Vascular endothelial growth factors and placenta growth factor in retinal vasculopathies: Current research and future perspectives

Abnormalities of retinal function in type 2 diabetes mellitus patients without clinical diabetic retinopathy detected by multifocal electroretinogram

OBJECTIVE

To study the changes of retinal function in type 2 diabetes mellitus(DM) patients without apparently diabetic retinopathy via multifocal electroretinogram.

METHODS

Thirty-six type 2 DM patients (72 eyes) without visible diabetic retinopathy were selected as the experimental group, and thirty-five healthy subjects (70 eyes) were selected as the control group. All subjects were underwent multifocal electroretinogram (mf- ERG).

RESULTS

Compared with the control group, the implicit time delay of the P1 wave in the first ring, third ring, fourth ring, and fifth ring of the experimental group was significant (t = -3.154, p = 0.004, t = -8.21, p = 0.000, t = -3.067, p = 0.004, t = -4.443, p = 0.000, respectively). The implicit time of the N1 wave in the fourth- and fifth-ring were also significantly delayed compared with the control group (t = -3.549, p = 0.001, t = 2.961, p = 0.005, respectively). Compared with the control group, the implicit time of the P1 wave and N1 wave in the temporal region of the experimental group were delayed (t = -2.148, p = 0.037, t = -2.834, p = 0.007, respectively). There were no significant difference between the experimental group and the control group of the temporal area in the amplitude density of P1 wave, N1 wave. There was no difference in the implicit time and amplitude density of the N1 and P1 waves in the nasal region between the experimental group and the control group. The multifocal electroretinogram complex parameters showed better specificity and sensitivity in the diagnosis of diabetic retinopathy.

CONCLUSION

The multifocal electroretinogram can detect abnormal changes in the retina of type 2 DM patients without visible diabetic retinopathy. The multifocal electroretinogram complex parameter is a potential indicator for the early diagnosis of diabetic retinopathy.

Serum and Vitreous Levels of Placenta Growth Factor in Diabetic Retinopathy Patients: Correlation With Disease Severity and Optical Coherence Tomographic Parameters

Purpose The primary objective of this study was to compare placenta growth factor (PlGF) levels in the serum and vitreous of diabetic retinopathy (DR) patients to non-diabetic controls. Additionally, the study aimed to establish associations between serum and vitreous PlGF concentrations and to examine the correlation between vitreous PlGF in DR patients and morphological parameters. Methods This study included serum and vitreous samples from 38 patients, including 21 patients with DR and 17 non-diabetic controls. The control group included non-diabetic patients with rhegmatogenous retinal detachment with retinal tears secondary to posterior vitreous detachment or trauma. PlGF levels were quantified in vitreous and serum samples using an enzyme-linked immunosorbent assay (ELISA). Optical coherence tomography (OCT) scans from DR patients were evaluated to measure the central retinal thickness (CRT) and macular volume (MV). Results DR patients had significantly higher mean vitreous PlGF levels compared to non-DR patients (70.0±39.2 vs. 46.47±9.7 pg/mL, p-value=0.004). However, no significant increase in mean serum PlGF levels was observed in DR patients (p-value=0.232). Within the DR group, proliferative DR (PDR) patients presented significantly higher vitreous PlGF levels than non-PDR (NPDR) patients (76.5±41.0 vs. 42.5±5.0 pg/mL, p-value=0.009). There was no association between serum and vitreous PlGF levels. The correlation between vitreous PlGF levels and morphological parameters was rsp=0.175, p-value=0.488 for CRT, and rsp=0.288, p-value=0.262 for MV. Conclusion This study emphasizes the important role of PlGF in neovascularization, specifically highlighting its overexpression exclusively in vitreous from PDR patients. The observed increase in PlGF levels may be indicative of disease severity. The lack of correlation between vitreous and serum PlGF levels suggests a potential dissociation between intravitreal and systemic PlGF synthesis. Consequently, targeting PlGF in therapeutic approaches may offer an additional strategy for ocular pathologies with a neovascular component.

Progress in the Application of Microneedles in Eye Disorders and the Proposal of the Upgraded Microneedle with Spinule

PURPOSE

In the local administration methods for treating eye diseases, the application of microneedles has great potential due to the shortcomings of low efficacy and significant side effects of local administration preparations. This article provides ideas for the research on the application of ophthalmic microneedle in the treatment of eye diseases.

RESULTS

This article analyzes the physiological structures of the eyes, ocular diseases and its existing ocular preparations in sequence. Finally, this article reviews the development and trends of ocular microneedles in recent years, and summarizes and discusses the drugs of ocular microneedles as well as the future directions of development. At the same time, according to the inspiration of previous work, the concept of "microneedle with spinule" is proposed for the first time, and its advantages and limitations are discussed in the article.

CONCLUSIONS

At present, the application of ocular microneedles still faces multiple challenges. The aspects of auxiliary devices, appearance, the properties of the matrix materials, and preparation technology of ophthalmic microneedle are crucial for their application in the treatment of eye diseases.

Progression of bilateral morning glory syndrome associated with unilateral persistent fetal vasculture: A case report of long term follow-up in an infant

PURPOSE

To describe a case of Bilateral Morning Glory Syndrome (MGS) associated with Unilateral Persistent Fetal Vasculature (PFV) in a 3-day old neonate.

OBSERVATIONS

A 3-day-old neonate was found bilateral retinal abnormalities due to neonatal eye screening. Dilated fundus exam showed bilateral optic disc dysplasia with the persistent hyaloid vessels in right eye at first. With the progress of the disease, optic disc was enlarged with central umbilication which with a similar anomalous radiating peripapillary vascular appearance, the persistent hyaloid vessels in vitreous cavity of right eye gradually disappear, a large amount of exudation can be seen in the posterior pole retina with macular movement in both eyes. Bilateral vitrectomy was performed in this case, then the condition of the neonate's both eyes is stable until 1 year old.

CONCLUSIONS AND IMPORTANCE

This is a rare case that showing the development of MGS and PFV and the relationship between these two diseases. In addition, we completely observed the whole process of the change of the persistent hyaloid vessels in the vitreous cavity of a case of MGS associated with PFV.

Human retinal secretome: A cross-link between mesenchymal and retinal cells

In recent years, mesenchymal stem cells (MSC) have been considered the most effective source for regenerative medicine, especially due to released soluble paracrine bioactive components and extracellular vesicles. These factors, collectively called the secretome, play crucial roles in immunomodulation and in improving survival and regeneration capabilities of injured tissue. Recently, there has been a growing interest in the secretome released by retinal cytotypes, especially retinal pigment epithelium and Müller glia cells. The latter trophic factors represent the key to preserving morphofunctional integrity of the retina, regulating biological pathways involved in survival, function and responding to injury. Furthermore, these factors can play a pivotal role in onset and progression of retinal diseases after damage of cell secretory function. In this review, we delineated the importance of cross-talk between MSCs and retinal cells, focusing on common/induced secreted factors, during experimental therapy for retinal diseases. The cross-link between the MSC and retinal cell secretomes suggests that the MSC secretome can modulate the retinal cell secretome and vice versa. For example, the MSC secretome can protect retinal cells from degeneration by reducing oxidative stress, autophagy and programmed cell death. Conversely, the retinal cell secretome can influence the MSC secretome by inducing changes in MSC gene expression and phenotype.

