Differential expression of vascular endothelial growth factor (vascular permeability factor) forms in rat tissues

Single dose S-ketamine rescues transcriptional dysregulation of Mtor and Nrp2 in the prefrontal cortex of FSL rats 1 hour but not 14 days post dosing

There is a pressing need to identify biological indicators of major depression to help guide proper diagnosis and optimize treatment. Animal models mimicking aspects of depression constitute essential tools for early-stage exploration of relevant pathways. In this study, we used the Flinders Sensitive and Resistant Line (FSL/FRL) to explore central and peripheral transcriptional changes in vascular endothelial growth factor (VEGF) pathway genes and their temporal regulation after a single dose of S-ketamine (15 mg/kg). We found that S-ketamine induced both rapid (1 hour) and sustained (2 and 14 days) antidepressant-like effects in the FSL rats. Analysis of mRNA expression revealed significant strain effects of Vegf, Vegf164, Vegfr-1, Nrp1, Nrp2, Rictor, and Raptor in the prefrontal cortex (PFC) and of Vegf164, GbetaL, and Tsc1 in the hippocampus (HIP), which indicates suppression of VEGF signaling in the FSL rats compared to FRL rats. This notion was further substantiated by reduced expression of Vegf and Mtor in plasma from FSL rats. In the brain, S-ketamine induced transcriptional changes in the acute phase, not the sustained phase. There were significant treatment effects of S-ketamine on Vegfr-2 in both PFC and HIP and on Vegf and Vegfr-1 in HIP. Moreover, we found that S-ketamine specifically restored reduced levels of Nrp2 and Mtor in the PFC of the FSL rats. In conclusion, this study substantiates the use of the FRL/FSL rats to explore the depressive-like behavior at the transcriptional level of the VEGF pathway genes and study their regulation in response to various treatment paradigms.

Altered VEGF Splicing Isoform Balance in Tumor Endothelium Involves Activation of Splicing Factors Srpk1 and Srsf1 by the Wilms' Tumor Suppressor Wt1

Angiogenesis is one hallmark of cancer. Vascular endothelial growth factor (VEGF) is a known inducer of angiogenesis. Many patients benefit from antiangiogenic therapies, which however have limitations. Although VEGF is overexpressed in most tumors, different VEGF isoforms with distinct angiogenic properties are produced through alternative splicing. In podocytes, the Wilms' tumor suppressor 1 (WT1) suppresses the Serine/arginine-rich protein-specific splicing factor kinase (SRPK1), and indirectly Serine/arginine-rich splicing factor 1 (Srsf1) activity, and alters VEGF splicing. We analyzed VEGF isoforms, Wt1, Srpk1, and Srsf1 in normal and tumor endothelium. Wt1, Srpk1, Srsf1, and the angiogenic VEGF164a isoform were highly expressed in tumor endothelium compared to normal lung endothelium. Nuclear expression of Srsf1 was detectable in the endothelium of various tumor types, but not in healthy tissues. Inducible conditional vessel-specific knockout of Wt1 reduced Wt1, Srpk1, and Srsf1 expression in endothelial cells and induced a shift towards the antiangiogenic VEGF120 isoform. Wt1(-KTS) directly binds and activates both the promoters of Srpk1 and Srsf1 in endothelial cells. In conclusion, Wt1 activates Srpk1 and Srsf1 and induces expression of angiogenic VEGF isoforms in tumor endothelium.

Targeting VEGF and Its Receptors for the Treatment of Osteoarthritis and Associated Pain

Increased vascular endothelial growth factor (VEGF) levels are associated with osteoarthritis (OA) progression. Indeed, VEGF appears to be involved in OA-specific pathologies including cartilage degeneration, osteophyte formation, subchondral bone cysts and sclerosis, synovitis, and pain. Moreover, a wide range of studies suggest that inhibition of VEGF signaling reduces OA progression. This review highlights both the potential significance of VEGF in OA pathology and pain, as well as potential benefits of inhibition of VEGF and its receptors as an OA treatment. With the emergence of the clinical use of anti-VEGF therapy outside of OA, both as high-dose systemic treatments and low-dose local treatments, these particular therapies are now more widely understood. Currently, there is no established disease-modifying drug available for patients with OA, which warrants continued study of the inhibition of VEGF signaling in OA, as stand-alone or adjuvant therapy. © 2016 American Society for Bone and Mineral Research.

VEGF189 expression is highly related to adaptation of the plateau pika (Ochotona curzoniae) inhabiting high altitudes

The plateau pika (Ochotona curzonia) has adapted to high-altitude hypoxia during evolution. Higher microvessel density in specific tissues and a blunted hypoxic pulmonary vasoconstriction response are the critical components of this adaptation. VEGF, vascular endothelial growth factor, has proved to be a key regulator of angiogenesis in response to tissue hypoxia and to play an important role in vascular vasodilation. However, the role of VEGF in adaptation to high-altitude hypoxia in the plateau pika remains unknown. In this study, we cloned cDNAs for VEGF165 and VEGF189 and examined their expression in pikas inhabiting altitudes of 3200 and 4750 m. Phylogenetic analysis reveals that pika VEGF165 and VEGF189 are evolutionarily conserved. Real-time PCR analysis demonstrates that VEGF165 and VEGF189 display tissue and altitude-specific expression patterns. Interestingly, we found that the levels of VEGF189 mRNA are significantly higher than those of VEGF165 in the brain and muscle tissues of the pika, which is different from what was previously observed in sea-level mammals. VEGF189 mRNA levels in brain, muscle, and lung of the pika increased with increased habitat altitude, whereas VEGF165 shows less change. Our study suggests an important role for VEGF189 in adaptation to hypoxia by the plateau pika in the high-altitude environment.

Allergic rhinitis and vascular endothelial growth factor

Vascular endothelial growth factor (VEGF) was identified in 1980s as a protein that increases vascular permeability and induces endothelial cell-specific mitosis. VEGF plays an important role in angiogenesis during the embryonic stage and in angiogenesis and in increasing vascular permeability during postnatal life, both physiologically and pathologically. Great progress has been made in studies of VEGF, mainly in the field of oncology, and VEGF-targeted therapy has been successfully used to treat patients with cancer. In research related to chronic inflammation, several reports concerning rheumatoid arthritis or retinopathy and VEGF have been published. In the lower respiratory tract, increased levels of VEGF have been detected in biological samples from patients with asthma. However, VEGF has not been studied in detail in upper-airway diseases, such as rhinosinusitis. This review article focuses on VEGF and allergic rhinitis to advance studies of VEGF in chronic inflammation of the upper respiratory tract. VEGF levels in nasal secretions and nasal lavage fluid were higher in perennial allergic rhinitis than in nonallergic rhinosinusitis, after, rather than before, the antigen provocation test. The major VEGF isoforms were confirmed to be VEGF₁₂₁ and VEGF₁₆₅ in allergic rhinitis. Expression of VEGF mRNA was higher in serous versus mucous acini. In allergic rhinitis, serous acini produced significant quantities of VEGF, which was hypersecreted after antigen provocation. VEGF seems to play an important role in the pathophysiology of allergic rhinitis. Modulation of VEGF function seems to contribute to the successful treatment of conditions with airway inflammation such as allergic rhinitis.

Sildenafil alleviates bronchopulmonary dysplasia in neonatal rats by activating the hypoxia-inducible factor signaling pathway

Bronchopulmonary dysplasia (BPD) is a major cause of morbidity in premature infants receiving oxygen therapy. Currently, sildenafil is being examined clinically to improve pulmonary function in patients with BPD. Based on the pharmacological action of sildenafil, the elevation of cyclic guanosine 3',5'-monophosphate (cGMP) in lung tissue is considered to underlie its beneficial effects, but this mechanism is not understood at the molecular level. Here, we examined the possibility that sildenafil helps the pulmonary system adapt to hyperoxic stress. To induce BPD, fetal rats were exposed to LPS before delivery, and neonates were exposed to hyperoxia, followed by intraperitoneal injections of sildenafil. Alveolarization was impaired in rats exposed to hyperoxia, and alveolarization significantly recovered with sildenafil. An immunohistochemical examination revealed that sildenafil effectively increased vascular distribution in lung tissue. Furthermore, the oxygen sensor hypoxia-inducible factor (HIF)-1/2α and the angiogenic factor vascular endothelial growth factor (VEGF) were highly expressed in the lungs of sildenafil-treated rats. In human small-airway epithelial cells, HIF-1/2α and its downstream genes, including VEGF, were confirmed to be induced by sildenafil at both the protein and mRNA levels. Mechanistically, cGMP in airway cells accumulated after sildenafil treatment because of interfering phosphodiesterase Type 5, and subsequently cGMP activated HIF-mediated hypoxic signaling by stimulating the phosphoinositide 3-kinase (PI3K)-v-akt murine thymoma viral oncogene homolog 1 (AKT)-mammalian target of rapamycin (mTOR) pathway. This study provides a better understanding about the mode of action for sildenafil, and suggests that HIF can be a potential target for treating patients with BPD.

