Response to anti-VEGF-A treatment of endothelial cells in vitro

Acrizanib as a Novel Therapeutic Agent for Fundus Neovascularization via Inhibitory Phosphorylation of VEGFR2

Purpose

The present study aimed to evaluate the effect of acrizanib, a small molecule inhibitor targeting vascular endothelial growth factor receptor 2 (VEGFR2), on physiological angiogenesis and pathological neovascularization in the eye and to explore the underlying molecular mechanisms.

Methods

We investigated the potential role of acrizanib in physiological angiogenesis using C57BL/6J newborn mice, and pathological angiogenesis using the mouse oxygen-induced retinopathy (OIR) and laser-induced choroidal neovascularization (CNV) models. Moreover, vascular endothelial growth factor (VEGF)-treated human umbilical vein endothelial cells (HUVECs) were used as an in vitro model for studying the molecular mechanism underlying acrizanib's antiangiogenic effects.

Results

The intravitreal injection of acrizanib did not show a considerable impact on physiological angiogenesis and retinal thickness, indicating a potentially favorable safety profile. In the mouse models of OIR and CNV, acrizanib showed promising results in reducing pathological neovascularization, inflammation, and vascular leakage, indicating its potential efficacy against pathological angiogenesis. Consistent with in vivo results, acrizanib blunted angiogenic events in VEGF-treated HUVECs such as proliferation, migration, and tube formation. Furthermore, acrizanib inhibited the multisite phosphorylation of VEGFR2 to varying degrees and the activation of its downstream signal pathways in VEGF-treated HUVECs.

Conclusions

This study suggested the potential efficacy and safety of acrizanib in suppressing fundus neovascularization. Acrizanib functioned through inhibiting multiple phosphorylation sites of VEGFR2 in endothelial cells to different degrees.

Translational Relevance

These results indicated that acrizanib might hold promise as a potential candidate for the treatment of ocular vascular diseases.

Expression and characterization of a novel single-chain anti-vascular endothelial growth factor antibody in the goat milk

Vascular endothelial growth factor (VEGF) has essential functions in angiogenesis, endothelial cell proliferation, migration, and tumor invasion. Different approaches have been developed to suppress tumor angiogenesis, which is considered a hallmark of cancer. Anti-VEGF monoclonal antibodies constitute an important strategy for cancer immunotherapy, which has been produced on several platforms. In this study, a novel single-chain anti-VEGF monoclonal antibody (scVEGFmAb) was produced in the goat mammary gland by adenoviral transduction. scVEGFmAb was purified by affinity chromatography. N-glycans were analyzed by exoglycosidase digestion and hydrophilic interaction ultra-performance liquid chromatography coupled to electrospray ionization mass spectrometry. The biological activity of scVEGFmAb was assessed by scratch and mouse aortic ring assays. scVEGFmAb was produced at 0.61 g/L in the goat milk, and its purification rendered 95 % purity. N-glycans attached to scVEGFmAb backbone were mainly neutral biantennary core fucosylated with Galβ1,4GlcNAc motif, and charged structures were capped with Neu5Ac and Neu5Gc. The chimeric molecule significantly prevented cell migration and suppressed microvessel sprouting. These results demonstrated for the first time the feasibility of producing an anti-VEGF therapeutic antibody in the milk of non-transgenic goats with the potential to counteract tumor angiogenesis.

Effect of intravitreal conbercept injection on VEGF-A and -B levels in the aqueous and vitreous humor of patients with proliferative diabetic retinopathy

