The novel use of decorin in prevention of the development of proliferative vitreoretinopathy (PVR)

Experimental Models to Study Epithelial-Mesenchymal Transition in Proliferative Vitreoretinopathy

Proliferative vitreoretinal diseases (PVDs) encompass proliferative vitreoretinopathy (PVR), epiretinal membranes, and proliferative diabetic retinopathy. These vision-threatening diseases are characterized by the development of proliferative membranes above, within and/or below the retina following epithelial-mesenchymal transition (EMT) of the retinal pigment epithelium (RPE) and/or endothelial-mesenchymal transition of endothelial cells. As surgical peeling of PVD membranes remains the sole therapeutic option for patients, development of in vitro and in vivo models has become essential to better understand PVD pathogenesis and identify potential therapeutic targets. The in vitro models range from immortalized cell lines to human pluripotent stem-cell-derived RPE and primary cells subjected to various treatments to induce EMT and mimic PVD. In vivo PVR animal models using rabbit, mouse, rat, and swine have mainly been obtained through surgical means to mimic ocular trauma and retinal detachment, and through intravitreal injection of cells or enzymes to induce EMT and investigate cell proliferation and invasion. This review offers a comprehensive overview of the usefulness, advantages, and limitations of the current models available to investigate EMT in PVD.

Applications of Human Amniotic Membrane Patching Assisted Vitrectomy in the Management of Postoperative PVR in Complex Retinal Detachments

Human amniotic membranes (hAMs) are extraembryonic tissues currently employed in the treatment of many ocular and systemic diseases. Several reports indicate that hAMs can suppress the signaling pathway of tissue growth factor beta (TGF-β), a cytokine that plays a major role in the pathogenesis of proliferative vitreoretinopathy (PVR) through the induction of epithelial-mesenchymal transition (EMT) in exposed retinal pigmented epithelium (RPE) cells. The present study was conducted to evaluate the efficacy of a modified vitrectomy procedure (hAMP-V) involving the extensive coverage of exposed RPE with hAM patches to prevent postoperative PVR in a series of 15 cases of retinal detachment complicated by severe preoperatory PVR. The primary outcome was to assess the rate of successful retinal reattachment of a single hAMP-V procedure at 6 months from silicone oil removal. Secondary outcomes included the collection of intraoperative data concerning the quantity, size, and scope of hAM patches, and the assessment of postoperative improvements in mean LogMar BCVA at 3 and 6 months. Successful retinal reattachment was obtained in 14 out of 15 eyes (93.3%). Surgical failure due to major recurrence of PVR occurred in 1 out of 15 eyes (6.7%). Postoperative improvements in mean LogMar BCVA were statistically significant (p < 0.05, paired t-test). No intraoperative and postoperative adverse effects were reported. The study helped to refine the surgical technique while also offering cues for future improvements.

Role of Decorin in the Lens and Ocular Diseases

Decorin is an archetypal member of the small leucine-rich proteoglycan gene family and is involved in various biological functions and many signaling networks, interacting with extra-cellular matrix (ECM) components, growth factors, and receptor tyrosine kinases. Decorin also modulates the growth factors, cell proliferation, migration, and angiogenesis. It has been reported to be involved in many ischemic and fibrotic eye diseases, such as congenital stromal dystrophy of the cornea, anterior subcapsular fibrosis of the lens, proliferative vitreoretinopathy, et al. Furthermore, recent evidence supports its role in secondary posterior capsule opacification (PCO) after cataract surgery. The expression of decorin mRNA in lens epithelial cells in vitro was found to decrease upon transforming growth factor (TGF)-β-2 addition and increase upon fibroblast growth factor (FGF)-2 addition. Wound healing of the injured lens in mice transgenic for lens-specific human decorin was promoted by inhibiting myofibroblastic changes. Decorin may be associated with epithelial-mesenchymal transition and PCO development in the lens. Gene therapy and decorin administration have the potential to serve as excellent therapeutic approaches for modifying impaired wound healing, PCO, and other eye diseases related to fibrosis and angiogenesis. In this review, we present findings regarding the roles of decorin in the lens and ocular diseases.

Damage-Associated Molecular Patterns (DAMPs) in Retinal Disorders

Damage-associated molecular patterns (DAMPs) are endogenous danger molecules released from the extracellular and intracellular space of damaged tissue or dead cells. Recent evidence indicates that DAMPs are associated with the sterile inflammation caused by aging, increased ocular pressure, high glucose, oxidative stress, ischemia, mechanical trauma, stress, or environmental conditions, in retinal diseases. DAMPs activate the innate immune system, suggesting their role to be protective, but may promote pathological inflammation and angiogenesis in response to the chronic insult or injury. DAMPs are recognized by specialized innate immune receptors, such as receptors for advanced glycation end products (RAGE), toll-like receptors (TLRs) and the NOD-like receptor family (NLRs), and purine receptor 7 (P2X7), in systemic diseases. However, studies describing the role of DAMPs in retinal disorders are meager. Here, we extensively reviewed the role of DAMPs in retinal disorders, including endophthalmitis, uveitis, glaucoma, ocular cancer, ischemic retinopathies, diabetic retinopathy, age-related macular degeneration, rhegmatogenous retinal detachment, proliferative vitreoretinopathy, and inherited retinal disorders. Finally, we discussed DAMPs as biomarkers, therapeutic targets, and therapeutic agents for retinal disorders.

