Retina

Retina Publications

Sena DF, Kilian R, Liu S-H, Rizzo S, Virgili G. Pneumatic retinopexy versus scleral buckle for repairing simple rhegmatogenous retinal detachments. Cochrane Database Syst Rev 2021;11:CD008350.Abstract
BACKGROUND: A rhegmatogenous retinal detachment (RRD) is a separation of the neurosensory retina from the retinal pigment epithelium caused by a full-thickness break associated with vitreous traction. While pneumatic retinopexy (PR), scleral buckle (SB), and vitrectomy are all well-received surgical interventions for eyes with RRD, their relative effectiveness has remained controversial. OBJECTIVES: To assess the effectiveness and safety of PR versus SB or PR versus a combination treatment of SB and vitrectomy for people with RRD and to summarize any data on economic measures and quality of life. SEARCH METHODS: We searched CENTRAL; which contains the Cochrane Eyes and Vision Trials Register; 2021, Issue 3); Ovid MEDLINE; Ovid Embase; and four other databases on 11 March 2021. We used no date or language restrictions in the electronic searches for trials. SELECTION CRITERIA: We included all randomized or quasi-randomized controlled trials comparing the effectiveness of PR versus SB (with or without vitrectomy) for eyes with RRD. DATA COLLECTION AND ANALYSIS: After screening for eligibility, two review authors independently extracted study characteristics, methods, and outcomes. We followed systematic review standards as set by Cochrane. MAIN RESULTS: In this update, we identified and included one new randomized controlled trial. Together with two trials from the 2015 version of the review, we included three trials (276 eyes of 274 participants) comparing the effectiveness of PR versus SB. None compared PR versus a combined treatment of SB and vitrectomy.  Of the three trials, one was a small study (published in 1996) with 20 participants (20 eyes) enrolled in Ireland and followed for a mean of 16 months; the second (published in 1989) included 196 participants (198 eyes) in the US followed for at least six months, and the third (published in 2021) was conducted in Italy and enrolled 58 participants (58 eyes) with a follow-up of 12 months. Overall, poor reporting quality resulted in unclear or high risks of bias.  We found low-certainty evidence that PR may achieve retinal reattachment slightly less often than SB (risk ratio [RR] 0.91, 95% confidence interval [CI] 0.81 to 1.02; I2 = 0%; 3 studies, 276 eyes). Eyes undergoing PR may also display a higher risk of recurrent retinal detachment (low-certainty evidence), but the RR estimates were very imprecise (RR 1.70, 95% CI 0.97 to 2.98; I2 = 0%; 3 studies, 276 eyes). All three studies described the final visual acuity (VA) after the two procedures. However, the results were reported using different metrics and could not be combined. One study (196 participants) reported the proportion of eyes with a final VA of 20/40 or greater and favored PR (RR 1.31, 95% CI 1.04 to 1.65; low-certainty evidence), whereas in the 2021 study, both groups showed an improvement in final VA and there was no evidence of a difference between the two (mean difference [MD] -0.03, 95% CI -0.25 to 0.19; low-certainty evidence). No study reported data on quality of life or economic measures. Postoperative safety outcomes generally favored PR versus SB (low/very low-certainty evidence); however, there was considerable uncertainty regarding the risk of any operative ocular adverse events (RR 0.55 CI 0.28 to 1.11; 276 eyes), glaucoma (RR 0.31, 95% CI 0.01 to 7.46; 198 eyes), macular pucker (RR 0.65, 95% CI 0.20 to 2.11; 256 eyes), proliferative vitreoretinopathy (RR 0.94, 95% CI 0.30 to 2.96; 276 eyes), and persistent diplopia (RR 0.24, 95% CI 0.03 to 2.09; 256 eyes). Eyes undergoing PR experienced fewer postoperative cataract developments (RR 0.40, 95% CI 0.21 to 0.75; 153 eyes), choroidal detachments (RR 0.17, 95% CI 0.05 to 0.57; 198 eyes), and myopic shift (RR 0.03, 95% CI 0.01 to 0.10; 256 eyes). AUTHORS' CONCLUSIONS: The current update confirms the findings of the previous review. PR may result in lower rates of reattachment and higher rates of recurrence than SB, but carries a lower burden of postoperative complications. The effects of these two procedures on other functional outcomes and quality of life remain uncertain. The available evidence remains insufficient and of low quality.
