Systemic and Intraocular Methotrexate for the Prevention and Treatment of Proliferative Vitreoretinopathy in Children With Rhegmatogenous Retinal Detachment and Underlying Inflammatory Disease

PURPOSE

This index study highlights the efficacy and safety of a combined surgical and medical therapy (with intraocular and systemic methotrexate) of pediatric rhegmatogenous retinal detachments (RRD) complicated by proliferative vitreoretinopathy (PVR).

METHODS

Three pediatric patients with RRD complicated by PVR in the setting of underlying atopic dermatitis and/or uveitis who were treated with a combination of vitreoretinal surgery and intraoperative intravitreal methotrexate (MTX) (40mg) infusion, followed by at least one injection of 200 μg of MTX into the silicone oil-filled vitreous cavity, are reported. In addition, the patients received short-term systemic immunosuppression with systemic (oral or subcutaneous 20 mg weekly MTX for 12 weeks) and/or steroids.

RESULTS

Retinal reattachment with improvement in visual acuity was achieved in all eyes following a single surgery and remained to the final follow-up examination after oil removal. There were no observed side effects of intraocular or systemic MTX.

CONCLUSIONS

The safety and efficacy of this combination therapy suggests that it could be a successful strategy for treating pediatric patients with RRD with or without PVR in the presence or absence of underlying inflammatory diseases.

Doxycycline Ameliorates the Severity of Experimental Proliferative Vitreoretinopathy in Mice

After successful surgeries for patients with rhegmatogenous retinal detachment, the most common cause of retinal redetachment is proliferative vitreoretinopathy (PVR), which causes severe vision impairment and even blindness worldwide. Until now, the major treatment for PVR is surgical removal of the epiretinal membrane, while effective treatment to prevent PVR is still unavailable. Therefore, we investigated the potential of doxycycline, an antibiotic in the tetracycline class, to treat PVR using a mouse model. We used the human retinal pigment epithelial cell line, ARPE-19, for in vitro and in vivo studies to test doxycycline for PVR treatment. We found that doxycycline suppressed the migration, proliferation, and contraction of ARPE-19 cells with reduced p38 MAPK activation and total MMP activity. Intravitreal doxycycline and topical tetracycline treatment significantly ameliorated the PVR severity induced by ARPE-19 cells in mice. PVR increased the expression of MMP-9 and IL-4 and p38 MAPK phosphorylation and modestly decreased IL-10. These effects were reversed by doxycycline and tetracycline treatment in the mouse retina. These results suggest that doxycycline will be a potential treatment for PVR in the future.

A sustained dual drug delivery system for proliferative vitreoretinopathy

Proliferative vitreoretinopathy (PVR) is a significant threat for vision recovery from retinal detachment or ocular trauma. Currently, no approved pharmacological intervention to prevent PVR. Daunorubicin (DNR) and dexamethasone (DEX) were sequentially loaded into oxidized porous silicon (pSiO₂) particles by covalent conjugation. The DNR + DEX-loaded particles, and control particles loaded with DNR only and DEX only were incubated with RPE-populated collagen for daily gel surface quantitation. Toxicity was monitored by ophthalmic examinations and histological evaluation 21 days after injection. At 3rd week following intravitreal injection, a localized retinal detachment (RD) was created by subretinal injection of Healon in all pretreated eyes in addition to 3 non-interventional control eyes. 10 µg of bromodeoxyuridine (BrdU) was injected into the vitreous 4 h before sacrifice on day 3 after RD induction. Retinal sections were stained for glial fibrillary green protein (GFAP) and BrdU to identify activated glial cells and retinal cell proliferation. The studies demonstrated that all three pSiO₂ particle types were well tolerated in vivo. DNR alone and DNR + DEX combination formulations demonstrated equally strong suppression on gel contraction (least square mean area of the gel: control = 1.71 vs. 30DNR = 1.85 or 30/40Dual = 1.83, p < .05). Eyes pretreated with pSiO₂−DNR + DEX exhibited the least GFAP activation (least square mean intensity mm⁻²: Dual = 4.03, DNR = 7.76, Dex = 16.23, control = 29.11, p < .05) and BrdU expression (Mean number of BrdU positive cells per mm of retina: Dual = 2.77, DNR = 4.58, Dex = 4.01, control = 6.16, p < .05). The synergistic effect of a sustained release pSiO₂−DNR/DEX showed promise for the prevention of PVR development while reducing the necessary therapeutic concentration of each drug.