Vascular endothelial growth factor participates in modulating the C6 glioma-induced migration of rat bone marrow-derived mesenchymal stem cells and upregulates their vascular cell adhesion molecule-1 expression

Bone marrow-derived mesenchymal stem cells (BMSCs) have been shown to be able to migrate towards glioma, but the molecular mechanisms responsible for this migratory behavior still require further elucidation. This study aimed to test the role of vascular endothelial growth factor (VEGF) in the C6 glioma-induced migration of BMSCs, evaluate the effect of VEGF on the migratory capacity and vascular cell adhesion molecule-1 (VCAM-1) expression of BMSCs and explore the role of VCAM-1 in the VEGF-induced migration of BMSCs. The results showed that C6 glioma cells significantly increased the migration of BMSCs in vitro, which was partially blocked by a VEGF neutralizing antibody, and 20 ng/ml recombinant rat VEGF(164) incubation enhanced the migration of BMSCs. Moreover, 12 h of 20 ng/ml VEGF(164) incubation upregulated the VCAM-1 expression of BMSCs and the blocking of VCAM-1 reduced the VEGF(164)-induced migration of BMSCs. The data also revealed that LY294002, an inhibitor of phosphoinositide-3-kinase (PI3K), decreased the VEGF-induced migration and VCAM-1 expression of BMSCs. These findings indicate that VEGF participates in mediating the C6 glioma-induced migration of BMSCs by upregulating their VCAM-1 expression, and that PI3K is involved in the signal transduction of VEGF(164)-induced migration and VCAM-1 expression of BMSCs.

The balance of proangiogenic and antiangiogenic VEGFA isoforms regulate follicle development

Vascular endothelial growth factor A (VEGFA) has been extensively studied because of its role in follicular development and is a principal angiogenic factor essential for angiogenesis. Since vascularization of the theca layer increases as follicles progress in size through preantral and antral stages, VEGFA might influence follicle growth via the regulation of angiogenesis. However, VEGFA might also influence follicular development through nonangiogenic mechanisms, since its expression has been localized in nonvascular follicles and cells. Alternative mRNA splicing of eight exons from the VEGFA gene results in the formation of various VEGFA isoforms. Each isoform has unique properties and is identified by the number of amino acids within the mature protein. Proangiogenic isoforms (VEGFA_XXX) are encoded by exon 8a, whereas a sister set of isoforms (VEGFA_XXXB) with antiangiogenic properties is encoded by exon 8b. The antiangiogenic VEGFA_XXXB isoforms comprise the majority of VEGFA expressed in most tissues, whereas expression of the proangiogenic VEGFA isoforms is upregulated in tissues undergoing active angiogenesis. Although proangiogenic and antiangiogenic isoforms can now be distinguished from one another, many studies evaluating VEGFA in ovarian and follicular development up to now have not differentiated proangiogenic VEGFA from antiangiogenic VEGFA. Experiments from our laboratory indicate that proangiogenic VEGFA promotes follicle recruitment and early follicular development and antiangiogenic VEGFA inhibits these processes. The balance of proangiogenic versus antiangiognic VEGFA isoforms is thus of importance during follicle development. Further studies are warranted to elucidate the way that this balance regulates follicular formation and progression.

Optimal dose of plasmid vascular endothelial growth factor for enhancement of angiogenesis in the rat brain ischemia model

Vascular endothelial growth factor (VEGF) administration has recently been assessed as a therapeutic strategy for ischemic diseases including brain ischemia because of its angiogenic effect. However, VEGF also causes detrimental adverse effects by increasing vascular permeability. This study examined whether plasmid human VEGF (phVEGF) administration induced angiogenic effects in the rat brain ischemia model caused by permanent ligation of both common carotid arteries, and investigated the occurrence of adverse effects. Administration of various doses (0-200 microg) of phVEGF in the temporal muscle was followed by encephalo-myo-synangiosis. Thirty days after treatment, the numbers and areas of capillaries per field in the extracted brains were analyzed with the National Institutes of Health Image software program. The maximal angiogenic effect occurred with a 100 microg dose of phVEGF in the numbers and areas of capillaries in the VEGF-treated brains. Histological examination showed no apparent adverse effects in the brain parenchyma even at the highest administration dose (200 microg) of phVEGF. The maximal angiogenic effect at the optimal dose of phVEGF can be considered under the threshold to cause serious adverse effects in the rat brain.

Effect of vascular endothelial growth factor on nasal vascular permeability

OBJECTIVES/HYPOTHESIS

One of the major functions of vascular endothelial growth factor (VEGF) is increasing vascular permeability. We previously reported that VEGF is present in nasal secretions in rhinosinusitis, particularly in allergic rhinitis, and is hyperproduced immediately after antigen provocation. However, its function in nasal mucosa has not yet been investigated. This study was designed to estimate the increased vascular permeability by VEGF in nasal mucosa and to discuss its possible role in allergic rhinitis.

STUDY DESIGN

Prospective animal experiment.

METHODS

Hartley guinea pigs were used. Ethyl carbamate was injected into the abdomen for anesthesia, followed by intravenous injection of Evans blue into the femoral vein. Phosphate buffered saline, histamine, or VEGF was then applied to nasal cavities. Nasal mucosa was harvested after saline reflux from heart with phlebotomy by amputating the abdominal aorta. Tissue samples were soaked in formamide for 12 hours at 63 degrees C to extract dye exudates from nasal mucosa. To analyze vascular permeability, dye was quantified by colorimetry.

RESULTS

VEGF increased vascular permeability in nasal mucosa, and was more than 1 x 10(6) times more potent than histamine on the basis of molar units. Although increased vascular permeability by VEGF was not inhibited by histamine 1 receptor antagonist, it was markedly inhibited by anti-VEGF receptor antibodies.

CONCLUSIONS

VEGF increased vascular permeability to a greater degree than histamine in nasal mucosa via a different pathway. Regulating VEGF may be a new therapeutic option for persistent nasal symptoms in allergic rhinitis.

Identification of an exonic splicing silencer in exon 6A of the human VEGF gene

Background

The different isoforms of vascular endothelial growth factor (VEGF) play diverse roles in vascular growth, structure and function. Alternative splicing of the VEGF gene results in the expression of three abundant isoforms: VEGF121, VEGF165 and VEGF189. The mRNA for VEGF189 contains the alternatively spliced exon 6A whereas the mRNA for VEGF165 lacks this exon. The objective of this study was to identify the cis elements that control utilization of exon 6A. A reporter minigene was constructed (pGFP-E6A) containing the coding sequence for GFP whose translation was dependent on faithful splicing for removal of the VEGF exon 6A. To identify cis-acting splicing elements, sequential deletions were made across exon 6A in the pGFP-E6A plasmid.

Results

A candidate cis-acting exonic splicing silencer (ESS) comprising nucleotides 22-30 of exon 6A sequence was identified corresponding to the a silencer consensus sequence of AAGGGG. The function of this sequence as an ESS was confirmed in vivo both in the context of the reporter minigene as a plasmid and in the context of a longer minigene with VEGF exon 6A in its native context in an adenoviral gene transfer vector. Further mutagenesis studies resulted in the identification of the second G residue of the putative ESS as the most critical for function.

Conclusion

This work establishes the identity of cis sequences that regulate alternative VEGF splicing and dictate the relative expression levels of VEGF isoforms.