Decorin Concentrations in Aqueous Humor of Patients with Diabetic Retinopathy

Diabetic retinopathy (DR) is a microvascular complication of diabetes in the retina. Chronic hyperglycemia damages retinal microvasculature embedded into the extracellular matrix (ECM), causing fluid leakage and ischemic retinal neovascularization. Current treatment strategies include intravitreal anti-vascular endothelial growth factor (VEGF) or steroidal injections, laser photocoagulation, or vitrectomy in severe cases. However, treatment may require multiple modalities or repeat treatments due to variable response. Though DR management has achieved great success, improved, long-lasting, and predictable treatments are needed, including new biomarkers and therapeutic approaches. Small-leucine rich proteoglycans, such as decorin, constitute an integral component of retinal endothelial ECM. Therefore, any damage to microvasculature can trigger its antifibrotic and antiangiogenic response against retinal vascular pathologies, including DR. We conducted a cross-sectional study to examine the association between aqueous humor (AH) decorin levels, if any, and severity of DR. A total of 82 subjects (26 control, 56 DR) were recruited. AH was collected and decorin concentrations were measured using an enzyme-linked immunosorbent assay (ELISA). Decorin was significantly increased in the AH of DR subjects compared to controls (p = 0.0034). AH decorin levels were increased in severe DR groups in ETDRS and Gloucestershire classifications. Decorin concentrations also displayed a significant association with visual acuity (LogMAR) measurements. In conclusion, aqueous humor decorin concentrations were found elevated in DR subjects, possibly due to a compensatory response to the retinal microvascular changes during hyperglycemia.

Small Leucine-Rich Proteoglycans (SLRPs) in the Retina

Retinal diseases such as age-related macular degeneration (AMD), retinopathy of prematurity (ROP), and diabetic retinopathy (DR) are the leading causes of visual impairment worldwide. There is a critical need to understand the structural and cellular components that play a vital role in the pathophysiology of retinal diseases. One potential component is the family of structural proteins called small leucine-rich proteoglycans (SLRPs). SLRPs are crucial in many fundamental biological processes involved in the maintenance of retinal homeostasis. They are present within the extracellular matrix (ECM) of connective and vascular tissues and contribute to tissue organization and modulation of cell growth. They play a vital role in cell–matrix interactions in many upstream signaling pathways involved in fibrillogenesis and angiogenesis. In this comprehensive review, we describe the expression patterns and function of SLRPs in the retina, including Biglycan and Decorin from class I; Fibromodulin, Lumican, and a Proline/arginine-rich end leucine-rich repeat protein (PRELP) from class II; Opticin and Osteoglycin/Mimecan from class III; and Chondroadherin (CHAD), Tsukushi and Nyctalopin from class IV.

Multiple Therapeutic Applications of RBM-007, an Anti-FGF2 Aptamer

Vascular endothelial growth factor (VEGF) plays a pivotal role in angiogenesis, but is not the only player with an angiogenic function. Fibroblast growth factor-2 (FGF2), which was discovered before VEGF, is also an angiogenic growth factor. It has been shown that FGF2 plays positive pathophysiological roles in tissue remodeling, bone health, and regeneration, such as the repair of neuronal damage, skin wound healing, joint protection, and the control of hypertension. Targeting FGF2 as a therapeutic tool in disease treatment through clinically useful inhibitors has not been developed until recently. An isolated inhibitory RNA aptamer against FGF2, named RBM-007, has followed an extensive preclinical study, with two clinical trials in phase 2 and phase 1, respectively, underway to assess the therapeutic impact in age-related macular degeneration (wet AMD) and achondroplasia (ACH), respectively. Moreover, showing broad therapeutic potential, preclinical evidence supports the use of RBM-007 in the treatment of lung cancer and cancer pain.

Pharmacotherapy as an adjunct to vitrectomy

Vitreoretinal surgery has advanced extensively from the first days of vitrectomy. During the last decade, new developments in intravitreal pharmacotherapy have created new opportunities to enhance the surgical outcomes of our patients. In this article, we review and discuss some of the supporting evidence of different pharmacotherapies that may be used as an adjunct to vitrectomy for select common etiologies. Triamcinolone acetonide, dexamethasone, and angiogenesis inhibitors are among the most commonly used drugs given their safety profile and proven efficacy. Other pharmaceuticals have also shown promising results in small studies. The adoption of individualized medical treatments prior, during, and after vitrectomy will continue to increase as new evidence supporting the benefit of pharmacotherapy as an adjunct to vitrectomy becomes available.

Role of Decorin in Posterior Capsule Opacification and Eye Lens Development

Decorin (DCN) is involved in a variety of physiological and pathological processes. Epithelial-mesenchymal transition (EMT) of lens epithelial cells (LECs) has been proposed as a major cause for the development of posterior capsule opacification (PCO) after cataract surgery. We investigated the plausible target gene(s) that suppress PCO. The expression of Dcn was significantly upregulated in rat PCO tissues compared to that observed in the control using a microarray-based approach. LECs treated with fibroblast growth factor (FGF) 2 displayed an enhanced level of DCN expression, while LECs treated with transforming growth factor (TGF)β-2 showed a decrease in DCN expression. The expression of tropomyosin 1 (Tpm1), a marker of lens EMT increased after the addition of TGFβ-2 in human LEC; however, upregulation of Tpm1 mRNA or protein expression was reduced in human LECs overexpressing human DCN (hDCN). No phenotypic changes were observed in the lenses of 8- and 48-week-old transgenic mice for lens-specific hDCN (hDCN-Tg). Injury-induced EMT of the mouse lens, and the expression patterns of α smooth muscle actin, were attenuated in hDCN-Tg mice lenses. Overexpression of DCN inhibited the TGFβ-2-induced upregulation of Tpm1 and EMT observed during wound healing of the lens, but it did not affect mouse lens morphology until 48 weeks of age. Our findings demonstrate that DCN plays a significant role in regulating EMT formation of LECs and PCO, and suggest that for therapeutic intervention, maintenance of physiological expression of DCN is essential to attenuate EMT progression and PCO formation.

Effect of Decorin and Bevacizumab on oxygen-induced retinopathy in rat models: A comparative study

Purpose

The aims of this study were to evaluate the effects of decorin (DCN) in rat oxygen-induced retinopathy (OIR) model and to compare the results with those of bevacizumab.