Zekavat SM, Raghu VK, Trinder M, Ye Y, Koyama S, Honigberg MC, Yu Z, Pampana A, Urbut S, Haidermota S, O'Regan DP, Zhao H, Ellinor PT, Segrè AV, Elze T, Wiggs JL, Martone J, Adelman RA, Zebardast N, Del Priore L, Wang JC, Natarajan P. Deep Learning of the Retina Enables Phenome- and Genome-wide Analyses of the Microvasculature. Circulation 2021;Abstract
Background: The microvasculature, the smallest blood vessels in the body, has key roles in maintenance of organ health as well as tumorigenesis. The retinal fundus is a window for human in vivo non-invasive assessment of the microvasculature. Large-scale complementary machine learning-based assessment of the retinal vasculature with phenome-wide and genome-wide analyses may yield new insights into human health and disease. Methods: We utilized 97,895 retinal fundus images from 54,813 UK Biobank participants. Using convolutional neural networks to segment the retinal microvasculature, we calculated fractal dimension (FD) as a measure of vascular branching complexity, and vascular density. We associated these indices with 1,866 incident ICD-based conditions (median 10y follow-up) and 88 quantitative traits, adjusting for age, sex, smoking status, and ethnicity. Results: Low retinal vascular FD and density were significantly associated with higher risks for incident mortality, hypertension, congestive heart failure, renal failure, type 2 diabetes, sleep apnea, anemia, and multiple ocular conditions, as well as corresponding quantitative traits. Genome-wide association of vascular FD and density identified 7 and 13 novel loci respectively, which were enriched for pathways linked to angiogenesis (e.g., VEGF, PDGFR, angiopoietin, and WNT signaling pathways) and inflammation (e.g., interleukin, cytokine signaling). Conclusions: Our results indicate that the retinal vasculature may serve as a biomarker for future cardiometabolic and ocular disease and provide insights on genes and biological pathways influencing microvascular indices. Moreover, such a framework highlights how deep learning of images can quantify an interpretable phenotype for integration with electronic health records, biomarker, and genetic data to inform risk prediction and risk modification.
Cai LZ, Lin J, Starr MR, Obeid A, Ryan EH, Ryan C, Forbes NJ, Arias D, Ammar MJ, Patel LG, Capone A, Emerson GG, Joseph DP, Eliott D, Gupta OP, Regillo CD, Hsu J, Yonekawa Y, Yonekawa Y. PRO score: predictive scoring system for visual outcomes after rhegmatogenous retinal detachment repair. Br J Ophthalmol 2021;Abstract
BACKGROUND/AIMS: To compare risk factors for poor visual outcomes in patients undergoing primary rhegmatogenous retinal detachment (RRD) repair and to develop a scoring system. METHODS: Analysis of the Primary Retinal detachment Outcomes (PRO) study, a multicentre interventional cohort of consecutive primary RRD surgeries performed in 2015. The main outcome measure was a poor visual outcome (Snellen VA ≤20/200). RESULTS: A total of 1178 cases were included. The mean preoperative and postoperative logMARs were 1.1±1.1 (20/250) and 0.5±0.7 (20/63), respectively. Multivariable logistic regression identified preoperative risk factors predictive of poor visual outcomes (≤20/200), including proliferative vitreoretinopathy (PVR) (OR 1.26; 95% CI 1.13 to 1.40), history of antivascular endothelial growth factor (VEGF) injections (1.38; 1.11 to 1.71), >1-week vision loss (1.17; 1.08 to 1.27), ocular comorbidities (1.18; 1.00 to 1.38), poor presenting VA (1.06 per initial logMAR unit; 1.02 to 1.10) and age >70 (1.13; 1.04 to 1.23). The data were split into training (75%) and validation (25%) and a scoring system was developed and validated. The risk for poor visual outcomes was 8% with a total score of 0, 17% with 1, 29% with 2, 47% with 3, and 71% with 4 or higher. CONCLUSIONS: Independent risk factors were compared for poor visual outcomes after RRD surgery, which included PVR, anti-VEGF injections, vision loss >1 week, ocular comorbidities, presenting VA and older age. The PRO score was developed to provide a scoring system that may be useful in clinical practice.
