VEGF-DdeltaNdeltaC mediated angiogenesis in skeletal muscles of diabetic WHHL rabbits

The Role of the VEGF Family in Coronary Heart Disease

The vascular endothelial growth factor (VEGF) family, the regulator of blood and lymphatic vessels, is mostly investigated in the tumor and ophthalmic field. However, the functions it enjoys can also interfere with the development of atherosclerosis (AS) and further diseases like coronary heart disease (CHD). The source, regulating mechanisms including upregulation and downregulation, target cells/tissues, and known functions about VEGF-A, VEGF-B, VEGF-C, and VEGF-D are covered in the review. VEGF-A can regulate angiogenesis, vascular permeability, and inflammation by binding with VEGFR-1 and VEGFR-2. VEGF-B can regulate angiogenesis, redox, and apoptosis by binding with VEGFR-1. VEGF-C can regulate inflammation, lymphangiogenesis, angiogenesis, apoptosis, and fibrogenesis by binding with VEGFR-2 and VEGFR-3. VEGF-D can regulate lymphangiogenesis, angiogenesis, fibrogenesis, and apoptosis by binding with VEGFR-2 and VEGFR-3. These functions present great potential of applying the VEGF family for treating CHD. For instance, angiogenesis can compensate for hypoxia and ischemia by growing novel blood vessels. Lymphangiogenesis can degrade inflammation by providing exits for accumulated inflammatory cytokines. Anti-apoptosis can protect myocardium from impairment after myocardial infarction (MI). Fibrogenesis can promote myocardial fibrosis after MI to benefit cardiac recovery. In addition, all these factors have been confirmed to keep a link with lipid metabolism, the research about which is still in the early stage and exact mechanisms are relatively obscure. Because few reviews have been published about the summarized role of the VEGF family for treating CHD, the aim of this review article is to present an overview of the available evidence supporting it and give hints for further research.

Comparison of Efficiency and Function of Vascular Endothelial Growth Factor Adenovirus Vectors in Endothelial Cells for Gene Therapy of Placental Insufficiency

Severe fetal growth restriction (FGR) affects 1:500 pregnancies, is untreatable and causes serious neonatal morbidity and death. Reduced uterine blood flow (UBF) and lack of bioavailable VEGF due to placental insufficiency is a major cause. Transduction of uterine arteries in normal or FGR sheep and guinea pigs using an adenovirus (Ad) encoding VEGF isoforms A (Ad.VEGF-A165) and a FLAG-tagged pre-processed short form D (DΔNΔC, Ad.VEGF-DΔNΔC-FLAG) increases endothelial nitric oxide expression, enhances relaxation and reduces constriction of the uterine arteries and their branches. UBF and angiogenesis are increased long term, improving fetal growth in utero. For clinical trial development we compared Ad.VEGF vector transduction efficiency and function in endothelial cells (ECs) derived from different species. We aimed to compare the transduction efficiency and function of the pre-clinical study Ad. constructs (Ad.VEGF-A165, Ad.VEGF-DΔNΔC-FLAG) with the intended clinical trial construct (Ad.VEGF-DΔNΔC) where the FLAG tag is removed. We infected ECs from human umbilical vein, pregnant sheep uterine artery, pregnant guinea pig aorta and non-pregnant rabbit aorta, with increasing multiplicity of infection (MOI) for 24 or 48 hours of three Ad.VEGF vectors, compared to control Ad. containing the LacZ gene (Ad.LacZ). VEGF supernatant expression was analysed by ELISA. Functional assessment used tube formation assay and Erk-Akt phosphorylation by ELISA. VEGF expression was higher after Ad.VEGF-DΔNΔC-FLAG and Ad.VEGF-DΔNΔC transduction compared to Ad.VEGF-A165 in all EC types (*p < 0.001). Tube formation was higher in ECs transduced with Ad.VEGF-DΔNΔC in all species compared to other constructs (***p < 0.001, *p < 0.05 with rabbit aortic ECs). Phospho-Erk and phospho-Akt assays displayed no differences between the three vector constructs, whose effect was, as in other experiments, higher than Ad.LacZ (***p < 0.001). In conclusion, we observed high transduction efficiency and functional effects of Ad.VEGF-DΔNΔC vector with comparability in major pathway activation to constructs used in pre-clinical studies, supporting its use in a clinical trial.