Methods

Twenty-eight newborn Sprague-Dawley rats were randomly divided into four groups. Group I (control): normoxia plus intraperitoneal (ip) normal saline (NS), Group II (sham): OIR plus ip NS, Group III (DCN): OIR plus ip 0.1 mg/kg DCN, and Group IV (bevacizumab): OIR plus ip 2.5 mg/kg bevacizumab. The OIR model was induced by cycling the oxygen concentration between 50% and 10% every 24 h for 14 days following their birth. In all groups, injections were administered on postnatal day (PD) 15. All animals were sacrificed and their right eyes were enucleated on PD 18. The nuclei of neovascular endothelial cells on the vitreal side of the inner limiting membrane were counted, and vascular endothelial growth factor (VEGF) and tumor necrosis factor-alpha (TNF)-α immunoreactivity were detected in histopathological and immunohistochemical examinations. One-way analysis of variance and post hoc Tukey tests were used for statistical analyses of the data.

Results

In Groups II, III, and IV, the mean neovascular cell nuclei counts were 13.14 ± 1.34, 6.57 ± 1.51, and 6.71 ± 1.49, respectively. The mean neovascular cell nuclei count was significantly reduced in treatment groups compared with sham group (P < 0.001). In immunohistochemical staining, the immunoreactivity of VEGF was 0.07 ± 0.02, 0.97 ± 0.21, 0.37 ± 0.12, and 0.23 ± 0.17, respectively. Likewise, immunoreactivity of TNF-α was 0.02 ± 0.02, 1.11 ± 0.36, 0.37 ± 0.13, and 0.62 ± 0.21, respectively. VEGF and TNF-α immunoreactivity increased markedly in the sham group compared with those in the control group (P < 0.001). VEGF and TNF-α immunoreactivity of treatment groups decreased significantly compared to sham group (P < 0.001).

Conclusion

The beneficial effects obtained by DCN administration in OIR model were comparable to the effects of bevacizumab.

[Proliferative vitreoretinopathy process-To heal or not to heal]

BACKGROUND

Proliferative vitreoretinopathy (PVR) is still an unsolved problem after half a century of research.

METHODS

This article provides a review of mechanisms leading to PVR in the context of wound healing research.

RESULTS

Wound healing is a physiological repair process that occurs in a similar way in all organs and may end in scar formation. The development of PVR is based on this wound healing mechanism. The localization and structures involved lead to specific characteristics and consequences. Up to now the pharmacotherapeutic strategies were not sufficiently effective. The growing understanding of the mechanisms of scar-free fetal wound healing, could however lead to a solution of the PVR problem.

CONCLUSION

The PVR is a physiological process with a pathological result. The complex steps involved in vitreoretinal wound healing are well understood. There is currently no therapeutic approach neither in ophthalmology nor in other medical disciplines that is able to restore the original function and structure of the involved tissue or organ but there is hope that this can succeed in the future.

Sustained dasatinib treatment prevents early fibrotic changes following ocular trauma

Purpose

Posterior ocular trauma and the subsequent fibrotic retinal complication termed proliferative vitreoretinopathy (PVR) are leading causes of blindness in children and young adults. A previous study suggested that changes occurring within the first month post-trauma can lead to development of PVR later. The aim of this study was to examine the effect of dasatinib, a tyrosine kinase inhibitor clinically used to treat chronic myeloid leukemia, on fibrotic changes occurring within the first month following ocular trauma.

Methods

A previously established swine ocular trauma model that mimics both contusion and penetrating injuries was used. Dasatinib was administered on days 4 and 18 post-trauma via intravitreal injection of either bolus solution or suspension of a sustained release system incorporated in biodegradable poly (lactic-co-glycolic acid) (PLGA) nanoparticles. Animals were followed up to day 32, and the development of traction full-thickness fold in the posterior retina was assessed.

Results

A full-thickness retinal fold extending from the wound site developed in 3 out of 4 control eyes injected with PLGA nanoparticles alone at 1 month. Administration of dasatinib solution had little preventative effect with 6 out of 7 eyes developing a fold. In contrast, dasatinib-incorporated PLGA nanoparticle injection significantly reduced the incidence of fold to 1 out of 10 eyes.

Conclusions

Injection of dasatinib-incorporated PLGA significantly reduced early fibrotic retinal changes which eventually lead to PVR following posterior ocular trauma. Thus, our sustained dasatinib release system can potentially be used to both prevent and/or broaden the surgical treatment window for PVR.

[Proliferative vitreoretinopathy prophylaxis : Mission (im)possible]

BACKGROUND

Proliferative vitreoretinopathy (PVR) is one of the most important complications following vitreoretinal surgery. So far, surgical strategies have been the gold standard in treatment. Pharmacological approaches for prevention and treatment of PVR are under clinical investigation and intervene in different phases of the PVR cascade.

METHODS

The relevant literature as well as own data and experience with PVR are discussed in this review article. The most important aspects of pharmacological approaches for PVR prophylaxis and treatment are explained.

RESULTS

A prophylactic use of systemic prednisone administration as an anti-inflammatory substance showed contradictory results, while there was no additional benefit for intravitreal triamcinolone. Orally administered isotretinoin also seems to be able to minimize the formation of PVR after retinal reattachment surgery, whereas there was no improvement in the success rate in established PVR. Cell proliferation inhibitors have already been extensively studied. The combined intravitreal prophylactic approach of 5‑fluorouracil and low molecular weight heparin was recently further investigated in a multicenter, placebo-controlled study and showed a positive effect in some studies. New preclinical and experimental approaches include the inhibition of growth factors, modulation of integrin activity and the induction of apoptosis.

CONCLUSION

Most clinical studies dealt with an anti-inflammatory or antiproliferative approach. So far, no pharmacological substance has been established for the treatment of PVR but there are promising approaches for prophylaxis.