Major challenges in vitreoretinal surgery

Since the first vitrectomy surgery was used for treatment of vitreoretinal diseases, surgical techniques and instrumentation have been rapidly improved in the past decades. However, there are complicated vitreoretinal diseases that cannot be successfully treated, even with state-of-the-art surgeries. The outcomes of some complicated cases are still poor due to different reasons and debates still remain in some areas regarding what are the best treatments. There is still a lack of full understanding on many complicated vitreoretinal diseases, such as the molecular basis of proliferative vitreoretinopathy (PVR), the role of scleral buckling (SB) in the management of rhegmatogenous retinal detachment (RRD), the optimal surgical consideration for pediatric RD, and the possibility of surgical management for various retinal degenerations and congenital retinal anomalies. This review discusses the current understandings of some complicated vitreoretinal diseases.

The role of thrombin in proliferative vitreoretinopathy

PURPOSE

To determine the role of thrombin in the development of proliferative vitreoretinopathy (PVR).

METHODS

Vitreous was collected from patients undergoing a vitrectomy (macular holes and puckers, n = 11 [controls]; retinal detachment without PVR development following vitrectomy, n = 15 [RRD1]; retinal detachment with PVR development within 6 months after vitrectomy, n = 11 [RRD2]; and established PVR, n = 14 [PVR]). Thrombin activity in vitreous was determined using a thrombin-specific chromogenic substrate. ARPE-19 cells were stimulated with 8× diluted vitreous samples in the presence and absence of hirudin. The samples were analyzed at t = 0 and t = 24 hours for the presence of 27 cytokines/chemokines and growth factors using a multiplex approach. In comparable studies, ARPE-19 cells were stimulated for 2 hours, and mRNA expression levels for CCL2, CXCL8, GMCSF, IL6, and PDGFB were determined by real-time quantitative (RQ)-PCR.

RESULTS

Thrombin activity was significantly (P < 0.05) higher in vitreous of the PVR group compared to the other groups. Proliferative vitreoretinopathy vitreous stimulated the production of chemokine (C-C motif) ligand (CCL)2, chemokine (C-X-C motif) ligand (CXCL)8, granulocyte-macrophage colony-stimulating factor (GM-CSF), IL-6, and platelet-derived growth factor (PDGF)-BB by ARPE-19 to significantly (P < 0.05) higher levels than vitreous from the RRD1 and RRD2 groups. These effects of PVR vitreous were significantly (P < 0.05) reduced by hirudin. These data were confirmed by mRNA studies.

CONCLUSIONS

Thrombin activity is increased in vitreous of patients with established PVR and is involved in the activation of proinflammatory and profibrotic pathways in RPE cells. Inhibition of thrombin activity may therefore represent a potential treatment option for proliferative vitreoretinopathy.

Trichostatin A, a histone deacetylase inhibitor, suppresses proliferation and epithelial-mesenchymal transition in retinal pigment epithelium cells

The proliferation and epithelial-mesenchymal transition (EMT) of retinal pigment epithelium (RPE) cells are the major pathological changes in development of proliferative vitreoretinopathy (PVR), which leads to severe visual impairment. Histone deacetylases (HDACs)-mediated epigenetic mechanisms play important roles in controlling various physiological and pathological events. However, whether HDACs are involved in the regulation of proliferation and EMT in PRE cells remains unidentified. In this study, we evaluated the expression profile of HDAC family (18 genes) and found that some of class I and class II HDACs were up-regulated in transforming growth factor-β2 (TGF-β2)/TGF-β1-stimulated RPE cells. Tricostatin A (TSA), a class I and II HDAC inhibitor, suppressed the proliferation of RPE cells by G1 phase cell cycle arrest through inhibition of cyclin/CDK/p-Rb and induction of p21 and p27. In the meantime, TSA strongly prevented TGF-β2-induced morphological changes and the up-regulation of α-SMA, collagen type I, collagen type IV, fibronectin, Snail and Slug. We also demonstrated that TSA affected not only the canonical Smad signalling pathway but also the non-canonical TGF-β/Akt, MAPK and ERK1/2 pathways. Finally, we found that the underlying mechanism of TSA affects EMT in RPE cells also through down-regulating the Jagged/Notch signalling pathway. Therefore, this study may provide a new insight into the pathogenesis of PVR, and suggests that epigenetic treatment with HDAC inhibitors may have therapeutic value in the prevention and treatment of PVR.