Comparison of widefield swept-source optical coherence tomographic angiography and fluorescein fundus angiography for detection of retinal neovascularization with diabetic retinopathy

BACKGROUND

To compare vitreous angiomosaic images (VAMIs), obtained by widefield swept-source optical coherence tomographic angiography (wfSS-OCTA) and the image of fluorescein fundus angiography (FFA) in the identification of retinal neovascularization (NV) in patients with diabetic retinopathy (DR).

METHODS

In this prospective observational study, severe non-proliferative diabetic retinopathy (NPDR) or proliferative DR (PDR) patients were included. All patients underwent FFA and wfSS-OCTA. The number of NVs identified by wfSS-OCTA VAMIs using five fixations 12 × 12 mm montage scans and the resembling FFA images were compared.

RESULTS

Fifty-three eyes of 29 patients were enrolled. NVs were detected in 25 eyes by using FFA, including 9 NVs of the disc (NVDs) and 72 NVs elsewhere (NVEs), and in 29 eyes by OCTA, including 11 NVDs and 90 NVEs. The detection rate of NV and NVD of OCTA was comparable to that of FFA (p > 0.05), and the level of agreement was excellent (κ = 0.850, κ = 0.754). Using FFA as the gold standard, the sensitivity for detection of NV by OCTA was 100.0%, specificity was 85.7%, the positive-predictive value was 86.2%, and the negative-predictive value was 100.0%. Compared with FFA, OCTA was superior in terms of the number of NVEs identified (p = 0.024). When we excluded images of patients treated with anti-vascular endothelial growth factor (VEGF) intravitreal therapy for < 3 months, OCTA was comparable to FFA in terms of the number of NVEs discovered (p = 0.203), with excellent agreement (intraclass correlation coefficient = 0.941).

CONCLUSIONS

WfSS-OCTA is an independent non-invasive alternative to FFA for NV discovery, NVD detection, and individual NVE identification, particularly in patients with PDR who have a history of prior treatment with anti-VEGF.

Determination of Vascular Endothelial Growth Factor-B Concentrations in Aqueous Humor and Plasma of Neovascular Age-Related Macular Degeneration and Polypoidal Choroidal Vasculopathy Patients Before and After Anti-VEGF Therapy

INTRODUCTION

Anti-vascular endothelial growth factor (anti-VEGF) injection was widely used in patients with neovascular age-related macular degeneration (nAMD) and polypoidal choroidal vasculopathy (PCV); however, the systemic and local levels of vascular endothelial growth factor (VEGF)-B were seldom detected before. This study was conducted to detect and compare the aqueous humor and plasma VEGF-B levels in nAMD and PCV before and after anti-VEGF therapy.

METHODS

Concentrations of VEGF-B in aqueous humor and plasma of individuals with nAMD (n = 10), PCV (n = 22), and age-related cataract controls (n = 12) were measured by enzyme-linked immunosorbent assay. Ranibizumab was injected intravitreally in patients monthly for three consecutive months. Before each injection in patients and at the baseline of controls, blood and aqueous humor samples were collected. Best-corrected visual acuity (BCVA) and central retinal thickness (CRT) were collected before each injection in patient groups. The differences of BCVA, CRT, and VEGF-B levels in aqueous humor and plasma between groups before and after anti-VEGF therapy were compared.

RESULTS

VEGF-B was overexpressed in aqueous humor and plasma of nAMD and PCV groups compared with control group (P < 0.05), but no statistically significant difference existed across nAMD and PCV groups (P > 0.05). Moreover, there were no obvious difference in levels of VEGF-B in aqueous humor and plasma within the treatment groups after anti-VEGF treatment (P > 0.05). The mean CRT in the nAMD group was thinner than that in the PCV group at baseline (P < 0.01). After injections, the CRT obviously declined in both groups (P < 0.05). There was no correlation between CRT reduction and high VEGF-B expression in aqueous humor and plasma of treatment groups.

CONCLUSION

Overexpression of VEGF-B locally and systemically in patients with nAMD and PCV indicated that elevated VEGF-B concentrations were relevant to the disease processes. Ranibizumab did not influence the levels of VEGF-B in the real world. CRT might help to distinguish PCV from nAMD.

Proteomics profiling of vitreous humor reveals complement and coagulation components, adhesion factors, and neurodegeneration markers as discriminatory biomarkers of vitreoretinal eye diseases

Introduction

Diabetic retinopathy (DR) and age-related macular degeneration (AMD) are leading causes of visual impairment and blindness in people aged 50 years or older in middle-income and industrialized countries. Anti-VEGF therapies have improved the management of neovascular AMD (nAMD) and proliferative DR (PDR), no treatment options exist for the highly prevalent dry form of AMD.

Methods

To unravel the biological processes underlying these pathologies and to find new potential biomarkers, a label-free quantitative (LFQ) method was applied to analyze the vitreous proteome in PDR (n=4), AMD (n=4) compared to idiopathic epiretinal membranes (ERM) (n=4).

Results and discussion

Post-hoc tests revealed 96 proteins capable of differentiating among the different groups, whereas 118 proteins were found differentially regulated in PDR compared to ERM and 95 proteins in PDR compared to dry AMD. Pathway analysis indicates that mediators of complement, coagulation cascades and acute phase responses are enriched in PDR vitreous, whilst proteins highly correlated to the extracellular matrix (ECM) organization, platelet degranulation, lysosomal degradation, cell adhesion, and central nervous system development were found underexpressed. According to these results, 35 proteins were selected and monitored by MRM (multiple reaction monitoring) in a larger cohort of patients with ERM (n=21), DR/PDR (n=20), AMD (n=11), and retinal detachment (n=13). Of these, 26 proteins could differentiate between these vitreoretinal diseases. Based on Partial least squares discriminant and multivariate exploratory receiver operating characteristic (ROC) analyses, a panel of 15 discriminatory biomarkers was defined, which includes complement and coagulation components (complement C2 and prothrombin), acute-phase mediators (alpha-1-antichymotrypsin), adhesion molecules (e.g., myocilin, galectin-3-binding protein), ECM components (opticin), and neurodegeneration biomarkers (beta-amyloid, amyloid-like protein 2).