The neuroregenerative effects of topical decorin on the injured mouse cornea

Background

The cornea is innervated with a rich supply of sensory nerves that play important roles in ocular surface health. Any injury or pathology of the corneal nerves increases the risk of dry eye disease and infection. This study aims to evaluate the therapeutic potential of topical decorin to improve corneal nerve regeneration in a mouse model of sterile epithelial abrasion injury.

Methods

Bilateral central corneal epithelial abrasions (2-mm, Alger Brush) were performed on young C57BL/6 J mice to remove the corneal sensory nerves. Decorin, or vehicle, was applied topically, three times per day for 1 week or every 2 h for 6 h. Spectral-domain optical coherence tomography was performed to measure the abrasion area and corneal thickness. Wholemount immunofluorescence staining was used to assess sensory nerve regeneration (β-tubulin III) and immune cell density (CD45, Iba1, CD11c). To investigate the specific role of dendritic cells (DCs), Cx3cr1^gfp/gfp mice, which spontaneously lack resident corneal epithelial DCs, were also investigated. The effect of prophylactic topical administration of recombinant human decorin (applied prior to the abrasion) was also investigated. Nerve tracing (NeuronJ software) was performed to compare recovery of basal nerve axons and superficial nerve terminals in the central and peripheral cornea.

Results

At 6 h after injury, topical decorin application was associated with greater intraepithelial DC recruitment but no change in re-epithelialisation or corneal thickness, compared to the vehicle control. One week after injury, sub-basal nerve plexus and superficial nerve terminal density were significantly higher in the central cornea in the decorin-treated eyes. The density of corneal stromal macrophages in the decorin-treated eyes and their contralateral eyes was significantly lower compared to saline-treated corneas. No significant improvement in corneal nerve regeneration was observed in Cx3cr1^gfp/gfp mice treated with decorin.

Conclusions

Decorin promotes corneal epithelial nerve regeneration after injury. The neuroregenerative effect of topical decorin was associated with a higher corneal DC density during the acute phase, and fewer macrophages at the study endpoint. The corneal neuroregenerative effects of decorin were absent in mice lacking intraepithelial DCs. Together, these findings support a role for decorin in DC-mediated neuroregeneration following corneal abrasion injury.

Inflammatory mediators of proliferative vitreoretinopathy: hypothesis and review

Purpose

To review the role of inflammatory mediators in proliferative vitreoretinopathy (PVR) development and the current treatment for PVR prevention.

Methods

A PubMed search was carried out using these keywords “PVR,” “inflammatory mediators,” “growth factors,” “cytokines” and “treatment.” Studies regarding inflammatory mediators and PVR therapy were included and published up to December 2019.

Results

Inflammatory mediators, namely growth factors and cytokines, have been implicated in the occurrence and development of PVR. Among various inflammatory mediators, transforming growth factor-β, platelet-derived growth factor, interleukin-6, interleukin-8 and tumor necrosis factor-α are considered to be particularly important. In this review, we focus on the hypothesis that growth factors and cytokines are involved in the development of PVR, and current treatment for the prevention of PVR.

Conclusion

We support the hypothesis that growth factors and cytokines may participate in the complex process of PVR development. More importantly, the identification of inflammatory mediators provides novel and efficacious therapeutic targets for the treatment of PVR.

Anti-Angiogenic and Anti-Scarring Dual Action of an Anti-Fibroblast Growth Factor 2 Aptamer in Animal Models of Retinal Disease

Currently approved therapies for age-related macular degeneration (AMD) are inhibitors against vascular endothelial growth factor (VEGF), which is a major contributor to the pathogenesis of neovascular AMD (nAMD). Intravitreal injections of anti-VEGF drugs have shown dramatic visual benefits for AMD patients. However, a significant portion of AMD patients exhibit an incomplete response to therapy and, over the extended management course, can lose vision, with the formation of submacular fibrosis as one risk factor. We investigated a novel target for AMD treatments, fibroblast growth factor 2 (FGF2), which has been implicated in the pathophysiology of both angiogenesis and fibrosis in a variety of tissue and organ systems. The anti-FGF2 aptamer, RBM-007, was examined for treatment of nAMD in animal models. In in vivo studies conducted in mice and rats, RBM-007 was able to inhibit FGF2-induced angiogenesis, laser-induced choroidal neovascularization (CNV), and CNV with fibrosis. Pharmacokinetic studies of RBM-007 in the rabbit vitreous revealed high and relatively long-lasting profiles that are superior to other approved anti-VEGF drugs. The anti-angiogenic and anti-scarring dual action of RBM-007 holds promise as an additive or alternative therapy to anti-VEGF treatments for nAMD.

Altered Decorin Biology in Proliferative Vitreoretinopathy: A Mechanistic and Cohort Study

Purpose

To determine if vitreous levels of the pro-fibrotic cytokine transforming growth factor beta2 (TGF-β2) and its opposing regulator decorin predict subsequent proliferative vitreoretinopathy (PVR) development in patients with rhegmatogenous retinal detachment (RRD).

Methods

We examined the effect of TGF-β2 and decorin on epithelial-mesenchymal transition (EMT) and collagen expression in vitro using ARPE-19 cells, and we analyzed extracellular matrix marker expression in PVR membrane and internal limiting membrane patient samples. We performed a prospective noninterventional cohort study, recruiting 125 patients undergoing vitrectomy for RRD and macular hole surgery, measured vitreous levels of TGF-β2 and decorin by ELISA, and followed them up for 6 months. Patients who did not develop PVR were compared to those who did, in order to determine whether vitreous TGF-β2 and decorin levels predicted PVR development.

Results

In vitro, TGF-β2 induced EMT and collagen production. Decorin strongly inhibited EMT and collagen production at high levels. PVR membranes expressed high levels of fibrosis-associated proteins, consistent with EMT. Vitreous TGF-β2 levels were unchanged between patients with macular holes and RRD who did or did not subsequently develop PVR. Average decorin levels were higher in the vitreous of RRD patients who subsequently developed PVR compared to those who did not, but at the measured vitreous concentrations (1-2 μg/mL), decorin did not demonstrate an in vitro inhibitory effect on EMT.

