Fibrosis and diseases of the eye

Salinomycin and its derivatives - A new class of multiple-targeted "magic bullets"

The history of drug development clearly shows the scale of painstaking effort leading to a finished product - a highly biologically active agent that would be at the same time no or little toxic to human organism. Moreover, the aim of modern drug discovery can move from "one-molecule one-target" concept to more promising "one-molecule multiple-targets" one, particularly in the context of effective fight against cancer and other complex diseases. Gratifyingly, natural compounds are excellent source of potential drug leads. One of such promising naturally-occurring drug candidates is a polyether ionophore - salinomycin (SAL). This compound should be identified as multi-target agent for two reasons. Firstly, SAL combines a broad spectrum of bioactivity, including antibacterial, antifungal, antiviral, antiparasitic and anticancer activity, with high selectivity of action, proving its significant therapeutic potential. Secondly, the multimodal mechanism of action of SAL has been shown to be related to its interactions with multiple molecular targets and signalling pathways that are synergistic for achieving a therapeutic anticancer effect. On the other hand, according to the Paul Ehrlich's "magic bullet" concept, invariably inspiring the scientists working on design of novel target-selective molecules, a very interesting direction of research is rational chemical modification of SAL. Importantly, many of SAL derivatives have been found to be more promising as chemotherapeutics than the native structure. This concise review article is focused both on the possible role of SAL and its selected analogues in future antimicrobial and/or cancer therapy, and on the potential use of SAL as a new class of multiple-targeted "magic bullet" because of its multimodal mechanism of action.

Anatomical and functional changes in neovascular AMD in remission: comparison of fibrocellular and fibrovascular phenotypes

PURPOSE

To investigate the anatomical changes and the macular function in neovascular age-related macular degeneration (AMD) eyes, according to the recognition of either fibrocellular or fibrovascular phenotype.

METHODS

We enrolled eyes with previously treated neovascular AMD in remission (no subretinal haemorrhage, sign of fluid in or under the retina and no treatment for at least 6 months). Subjects underwent multimodal imaging assessment and were tested for macular sensitivity using microperimetry. The study cohort was divided according to the presence of fibrosis on multicolour (MC) images, yielding two distinct phenotypic subgroups: (1) fibrocellular group and (2) fibrovascular group.

RESULTS

Nineteen eyes were classified as fibrocellular on MC images, while 22 eyes as fibrovascular. Mean±SD age was 73.9±11.0 years in the fibrocellular group and 75.9±7.1 years in the fibrovascular group (p=0.221). Best-corrected visual acuity was 0.7±0.5 logarithm of the minimum angle of resolution (LogMAR) in the fibrocellular group and 0.3±0.2 LogMAR in the fibrovascular group (p=0.003). On the optical coherence tomography and fundus autofluorescence evaluation, 17/19 eyes with the fibrocellular phenotype and 8/22 eyes with the fibrovascular phenotype displayed the presence of retinal pigment epithelium (RPE) atrophy (p=0.001). The perfusion density within the neovascular lesion was 28.9%±9.9% in the fibrocellular group and 44.2%±5.9 % in the fibrovascular group (p<0.0001).

CONCLUSION

Neovascular AMD eyes in remission and with evidence of fibrocellular scar are characterised by RPE atrophy and reduced perfusion, which are associated with a higher degree of functional impairment. These findings suggest that maturation of vessels in fibrosis might be a better target in neovascular AMD treatments rather than their abolishment.

Stemness and Regenerative Potential of Corneal Stromal Stem Cells and Their Secretome After Long-Term Storage: Implications for Ocular Regeneration

Purpose

To assess the stemness and regenerative potential of cryopreserved corneal stromal stem cells (cryo-CSSCs) after long-term storage. We also used the secretome from these cells to observe the effect on wound-healing capacity of corneal fibroblasts and on the expression of fibrotic markers during wound healing.

Methods

CSSCs were obtained from three donors and stored in liquid nitrogen for approximately 10 years. Post thaw, cryo-CSSCs were characterized for stemness using phenotypic and genotypic markers along with colony-forming efficiency and three-dimensional spheroid formation. Multilineage differentiation was observed by differentiation into osteocytes, adipocytes, neural cells, and keratocytes. Secretome was harvested by culturing cryo-CSSCs in log phase. Wound-healing capacity was observed by live-cell time-lapse microscopy. Statistical analysis was done using 1-way ANOVA and Tukey posttest.

Results

CSSCs displayed good viability post thaw and showed >90% expression of stem cell markers CD90, CD73, CD105, STRO1, and CD166. cryo-CSSCs also expressed stem cell genes OCT4, KLF4, and ABCG2, and could also form colonies and three-dimensional spheroids. Multipotency assessment showed that all three cryo-CSSCs could differentiate into osteocytes, adipocytes, neural cells, as shown by β-III tubulin and neurofilament antibody staining and corneal keratocytes as observed by staining for Kera C, J19, and collagen V antibodies. The secretome derived from these three populations could promote the wound healing of corneal fibroblasts and reduce the expression of fibrotic markers SPARC and fibronectin.

Conclusions

CSSCs maintained their stemness and multipotency after long-term storage, and secretome derived from these cells can be of paramount importance for corneal regeneration and prevention of fibrosis.

Macular Features on Spectral-Domain Optical Coherence Tomography Imaging Associated With Visual Acuity in Coats' Disease

Purpose

To investigate the association between macular features on spectral-domain optical coherence tomography (SD-OCT) and visual acuity (VA) in Coats' disease.

Methods

Thirty-nine eyes (39 patients) with SD-OCT from January 1, 2008 to December 31, 2016 were reviewed for SD-OCT features. Central subfield (CSF) SD-OCT findings were analyzed relative to VA (logarithm of the minimum angle of resolution) at baseline and final visit (when follow-up ≥ 6 months) and across visits.

Results

Mean VA ± standard deviation at baseline (37 eyes) was 0.92 ± 0.82. SD-OCT features associated with worse VA included, for treatment-naïve eyes (n = 21), outer retinal atrophy (ORA) (1.18 ± 0.34 with versus 0.20 ± 0.30 without, P = 0.005), subretinal fluid (SRF) (1.80 ± 0.63 vs. 0.63 ± 0.50, P = 0.008), bright hyperreflectivities (1.23 ± 0.68 vs. 0.52 ± 0.53, P = 0.02), thicker foveal subretinal space (r² = 0.32, P = 0.01), and CSF (r² = 0.39, P = 0.007); and for previously treated eyes (n = 16), a compact hyperreflective structure (1.60 ± 0.88 vs. 0.56 ± 0.64, P = 0.02) and ORA (1.34 ± 0.86 vs. 0.30 ± 0.44, P = 0.01). At final follow-up (n = 22), mean VA was 0.81 ± 0.83. Eyes with final VA <20/200 (n = 6, vs. >20/60, n = 11) more commonly had a compact hyperreflective structure and ORA at baseline and final visit (P < 0.05). Mean change in VA from baseline (n = 20) was −0.20 ± 0.59. Mean improvement in VA (range, −0.525 to −1.127) occurred in eyes with baseline SRF (P = 0.02) and bright hyperreflectivities (P = 0.03). Changes in thickness that correlated with change in VA included those for the foveal subretinal space (r² = 0.52, P < 0.001) and CSF (r² = 0.26, P = 0.045).

Conclusions

A compact hyperreflective structure (fibrosis) and ORA were associated with poor final VA while SRF, bright hyperreflectivities (exudation), and foveal subretinal thickness were associated with VA improvement post treatment.

