2020

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Yan W, Peng Y-R, van Zyl T, Regev A, Shekhar K, Juric D, Sanes JR. Cell Atlas of The Human Fovea and Peripheral Retina. Sci Rep 2020;10(1):9802.Abstract
Most irreversible blindness results from retinal disease. To advance our understanding of the etiology of blinding diseases, we used single-cell RNA-sequencing (scRNA-seq) to analyze the transcriptomes of ~85,000 cells from the fovea and peripheral retina of seven adult human donors. Utilizing computational methods, we identified 58 cell types within 6 classes: photoreceptor, horizontal, bipolar, amacrine, retinal ganglion and non-neuronal cells. Nearly all types are shared between the two retinal regions, but there are notable differences in gene expression and proportions between foveal and peripheral cohorts of shared types. We then used the human retinal atlas to map expression of 636 genes implicated as causes of or risk factors for blinding diseases. Many are expressed in striking cell class-, type-, or region-specific patterns. Finally, we compared gene expression signatures of cell types between human and the cynomolgus macaque monkey, Macaca fascicularis. We show that over 90% of human types correspond transcriptomically to those previously identified in macaque, and that expression of disease-related genes is largely conserved between the two species. These results validate the use of the macaque for modeling blinding disease, and provide a foundation for investigating molecular mechanisms underlying visual processing.
Yanagida K, Engelbrecht E, Niaudet C, Jung B, Gaengel K, Holton K, Swendeman S, Liu CH, Levesque MV, Kuo A, Fu Z, Smith LEH, Betsholtz C, Hla T. Sphingosine 1-Phosphate Receptor Signaling Establishes AP-1 Gradients to Allow for Retinal Endothelial Cell Specialization. Dev Cell 2020;52(6):779-793.e7.Abstract
Transcriptional mechanisms that drive angiogenesis and organotypic vascular endothelial cell specialization are poorly understood. Here, we show that retinal endothelial sphingosine 1-phosphate receptors (S1PRs), which restrain vascular endothelial growth factor (VEGF)-induced angiogenesis, spatially restrict expression of JunB, a member of the activator protein 1 (AP-1) family of transcription factors (TFs). Mechanistically, VEGF induces JunB expression at the sprouting vascular front while S1PR-dependent vascular endothelial (VE)-cadherin assembly suppresses JunB expression in the nascent vascular network, thus creating a gradient of this TF. Endothelial-specific JunB knockout mice showed diminished expression of neurovascular guidance genes and attenuated retinal vascular network progression. In addition, endothelial S1PR signaling is required for normal expression of β-catenin-dependent genes such as TCF/LEF1 and ZIC3 TFs, transporters, and junctional proteins. These results show that S1PR signaling restricts JunB function to the expanding vascular front, thus creating an AP-1 gradient and enabling organotypic endothelial cell specialization of the vascular network.
Yang M, Bair JA, Hodges RR, Serhan CN, Dartt DA. Resolvin E1 Reduces Leukotriene B4-Induced Intracellular Calcium Increase and Mucin Secretion in Rat Conjunctival Goblet Cells. Am J Pathol 2020;190(9):1823-1832.Abstract
Leukotriene B4 (LTB4) is a major proinflammatory mediator important in host defense, whereas resolvins (Rvs) are produced during the resolution phase of inflammation. The authors determined the actions of both RvE1 and RvD1 on LTB4-induced responses of goblet cells cultured from rat conjunctiva. The responses measured were an increase in the intracellular [Ca] ([Ca]) and high-molecular-weight glycoprotein secretion. Treatment with RvE1 or RvD1 for 30 minutes significantly blocked the LTB4-induced [Ca] increase. The actions of RvE1 on LTB4-induced [Ca] increase were reversed by siRNA for the RvE1 receptor, and the actions of RvD1 were reversed by an RvD1 receptor inhibitor. The RvE1 and RvD1 block of LTB4-stimulated increase in [Ca] was also reversed by an inhibitory peptide to β-adrenergic receptor kinase. LTB4 and block of the LTB4-stimulated increase in [Ca] by RvE1 and RvD1 were partially mediated by the depletion of intracellular Ca stores. RvE1, but not RvD1, counterregulated the LTB4-induced high-molecular-weight glycoprotein secretion. Thus, both RvE1 and RvD1 receptors directly inhibit LTB4 by phosphorylating the LTB4 receptor using β adrenergic receptor kinase. RvE1 receptor counterregulates the LTB4-induced increase in [Ca] and secretion, whereas RvD1 receptor only counterregulates LTB4-induced [Ca] increase.