Essential Role of Multi-Omics Approaches in the Study of Retinal Vascular Diseases

Retinal vascular disease is a highly prevalent vision-threatening ocular disease in the global population; however, its exact mechanism remains unclear. The expansion of omics technologies has revolutionized a new medical research methodology that combines multiple omics data derived from the same patients to generate multi-dimensional and multi-evidence-supported holistic inferences, providing unprecedented opportunities to elucidate the information flow of complex multi-factorial diseases. In this review, we summarize the applications of multi-omics technology to further elucidate the pathogenesis and complex molecular mechanisms underlying retinal vascular diseases. Moreover, we proposed multi-omics-based biomarker and therapeutic strategy discovery methodologies to optimize clinical and basic medicinal research approaches to retinal vascular diseases. Finally, the opportunities, current challenges, and future prospects of multi-omics analyses in retinal vascular disease studies are discussed in detail.

Vitreous protein networks around ANG2 and VEGF in proliferative diabetic retinopathy and the differential effects of aflibercept versus bevacizumab pre-treatment

Extracellular signalling proteins interact in networks rather than in isolation. In this context we investigated vitreous protein levels, including placental growth factor (PlGF), angiopoietin-2 (ANG2) and vascular endothelial growth factor (VEGF), in patients with proliferative diabetic retinopathy (PDR) with variable disease severities, and after anti-VEGF pre-treatment. Vitreous samples of 112 consecutive patients undergoing vitrectomy for PDR and of 52 non-diabetic patients with macular holes as controls were studied. A subset of the PDR patients were treated with either aflibercept (AFB, n = 25) or bevacizumab (BVZ)/ranibizumab (RZB) (n = 13), before surgery. Antibody-based analysis of 35 proteins (growth factors and cytokines) showed a significant increase in expression levels of 27 proteins in PDR patients as compared to controls. In network analysis of co-regulated proteins, a strong correlation in expression levels between VEGF, PlGF, MCP1 and ANG2 was found, mostly clustered around ANG2. In the AFB treatment group, concentrations of several proteins were decreased, including VEGFR1, whereas interleukin 6 and 8 were increased as compared to untreated PDR patients. The observed differences in vitreous protein levels between the different treatments and untreated PDR patients may underlie differences in clinical outcomes in patients with PDR.

Retinal Oxygen Metabolism in Patients With Type 2 Diabetes and Different Stages of Diabetic Retinopathy

The aim of this cross-sectional study was to assess retinal oxygen metabolism in patients with type 2 diabetes and different stages of nonproliferative diabetic retinopathy (DR) (n = 67) compared with healthy control subjects (n = 20). Thirty-four patients had no DR, 15 had mild DR, and 18 had moderate to severe DR. Retinal oxygen saturation in arteries and veins was measured using the oxygen module of a retinal vessel analyzer. Total retinal blood flow (TRBF) was measured using a custom-built Doppler optical coherence tomography system. Retinal oxygen extraction was calculated from retinal oxygen saturation and TRBF. Arteriovenous difference in oxygen saturation was highest in healthy subjects (34.9 ± 7.5%), followed by patients with no DR (32.5 ± 6.3%) and moderate to severe DR (30.3 ± 6.5%). The lowest values were found in patients with mild DR (27.3 ± 8.0%, P = 0.010 vs. healthy subjects). TRBF tended to be higher in patients with no DR (40.1 ± 9.2 μL/min) and mild DR (41.8 ± 15.0 μL/min) than in healthy subjects (37.2 ± 5.7 μL/min) and patients with moderate to severe DR (34.6 ± 10.4 μL/min). Retinal oxygen extraction was the highest in healthy subjects (2.24 ± 0.57 μL O2/min), followed by patients with no DR (2.14 ± 0.6 μL O2/min), mild DR (1.90 ± 0.77 μL O2/min), and moderate to severe DR (1.78 ± 0.57 μL O2/min, P = 0.040 vs. healthy subjects). These results indicate that retinal oxygen metabolism is altered in patients with type 2 diabetes. Furthermore, retinal oxygen extraction decreases with increasing severity of DR.

VEGF-targeting drugs for the treatment of retinal neovascularization in diabetic retinopathy

Diabetic retinopathy (DR) is the most common microangiopathic complication of diabetes mellitus, representing a major cause of visual impairment in developed countries. Proliferative DR (PDR) represents the last stage of this extremely complex retinal disease, characterized by the development of neovascularization induced by the abnormal production and release of vascular endothelial growth factor (VEGF). The term VEGF includes different isoforms; VEGF-A represents one of the most important pathogenic factors of DR. Anti-VEGF intravitreal therapies radically changed the outcome of DR, due to combined anti-angiogenic and anti-edematous activities. Nowadays, several anti-VEGF molecules exist, characterized by different pharmacological features and duration. With respect to PDR, although anti-VEGF treatments represented a fundamental step forward in the management of this dramatic complication, a big debate is present in the literature regarding the role of anti-VEGF as substitute of panretinal photocoagulation or if these two approaches may be used in combination. In the present review, we provided an update on VEGF isoforms and their role in DR pathogenesis, on current anti-VEGF molecules and emerging new drugs, and on the current management strategies of PDR. There is an overall agreement regarding the relative advantage provided by anti-VEGF, especially looking at the management of PDR patients requiring vitrectomy, with respect to laser. Based on the current data, laser approaches might be avoided when a perfectly planned anti-VEGF therapeutic strategy can be adopted. Conversely, laser treatment may have a role for those patients unable to guarantee enough compliance to anti-VEGF injections.Key messagesVEGF increased production, stimulated by retinal hypoperfusion and ischaemia, is a major pathogenic factor of neovascular complication onset in diabetic retinopathy and of DR stages progression.Nowadays, several anti-VEGF molecules are available in clinical practice and other molecules are currently under investigation. Each anti-VEGF molecule is characterized by different targets and may interact with multiple biochemical pathways within the eye.All the data agreed in considering anti-VEGF molecules as a first line choice for the management of diabetic retinopathy. Laser treatments may have a role in selected advanced cases and for those patients unable to guarantee enough compliance to intravitreal treatments schemes.

