Retina

Chen J, Michan S, Juan AM, Hurst CG, Hatton CJ, Pei DT, Joyal J-S, Evans LP, Cui Z, Stahl A, Sapieha P, Sinclair DA, Smith LEH. Neuronal sirtuin1 mediates retinal vascular regeneration in oxygen-induced ischemic retinopathy. Angiogenesis 2013;16(4):985-92.Abstract
Regeneration of blood vessels in ischemic neuronal tissue is critical to reduce tissue damage in diseases. In proliferative retinopathy, initial vessel loss leads to retinal ischemia, which can induce either regrowth of vessels to restore normal metabolism and minimize damage, or progress to hypoxia-induced sight-threatening pathologic vaso-proliferation. It is not well understood how retinal neurons mediate regeneration of vascular growth in response to ischemic insults. In this study we aim to investigate the potential role of Sirtuin 1 (Sirt1), a metabolically-regulated protein deacetylase, in mediating the response of ischemic neurons to regulate vascular regrowth in a mouse model of oxygen-induced ischemic retinopathy (OIR). We found that Sirt1 is highly induced in the avascular ischemic retina in OIR. Conditional depletion of neuronal Sirt1 leads to significantly decreased retinal vascular regeneration into the avascular zone and increased hypoxia-induced pathologic vascular growth. This effect is likely independent of PGC-1α, a known Sirt1 target, as absence of PGC-1α in knockout mice does not impact vascular growth in retinopathy. We found that neuronal Sirt1 controls vascular regrowth in part through modulating deacetylation and stability of hypoxia-induced factor 1α and 2α, and thereby modulating expression of angiogenic factors. These results indicate that ischemic neurons induce Sirt1 to promote revascularization into ischemic neuronal areas, suggesting a novel role of neuronal Sirt1 in mediating vascular regeneration in ischemic conditions, with potential implications beyond retinopathy.
Englander M, Chen TC, Paschalis EI, Miller JW, Kim IK. Intravitreal injections at the Massachusetts Eye and Ear Infirmary: analysis of treatment indications and postinjection endophthalmitis rates. Br J Ophthalmol 2013;97(4):460-5.Abstract
AIM: To report the incidence rate of acute postoperative endophthalmitis secondary to therapeutic intravitreal injections. METHODS: A retrospective review of all consecutive eyes after intravitreal injections was performed at the Massachusetts Eye and Ear Infirmary, Boston, from 1 January 2007 to 31 December 2011. RESULTS: During the 5-year study interval, 10 208 intravitreal injections were performed. The overall incidence rate of endophthalmitis was 0.029% per injection (3 of 10 208 injections). In the three cases, in our series, the endophthalmitis occurred at an average of seven injections, which lies within the SD of the mean number of injections received by each eye in this study, suggesting approximately equal probability of infection for each eye after receiving multiple, sequential injections. Bacterial cultures and Gram stain revealed coagulase-negative Staphylococcus species (n=1), moderate bacteria with negative culture (n=1) and moderate Staphylococcus epidermidis (n=1). All cases were successfully treated using either intravitreal antibiotics and steroids or pars plana vitrectomy. Best-corrected visual acuity reduction was not clinically significant at the last visit (>7 months for all cases). CONCLUSIONS: Acute endophthalmitis is a rare potential complication after intravitreal injection. Further studies are required to elucidate the best prophylactic and aseptic techniques to prevent this rare complication.