Yemanyi F, Bora K, Blomfield AK, Wang Z, Chen J. Wnt Signaling in Inner Blood-Retinal Barrier Maintenance. Int J Mol Sci 2021;22(21)Abstract
The retina is a light-sensing ocular tissue that sends information to the brain to enable vision. The blood-retinal barrier (BRB) contributes to maintaining homeostasis in the retinal microenvironment by selectively regulating flux of molecules between systemic circulation and the retina. Maintaining such physiological balance is fundamental to visual function by facilitating the delivery of nutrients and oxygen and for protection from blood-borne toxins. The inner BRB (iBRB), composed mostly of inner retinal vasculature, controls substance exchange mainly via transportation processes between (paracellular) and through (transcellular) the retinal microvascular endothelium. Disruption of iBRB, characterized by retinal edema, is observed in many eye diseases and disturbs the physiological quiescence in the retina's extracellular space, resulting in vision loss. Consequently, understanding the mechanisms of iBRB formation, maintenance, and breakdown is pivotal to discovering potential targets to restore function to compromised physiological barriers. These unraveled targets can also inform potential drug delivery strategies across the BRB and the blood-brain barrier into retinas and brain tissues, respectively. This review summarizes mechanistic insights into the development and maintenance of iBRB in health and disease, with a specific focus on the Wnt signaling pathway and its regulatory role in both paracellular and transcellular transport across the retinal vascular endothelium.
Tomita Y, Qiu C, Bull E, Allen W, Kotoda Y, Talukdar S, Smith LEH, Fu Z. Müller glial responses compensate for degenerating photoreceptors in retinitis pigmentosa. Exp Mol Med 2021;Abstract
Photoreceptor degeneration caused by genetic defects leads to retinitis pigmentosa, a rare disease typically diagnosed in adolescents and young adults. In most cases, rod loss occurs first, followed by cone loss as well as altered function in cells connected to photoreceptors directly or indirectly. There remains a gap in our understanding of retinal cellular responses to photoreceptor abnormalities. Here, we utilized single-cell transcriptomics to investigate cellular responses in each major retinal cell type in retinitis pigmentosa model (P23H) mice vs. wild-type littermate mice. We found a significant decrease in the expression of genes associated with phototransduction, the inner/outer segment, photoreceptor cell cilium, and photoreceptor development in both rod and cone clusters, in line with the structural changes seen with immunohistochemistry. Accompanying this loss was a significant decrease in the expression of genes involved in metabolic pathways and energy production in both rods and cones. We found that in the Müller glia/astrocyte cluster, there was a significant increase in gene expression in pathways involving photoreceptor maintenance, while concomitant decreases were observed in rods and cones. Additionally, the expression of genes involved in mitochondrial localization and transport was increased in the Müller glia/astrocyte cluster. The Müller glial compensatory increase in the expression of genes downregulated in photoreceptors suggests that Müller glia adapt their transcriptome to support photoreceptors and could be thought of as general therapeutic targets to protect against retinal degeneration.
Hellström A, Pivodic A, Gränse L, Lundgren P, Sjöbom U, Nilsson AK, Söderling H, Hård A-L, Smith LEH, Löfqvist CA. Association of Docosahexaenoic Acid and Arachidonic Acid Serum Levels With Retinopathy of Prematurity in Preterm Infants. JAMA Netw Open 2021;4(10):e2128771.Abstract
Importance: Supplementing preterm infants with long-chain polyunsaturated fatty acids (LC-PUFA) has been inconsistent in reducing the severity and incidence of retinopathy of prematurity (ROP). Furthermore, few studies have measured the long-term serum lipid levels after supplementation. Objective: To assess whether ROP severity is associated with serum levels of LC-PUFA, especially docosahexaenoic acid (DHA) and arachidonic acid (AA), during the first 28 postnatal days. Design, Setting, and Participants: This cohort study analyzed the Mega Donna Mega study, a randomized clinical trial that provided enteral fatty acid supplementation at 3 neonatal intensive care units in Sweden. Infants included in this cohort study were born at a gestational age of less than 28 weeks between December 20, 2016, and August 6, 2019. Main Outcomes and Measures: Severity of ROP was classified as no ROP, mild or moderate ROP (stage 1-2), or severe ROP (stage 3 and type 1). Serum phospholipid fatty acids were measured through gas chromatography-mass spectrometry. Ordinal logistic regression, with a description of unadjusted odds ratio (OR) as well as gestational age- and birth weight-adjusted ORs and 95% CIs, was used. Areas under the curve were used to calculate mean daily levels of fatty acids during postnatal days 1 to 28. Blood samples were obtained at the postnatal ages of 1, 3, 7, 14, and 28 days. Results: A total of 175 infants were included in analysis. Of these infants, 99 were boys (56.6%); the median (IQR) gestational age was 25 weeks 5 days (24 weeks 3 days to 26 weeks 6 days), and the median (IQR) birth weight was 785 (650-945) grams. A higher DHA proportion was seen in infants with no ROP compared with those with mild or moderate ROP or severe ROP (OR per 0.5-molar percentage increase, 0.49 [95% CI, 0.36-0.68]; gestational age- and birth weight-adjusted OR, 0.66 [95% CI, 0.46-0.93]). The corresponding adjusted OR for AA levels per 1-molar percentage increase was 0.83 (95% CI, 0.66-1.05). The association between DHA levels and ROP severity appeared only in infants with sufficient AA levels, suggesting that a mean daily minimum level of 7.8 to 8.3 molar percentage of AA was necessary for a detectable association between DHA level and less severe ROP. Conclusions and Relevance: This cohort study found that higher mean daily serum levels of DHA during the first 28 postnatal days were associated with less severe ROP even after adjustment for known risk factors, but only in infants with sufficiently high AA levels. Further studies are needed to identify LC-PUFA supplementation strategies that may prevent ROP and other morbidities.