Dysfunction of ABC Transporters at the Surface of BBB: Potential Implications in Intractable Epilepsy and Applications of Nanotechnology Enabled Drug Delivery

Epilepsy is a chronic neurological disorder affecting 70 million people globally. One of the fascinating attributes of brain microvasculature is the (BBB), which controls a chain of distinct features that securely regulate the molecules, ions, and cells movement between the blood and the parenchyma. The barrier's integrity is of paramount importance and essential for maintaining brain homeostasis, as it offers both physical and chemical barriers to counter pathogens and xenobiotics. Dysfunction of various transporters in the (BBB), mainly ATP binding cassette (ABC), is considered to play a vital role in hampering the availability of antiepileptic drugs into the brain. ABC (ATP-binding cassette) transporters constitute a most diverse protein superfamily, which plays an essential part in various biological processes, including cell homeostasis, cell signaling, uptake of nutrients, and drug metabolism. Moreover, it plays a crucial role in neuroprotection by out-flowing various internal and external toxic substances from the interior of a cell, thus decreasing their buildup inside the cell. In humans, forty-eight ABC transporters have been acknowledged and categorized into subfamilies A to G based on their phylogenetic analysis. ABC subfamilies B, C, and G, impart a vital role at the BBB in guarding the brain against the entrance of various xenobiotic and their buildup. The illnesses of the central nervous system have received a lot of attention lately Owing to the existence of the BBB, the penetration effectiveness of most CNS medicines into the brain parenchyma is very limited (BBB). In the development of neurological therapies, BBB crossing for medication delivery to the CNS continues to be a major barrier. Nanomaterials with BBB cross ability have indeed been extensively developed for the treatment of CNS diseases due to their advantageous properties. This review will focus on multiple possible factors like inflammation, oxidative stress, uncontrolled recurrent seizures, and genetic polymorphisms that result in the deregulation of ABC transporters in epilepsy and nanotechnology-enabled delivery across BBB in epilepsy.

Comparisons of the short-term effectiveness and safety of surgical treatment for neovascular glaucoma: a systematic review and network meta-analysis

OBJECTIVE

To compare the effectiveness and safety of the six interventions for neovascular glaucoma.

DESIGN

A systematic review and network meta-analysis.

METHODS

Randomised controlled trials and cohort studies which compared the six interventions in neovascular glaucoma were identified using the following databases searched up to 1 September 2020: PubMed, Cochrane Library, Embase and Web of Science. The quality assessment was conducted by using the Cochrane risk of bias tool and the Newcastle-Ottawa scale. The primary outcome measure was the weighted mean differences for intraocular pressure reduction. Secondary one was ORs for success rate. Outcome measures were reported with a 95% CI and p<0.05 was considered statistically significant. Network meta-analysis was performed using Stata V.15.0.

RESULTS

Twenty-three studies involving a total of 1303 patients were included. The types of surgical treatments included Ahmed glaucoma valve (AGV) implant surgery, AGV combined with intravitreal anti-vascular endothelial growth factor (AGV +IVAV), cyclophotocoagulation (CPC), cyclocryotherapy (CCT), trabeculectomy with mitomycin (Trab(MMC)) and Trab(MMC) combined with IVAV (Trab(MMC)+IVAV). Network meta-analysis showed that in comparison with AGV, AGV +IVAV (MD=4.74, 95% CI 1.04 to 8.45) and Trab(MMC)+IVAV (MD=6.19, 95% CI 0.99 to 11.40) showed a favourable effect in intraocular pressure reduction (IOPR) 6 months after surgery. Compared with CCT, AGV (OR=-0.17, 95% CI -0.53 to -0.05), AGV +IVAV (OR=-0.10, 95% CI -3.48 to -1.19), CPC (OR=-0.12, 95% CI -0.53 to -0.05), Trab(MMC) (OR=3.54, 95% CI 1.15 to 10.91) and Trab(MMC)+IVAV (OR=5.78, 95% CI 2.29 to 14.61) showed a superior impact in success rate. The order of efficacy as best intervention ranked as follows: Trab(MMC)+IVAV (IOPR 6 months after surgery, surface under the cumulative ranking (SUCRA)=88.1), CPC (IOPR 12 months after surgery, SUCRA=81.9), AGV +IVAV (IOPR 12 months after surgery, SUCRA=79.9) and AGV +IVAV (success rate, SUCRA=92.7). Adverse events were also summarised in detail.

CONCLUSION

In the treatment of neovascular glaucoma, AGV+IVAV and CPC were more effective in IOPR and success rate than the other four interventions. Additionally, AGV+IVAV is superior to CPC concerning the success rate in the long-term treatment. However, considering the limitations of this review, more high-quality trials, especially those surgical interventions not mentioned in this review, should be carried out in the future to further confirm the current findings.

Hypoxia-Mimetic CoCl2 Agent Enhances Pro-Angiogenic Activities in Ovine Amniotic Epithelial Cells-Derived Conditioned Medium

Amniotic epithelial stem cells (AECs) are largely studied for their pro-regenerative properties. However, it remains undetermined if low oxygen (O₂) levels that AECs experience in vivo can be of value in maintaining their biological properties after isolation. To this aim, the present study has been designed to evaluate the effects of a hypoxia-mimetic agent, cobalt chloride (CoCl₂), on AECs’ stemness and angiogenic activities. First, a CoCl₂ dose-effect was performed to select the concentration able to induce hypoxia, through HIF-1α stabilization, without promoting any cytotoxicity effect assessed through the analysis of cell vitality, proliferation, and apoptotic-related events. Then, the identified CoCl₂ dose was evaluated on the expression and angiogenic properties of AECs’ stemness markers (OCT-4, NANOG, SOX-2) by analysing VEGF expression, angiogenic chemokines’ profiles, and AEC-derived conditioned media activity through an in vitro angiogenic xeno-assay. Results demonstrated that AECs are sensitive to the cytotoxicity effects of CoCl₂. The unique concentration leading to HIF-1α stabilization and nuclear translocation was 10 µM, preserving cell viability and proliferation up to 48 h. CoCl₂ exposure did not modulate stemness markers in AECs while progressively decreasing VEGF expression. On the contrary, CoCl₂ treatment promoted a significant short-term release of angiogenic chemokines in culture media (CM). The enrichment in bio-active factors was confirmed by the ability of CoCl₂-derived CM to induce HUVEC growth and the cells’ organization in tubule-like structures. These findings demonstrate that an appropriate dose of CoCl₂ can be adopted as a hypoxia-mimetic agent in AECs. The short-term, chemical-induced hypoxic condition can be targeted to enhance AECs’ pro-angiogenic properties by providing a novel approach for stem cell-free therapy protocols.

N-carboxymethyl chitosan/sodium alginate composite hydrogel loading plasmid DNA as a promising gene activated matrix for in-situ burn wound treatment

Improving the degree of vascularization through the regulation of wound microenvironment is crucial for wound repair. Gene activated matrix (GAM) technology provides a new approach for skin regeneration. It is a local gene delivery system that can not only maintain a moist environment, but also increase the concentration of local active factors. For this purpose, we fabricated the mVEGF165/TGF-β₁ gene-loaded N-carboxymethyl chitosan/sodium alginate hydrogel and studied its effect on promoting deep second degree burn wound repair. The average diameter of the hydrogel pores was 100 μm and the porosity was calculated as 50.9%. SEM and CLSM images showed that the hydrogel was suitable for cell adhesion and growth. The NS-GAM could maintain continuous expression for at least 9 days in vitro, showing long-term gene release and expression effect. Deep second-degree burn wound model was made on the backs of Wistar rats to evaluate the healing effect. The wounds were healed by day 22 in NS-GAM group with the prolonged high expression of VEGF and TGF-β₁ protein. A high degree of neovascularization and high expression level of CD34 were observed in NS-GAM group in 21 days. The histological results showed that NS-GAM had good tissue safety and could effectively promote epithelialization and collagen regeneration. These results indicated that the NS-GAM could be applied as a promising local gene delivery system for the repair of deep second-degree burn wounds.