Conclusions

In vitro, high concentrations of decorin inhibited EMT and fibrosis. At the levels seen in human vitreous, decorin did not prevent fibrosis or EMT in vitro, and higher initial vitreous decorin levels were associated with the development of postoperative PVR after vitrectomy to treat RRD, but did not reliably predict the outcome.

Determining the effect of low-dose isotretinoin on proliferative vitreoretinopathy: the DELIVER trial

PURPOSE

To examine the effect of low-dose, oral isotretinoin in lowering the risk of proliferative vitreoretinopathy (PVR) following rhegmatogenous retinal detachment (RRD) repair.

METHODS

Prospective, open label, dual-cohort study with pathology-matched historical controls. The prospective experimental arms included two cohorts, composed of 51 eyes with recurrent PVR-related RRD and 58 eyes with primary RRD associated with high-risk features for developing PVR. Eyes in the experimental arms received 20 mg of isotretinoin by mouth once daily for 12 weeks starting the day after surgical repair. The primary outcome measure was single surgery anatomical success rate at 3 months following the study surgery.

RESULTS

The single surgery anatomic success rate was 78.4% versus 70.0% (p=0.358) in eyes with recurrent PVR-related retinal detachment exposed to isotretinoin versus historical controls, respectively. In eyes with RRD at high risk for developing PVR, the single surgery success rate was 84.5% versus 61.1% (p=0.005) for eyes exposed to isotretinoin versus historical controls, respectively. For eyes enrolled in the experimental arms, the most common isotretinoin-related side effects were dry skin/mucus membranes in 106 patients (97.2%), abnormal sleep/dreams in 4 patients (3.7%) and fatigue in 3 patients (2.8%).

CONCLUSION

The management and prevention of PVR is challenging and complex. At the dose and duration given in this study, oral istotretinoin may reduce the risk of PVR-associated recurrent retinal detachment in eyes with primary RRD at high risk of developing PVR.

Intravitreal decorin preventing proliferative vitreoretinopathy in perforating injuries: a pilot study

PURPOSE

To determine the short-term safety of human recombinant decorin protein in preventing proliferative vitreoretinopathy (PVR) in perforating injuries.

METHODS

This is a prospective, single-center, open-label, interventional case series. Single intravitreal injection of decorin 200 μg (n = 4) or 400 μg (n = 8) was given 48 h after injury. At the tenth day, pars plana vitrectomy was done whenever indicated. Flash electroretinogram (ERG) was done before and 3 months post-injection. We assessed ocular inflammation, ERG changes, and retinal layer integrity by optical coherence tomography (OCT). Systemic and vitreous pharmacokinetics were also evaluated.

RESULTS

Twelve patients (12 eyes) with perforating globe injuries (zone III) were included and followed for a median of 6 months. Intravitreal decorin injection was well tolerated with no ocular or systemic safety adverse events. Decorin retinal safety was demonstrated anatomically by intact retinal layer by OCT, and functionally by flash ERG which did not show any significant worsening during the study and the final mean logMAR best-corrected visual acuity (BCVA) which was 1.15 (20/280) and 0.7 (20/100) for groups A and B, respectively, and ≥ 20/200 in 75% of all eyes. Decorin serum and vitreous levels were elevated following trauma, with higher and extended levels following intravitreal injection.

CONCLUSIONS

No short-term safety concerns were detected after a single intravitreal injection of decorin in patients with perforating injuries.

TRIAL REGISTRATION

ClinicalTrials.gov ID: NCT02865031.

Outcomes and prognostic factors for aggressive posterior retinopathy of prematurity following initial treatment with intravitreal ranibizumab

Background

This study sought to identify factors associated with retinal detachment and retreatment of aggressive posterior retinopathy of prematurity (APROP) initially treated with intravitreal ranibizumab (IVR) injection as well as the efficacy of IVR treatment.

Methods

This was a retrospective study. A total of 83 preterm infants (160 eyes) diagnosed with APROP who were primarily treated with IVR were included. The 160 eyes were divided into two groups based on the anatomic outcomes. Group A included 35 eyes that developed retinal detachment, and Group B included 125 eyes without retinal detachment. The following patient factors were retrospectively reviewed: gender, gestational age (GA), birth weight (BW), postmenstrual age (PMA) at first treatment, iris neovascularizations, retinal hemorrhage, neutrophil and lymphocyte counts before the first intravitreal injection, neutrophil-to-lymphocyte ratio (NLR), anatomical outcomes, additional treatment and follow-up time. Three dummy variables were created as dependent variables based on the methods of retreatment. The possible risk factors for APROP were evaluated, and statistical analyses included univariate and multivariate logistic regression.

Results

A total of 160 eyes from 83 preterm infants (56 males and 27 females) underwent initial IVR treatment with a follow-up time of 17.17 ± 10.54 months. Thirty-five of the 160 (21.9%) eyes progressed to retinal detachment, and 82 of the 125 (65.6%) non-retinal detachment eyes needed retreatment, with favorable anatomical outcomes. The disease improved approximately 1.5 ± 1.2 weeks after the first IVR treatment. The mean recurrence period of APROP was approximately 7.5 ± 6.9 weeks after the first IVR treatment. Multiple logistic regression analysis revealed postmenstrual age (P < 0.001) and neutrophil count (P = 0.009) as the most significant factors for retinal detachment in APROP. Retinal hemorrhage (P = 0.007) and BW (P = 0.04) were most significantly associated with APROP recurrence and retreatment.