Comin CH, Tsirukis DI, Sun Y, Xu X. Quantification of retinal blood leakage in fundus fluorescein angiography in a retinal angiogenesis model. Sci Rep 2021;11(1):19903.Abstract
Blood leakage from the vessels in the eye is the hallmark of many vascular eye diseases. One of the preclinical mouse models of retinal blood leakage, the very-low-density-lipoprotein receptor deficient mouse (Vldlr-/-), is used for drug screening and mechanistic studies. Vessel leakage is usually examined using Fundus fluorescein angiography (FFA). However, interpreting FFA images of the Vldlr-/- model is challenging as no automated and objective techniques exist for this model. A pipeline has been developed for quantifying leakage intensity and area including three tasks: (i) blood leakage identification, (ii) blood vessel segmentation, and (iii) image registration. Morphological operations followed by log-Gabor quadrature filters were used to identify leakage regions. In addition, a novel optic disk detection algorithm based on graph analysis was developed for registering the images at different timepoints. Blood leakage intensity and area measured by the methodology were compared to ground truth quantifications produced by two annotators. The relative difference between the quantifications from the method and those obtained from ground truth images was around 10% ± 6% for leakage intensity and 17% ± 8% for leakage region. The Pearson correlation coefficient between the method results and the ground truth was around 0.98 for leakage intensity and 0.94 for leakage region. Therefore, we presented a computational method for quantifying retinal vascular leakage and vessels using FFA in a preclinical angiogenesis model, the Vldlr-/- model.
Uemura A, Fruttiger M, D'Amore PA, De Falco S, Joussen AM, Sennlaub F, Brunck LR, Johnson KT, Lambrou GN, Rittenhouse KD, Langmann T. VEGFR1 signaling in retinal angiogenesis and microinflammation. Prog Retin Eye Res 2021;84:100954.Abstract
Five vascular endothelial growth factor receptor (VEGFR) ligands (VEGF-A, -B, -C, -D, and placental growth factor [PlGF]) constitute the VEGF family. VEGF-A binds VEGF receptors 1 and 2 (VEGFR1/2), whereas VEGF-B and PlGF only bind VEGFR1. Although much research has been conducted on VEGFR2 to elucidate its key role in retinal diseases, recent efforts have shown the importance and involvement of VEGFR1 and its family of ligands in angiogenesis, vascular permeability, and microinflammatory cascades within the retina. Expression of VEGFR1 depends on the microenvironment, is differentially regulated under hypoxic and inflammatory conditions, and it has been detected in retinal and choroidal endothelial cells, pericytes, retinal and choroidal mononuclear phagocytes (including microglia), Müller cells, photoreceptor cells, and the retinal pigment epithelium. Whilst the VEGF-A decoy function of VEGFR1 is well established, consequences of its direct signaling are less clear. VEGFR1 activation can affect vascular permeability and induce macrophage and microglia production of proinflammatory and proangiogenic mediators. However the ability of the VEGFR1 ligands (VEGF-A, PlGF, and VEGF-B) to compete against each other for receptor binding and to heterodimerize complicates our understanding of the relative contribution of VEGFR1 signaling alone toward the pathologic processes seen in diabetic retinopathy, retinal vascular occlusions, retinopathy of prematurity, and age-related macular degeneration. Clinically, anti-VEGF drugs have proven transformational in these pathologies and their impact on modulation of VEGFR1 signaling is still an opportunity-rich field for further research.