Statins in ophthalmology

Statins, 3-hydroxy-3-methyl-gutaryl coenzyme A reductase inhibitors, are a class of lipid-lowering drugs with anti-inflammatory, immunomodulatory, and vascular effects. Statins are increasingly being used in the treatment of a variety of medical conditions. We examine the actions of statins on the eye and its associated ophthalmic disorders. Statins can be synthetic or nonsynthetic, and their differentiating derivations may contribute to their varying cholesterol-lowering and pleiotropic effects. There is conflicting evidence on the ocular therapeutic and adverse effects of the statins. Statins may play a role in reducing the burden of dry eye, corneal ulcer scarring, thyroid-associated orbitopathy, glaucoma, uveitis and other associated ocular inflammatory states, cataract, proliferative vitreoretinopathy, diabetic retinopathy, macular degeneration, and choroidal melanoma. Topical preparations of statins can be formulated, thereby extending the range of ocular diseases that may be amenable to treatment. Statins have a relatively safe side effect profile, but rare and serious adverse reactions have been reported with their usage in ophthalmology, including myopathies and rhabdomyolysis with acute renal failure.

Autophagy resists EMT process to maintain retinal pigment epithelium homeostasis

Proliferative vitreoretinopathy (PVR) is the most serious fibrous complication that causes vision loss after intraocular surgery, and there is currently no effective treatment in clinical. Autophagy is an important cell biological mechanism in maintaining the homeostasis of tissues and cells, resisting the process of EMT. However, it is still unclear whether autophagy could resist intraocular fibrosis and prevent PVR progression. In this study, we investigated the expression of mesenchymal biomarkers in autophagy deficiency cells and found these proteins were increased. The mesenchymal protein transcription factor Twist can bind to autophagy related protein p62 and promote the degradation of Twist, which reduced the expression of mesenchymal markers. By constructing an EMT model of retinal pigment epithelial (RPE) cells in vitro, we found that autophagy was activated in the EMT process of RPE cells. Moreover, in autophagy deficient RPE cell line via knockdown autophagy related protein 7 (Atg7), the expression of epithelial marker claudin-1 was suppressed and the mesenchymal markers were increased, accompanied by an increase in cell migration and contractility. Importantly, RPE epithelial properties can be maintained by promoting autophagy and effectively reversing TFG-β2-induced RPE fibrosis. These observations reveal that autophagy may be an effective way to treat PVR.

Proliferative Vitreoretinopathy: A Review

Proliferative vitreoretinopathy (PVR) is the most common cause for failure of rhegmatogenous retinal detachment repair and is characterized by the growth and contraction of cellular membranes within the vitreous cavity and on both sides of the retinal surface as well as intraretinal fibrosis. Currently, PVR is thought to be an abnormal wound healing response that is primarily driven by inflammatory, retinal, and RPE cells. At this time, surgery is the only management option for PVR as there is no proven pharmacologic agent for the treatment or prevention of PVR. Laboratory research to better understand PVR pathophysiology and clinical trials of various agents to prevent PVR formation are ongoing.

Lymphatic Vascular Structures: A New Aspect in Proliferative Diabetic Retinopathy

Diabetic retinopathy (DR) is the most common diabetic microvascular complication and major cause of blindness in working-age adults. According to the level of microvascular degeneration and ischemic damage, DR is classified into non-proliferative DR (NPDR), and end-stage, proliferative DR (PDR). Despite advances in the disease etiology and pathogenesis, molecular understanding of end-stage PDR, characterized by ischemia- and inflammation-associated neovascularization and fibrosis, remains incomplete due to the limited availability of ideal clinical samples and experimental research models. Since a great portion of patients do not benefit from current treatments, improved therapies are essential. DR is known to be a complex and multifactorial disease featuring the interplay of microvascular, neurodegenerative, metabolic, genetic/epigenetic, immunological, and inflammation-related factors. Particularly, deeper knowledge on the mechanisms and pathophysiology of most advanced PDR is critical. Lymphatic-like vessel formation coupled with abnormal endothelial differentiation and progenitor cell involvement in the neovascularization associated with PDR are novel recent findings which hold potential for improved DR treatment. Understanding the underlying mechanisms of PDR pathogenesis is therefore crucial. To this goal, multidisciplinary approaches and new ex vivo models have been developed for a more comprehensive molecular, cellular and tissue-level understanding of the disease. This is the first step to gain the needed information on how PDR can be better evaluated, stratified, and treated.

Adiponectin: A potential candidate for treating fibrosis in posterior segment of the eye

Fibrosis in ocular tissues causes severe visual deterioration and blindness in patients with glaucoma, cataract, age related macular degeneration (AMD) and diabetic retinopathy (DR). Currently available anti-fibrotic agents exhibit undesirous cytotoxic effects and thus prove ineffective to treat post-surgical fibrosis. Accordingly, there is a need to develop efficient and novel anti-fibrotic agents. Adiponectin (APN), an adipokine from adipocytes is increased in the aqueous and vitreous humor of the patients with micro-angiopathy and chronic inflammation. Furthermore, it is reported to be elevated in the subretinal fluid, vitreous and epiretinal membrane of patients with AMD, proliferative vitreoretinopathy (PVR) and proliferative diabetic retinopathy (PDR) respectively. Since APN has anti-angiogenic activity and reduces VEGF levels, we hypothesize that APN might regulate the angio-fibrotic switch and drive the formation of fibrovascular membrane at advanced stages of AMD, PVR and PDR. Intriguingly, APN is shown to inhibit liver, cardiac and pulmonary fibrosis, yet it accelerates renal fibrosis. Therefore, the factors such as tissue and cell type, disease specific pathological milieu and the choice of APN receptor interaction could determine the pro- or anti-fibrotic nature of APN. We speculate that APN could play a profibrotic role in the posterior segment of the eye.

Supercontinuum source-based multi-contrast optical coherence tomography for rat retina imaging

This study proposed an ultrahigh-resolution multi-contrast optical coherence tomography system integrated with fundus photography for in vivo retinal imaging of rodents. A supercontinuum light source was used in the system, providing an axial resolution of less than 3 µm within 1.8 mm (in the tissue). Three types of tissue contrast based on backscattered intensity, phase retardation, and microvasculature at a capillary level can be simultaneously obtained using the proposed system. Pigmented Long-Evans, non-pigmented (albino) Sprague Dawley, and Royal College of Surgeons rats were imaged and compared. In vivo imaging results were validated with histology.

Histological investigation of human glaucomatous eyes: Extracellular fibrotic changes and galectin 3 expression in the trabecular meshwork and optic nerve head

Glaucoma is a leading cause of irreversible vision loss and is associated with fibrotic changes in two ocular tissues-the optic nerve head (ONH) and trabecular meshwork (TM). We investigated the differences in extracellular matrix components (ECM) including collagen, elastin, transforming growth factor beta-2, type-II receptor (TGFβRII) and Galectin3 (Gal3) in the glaucomatous human eyes to quantify fibrotic changes in ONH and TM. Glaucomatous and control human donor eyes were prepared for chemical and immunological staining to quantify ECM protein expression in the TM and ONH. Chemical staining included: Trichrome (collagen), Vernhoeff-Van Giesen (elastin) and Sirius Red (collagen). Immunohistochemistry was used to determine levels of Gal3 and TGFβ2RII. Quantitative analyses were performed using Image J software. Student's t-test was used to compare groups and Pearson's test was used to determine correlations P-values of 0.05 (or less) were considered statistically significant. Deposition of ECM proteins was elevated in glaucomatous tissues. There was increased collagen (P = 0.0469), Gal3 (P < 0.0001) and TGFβ2RII (P = 0.0005) in the TM of glaucomatous eyes. Likewise, collagen (P = 0.0517) and Galectin3 (P = 0.041) were increased in the ONH glaucomatous eyes. There was a correlation of TGFβRII with Gal3 in the TM (P < 0.0001) and optic nerve (P = 0.0003). The TM and ONH of glaucomatous eyes showed increased expression of ECM proteins supporting a fibrotic pathology. Galectin3 and TGFβ-2R II showed a positive correlation in TM and optic nerve supporting co-localization and suggesting their potential role in the glaucoma fibrotic process. Clin. Anat. 31:1031-1049, 2018. © 2018 The Authors. Clinical Anatomy published by Wiley Periodicals, Inc. on behalf of American Association of Clinical Anatomists.

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.