Conclusions

IVR injection is an effective treatment for APROP. In this study, older postmenstrual age and low neutrophil count were identified as risk factors for retinal detachment in APROP. In addition, retinal hemorrhage and low BW were significantly associated with recurrence and retreatment in non-retinal detachment APROP. Thus, patients with a lower BW, older postmenstrual age, low neutrophil count and retinal hemorrhage should be reexamined in a timely and more frequent manner.

TGF-β participates choroid neovascularization through Smad2/3-VEGF/TNF-α signaling in mice with Laser-induced wet age-related macular degeneration

Choroidal neovascularization(CNV) is the most severe complication in Age-related macular degeneration(AMD) and the most common cause of irreversible blindness in the elderly in developed world. The aim of this study was to identify the effect of transforming growth factor-β(TGF-β) and Smad2/3-VEGF/TNF-α signaling on CNV angiopoiesis, and to explore TGF-β inhibitors on the development of CNV in a CNV mouse model. Fundus fluorescein angiography(FFA) was used to evaluate the laser-induced CNV formation. The histology of CNV lesions stained with hematoxylin-eosin(HE) was obtained. The immunofluorescent staining was performed to determine TGF-β protein expression. The expressions of TGF-β, phosphorylated Smad2/3, VEGF and TNF-α were determined by using Western blot analysis. The CNV areas were analyzed by using fluorescein stain on RPE/choroid-sclera flat mounts. We found the levels of TGF-β protein expression increasingly reached the peak till 3rd week during the CNV development. The protein levels of VEGF and TNF-α also increased significantly in CNV mice, which were inhibited by a synthetic TGF-β inhibitor LY2157299 or a natural TGF-β inhibitor Decorin. The phosphorylated Smad2/3 levels increased significantly in CNV mice, but this response was profoundly suppressed by the TGF-β inhibitors. Here we have demonstrated that TGF-β/Smad signaling plays an important role in Laser-induced CNV formation through down-regulation of VEGF and TNF-α expressions, suggesting TGF-β inhibitors may provide an alternative to traditional methods in wet AMD treatment.

The influence of systemic renin-angiotensin-inhibition on ocular cytokines related to proliferative vitreoretinopathy

PURPOSE

The renin-angiotensin system is involved in the pathogenesis of fibrosis in several organs via induction of transforming growth factor (TGF) beta. In the pathogenesis of proliferative vitreoretinopathy (PVR) TGF-beta plays a pivotal role, promoting transition of retinal pigment epithelial (RPE) cells into myofibroblasts. We studied the influence of angiotensin converting enzyme-inhibition (ACEI) on cytokines and growth factors, related to PVR in aqueous humor.

METHODS

We performed a post hoc analysis of a prospectively conducted interventional case series. From patients with rhegmatogenous retinal detachment (RRD) aqueous humor was obtained during primary surgery and analyzed using multiplex bead analysis for interferon gamma, tumor necrosis factor alpha, CC-chemokine ligand (CCL) 2 / monocyte chemoattractant protein (MCP)-1, interleukin (IL)-1 beta, IL-2, IL-4, IL-6, IL-8, vascular endothelial growth factor (VEGF)-A, platelet derived growth factor (PDGF)-aa, TGF-beta 1, TGF-beta 2, TGF-beta 3, fibroblast growth factor (FGF)-aa, and FGF-bb. We recorded information about systemic ACEI from the medical history.

RESULTS

In the primary study elevated levels of TGF-beta 1 and 2, IL 6 and 8 and CCL2/MCP-1 were a risk factor for later PVR development. Here, systemic ACEI neither influenced levels of these cytokines and growth factors, nor of any other tested in this study (p ≥ 0.438, respectively). Also the incidence of PVR development was unaffected (p = 0.201).

CONCLUSION

The systemic intake of ACEI for arterial hypertension does not influence levels of profibrotic cytokines/growth factors in aqueous humor. Further studies need to clarify if relevant levels of ACEI accumulate in the eye, and if direct administration of ACEI in experimental PVR could be beneficial.

Pirfenidone inhibits post-traumatic proliferative vitreoretinopathy

PurposeThe purpose of the study was to evaluate the efficacy and safety of intravitreal pirfenidone for inhibition of proliferative vitreoretinopathy (PVR) in a model of penetrating ocular injury.Patients and methodsPenetrating trauma was induced on the retina of rabbit and treated either with 0.1 ml of phosphate-buffered saline (PBS) or 0.1 ml of 0.5% pirfenidone, and development of PVR was evaluated clinically and graded after 1 month. Histopathology and immunohistochemistry with transforming growth factor beta (TGFβ), alpha smooth muscle actin (αSMA), and collagen-1 were performed to assess the fibrotic changes. Expression of cytokines in the vitro-retinal tissues at different time points following pirfenidone and PBS injection was examined by RT-PCR. Availability of pirfenidone in the vitreous of rabbit at various time points was determined by high-performance liquid chromatography following injection of 0.1 ml of 0.5% pirfenidone. In normal rabbit eye, 0.1 ml of 0.5% pirfenidone was injected to evaluate any toxic effect.ResultsClinical assessment and grading revealed prevention of PVR formation in pirfenidone-treated animals, gross histology, and histopathology confirmed the observation. Immunohistochemistry showed prevention in the expression of collagen-I, αSMA, and TGFβ in the pirfenidone-treated eyes compared to the PBS-treated eyes. Pirfenidone inhibited increased gene expression of cytokines observed in control eyes. Pirfenidone could be detected up to 48 h in the vitreous of rabbit eye following single intravitreal injection. Pirfenidone did not show any adverse effect following intravitreal injection; eyes were devoid of any abnormal clinical sign, intraocular pressure, and electroretinography did not show any significant change and histology of retina remained unchanged.ConclusionThis animal study shows that pirfenidone might be a potential therapy for PVR. Further clinical study will be useful to evaluate the clinical application of pirfenidone.

