Hiroshi Enaida

Dynamic Increase in Extracellular ATP Accelerates Photoreceptor Cell Apoptosis via Ligation of P2RX7 in Subretinal Hemorrhage

Photoreceptor degeneration is the most critical cause of visual impairment in age-related macular degeneration (AMD). In neovascular form of AMD, severe photoreceptor loss develops with subretinal hemorrhage due to choroidal neovascularization (CNV), growth of abnormal blood vessels from choroidal circulation. However, the detailed mechanisms of this process remain elusive. Here we demonstrate that neovascular AMD with subretinal hemorrhage accompanies a significant increase in extracellular ATP, and that extracellular ATP initiates neurodegenerative processes through specific ligation of Purinergic receptor P2X, ligand-gated ion channel, 7 (P2RX7; P2X7 receptor). Increased extracellular ATP levels were found in the vitreous samples of AMD patients with subretinal hemorrhage compared to control vitreous samples. Extravascular blood induced a massive release of ATP and photoreceptor cell apoptosis in co-culture with primary retinal cells. Photoreceptor cell apoptosis accompanied mitochondrial apoptotic pathways, namely activation of caspase-9 and translocation of apoptosis-inducing factor (AIF) from mitochondria to nuclei, as well as TUNEL-detectable DNA fragmentation. These hallmarks of photoreceptor cell apoptosis were prevented by brilliant blue G (BBG), a selective P2RX7 antagonist, which is an approved adjuvant in ocular surgery. Finally, in a mouse model of subretinal hemorrhage, photoreceptor cells degenerated through BBG-inhibitable apoptosis, suggesting that ligation of P2RX7 by extracellular ATP may accelerate photoreceptor cell apoptosis in AMD with subretinal hemorrhage. Our results indicate a novel mechanism that could involve neuronal cell death not only in AMD but also in hemorrhagic disorders in the CNS and encourage the potential application of BBG as a neuroprotective therapy.

Astrocyte-Mediated Ischemic Tolerance

Preconditioning (PC) using a preceding sublethal ischemic insult is an attractive strategy for protecting neurons by inducing ischemic tolerance in the brain. Although the underlying molecular mechanisms have been extensively studied, almost all studies have focused on neurons. Here, using a middle cerebral artery occlusion model in mice, we show that astrocytes play an essential role in the induction of brain ischemic tolerance. PC caused activation of glial cells without producing any noticeable brain damage. The spatiotemporal pattern of astrocytic, but not microglial, activation correlated well with that of ischemic tolerance. Interestingly, such activation in astrocytes lasted at least 8 weeks. Importantly, inhibiting astrocytes with fluorocitrate abolished the induction of ischemic tolerance. To investigate the underlying mechanisms, we focused on the P2X7 receptor as a key molecule in astrocyte-mediated ischemic tolerance. P2X7 receptors were dramatically upregulated in activated astrocytes. PC-induced ischemic tolerance was abolished in P2X7 receptor knock-out mice. Moreover, our results suggest that hypoxia-inducible factor-1α, a well known mediator of ischemic tolerance, is involved in P2X7 receptor-mediated ischemic tolerance. Unlike previous reports focusing on neuron-based mechanisms, our results show that astrocytes play indispensable roles in inducing ischemic tolerance, and that upregulation of P2X7 receptors in astrocytes is essential.

Relationship between Aqueous Flare and Visual Function in Retinitis Pigmentosa

PURPOSEnTo investigate the correlation between aqueous flare values and central visual function in patients with retinitis pigmentosa (RP).nnnDESIGNnRetrospective, observational case series.nnnMETHODSnWe retrospectively studied 160 patients diagnosed with typical RP and 59 control subjects. Aqueous flare values were measured by laser flare cell meter. The relationships between aqueous flare and best-corrected visual acuity (VA) and mean deviation (MD) of static perimetry tests were analyzed in RP patients.nnnRESULTSnThe aqueous flare values were significantly higher in the RP patients compared to the control subjects (10.6 ± 7.9 vs 5.0 ± 2.1 photon counts per millisecond [pc/ms], P < .0001). In the RP patients, the aqueous flare values were negatively correlated with VA (rxa0= 0.359, P < .0001) and MD (rxa0=xa0-0.330, P < .0001). Age-subgroup analysis showed a significant correlation between aqueous flare and VA in the RP patients 40s, 50s, and 60s and between aqueous flare and MD in the 30s, 40s, 50s, and 60s. The RP patients with MD values ≥-15 decibels (dB) showed significantly higher levels of aqueous flare than those with MD values <-15 dB (12.0 ± 6.2 vs 8.7 ± 5.8, Pxa0= .0001).nnnCONCLUSIONSnAqueous flare is increased in RP patients and negatively correlates with central visual function. These results suggest a close relationship between inflammation and central vision loss in RP.