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The plasmids loaded in NS-GAM can achieve efficient gene delivery and expression in vitro and in vivo.

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The NS-GAM showed long-term controlled release function of the plasmids.

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The NS-GAM played a significant effect on neovascularization by means of gene delivery.

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The NS-GAM could achieve efficient in situ repair on deep second degree burn wounds.

Effect of Probenecid on Endothelial Cell Growth Rate and Retinal Angiogenesis in an Oxygen-Induced Retinopathy Model

Objectives: Probenecid is an anion transport inhibitor, which, according to the connectivity map (CMap; a biological application database), interferes with hypoxia-induced gene expression changes in retinal vascular endothelial cells (ECs). Here, we investigated the influence of probenecid on retinal EC cytotoxicity and retinal neovascularization in a murine oxygen-induced retinopathy (OIR) model.

Methods: The retinal EC growth rate in the presence of hypoxia-mimicking concentrations of cobalt chloride (CoCl₂) was determined using the thiazolyl blue tetrazolium bromide (MTT) assay and proliferating cell nuclear antigen (PCNA) expression. In OIR rats, probenecid was administered by intraperitoneal injection (i.p.) from postnatal day (P) 1 to P7. The concentrations of vitreous humor vascular endothelial growth factor (VEGF), hypoxia-inducible factor (HIF)-1α, and placental growth factor (PlGF) were determined by using the ELISA kit at P21. The amount of newly formed vascular lumen was evaluated by histopathological examination. Retinopathy and neovascularization were assessed by scoring isolectin B4 fluorescein–stained retinal flat mounts. Western blots for liver tissue HIF-1α and hepcidin (HAMP) were performed.

Results:In vitro, probenecid led to the recession of the hypoxia-induced EC growth rate. In vivo, compared to the OIR retina, the upregulation of VEGF, HIF-1α, and PlGF in phase II retinopathy of prematurity (ROP) was inhibited by probenecid administration. Moreover, probenecid ameliorated neovascularization and resulted in significantly reduced relative leakage fluorescence signal intensity in fluorescein-stained retinal flat mounts (p < 0.05). Probenecid alleviated the liver overactivation of HAMP and downregulation of HIF-1α in OIR rats.

Conclusions: This is the first demonstration that implies that probenecid might be a protective compound against retinal angiogenesis in OIR. These changes are accompanied with decreased hyperoxia-mediated hepcidin overproduction. Although the relevance of the results to ROP needs further research, these findings may help establish potential pharmacological targets based on the CMap database.

Hypoxia Induces Galectin-1 Expression Via Autoinduction of Placental Growth Factor in Retinal Pigment Epithelium Cells

Purpose

Galectin-1/LGALS1, a β-galactoside-binding protein, contributes to angiogenesis and fibrosis in various ocular diseases. Hypoxia-dependent and -independent pathways upregulate galectin-1/LGALS1 expression in Müller glial cells. Here, we present novel findings on the galectin-1/LGALS1 regulatory system in human retinal pigment epithelium (RPE) cells, the major cellular participant in the pathogenesis of neovascular age-related macular degeneration (nAMD).

Methods

Human RPE cells were used to evaluate changes in gene and protein expression with real-time quantitative PCR and immunoblot analyses, respectively. The promoter and enhancer regions of LGALS1 were analyzed by reporter assay and chromatin immunoprecipitation. Immunofluorescence analysis of nAMD patient specimens was used to confirm the in vitro findings.

Results

Hypoxia induced galectin-1/LGALS1 expression via binding of hypoxia-inducible factor 1α (HIF-1α) to hypoxia-responsive elements in the LGALS1 promoter region. Blockade of vascular endothelial growth factor receptor 1 (VEGFR1) partially decreased hypoxia-induced galectin-1/LGALS1 expression. Among several VEGFR1 ligands induced by hypoxia, placental growth factor (PlGF)/PGF alone upregulated galectin-1/LGALS1 expression via phosphorylation of activator protein 1 (AP-1) subunits following AKT and p38 mitogen-activated protein kinase (MAPK) activation. An AP-1 site in the LGALS1 enhancer region was required for PlGF-induced galectin-1/LGALS1 expression in RPE cells. PlGF application upregulated PGF expression via extracellular signal-regulated kinase 1 and 2, AKT, and p38 MAPK pathways. nAMD patient specimens demonstrated co-localization of galectin-1 with HIF-1α, PlGF, and VEGFR1 in RPE cells.

Conclusions

Our present findings implicate the significance of hypoxia as a key inducer of galectin-1/LGALS1 in RPE cells and the autoinduction of hypoxia-induced PlGF as a vicious cycle amplifying the pathogenesis of nAMD.

The Vitreous Ecosystem in Diabetic Retinopathy: Insight into the Patho-Mechanisms of Disease

Diabetic retinopathy is one of the leading causes of blindness in the world with the incidence of disease ever-increasing worldwide. The vitreous humor represents an extensive and complex interactive arena for cytokines in the diabetic eye. In recent decades, there has been significant progress in understanding this environment and its implications in disease pathophysiology. In this review, we investigate the vitreous ecosystem in diabetic retinopathy at the molecular level. Areas of concentration include: the current level of knowledge of growth factors, cytokine and chemokine mediators, and lipid-derived metabolites in the vitreous. We discuss the molecular patho-mechanisms of diabetic retinopathy based upon current vitreous research.

PlGF knockdown attenuates hypoxia-induced stimulation of cell proliferation and glycolysis of lung adenocarcinoma through inhibiting Wnt/β-catenin pathway

Background

Angiogenic placental growth factor (PlGF) plays a role in hypoxia-induced angiogenesis. Here, we aimed to investigate the biological roles of PlGF in cell proliferation and glycolysis of lung adenocarcinoma (LUAD) and the underlying molecular mechanisms.

Methods

PlGF was knocked down in H358 and H1975 cells by lentiviruses, which were then cultured under hypoxia (90% N₂, 5%CO₂ and 5%O₂) for 24 h. PlGF was overexpressed in PC9 cells treated with XAV939, inhibitor of Wnt/β-catenin signaling pathway. PlGF-silencing H1975 cells were implanted into mice, and tumor xenografts were harvested and analyzed.