The stereotypical molecular cascade in neovascular age-related macular degeneration: the role of dynamic reciprocity

This review summarises our current understanding of the molecular basis of subretinal neovascularisation (SRNV) in age-related macular degeneration (AMD). The term neovascular AMD (NVAMD) is derived from the dominant early clinical features of haemorrhage, fluid, and lipid in the subretinal space (SRS) and the historical role of fluorescein angiography in detecting the presence of NV tissue. However, at the cellular level, SRNV resembles an aberrant but stereotypical tissue repair response that incorporates both an early inflammatory phase and a late fibrotic phase in addition to the neovascular (NV) component that dominates the early clinical presentation. This review will seek not only to highlight the important molecules involved in each of these components but to demonstrate that the development of SRNV has its origins in the earliest events in non-NV AMD pathogenesis. Current evidence suggests that this early-stage pathogenesis is characterised by complement-mediated immune dysregulation, leading to a state of chronic inflammation in the retinal pigment epithelium/Bruch's membrane/choriocapillaris complex. These initial events can be seamlessly and inextricably linked to late-stage development of SRNV in AMD by the process of dynamic reciprocity (DyR), the ongoing bidirectional communication between cells, and their surrounding matrix. Moreover, this correlation between disease onset and eventual outcome is reflected in the temporal and spatial correlation between chronic inflammation, NV, and fibrosis within the reparative microenvironment of the SRS. In summary, the downstream consequences of the earliest dysfunctional molecular events in AMD can result in the late-stage entity we recognize clinically as SRNV and is characterized by a spectrum of predictable, related, and stereotypical processes referred to as DyR.

A TGF-β receptor 1 inhibitor for prevention of proliferative vitreoretinopathy

This study evaluates the use of the TGF-β receptor 1 inhibitor LY-364947 (LY) to prevent proliferative vitreoretinopathy (PVR). For the in vitro experiments Human Tenon's Fibroblasts (HTFs) and retinal pigment epithelial (RPE) cells were treated with different concentrations of LY to determine HTF proliferation and RPE transdifferentiation. For in vivo testing 30 rabbits underwent a PVR trauma model. The animals received different concentrations of intravitreally injected LY, with or without vitrectomy. LY treatment reduced HTF proliferation and RPE transdifferentiation in vitro. In vivo intravitreal injection of LY prevented PVR development significantly. This positive effect was also present when LY injection was combined with vitrectomy. Intravitreal injection of LY prevented tractional retinal detachment in 14 out of 15 animals. In conclusion, treatment with the TGF-β receptor 1 inhibitor LY reduces HTF proliferation and RPE transdifferentiation in vitro and prevents proliferative vitreoretinopathy and subsequent tractional retinal detachment in vivo.

Expression of IGFBP-6 in a proliferative vitreoretinopathy rat model and its effects on retinal pigment epithelial cell proliferation and migration

AIM

To investigate the expression of insulin-like growth factor binding protein-6 (IGFBP-6) in a proliferative vitreoretinopathy (PVR) model and its effects on proliferation and migration in retinal pigment epithelial (RPE) cells.

METHODS

A PVR Wistar rat model was established by the intravitreal injection of RPE-J cells combined with platelet-rich plasma (PRP). The expression levels of IGFBP-6 were tested by ELISA. ARPE-19 cell proliferation was evaluated by the MTS method, and cell migration was evaluated by wound healing assays.

RESULTS

The success rate of the PVR model was 89.3% (25/28). IGFBP-6 was expressed at higher levels in the vitreous, serum and retina of rats experiencing advanced PVR (grade 3) than in the control group (vitreous: 152.80±15.08ng/mL vs 105.44±24.81ng/mL, P>0.05; serum: 93.48±9.27ng/mL vs 80.59±5.20ng/mL, P<0.05; retina: 3.02±0.38ng/mg vs 2.05±0.53ng/mg, P<0.05). In vitro, IGFBP-6 (500ng/mL) inhibited the IGF-II (50ng/mL) induced ARPE-19 cell proliferation (OD value at 24h: from 1.38±0.05 to 1.30±0.02; 48h: from 1.44±0.06 to 1.35±0.05). However, it did not affect basal or VEGF-, TGF-β- and PDGF-induced cell proliferation. IGFBP-6 (500ng/mL) reduced the IGF-II (50ng/mL)-induced would healing rate [24h: from (43.91±3.85)% to (29.76±2.49)%; 48 h: from (66.09±1.67)% to (59.88±3.43)%].

CONCLUSION

Concentrations of IGFBP-6 increased in the vitreous, serum, and retinas only in advanced PVR in vivo. IGFBP-6 also inhibited IGF-II-induced cell proliferation in a not dose or time dependent manner and migration. IGFBP-6 participates in the development of PVR and might play a protective role in PVR.

Is neutralizing vitreal growth factors a viable strategy to prevent proliferative vitreoretinopathy?

Proliferative vitreoretinopathy (PVR) is a blinding disorder that occurs in eyes with rhegmatogenous retinal detachment and in eyes that have recently undergone retinal detachment surgery. There are presently no treatment strategies to reduce the risk of developing PVR in eyes with retinal detachment, and surgical intervention is the only option for eyes with retinal detachment and established PVR. Given the poor visual outcome associated with the surgical treatment of PVR, considerable work has been done to identify pharmacologic agents that could antagonize the PVR process. Intensive efforts to identify molecular determinants of PVR implicate vitreal growth factors. A surprise that emerged in the course of testing the 'growth factor hypothesis' of PVR was the existence of a functional relationship amongst growth factors that engage platelet-derived growth factor (PDGF) receptor α (PDGFRα), a receptor tyrosine kinase that is key to pathogenesis of experimental PVR. Vascular endothelial cell growth factor A (VEGF), which is best known for its ability to activate VEGF receptors (VEGFRs) and induce permeability and/or angiogenesis, enables activation of PDGFRα by a wide spectrum of vitreal growth factors outside of the PDGF family (non-PDGFs) in a way that triggers signaling events that potently enhance the viability of cells displaced into vitreous. Targeting these growth factors or signaling events effectively neutralizes the bioactivity of PVR vitreous and prevents PVR in a number of preclinical models. In this review, we discuss recent conceptual advances in understanding the role of growth factors in PVR, and consider the tangible treatment strategies for clinical application.