Effect of estrogen on the blood supply of pituitary autografts in rats

Estrogens are known to cause pituitary enlargement and lactotroph proliferation. They also modulate pituitary angiogenesis and induce tumor formation. Pituitary grafts, due to the loss of hypothalamic dopamine, also show lactotroph hyperplasia. We investigated the role of estrogen on rat pituitary autograft vascularization by light and transmission electron microscopy, and assessed prolactin (PRL) blood levels, microvessel density (MVD) and cell proliferation using the BrdU labeling index. All adenohypophysial cell types were identified by immunohistochemistry (streptavidin-biotin-peroxidase complex method). The proangiogenic factors, vascular endothelial growth factor (VEGF), its receptor Flk-1, and hypoxia inducible factor-1alpha (HIF-1alpha) were similarly demonstrated. The prevalence of lactotrophs, as well as more intense staining for VEGF, Flk-1 and HIF-1alpha, was noted in those grafts exposed to estrogen, mainly in the area surrounding the central necrotic core. Immunostaining showed Flk-1 expression increased in endothelial cells of the estrogen-exposed grafts as compared with those unexposed. In contrast to the grafts not exposed to estrogen, in the estrogen-exposed grafts, only fenestrated endothelium could be demonstrated, suggesting that estrogen induces fenestration of newly formed capillaries. There was an increase in blood PRL levels in the estrogen-treated groups as compared with controls. Both MVD and BrdU labeling indices were higher in grafts exposed to estrogen, especially after 4 weeks. Our results suggest that estrogen administration not only enhances the expression of proangiogenic factors in the pituitary grafts but also induces their expression at earlier stages, leading to rapid neoformation of purely fenestrated capillaries.

Vascular endothelial growth factor expression in the urethral epithelium of castrated adult female rats treated with tamoxifen

OBJECTIVE

The aim of this study was to evaluate the effects of tamoxifen on vascular endothelial growth factor (VEGF) expression in the urethral epithelium of castrated rats.

MATERIALS AND METHODS

Thirty-six adult, castrated, female Wistar-Hannover rats were randomly divided into two groups: group I (n = 16, control), receiving only propylene glycol, and group II (n = 20, tamoxifen), treated with 250 microg/day of tamoxifen for 30 consecutive days by gavage. On the 31st day, the animals were sacrificed and the urethras were immediately removed, separated into the proximal and distal segments and processed for VEGF immunohistochemistry. The data were analysed using Student's t-test (p < 0.05).

RESULTS

The mean percentage of VEGF expression in the epithelium of the proximal urethra of the animals in groups I and II was 64.47+/-3.70 and 74.69+/-3.03, respectively (p < 0.03), whereas the mean percentage of VEGF expression in the distal urethral epithelium of the animals in groups I and II was 53.49+/-4.64 and 68.57+/-3.67, respectively (p < 0.01).

CONCLUSIONS

Our results indicate that, at the dose and during the time of treatment used, tamoxifen increased VEGF expression in the urethral epithelium of castrated rats.

Vascular endothelial growth factor isoform and receptor expression during compensatory lung growth

BACKGROUND

Vascular endothelial growth factor (VEGF) is required for blood vessel formation during lung growth and repair. Alteration of VEGF isoform expression has been demonstrated in response to fetal tracheal occlusion and in models of lung injury. The purpose of this study was to investigate VEGF expression during compensatory lung growth in the mouse.

METHODS

Under general anesthesia, adult mice underwent left thoracotomy with (n = 5) or without (sham, n = 5) pneumonectomy. The right lungs were harvested at 1, 3, and 7 d after the operation. Lung-to-body weight ratio as well as total DNA and protein content were measured. VEGF protein expression was analyzed by Western blot and ELISA. VEGF isoform expression was evaluated using semi-quantitative PCR followed by Imagequant optical densitometry. Values were compared by Student's t-test and ANOVA using Fisher's protected least significant difference post-hoc test where appropriate.

RESULTS

Compensatory lung growth was observed as measured by increases in right lung-to-body weight ratio and in DNA and protein content. Total VEGF RNA and protein expression did not change after pneumonectomy. However, on post-operative day 1, there was a decrease in the relative percentage of VEGF188 mRNA (P < 0.01), and an increase in the relative percentage of VEGF164 mRNA (P = 0.05). At 3 d postpneumonectomy, low relative VEGF188 expression persisted (P < 0.05), VEGF164 expression normalized, and relative VEGF120 expression increased (P < 0.01). Isoform expression in the pneumonectomy animals was identical to sham animals by the seventh d. There were no differences observed in VEGF receptor expression.

CONCLUSION

During compensatory lung growth, we have observed an early postoperative reversion of VEGF isoform expression to the pattern seen during fetal lung development and in lung injury models.

Vascular endothelial growth factor produced in nasal glands of perennial allergic rhinitis

BACKGROUND

Vascular endothelial growth factor (VEGF), a pleiotropic polypeptide that mediates endothelial cell-specific responses such as induction of angiogenesis and vascular leakage, is hyperproduced in a variety of inflammatory disorders. In asthma, VEGF hyperproduction promotes mucosal edema by enhancing vascular leakage. However, in allergic rhinitis, details of the pathophysiological importance remain unclear. This study was designed to investigate and discuss the pathophysiological significance of VEGF in nasal secretions from perennial allergic rhinitis sufferers.

METHODS

Seven allergic rhinitis patients sensitized with house-dust mites and 12 chronic rhinosinusitis patients were enrolled. Nasal secretion VEGF was quantified and compared between groups. In allergic rhinitis cases, nasal lavage VEGF was estimated before and after the antigen provocation. Nasal gland VEGF was immunohistochemically investigated. VEGF messenger RNA (mRNA) levels in serous and mucous acini were analyzed by laser microdissection and light cycler-polymerase chain reaction.

RESULTS

VEGF levels in nasal secretions and nasal lavage from allergic rhinitis were higher than in nonallergic rhinosinusitis, after rather than before antigen provocation. VEGF mRNA expression was higher in serous versus mucous acini. These results are consistent with the immunohistochemistry results.

CONCLUSION

In allergic rhinitis, there was significant VEGF production in serous acini, which was hypersecreted after antigen provocation. VEGF may play an important role in pathophysiology of allergic rhinitis.

Plasma levels of vascular endothelial growth factor after treatment for cerebral arteriovenous malformations

BACKGROUND AND PURPOSE

The role of abnormal angiogenesis in the formation and progression of cerebral arteriovenous malformations (AVMs) is unclear. Previous studies have demonstrated increased local expression of vascular endothelial growth factor (VEGF) in AVM tissue and increased circulating levels of VEGF in AVM patients. We sought to further investigate the role of VEGF in AVM pathophysiology by examining changes in plasma VEGF levels in patients undergoing treatment for AVMs.

METHODS

Three serial blood samples were obtained from 13 AVM patients undergoing treatment: (1) before any treatment, (2) 24 hours postresection, and (3) 30 days postresection. Plasma VEGF concentrations were measured via commercially available enzyme-linked immunosorbent assay (ELISA). For controls, blood samples were obtained from 29 lumbar laminectomy patients.

RESULTS

The mean plasma VEGF level in AVM patients at baseline was 36.08+/-13.02 pg/mL, significantly lower than that of the control group (80.52+/-14.02 pg/mL, P=0.028). Twenty-four hours postresection, plasma VEGF levels dropped to 20.09+/-4.54 pg/mL, then increased to 66.81+/-26.45 pg/mL 30 days later (P=0.048). The mean plasma VEGF concentration 30 days after resection was no longer significantly different from the control group (P=0.33).

CONCLUSIONS

Plasma VEGF levels in 13 AVM patients were unexpectedly lower than controls, dropped early after AVM resection, then significantly increased 30 days later. These results support the key role of abnormal angiogenesis in AVM pathophysiology and suggest that a disruption in systemic VEGF expression may contribute to the natural history of these lesions.

Inhibition of cyclooxygenase-2 (COX-2) by meloxicam decreases the incidence of ovarian hyperstimulation syndrome in a rat model

OBJECTIVE

To investigate the effects of selective cyclooxygenase-2 (COX-2) inhibition on the ovarian hyperstimulation syndrome (OHSS) in an experimental model.

DESIGN

Controlled laboratory study.

SETTING

University-affiliated fertility center.

ANIMAL(S)

Female Wistar rats.

INTERVENTION(S)

Female Wistar rats (22 days old) were divided into four groups: group 1 (control group; n = 10) received 0.1 mL of intraperitoneal (IP) saline from days 22-26; group 2 (mild-stimulated group; n = 10) received 10 IU of pregnant mare serum gonadotropin (PMSG) on day 24 and 10 IU of hCG 48 hours later (day 26); group 3 (OHSS group; n = 10) was given 10 IU of PMSG for 4 consecutive days from day 22 and 30 IU hCG on the fifth day to induce OHSS; group 4 was treated the same as group 3, but received 2 muL (15 mg/mL) of meloxicam 2 hours before the PMSG injection for 4 consecutive days, and 2 hours before the hCG injection on the fifth day. All groups were killed on day 26.

MAIN OUTCOME MEASURE(S)

Number of antral and luteinized follicles, ovarian weight, semiquantitative vascular endothelial growth factor (VEGF) and COX-2 immunohistochemistry.