Correlation of transforming growth factor β-1 vitreous levels with clinical severity of proliferative vitreoretinopathy in patients with rhegmatogenous retinal detachment

OBJECTIVE

To correlate the vitreous concentration of transforming growth factor β-1 (TGF β-1) with the degree of clinical severity of proliferative vitreoretinopathy (PVR).

DESIGN

A prospective, observational, cross-sectional study carried out on cases and controls.

PARTICIPANTS

The study included 40 patients with a diagnosis of PVR secondary to rhegmatogenous retinal detachment.

METHODS

Vitreous was obtained in patients undergoing pars plana vitrectomy by rhegmatogenous retinal detachment, who were treated during the period from August 2015 to June 2016, in a national reference centre for ophthalmological care in Mexico City, Mexico. The levels of TGFβ-1 were quantified by ELISA technique. An ANOVA test was performed for the comparison of the different groups, together with a post-hoc Dunns test. A statistically significant difference was considered when obtaining P <.05.

RESULTS

The levels of TGFβ-1 were quantified, and the following means were found for each group: In the group with PVR grade A, 1150.6 ± 452.08 pg / ml, PVR grade B: 1129.6 ± 365.54 pg / ml, and PVR grade C: 1146.4 ± 330.21 pg / ml. The statistical analysis did not find significant differences when comparing the different PVR groups. (P=.53). However, when performing the differential analysis for each level of severity, a statistically significant increase in the expression of TGFβ-1 was observed in the group of patients with PVR-A at a greater number of days of evolution of the detachment. (P=.03). There were no statistically significant differences for PVR-B and PVR-C (P=.16 and P=.16, respectively).

CONCLUSION

Although the levels of TGFβ-1 are not directly related to the clinical severity grade, suggesting that there must be other factors involved in the advanced stages of PVR, TGFβ-1 may have greater relevance during the initial stages of the clinical course by promoting the epithelial-mesenchymal transition due to its greater expression in PVR-A. Thus, it can be concluded that each isoform plays a very particular role in the complex process of PVR.

Galectin-1 promotes choroidal neovascularization and subretinal fibrosis mediated via epithelial-mesenchymal transition

VEGFA and TGF-β are known major angiogenic and fibrogenic factors. Galectin-1, encoded by lectin, galactoside-binding, soluble ( LGALS) 1, has attracted growing attention for its facilitatory role in angiogenesis and fibrosis through its modification of VEGFA and TGF-β receptor signaling pathways. We reveal galectin-1 involvement in the mouse model of laser-induced choroidal neovascularization (CNV) and subretinal fibrosis, both of which represent the pathogenesis of age-related macular degeneration (AMD). Neither deletion nor overexpression of Lgals1 affected physiologic retinal development or visual function. Galectin-1/ Lgals1 was upregulated by CNV induction, whereas deletion of Lgals1 suppressed CNV together with downstream molecules of VEGF receptor (VEGFR)2. Loss of Lgals1 also attenuated subretinal fibrosis, expression of epithelial-mesenchymal transition (EMT) markers including Snai1, and phosphorylation of SMAD family member 2. Supporting these in vivo findings, silencing of LGALS1 in human retinal pigment epithelial (RPE) cells inhibited TGF-β1-induced EMT-related molecules and cell motilities. Conversely, overexpression of Lgals1 enhanced CNV and subretinal fibrosis. Specimens from patients with AMD demonstrated colocalization of galectin-1 with VEGFR2 in neovascular endothelial cells and with phosphorylated SMAD2 in RPE cells. These results suggested a biologic significance of galectin-1 as a key promotor for both angiogenesis and fibrosis in eyes with AMD.-Wu, D., Kanda, A., Liu, Y., Kase, S., Noda, K., Ishida, S. Galectin-1 promotes choroidal neovascularization and subretinal fibrosis mediated via epithelial-mesenchymal transition.

Human Vascular Endothelial Growth Factor A165 Expression Induces the Mouse Model of Neovascular Age-Related Macular Degeneration

Vascular endothelial growth factor (VEGF) expression induces age-related macular degeneration (AMD), which is a common vision-threatening disease due to choroidal neovascularization and a fibrovascular membrane. We describe a mouse model of neovascular AMD with the local expression of human VEGF-A₁₆₅ in the eye. We use a transgenic mouse in which human VEGF-A₁₆₅ has been silenced with the loxP-STOP fragment. The choroidal neovascularization and human VEGF-A₁₆₅ expression in the mouse are induced by subretinal adenoviral Cre gene delivery. Cre gene transfer is compared with adenoviral LacZ gene transfer control. We characterize the AMD phenotype and changes in the vasculature by using fluorescein angiography, optical coherence tomography, and immunohistochemistry. At early time points, mice exhibit increases in retinal thickness (348 ± 114 µm vs. 231 ± 32 µm) and choroidal neovascularization area (12000 ± 15174 µm² vs. 2169 ± 3495 µm²) compared with the control. At later time points, choroidal neovascularization develops into subretinal fibrovascular membrane. Human VEGF-A₁₆₅ expression lasts several weeks. In conclusion, the retinas display vascular abnormalities consistent with choroidal neovascularization. Together with immunohistochemical findings, these changes resemble clinical AMD-like ocular pathologies. We conclude that this mouse model of Cre-induced choroidal neovascularization is useful for mimicking the pathogenesis of AMD, studying the effects of human VEGF-A₁₆₅ in the retina, and evaluating anti-VEGF treatments for choroidal neovascularization.

Dabigatran inhibits intravitreal thrombin activity

PURPOSE

Proliferative vitreoretinopathy (PVR) is a vitreoretinal disorder in which retinal pigment epithelial (RPE) cell activation contributes to both formation of fibrotic retinal membranes and inflammation. Vitreous of patients with PVR contains increased thrombin activity which induces profibrotic and proinflammatory programs in RPE cells. Inhibition of intravitreal thrombin activity may thus represent a therapeutic option for PVR. In this study, we examined the capacity of the clinically available direct thrombin inhibitor dabigatran to inhibit thrombin activity in vitreous fluids.

METHODS

ARPE-19 cells were cultured with the following: (i) thrombin, (ii) vitreous without thrombin activity and (iii) vitreous with elevated thrombin activity (PVR samples and thrombin spiked vitreous) either in the presence or absence of dabigatran (range: 10^-5 to 10^-7  M). Subsequently, CCL2, CXCL8, GMCSF, IL6 and PDGFB mRNA expression levels were determined by RQ-PCR and protein levels of 27 cytokines, chemokines and growth factors were detected in culture supernatants using a multiplex approach. In addition, the capacity of vitreous fluids obtained from patients after oral dabigatran intake was tested in an in vitro thrombin activity assay.

RESULTS

Thrombin and vitreous fluids containing thrombin activity induced CCL2, CXCL8, GM-CSF, IL-6 and PDGF-BB expression by ARPE-19 cells, which was inhibited by dabigatran. In addition, dabigatran that reached the vitreous after repeated oral intake did inhibit thrombin activity in the in vitro activity assay.

CONCLUSION

Proliferative vitreoretinopathy (PVR) is associated with increased intravitreal thrombin activity that activates profibrotic and proinflammatory pathways in RPE cells. Our findings provide evidence that this activation pathway can potentially be inhibited by dabigatran.

Choroidal pericytes promote subretinal fibrosis after experimental photocoagulation

Subretinal fibrosis results in local destruction of retinal structures and permanent vision loss, representing the end stage of neovascular age-related macular degeneration (AMD). Histological examination of fibrotic specimens from AMD patients has uncovered a wide range of cellular and acellular components. However, their origins and roles in fibrosis remain largely unexplored. Using a laser-induced photocoagulation model with collagen 1α1-GFP reporter mice, we demonstrate, by cell-lineage tracing, that pericytes associating with choroidal microvasculature are activated upon injury and infiltrate into the subretinal space as significant components of fibrotic lesions. In contrast to their choroidal precursors, infiltrating pericytes acquire stellate-like structures, upregulate expression of fibrogenic molecules and colocalize with extracellular fibrotic scar. Collectively, our results identify the choroidal perivascular niche as a novel source of subretinal fibrosis after photocoagulation, and suggest that collagen 1-expressing pericytes are potential targets for therapeutic intervention to suppress subretinal fibrosis and preserve vision.