Results

Hypoxia treatment led to up-regulation of PlGF, C-myc, lactate dehydrogenase A (LDHA), and β-catenin, promotion of cell proliferation and glycolysis in H358 and H1975 cells, which were obviously reversed by knocking down PlGF. In tumors, PlGF knockdown significantly prohibited cell proliferation and glycolysis, and decreased expression of C-myc, LDHA, and β-catenin. PlGF overexpression markedly strengthened cell proliferation, which was inhibited by β-catenin knockdown. Consistently, XAV939, inhibitor of Wnt/β-catenin pathway, also inhibited PlGF-induced cell proliferation, glycolysis, and β-catenin expression in PC9 cells.

Conclusion

PlGF knockdown inhibited the stimulatory effect of hypoxia on cell proliferation and glycolysis of LUAD through deactivating Wnt/β-catenin pathway.

Scutellaria barbata D. Don Polysaccharides Inhibit High Glucose-Induced Proliferation and Angiogenesis of Retinal Vascular Endothelial Cells

PURPOSE

The traditional Chinese medicine Scutellaria barbata D. Don (S. barbata) has been reported to exhibit anti-cancer and anti-inflammation activities. The ethanol extract of S. barbata has been confirmed to attenuate diabetic retinopathy (DR). This study aimed to investigate the effects and underlying mechanisms of the polysaccharides isolated from S. barbata (PSB) on the proliferation and angiogenesis of retinal vascular endothelial cells (RVECs) in DR.

METHODS

Human RVECs (HRVECs) were cultured in normal glucose (NG, 5.5 mM), mannitol (MA, 30 mM), high glucose (HG, 30 mM) and HG plus 40 μg/mL PSB, respectively. Then, cell proliferation, migration and angiogenesis were evaluated. The cell proliferation was also estimated in the presence of SLIGKV, which was used to induce the phosphorylation of ERK (p-ERK).

RESULTS

PSB reduced normal and HG-induced HRVECs cell viability in a concentration-dependent manner. The protein expression of proliferating cell nuclear antigen (PCNA) and proliferating antigen KI67 (Ki67), the migration rate and tube formation ability, which were increased by HG treatment, were significantly decreased by PSB. PSB also inhibited the phosphorylation of Raf, MEK and ERK in HG-stimulated HRVECs. Moreover, the application of SLIGKV recovered cell viability and the expression of p-ERK, PCNA and Ki67, in HG plus PSB-treated cells. Finally, the HG-enhanced expression of VE-cadherin, Frizzed, β-catenin, MMP-2 and MMP-9 was all reversed by PSB.

CONCLUSION

PSB could inhibit HG-induced HRVECs proliferation, migration and neovascularization, and these effects might work through blocking the activation of MEK/ERK pathway and VEGF/VE-cadherin axis.

Multifocal Electroretinogram Can Detect the Abnormal Retinal Change in Early Stage of type2 DM Patients without Apparent Diabetic Retinopathy

PURPOSE

To study retinal function defects in type 2 diabetic patients without clinically apparent retinopathy using a multifocal electroretinogram (mf-ERG).

METHODS

Seventy-six eyes of thirty-eight type 2 diabetes mellitus(DM) patients without clinically apparent retinopathy and sixty-four normal eyes of thirty-two healthy control (HC) participants were examined using mf-ERG.

RESULTS

Patients with type 2 DM without apparent diabetic retinopathy demonstrated an obvious implicit time delay of P1 in ring 1, ring 3, and ring 5 compared with healthy controls (t = 5.184, p ≤ 0.001; t = 8.077, p ≤ 0.001; t = 2.000, p = 0.047, respectively). The implicit time (IT) in ring 4 of N1wave was significantly delayed in the DM group (t = 2.327, p = 0.021). Compared with the HC group, the implicit time of the P1 and N1 waves in the temporal retina zone was significantly prolonged (t = 3.66, p ≤ 0.001; t = 2.187, p = 0.03, respectively). And the amplitude of P1 in the temporal retina decreased in the DM group, which had a significantly statistical difference with the healthy controls (t = -6.963, p ≤ 0.001). However, there were no differences in either the amplitude of the response or the implicit time of the nasal retina zone between DM and HC. The AUC of multiparameters of mf-ERG was higher in the diagnosis of DR patients.

CONCLUSIONS

Patients with type 2 DM without clinically apparent retinopathy had a delayed implicit time of P1 wave in temporal regions of the postpole of the retina compared with HC subjects. It demonstrates that mf-ERG can detect the abnormal retinal change in the early stage of type2 DM patients without apparent diabetic retinopathy. Multiparameters of mf-ERG can improve the diagnostic efficacy of DR, and it may be a potential clinical biomarker for early diagnosis of DR.

CircASH2L Promotes Ovarian Cancer Tumorigenesis, Angiogenesis, and Lymphangiogenesis by Regulating the miR-665/VEGFA Axis as a Competing Endogenous RNA

Ovarian cancer is the leading cause of gynecologic cancer-related deaths. Emerging research has revealed a close relationship between circular RNAs (circRNAs) and ovarian cancer development, metastasis, and prognosis. The objective of our research was to further explore the relationship between circASH2L and ovarian cancer. Quantitative real-time polymerase chain reaction was used to detect the differential expression of circRNAs between normal ovaries and ovarian cancer tissues. The impact of circASH2L on the proliferation, invasion, and tumorigenicity of ovarian cancer cells was evaluated using gain- and loss-of-function experiments. The molecular mechanisms of circASH2L function were investigated using bioinformatics analysis, RNA fluorescence in situ hybridization, western blots, and dual-luciferase reporter assays. The results showed that circASH2L was remarkably upregulated in ovarian cancer. The invasion and growth of ovarian cancer cells were suppressed by circASH2L knockdown in vitro, and downregulation of circASH2L restrained both angiogenesis and lymphangiogenesis of tumor xenografts in vivo. Furthermore, circASH2L was mostly distributed in the cytoplasm, where it competes with vascular endothelial growth factor A (VEGFA) for binding to miR-665. These findings indicate that circASH2L has an oncogenic function in ovarian cancer. In conclusion, circASH2L plays a critical role in regulating ovarian cancer cell tumorigenesis, angiogenesis, and lymphangiogenesis through the miR-665/VEGFA axis and, therefore, is a possible candidate target for ovarian cancer treatment.

Comparison of aqueous humor levels of PlGF and VEGF in proliferative diabetic retinopathy before and after intravitreal conbercept injection

AIMS

The aim of this paper is to observe the change of aqueous humor levels of placenta growth factor (PlGF) and vascular endothelial growth factor (VEGF) in proliferative diabetic retinopathy (PDR) patients before and one week after intravitreal conbercept injection.

METHODS

A prospective case series study was conducted in 24 active PDR patients (24 eyes). All the patients had received 0.5 mg of intravitreal conbercept followed by vitrectomy one week later. The aqueous humor was collected before conbercept injection and at the beginning of vitrectomy.