Yang Y, Huang X, Ma G, Cui J, Matsubara JA, Kazlauskas A, Zhao J, Wang J, Lei H. PDGFRβ plays an essential role in patient vitreous-stimulated contraction of retinal pigment epithelial cells from epiretinal membranes. Exp Eye Res 2020;197:108116.Abstract
Platelet-derived growth factor (PDGF) is associated with clinical proliferative vitreoretinopathy (PVR), which is characterized by formation of sub- or epi-retinal membranes that consist of cells including retinal pigment epithelial (RPE) cells and extracellular matrix. RPE cells play an important role in PVR pathogenesis. Previous findings indicated that PDGF receptor (PDGFR)α was essential in experimental PVR induced by fibroblasts. In RPE cells derived from epiretinal membranes from patients with PVR (RPEMs), Akt was activated by PDGF-B but not PDGF-A, which suggested that PDGFRβ was the predominant PDGFR isoform expressed in RPEMs. Indeed, CRISPR/Cas9-mediated depletion of PDGFRβ in RPEMs attenuated patient vitreous-induced Akt activation and cellular responses intrinsic to PVR including cell proliferation, migration, and contraction. We conclude that PDGFRβ appears to be the PVR relevant PDGFR isoform in RPEMs.
Yang J, LeBlanc ME, Cano I, Saez-Torres KL, Saint-Geniez M, Ng Y-S, D'Amore PA. ADAM10 and ADAM17 proteases mediate proinflammatory cytokine-induced and constitutive cleavage of endomucin from the endothelial surface. J Biol Chem 2020;295(19):6641-6651.Abstract
Contact between inflammatory cells and endothelial cells (ECs) is a crucial step in vascular inflammation. Recently, we demonstrated that the cell-surface level of endomucin (EMCN), a heavily -glycosylated single-transmembrane sialomucin, interferes with the interactions between inflammatory cells and ECs. We have also shown that, in response to an inflammatory stimulus, EMCN is cleared from the cell surface by an unknown mechanism. In this study, using adenovirus-mediated overexpression of a tagged EMCN in human umbilical vein ECs, we found that treatment with tumor necrosis factor α (TNF-α) or the strong oxidant pervanadate leads to loss of cell-surface EMCN and increases the levels of the C-terminal fragment of EMCN 3- to 4-fold. Furthermore, treatment with the broad-spectrum matrix metalloproteinase inhibitor batimastat (BB94) or inhibition of ADAM metallopeptidase domain 10 (ADAM10) and ADAM17 with two small-molecule inhibitors, GW280264X and GI254023X, or with siRNA significantly reduced basal and TNFα-induced cell-surface EMCN cleavage. Release of the C-terminal fragment of EMCN by TNF-α treatment was blocked by chemical inhibition of ADAM10 alone or in combination with ADAM17. These results indicate that cell-surface EMCN undergoes constitutive cleavage and that TNF-α treatment dramatically increases this cleavage, which is mediated predominantly by ADAM10 and ADAM17. As endothelial cell-surface EMCN attenuates leukocyte-EC interactions during inflammation, we propose that EMCN is a potential therapeutic target to manage vascular inflammation.
Yang M, Lippestad M, Hodges RR, Fjærvoll HK, Fjærvoll KA, Bair JA, Utheim TP, Serhan CN, Dartt DA. RvE1 uses the LTB receptor BLT1 to increase [Ca] and stimulate mucin secretion in cultured rat and human conjunctival goblet cells. Ocul Surf 2020;18(3):470-482.Abstract
PURPOSE: Specialized pro-resolving lipid mediator resolvin (Rv) E1 stimulates secretion including mucins from conjunctival goblet cells. RvE1 can use both its ChemR23 receptor and the LTB receptor BLT1 to increase [Ca]. The purpose of this study was to determine the expression of ChemR23 and BLT1 and receptors on conjunctival goblet cells and the respective roles these two receptors play in goblet cell responses to RvE1. METHODS: Goblet cells were cultured from male rat or human conjunctiva from both sexes. Western blotting analysis, reverse transcription PCR and immunofluorescence microscopy were used to demonstrate the expression of ChemR23 and BLT1 in conjunctival goblet cells. High molecular weight glycoprotein secretion was determined using an enzyme-linked lectin assay. Signaling pathways were studied by measuring the increase in [Ca] using fura 2/AM. RESULTS: ChemR23 and BLT1 and receptors were present on both rat and human conjunctival goblet cells. The BLT1 inhibitors LY293111 and U75302 significantly blocked RvE1-and LTB-stimulated [Ca] increase. RvE1-and LTB-stimulated [Ca] and secretion increases were blocked by BLT1-targeted siRNA. RvE1-stimulated [Ca] and secretion increases were also blocked by ChemR23-targeted siRNA. Addition of RvE1 2 min before or simultaneously with LTB desensitized the LTB [Ca] response. Addition of RvE1 and LTB simultaneously caused secretion that was decreased compared to either response alone. CONCLUSION: RvE1, in addition to the ChemR23 receptor, uses the BLT1 receptor to increase [Ca] and stimulate secretion in both rat and human cultured conjunctival goblet cells.