Interleukin-6 plays a crucial role in the development of subretinal fibrosis in a mouse model

Subretinal fibrosis has been recognized as a feature of an advanced stage of exudative age-related macular degeneration (AMD) that leads to irreversible loss of vision. This study was aimed at elucidating roles of interlukin-6 (IL-6) in the development of subretinal fibrosis. Immunohistochemistry (IHC) was performed with anti-human IL-6 antibody in surgically excised choroidal neovascular tissues from patients with exudative AMD. The area of subretinal fibrosis was measured in a mouse subretinal fibrosis model with injection of control small interfering RNA(siRNA) or IL-6 siRNA, or isotype control antibody or anti-IL-6 receptor antibody after peritoneal exudative cells (PECs) injection into the vitreous cavity. PECs derived from IL-6^+/+ or IL-6^-∕- mice were placed into the subretinal space of IL-6^+/+ mice. IL-6 was expressed in the stroma and retinal pigment epithelial (RPE) layer in the choroidal neovascular tissues. IL-6 knockdown or blocking of the IL-6 receptor suppressed the formation of subretinal fibroblastic scars. The area of subretinal fibrosis induced by PECs derived from IL-6^-∕- mice was less than that induced by PECs from IL-6^+/+ mice. The results suggested that IL-6, expressed by activated macrophages, is a crucial mediator that promotes subretinal fibrosis. Targeting IL-6 and the corresponding signaling pathway would be an attractive therapeutic approach not only in choroidal neovascularization, but also in subretinal fibrosis.

Involvement of the ubiquitin-proteasome system in the expression of extracellular matrix genes in retinal pigment epithelial cells

Emerging evidence suggests that dysfunction of the ubiquitin-proteasome system is involved in the pathogenesis of numerous senile degenerative diseases including retinal disorders. The aim of this study was to assess whether there is a link between proteasome regulation and retinal pigment epithelium (RPE)-mediated expression of extracellular matrix genes. For this purpose, human retinal pigment epithelial cells (ARPE-19) were treated with different concentrations of transforming growth factor-β (TGFβ), connective tissue growth factor (CTGF), interferon-γ (IFNγ) and the irreversible proteasome inhibitor epoxomicin. First, cytotoxicity and proliferation assays were carried out. The expression of proteasome-related genes and proteins was assessed and proteasome activity was determined. Then, expression of fibrosis-associated factors fibronectin (FN), fibronectin EDA domain (FN EDA), metalloproteinase-2 (MMP-2), tissue inhibitor of metalloproteinases-1 (TIMP-1) and peroxisome proliferator-associated receptor-γ (PPARγ) was assessed. The proteasome inhibitor epoxomicin strongly arrested cell cycle progression and down-regulated TGFβ gene expression, which in turn was shown to induce expression of pro-fibrogenic genes in ARPE-19 cells. Furthermore, epoxomicin induced a directional shift in the balance between MMP-2 and TIMP-1 and was associated with down-regulation of transcription of extracellular matrix genes FN and FN-EDA and up-regulation of the anti-fibrogenic factor PPARγ. In addition, both CTGF and TGFβ were shown to affect expression of proteasome-associated mRNA and protein levels. Our results suggest a link between proteasome activity and pro-fibrogenic mechanisms in the RPE, which could imply a role for proteasome-modulating agents in the treatment of retinal disorders characterized by RPE-mediated fibrogenic responses.

Baseline Predictors of Visual Acuity Outcome in Patients with Wet Age-Related Macular Degeneration

Age-related macular degeneration (AMD) is one of the leading causes of severe vision loss in people over 60 years. Wet AMD (wAMD) causes more severe visual acuity (VA) loss compared with the dry form due to formation of choroidal neovascularization (CNV). Antivascular endothelial growth factor (anti-VEGF) agents such as ranibizumab and aflibercept are now the standard of care treatment for wAMD. Unfortunately, up to a quarter of anti-VEGF-treated wAMD patients might not fully benefit from intravitreal injections and CNV activity may not respond to the treatment and these patients are called anti-VEGF nonresponders. This article aims to discuss the baseline factors associated with VA outcome such as age, initial VA, lesion types, disease duration, optical coherence tomography (OCT) features, fundus autofluorescence findings, and the presence of particular genotype risk alleles in patients with wAMD. Recommendations are provided regarding when to consider discontinuation of therapy because of either success or futility. Understanding the predictive factors associated with VA outcome and treatment frequency response to anti-VEGF therapy may help retina specialists to manage patients' expectations and guide treatment decisions from the beginning of treatment on the basis of “personalized medicine.”

Recent Updates on Treatment of Ocular Microbial Infections by Stem Cell Therapy: A Review

Ocular microbial infection has emerged as a major public health crisis during the past two decades. A variety of causative agents can cause ocular microbial infections; which are characterized by persistent and destructive inflammation of the ocular tissue; progressive visual disturbance; and may result in loss of visual function in patients if early and effective treatments are not received. The conventional therapeutic approaches to treat vision impairment and blindness resulting from microbial infections involve antimicrobial therapy to eliminate the offending pathogens or in severe cases; by surgical methods and retinal prosthesis replacing of the infected area. In cases where there is concurrent inflammation, once infection is controlled, anti-inflammatory agents are indicated to reduce ocular damage from inflammation which ensues. Despite advances in medical research; progress in the control of ocular microbial infections remains slow. The varying level of ocular tissue recovery in individuals and the incomplete visual functional restoration indicate the chief limitations of current strategies. The development of a more extensive therapy is needed to help in healing to regain vision in patients. Stem cells are multipotent stromal cells that can give rise to a vast variety of cell types following proper differentiation protocol. Stem cell therapy shows promise in reducing inflammation and repairing tissue damage on the eye caused by microbial infections by its ability to modulate immune response and promote tissue regeneration. This article reviews a selected list of common infectious agents affecting the eye; which include fungi; viruses; parasites and bacteria with the aim of discussing the current antimicrobial treatments and the associated therapeutic challenges. We also provide recent updates of the advances in stem cells studies on sepsis therapy as a suggestion of optimum treatment regime for ocular microbial infections.

Inflammation-Induced Photoreceptor Cell Death

Neuroinflammation is an important aspect of many diseases of the eye, and experimental animal models have been widely used to determine its impact on retinal homeostasis and neuron survival. Physical separation of the neurosensory retina from the underlying retinal pigment epithelium (RPE) results in activation and infiltration of macrophages. Numerous studies have shown the critical role of macrophages in retinal disease processes. In retinal detachment, accumulation of macrophages in the subretinal space is associated with changes in cytokine and chemokine profile which lead to photoreceptor cell death. Targeted disruption of macrophage chemotaxis significantly reduces retinal detachment-induced photoreceptor degeneration. Apoptosis is the predominant mechanism of cell death; however regulated necrosis is also a contributor of photoreceptor loss. Therefore, effective neuroprotective approaches could integrate combined inhibition of both apoptotic and regulated necrosis pathways.

NLRP3 inflammasome activation is associated with proliferative diabetic retinopathy

PURPOSE

Innate immunity and dysregulation of inflammatory processes play a role in vascular diseases like atherosclerosis or diabetes. Nucleotide-binding domain and Leucine-rich repeat Receptor containing a Pyrin domain 3 (NLRP3) inflammasomes are pro-inflammatory signalling complexes that were found in 2002. In addition to pathogens and other extracellular threats, they can be activated by various endogenous danger signals. The purpose of this study was to find out whether NLRP3 activation occurs in patients with sight-threatening forms of diabetic retinopathy (DR).