RESULT(S)

There were no differences in the ovarian weight between groups 1 and 2. Group 3 showed significantly increased ovarian weight that was suppressed, in group 4, by meloxicam. There was no difference in the number of antral follicles among the four groups. In the mild-stimulated and OHSS groups, the granulosa cells (GC) of preovulatory follicles and the stromal cells showed intense VEGF immunoreactivity. The ovaries from the meloxicam-treated group showed less immunoreactivity than the OHSS group, indicating diminished VEGF expression associated with meloxicam treatment. Group 3 (OHSS group) showed increased COX-2 immunoreactivity that was diminished in the meloxicam-treated group. Meloxicam treatment did not affect the hormone-induced increase in serum E(2) levels seen in OHSS rats.

CONCLUSION(S)

Our results in a rat model suggest that meloxicam has a beneficial effect on OHSS by reducing the increases in ovarian weight and VEGF expression associated with OHSS. These effects may be mediated by the COX-2 inhibitory capacity of meloxicam.

Coordinated vascular endothelial growth factor expression and signaling during skeletal myogenic differentiation

Angiogenesis is largely controlled by hypoxia-driven transcriptional up-regulation and secretion of vascular endothelial growth factor (VEGF) and its binding to the endothelial cell tyrosine receptor kinases, VEGFR1 and VEGFR2. Recent expression analysis suggests that VEGF is expressed in a cell-specific manner in normoxic adult tissue; however, the transcriptional regulation and role of VEGF in these tissues remains fundamentally unknown. In this report we demonstrate that VEGF is coordinately up-regulated during terminal skeletal muscle differentiation. We reveal that this regulation is mediated in part by MyoD homo- and hetero-dimeric transcriptional mechanisms. Serial deletions of the VEGF promoter elucidated a region containing three tandem CANNTG consensus MyoD sites serving as essential sites of direct interaction for MyoD-mediated up-regulation of VEGF transcription. VEGF-null embryonic stem (ES) cells exhibited reduced myogenic differentiation compared with wild-type ES cells, suggesting that VEGF may serve a role in skeletal muscle differentiation. We demonstrate that VEGFR1 and VEGFR2 are expressed at low levels in myogenic precursor cells and are robustly activated upon VEGF stimulation and that their expression is coordinately regulated during skeletal muscle differentiation. VEGF stimulation of differentiating C2C12 cells promoted myotube hypertrophy and increased myogenic differentiation, whereas addition of sFlt1, a VEGF inhibitor, resulted in myotube hypotrophy and inhibited myogenic differentiation. We further provide evidence indicating VEGF-mediated myogenic marker expression, mitogenic activity, migration, and prosurvival functions may contribute to increased myogenesis. These data suggest a novel mechanism whereby VEGF is coordinately regulated as part of the myogenic differentiation program and serves an autocrine function regulating skeletal myogenesis.

Overexpression of vascular endothelial growth factor 189 in breast cancer cells leads to delayed tumor uptake with dilated intratumoral vessels

Vascular endothelial growth factor (VEGF) is essential for breast cancer progression and is a relevant target in anti-angiogenesis. Although VEGF121 and VEGF165, the fully or partially secreted isoforms, respectively, have been the focus of intense studies, the role of the cell-associated VEGF189 isoform is not understood. To clarify the contribution of VEGF189 to human mammary carcinogenesis, we established several clones of MDA-MB-231 cells stably overexpressing VEGF189 (V189) and VEGF165 (V165). V189 and V165 clones increased tumor growth and angiogenesis in vivo. Remarkably, V165 induced the most rapid tumor uptake, whereas V189 increased vasodilation. In vitro overexpression of VEGF165 and VEGF189 increases the proliferation and chemokinesis of these cancer cells. Interestingly, overexpression of VEGF189 increased cell adhesion on fibronectin (1.9-fold) and vitronectin (1.6-fold), as compared to VEGF165, through alpha5beta1 and alphavbeta5 integrins. Using the BIACore system we demonstrated for the first time that VEGF189 binds directly to neuropilin-1, which is strongly expressed in MDA-MB-231 cells. In contrast, VEGF-R2 was not significantly expressed and VEGF-R1 was expressed at low level. Our in vitro results suggest an autocrine effect of VEGF189 on breast cancer cells, probably through neuropilin-1. In conclusion, our data indicate that VEGF189 participates in mammary tumor growth through both angiogenesis and nonangiogenic functions. Whether VEGF189 overexpression is correlated to prognosis in human breast tumors remains to be established.

Spatiotemporal control over growth factor signaling for therapeutic neovascularization

Many of the qualitative roles of growth factors involved in neovascularization have been delineated, but it is unclear yet from an engineering perspective how to use these factors as therapies. We propose that an approach that integrates quantitative spatiotemporal measurements of growth factor signaling using 3-D in vitro and in vivo models, mathematic modeling of factor tissue distribution, and new delivery technologies may provide an opportunity to engineer neovascularization on demand.

VEGF receptor inhibition slows the progression of polycystic kidney disease

Although the receptors for vascular endothelial growth factor (VEGF) exert their effects on vasculogenesis and angiogenesis through receptors located on endothelial cells, recent studies have shown that these receptors are also present on renal tubular epithelial cells. We investigated the role of VEGF on increased tubule cell proliferation in the Han:SPRD heterozygous (Cy/+) rat model of polycystic kidney disease. The levels of VEGF in the kidneys and the serum, and the expression of the two receptors on tubules were increased in Cy/+ rats. These rats were given ribozymes that specifically inhibited VEGFR1 and VEGFR2 mRNA expression. Tubule cell proliferation within the cysts was significantly decreased in the ribozyme-treated animals leading to decreased cystogenesis, blunted renal enlargement, and prevented the loss of renal function. Our studies show that inhibition of VEGF function may be an important therapeutic option to delay the progression of polycystic kidney disease.

Clinical improvement after treatment with VEGF(165) in patients with severe chronic lower limb ischaemia

The present study focuses on the application of a therapeutic strategy in patients with chronic severe lower limb ischaemia using a plasmid vector encoding the vascular endothelial growth factor (phVEGF(165)). It has been shown that VEGF promotes neo-vascularization and blood vessel network formation and thus might have the ability to improve blood-flow at the level of the affected limbs. However, little information is available regarding the necessary level of expression of VEGF and its possible related adverse effects. We have subcloned VEGF ( 165 )isoform into pCMV-Script expression vector (Stratagene) under the control of the CMV promoter. Three patients with chronic ischaemia of the lower limb, considered as not suitable for surgical re-vascularization, received intramuscular injection with 0.5 ml saline solution containing 10(11) copies of VEGF ( 165 ) plasmid. The clinical evolution has been monitored by angiography and estimated by walking time on the rolling carpet (Gardner protocol). Two months after therapy, all three patients showed complete relief of rest pain, improvement of ischaemic ulcer lesions and increased walking distance on the rolling carpet most probably due to appearance of newly formed collateral vessels.

Therapeutic angiogenesis for brain ischemia: a brief review

In the normal mature brain, blood vessel formation is tightly downregulated. However, pathologic processes such as ischemia can induce cerebral vascular regeneration. Angiogenesis is one of the major styles of new vessel formation. In this article, we summarize the major angiogenic factors in the brain, discuss the significant changes of angiogenic factors and endothelial progenitor cells (EPCs) in response to brain ischemia, and finally, review the therapeutic potential of angiogenic factors and EPCs in experimental cerebral ischemia based on the concept of neurovascular unit.

The significance of VEGF-C/VEGFR-2 interaction in the neovascularization and prognosis of nephroblastoma (Wilms' tumour)

AIM

To investigate the immunohistochemical expression of vascular endothelial growth factor (VEGF)-C and VEGFR-2 in nephroblastoma tissue and correlate their presence with the survival rate of children diagnosed with stage III Wilms' tumour.

METHODS AND RESULTS

The material included nephroblastoma tissue obtained from 25 children hospitalized in the Department of Paediatric Oncology, Haematology and Transplantology between 1997 and 2003. VEGF-C and VEGFR-2 expression was evaluated by immunohistochemical assay. VEGF-C was expressed in all cells of the blastemal component and in 30% of tumour cells in the stromal part. It was absent from epithelial elements. VEGFR-2 expression was spread over the surface of numerous stromal cells as well as all the epithelial cells forming dysplastic tubules. The blastemal component of Wilms' tumour was VEGFR-2-negative. VEGF-C-immunopositive stromal cells were situated in the closest proximity to VEGF-C-immunonegative but VEGFR-2-immunoreactive tubules. VEGF-C expression was of prognostic value for both clinical progression (P = 0.0005) and tumour-related death (P = 0.0365).