Yousefi S, Elze T, Pasquale LR, Saeedi O, Wang M, Shen LQ, Wellik SR, De Moraes CG, Myers JS, Boland MV. Monitoring Glaucomatous Functional Loss Using an Artificial Intelligence-Enabled Dashboard. Ophthalmology 2020;127(9):1170-1178.Abstract
PURPOSE: To develop an artificial intelligence (AI) dashboard for monitoring glaucomatous functional loss. DESIGN: Retrospective, cross-sectional, longitudinal cohort study. PARTICIPANTS: Of 31 591 visual fields (VFs) on 8077 subjects, 13 231 VFs from the most recent visit of each patient were included to develop the AI dashboard. Longitudinal VFs from 287 eyes with glaucoma were used to validate the models. METHOD: We entered VF data from the most recent visit of glaucomatous and nonglaucomatous patients into a "pipeline" that included principal component analysis (PCA), manifold learning, and unsupervised clustering to identify eyes with similar global, hemifield, and local patterns of VF loss. We visualized the results on a map, which we refer to as an "AI-enabled glaucoma dashboard." We used density-based clustering and the VF decomposition method called "archetypal analysis" to annotate the dashboard. Finally, we used 2 separate benchmark datasets-one representing "likely nonprogression" and the other representing "likely progression"-to validate the dashboard and assess its ability to portray functional change over time in glaucoma. MAIN OUTCOME MEASURES: The severity and extent of functional loss and characteristic patterns of VF loss in patients with glaucoma. RESULTS: After building the dashboard, we identified 32 nonoverlapping clusters. Each cluster on the dashboard corresponded to a particular global functional severity, an extent of VF loss into different hemifields, and characteristic local patterns of VF loss. By using 2 independent benchmark datasets and a definition of stability as trajectories not passing through over 2 clusters in a left or downward direction, the specificity for detecting "likely nonprogression" was 94% and the sensitivity for detecting "likely progression" was 77%. CONCLUSIONS: The AI-enabled glaucoma dashboard, developed using a large VF dataset containing a broad spectrum of visual deficit types, has the potential to provide clinicians with a user-friendly tool for determination of the severity of glaucomatous vision deficit, the spatial extent of the damage, and a means for monitoring the disease progression.
Yu M, Lee S-M, Lee HS, Amouzegar A, Nakao T, Chen Y, Dana R. Neurokinin-1 Receptor Antagonism Ameliorates Dry Eye Disease by Inhibiting Antigen-Presenting Cell Maturation and T Helper 17 Cell Activation. Am J Pathol 2020;190(1):125-133.Abstract
Neuroinflammation plays an important role in the pathogenesis of ocular surface disease, including dry eye disease (DED), but little is known about the contribution of substance P (SP) to DED. In this study, we investigated the expression of SP at the ocular surface and evaluated its effect on maturation of antigen-presenting cells (APCs), the key cell component involved in the induction of type 17 helper T-cell (Th17) response in DED. The effect of topical blockade of SP signaling was further investigated using neurokinin-1 receptor (NK1R) inhibitors on APC maturation, Th17 cell activation, and disease severity in a mouse model of DED. The results demonstrate that SP is constitutively expressed at the ocular surface, and trigeminal ganglion neurons are the major source of SP in DED. SP derived from trigeminal ganglion enhanced the expression of major histocompatibility complex class II maturation marker by bone marrow-derived dendritic cells, an effect that is abrogated by blockade of SP signaling using NK1R antagonist spantide. Finally, using a well-established murine model of DED, topical treatment of DED mice with NK1R antagonists CP-99,994 and L-733,060 suppressed APC acquisition of major histocompatibility complex class II, reduced Th17 cell activity, and ameliorated DED severity. These findings are of translational value, as they suggest that antagonizing NK1R-mediated SP signaling may be an effective strategy in suppressing Th17-mediated ocular surface disease.