Laíns I, Wang JC, Cui Y, Katz R, Vingopoulos F, Staurenghi G, Vavvas DG, Miller JW, Miller JB. Retinal applications of swept source optical coherence tomography (OCT) and optical coherence tomography angiography (OCTA). Prog Retin Eye Res 2021;84:100951.Abstract
The advent of optical coherence tomography (OCT) revolutionized both clinical assessment and research of vitreoretinal conditions. Since then, extraordinary advances have been made in this imaging technology, including the relatively recent development of swept-source OCT (SS-OCT). SS-OCT enables a fast scan rate and utilizes a tunable swept laser, thus enabling the incorporation of longer wavelengths than conventional spectral-domain devices. These features enable imaging of larger areas with reduced motion artifact, and a better visualization of the choroidal vasculature, respectively. Building on the principles of OCT, swept-source OCT has also been applied to OCT angiography (SS-OCTA), thus enabling a non-invasive in depth-resolved imaging of the retinal and choroidal microvasculature. Despite their advantages, the widespread use of SS-OCT and SS-OCTA remains relatively limited. In this review, we summarize the technical details, advantages and limitations of SS-OCT and SS-OCTA, with a particular emphasis on their relevance for the study of retinal conditions. Additionally, we comprehensively review relevant studies performed to date to the study of retinal health and disease, and highlight current gaps in knowledge and opportunities to take advantage of swept source technology to improve our current understanding of many medical and surgical chorioretinal conditions. We anticipate that SS-OCT and SS-OCTA will continue to evolve rapidly, contributing to a paradigm shift to more widespread adoption of new imaging technology to clinical practice.
Townes-Anderson E, Halasz E, Wang W, Zarbin M. Coming of Age for the Photoreceptor Synapse. Invest Ophthalmol Vis Sci 2021;62(12):24.Abstract
Purpose: To discuss the potential contribution of rod and cone synapses to the loss of visual function in retinal injury and disease. Methods: The published literature and the authors' own work were reviewed. Results: Retinal detachment is used as a case study of rod spherule and cone pedicle plasticity after injury. Both rod and cone photoreceptors terminals are damaged after detachment although the structural changes observed are only partially overlapping. For second-order neurons, only those associated with rod spherules respond consistently to injury by remodeling. Examination of signaling pathways involved in plasticity of conventional synapses and in neural development has been and may continue to be productive in discovering novel therapeutic targets. Rho kinase (ROCK) inhibition is an example of therapy that may reduce synaptic damage by preserving normal synaptic structure of rod and cone cells. Conclusions: We hypothesize that synaptic damage contributes to poor visual restoration after otherwise successful anatomical repair of retinal detachment. A similar situation may exist for patients with degenerative retinal disease. Thus, synaptic structure and function should be routinely studied, as this information may disclose therapeutic strategies to mitigate visual loss.
Patel NA, Yannuzzi NA, Lin J, Smiddy WE. A Cost Effectiveness Analysis of Intravitreal Aflibercept for the Prevention of Progressive Diabetic Retinopathy. Ophthalmol Retina 2021;Abstract
PURPOSE: To calculate costs required to prevent center-involved diabetic macular edema (CI-DME) or proliferative diabetic retinopathy (PDR), and to improve the diabetic retinopathy severity score (DRSS) with intravitreal anti-VEGF injections as reported for aflibercept in two randomized control trials. DESIGN: Cost-effectiveness analysis modeling based on published data SUBJECTS: None METHODS: Results from PANORAMA and the Diabetic Retinopathy Clinical Research Network (DRCR.net) Protocol W were analyzed. Parameters collected included DRSS score, risk reduction of PDR, risk reduction of CI-DME, and number of treatments required. Costs were modeled based on 2020 Medicare reimbursement data practice settings of hospital-based facility and non-facility. MAIN OUTCOME MEASURE: Cost to prevent case of PDR and CI-DME, and to improve DRSS stage RESULTS: Over 2 years in Protocol W, the cost required to prevent 1 case of PDR was $83,000 ($72,400) in the facility (non-facility) setting; in PANORAMA, the corresponding 2 year costs were $89,400 ($75,000) for the 2Q16 arm, and $91,200 ($89,900) for the 2Q8PRN arm. To prevent 1 case of CI-DME with vision loss in Protocol W, the cost was $154,000 ($133,000). For all CI-DME, with and without vision loss; in PANORAMA, the costs to prevent a case were $70,900 ($59,500) for the 2Q16 arm, and $90,000 ($88,800) for the 2Q8PRN arm. In Protocol W, the overall accumulated total for cost /DRSS unit change at the 2 year point for facility (non-facility) setting was $2700 ($2400)/DRSS. In the first year alone, it was $2100 ($1800)/DRSS and in the second year alone, $6100 ($5300)/DRSS. CONCLUSION: There is a considerable cost associated with the prevention of PDR and CI-DME with intravitreal aflibercept injections. A price per unit of change in diabetic retinopathy severity score is a new parameter which might serve as a benchmark in future utility analyses that could be used to bring perspective to cost-utility considerations.