CONCLUSIONS

VEGF-C expression in Wilms' tumour constitutes a potent unfavourable risk factor and may direct future antiangiogenic treatment strategies. The proximity of VEGF-C and VEGFR-2 in the stromal and epithelial components of nephroblastoma could be the neoplastic equivalent of the binary VEGF-C function observed in epithelial and endothelial morphogenesis.

Localization of vascular response to VEGF is not dependent on heparin binding

The major vascular endothelial growth factor (VEGF) isoforms are splice variants from a single gene that differ in their extent of heparin affinity due to the absence of the heparin binding domain in the smallest isoform (mouse VEGF120, human VEGF121). A long-held assumption that has guided the use of VEGF isoforms clinically has been that their differences in heparin binding dictate their ability to diffuse through tissue, with VEGF121 moving most freely and that the distribution of recombinant VEGF would have therapeutically relevant consequences. To test this assumption, we delivered the genes encoding these isoforms by myoblast-mediated gene transfer, a means of delivering genes to highly localized sites within muscle. Surprisingly, all isoforms induced comparable extremely localized physiological effects. Significantly, irrespective of the isoform delivered, the vessels passing within several micrometers of muscle fibers expressing VEGF displayed sharply delineated changes in morphology. The induction of capillary wrapping around VEGF-producing fibers, and of vascular malformations in the muscle at high levels, did not differ among isoforms. These results indicate that heparin binding is not essential for the localization of VEGF in adult tissue and suggest that the preferential delivery of VEGF121 cDNA for clinical applications may not have a physiological basis.

Vascular endothelial growth factor receptor-2 and low affinity VEGF binding sites on human glomerular endothelial cells: Biological effects and advanced glycosilation end products modulation

Vascular Endothelial Growth Factor (VEGF), binding to its receptor in endothelial cells, seems to modulate the increased blood flow in the early phase of diabetic renal disease. The aim of the study was to evaluate, in a diabetic milieu, the expression, biological function and modulation of VEGF binding sites in human glomerular endothelial cells (GENC). We demonstrated the presence of VEGF binding sites with high (VEGFR-2) and low (heparan sulfate proteoglycans, HSPG) affinity. VEGF165 and VEGF121 working through VEGFR-2 stimulated nitric oxide (NO) production at low doses (0.1-1 nM), whereas only VEGF165 at high doses (10-100 nM) increased thymidine incorporation. 1 nM VEGF165 and VEGF121 induced in GENC a significant peak of inducible NO synthase (iNOS) production and, at a lower level, of endothelial NOS (eNOS). The copresence of VEGF165 with aminoguanidine (iNOS inhibitor) determined an increase of eNOS and a significant increase in thymidine incorporation. Advanced glycation end products (AGEs) working through specific receptors (RAGE) up-regulated the expression of VEGFR-2, decreased the expression of HSPG sites and reduced GENC growth. These results identify in GENC VEGFR-2 as a mediator of iNOS and eNOS release under control of VEGF, whereas HSPG binding sites seem to mediate the weak growth effect. The presence of AGEs, up-regulating the VEGFR-2 and decreasing HSPG sites might participate to the block of glomerular angiogenesis addressing the VEGF effects on glomerular permeability.

Rac1 and RhoA as regulators of endothelial phenotype and barrier function in hypoxia-induced neonatal pulmonary hypertension

Hypoxia is a common cause of persistent pulmonary hypertension in the newborn (PPHN), a condition associated with endothelial dysfunction and abnormal pulmonary vascular remodeling. The GTPase RhoA has been implicated in the pathogenesis of PPHN, but its contribution to endothelial remodeling and function is not known. We studied pulmonary artery endothelial cells (PAECs) taken from piglets with chronic hypoxia-induced pulmonary hypertension and from healthy animals and analyzed the roles of Rho GTPases in the regulation of the endothelial phenotype and function under basal normoxic conditions, acute hypoxia, and reoxygenation. The activities of RhoA, Rac1, and Cdc42 were correlated with changes in the endothelial cytoskeleton, adherens junctions, permeability, ROS production, VEGF levels, and activities of transcription factors hypoxia-inducible factor (HIF)-1alpha and NF-kappaB. Adenoviral gene transfer was used to express dominant-negative GTPases, kinase-dead p21-activated kinase (PAK)-1, and constitutively activated Rac1 in cells. PAECs from pulmonary hypertensive piglets had a stable abnormal phenotype with a sustained reduction in Rac1 activity and an increase in RhoA activity, which correlated with an increase in actin stress fiber formation, increased permeability, and a decrease in VEGF and ROS production. Cells from pulmonary hypertensive animals were still able to respond to acute hypoxia. They also showed high activities of HIF-1alpha and NF-kappaB, likely to result from changes in the activities of Rho GTPases. Activation of Rac1 and its effector PAK-1 as well as inhibition of RhoA restored the abnormal phenotype and permeability of hypertensive PAECs to normal.

Inhibitor of vascular endothelial growth factor receptor tyrosine kinase attenuates cellular proliferation and differentiation to mature neurons in the hippocampal dentate gyrus after transient forebrain ischemia in the adult rat

Neurogenesis in the adult hippocampal dentate gyrus is promoted by transient forebrain ischemia. The mechanism responsible for this ischemia-induced neurogenesis, however, remains to be determined. It has been suggested that there may be a close relationship between neurogenesis and the expression of vascular endothelial growth factor, an angiogenic factor. The purpose of the present study was to examine the relationship between vascular endothelial growth factor and cell proliferation in the dentate gyrus after transient forebrain ischemia. The mRNA expression of vascular endothelial growth factor was increased in the dentate gyrus on day 1 after ischemia. Immunohistochemical analysis on day 9 after ischemia, when a significant increase in cell proliferation was seen, showed that the cerebral vessel space in the subgranular zone of the dentate gyrus had not been affected by the ischemia. Neither were the vascular densities on days 1 and 3 after ischemia altered compared with those of non-operated naïve control rats. Furthermore, the distance from the center of the proliferative cells to the nearest cerebral vessel of ischemic rats was comparable to that of the sham-operated rats. We demonstrated that transient forebrain ischemia-induced cell proliferation and differentiation to mature neurons in the hippocampal dentate gyrus was attenuated by the i.c.v. administration of a vascular endothelial growth factor receptor tyrosine kinase inhibitor. These results suggest that vascular endothelial growth factor receptor at the early period of reperfusion may contribute to neurogenesis rather than to angiogenesis in the hippocampal dentate gyrus.

VEGF regulation of endothelial nitric oxide synthase in glomerular endothelial cells

BACKGROUND

Vascular endothelial growth factor (VEGF) regulation of endothelial nitric oxide synthase (eNOS) and signaling pathways involved have not been well studied in glomerular endothelial cells (GENCs).

METHODS

GENCs grown from tsA58 Immortomice were used. Immunoblotting and in-cell Western blot analysis were employed to assess changes in VEGF receptor signaling pathway and eNOS phosphorylation of ser1177. Immunokinase assay and immunoblotting with phosphospecific antibodies were performed to assess activity of kinases.

RESULTS

VEGF rapidly induced tyrosine phosphorylation of type 1 and type 2 VEGF receptors. Physical association between VEGF-receptor 2 (VEGF-R2) and insulin receptor substrate (IRS-1) and phosphatidylinositol 3'-kinase (PI3K) was induced by VEGF, which augmented PI3K activity in VEGF-R2 immunoprecipitates. VEGF stimulated Akt phosphorylation in a PI3K-dependent manner. VEGF increased eNOS phosphorylation on Ser1177. Activation of eNOS was associated with nitric oxide generation as measured by medium nitrite content. Signaling mechanisms involved in VEGF stimulation of eNOS were explored. VEGF-induced eNOS phosphorylation was abolished by SU1498, a VEGF-R2 inhibitor, LY294002, a PI3K inhibitor, and infection of cells with an adenovirus carrying a dominant negative-mutant of Akt, demonstrating the requirement of the VEGF-R2/IRS-1/PI3K/Akt axis for activation of eNOS. VEGF also activated extracellular signal-regulated protein kinase (ERK) in a time-dependent manner; and VEGF-stimulated eNOS phosphorylation on Ser1177 was prevented by PD098059, an upstream inhibitor of ERK, demonstrating that ERK was involved in VEGF regulation of eNOS. ERK phosphorylation was abolished by LY294002, suggesting ERK was downstream of PI3K in VEGF-treated GENC.