Correlation between macular blood flow and central visual sensitivity in retinitis pigmentosa

To investigate the changes in macular blood flow and the correlation between those changes and central visual function in patients with retinitis pigmentosa (RP).

Hyphema is a risk factor for failure of trabeculectomy in neovascular glaucoma: a retrospective analysis

BackgroundSeveral retinal ischemic diseases can cause neovascular glaucoma (NVG). Trabeculectomy with mitomycin C (MMC) is a relatively better treatment modality in the management of eyes with NVG than other glaucoma surgeries. The aim of this study was to investigate the factors that may influence the outcome of trabeculectomy with MMC for NVG.MethodsForty-nine NVG eyes from 43 patients (26 males and 17 females) underwent primary trabeculectomy with MMC. The mean follow-up period was 16.8u2009±u20098.1xa0months (range, 6 to 34xa0months). Twenty-one eyes of 21 patients received intravitreal bevacizumab (IVB) 3.6u2009±u20091.8xa0days before trabeculectomy with MMC. A Kaplan-Meier survival-curve analysis was used to summarize the cumulative probability of success. We examined the relationship between the surgical outcome and the following surgical factors: gender, age, history of panretinal photocoagulation, history of cataract surgery, history of vitrectomy, preoperative IVB, NVG in the fellow eye, and postoperative complications (hyphema, choroidal detachment, and formation of fibrin) by multivariate analysis.ResultsThe survival rate was 83.7% after 6xa0months, 70.9% after 12xa0months, and 60.8% after 24xa0months. The Kaplan-Meier survival curves showed no significant difference in the survival rate between the eyes with preoperative IVB (nu2009=u200921) and the eyes without preoperative IVB (nu2009=u200928) (pu2009=u20090.14). The multiple logistic regression analysis showed that postoperative hyphema (odds ratio, 6.54; 95% confidence interval, 1.41 to 35.97) was significantly associated with the surgical outcome (pu2009=u20090.02).ConclusionsPostoperative hyphema was significantly correlated with the outcome of trabeculectomy for NVG. There was no significant association between preoperative IVB and postoperative hyphema or the results of trabeculectomy.

Therapeutic efficacy of topical unoprostone isopropyl in retinitis pigmentosa

To evaluate the therapeutic effect of topical unoprostone isopropyl (unoprostone) on patients with retinitis pigmentosa (RP).

Ultrastructural Changes of the Vitreoretinal Interface During Long-Term Follow-up After Removal of the Internal Limiting Membrane

PURPOSEnTo investigate long-term ultrastructural changes in the retina after internal limiting membrane (ILM) peeling through the examination of morphologic changes 3 years after vitrectomy in cynomolgus monkeys.nnnDESIGNnLaboratory investigation.nnnMETHODSnPars plana vitrectomy was performed, followed by ILM peeling, in 2 primate eyes. Ultrastructural changes were investigated using light microscopy and transmission and scanning electron microscopy 3 years after ILM peeling.nnnRESULTSnThe remaining posterior vitreous and ILM-peeled areas were clearly recognized after the long-term follow-up. The exposed Müller cell processes were partially damaged, while regenerative spindle-shaped Müller cell processes developed, covering most of the retina. Notably, the nerve fiber layer was found to be uncovered and exposed to the vitreous space owing to misdirection of glial wound healing in some parts. In these areas, glial wound healing occurred beneath the nerve fiber layer. Although the glial cells covered the damaged areas, there was no apparent ILM regeneration in the shape of a continuous flat sheet, with the exception of accumulated deposits of basement membrane materials.nnnCONCLUSIONSnAlthough the retinal structures were well preserved after ILM peeling, ILM peeling resulted in mild damage to the vitreoretinal interface, which was not completely restored even after 3 years. The multilinear shape of the exposed nerve fiber may explain the previously reported dissociated optic nerve fiber layer appearance. The glial cells produced basement membrane materials around their processes, although they did not restore the ILM as a flat sheet.