Takeuchi K, Morizane Y, Kamami-Levy C, Suzuki J, Kayama M, Cai W, Miller JW, Vavvas DG. AMP-dependent kinase inhibits oxidative stress-induced caveolin-1 phosphorylation and endocytosis by suppressing the dissociation between c-Abl and Prdx1 proteins in endothelial cells. J Biol Chem 2013;288(28):20581-91.Abstract
Caveolin-1 is the primary structural component of endothelial caveolae that is essential for transcellular trafficking of albumin and is also a critical scaffolding protein that regulates the activity of signaling molecules in caveolae. Phosphorylation of caveolin-1 plays a fundamental role in the mechanism of oxidant-induced vascular hyper permeability. However, the regulatory mechanism of caveolin-1 phosphorylation remains unclear. Here we identify a previously unexpected role for AMPK in inhibition of caveolin-1 phosphorylation under oxidative stress. A pharmacological activator of AMPK, 5-amino-4-imidazole carboxamide riboside (AICAR), inhibited oxidative stress-induced phosphorylation of both caveolin-1 and c-Abl, which is the major kinase of caveolin-1, and endocytosis of albumin in human umbilical vein endothelial cell. These effects were abolished by treatment with two specific inhibitors of AICAR, dipyridamole, and 5-iodotubericidin. Consistently, knockdown of the catalytic AMPKα subunit by siRNA abolished the inhibitory effect of AICAR on oxidant-induced phosphorylation of both caveolin-1 and c-Abl. Pretreatment with specific c-Abl inhibitor, imatinib mesylate, and knock down of c-Abl significantly decreased the caveolin-1 phosphorylation after H2O2 exposure and abolished the inhibitory effect of AICAR on the caveolin-1 phosphorylation. Interestingly, knockdown of Prdx-1, an antioxidant enzyme associated with c-Abl, increased phosphorylation of both caveolin-1 and c-Abl and abolished the inhibitory effect of AICAR on the caveolin-1 phosphorylation. Furthermore, co-immunoprecipitation experiment showed that AICAR suppressed the oxidant-induced dissociation between c-Abl and Prdx1. Overall, our results suggest that activation of AMPK inhibits oxidative stress-induced caveolin-1 phosphorylation and endocytosis, and this effect is mediated in part by stabilizing the interaction between c-Abl and Prdx-1.
Yonekawa Y, MacDonald SM, Shildkrot Y, Mukai S. Standard fractionation low-dose proton radiotherapy for diffuse choroidal hemangiomas in pediatric Sturge-Weber syndrome. J AAPOS 2013;17(3):318-22.Abstract
Sturge-Weber syndrome is a nonhereditary congenital neurocutaneous syndrome characterized by leptomeningeal angiomatosis, facial nevus flammeus, and diffuse choroidal hemangioma, which when complicated by total retinal detachment, portend a poor prognosis. Management is often limited to salvage external beam irradiation. We present a modified proton therapy technique for young children with total bullous retinal detachments that uses standard fractionation low-dose proton radiotherapy to decrease the risk of radiation complications. Treatment techniques for young children who cannot cooperate with conventional radiation protocols are also described.
Theodoropoulou S, Brodowska K, Kayama M, Morizane Y, Miller JW, Gragoudas ES, Vavvas DG. Aminoimidazole carboxamide ribonucleotide (AICAR) inhibits the growth of retinoblastoma in vivo by decreasing angiogenesis and inducing apoptosis. PLoS One 2013;8(1):e52852.Abstract
5-Aminoimidazole-4-carboxamide-1-β-4-ribofuranoside (AICAR), an analog of AMP is widely used as an activator of AMP-kinase (AMPK), a protein that regulates the responses of the cell to energy change. Recently, we showed that AICAR-induced AMPK activation inhibits the growth of retinoblastoma cells in vitro by decreasing cyclins and by inducing apoptosis and S-phase arrest. In this study, we investigated the effects of AMPK activator AICAR on the growth of retinoblastoma in vivo. Intraperitoneal injection of AICAR resulted in 48% growth inhibition of Y79 retinoblastoma cell tumors in mice. Tumors isolated from mice treated with AICAR had decreased expression of Ki67 and increased apoptotic cells (TUNEL positive) compared with the control. In addition, AICAR treatment suppressed significantly tumor vessel density and macrophage infiltration. We also showed that AICAR administration resulted in AMPK activation and mTOR pathway inhibition. Paradoxically observed down-regulation of p21, which indicates that p21 may have a novel function of an oncogene in retinoblastoma tumor. Our results indicate that AICAR treatment inhibited the growth of retinoblastoma tumor in vivo via AMPK/mTORC1 pathway and by apoptogenic, anti-proliferative, anti-angiogenesis mechanism. AICAR is a promising novel non-chemotherapeutic drug that may be effective as an adjuvant in treating Retinoblastoma.