CONCLUSIONS

Our data demonstrate that in GENC, VEGF stimulates VEGF-R2/IRS-1/PI3K/Akt axis to regulate eNOS phosphorylation on Ser1177 in conjunction with the ERK signaling pathway.

Enhanced brain angiogenesis in chronic cerebral hypoperfusion after administration of plasmid human vascular endothelial growth factor in combination with indirect vasoreconstructive surgery

OBJECT

Vascular endothelial growth factor (VEGF) is a secreted mitogen associated with angiogenesis. The conceptual basis for therapeutic angiogenesis after plasmid human VEGF gene (phVEGF) transfer has been established in patients presenting with limb ischemia and myocardial infarction. The authors hypothesized that overexpression of VEGF using a gene transfer method combined with indirect vasoreconstruction might induce effective brain angiogenesis in chronic cerebral hypoperfusion, leading to prevention of ischemic attacks.

METHODS

A chronic cerebral hypoperfusion model induced by permanent ligation of both common carotid arteries in rats was used in this investigation. Seven days after induction of cerebral hypoperfusion, encephalomyosynangiosis (EMS) and phVEGF administration in the temporal muscle were performed. Fourteen days after treatment, the VEGF gene therapy group displayed numbers and areas of capillary vessels in temporal muscles that were 2.2 and 2.5 times greater, respectively, in comparison with the control group. In the brain, the number and area of capillary vessels in the group treated with the VEGF gene were 1.5 and 1.8 times greater, respectively, relative to the control group.

CONCLUSIONS

In rat models of chronic cerebral hypoperfusion, administration of phVEGF combined with indirect vasoreconstructive surgery significantly increased capillary density in the brain. The authors' results indicate that administration of phVEGF may be an effective therapy in patients with chronic cerebral hypoperfusion, such as those with moyamoya disease.

A reassessment of vascular endothelial growth factor in central nervous system pathology

✓ Overexpression of vascular endothelial growth factor (VEGF) is associated with several central nervous system (CNS) diseases and abnormalities, and is often postulated as a causative factor and promising therapeutic target in these settings. The authors' goal was to reassess the contribution of VEGF to the biology and pathology of the CNS.

The authors review the literature relating to the following aspects of VEGF: 1) the biology of VEGF in normal brain; 2) the involvement of VEGF in CNS disorders other than tumors (traumatic and ischemic injuries, arteriovenous malformations, inflammation); and 3) the role of VEGF in brain tumor biology (gliomas and the associated vasogenic edema, and hemangioblastomas).

The authors conclude the following: first, that VEGF overexpression contributes to the phenotype associated with many CNS disorders, but VEGF is a reactive rather than a causative factor in many cases; and second, that use of VEGF as a therapeutic agent or target is complicated by the effects of VEGF not only on the cerebral vasculature, but also on astrocytes, neurons, and inflammatory cells. In many cases, therapeutic interventions targeting the VEGF/VEGF receptor axis are likely to be ineffective or even detrimental. Clinical manipulation of VEGF levels in the CNS must be approached with caution.

Alteration of splicing signals in a genomic/cDNA hybrid VEGF gene to modify the ratio of expressed VEGF isoforms enhances safety of angiogenic gene therapy

Vascular endothelial growth factor (VEGF)-mediated physiological angiogenesis results from the concerted action of three major VEGF isoforms (VEGF121, 165, 189), which arise from alternate splicing. We have previously shown that expression of a mixture of VEGF isoforms via gene transfer is considerably more potent than expression of a single VEGF isoform. To test the hypothesis that different mixtures of VEGF isoforms may offer the same therapeutic benefit with a better safety profile, we compared the efficacy and safety of an adenovirus gene transfer vector expressing the three major VEGF isoforms (AdVEGF-All) in the normal ratio to those of AdVEGF-All6A+, in which the splicing sequences for exon 6A were altered to promote expression of VEGF189 at the expense of VEGF121. Both vectors were equally potent in mediating recovery of hind-limb blood flow following experimental ischemia. By contrast, intravenous administration of AdVEGF-All6A+ yielded enhanced survival and a lower capacity to support tumor growth compared to AdVEGF-All, and intratracheal administration of AdVEGF-All6A+ resulted in less pulmonary edema than that of AdVEGF-All. We conclude that AdVEGF-All and AdVEGF-All6A+ are similar in potency but that AdVEGF-All6A+ is safer. This suggests that AdVEGF-All6A+ may be the preferred candidate for clinical development.

Vascular endothelial growth factor induces branching morphogenesis/tubulogenesis in renal epithelial cells in a neuropilin-dependent fashion

Vascular endothelial growth factor (VEGF) is well characterized for its role in endothelial cell differentiation and vascular tube formation. Alternate splicing of the VEGF gene in mice results in various VEGF-A isoforms, including VEGF-121 and VEGF-165. VEGF-165 is the most abundant isoform in the kidney and has been implicated in glomerulogenesis. However, its role in the tubular epithelium is not known. We demonstrate that VEGF-165 but not VEGF-121 induces single-cell branching morphogenesis and multicellular tubulogenesis in mouse renal tubular epithelial cells and that these morphogenic effects require activation of the phosphatidylinositol 3-kinase (PI 3-K) and, to a lesser degree, the extracellular signal-regulated kinase and protein kinase C signaling pathways. Further, VEGF-165-stimulated sheet migration is dependent only on PI 3-K signaling. These morphogenic effects of VEGF-165 require activation of both VEGF receptor 2 (VEGFR-2) and neuropilin-1 (Nrp-1), since neutralizing antibodies to either of these receptors or the addition of semaphorin 3A (which blocks VEGF-165 binding to Nrp-1) prevents the morphogenic response and the phosphorylation of VEGFR-2 along with the downstream signaling. We thus conclude that in addition to endothelial vasculogenesis, VEGF can induce renal epithelial cell morphogenesis in a Nrp-1-dependent fashion.

Angiogenesis and cerebral neoplasia

Angiogenesis is a fundamental process in reproduction and wound healing. It is a tightly regulated process causing neovascularization. However, if angiogenesis becomes unregulated, it may be responsible for several disease processes such as brain tumour growth and metastasis. An understanding of the factors implicated in angiogenesis and its inhibition is essential if they are to be exploited as possible clinical treatments for brain tumours. Unfortunately, there are multiple factors known to be involved in the regulation of angiogenesis, and hence, the clinical application of any single agent may not be effective. This article summarizes the processes of blood vessel formation in the brain, examines the angiogenic factors that are important in the nervous system and discusses their role in brain tumour development and possible treatment.

Changes in fetal lung distension alter expression of vascular endothelial growth factor and its isoforms in developing rat lung

Vascular endothelial growth factor A (VEGF-A) is essential for normal pulmonary vascular and parenchymal development. Changes in fetal lung distension profoundly affect lung growth and maturation, including vascular development. To define developmental lung expression of VEGF-A and its receptors and investigate effects of changes in fetal lung distension, we studied fetal rats at embryonic day (ED) 16, 19, and 22, postnatal rats at postnatal day (PD) 5, 10, and 21, and adult rats. We used reverse transcriptase PCR to measure mRNA expression for VEGF-A isoforms (VEGF-A(120), (-144), (-164), and (-188)) and VEGF-A receptors, Flt-1 and Flk-1. With advancing development, mRNA content increased only for VEGF-A(188) (p < 0.05) and for Flt-1 (p < 0.02) and Flk-1 (p < 0.005). As a percentage of total VEGF-A mRNA, VEGF-A(188) (15% at ED 16) increased to become the dominant isoform at PD 21 (40%, p < 0.005) and adulthood; in contrast, there were decreases in both VEGF-A(144) (p < 0.05) and (-120) (p < 0.005). VEGF-A protein was expressed in alveolar epithelium (type I and II cells) and interstitium. Increasing fetal lung distension by tracheal occlusion (TO) accelerated the normal maturational pattern of VEGF-A isoforms and increased VEGF-A protein; decreasing fetal lung distension by congenital diaphragmatic hernia (CDH) retarded the normal developmental pattern and decreased VEGF-A protein. Neither TO nor CDH consistently affected Flt-1 or Flk-1 mRNA content. These results show that mechanical factors significantly affect lung VEGF-A expression and suggest that VEGF-A mediates previously described changes in lung vascular and parenchymal development caused by CDH and by TO.

Encapsulated vascular endothelial growth factor—secreting cell grafts have neuroprotective and angiogenic effects on focal cerebral ischemia

Object

The authors evaluated the neuroprotective and angiogenic effects of a continuous and low-dose infusion of vascular endothelial growth factor (VEGF)-165 on cerebral ischemia in rats.

