Inhibition of choroidal and corneal pathologic neovascularization by Plgf1-de gene transfer

Sustained and Efficient Delivery of Antivascular Endothelial Growth Factor by the Adeno-associated Virus for the Treatment of Corneal Neovascularization: An Outlook for Its Clinical Translation

Corneal diseases represent 5.1% of all eye defects and are the fourth leading cause of blindness globally. Corneal neovascularization can arise from all conditions of chronic irritation or hypoxia, which disrupts the immune-privileged state of the healthy cornea, increases the risk of rejection after keratoplasty, and leads to opacity. In the past decades, significant progress has been made for neovascular diseases of the retina and choroid, with plenty of drugs getting commercialized. In addition, to overcome the barriers of the short duration and inadequate penetration of conventional formulations of antivascular endothelial growth factor (VEGF), multiple novel drug delivery systems, including adeno-associated virus (AAV)-mediated transfer have gone through the full process of bench-to-bedside translation. Like retina neovascular diseases, corneal neovascularization also suffers from chronicity and a high risk of recurrence, necessitating sustained and efficient delivery across the epithelial barrier to reach deep layers of the corneal stroma. Among the explored methods, adeno-associated virus-mediated delivery of anti-VEGF to treat corneal neovascularization is the most extensively researched and most promising strategy for clinical translation although currently although, it remains predominantly at the preclinical stage. This review comprehensively examines the necessity, benefits, and risks of applying AAV vectors for anti-VEGF drug delivery in corneal vascularization, including its current progress and challenges in clinical translation.

Nanotechnology-based ocular drug delivery systems: recent advances and future prospects

Ocular drug delivery has constantly challenged ophthalmologists and drug delivery scientists due to various anatomical and physiological barriers. Static and dynamic ocular barriers prevent the entry of exogenous substances and impede therapeutic agents' active absorption. This review elaborates on the anatomy of the eye and the associated constraints. Followed by an illustration of some common ocular diseases, including glaucoma and their current clinical therapies, emphasizing the significance of drug therapy in treating ocular diseases. Subsequently, advances in ocular drug delivery modalities, especially nanotechnology-based ocular drug delivery systems, are recommended, and some typical research is highlighted. Based on the related research, systematic and comprehensive characterizations of the nanocarriers are summarized, hoping to assist with future research. Besides, we summarize the nanotechnology-based ophthalmic drugs currently on the market or still in clinical trials and the recent patents of nanocarriers. Finally, inspired by current trends and therapeutic concepts, we provide an insight into the challenges faced by novel ocular drug delivery systems and further put forward directions for future research. We hope this review can provide inspiration and motivation for better design and development of novel ophthalmic formulations.

4-(2-Butyl-6,7-dichloro-2-cyclopentyl-indan-1-on-5-yl) oxobutyric acid inhibits angiogenesis via modulation of vascular endothelial growth factor receptor 2 signaling pathway

4-(2-Butyl-6,7-dichloro-2-cyclopentyl-indan-1-on-5-yl) oxobutyric acid (DCPIB), was discovered to be a potent and specific antagonist of volume-regulated anion channel that is closely linked to angiogenesis. However, the effect of DCPIB on angiogenesis remains unclear. Here, we found that DCPIB inhibited angiogenesis in the corneal suture and myocardial infarction in vivo model. In addition, DCPIB inhibited human umbilical vein endothelial cell migration, tube formation and proliferation in vitro. Moreover, DCPIB repressed the activation and expression of vascular endothelial growth factor receptor 2 (VEGFR2) and its downstream signaling pathway. Computer modeling further confirmed that DCPIB binds with high affinity to VEGFR2. Collectively, we present evidence supporting an antiangiogenic role of DCPIB by targeting VEGFR2 signaling pathway, which suggests that DCPIB is a valuable lead compound for the treatment of angiogenesis-related diseases.

Gene therapy in the anterior eye segment

This review provides comprehensive information about the advances in gene therapy in the anterior segment of the eye including cornea, conjunctiva, lacrimal gland, and trabecular meshwork. We discuss gene delivery systems including viral and non-viral vectors as well as gene editing techniques, mainly CRISPR-Cas9, and epigenetic treatments including antisense and siRNA therapeutics. We also provide a detailed analysis of various anterior segment diseases where gene therapy has been tested with corresponding outcomes. Disease conditions include corneal and conjunctival fibrosis and scarring, corneal epithelial wound healing, corneal graft survival, corneal neovascularization, genetic corneal dystrophies, herpetic keratitis, glaucoma, dry eye disease, and other ocular surface diseases. Although most of the analyzed results on the use and validity of gene therapy at the ocular surface have been obtained in vitro or using animal models, we also discuss the available human studies. Gene therapy approaches are currently considered very promising as emerging future treatments of various diseases, and this field is rapidly expanding.