Bannai D, Adhan I, Katz R, Kim LA, Keshavan M, Miller JB, Lizano P. Quantifying Retinal Microvascular Morphology in Schizophrenia Using Swept-Source Optical Coherence Tomography Angiography. Schizophr Bull 2021;Abstract
BACKGROUND: Retinovascular changes are reported on fundus imaging in schizophrenia (SZ). This is the first study to use swept-source optical coherence tomography angiography (OCT-A) to comprehensively examine retinal microvascular changes in SZ. METHODS: This study included 30 patients with SZ/schizoaffective disorder (8 early and 15 chronic) and 22 healthy controls (HCs). All assessments were performed at Beth Israel Deaconess Medical Center and Massachusetts Eye and Ear. All participants underwent swept-source OCT-A of right (oculus dextrus [OD]) and left (oculus sinister [OS]) eye, clinical, and cognitive assessments. Macular OCT-A images (6 × 6 mm) were collected with the DRI Topcon Triton for superficial, deep, and choriocapillaris vascular regions. Microvasculature was quantified using vessel density (VD), skeletonized vessel density (SVD), fractal dimension (FD), and vessel diameter index (VDI). RESULTS: Twenty-one HCs and 26 SZ subjects were included. Compared to HCs, SZ patients demonstrated higher overall OD superficial SVD, OD choriocapillaris VD, and OD choriocapillaris SVD, which were primarily observed in the central, central and outer superior, and central and outer inferior/superior, respectively. Early-course SZ subjects had significantly higher OD superficial VD, OD choriocapillaris SVD, and OD choriocapillaris FD compared to matched HCs. Higher bilateral (OU) superficial VD correlated with lower Positive and Negative Syndrome Scale (PANSS) positive scores, and higher OU deep VDI was associated with higher PANSS negative scores. CONCLUSIONS AND RELEVANCE: These results suggest the presence of microvascular dysfunction associated with early-stage SZ. Clinical associations with microvascular alterations further implicate this hypothesis, with higher measures being associated with worse symptom severity and functioning in early stages and with lower symptom severity and better functioning in later stages.
Maidana DE, Gonzalez-Buendia L, Miller JW, Vavvas DG. Local photoreceptor cell death differences in the murine model of retinal detachment. Sci Rep 2021;11(1):18798.Abstract
To investigate local cell death differences in the attached and detached retina at different regions in a murine experimental retinal detachment model. Subretinal injection of sodium hyaluronate was performed in eight-week-old C57BL/6J mice. Retinal regions of interest were defined in relation to their distance from the peak of the retinal detachment, as follows: (1) attached central; (2) attached paracentral; (3) detached apex; and (4) detached base. At day 0, the outer nuclear layer cell count for the attached central, attached paracentral, detached apex, and detached base was 1247.60 ± 64.62, 1157.80 ± 163.33, 1264.00 ± 150.7, and 1013.80 ± 67.16 cells, respectively. There were significant differences between the detached base vs. attached central, and between detached base vs. detached apex at day 0. The detached apex region displayed a significant and progressive cell count reduction from day 0 to 14. In contrast, the detached base region did not show progressive retinal degeneration in this model. Moreover, only the detached apex region had a significant and progressive cell death rate compared to baseline. Immediate confounding changes with dramatic differences in cell death rates are present across regions of the detached retina. We speculate that mechanical and regional differences in the bullous detached retina can modify the rate of cell death in this model.
