Age-dependent expression of VEGF isoforms and receptors in the rabbit anterior cruciate ligament

Association of genetic polymorphisms in vascular endothelial growth factor with susceptibility to coronary artery disease: a meta-analysis

Background

Single nucleotide polymorphisms (SNPs) located in the vascular endothelial growth factor (VEGF) gene may be correlated with the susceptibility to coronary artery disease (CAD) – although results have been controversial. The aim of this meta–analysis is to clarify the effects of VEGF –2578A/C (rs699947), −1154G/A (rs1570360), +405C/G (rs2010963), and + 936C/T (rs3025039) polymorphisms on CAD risk.

Methods

Pooled odds ratio (OR) and corresponding 95% confidence intervals (CIs) were calculated to estimate the strength of the association between VEGF gene polymorphisms and CAD risk. Fixed- or random-effects model was used depending on the heterogeneity between studies.

Results

In total, 13 eligible articles containing 29 studies were analysed. The pooled analysis indicated that the VEGF gene polymorphisms of rs699947, rs2010963, and rs3025039 were associated with an increased risk of CAD, whereas no significant associations were observed with the rs1570360 polymorphism. A subgroup analysis stratified by ethnicity revealed that the rs699947 and rs3025039 polymorphisms were associated with CAD risk in Asian populations. In addition, stratification by control source indicated an increased risk of CAD susceptibility with the rs699947 polymorphism for population–based studies of reduced heterogeneity.

Conclusions

In summary, we concluded that the VEGF gene polymorphisms rs699947, rs2010963, and rs3025039 are correlated with an elevated CAD risk.

Electronic supplementary material

The online version of this article (10.1186/s12881-018-0628-3) contains supplementary material, which is available to authorized users.

VEGF Splicing and the Role of VEGF Splice Variants: From Physiological-Pathological Conditions to Specific Pre-mRNA Splicing

During this past decade, the vascular endothelial growth factor (VEGF) pathway has been extensively studied. VEGF is a paradigm of molecular regulation since its expression is controlled at all possible steps including transcription, mRNA stability, translation, and pre-mRNA splicing. The latter form of molecular regulation is probably the least studied. This field has been neglected; yet different forms of VEGF with different sizes and different physiological properties issued from alternative splicing have been described a long time ago. Recently a new level of complexity was added to the field of splicing of VEGF pre-mRNA. Whereas thousands of publications have described VEGF as a pro-angiogenic factor, an alternative splicing event generates specific anti-angiogenic forms of VEGF that only differ from the others by a modification in the last six amino acids of the protein. According to the scientists who discovered these isoforms, which are indistinguishable from the pro-angiogenic ones with pan VEGF antibodies, some of the literature on VEGF is at least inexact if not completely false. Moreover, the presence of anti-angiogenic forms of VEGF may explain the disappointing efficacy of anti-VEGF therapies on the overall survival of patients with different forms of cancers and with wet age-related macular degeneration. This review focuses on the existence of the different alternative splice variants of VEGF and the molecular mechanisms associated with their expression and function.

Expression of vascular remodelling markers in relation to bradykinin receptors in asthma and COPD

BACKGROUND

Vascular remodelling plays a central role in asthma and chronic obstructive pulmonary disease (COPD). Bradykinin (BK) is a vasoactive proinflammatory peptide mediating acute responses in asthma. We investigated the role of angiogenic factors in relation to BK receptors in asthma and COPD.

METHODS

Bronchial biopsies from 33 patients with COPD, 24 old (≥50 years) patients with (≥50 years) asthma, 18 old control smokers, 11 old control non-smokers, 15 young (≤40yrs) patients with (≤40 years) asthma and 10 young control non-smokers were immunostained for CD31, vascular endothelial growth factor-A (VEGF-A), angiogenin and BK receptors (B2R and B1R). Fibroblast and endothelial co-localisation of relevant molecules were performed by immunofluorescence. BK-induced VEGF-A and angiogenin release was studied (ELISA) in bronchial fibroblasts from subjects with asthma and COPD.