Mechanisms of protection of retinal pigment epithelial cells from oxidant injury by humanin and other mitochondrial-derived peptides: Implications for age-related macular degeneration

The mitochondrial-derived peptides (MDPs) are a new class of small open reading frame encoded polypeptides with pleiotropic properties. The prominent members are Humanin (HN) and small HN-like peptide (SHLP) 2, which encode 16S rRNA, while mitochondrial open reading frame of the twelve S c (MOTS-c) encodes 12S rRNA of the mitochondrial genome. While the multifunctional properties of HN and its analog 14-HNG have been well documented, their protective role in the retinal pigment epithelium (RPE)/retina has been investigated only recently. In this review, we have summarized the multiple effects of HN and its analogs, SHLP2 and MOTS-c in oxidatively stressed human RPE and the regulatory pathways of signaling, mitochondrial function, senescence, and inter-organelle crosstalk. Emphasis is given to the mitochondrial functions such as biogenesis, bioenergetics, and autophagy in RPE undergoing oxidative stress. Further, the potential use of HN and its analogs in the prevention of age-related macular degeneration (AMD) are also presented. In addition, the role of novel, long-acting HN elastin-like polypeptides in nanotherapy of AMD and other ocular diseases stemming from oxidative damage is discussed. It is expected MDPs will become a promising group of mitochondrial peptides with valuable therapeutic applications in the treatment of retinal diseases.

Co-inhibition of PGF and VEGF blocks their expression in mononuclear phagocytes and limits neovascularization and leakage in the murine retina

Background

Age-related macular degeneration (AMD) is a leading cause of visual impairment in the elderly. The neovascular (wet) form of AMD can be treated with intravitreal injections of different anti-vascular endothelial growth factor (VEGF) agents. Placental growth factor (PGF) is another member of the VEGF family of cytokines with pro-angiogenic and pro-inflammatory effects. Here, we aimed to compare single and combined inhibition of VEGF-A and PGF in the laser-induced mouse model of choroidal neovascularization (CNV) with a focus on the effects on retinal mononuclear phagocytes.

Methods

CNV was induced in C57BL/6J mice using a YAG-Laser. Immediately after laser damage antibodies against VEGF-A (aVEGF), anti-PGF (aPGF), aVEGF combined with aPGF, aflibercept, or IgG control were injected intravitreally in both eyes. Three and 7 days after laser damage, the vascular leakage was determined by fluorescence angiography. Lectin staining of retinal and RPE/choroidal flat mounts was used to monitor CNV. In situ mRNA co-expression of Iba1, VEGF and PGF were quantified using in situ hybridization. Retinal and RPE/choroidal protein levels of VEGF and PGF as well as the pro-inflammatory cytokines IL-6, IL1-beta, and TNF were determined by ELISA.

Results

Early (day 3) and intermediate (day 7) vascular leakage and CNV were significantly inhibited by PGF and VEGF-A co-inhibition, most effectively with the trap molecule aflibercept. While VEGF-A blockage alone had no effects, trapping PGF especially with aflibercept prevented the accumulation of reactive microglia and macrophages in laser lesions. The lesion-related mRNA expression and secretion of VEGF-A and PGF by mononuclear phagocytes were potently suppressed by PGF and partially by VEGF-A inhibition. Protein levels of IL-6 and IL1-beta were strongly reduced in all treatment groups.

Conclusions

Retinal inhibition of PGF in combination with VEGF-A prevents vascular leakage and CNV possibly via modulating their own expression in mononuclear phagocytes. PGF-related, optimized strategies to target inflammation-mediated angiogenesis may help to increase efficacy and reduce non-responders in the treatment of wet AMD patients.

Electronic supplementary material

The online version of this article (10.1186/s12974-019-1419-2) contains supplementary material, which is available to authorized users.