RESULTS

Before conbercept injection, the aqueous humor median levels of VEGF-A, VEGF-B and PlGF were457.0pg/mL(IQRfrom392.9to860.6pg/mL), 43.6pg/mL(IQRfrom33.6to81.6pg/mL), 37.5pg/mL(IQRfrom25.0to53.6pg/mL), respectively. One week after conbercept injection, the aqueous humor levels of VEGF-A, VEGF-B and PiGF decreased significantly. The aqueous humor VEGF-A levels in PDR patients with fibrovascular membranes were lower than those without them. There was positive correlation between aqueous humor VEGF-B and PiGF levels (P = 0.007). No significant correlation was found between VEGF-A and PiGF levels. No ocular and systemic adverse events were observed.

CONCLUSIONS

The aqueous humor levels of PlGF was correlated with VEGF-B, and levels of VEGF-A, VEGF-B, and PlGF decreased after intravitreal conbercept injection in active PDR patients.

The Inhibitory Effects of Gold Nanoparticles on VEGF-A-Induced Cell Migration in Choroid-Retina Endothelial Cells

Background: Vascular endothelial growth factor (VEGF) is upregulated by hypoxia and is a crucial stimulator for choroidal neovascularization (CNV) in age-related macular degeneration and pathologic myopia, as well as retinal neovascularization in proliferative diabetic retinopathy. Retinal and choroidal endothelial cells play key roles in the development of retinal and CNV, and subsequent fibrosis. At present, the effects of gold nanoparticles (AuNPs) on the VEGF-induced choroid-retina endothelial (RF/6A) cells are still unknown. In our study, we investigated the effects of AuNPs on RF/6A cell viabilities and cell adhesion to fibronectin, a major ECM protein of fibrovascular membrane. Furthermore, the inhibitory effects of AuNPs on RF/6A cell migration induced by VEGF and its signaling were studied. Methods: The cell viability assay was used to determine the viability of cells treated with AuNPs. The migration of RF/6A cells was assessed by the Transwell migration assay. The cell adhesion to fibronectin was examined by an adhesion assay. The VEGF-induced signaling pathways were determined by western blotting. Results: The 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) viability assay revealed no cytotoxicity of AuNPs on RF/6A cells. AuNPs inhibited VEGF-induced RF/6A cell migration in a concentration-dependent manner but showed no significant effects on RF/6A cell adhesion to fibronectin. Inhibitory effects of AuNPs on VEGF-induced Akt/eNOS were found. Conclusions: These results suggest that AuNPs are an effective inhibitor of VEGF-induced RF/6A cell migration through the Akt/eNOS pathways, but they have no effects on their cell viabilities and cell adhesion to fibronectin.

Distinct downstream signaling and the roles of VEGF and PlGF in high glucose-mediated injuries of human retinal endothelial cells in culture

Vascular endothelial growth factor (VEGF) and placental growth factor (PlGF) plays a crucial role in breakdown of the blood-retinal barrier due to hyperpermeability in diabetic retinopathy (DR). However, the distinct signaling driven by VEGF and PlGF in the pathogenesis of DR remains unclear. In this study, we investigated VEGF- and PlGF- related signaling pathways and their roles in cultured human microvascular retinal endothelial cells (hRECs) under high glucose conditions (HG; 25 mM). Apoptotic cell death was evaluated, and FITC conjugated bovine serum albumin across monolayer hRECs served as an index of permeability. Western blots were used to assess the protein levels of VEGF and PlGF, as well as the phosphorylation of p38MAPK, STAT1 and Erk1/2. Knockdown of VEGF and PlGF was performed by using siRNA. Following HG treatment, increases of VEGF and PlGF as well as PKC activity were detected in hRECs. Increased phosphorylations of p38MAPK^{Thr180/Thr182}, STAT1^Ser727, and Erk1/2^{Tyr202/Tyr185} as well as VEGFR1^Tyr1213 and VEGFR2^Tyr1175 were also detected in HG-treated hRECs. Inhibition of PKC activity by Go 6976 prevented HG-induced increases of phosphor-Erk1/2 and nitric oxide synthase (NOS1) expressions as well as hyperpermeability, whereas inhibition of p38MAPK pathway by SB203580 selectively suppressed activation of STAT1 and decreased apoptotic cell death under HG conditions. Moreover, VEGF knockdown predominantly inhibited activation of VEGFR2, and phosphorylation of p38MAPK and STAT1, as well as apoptotic cell death in HG-treated hRECs. Nevertheless, PlGF knockdown mainly suppressed phosphorylation of VEGFR1, PKC, and Erk1/2, as well as NOS1 expressions and hyperpermeability. Taken together, we provide evidence demonstrating that HG-induced elevation of PlGF is responsible for hyperpermeability mainly through increasing activation of PKC-Erk1/2-NOS axis via VEGFR1, while HG-induced elevation of VEGF is associated with induction of apoptotic cell death mainly through increasing activation of p38MAPK/STAT1 signaling via VEGFR2.

Sustained intraocular vascular endothelial growth factor neutralisation does not affect retinal and choroidal vasculature in Ins2Akita diabetic mice

The purpose of this study was to understand the influence of sustained intravitreal vascular endothelial growth factor neutralisation on the retinal and choroidal vasculature in diabetic eyes. Ins2^Akita diabetic mice received five intravitreal injections of anti-mouse vascular endothelial growth factor antibody or goat immunoglobulin G (0.2 µg/µL/eye) over a 4-month period. Retinal and choroidal vascular changes were analysed by confocal microscopy of tissue flat-mounts. Retinal gene expression of vascular endothelial growth factor family members (vascular endothelial growth factors A, B, C and D), vascular endothelial growth factor receptors (sVEGFR-1 and VEGFR-2) and tight junctions (claudin 1, 2, 5; occludin and zonula occludens-1) were analysed by quantitative reverse transcription polymerase chain reaction. Vascular endothelial growth factor A and claudin 5 were significantly increased in diabetic retinae. Gene expression was unaffected by anti-vascular endothelial growth factor treatment. The number of acellular vessels was increased in diabetic retinae and reduced following anti-vascular endothelial growth factor treatment. Retinal and choroidal vascular density and area were unaffected by sustained vascular endothelial growth factor neutralisation. Our results suggest that five consecutive intravitreal anti-vascular endothelial growth factor injections do not cause significant vascular changes in the retina and choroid in diabetic and non-diabetic mice.