Methods

The authors introduced VEGF complementary (c)DNA into baby hamster kidney (BHK) cells and established a cell line that produces human VEGF165 (BHK-VEGF). The BHK-VEGF cells and BHK cells that had been transfected with an expression vector that did not contain human VEGF165 cDNA (BHK-control) were encapsulated. Both capsules were implanted into rat striata. Six days after capsule implantation, the right middle cerebral artery (MCA) was occluded. Some animals were killed 24 hours after occlusion to measure the volume of the resulting infarct and to perform immunohistochemical studies. Other animals were used for subsequent behavioral studies 1, 7, and 14 days after MCA occlusion.

The encapsulated BHK-VEGF cell grafts significantly reduced the volume of the infarct and the number of apoptotic cells in the penumbral area when compared with the effect of the BHK-control cell capsule. In addition, angiogenesis and gliogenesis significantly increased in the region around the capsule in animals that received BHK-VEGF cell capsules without an increase in focal cerebral blood flow; this did not occur in animals that received the BHK-control cell capsule. In behavioral studies rats that received the BHK-VEGF cell capsule displayed significant recovery while participating in the accelerating rotarod test after stroke.

Conclusions

Continuous intracerebral administration of low-dose VEGF165 through encapsulated grafts of VEGF-producing cells produces neuroprotective and angiogenic effects. These effects improve subsequent motor function.

Specific interaction of VEGF165 with beta-amyloid, and its protective effect on beta-amyloid-induced neurotoxicity

beta-amyloid (Abeta) is a major component of senile plaques that is commonly found in the brain of Alzheimer's disease (AD) patient. In the previous report, we showed that an important angiogenic factor, vascular endothelial growth factor (VEGF) interacts with Abeta and is accumulated in the senile plaques of AD patients' brains. Here we show that Abeta interacts with VEGF(165) isoform, but not with VEGF(121). Abeta binds to the heparin-binding domain (HBD) of VEGF(165) with similar affinity as that of intact VEGF(165). Abeta binds mostly to the C-terminal subdomain of HBD, but with greatly reduced affinity than HBD. Therefore, the full length of HBD appears to be required for maximal binding of Abeta. Although Abeta binds to heparin-binding sequence of VEGF, it does not bind to other heparin-binding growth factors except midkine. Thus it seems that Abeta recognizes unique structural features of VEGF HBD. VEGF(165) prevents aggregation of Abeta through its HBD. We localized the core VEGF binding site of Abeta at around 26-35 region of the peptide. VEGF(165) and HBD protect PC12 cells from the Abeta-induced cytotoxicity. The mechanism of protection appears to be inhibition of both Abeta-induced formation of reactive oxygen species and Abeta aggregation.

Schwann cells upregulate vascular endothelial growth factor secondary to chronic nerve compression injury

To better understand the pathogenesis of chronic nerve compression injuries, we investigated the possibility that Schwann cell production of vascular endothelial growth factor (VEGF) is responsible for the increased vascularity and Schwann cell proliferation associated with chronic nerve injury. In situ hybridization was used to evaluate VEGF mRNA production with immunohistochemistry to further localize the production of VEGF and its receptor proteins in an animal model of chronic nerve compression injury. VEGF mRNA and protein expression increased within Schwann cells as early as 2 weeks after compression and peaked by 1 month with a subsequent marked increase in the number of blood vessels. Thus, chronic nerve compression injury induces Schwann cells to increase VEGF production, which may be responsible for changes in neural vasculature secondary to chronic nerve compression injury. With a better understanding of these nerve injuries, more effective treatments may be developed to help patients with these impairments.

Acceleration of Follicular Development by Administration of Vascular Endothelial Growth Factor in Cycling Female Rats

To address the role of follicular angiogenesis in the determination of ovulatory follicles and the effects of different vascular endothelial growth factor (VEGF) isoforms on follicular angiogenesis and development, mature female rats were treated with an angiogenic inhibitor (TNP-470), and also with VEGF 120 or 164 at different dosages (0.4, 0.8, 4.0 or 8.0 microg/kg body weight) for 3 days during the estrous cycle. Ovarian follicular angiogenesis, the population of large follicles and ovulation were examined. VEGF 120 (0.8 microg/kg) and 164 (8.0 microg/kg) treatments stimulated follicular angiogenesis in the theca interna layer, while TNP-470 treatment showed severe depression of follicular angiogenesis, and completely inhibited ovulation. After administration of VEGF 120 or 164, the number of healthy preovulatory follicles and ovulated oocytes increased significantly, concomitantly with a decrease in the number of atretic preovulatory follicles. The oocytes ovulated had normal fertilizability and developed to term with the same litter size as in the control rats. Our findings suggest that follicular angiogenesis may be a determinant of follicular development during the periovulatory phase, and that VEGF isoforms may play different important roles in regulating follicular angiogenesis.

Adenovirus-mediated transfer of a minigene expressing multiple isoforms of VEGF is more effective at inducing angiogenesis than comparable vectors expressing individual VEGF cDNAs

To assess the hypothesis that angiogenic gene therapy with the genomic form of vascular endothelial growth factor (VEGF) expressing the three major isoforms could be more potent than a vector expressing a single isoform, we designed an adenovirus vector (AdVEGF-All) expressing a VEGF cDNA/genomic hybrid gene. AdVEGF-All expressed all three major isoforms (121, 165, 189) in a 2:2:1 ratio. AdVEGF-All was 100-fold more potent than cDNA vectors expressing VEGF 121, 165, or 189 in restoring blood flow to the ischemic mouse hind limb. Interestingly, a mixture of Ad vectors individually expressing the VEGF 121, 165, and 189 cDNAs was equipotent to an equivalent dose of AdVEGF-All. Thus, a mixture of VEGF isoforms provides a more potent angiogenic response than a single isoform, suggesting that the individual isoforms function synergistically, an observation with important implications for gene and recombinant protein therapy.

Clinical implications of growth factors in flexor tendon wound healing

Recent research has focused on the role of growth factors in flexor tendon wound healing. These basic science reports have described the identification and quantification of various growth factors in in vitro and in vivo models. Although these reports have begun to piece together the cascade of events involved in flexor tendon wound healing, the clinical relevance for the practicing hand surgeon is unclear. Growth factors are cell-secreted proteins that regulate cellular functions. These growth factors are involved in cell differentiation and growth, including the normal processes of development and tissue repair. Several growth factors recently have been identified as playing roles in tendon healing including vascular endothelial growth factor (VEGF), insulin-like growth factor (IGF), platelet-derived growth factor (PDGF), basic fibroblast growth factor (bFGF), and transforming growth factor beta (TGF-beta). In addition, the transcription factor NF-kappaB has been implicated in the signaling pathways of these growth factors. The purpose of this article is to describe what is known about the molecular basis of flexor tendon wound healing, to review the most commonly studied growth factors, and to summarize likely clinical applications of these growth factors to flexor tendon repair.

Regulation of hypoxia-inducible factor 1alpha and induction of vascular endothelial growth factor in a rat neonatal stroke model

Stroke is a devastating condition occurring in at least 1 in 4000 live births in the neonatal period. Since hypoxia-inducible factor (HIF)-1alpha can modulate ischemic injury via induction of target genes that may protect cells against ischemia, and is induced after preconditioning by hypoxia in the neonatal rat brain hypoxia-ischemia model, we evaluated whether HIF-1alpha is induced after focal ischemia-reperfusion, a model for neonatal stroke. We developed an ischemia-reperfusion model in postnatal day 10 (P10) rats by transiently occluding the middle cerebral artery (MCA) for 1.5 h. The MCA territory was reperfused for 0, 4, 8, or 24 h and the expression of HIF-1alpha and its target gene, vascular endothelial growth factor (VEGF), were delineated. HIF-1alpha protein and VEGF protein peaked at 8 h, and declined subsequently at 24 h in injured cortex following 1.5 h of MCA occlusion. Double-immunolabeling indicated that both HIF-1alpha and VEGF are expressed together in neurons with a similar time course of expression. The presence of HIF-1alpha and VEGF after moderate ischemia-reperfusion injury suggests potential avenues to exploit for neuroprotection.