METHODS

Inflammasome components NLRP3 and caspase-1, inflammasome-related pro-inflammatory cytokines IL-1β and IL-18, vascular endothelial growth factor (VEGF), acute-phase cytokines TNF-α and IL-6, as well as adaptive immunity-related cytokine interferon gamma (IFN-γ) were measured from the vitreous samples of 15 non-proliferative diabetic retinopathy (non-PDR) and 23 proliferative diabetic retinopathy (PDR) patients using the enzyme-linked immunosorbent assay (ELISA) method. The adaptor protein apoptosis-associated speck-like protein containing a CARD (ASC) was determined using the Western blot technique.

RESULTS

Inflammasome components were present in the vitreous of DR patients. Along with VEGF, the levels of caspase-1 and IL-18 were significantly increased, especially in PDR eyes. Interestingly, clearly higher levels of NLRP3 were found in the PDR eyes with tractional retinal detachment (TRD) than from PDR eyes with fully attached retina. There were no significant differences in the amounts of IL-1β, TNF-α, IL-6, and IFN-γ that were detectable in the vitreous of both non-PDR and PDR patients.

CONCLUSION

Our results suggest that NLRP3 inflammasome activation can be associated especially with the pathogenesis of PDR. The lack of differences in TNF-α, IL-6, and IFN-γ also alludes that acute inflammation or T-cell-mediated responses do not dominate in PDR pathogenesis.

Principles of pharmacology in the eye

The eye is a highly specialized organ that is subject to a huge range of pathology. Both local and systemic disease may affect different anatomical regions of the eye. The least invasive routes for ocular drug administration are topical (e.g. eye drops) and systemic (e.g. tablets) formulations. Barriers that subserve as protection against pathogen entry also restrict drug permeation. Topically administered drugs often display limited bioavailability due to many physical and biochemical barriers including the pre-corneal tear film, the structure and biophysiological properties of the cornea, the limited volume that can be accommodated by the cul-de-sac, the lacrimal drainage system and reflex tearing. The tissue layers of the cornea and conjunctiva are further key factors that act to restrict drug delivery. Using carriers that enhance viscosity or bind to the ocular surface increases bioavailability. Matching the pH and polarity of drug molecules to the tissue layers allows greater penetration. Drug delivery to the posterior segment is a greater challenge and, currently, the standard route is via intravitreal injection, notwithstanding the risks of endophthalmitis and retinal detachment with frequent injections. Intraocular implants that allow sustained drug release are at different stages of development. Novel exciting therapeutic approaches include methods for promoting transscleral delivery, sustained release devices, nanotechnology and gene therapy.

Modulation of Fibroblasts in Conjunctival Wound Healing

Modulating conjunctival wound healing has the potential to improve outcomes after glaucoma filtration surgery and for several ocular disorders, including ocular cicatrial pemphigoid, vernal keratoconjunctivitis, and pterygium. Although anti-inflammatories and antimetabolites have been used with success, these nonspecific agents are not without their complications. The search for novel and more targeted means to control conjunctival fibrosis without such limitations has brought much attention to the regulation of fibroblast proliferation, differentiation, extracellular matrix production, and apoptosis. This review provides an update on where we stand with current antifibrotic agents and outlines the strategies that novel agents use, as they evolve from the bench to the bedside.

Hyperglycemia Alters the Protein Levels of Prominin-1 and VEGFA in the Retina of Albino Rats

In this study, we addressed the potential relationship between prominin-1 (prom1) and vascular endothelial growth factor (VEGFA) in diabetes-induced retinopathy. In total, we examined 28 retinas from 14 rats with streptozotocin-induced diabetes and 30 retinas from 15 untreated control rats. ELISA was used to measure the level of prom1 and VEGFA in retinal tissue homogenates. Immunohistochemical techniques were used with antibodies directed against prom1, VEGFA, and CASP-3. After 180 days of diabetes induction, we performed light and electron microscopy studies on rat eyes to evaluate histopathological changes and to estimate the de novo metric "Diabetic Retinopathy Histopathological Index" (DRHI). These changes were then correlated to the tissue and immunoexpression levels of prom1 and VEGFA. The data showed a significant upregulation of the tissue levels and optical densities (ODs) of VEGFA and prom1 immunoreactivity in diabetic retinas compared with controls. Both the tissue levels and OD values of prom1 and VEGFA correlated significantly with each other and to the diabetic structural changes as calculated by DRHI. Taken together, these data provide new insight into the potential role of prom1 and VEGFA in the development of diabetic retinopathy.

Neutralization of placental growth factor as a novel treatment option in diabetic retinopathy

The current standard of care in clinical practice for diabetic retinopathy (DR), anti-vascular endothelial growth factor (VEGF) therapy, has shown a significant improvement in visual acuity. However, treatment response can be variable and might be associated with potential side effects. This study was designed to investigate inhibition of placental growth factor (PlGF) as a possible alternative therapy for DR. The effect of the anti-PlGF antibody (PL5D11D4) was preclinically evaluated in various animal models by investigating different DR hallmarks, including inflammation, neurodegeneration, vascular leakage and fibrosis. The in vivo efficacy was tested in diabetic streptozotocin (STZ) and Akimba models and in the laser induced choroidal neovascularization (CNV) mouse model. Intravitreal (IVT) administration of the anti-PlGF antibody was compared to anti-VEGFR-2 antibody (DC101), anti-VEGF antibody (B20), VEGF-Trap (aflibercept) and triamcinolone acetonide (TAAC). Vascular leakage was investigated in the mouse STZ model by fluorescein isothiocyanate labeled bovine serum albumin (FITC-BSA) perfusion and in the Akimba model by fluorescein angiography (FA). Repeated IVT administration of the anti-PlGF antibody reduced vascular leakage, which was comparable to a single administration of VEGFR-2 inhibition in the mouse STZ model. PL5D11D4 treatment did not alter retinal ganglion cell (RGC) density, as demonstrated by Brn3a staining, whereas DC101 significantly reduced RGC number with 20%. Immunohistological stainings were performed to investigate inflammation (CD45, F4/80) and fibrosis (collagen type 1a). In the CNV model, IVT injection(s) of PL5D11D4 dose-dependently reduced inflammation and fibrosis, as compared to PBS treatment. Equimolar single administration of the anti-PlGF antibody and aflibercept (21 nM) and TAAC decreased leukocyte and macrophage infiltration with 50%, whereas DC101 and B20 (21 nM) had no effect on the inflammatory response. Similar results were observed in the mouse STZ model on the number of microglia and macrophages in the retina. Repeated administration of PL5D11D4 (21 nM) and TAAC similarly reduced fibrosis, while no effect was observed after equimolar DC101, B20 nor aflibercept administration (21 nM). In summary, the anti-PlGF antibody showed comparable efficacy as well-characterized VEGF-inhibitor on the process of vascular leakage, but differentiates itself by also reducing inflammation and fibrosis, without triggering a neurodegenerative response.

Myofibroblast transdifferentiation: The dark force in ocular wound healing and fibrosis

Wound healing is one of the most complex biological processes to occur in life. Repair of tissue following injury involves dynamic interactions between multiple cell types, growth factors, inflammatory mediators and components of the extracellular matrix (ECM). Aberrant and uncontrolled wound healing leads to a non-functional mass of fibrotic tissue. In the eye, fibrotic disease disrupts the normally transparent ocular tissues resulting in irreversible loss of vision. A common feature in fibrotic eye disease is the transdifferentiation of cells into myofibroblasts that can occur through a process known as epithelial-mesenchymal transition (EMT). Myofibroblasts rapidly produce excessive amounts of ECM and exert tractional forces across the ECM, resulting in the distortion of tissue architecture. Transforming growth factor-beta (TGFβ) plays a major role in myofibroblast transdifferentiation and has been implicated in numerous fibrotic eye diseases including corneal opacification, pterygium, anterior subcapsular cataract, posterior capsular opacification, proliferative vitreoretinopathy, fibrovascular membrane formation associated with proliferative diabetic retinopathy, submacular fibrosis, glaucoma and orbital fibrosis. This review serves to introduce the pathological functions of the myofibroblast in fibrotic eye disease. We also highlight recent developments in elucidating the multiple signaling pathways involved in fibrogenesis that may be exploited in the development of novel anti-fibrotic therapies to reduce ocular morbidity due to scarring.