Vascular alteration in relation to fosfomycine: In silico and in vivo investigations using a chick embryo model

Fosfomycin residues are found in the egg following administration in the layer hen. In this regard, some aspects of embryo-toxicity of fosfomycin have been documented previously. The exact mechanism by which fosfomycin causes embryo-toxicity is not clearly understood. We hypothesis that fosfomycin may alter vasculature as well as normal expression of genes, which are associated with vascular development. Therefore, the present study aimed to address these issues through in silico and in vivo investigations. At first, embryo-toxicity and anti-angiogenic effects of fosfomycin were tested using computerized programs. After that, fertile chicken eggs were treated with fosfomycin and chorioallantoic membrane vasculature was assessed through morphometric, molecular and histopathological assays. The results showed that fosfomycin not only interacted with VEGF-A protein and promoter, but also altered embryonic vasculature and decreased expression level of VEGF-A. Reticulin staining of treated group was also confirmed decreased vasculature. The minor groove of DNA was the preferential binding site for fosfomycin with its selective binding to GC-rich sequences. We suggested that the affinity of fosfomycin for VEGF-A protein and promoter as well as alteration of the angiogenic signaling pathway may cause vascular damage during embryonic growth. Hence, veterinarians should be aware of such effects and limit the use of this drug during the developmental stages of the embryo, particularly in breeder farms. Considering the anti-angiogenic activity and sequence selectivity of fosfomycin, a major advantage that seems to be very promising is the fact that it is possible to achieve a sequence-selective binding drug for cancer.

The role of placental growth factor (PlGF) and its receptor system in retinal vascular diseases

Placental growth factor (PlGF) is a member of the vascular endothelial growth factor (VEGF) family. Upon binding to VEGF- and neuropilin-receptor sub-types, PlGF modulates a range of neural, glial and vascular cell responses that are distinct from VEGF-A. As PlGF expression is selectively associated with pathological angiogenesis and inflammation, its blockade does not affect the healthy vasculature. PlGF actions have been extensively described in tumor biology but more recently there has been accumulating preclinical evidence that indicates that this growth factor could have an important role in retinal diseases. High levels of PlGF have been found in aqueous humor, vitreous and/or retina of patients exhibiting retinopathies, especially those with diabetic retinopathy (DR) and neovascular age-related macular degeneration (nvAMD). Expression of this growth factor seems to correlate closely with many of the key pathogenic features of early and late retinopathy in preclinical models. For example, studies using genetic modification and/or pharmacological treatment to block PlGF in the laser-induced choroidal neovascularization (CNV) model, oxygen-induced retinopathy model, as well as various murine diabetic models, have shown that PlGF deletion or inhibition can reduce neovascularization, retinal leakage, inflammation and gliosis, without affecting vascular development or inducing neuronal degeneration. Moreover, an inhibitory effect of PlGF blockade on retinal scarring in the mouse CNV model has also been recently demonstrated and was found to be unique for PlGF inhibition, as compared to various VEGF inhibition strategies. Together, these preclinical results suggest that anti-PlGF therapy might have advantages over anti-VEGF treatment, and that it may have clinical applications as a standalone treatment or in combination with anti-VEGF. Additional clinical studies are clearly needed to further elucidate the role of PlGF and its potential as a therapeutic target in ocular diseases.

Pathophysiology of Diabetic Retinopathy: The Old and the New

Vision loss in diabetic retinopathy (DR) is ascribed primarily to retinal vascular abnormalities-including hyperpermeability, hypoperfusion, and neoangiogenesis-that eventually lead to anatomical and functional alterations in retinal neurons and glial cells. Recent advances in retinal imaging systems using optical coherence tomography technologies and pharmacological treatments using anti-vascular endothelial growth factor drugs and corticosteroids have revolutionized the clinical management of DR. However, the cellular and molecular mechanisms underlying the pathophysiology of DR are not fully determined, largely because hyperglycemic animal models only reproduce limited aspects of subclinical and early DR. Conversely, non-diabetic mouse models that represent the hallmark vascular disorders in DR, such as pericyte deficiency and retinal ischemia, have provided clues toward an understanding of the sequential events that are responsible for vision-impairing conditions. In this review, we summarize the clinical manifestations and treatment modalities of DR, discuss current and emerging concepts with regard to the pathophysiology of DR, and introduce perspectives on the development of new drugs, emphasizing the breakdown of the blood-retina barrier and retinal neovascularization.

Dendrobium nobile Lindley and its bibenzyl component moscatilin are able to protect retinal cells from ischemia/hypoxia by dowregulating placental growth factor and upregulating Norrie disease protein

Background

Presumably, progression of developmental retinal vascular disorders is mainly driven by persistent ischemia/hypoxia. An investigation into vision-threatening retinal ischemia remains important. Our aim was to evaluate, in relation to retinal ischemia, protective effects and mechanisms of Dendrobium nobile Lindley (DNL) and its bibenzyl component moscatilin. The therapeutic mechanisms included evaluations of levels of placental growth factor (PLGF) and Norrie disease protein (NDP).

Methods

An oxygen glucose deprivation (OGD) model involved cells cultured in DMEM containing 1% O₂, 94% N₂ and 0 g/L glucose. High intraocular pressure (HIOP)-induced retinal ischemia was created by increasing IOP to 120 mmHg for 60 min in Wistar rats. The methods included electroretinogram (ERG), histopathology, MTT assay and biochemistry.

Results

When compared with cells cultured in DMEM containing DMSO (DMSO+DMEM), cells subjected to OGD and pre-administrated with DMSO (DMSO+OGD) showed a significant reduction in the cell viability and NDP expression. Moreover, cells that received OGD and 1 h pre-administration of 0.1 μM moscatilin (Pre-OGD Mos 0.1 μM) showed a significant counteraction of the OGD-induced decreased cell viability. Furthermore, compared with the DMSO+OGD group (44.54 ± 3.15%), there was significant elevated NDP levels in the Pre-OGD Mos 0.1 μM group (108.38 ± 29.33%). Additionally, there were significant ischemic alterations, namely reduced ERG b-wave, less numerous retinal ganglion cells, decreased inner retinal thickness, and reduced/enhanced amacrine’s ChAT/Müller’s GFAP or vimentin immunolabelings. Moreover, there were significantly increased protein levels of HIF-1α, VEGF, PKM2, RBP2 and, particularly, PLGF (pg/ml; Sham vs. Vehicle: 15.11 ± 1.58 vs. 39.53 ± 5.25). These ischemic effects were significantly altered when 1.0 g/Kg/day DNL (DNL1.0 + I/R or I/R+ DNL1.0) was applied before and/or after ischemia, but not vehicle (Vehicle+I/R). Of novelty and significance, the DNL1.0 action mechanism appears to be similar to that of the anti-PLGF Eylea [PLGF (pg/ml); DNL1.0 vs. Eylea+I/R: 19.93 ± 2.24 vs. 6.44 ± 0.60].

Conclusions

DNL and moscatilin are able to protect against retinal ischemic/hypoxic changes respectively by downregulating PLGF and upregulating NDP. Progression of developmental retinal vascular disorders such as Norrie disease due to persistent ischemia/hypoxia might be thus prevented.

Electronic supplementary material

The online version of this article (10.1186/s12906-018-2256-z) contains supplementary material, which is available to authorized users.