The History of the WHHL Rabbit, an Animal Model of Familial Hypercholesterolemia (II) - Contribution to the Development and Validation of the Therapeutics for Hypercholesterolemia and Atherosclerosis

A number of effective drugs have been developed through animal experiments, contributing to the health of many patients. In particular, the WHHL rabbit family (WHHL rabbits and its advanced strains (coronary atherosclerosis-prone WHHL-CA rabbits and myocardial infarction-prone WHHLMI rabbits) developed at Kobe University (Kobe, Japan) contributed greatly in the development of cholesterol-lowering agents. The WHHL rabbit family is animal models for human familial hypercholesterolemia, coronary atherosclerosis, and coronary heart disease. At the end of breeding of the WHHL rabbit family, this review summarizes the contribution of the WHHL rabbit family to the development of lipid-lowering agents and anti-atherosclerosis agents. Studies using the WHHL rabbit family demonstrated, for the first time in the world, that lowering serum cholesterol levels or preventing LDL oxidation can suppress the progression and destabilization of coronary lesions. In addition, the WHHL rabbit family contributed to the development of various compounds that exhibit lipid-lowering and anti-atherosclerotic effects and has also been used in studies of gene therapeutics. Furthermore, this review also discusses the causes of the increased discrepancy in drug development between the results of animal experiments and clinical studies, which became a problem in recent years, and addresses the importance of the selection of appropriate animal models used in studies in addition to an appropriate study design.

Pro-angiogenic efficacy of transplanting endothelial progenitor cells for treating hindlimb ischemia in hyperglycemic rabbits

AIMS

To evaluate the effectiveness of endothelial progenitor cells (EPCs) therapy in ischemia with or without hyperglycemia.

METHODS

Japanese White Rabbits were randomly assigned to three groups, group SH, hyperglycemia with sham therapy (n=10); group NE, normoglycemia with autologous EPCs transplantation therapy (n=12); and group HE, hyperglycemia with autologous EPCs transplantation therapy (n=12). Hyperglycemia was induced by injecting alloxan and sustained for 12weeks. Hindlimb ischemia was induced by complete excision of the femoral artery. Ex vivo-expanded EPCs were derived from autologous bone marrow and transplanted intermuscularily in the ischemic hindlimb. Fourteen days after transplantation, the indicators were determined.

RESULTS

There is no difference of the functions of ex vivo-expanded EPCs from autologous bone marrow between normoglycemic and hyperglycemic groups. We found significant improvement in both EPCs transplantation therapy groups compared to sham, in terms of the angiogenesis index (8.62±1.36, 11.12±2.23, 12.35±2.97), capillary density (7.06±0.91, 13.51±1.16, 13.90±2.78), capillary to muscle fiber ratio (0.68±0.09, 0.96±0.11,0.89±0.10), muscle VEGF expression (0.22±0.07, 0.41±0.08, 0.38±0.07ng/g). We found no significant differences between hyperglycemic and normoglycemic EPCs therapy groups except for 5 pro-angiogenic genes that were upregulated in HE as compared to NE.

CONCLUSION

Ex vivo expanded EPCs from autologous bone marrow transplantation is an effective therapeutic method for hindlimb ischemia in rabbits regardless of glycemic state.

Vascular endothelial growth factor-D: signaling mechanisms, biology, and clinical relevance

Vascular endothelial growth factor-D (VEGF-D) is a secreted glycoprotein that promotes growth of blood vessels (angiogenesis) and lymphatic vessels (lymphangiogenesis), and can induce remodeling of large lymphatics. VEGF-D enhances solid tumor growth and metastatic spread in animal models of cancer, and in some human cancers VEGF-D correlates with metastatic spread, poor patient outcome, and, potentially, with resistance to anti-angiogenic drugs. Hence, VEGF-D signaling is a potential target for novel anti-cancer therapeutics designed to enhance anti-angiogenic approaches and to restrict metastasis. In the cardiovascular system, delivery of VEGF-D in animal models enhanced angiogenesis and tissue perfusion, findings which have led to a range of clinical trials testing this protein for therapeutic angiogenesis in cardiovascular diseases. Despite these experimental and clinical developments, our knowledge of the signaling mechanisms driven by VEGF-D is still evolving--here we explore the biology of VEGF-D, its signaling mechanisms, and the clinical relevance of this growth factor.