RESULTS

In bronchial lamina propria of old patients with asthma, CD31 and VEGF-A(+) cell numbers were higher than old control non-smokers (p<0.05). Angiogenin(+), B2R(+) and B1R(+) cell numbers in old patients with asthma were higher than in old control non-smokers, control smokers and patients with COPD (p<0.01). Angiogenin(+) cell numbers were higher in patients with COPD than both old control groups (p<0.05). In all patients with asthma the number of B2R(+) cells was positively related to the numbers of B1R(+) (rs=0.43), angiogenin(+) (rs=0.42) and CD31 cells (rs=0.46) (p<0.01). Angiogenin(+) cell numbers were negatively related to forced expiratory volume in 1 s (rs=-0.415, p=0.008). Double immunofluorescence revealed that CD31 cells of capillary vessels coexpressed B2R and that fibroblasts coexpressed B2R, VEGF-A and angiogenin. BK (10(-6)M) induced significant angiogenin release in fibroblasts from asthma and to a lesser extent in COPD.

CONCLUSIONS

Unlike COPD, this study suggests the involvement of BK receptors in bronchial vascular remodelling in asthma.

VEGF receptor mRNA expression by ACL fibroblasts is associated with functional healing of the ACL

PURPOSE

Recent advances in the treatment of ACL ruptures employ platelet-rich plasma combined with collagen to modulate growth factor release from platelets to stimulate healing. Among the most notable of these growth factors is VEGF, which is a potent mitogen and stimulator of vascular growth and healing. However, the effect of such a growth factor on healing depends on the cellular ability to bind with its receptor. The purpose of this study was to test (1) whether the strength of a tissue-engineered ACL repair is associated with VEGF receptors' mRNA expression of ACL cells and (2) whether age influences this association.

METHOD

Nineteen female Yucatan pigs underwent enhanced ACL repair. Biomechanical testing was performed after 15 weeks of healing. Messenger RNA of VEGF receptors 1 and 2 in ACL fibroblasts was assessed by RT-PCR. The ACL structural properties were regressed on receptor expression levels in a multivariate model including serum levels of VEGF, age, and weight as potential confounders.

RESULT

While maximum load and linear stiffness were independent of VEGF receptor expression, VEGF receptor 1 was associated with displacement (positively) and yield load (negatively). In a multivariate model of VEGF receptor expression and biomechanics, age was associated with maximum load and yield load.

CONCLUSION

These findings suggest that high VEGF receptor expression, even more so at higher age, results in a more compliant scar, which in turn may lead to greater knee laxity and a compromised clinical result.

Bone regeneration properties of granulocyte colony-stimulating factor via neovascularization and osteogenesis

OBJECTIVES

It has been well recognized that appropriate vascularization is emerging as a prerequisite for bone development and regeneration. The aim of this study was to test the hypothesis that locally applied granulocyte colony-stimulating factor (G-CSF) enhances bone regeneration via revascularization and osteogenesis.

METHODS

A segmental bone defect (20mm) was created at the diaphysis of the rabbit ulna. The defects were treated with cationized gelatin hydrogel, which was the drug delivery system, with G-CSF, and then bone regeneration, neovascularization, and osteogenesis properties with G-CSF were assessed.

RESULTS

Radiographic, computed tomography, and histological findings revealed that bone formation was significantly promoted in G-CSF-treated group as early as 2 weeks. Immunohistochemistry, real-time reverse transcription-polymerase chain reaction, and flow cytometry studies indicated that angiogenesis/vasculogenesis, which are regulated by mobilization and incorporation of CD34+/G-CSF receptor (CSFR+) cells, and osteogenesis, which is regulated by osteocalcin+/G-CSFR+ cells, were also significantly enhanced in the G-CSF group.

CONCLUSIONS

This study suggests that locally applied G-CSF contributes to an ideal local environment for fracture healing by supplying adequate blood flow and stimulating osteogenesis. G-CSF may have the therapeutic potential for bone regeneration.