Galectin-3 Inhibition by a Small-Molecule Inhibitor Reduces Both Pathological Corneal Neovascularization and Fibrosis

Purpose

Corneal neovascularization and scarring commonly lead to significant vision loss. This study was designed to determine whether a small-molecule inhibitor of galectin-3 can inhibit both corneal angiogenesis and fibrosis in experimental mouse models.

Methods

Animal models of silver nitrate cautery and alkaline burn were used to induce mouse corneal angiogenesis and fibrosis, respectively. Corneas were treated with the galectin-3 inhibitor, 33DFTG, or vehicle alone and were processed for whole-mount immunofluorescence staining and Western blot analysis to quantify the density of blood vessels and markers of fibrosis. In addition, human umbilical vein endothelial cells (HUVECs) and primary human corneal fibroblasts were used to analyze the role of galectin-3 in the process of angiogenesis and fibrosis in vitro.

Results

Robust angiogenesis was observed in silver nitrate-cauterized corneas on day 5 post injury, and markedly increased corneal opacification was demonstrated in alkaline burn-injured corneas on days 7 and 14 post injury. Treatment with the inhibitor substantially reduced corneal angiogenesis and opacification with a concomitant decrease in α-smooth muscle actin (α-SMA) expression and distribution. In vitro studies revealed that 33DFTG inhibited VEGF-A-induced HUVEC migration and sprouting without cytotoxic effects. The addition of exogenous galectin-3 to corneal fibroblasts in culture induced the expression of fibrosis-related proteins, including α-SMA and connective tissue growth factor.

Conclusions

Our data provide proof of concept that targeting galectin-3 by the novel, small-molecule inhibitor, 33DFTG, ameliorates pathological corneal angiogenesis as well as fibrosis. These findings suggest a potential new therapeutic strategy for treating ocular disorders related to pathological angiogenesis and fibrosis.

A novel porcine ex vivo retina culture model for oxidative stress induced by H₂O₂

Oxidative stress is a key player in many ophthalmic diseases. However, the role of oxidative stress in most degenerative processes is not yet known. Therefore, accurate and practical models are required to efficiently screen for therapeutics. Porcine eyes are closely related to the human eye, and can be obtained from the abattoir as a by-product of the food industry. Therefore, they offer excellent opportunities for the development of culture models with which to pre-screen potential therapies, while reducing the use of laboratory animals. To induce oxidative stress, organotypic cultures of porcine retina were treated with different doses of hydrogen peroxide (H₂O₂; 100, 300 and 500μM) for three hours. On days 3 and 8, the retinas were conserved for histological and Western blotting analyses and for evaluation of gene expression, which determined the number of retinal ganglion cells (RGCs), the activation state of glial cells, and the expression levels of several oxidative stress markers. H₂O₂ treatment led to a reduction in the number of RGCs and to an increase in apoptotic RGCs. In addition, a dose-dependent increase of microglia and an elevation of CD11b expression was observed. On day 3, a reduction of IL-1β, and an increase of iNOS, as well as of HSP70 mRNA were found. On day 8, an increase in TNF-α and IL-1β mRNA expression was detected. In conclusion, this ex vivo model offers an opportunity to study the molecular mechanisms underlying certain eye disorders and to test new therapeutic approaches to diminish the effects of oxidative stress.

Mouse Models of Corneal Scarring

Corneal scarring is an obligatory consequence of stroma corneal injury and is a major cause of decreased visual quality and vision loss worldwide. There are currently no satisfactory intervention therapies for corneal fibrosis. In this chapter, we describe well-established in vivo corneal wound models to allow researchers to investigate epithelial and stromal responses to corneal injury.

Interleukin-33 regulates tissue remodelling and inhibits angiogenesis in the eye

Age‐related macular degeneration (AMD) is the leading cause of central vision loss worldwide. Loss of retinal pigment epithelium (RPE) is a major pathological hallmark in AMD with or without pathological neovascularization. Although activation of the immune system is implicated in disease progression, pathological pathways remain diverse and unclear. Here, we report an unexpected protective role of a pro‐inflammatory cytokine, interleukin‐33 (IL‐33), in ocular angiogenesis. IL‐33 and its receptor (ST2) are expressed constitutively in human and murine retina and choroid. When RPE was activated, IL‐33 expression was markedly elevated in vitro. We found that IL‐33 regulated tissue remodelling by attenuating wound‐healing responses, including reduction in the migration of choroidal fibroblasts and retinal microvascular endothelial cells, and inhibition of collagen gel contraction. In vivo, local administration of recombinant IL‐33 inhibited murine choroidal neovascularization (CNV) formation, a surrogate of human neovascular AMD, and this effect was ST2‐dependent. Collectively, these data demonstrate IL‐33 as a potential immunotherapy and distinguishes pathways for subverting AMD pathology. © 2016 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

Inhibition of glial proliferation, promotion of axonal growth and myelin production by synthetic glycolipid: A new approach for spinal cord injury treatment

PURPOSE

After spinal cord injury (SCI) a glial scar is generated in the area affected that forms a barrier for axon growth and myelination, preventing functional recovery. Recently, we have described a synthetic glycolipid (IG20) that inhibited proliferation of human glioma cells. We show now that IG20 inhibited the proliferation of astrocytes and microglial cells, the principal cellular components of the glial scar, and promoting axonal outgrowth and myelin production in vitro.

METHODS

Glial cells were inhibited with IG20 (IC50≈10 μM) and studied by RT-PCR, Western Blotting, immunoprecipitation and fluorescence microscopy. Axonal outgrowth in dorsal root ganglia (DRG) and myelin production by oligodendrocytes were analyzed by immunocytochemistry. Adult rats were assayed in spinal cord contusion model and the recovery of treated animals (n = 6) and controls (n = 6) was followed.

RESULTS

The IG20 was localized in the cytosol of glial cells, forming a complex with RhoGDIα, a regulator of RhoGTPases. Treatment of astroglial cultures with IG20 increase the expression of BDNF receptor genes (TrkBT1, TrkB Full). IG20 reduced the astroglial marker GFAP, while increasing production of myelin basic protein in oligodendrocytes and promoted axonal outgrowth from DRG neurons. Local injection of IG20, near a spinal cord contusion, promoted the recovery of lesioned animals analyzed by BBB test (P <  0.05).

CONCLUSIONS

We propose that inhibition of astrocytes and microglia by IG20 could be diminished the glial scar formation, inducing the re-growth and myelination of axons, these elements constitute a new approach for SCI therapy.

Trichostatin A Inhibits Retinal Pigmented Epithelium Activation in an In Vitro Model of Proliferative Vitreoretinopathy

Purpose: Proliferative vitreoretinopathy (PVR) is a blinding disorder that develops after a retinal tear or detachment. Activation of the retinal pigmented epithelium (RPE) is implicated in PVR; however, the mechanisms leading to enhanced RPE proliferation, migration, and contraction remain largely unknown. This study utilized an in vitro model of PVR to investigate the role of acetylation in RPE activation and its contribution to the progression of this disease.

Methods: ARPE-19 cells, primary cultures of porcine RPE, and induced pluripotent stem cell-derived RPE (iPS-RPE) were utilized for cellular and molecular analyses. Cells treated with transforming growth factor beta 2 (TGFβ2; 10 ng/mL) alone or in the presence of the broad-spectrum histone deacetylase (HDAC) inhibitor, trichostatin A (TSA; 0.1 μM), were assessed for contraction and migration through collagen contraction and scratch assays, respectively. Western blotting and immunofluorescence analysis were performed to assess α-smooth muscle actin (α-SMA) and β-catenin expression after TGFβ2 treatment alone or in combination with TSA.

Results: TGFβ2 significantly increased RPE cell contraction in collagen matrix and this effect was inhibited in the presence of TSA (0.1 μM). In agreement with these data, immunofluorescence analysis of TSA-treated iPS-RPE wounded monolayers revealed decreased α-SMA as compared with control. Scratch assays to assess wound healing revealed TSA inhibited TGFβ2-mediated iPS-RPE cell migration.