Thrombin induces epithelial-mesenchymal transition and collagen production by retinal pigment epithelial cells via autocrine PDGF-receptor signaling

PURPOSE

De-differentiation of RPE cells into mesenchymal cells (epithelial-mesenchymal transition; EMT) and associated collagen production contributes to development of proliferative vitreoretinopathy (PVR). In patients with PVR, intraocular coagulation cascade activation occurs and may play an important initiating role. Therefore, we examined the effect of the coagulation proteins factor Xa and thrombin on EMT and collagen production by RPE cells.

METHODS

Retinal pigment epithelial cells were stimulated with factor Xa or thrombin and the effect on zonula occludens (ZO)-1, α-smooth muscle actin (α-SMA), collagen, and platelet-derived growth factor (PDGF)-B were determined by real-time quantitative-polymerase chain reaction (RQ-PCR), immunofluorescence microscopy, and HPLC and ELISA for collagen and PDGF-BB in culture supernatants, respectively. PDGF-receptor activation was determined by phosphorylation analysis and inhibition studies using the PDGF-receptor tyrosine kinase inhibitor AG1296.

RESULTS

Thrombin reduced ZO-1 gene expression (P < 0.05) and enhanced expression of the genes encoding α-SMA and the pro-alpha1 chain of collagen type-1 (P < 0.05), indicating EMT. Also, ZO-1 protein expression declined on thrombin stimulation, whereas production of α-SMA and collagen increased. In contrast to thrombin, factor Xa hardly stimulated EMT by RPE. Thrombin clearly induced PDGF-BB production and PDGF-Rβ chain phosphorylation in RPE. Moreover, AG1296 significantly blocked the effect of thrombin on EMT and collagen production.

CONCLUSIONS

Our findings demonstrate that thrombin is a potent inducer of EMT by RPE via autocrine activation of PDGF-receptor signaling. Coagulation cascade-induced EMT of RPE may thus contribute to the formation of fibrotic retinal membranes in PVR and should be considered as treatment target in PVR.

Regulation of Na,K-ATPase β1-subunit in TGF-β2-mediated epithelial-to-mesenchymal transition in human retinal pigmented epithelial cells

Proliferative vitreo retinopathy (PVR) is associated with extracellular matrix membrane (ECM) formation on the neural retina and disruption of the multilayered retinal architecture leading to distorted vision and blindness. During disease progression in PVR, retinal pigmented epithelial cells (RPE) lose cell-cell adhesion, undergo epithelial-to-mesenchymal transition (EMT), and deposit ECM leading to tissue fibrosis. The EMT process is mediated via exposure to vitreous cytokines and growth factors such as TGF-β2. Previous studies have shown that Na,K-ATPase is required for maintaining a normal polarized epithelial phenotype and that decreased Na,K-ATPase function and subunit levels are associated with TGF-β1-mediated EMT in kidney cells. In contrast to the basolateral localization of Na,K-ATPase in most epithelia, including kidney, Na,K-ATPase is found on the apical membrane in RPE cells. We now show that EMT is also associated with altered Na,K-ATPase expression in RPE cells. TGF-β2 treatment of ARPE-19 cells resulted in a time-dependent decrease in Na,K-ATPase β1 mRNA and protein levels while Na,K-ATPase α1 levels, Na,K-ATPase activity, and intracellular sodium levels remained largely unchanged. In TGF-β2-treated cells reduced Na,K-ATPase β1 mRNA inversely correlated with HIF-1α levels and analysis of the Na,K-ATPase β1 promoter revealed a putative hypoxia response element (HRE). HIF-1α bound to the Na,K-ATPase β1 promoter and inhibiting the activity of HIF-1α blocked the TGF-β2 mediated Na,K-ATPase β1 decrease suggesting that HIF-1α plays a potential role in Na,K-ATPase β1 regulation during EMT in RPE cells. Furthermore, knockdown of Na,K-ATPase β1 in ARPE-19 cells was associated with a change in cell morphology from epithelial to mesenchymal and induction of EMT markers such as α-smooth muscle actin and fibronectin, suggesting that loss of Na,K-ATPase β1 is a potential contributor to TGF-β2-mediated EMT in RPE cells.