Musayeva A, Unkrig JC, Zhutdieva MB, Manicam C, Ruan Y, Laspas P, Chronopoulos P, Göbel ML, Pfeiffer N, Brochhausen C, Daiber A, Oelze M, Li H, Xia N, Gericke A. Betulinic Acid Protects from Ischemia-Reperfusion Injury in the Mouse Retina. Cells 2021;10(9)Abstract
Ischemia/reperfusion (I/R) events are involved in the pathophysiology of numerous ocular diseases. The purpose of this study was to test the hypothesis that betulinic acid protects from I/R injury in the mouse retina. Ocular ischemia was induced in mice by increasing intraocular pressure (IOP) to 110 mm Hg for 45 min, while the fellow eye served as a control. One group of mice received betulinic acid (50 mg/kg/day p.o. once daily) and the other group received the vehicle solution only. Eight days after the I/R event, the animals were killed and the retinal wholemounts and optic nerve cross-sections were prepared and stained with cresyl blue or toluidine blue, respectively, to count cells in the ganglion cell layer (GCL) of the retina and axons in the optic nerve. Retinal arteriole responses were measured in isolated retinas by video microscopy. The levels of reactive oxygen species (ROS) were assessed in retinal cryosections and redox gene expression was determined in isolated retinas by quantitative PCR. I/R markedly reduced cell number in the GCL and axon number in the optic nerve of the vehicle-treated mice. In contrast, only a negligible reduction in cell and axon number was observed following I/R in the betulinic acid-treated mice. Endothelial function was markedly reduced and ROS levels were increased in retinal arterioles of vehicle-exposed eyes following I/R, whereas betulinic acid partially prevented vascular endothelial dysfunction and ROS formation. Moreover, betulinic acid boosted mRNA expression for the antioxidant enzymes SOD3 and HO-1 following I/R. Our data provide evidence that betulinic acid protects from I/R injury in the mouse retina. Improvement of vascular endothelial function and the reduction in ROS levels appear to contribute to the neuroprotective effect.
Peterson SL, Li Y, Sun CJ, Wong KA, Leung KS, de Lima S, Hanovice NJ, Yuki K, Stevens B, Benowitz LI. Retinal Ganglion Cell Axon Regeneration Requires Complement and Myeloid Cell Activity within the Optic Nerve. J Neurosci 2021;41(41):8508-8531.Abstract
Axon regenerative failure in the mature CNS contributes to functional deficits following many traumatic injuries, ischemic injuries, and neurodegenerative diseases. The complement cascade of the innate immune system responds to pathogen threat through inflammatory cell activation, pathogen opsonization, and pathogen lysis, and complement is also involved in CNS development, neuroplasticity, injury, and disease. Here, we investigated the involvement of the classical complement cascade and microglia/monocytes in CNS repair using the mouse optic nerve injury (ONI) model, in which axons arising from retinal ganglion cells (RGCs) are disrupted. We report that central complement C3 protein and mRNA, classical complement C1q protein and mRNA, and microglia/monocyte phagocytic complement receptor CR3 all increase in response to ONI, especially within the optic nerve itself. Importantly, genetic deletion of C1q, C3, or CR3 attenuates RGC axon regeneration induced by several distinct methods, with minimal effects on RGC survival. Local injections of C1q function-blocking antibody revealed that complement acts primarily within the optic nerve, not retina, to support regeneration. Moreover, C1q opsonizes and CR3+ microglia/monocytes phagocytose growth-inhibitory myelin debris after ONI, a likely mechanism through which complement and myeloid cells support axon regeneration. Collectively, these results indicate that local optic nerve complement-myeloid phagocytic signaling is required for CNS axon regrowth, emphasizing the axonal compartment and highlighting a beneficial neuroimmune role for complement and microglia/monocytes in CNS repair.SIGNIFICANCE STATEMENT Despite the importance of achieving axon regeneration after CNS injury and the inevitability of inflammation after such injury, the contributions of complement and microglia to CNS axon regeneration are largely unknown. Whereas inflammation is commonly thought to exacerbate the effects of CNS injury, we find that complement proteins C1q and C3 and microglia/monocyte phagocytic complement receptor CR3 are each required for retinal ganglion cell axon regeneration through the injured mouse optic nerve. Also, whereas studies of optic nerve regeneration generally focus on the retina, we show that the regeneration-relevant role of complement and microglia/monocytes likely involves myelin phagocytosis within the optic nerve. Thus, our results point to the importance of the innate immune response for CNS repair.

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