Yonekawa Y, Shildkrot Y, Eliott D. Inferior peripheral nonperfusion in bilateral diffuse uveal melanocytic proliferation. Ophthalmic Surg Lasers Imaging Retina 2013;44(2):190-2.Abstract
Bilateral diffuse uveal melanocytic proliferation (BDUMP) is a paraneoplastic syndrome characterized by cataract, photoreceptor loss and subretinal fluid overlying patchy areas of retinal pigment epithelium atrophy, and a diffusely thickened choroid with focal nodules. We present the case of a 64-year-old woman with a history of endometrial adenocarcinoma who developed BDUMP with bilateral exudative retinal detachments with inferior peripheral retinal ischemia. This new finding of peripheral nonperfusion expands the spectrum of BDUMP.
Smith LE, Hard A-L, Hellström A. The biology of retinopathy of prematurity: how knowledge of pathogenesis guides treatment. Clin Perinatol 2013;40(2):201-14.Abstract
Retinopathy of prematurity occurs because the retina of a preterm infant at birth is incompletely vascularized, and if the postnatal environment does not match the in utero environment that supported retinal development, the vessels and neural retina will not grow normally. Risk factors determined from many clinical studies and animal studies fall into 2 categories: prenatal factors and postnatal factors.
Pennock S, Kim D, Mukai S, Kuhnle M, Chun DW, Matsubara J, Cui J, Ma P, Maberley D, Samad A, Van Geest RJ, Oberstein SL, Schlingemann RO, Kazlauskas A. Ranibizumab is a potential prophylaxis for proliferative vitreoretinopathy, a nonangiogenic blinding disease. Am J Pathol 2013;182(5):1659-70.Abstract
Proliferative vitreoretinopathy (PVR) exemplifies a disease that is difficult to predict, lacks effective treatment options, and substantially reduces the quality of life of an individual. Surgery to correct a rhegmatogenous retinal detachment fails primarily because of PVR. Likely mediators of PVR are growth factors in vitreous, which stimulate cells within and behind the retina as an inevitable consequence of a breached retina. Three classes of growth factors [vascular endothelial growth factor A (VEGF-A), platelet-derived growth factors (PDGFs), and non-PDGFs (growth factors outside of the PDGF family)] are relevant to PVR pathogenesis because they act on PDGF receptor α, which is required for experimental PVR and is associated with this disease in humans. We discovered that ranibizumab (a clinically approved agent that neutralizes VEGF-A) reduced the bioactivity of vitreous from patients and experimental animals with PVR, and protected rabbits from developing disease. The apparent mechanism of ranibizumab action involved derepressing PDGFs, which, at the concentrations present in PVR vitreous, inhibited non-PDGF-mediated activation of PDGF receptor α. These preclinical findings suggest that available approaches to neutralize VEGF-A are prophylactic for PVR, and that anti-VEGF-based therapies may be effective for managing more than angiogenesis- and edema-driven pathological conditions.