Conclusions: Our findings indicate a role of acetylation in RPE activation. Specifically, the HDAC inhibitor TSA decreased RPE cell proliferation and TGFβ2-mediated cell contraction and migration. Further investigation of pharmacological compounds that modulate acetylation may hold promise as therapeutic agents for PVR.

Inhibition of development of laser-induced choroidal neovascularization with suppression of infiltration of macrophages in Smad3-null mice

We evaluated the effects of the loss of Smad3 on the development of experimental argon laser-induced choroidal neovascularization (CNV) in mice. An in vitro angiogenesis model was also used to examine the role of transforming growth factor-β1 (TGFβ1)/Smad3 signaling in vessel-like tube formation by human umbilical vein endothelial cells (HUVECs). CNV was induced in eyes of 8-12-week-old B6.129-background Smad3-deficient (KO) mice (n=47) and wild-type (WT) mice (n=47) by argon laser irradiation. Results showed that the size of the CNV induced was significantly smaller in KO mice as compared with WT mice at day 14 as revealed by high-resolution angiography with fluorescein isothiocyanate-dextran. Immunohistochemistry and real-time reverse transcription-polymerase chain reaction of RNA extracted from laser-irradiated choroidal tissues were conducted on specimens at specific timepoints. Invasion of macrophages (F4/80+), but not neutrophils (myeloperoxidase+), and appearance of myofibroblasts (α-smooth muscle actin+) were suppressed in laser-irradiated KO tissues. mRNA expression of inflammation-related factors, that is, vascular endothelial growth factor (VEGF), macrophage-chemoattractant protein-1 (MCP-1), interleukin-6 (IL-6) and TGFβ1 in choroidal tissues was suppressed by the loss of Smad3. We then examined the effects of adding a Smad3 inhibitor, SIS3, or an ALK5 inhibitor, SB431542, on tube formation promoted by TGFβ1 or VEGF in HUVECs cocultured with fibroblast feeder. Further addition of SIS3 or SB431542 augmented vessel-like tube formation by HUVECs in the presence of TGFβ1 or VEGF. In conclusion, lack of Smad3 attenuated the growth of laser-induced CNV with suppression of inflammation by macrophages in mice. Because blocking TGFβ1/Smad3 signal stimulated the activity of angiogenesis of HUVECs in vitro, the reduction of CNV in vivo in KO mice is attributed to a decrease in growth factor levels in the tissue by the loss of Smad3.

Stem Cell Therapy for Treatment of Ocular Disorders

Sustenance of visual function is the ultimate focus of ophthalmologists. Failure of complete recovery of visual function and complications that follow conventional treatments have shifted search to a new form of therapy using stem cells. Stem cell progenitors play a major role in replenishing degenerated cells despite being present in low quantity and quiescence in our body. Unlike other tissues and cells, regeneration of new optic cells responsible for visual function is rarely observed. Understanding the transcription factors and genes responsible for optic cells development will assist scientists in formulating a strategy to activate and direct stem cells renewal and differentiation. We review the processes of human eye development and address the strategies that have been exploited in an effort to regain visual function in the preclinical and clinical state. The update of clinical findings of patients receiving stem cell treatment is also presented.

Retinal fibrosis in diabetic retinopathy

In response to injury, reparative processes are triggered to restore the damaged tissue; however, such processes are not always successful in rebuilding the original state. The formation of fibrous connective tissue is known as fibrosis, a hallmark of the reparative process. For fibrosis to be successful, delicately balanced cellular events involving cell proliferation, cell migration, and extracellular matrix (ECM) remodeling must occur in a highly orchestrated manner. While successful repair may result in a fibrous scar, this often restores structural stability and functionality to the injured tissue. However, depending on the functionality of the injured tissue, a fibrotic scar can have a devastating effect. For example, in the retina, fibrotic scarring may compromise vision and ultimately lead to blindness. In this review, we discuss some of the retinal fibrotic complications and highlight mechanisms underlying the development of retinal fibrosis in diabetic retinopathy.

The Mechanism of Ligamentum Flavum Hypertrophy: Introducing Angiogenesis as a Critical Link That Couples Mechanical Stress and Hypertrophy

BACKGROUND

Biochemical alterations associated with mechanical stress have been explored as an initiating step in the pathological progression of ligamentum flavum hypertrophy (LFH); however, this mechanism remains poorly understood. Recently, the inflammation induced after mechanical stress and the subsequent response of ligamentum flavum (LF) cells have been implicated in LFH pathology.

OBJECTIVE

To investigate the hypothesis that angiogenesis may be a critical link between hypertrophy and a series of stimulating events, including mechanical stress.

METHODS

LF from 20 lumbar spinal canal stenosis (LSCS) patients and 16 non-LSCS patients (control group) were collected during surgery. Patient demographic and radiographic data were obtained. The levels of angiogenic factors (vascular endothelial growth factor [VEGF], angiopoietin-1, vascular cell adhesion molecule, and basic fibroblast growth factor) in the LF were investigated by using an enzyme-linked immunosorbent assay. Angiogenesis was also quantified by immunohistochemical detection of CD34-positive capillaries. The correlations among clinical factors, including radiographic factors, angiogenic factors, and angiogenesis, were statistically analyzed.

RESULTS

The LSCS group was older and exhibited a longer symptom duration, wider segmental motion, and thicker LF than the control group. The LSCS group showed significantly higher tissue concentrations of VEGF (P < .001) that positively correlated with LF thickness (r = 0.557, P < .001) and segmental motion (r = 0.586, P < .001). The LSCS group showed significantly more CD34-positive capillaries than the control group (P = .004).

CONCLUSION

The LSCS group showed greater segmental motion, higher VEGF concentrations, and more CD34-positive capillaries than the control group. These data indicate that VEGF-mediated angiogenesis following mechanical stress may be a critical step within the series of pathological events in LFH.

Effects of mechanical stress and vitreous samples in retinal pigment epithelial cells

In rhegmatogenous retinal detachment (RRD), scattered RPE cells from the basement membrane into the vitreous cavity undergo an epithelial mesenchymal transition (EMT) and form the intraocular fibrous membrane in response to vitreous fluid. We investigated whether exposure to vitreous samples was associated with EMT-associated signals and mesenchymal characters. Human vitreous samples were collected from patients with RRD, epiretinal membrane (ERM), or macular hole (MH). We evaluated the effects of vitreous on ARPE-19 cells in suspension cultures using poly 2-hydroxyethyl methacrylate-coated dishes and three-dimensional (3D) Matrigel cultures. We found that exposure to vitreous samples did not induce morphological changes or accelerate wound closure in monolayers. Several samples showed increased phosphorylation of Smad2 and nuclear translocation of nuclear factor-κB. Mechanical stress triggered an elevation of phosphorylation levels in Smad2. In addition, exposure to vitreous fluid increased the phosphorylation of p38 mitogen-activated protein kinase in cell suspension cultures after mechanical stress. Moreover, ARPE-19 cells showed a stellate invasive phenotype in 3D Matrigel cultures with vitreous samples. In this study, we demonstrated that mechanical stress and vitreous were associated with EMT-associated signals and invasive phenotypes in 3D cultures but not in monolayers. These results have important implications for the role of vitreous humor in the induction of EMT and intraocular fibrosis.

Molecular mechanisms of subretinal fibrosis in age-related macular degeneration

Subretinal fibrosis is a result of a wound healing response that follows choroidal neovascularization in neovascular age-related macular degeneration (nAMD). Although anti-vascular endothelial growth factor therapy has become a standard treatment that improves visual acuity in many nAMD patients, unsuccessful treatment outcomes have often been attributed to the progression of subretinal fibrosis. In this review, we summarize the cellular and extracellular components of subretinal fibrous membranes and also discuss the possible molecular mechanisms including the functional involvement of growth factors and the inflammatory response in the process. Moreover, we present an murine animal model of subretinal fibrosis that might facilitate greater understanding of the pathophysiology and the development of novel therapeutic strategies for the inhibition of subretinal fibrosis in nAMD.