Effects of aging on angiogenesis

Aging is a dominant risk factor for most forms of cardiovascular disease. Impaired angiogenesis and endothelial dysfunction likely contribute to the increased prevalence of both cardiovascular diseases and their adverse sequelae in the elderly. Angiogenesis is both an essential adaptive response to physiological stress and an endogenous repair mechanism after ischemic injury. In addition, induction of angiogenesis is a promising therapeutic approach for ischemic diseases. For these reasons, understanding the basis of age-related impairment of angiogenesis and endothelial function has important implications for understanding and managing cardiovascular disease. In this review, we discuss the molecular mechanisms that contribute to impaired angiogenesis in the elderly and potential therapeutic approaches to improving vascular function and angiogenesis in aging patients.

Vascular Endothelial Growth Factor (VEGF)-D Stimulates VEGF-A, Stanniocalcin-1, and Neuropilin-2 and Has Potent Angiogenic Effects

Objective—

The mature form of human vascular endothelial growth factor-D (hVEGF-D ΔNΔC ) is an efficient angiogenic factor, but its full mechanism of action has remained unclear. We studied the effects of hVEGF-D ΔNΔC in endothelial cells using gene array, signaling, cell culture, and in vivo gene transfer techniques.

Methods and Results—

Concomitant with the angiogenic and proliferative responses, hVEGF-D ΔNΔC enhanced the phosphorylation of VEGF receptor-2, Akt, and endothelial nitric oxide synthase. Gene arrays, quantitative reverse transcription–polymerase chain reaction, and Western blot revealed increases in VEGF-A, stanniocalcin-1 (STC1), and neuropilin (NRP) 2 expression by hVEGF-D ΔNΔC stimulation, whereas induction with hVEGF-A 165 altered the expression of STC1 and NRP1, another coreceptor for VEGFs. The effects of hVEGF-D ΔNΔC were seen only under high-serum conditions, whereas for hVEGF-A 165 , the strongest response was observed under low-serum conditions. The hVEGF-D ΔNΔC -induced upregulation of STC1 and NRP2 was also evident in vivo in mouse skeletal muscle treated with hVEGF-D ΔNΔC by adenoviral gene delivery. The importance of NRP2 in hVEGF-D ΔNΔC signaling was further studied with NRP2 small interfering RNA and NRP antagonist, which were able to block hVEGF-D ΔNΔC -induced survival of endothelial cells.

Conclusion—

In this study, the importance of serum and upregulation of NRP2 and STC1 for VEGF-D ΔNΔC effects were demonstrated. Better knowledge of VEGF-D ΔNΔC signaling and regulation is valuable for the development of efficient and safe VEGF-D ΔNΔC -based therapeutic applications for cardiovascular diseases.

Structural determinants of vascular endothelial growth factor-D receptor binding and specificity

Vascular endothelial growth factors (VEGFs) and their tyrosine kinase receptors (VEGFR-1-3) are central mediators of angiogenesis and lymphangiogenesis. VEGFR-3 ligands VEGF-C and VEGF-D are produced as precursor proteins with long N- and C-terminal propeptides and show enhanced VEGFR-2 and VEGFR-3 binding on proteolytic removal of the propeptides. Two different proteolytic cleavage sites have been reported in the VEGF-D N-terminus. We report here the crystal structure of the human VEGF-D Cys117Ala mutant at 2.9 Å resolution. Comparison of the VEGF-D and VEGF-C structures shows similar extended N-terminal helices, conserved overall folds, and VEGFR-2 interacting residues. Consistent with this, the affinity and the thermodynamic parameters for VEGFR-2 binding are very similar. In comparison with VEGF-C structures, however, the VEGF-D N-terminal helix was extended by 2 more turns because of a better resolution. Both receptor binding and functional assays of N-terminally truncated VEGF-D polypeptides indicated that the residues between the reported proteolytic cleavage sites are important for VEGF-D binding and activation of VEGFR-3, but not of VEGFR-2. Thus, we define here a VEGFR-2-specific form of VEGF-D that is angiogenic but not lymphangiogenic. These results provide important new insights into VEGF-D structure and function.