Schneider EW, Elner SG, van Kuijk FJ, Goldberg N, Lieberman RM, Eliott D, Johnson MW. Chronic retinal necrosis: cytomegalovirus necrotizing retinitis associated with panretinal vasculopathy in non-HIV patients. Retina 2013;33(9):1791-9.Abstract
PURPOSE: To characterize a unique cytomegalovirus (CMV)-associated retinopathy in patients with limited immune dysfunction. METHODS: Retrospective observational case series. CMV was confirmed as the pathogenic agent via polymerase chain reaction analysis of aqueous or vitreous humor samples or via immunohistochemical analysis of retinal biopsy specimens. RESULTS: Five non-HIV patients with granular necrotizing retinitis, vitritis, and severe occlusive vasculopathy were identified. Patient histories all suggested a basis for limited immune dysfunction including advanced age (n = 4), diabetes mellitus (n = 4), and noncytotoxic immunotherapy (n = 3). Diagnosis of CMV retinitis was delayed in all cases and patients received either no antiviral therapy (n = 2) or incorrect antiviral therapy (n = 3) for presumed herpes simplex/varicella zoster-related acute retinal necrosis. Retinitis subsequently regressed in all cases with introduction of systemic ganciclovir/valganciclovir (n = 5) and/or intravitreal foscarnet (n = 2). Four of five patients developed neovascularization because of extensive retinal ischemia. CONCLUSION: The clinical expression of CMV-associated retinopathy is strongly related to immune status. In patients with limited immune dysfunction, a mixed clinical picture of intraocular inflammation with panretinal occlusive vasculopathy, more characteristic of acute retinal necrosis, and peripheral slowly progressive granular retinitis, more characteristic of classic CMV retinitis, is observed. Recognition of this atypical clinical presentation, which the authors term chronic retinal necrosis, should prompt molecular testing for CMV to determine the appropriate antiviral therapy. Consideration should also be given to prophylactic panretinal photocoagulation in such eyes, given the high risk of neovascular complications.
Miller JW, Le Couter J, Strauss EC, Ferrara N. Vascular endothelial growth factor a in intraocular vascular disease. Ophthalmology 2013;120(1):106-14.Abstract
UNLABELLED: The vascular beds supplying the retina may sustain injury as a result of underlying disease such as diabetes, and/or the interaction of genetic predisposition, environmental insults, and age. The vascular pathologic features observed in different intraocular vascular diseases can be categorized broadly as proliferation, exemplified by proliferative diabetic retinopathy, leakage such as macular edema secondary to retinal vein occlusion, or a combination of proliferation and leakage, as seen in neovascular age-related macular degeneration (AMD). The World Health Organization has identified diabetic retinopathy and AMD as priority eye diseases for the prevention of vision loss in developed countries. The pathologic transformations of the retinal vasculature seen in intraocular vascular disease are associated with increased expression of vascular endothelial growth factor A (VEGF), a potent endothelial-specific mitogen. Furthermore, in model systems, VEGF alone is sufficient to trigger intraocular neovascularization, and its inhibition is associated with functional and anatomic improvements in the affected eye. Therapeutic interventions with effect on VEGF include intraocular capture and neutralization by engineered antibodies or chimeric receptors, downregulation of its expression with steroids, or alleviation of retinal ischemia, a major stimulus for VEGF expression, with retinal ablation by laser treatment. Data from prospective randomized clinical trials indicate that VEGF inhibition is a potent therapeutic strategy for intraocular vascular disease. These findings are changing clinical practice and are stimuli for further study of the basic mechanisms controlling intraocular angiogenesis. FINANCIAL DISCLOSURE(S): Proprietary or commercial disclosure may be found after the references.
Patel M, Vavvas DG. Fundus autofluorescence in ampiginous choroiditis. Ophthalmic Surg Lasers Imaging Retina 2013;44(4):393-7.Abstract
Fundus autofluorescence (FAF) is being increasingly employed in the evaluation of retinal diseases. We report the first description of FAF findings during the natural history of ampiginous choroiditis and correlate these findings to fundus photography, infrared imaging, and cross-sectional optical coherence tomography. In a patient with a 12-month recurring, relapsing course of ampiginous choroiditis, there was a predictable pattern of FAF findings. At the time of presentation with a whitish-yellow, creamy clinical lesion, FAF reveals a diffuse, subtle hyperautofluorescence at the site of activity. As the clinical lesion fades, the FAF takes on a more intense, discrete, coalesced hyperautofluorescence, which decreases and becomes stippled over time, eventually giving way to a patch of hypoautofluorescence at the site of inactivity. Examination over the patient's long course suggests that FAF evolves predictably during exacerbations and remissions, and the FAF findings reveal activity well after the clinical lesion resolves. FAF is a simple, noninvasive, and effective modality for following the evolution of ampiginous choroiditis.