Use of genetically modified muscle and fat grafts to repair defects in bone and cartilage

We report a novel technology for the rapid healing of large osseous and chondral defects, based upon the genetic modification of autologous skeletal muscle and fat grafts. These tissues were selected because they not only possess mesenchymal progenitor cells and scaffolding properties, but also can be biopsied, genetically modified and returned to the patient in a single operative session. First generation adenovirus vector carrying cDNA encoding human bone morphogenetic protein-2 (Ad.BMP-2) was used for gene transfer to biopsies of muscle and fat. To assess bone healing, the genetically modified ("gene activated") tissues were implanted into 5mm-long critical size, mid-diaphyseal, stabilized defects in the femora of Fischer rats. Unlike control defects, those receiving gene-activated muscle underwent rapid healing, with evidence of radiologic bridging as early as 10 days after implantation and restoration of full mechanical strength by 8 weeks. Histologic analysis suggests that the grafts rapidly differentiated into cartilage, followed by efficient endochondral ossification. Fluorescence in situ hybridization detection of Y-chromosomes following the transfer of male donor muscle into female rats demonstrated that at least some of the osteoblasts of the healed bone were derived from donor muscle. Gene activated fat also healed critical sized defects, but less quickly than muscle and with more variability. Anti-adenovirus antibodies were not detected. Pilot studies in a rabbit osteochondral defect model demonstrated the promise of this technology for healing cartilage defects. Further development of these methods should provide ways to heal bone and cartilage more expeditiously, and at lower cost, than is presently possible.

Molecular diversity of VEGF-A as a regulator of its biological activity

The vascular endothelial growth factor (VEGF) family of proteins regulates blood flow, growth, and function in both normal physiology and disease processes. VEGF-A is alternatively spliced to form multiple isoforms, in two subfamilies, that have specific, novel functions. Alternative splicing of exons 5-7 of the VEGF gene generates forms with differing bioavailability and activities, whereas alternative splice-site selection in exon 8 generates proangiogenic, termed VEGF(xxx), or antiangiogenic proteins, termed VEGF(xxx)b. Despite its name, emerging roles for VEGF isoforms on cell types other than endothelium have now been identified. Although VEGF-A has conventionally been considered to be a family of proangiogenic, propermeability vasodilators, the identification of effects on nonendothelial cells, and the discovery of the antiangiogenic subfamily of splice isoforms, has added further complexity to their regulation of microvascular function. The distally spliced antiangiogenic isoforms are expressed in normal human tissue, but downregulated in angiogenic diseases, such as cancer and proliferative retinopathy, and in developmental pathologies, such as Denys Drash syndrome and preeclampsia. Here, we examine the molecular diversity of VEGF-A as a regulator of its biological activity and compare the role of the pro- and antiangiogenic VEGF-A splice isoforms in both normal and pathophysiological processes.

Injury-induced changes in mRNA levels differ widely between anterior cruciate ligament and medial collateral ligament

BACKGROUND

The drastic difference in healing capacity between the anterior cruciate ligament and the medial collateral ligament is still largely unexplained. Few studies have compared the profiles of messenger ribonucleic acid expression for healing-associated molecules in ligaments during the course of healing.

HYPOTHESIS

Injury responses of the injured anterior cruciate ligament and medial collateral ligament are characterized by very different profiles of angiogenesis-promoting and repair-associated gene expression during the healing process.

STUDY DESIGN

Controlled laboratory study.

METHODS

Reverse-transcriptase polymerase chain reaction was used to assay expression of messenger ribonucleic acid for 11 healing- and angiogenesis-associated molecules at 3 days and 2, 6, and 16 weeks after anterior cruciate ligament or medial collateral ligament injury in adult female New Zealand White rabbits.

RESULTS

Marked differences were found in the postinjury changes in messenger ribonucleic acid levels in the anterior cruciate ligament compared to the medial collateral ligament. Notably, messenger ribonucleic acid levels for the important repair-associated growth factor transforming growth factor-beta1 did not increase in injured anterior cruciate ligament at any time point. Similarly, unlike the injured medial collateral ligament, no statistically significant increases in messenger ribonucleic acid levels for the important scar matrix protein collagen III were detected in injured anterior cruciate ligament. In contrast, matrix metalloproteinase messenger ribonucleic acid levels were markedly elevated in injured anterior cruciate ligament but only modestly increased in medial collateral ligament.

CONCLUSION

The results suggest that injury leads to an antifibrotic, catabolic response in the rabbit anterior cruciate ligament, possibly to prevent fibrosis and diminish the risk for loss of joint motion.

CLINICAL RELEVANCE

The development of effective biologically based treatments for anterior cruciate ligament injuries will need to incorporate strategies to deal with the significant differences in the molecular responses to injury of these tissues.