Long-term surgical outcomes of epiretinal membrane in patients with retinitis pigmentosa

Macular complications such as an epiretinal membrane (ERM), a cystoid macular edema and a macular hole lead to unexpected central vision impairment especially for patients with retinitis pigmentosa (RP). To evaluate the long-term surgical outcomes of pars plana vitrectomy (PPV) for ERM in patients with RP, we retrospectively reviewed the charts of a consecutive series of 10 RP patients who underwent PPV for ERM at Kyushu University Hospital. Visual acuity (VA) testing, a fundus examination, and an optical coherence tomography (OCT) analysis were conducted. The standard PPV using three sclerotomies was performed for ERM. PPV was performed in 12 eyes of 10 patients. One eye was excluded from the outcome assessment due to short period observation (18 months). There was no significantly deleterious change from the baseline to final VA between the operation eyes and the fellow eyes (Pu2009=u20090.19). Moreover, morphological improvement was obtained in 9 of 11 eyes based on OCT. Our present data suggest that PPV may be tolerable in the management for ERM in RP patients over the long-term. Furthermore, the appearance of the ellipsoid zone was an important factor in the prediction of visual outcome and determination of surgical indication.

Long-term outcomes of 3 surgical adjuvants used for internal limiting membrane peeling in idiopathic macular hole surgery.

PurposeIndocyanine green (ICG), an adjuvant used for peeling of the internal limiting membrane (ILM) during vitreous surgery for idiopathic macular hole (MH), has been reported to be toxic, possibly affecting postoperative visual acuity. We compared the long-term outcomes (within 2xa0years) of brilliant blue G (BBG), ICG, and triamcinolone acetonide (TA).Patients and methodsThis study involved 97 eyes of 94 patients who underwent vitreous surgery for MH at the Yamagata University Hospital between June 2002 and November 2010. The surgical adjuvants used were BBG for 15 eyes, ICG for 61 eyes, and TA for 21 eyes. We compared the postoperative visual acuities, initial closure rates, final closure rates, and complications of the 3 groups.ResultsIn all 3 groups, the visual acuity significantly improved after surgery. The magnitude of the improvement at 2xa0years after surgery was significantly better in the BBG group than in the ICG group (Mann–Whitney test, Pxa0=xa00.020). The postoperative visual acuity did not significantly differ between the BBG and TA groups (Pxa0=xa00.627) or between the ICG and TA groups (Pxa0=0xa0.137). Thus, the surgery using BBG resulted in a significantly better outcome in visual acuity than did the surgery using ICG. The 3 groups did not differ in initial or final closure rates or in incidence of complications.ConclusionAnalysis of the long-term outcomes of vitreous surgeries provided evidence that BBG is a useful adjuvant for ILM peeling.

Improved brilliant blue G staining of the internal limiting membrane with sharp cut filters of a novel viewing filter system.

Purpose: We developed a new artificial image enhancement system aimed at intraoperative visibility improvement as a clinical prototype. We examined each optical characteristic and change in intraoperative visibility using brilliant blue G (BBG) staining with various sharp cut filters (SCFs). Method: This was a retrospective and observational study. The system was composed of several filters attached to the operating microscope. Six eyes from 6 patients who presented with macular hole and underwent surgery using this system were studied. As a clinical examination, the intraoperative visibility of BBG staining intensities was compared for 4 kinds of SCFs during vitrectomy. Quantitative evaluation was calculated using the International Commission on Illumination 1976 (L*, a*, b*) color space (CIELAB) method. Furthermore, we evaluated each optical characteristic of 4 types of SCFs using extracted porcine eyes and a spectroradiometer as a clinical simulation. Results: Suitable filter selection was possible for this system. The observed color tone and spectral irradiance changes with SCF insertion changed dynamically. In macular hole cases, the color intensities between BBG-stained and nonstained areas were improved using SCF-455 and SCF-520, which was statistically significant (p < 0.05) by CIELAB. Conclusion: The system improved BBG staining intensity with the use of selective SCFs.