The Role of Vascular Endothelial Growth Factor in the Kidney in Health and Disease

Vascular endothelial growth factor (VEGF) is a potent endothelial cell mitogen, angiogenic factor and enhancer of vascular permeability. Expressed in the epithelial cells of the developing glomerulus and tubular epithelium, VEGF plays an important role in the development and maintenance of the early vasculature of the kidney. Here, we review the available literature regarding the expression and function of VEGF both in the developing and healthy adult kidney. Furthermore, we highlight how VEGF expression is altered in the diseased kidney and how this modulated expression may impact on and reflect underlying functional changes occurring during the disease process. As discussed, many controversial issues remain, particularly concerning the role of VEGF in the diseased kidney. That VEGF has been proposed as a potential future therapeutic target for the management of some renal diseases requires first that the precise role of VEGF in the normal kidney and various renal pathologies be further and more clearly defined.

Vascular Endothelial Growth Factor Expression and Angiogenesis Induced by Chronic Cerebral Hypoperfusion in Rat Brain

OBJECTIVE

In a rat model, we studied the time courses of vascular endothelial growth factor (VEGF) expression and angiogenesis induced by chronic cerebral hypoperfusion in the brain, and we investigated the histological basis of normal-perfusion pressure breakthrough.

METHODS

Twenty-one Sprague-Dawley rats were randomly divided into a control group (n = 3) and a model group assessed at various time points after the creation of a carotid artery-jugular vein fistula (12 h, n = 3; 24 h, n = 3; 72 h, n = 3; 7 d, n = 3; 21 d, n = 3; 90 d, n = 3). The time courses of the expression of VEGF messenger ribonucleic acid (mRNA) and protein in rat brain were analyzed with semiquantitative reverse transcriptase-polymerase chain reaction and Western blot assays, respectively. Immunohistochemical techniques were used to evaluate VEGF protein localization with rabbit polyclonal anti-rat VEGF, VEGF receptor (VEGFR) expression with rabbit polyclonal antibodies to VEGFR-1 and -2, microvascular density with mouse monoclonal anti-rat CD31, and astrocytic reactivity with polyclonal anti-glial fibrillary acidic protein, in cerebral cortical tissue of the right middle cerebral artery territory.

RESULTS

Three alternative splicing forms, i.e., VEGF(188), VEGF(164), and VEGF(120), were observed in cerebral cortical tissue of the right middle cerebral artery territory in semiquantitative reverse transcriptase-polymerase chain reaction analyses. VEGF(164) mRNA was the predominant isoform expressed in rat brain. VEGF(188) mRNA and VEGF(120) mRNA were also detected but at very low levels (not statistically significant). Low levels of VEGF(164) mRNA were observed in the control brains. However, VEGF(164) mRNA levels were significantly increased in the model brains at 24 hours postoperatively, peaked by 7 days, decreased by 21 days, and returned to basal levels by 90 days after fistula formation. VEGF protein expression, as measured in Western blot assays, was also increased in rat brains in the model group from 24 hours to 21 days postoperatively but returned to control levels by 90 days after fistula formation. VEGF immunohistochemical analyses indicated that this increased expression was mostly associated with endothelial cells. Consistent with the VEGF protein expression findings, up-regulation of VEGFR-1 but not VEGFR-2 expression on endothelial cells in the model brains was observed. Microvascular density in the rat brains began to increase significantly 7 days after fistula formation in the model group, as assessed immunohistochemically, and the increase was maintained for 90 days. Although no prominent astrocytic reactivity was observed in the rat brains throughout the experiments, there was an absence of astrocytic foot processes surrounding some cerebral capillaries 90 days after fistula formation in the model group.

CONCLUSION

These results demonstrated that chronic cerebral hypoperfusion could induce sustained up-regulation of VEGF mRNA and protein expression in rat brain, which was correlated with angiogenesis. An absence of corresponding astrocytic reactivity during angiogenesis may be an important factor accounting for structural deficits of the blood-brain barrier and the occurrence of normal-perfusion pressure breakthrough.

Angiogenic factors in the central nervous system

The past decade has seen considerable advances in the understanding of angiogenesis. Blood vessel development and growth in the central nervous system are tightly controlled processes that are regulated by angiogenic factors. Angiogenic factors have been implicated in the pathogenesis of a wide variety of disorders, including primary and metastatic brain tumors, aneurysms, arteriovenous malformations, and cavernous malformations. The potential clinical applications of angiogenesis research include inhibition of angiogenesis to control brain tumors and therapeutic angiogenesis to promote collateral blood vessel formation among patients at risk of ischemia. This article summarizes the processes of blood vessel formation in the brain, examines the angiogenic factors that are prominent in the central nervous system, reviews the clinical use of angiogenesis inhibitors, and identifies areas for future investigation.

Mechanical stress induces production of angiogenic regulators in cultured human gingival and periodontal ligament fibroblasts

BACKGROUND

As periodontal tissues are constantly exposed to mechanical stress during mastication, the relationship between mechanical stimulation and biochemical phenomena has been extensively investigated.

OBJECTIVES

The aim of the present study was to assess the change in the production of angiogenic regulators produced by human gingival fibroblasts (HGF) and periodontal ligament fibroblasts (HPLF), cultured on a flexible substrate, before and after application of cyclic tensile stretching.

MATERIALS AND METHODS

Both cell types were stretched in a Flexercell Strain Unit to 7, 14 and 21% elongation, at a frequency of 12 cycles/min. Medium cultured with HGF or HPLF was examined by enzyme-linked immunosorbent assay (ELISA) for vascular endothelial growth factor (VEGF), Western blotting of pigment epithelium-derived factor (PEDF) and in vitro angiogenesis assay. The residual cells were analyzed by reverse transcription-polymerase chain reaction (RT-PCR) for both VEGF and PEDF mRNA expression.

RESULTS

Stretching increased the VEGF mRNA level and VEGF secretion in both HGF and HPLF. The concentration of VEGF in the conditioned medium of the stretched HPLF was almost the same as that of stretched HGF. In the in vitro angiogenesis assay, the conditioned medium of HPLF after stretching showed a dramatic increase in tube formation. In contrast, stretched HGF did not show enhanced tube formation, despite the increase in VEGF secretion by stretched HGF. The mRNA levels of PEDF, an inhibitor of angiogenesis, were higher in HGF than HPLF. The protein level of PEDF in HGF was also higher than that in HPLF.

CONCLUSION

These findings suggest that under mechanical stress HPLF promotes angiogenesis via expression of VEGF, whereas under the same conditions angiogenesis is not promoted in HGF, due to the expression of PEDF.

Vascular endothelial growth factor induces protein synthesis in renal epithelial cells: a potential role in diabetic nephropathy

BACKGROUND

Vascular endothelial growth factor (VEGF) is an important determinant of ocular complications of diabetes. Its potential role in diabetic renal disease has not been extensively studied.

METHODS

We employed mice with streptozotocin-induced type 1 diabetes and db/db mice with type 2 diabetes to study the regulation of renal VEGF. Studies of VEGF regulation of protein synthesis were performed using proximal tubular epithelial (MCT) cells in culture.

RESULTS

A nearly three-fold increase of VEGF165 expression in the renal cortex was seen, coinciding with renal hypertrophy in mice with either type 1 or type 2 diabetes. VEGF increased de novo protein synthesis and induced significant hypertrophy in MCT cells. VEGF stimulation of protein synthesis was dependent on tyrosine phosphorylation of the type 2 VEGF receptor and phosphatidylinositol 3-kinase (PI 3-kinase) activity. Activity of Akt was increased two- to three-fold by VEGF. Expression of dominant-negative Akt showed that Akt activation was also needed for VEGF-induced protein synthesis and cell hypertrophy. As PI 3-kinase-Akt axis regulates initial events in protein translation, these events were examined in the context of VEGF regulation of protein synthesis. VEGF stimulated eukaryotic initiation factor 4E-binding protein (4E-BP1) phosphorylation, which was dependent on activation of PI 3-kinase and Akt. Stable transfection with 4E-BP1 Thr37,46-Ala37,46 mutant abolished the VEGF-induced de novo protein synthesis and cell hypertrophy.

CONCLUSION

VEGF augments protein synthesis and induces hypertrophy in MCT cells in a PI 3-kinase- and Akt-dependent manner. Phosphorylation of Thr37,46 in 4E-BP1 is required for VEGF-induced protein synthesis and hypertrophy in MCT cells. These data suggest a role for VEGF in the pathogenesis of diabetic renal disease.

Bone tissue engineering: recent advances and promising therapeutic agents

Bone regeneration can be accomplished with growth factors, cells and delivery systems. This review is a summary of these components that may be used for tissue regeneration. Support for the potential therapeutic applications of transcription factors in bone tissue engineering will also be discussed.