromatin immunoprecipitation assay. p300, which has histone acetyltransferase activity, augmented transcriptional activity in response to HIF-1alpha/beta and Smad3/4, and E1A, an inhibitor of p300, inhibited it. TGF-beta1 also increased the expression of fetal liver kinase-1 (Flk-1), a major VEGF receptor, and TGF-beta1 and VEGF stimulated pro-matrix metalloproteinase 9 (MMP-9) and active-MMP-9 expression, respectively. The results from the present study indicate that TGF-beta1 can activate mouse macrophages to express angiogenic mediators such as VEGF, MMP-9, and Flk-1.

FAK-dependent regulation of myofibroblast differentiation

Fibroblasts and myofibroblasts both participate in wound healing. Transforming growth factor beta (TGFbeta) induces fibroblasts to differentiate into myofibroblasts, whereas fibroblast growth factor and heparin (FGF/h) induce myofibroblasts to "de-differentiate" into fibroblasts. TGFbeta induces expression of smooth muscle alpha actin (SMalphaA) and incorporation into in stress fibers, a phenotype of differentiated myofibroblasts. Additionally, TGFbeta induces the expression of fibronectin and fibronectin integrins. Fibronectin-generated signals contribute to the TGFbeta-mediated myofibroblast differentiation. Because fibronectin signals are transmitted through focal adhesion kinase (FAK), it was predicted that FAK would be essential to TGFbeta-mediated myofibroblast differentiation. To determine whether the FAK signaling pathway is required for myofibroblast differentiation, we used two approaches to decrease FAK in mouse embryo fibroblasts (MEFs): 1) FAK +/+ MEFs, in which FAK protein expression was greatly decreased by short hairpin RNA (shRNA), and 2) FAK -/- MEFs, which lack FAK. In both cases, the majority of cells were myofibroblasts, expressing SMalphaA in stress fibers even after treatment with FGF/h. Furthermore, both the surface expression of FGFRs and FGF signaling were greatly reduced in FAK -/- [corrected]MEFs. We conclude that FAK does not contribute to TGFbeta-dependent myofibroblast differentiation. Instead, FAK was necessary for FGF/h signaling in down-regulating expression of SMalphaA, which is synonymous with myofibroblast differentiation. FAK activation could contribute to regulating myofibroblast differentiation, thereby ameliorating fibrosis.

Expression and regulation of latent TGF-beta binding protein-1 transcripts and their splice variants in human glomerular endothelial cells

Latent transforming growth factor (TGF)-beta-binding protein (LTBP) is required for the assembly, secretion, matrix association, and activation of latent TGF-beta complex. To elucidate the cell specific expression of the genes of LTBP-1 and their splice variants and the factors that regulate the gene expression, we cultured primary human glomerular endothelial cells (HGEC) under different conditions. Basal expression of LTBP-1 mRNA was suppressed in HGEC compared to WI-38 human embryonic lung fibroblasts. High glucose, H(2)O(2), and TGF-beta1 upregulated and vascular endothelial growth factor (VEGF) further downregulated LTBP-1 mRNA in HGEC. RT-PCR with a primer set for LTBP-1S produced many clones but no clone was gained with a primer set for LTBP-1L. Of 12 clones selected randomly, Sca I mapping and DNA sequencing revealed that only one was LTBP-1S and all the others were LTBP-1Sdelta53. TGF-beta1, but not high glucose, H(2)O(2) or VEGF, tended to increase LTBP-1Sdelta53 mRNA. In conclusion, HGEC express LTBP-1 mRNA which is suppressed at basal state but upregulated by high glucose, H(2)O(2), and TGF-beta1 and downregulated by VEGF. Major splice variant of LTBP-1 in HGEC was LTBP-1S 53. Modification of LTBP-1S 53 gene in HGEC may abrogate fibrotic action of TGF-beta1 but this requires confirmation.