Müller glia: Stem cells for generation and regeneration of retinal neurons in teleost fish

Adult zebrafish generate new neurons in the brain and retina throughout life. Growth-related neurogenesis allows a vigorous regenerative response to damage, and fish can regenerate retinal neurons, including photoreceptors, and restore functional vision following photic, chemical, or mechanical destruction of the retina. Müller glial cells in fish function as radial-glial-like neural stem cells. During adult growth, Müller glial nuclei undergo sporadic, asymmetric, self-renewing mitotic divisions in the inner nuclear layer to generate a rod progenitor that migrates along the radial fiber of the Müller glia into the outer nuclear layer, proliferates, and differentiates exclusively into rod photoreceptors. When retinal neurons are destroyed, Müller glia in the immediate vicinity of the damage partially and transiently dedifferentiate, re-express retinal progenitor and stem cell markers, re-enter the cell cycle, undergo interkinetic nuclear migration (characteristic of neuroepithelial cells), and divide once in an asymmetric, self-renewing division to generate a retinal progenitor. This daughter cell proliferates rapidly to form a compact neurogenic cluster surrounding the Müller glia; these multipotent retinal progenitors then migrate along the radial fiber to the appropriate lamina to replace missing retinal neurons. Some aspects of the injury-response in fish Müller glia resemble gliosis as observed in mammals, and mammalian Müller glia exhibit some neurogenic properties, indicative of a latent ability to regenerate retinal neurons. Understanding the specific properties of fish Müller glia that facilitate their robust capacity to generate retinal neurons will inform and inspire new clinical approaches for treating blindness and visual loss with regenerative medicine.

Proliferative vitreoretinopathy after eye injuries: an overexpression of growth factors and cytokines leading to a retinal keloid

Eye injury is a significant disabling worldwide health problem. Proliferative Vitreoretinopathy (PVR) is a common complication that develops in up to 40–60% of patients with an open-globe injury. Our knowledge about the pathogenesis of PVR has improved in the last decades. It seems that the introduction of immune cells into the vitreous, like in penetrating ocular trauma, triggers the production of growth factors and cytokines that come in contact with intra-retinal cells, like Müller cells and RPE cells. Growth factors and cytokines drive the cellular responses leading to PVR's development. Knowledge of the pathobiological and pathophysiological mechanisms involved in posttraumatic PVR is increasing the possibilities of management, and it is hoped that in the future our treatment strategies will evolve, in particular adopting a multidrug approach, and become even more effective in vision recovery. This paper reviews the current literature and clinical trial data on the pathogenesis of PVR and its correlation with ocular trauma and describes the biochemical/molecular events that will be fundamental for the development of novel treatment strategies. This literature review included PubMed articles published from 1979 through 2013. Only studies written in English were included.

Upregulation of TGF-ß1 in experimental proliferative vitreoretinopathy is accompanied by epithelial to mesenchymal transition

BACKGROUND

Proliferative vitreoretinopathy (PVR) is characterized by epithelial to mesenchymal transition (EMT) of retinal pigment epithelium (RPE) cells and consecutive formation of fibrous membranes, leading to retinal redetachment. Transforming growth factor beta (TGF-ß) has been suggested to play an important role in this process, but the role of TGF-ß isoforms is unknown.

METHODS

In pigmented rabbits (n = 14), PVR was induced by cryopexy and a full-thickness limbus-parallel incision. PVR was evaluated by indirect ophthalmoscopy. Concentrations of TGF-ß isoforms were determined by multiplex bead assay analysis in aqueous humor (AH) and vitreous samples. EMT marker vimentin was analyzed by western blot. Masson's-trichrome, haematoxilin and eosine (H&E), and immunohistochemical analysis for EMT marker alpha SMA were performed on cross-sections of eyes.

RESULTS

PVR was induced in all treated eyes. The number of quadrants affected by PVR was 1 (n = 5), 2 (n = 2), 3 (n = 2), 4 (n = 5). Vimentin and alpha SMA were expressed during PVR development. During PVR development, both TGF-ß1 levels (AH: p = 0.001; vitreous: p = 0.002) and TGF-ß2 levels increased (AH: p = 0.027; vitreous: p = 0.02), while TGF-ß3 was not detected at any timepoint. The increase was more pronounced for TGF-ß1 than for TGF- ß2 (AH: p = 0.002; vitreous: p = 0.0005), and only TGF-ß1 correlated with the amount of PVR (p = 0.024, r = 0,723).

CONCLUSIONS

Development of PVR membranes was accompanied by a pronounced upregulation of TGF-ß1, rather than TGF-ß2. Therefore TGF-ß1 could be a promising target for inhibition of PVR.

Proliferative vitreoretinopathy: current and emerging treatments

Proliferative vitreoretinopathy is a disease process that follows the proliferation of ectopic cell sheets in the vitreous and/or periretinal area, causing periretinal membrane formation and traction, in patients with rhegmatogenous retinal detachments. Currently, vitreous surgery is the standard treatment; however, the results aren't satisfactory given the vision loss that ensues and that redetachment is relatively common. It is becoming clearer that there exists an interplay between various cytokines/growth factors, matrix proteins, and the different cell types that drive the undesirable formation of periretinal membranes. This fundamental understanding is aiding in identifying different adjunct agents that can block the cellular events intrinsic to proliferative vitreoretinopathy. In this review, we describe the current understanding on the pathogenesis and discuss how the fundamental understanding of the biochemical/molecular events is instrumental in developing the novel treatment strategies that are also highlighted.