Indications of lymphatic endothelial differentiation and endothelial progenitor cell activation in the pathology of proliferative diabetic retinopathy

PURPOSE

Proliferative diabetic retinopathy (PDR) is characterized by ischaemia- and inflammation-induced neovascularization, but the pathological vascular differentiation in PDR remains poorly characterized. Here, endothelial progenitor and growth properties, as well as potential lymphatic differentiation, were investigated in the neovascular membrane specimens from vitrectomized patients with PDR.

METHODS

The expression of pan-endothelial CD31 (PECAM-1), ETS-related gene (ERG), α-smooth muscle actin (α-SMA), and stem/progenitor cell marker CD117 (c-kit) and cell proliferation marker Ki67 was investigated along with the markers of lymphatic endothelial differentiation (vascular endothelial growth factor receptor (VEGFR)-3; prospero-related homeobox gene-1 (Prox-1), lymphatic vessel endothelial receptor [LYVE)-1 and podoplanin (PDPN)] by immunohistochemistry. Lymphocyte antigen CD45 and pan-macrophage marker CD68 were likewise investigated.

RESULTS

All specimens displayed CD31, ERG and α-SMA immunoreactivity in irregular blood vessels. Unexpectedly, VEGFR3 and Prox-1 lymphatic marker positive vessels were also detected in several tissues. Prox-1 was co-expressed with CD117 in lumen-lining endothelial cells and adjacent cells, representing putative endothelial stem/progenitor cells and pro-angiogenic perivascular cells. Immunoreactivity of CD45 and CD68 was detectable in all investigated diabetic neovessel specimens. PDPN immunoreactivity was also detected in irregular lumen-forming structures, but these cells lacked CD31 and ERG that mark blood and lymphatic endothelium.

CONCLUSIONS

Although the inner part of human eye is physiologically devoid of lymphatic vessels, lymphatic differentiation associated with endothelial stem/progenitor cell activation may be involved in the pathogenesis of human PDR. Further studies are warranted to elucidate whether targeting lymphatic factors could be beneficial in the treatment of patients with the sight-threatening forms of DR.

Restoration of mesenchymal retinal pigmented epithelial cells by TGFβ pathway inhibitors: implications for age-related macular degeneration

BACKGROUND

Age-related macular degeneration (AMD) is a leading cause of blindness. Most vision loss occurs following the transition from a disease of deposit formation and inflammation to a disease of neovascular fibrosis and/or cell death. Here, we investigate how repeated wound stimulus leads to seminal changes in gene expression and the onset of a perpetual state of stimulus-independent wound response in retinal pigmented epithelial (RPE) cells, a cell-type central to the etiology of AMD.

METHODS

Transcriptome wide expression profiles of human fetal RPE cell cultures as a function of passage and time post-plating were determined using Agilent 44 K whole genome microarrays and RNA-Seq. Using a systems level analysis, differentially expressed genes and pathways of interest were identified and their role in the establishment of a persistent mesenchymal state was assessed using pharmacological-based experiments.

RESULTS

Using a human fetal RPE cell culture model that considers monolayer disruption and subconfluent culture as a proxy for wound stimulus, we show that prolonged wound stimulus leads to terminal acquisition of a mesenchymal phenotype post-confluence and altered expression of more than 40 % of the transcriptome. In contrast, at subconfluence fewer than 5 % of expressed transcripts have two-fold or greater expression differences after repeated passage. Protein-protein and pathway interaction analysis of the genes with passage-dependent expression levels in subconfluent cultures reveals a 158-node interactome comprised of two interconnected modules with functions pertaining to wound response and cell division. Among the wound response genes are the TGFβ pathway activators: TGFB1, TGFB2, INHBA, INHBB, GDF6, CTGF, and THBS1. Significantly, inhibition of TGFBR1/ACVR1B mediated signaling using receptor kinase inhibitors both forestalls and largely reverses the passage-dependent loss of epithelial potential; thus extending the effective lifespan by at least four passages. Moreover, a disproportionate number of RPE wound response genes have altered expression in neovascular and geographic AMD, including key members of the TGFβ pathway.

CONCLUSIONS

In RPE cells the switch to a persistent mesenchymal state following prolonged wound stimulus is driven by lasting activation of the TGFβ pathway. Targeted inhibition of TGFβ signaling may be an effective approach towards retarding AMD progression and producing RPE cells in quantity for research and cell-based therapies.

Altered expression of fibrosis genes in capsules of failed Ahmed glaucoma valve implants

PURPOSE

Ahmed glaucoma valve (AGV) implant is an aqueous shunt device used to control intraocular pressure in glaucoma. Implant failure results from impervious encapsulation of the shunt plate causing increased hydraulic resistance and raised intraocular pressure. We hypothesized that deregulation of fibrosis pathway contributes to capsular resistance. We tested this by studying fibrosis related gene expression in failed AGV implants.

METHODS

Differential gene expression was examined in failed AGV capsules and compared to normal control tenon. Following total RNA extraction, 84 key genes in fibrosis pathway were examined by real-time PCR using RT2 Profiler PCR Array. Relative gene expression was calculated using ΔΔCt method. Gene specific TaqMan assays were used to validate select genes with ≥2 fold differential expression in the array expression profile.

RESULTS

We observed differential expression in several genes in the fibrosis pathway. Almost half (39/84) of examined genes showed ≥2 fold differential expression in majority of capsules examined on the array. TaqMan assays for select genes including CCN2 (CTGF), THBS1, SERPINE1, THBS2, COL3A1, MMP3, and IL1A in an increased validation sample set showed significant changes in expression (p value from <0.001 to 0.022) at a high frequency in concurrence with our array results.

CONCLUSIONS

Pathway-focused analyses identified candidate genes with altered expression providing molecular evidence for deregulation of the fibrosis pathway in AGV failure.

Simultaneous application of bevacizumab and anti-CTGF antibody effectively suppresses proangiogenic and profibrotic factors in human RPE cells

PURPOSE

Retinal pigment epithelial (RPE) cells play key roles in the development of choroidal neovascularization and subsequent fibrosis. We investigated the impact of bevacizumab, antihuman vascular endothelial growth factor (VEGF) antibody, and anticonnective tissue growth factor (anti-CTGF) neutralizing antibody, individually or in combination, on proangiogenic and profibrotic properties of RPE cells.

METHODS

Primary cultures of human RPE cells were incubated with different concentrations of bevacizumab (0.25, 0.5, and 0.8 mg/ml) and/or anti-CTGF (10 μg/ml), and cell proliferation and apoptosis were determined. Expression and activity of proangiogenic and profibrotic genes including matrix metalloproteinases (MMP)-2 and 9, VEGFA, CTGF, vascular endothelial growth factor receptor-1 (VEGFR-1), cathepsin D, tissue inhibitor of metalloproteinases (TIMP) -1 and -2, and alpha smooth muscle actin (α-SMA) were assessed with slot blot, real-time RT-PCR, and zymography.

RESULTS

Bevacizumab alone inhibited proliferation of RPE cells while anti-CTGF or bevacizumab and anti-CTGF combined had no inhibitory effect in this regard. Bevacizumab increased MMP-2, MMP-9, and cathepsin D but decreased VEGFA and VEGFR-1 expression. The CTGF level was increased by using 0.25 mg/ml bevacizumab but decreased at the 0.8 mg/ml concentration of bevacizumab. Treatment with anti-CTGF antibody decreased MMP-2 expression whereas combined treatment with bevacizumab and anti-CTGF resulted in decreased expression of MMP-2, TIMP-1, cathepsin D, VEGFA, CTGF, and α-SMA in the treated cultures.

CONCLUSIONS

Treatment of RPE cells with the combination of bevacizumab and anti-CTGF could effectively suppress the proangiogenic and profibrotic activity of RPE cells.