The present study aimed to investigate the mechanisms of anti-VEGF treatment prior to eye surgery to reduce intraoperative bleeding. A total of 30 patients with proliferative vitreoretinopathy after clinical diagnosis were enrolled in the present study as the surgical group. Furthermore, 30 patients underwent intravitreal injection of the anti-VEGF drug conbercept and were considered the drug pretreatment group. The aqueous and vitreous humors from the eyes of patients in the surgical group were drawn during pars plana vitrectomy surgery. The aqueous humor in the eyes of patients in the drug pretreatment group was drawn prior to conbercept treatment and seven days after conbercept treatment immediately prior to surgery. The vitreous humor in this group was only taken during surgery. Furthermore, ELISA was used to detect the levels of VEGF-A and -B in the aqueous and vitreous humors. Semi-quantitative determination of VEGF-A and VEGF-B levels in fibrovascular proliferative membranes was performed using immunohistochemical staining. The results indicated that in the drug group, the levels of VEGF-A in the aqueous humor of patients prior to and after conbercept injection were 197.66±48.00 and 3.39±2.54 pg/ml, respectively. The levels of VEGF-A in the vitreous humor of patients in the surgical and drug groups were 267.53±179.60 and 21.43±5.81 pg/ml after injection, respectively. The levels of VEGF-B in the aqueous humor of patients prior to and after conbercept injection were 13.66±3.30 (before injection) and 2.17±0.94 pg/ml (after injection), respectively. The levels of VEGF-B in the vitreous humor of patients in the surgical and drug groups were 127.36±16.72 and 18.56±9.82 pg/ml after injection, respectively (P<0.05). Furthermore, in the drug group, the surgery time, bleeding and capillary formation were significantly reduced compared with those in the surgical group. Taken together, these results suggested that the levels of VEGF-A and -B decreased significantly in the aqueous humor of patients with PDR after conbercept injection. Furthermore, the levels of VEGF-A and -B in the vitreous humor of patients dropped significantly in the drug group compared with those in the surgical group. These results provide theoretical clinical support for the preoperative application of conbercept for patients with PDR.

Clinical pharmacology of intravitreal anti-VEGF drugs

Clinical efficacy of intravitreal anti-VEGF drugs has been widely demonstrated in several angiogenesis-driven eye diseases including diabetic macular edema and the neovascular form of age-related macular degeneration. Pegaptanib, ranibizumab, and aflibercept have been approved for use in the eye, whereas bevacizumab is widely used by ophthalmologists to treat patients "off-label". These drugs are active in the nanomolar to picomolar range; however, caution is required when establishing the rank order of affinity and potency due to in vitro inter-experimental variation. Despite the small doses used for eye diseases and the intravitreal route of administration may limit systemic side effects, these drugs can penetrate into blood circulation and alter systemic VEGF with unknown clinical consequences, particularly in vulnerable groups of patients. Clinical pharmacokinetics of ocular anti-VEGF agents should therefore be taken into account when choosing the right drug for the individual patient. The gaps in current understanding that leave open important questions are as follows: (i) uncertainty about which drug should be given first, (ii) how long these drugs can be used safely, and (iii) the choice of the best pharmacological strategy after first-line treatment failure. The current review article, based on the information published in peer-reviewed published papers relevant to anti-VEGF treatments and available on the PubMed database, describes in detail the clinical pharmacology of this class of drugs to provide a sound pharmacological basis for their proper use in ophthalmology clinical practice.

Intracrine VEGF signalling mediates colorectal cancer cell migration and invasion

Background:

Vascular endothelial growth factor (VEGF) and its receptors (VEGFRs) are key regulators of angiogenesis, affecting endothelial cell survival and function. However, the effect of VEGF-VEGFR signalling on tumour cell function is not well understood. Our previous studies in colorectal cancer (CRC) cells have demonstrated an intracrine VEGF/VEGFR1 signalling mechanism that mediates CRC cell survival and chemo-sensitivity. Since extracellular VEGF signalling regulates migration of endothelial cells and various tumour cells, we attempted to determine whether intracrine VEGF signalling affects CRC cell motility.

Methods:

Migration and invasion of CRC cells, with and without VEGF or VEGFR1 depletion, were assayed using transwell migration chambers. Changes in cell morphology, epithelial-mesenchymal transition (EMT) markers, and markers of cell motility were assessed by immunostaining and western blot.

Results:

Depletion of intracellular VEGF and VEGFR1 in multiple CRC cell lines led to strong inhibition of migration and invasion of CRC cells. Except for Twist, there were no significant differences in markers of EMT between control and VEGF/VEGFR1-depleted CRC cells. However, VEGF/VEGFR1-depleted CRC cells demonstrated a significant reduction in levels of phosphorylated focal adhesion kinase and its upstream regulators pcMET and pEGFR.

Conclusions:

Inhibition of intracrine VEGF signalling strongly inhibits CRC cell migration and invasion by regulating proteins involved in cell motility.