Placental growth factor and its potential role in diabetic retinopathy and other ocular neovascular diseases

The role of vascular endothelial growth factor (VEGF), including in retinal vascular diseases, has been well studied, and pharmacological blockade of VEGF is the gold standard of treatment for neovascular age‐related macular degeneration, retinal vein occlusion and diabetic macular oedema. Placental growth factor (PGF, previously known as PlGF), a homologue of VEGF, is a multifunctional peptide associated with angiogenesis‐dependent pathologies in the eye and non‐ocular conditions. Animal studies using genetic modification and pharmacological treatment have demonstrated a mechanistic role for PGF in pathological angiogenesis. Inhibition decreases neovascularization and microvascular abnormalities across different models, including oxygen‐induced retinopathy, laser‐induced choroidal neovascularization and in diabetic mice exhibiting retinopathies. High levels of PGF have been found in the vitreous of patients with diabetic retinopathy. Despite these strong animal data, the exact role of PGF in pathological angiogenesis in retinal vascular diseases remains to be defined, and the benefits of PGF‐specific inhibition in humans with retinal neovascular diseases and macular oedema remain controversial. Comparative effectiveness research studies in patients with diabetic retinal disease have shown that treatment that inhibits both VEGF and PGF may provide superior outcomes in certain patients compared with treatment that inhibits only VEGF. This review summarizes current knowledge of PGF, including its relationship to VEGF and its role in pathological angiogenesis in retinal diseases, and identifies some key unanswered questions about PGF that can serve as a pathway for future basic, translational and clinical research.

Epithelium-derived miR-204 inhibits corneal neovascularization

MicroRNA-204 (miR-204) is highly expressed in cornea, here we explored the role and mechanism of miR-204 in corneal neovascularization (CNV). Mouse CNV was induced by intrastromal placement of suture in BALB/c mice with the subconjunctival injection of miR-204 agomir or negative control. Human primary limbal epithelial cells (LECs) and immortalized microvascular endothelial cells (HMECs) were used to evaluate the expression changes and anti-angiogenic effects of miR-204 under biomechanical stress (BS). The expression and localization of miR-204, vascular endothelial growth factor (VEGF) and their receptors were detected by quantitative real-time PCR, in situ hybridization, immunohistochemistry and Western blot. The results showed that miR-204 expression was mainly localized in epithelium and down-expressed in vascularized cornea. Subconjunctival injection of miR-204 agomir inhibited CNV and reduced the expression of VEGF and VEGF receptor 2. Similarly, miR-204 overexpression attenuated the increased expression of VEGF by biomechanical stress in LECs, and suppressed the proliferation, migration, and tube formation of HMECs. These novel findings indicate that epithelium-derived miR-204 inhibits suture-induced CNV through regulating VEGF and VEGF receptor 2.

Influences of placental growth factor on mouse retinal vascular development

BACKGROUND

Placental growth factor (PGF) is important for wound-healing and vascular collaterogenesis. PGF deficiency is associated with preeclampsia, a hypertensive disease of human pregnancy. Offspring born to preeclamptic mothers display cognitive impairments and brain vascular and neurostructural deviations. Low PGF production during development may contribute to alterations in offspring cerebrovascular beds. Retina is a readily accessible part of the central nervous system with a well-described pattern of vascular development in mice. Impacts of PGF deficiency were addressed during mouse retinal vascularization.

RESULTS

Retinal vessels were compared between Pgf^-/- and congenic C57BL/6 (B6) mice. PGF deficiency altered neonatal retinal vascularization patterns. Some anatomic alterations persisted into adulthood, particularly in males. Greater arterial wall collagen IV expression was found in adult Pgf^-/- females. Pregnancy (studied in adult females at gestational days 11.5 or 18.5) induced subtle changes upon the mother's retinal vasculature but these pregnancy-induced changes did not differ between genotypes. Significant sex-related differences occurred between adult male and female B6 although sexually dimorphic retinal vascular differences were absent in B6 neonates.

CONCLUSIONS

Overall, PGF has a role in retinal vascular angiogenesis and vessel organization during development but does not affect retinal vessel adaptations in adult females during pregnancy. Developmental Dynamics 246:700-712, 2017. © 2017 Wiley Periodicals, Inc.