Raghuram A, Hansen RM, Moskowitz A, Fulton AB. Photoreceptor and postreceptor responses in congenital stationary night blindness. Invest Ophthalmol Vis Sci 2013;54(7):4648-58.Abstract
PURPOSE: To investigate photoreceptor and postreceptor retinal function in patients with congenital stationary night blindness (CSNB). METHODS: Forty-one patients with CSNB (ages 0.19-32 years) were studied. ERG responses to a series of full-field stimuli were obtained under scotopic and photopic conditions and were used to categorize the CSNB patients as complete (cCSNB) or incomplete (iCSNB). Rod and cone photoreceptor (R(ROD), S(ROD), R(CONE), S(CONE)) and rod-driven postreceptor (V(MAX), log σ) response parameters were calculated from the a- and b-waves. Cone-driven responses to 30 Hz flicker and ON and OFF responses to a long duration (150 ms) flash were also obtained. Dark-adapted thresholds were measured. Analysis of variance was used to compare data from patients with cCSNB, patients with iCSNB, and controls. RESULTS: We found significant reduction in saturated photoreceptor amplitude (R(ROD), R(CONE)) but normal photoreceptor sensitivity (S(ROD), S(CONE)) in both CSNB groups. Rod-driven postreceptor response amplitude (V(MAX)) and sensitivity (log σ) were significantly reduced in CSNB. Log σ was significantly worse in cCSNB than in iCSNB; this was the only scotopic parameter that differed between the two CSNB groups. Photopic b-wave amplitude increased monotonically with stimulus strength in CSNB patients rather than showing a normal photopic hill. The amplitude of the 30-Hz flicker response was reduced compared with controls, more so in iCSNB than in cCSNB. The mean dark-adapted threshold was significantly elevated in CSNB, more so in cCSNB than in iCSNB. CONCLUSIONS: These results are evidence of normal photoreceptor function (despite the low saturated photoresponse amplitude) and anomalous postreceptor retinal circuitry.
Panou N, Kim IK, Sobrin L. Choroiditis and choroidal neovascularization in acute disseminated encephalomyelitis. Retin Cases Brief Rep 2013;7(1):89-90.Abstract
PURPOSE: To present a case with bilateral choroidal neovascularization (CNV) secondary to acute disseminated encephalomyelitis-associated choroiditis requiring immunomodulatory therapy for prevention of recurrence. METHODS: The clinical course of a patient diagnosed with acute disseminated encephalomyelitis, who developed bilateral choroiditis at the time of his neurologic diagnosis and bilateral CNV 6 years later, is reviewed. PATIENT: A 57-year-old man developed CNV in both eyes, 6 years after the initial diagnosis of acute disseminated encephalomyelitis-associated choroiditis. The patient was initially treated successfully with intravitreal bevacizumab injections and oral prednisone, but CNV recurred with steroid tapering. Mycophenolate mofetil was initiated as steroid-sparing immunomodulatory therapy. RESULTS: There was no CNV recurrence for 1.5 years without the need for additional antiangiogenic therapy. CONCLUSION: To our best knowledge, this is the first report of choroiditis and secondary CNV associated with acute disseminated encephalomyelitis. In cases of recurrent CNV associated with choroiditis, systemic therapy should be strongly considered in conjunction with antiangiogenic therapy. The recurrence of CNV with tapering of oral steroids and the remission of CNV with steroid-sparing immunomodulatory therapy support the role of ongoing inflammation in the pathogenesis.

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