The Arteriovenous (AV) Loop in a Small Animal Model to Study Angiogenesis and Vascularized Tissue Engineering

A functional blood vessel network is a prerequisite for the survival and growth of almost all tissues and organs in the human body. Moreover, in pathological situations such as cancer, vascularization plays a leading role in disease progression. Consequently, there is a strong need for a standardized and well-characterized in vivo model in order to elucidate the mechanisms of neovascularization and develop different vascularization approaches for tissue engineering and regenerative medicine. We describe a microsurgical approach for a small animal model for induction of a vascular axis consisting of a vein and artery that are anastomosed to an arteriovenous (AV) loop. The AV loop is transferred to an enclosed implantation chamber to create an isolated microenvironment in vivo, which is connected to the living organism only by means of the vascular axis. Using 3D imaging (MRI, micro-CT) and immunohistology, the growing vasculature can be visualized over time. By implanting different cells, growth factors and matrices, their function in blood vessel network formation can be analyzed without any disturbing influences from the surroundings in a well controllable environment. In addition to angiogenesis and antiangiogenesis studies, the AV loop model is also perfectly suited for engineering vascularized tissues. After a certain prevascularization time, the generated tissues can be transplanted into the defect site and microsurgically connected to the local vessels, thereby ensuring immediate blood supply and integration of the engineered tissue. By varying the matrices, cells, growth factors and chamber architecture, it is possible to generate various tissues, which can then be tailored to the individual patient's needs.

Clinical study on local application of low-dose insulin for promoting wound healing after operation for deep burns

Transplanted free skin flaps are often needed to treat deep burns; their survival, however, is less than optimal. This study examined whether local low-dose insulin injections can promote flap survival and wound healing after surgery. A total of 165 patients who underwent free skin flap transplantation for simple deep burns were enrolled in the study and divided into 5 groups of 33 patients each: Blank control group (no local subcutaneous drug injections), saline control group (saline injections), low-dose insulin group (0.5 units regular insulin injections), medium-dose group (1.0 units regular insulin injections) and high-dose group (2.0 units regular insulin injections). Wound healing and flap survival conditions were assessed and compared among groups. The best wound healing rate found was that of the low-dose insulin injection group where all the parameters measured improved significantly: The healing time was shorter; the blood flow volume, the flap survival, the number of fibroblasts and new vessels increased; the re-epithelialization occurred faster; the infiltration of inflammatory cells was reduced; the expression levels of heat shock protein-90, vascular endothelial growth factor, transforming growth factor-β and interleukin-1 were higher; and the plasma glucose levels only fluctuated slightly. The results clearly demonstrate that a local low-dose insulin regime after flap transplantation can accelerate the healing time and improve the surgical outcome without exerting detrimental secondary effects on the glucose plasma level of deep burn patients.

LRRK2 knockdown in zebrafish causes developmental defects, neuronal loss, and synuclein aggregation

Although mutations in the leucine-rich repeat kinase 2 (LRRK2) gene are the most common cause of genetic Parkinson's disease, their function is largely unknown. LRRK2 is pleiotropic in nature, shown to be involved in neurodegeneration and in more peripheral processes, including kidney functions, in rats and mice. Recent studies in zebrafish have shown conflicting evidence that removal of the LRRK2 WD40 domain may or may not affect dopaminergic neurons and/or locomotion. This study shows that ∼50% LRRK2 knockdown in zebrafish causes not only neuronal loss but also developmental perturbations such as axis curvature defects, ocular abnormalities, and edema in the eyes, lens, and otic vesicles. We further show that LRRK2 knockdown results in significant neuronal loss, including a reduction of dopaminergic neurons. Immunofluorescence demonstrates that endogenous LRRK2 is expressed in the lens, brain, heart, spinal cord, and kidney (pronephros), which mirror the LRRK2 morphant phenotypes observed. LRRK2 knockdown results further in the concomitant upregulation of β-synuclein, PARK13, and SOD1 and causes β-synuclein aggregation in the diencephalon, midbrain, hindbrain, and postoptic commissure. LRRK2 knockdown causes mislocalization of the Na(+) /K(+) ATPase protein in the pronephric ducts, suggesting that the edema might be linked to renal malfunction and that LRRK2 might be associated with pronephric duct epithelial cell differentiation. Combined, our study shows that LRRK2 has multifaceted roles in zebrafish and that zebrafish represent a complementary model to further our understanding of this central protein. © 2016 Wiley Periodicals, Inc.