Osmotic induction of placental growth factor in retinal pigment epithelial cells in vitro: contribution of NFAT5 activity

One risk factor of neovascular age-related macular degeneration is systemic hypertension; hypertension is mainly caused by extracellular hyperosmolarity after consumption of dietary salt. In retinal pigment epithelial (RPE) cells, high extracellular osmolarity induces vascular endothelial growth factor (VEGF)-A (Hollborn et al. in Mol Vis 21:360-377, 2015). The aim of the present study was to determine whether extracellular hyperosmolarity and chemical hypoxia trigger the expression of further VEGF family members including placental growth factor (PlGF) in human RPE cells. Hyperosmotic media were made up by addition of 100 mM NaCl or sucrose. Chemical hypoxia was induced by CoCl2. Gene expression was quantified by real-time RT-PCR, and secretion of PlGF-2 was investigated with ELISA. Nuclear factor of activated T cell 5 (NFAT5) was depleted using siRNA. Extracellular hyperosmolarity triggered expression of VEGF-A, VEGF-D, and PlGF genes, and secretion of PlGF-2. Hypoosmolarity decreased PlGF gene expression. Hypoxia induced expression of VEGF-A, VEGF-B, VEGF-D, and PlGF genes. Extracellular hyperosmolarity and hypoxia produced additive PlGF gene expression. Both hyperosmolarity and hypoxia induced expression of KDR and FLT-4 receptor genes, while hyperosmolarity caused neuropilin-2 and hypoxia neuropilin-1 gene expression. The hyperosmotic, but not the hypoxic, PlGF gene expression was in part mediated by NFAT5. The expression of PlGF in RPE cells depends on the extracellular osmolarity. The data suggest that high consumption of dietary salt may exacerbate the angiogenic response of RPE cells in the hypoxic retina via transcriptional activation of various VEGF family member genes.

AAV2 delivery of Flt23k intraceptors inhibits murine choroidal neovascularization

Long-term inhibition of extracellular vascular endothelial growth factor (VEGF) in the treatment of age-related macular degeneration (AMD) may induce retinal neuronal toxicity and risk other side effects. We developed a novel strategy which inhibits retinal pigment epithelium (RPE)-derived VEGF, sparing other highly sensitive retinal tissues. Flt23k, an intraceptor inhibitor of VEGF, was able to inhibit VEGF in vitro. Adeno-associated virus type 2 (AAV2)-mediated expression of Flt23k was maintained for up to 6 months postsubretinal injection in mice. Flt23k was able to effectively inhibit laser-induced murine choroidal neovascularization (CNV). VEGF levels in the RPE/choroid complex decreased significantly in AAV2.Flt23k treated eyes. Neither retinal structure detected by Heidelberg Spectralis nor function measured by electroretinography (ERG) was adversely affected by treatment with AAV2.Flt23k. Hence AAV2.Flt23k can effectively maintain long-term expression and inhibit laser-induced CNV in mice through downregulation of VEGF while maintaining a sound retinal safety profile. These findings suggest a promising novel approach for the treatment of CNV.

Enhanced wound healing, kinase and stem cell marker expression in diabetic organ-cultured human corneas upon MMP-10 and cathepsin F gene silencing

PURPOSE

Diabetic corneas overexpress proteinases including matrix metalloproteinase-10 (M10) and cathepsin F (CF). Our purpose was to assess if silencing M10 and CF in organ-cultured diabetic corneas using recombinant adenovirus (rAV)-driven small hairpin RNA (rAV-sh) would normalize slow wound healing, and diabetic and stem cell marker expression.

METHODS

Sixteen pairs of organ-cultured autopsy human diabetic corneas (four per group) were treated with rAV-sh. Proteinase genes were silenced either separately, together, or both, in combination (Combo) with rAV-driven c-met gene overexpression. Fellow control corneas received rAV-EGFP. Quantitative RT-PCR confirmed small hairpin RNA (shRNA) silencing effect. Ten days after transfection, 5-mm epithelial wounds were made with n-heptanol and healing time recorded. Diabetic, signaling, and putative stem cell markers were studied by immunofluorescence of corneal cryostat sections.

RESULTS

Proteinase silencing reduced epithelial wound healing time versus rAV-enhanced green fluorescent protein (EGFP) control (23% for rAV-shM10, 31% for rAV-shCF, and 36% for rAV-shM10 + rAV-shCF). Combo treatment was even more efficient (55% reduction). Staining patterns of diabetic markers (α₃β₁ integrin and nidogen-1), and of activated epidermal growth factor receptor and its signaling target activated Akt were normalized upon rAV-sh treatment. Combo treatment also restored normal staining for activated p38. All treatments, especially the combined ones, increased diabetes-altered staining for putative limbal stem cell markers, ΔNp63α, ABCG2, keratins 15 and 17, and laminin γ3 chain.

CONCLUSIONS

Small hairpin RNA silencing of proteinases overexpressed in diabetic corneas enhanced corneal epithelial and stem cell marker staining and accelerated wound healing. Combined therapy with c-met overexpression was even more efficient. Specific corneal gene therapy has a potential for treating diabetic keratopathy.