Yu G, Seto BK, Yamada K, Zeng K, Arroyo JG. Combined Pneumatic and Enzymatic Vitreolysis for Severe Cases of Vitreomacular Traction. Retin Cases Brief Rep 2020;Abstract
PURPOSE: To evaluate the efficacy of combined pneumatic and enzymatic vitreolysis for treatment of severe cases of vitreomacular traction (VMT). METHODS: We analyzed a retrospective, consecutive series of five patients diagnosed with severe VMT refractory to pneumatic vitreolysis (PV) who then received an additional ocriplasmin injection while their gas bubble from PV was still present between February 2015 to February 2019. VMT release was confirmed using spectral domain optical coherence tomography (OCT). RESULTS: Four out of 5 patients treated with combined pneumatic and enzymatic vitreolysis achieved VMT release by day 28, and all cases eventually achieved complete VMT release. In addition to having VMT refractory to PV, patient characteristics included broad adhesion diameter (>1500 μm, n=1), presence of epiretinal membrane (n=2), age > 65 years (n=4), and pseudophakia (n=1). Visual acuity (VA) improved by 3 or more lines at 6 months in both of the patients with initial vision worse than 20/50 on an ETDRS chart but not in those whose vision was already fairly good (i.e. VA > 20/60). None of the patients experienced the following complications after receiving this combined treatment: retinal tears or detachments, vitreous floaters, and ellipsoid zone changes. CONCLUSION: Sequential, combined pneumatic and enzymatic vitreolysis resulted in VMT release in all 5 cases (4 cases by 28 days) and may be a potentially useful alternative to surgical intervention for refractory VMT cases.
Yu Z, Ma S, Wu M, Cui H, Wu R, Chen S, Xu C, Lu X, Feng S. Self-assembling hydrogel loaded with 5-FU PLGA microspheres as a novel vitreous substitute for proliferative vitreoretinopathy. J Biomed Mater Res A 2020;108(12):2435-2446.Abstract
The vitreous substitute for proliferative vitreoretinopathy (PVR) surgery remains an unmet clinical need in ophthalmology. In our study, we developed an in situ formed hydrogel by crosslinking polyvinyl alcohol (PVA) and chitosan as a potential vitreous substitute. 5-fluorouracil (5-FU) Poly (lactic-co-glycolic acid) (PLGA) microspheres were developed and loaded onto the PVA/chitosan hydrogels to treat PVR. In vitro, PVA/chitosan hydrogels at four concentrations were subjected to morphological, physical, rheological analyses, and cytotoxicity was evaluated together with the characterization of 5-FU PLGA microspheres. In vivo, pharmacologically induce PVR rabbits were performed a vitrectomy. In the PVA group, 3% PVA/chitosan hydrogel was injected into the vitreous cavity. In the PVA/MS group, 3% PVA/chitosan hydrogel and 5-FU PLGA microspheres were injected. In the Control group, phosphate-buffered saline was injected. Therapeutic efficacy was evaluated with postoperative examinations and histological analyses. This study demonstrated that the 3% PVA/chitosan hydrogel showed properties similar to those of the human vitreous and could be a novel in situ crosslinked vitreous substitute for PVR. Loading 5-FU PLGA microspheres onto this hydrogel may represent an effective strategy to improve the prognosis of PVR.
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Zampaglione E, Kinde B, Place EM, Navarro-Gomez D, Maher M, Jamshidi F, Nassiri S, Mazzone AJ, Finn C, Schlegel D, Comander J, Pierce EA, Bujakowska KM. Copy-number variation contributes 9% of pathogenicity in the inherited retinal degenerations. Genet Med 2020;22(6):1079-1087.Abstract
PURPOSE: Current sequencing strategies can genetically solve 55-60% of inherited retinal degeneration (IRD) cases, despite recent progress in sequencing. This can partially be attributed to elusive pathogenic variants (PVs) in known IRD genes, including copy-number variations (CNVs), which have been shown as major contributors to unsolved IRD cases. METHODS: Five hundred IRD patients were analyzed with targeted next-generation sequencing (NGS). The NGS data were used to detect CNVs with ExomeDepth and gCNV and the results were compared with CNV detection with a single-nucleotide polymorphism (SNP) array. Likely causal CNV predictions were validated by quantitative polymerase chain reaction (qPCR). RESULTS: Likely disease-causing single-nucleotide variants (SNVs) and small indels were found in 55.6% of subjects. PVs in USH2A (11.6%), RPGR (4%), and EYS (4%) were the most common. Likely causal CNVs were found in an additional 8.8% of patients. Of the three CNV detection methods, gCNV showed the highest accuracy. Approximately 30% of unsolved subjects had a single likely PV in a recessive IRD gene. CONCLUSION: CNV detection using NGS-based algorithms is a reliable method that greatly increases the genetic diagnostic rate of IRDs. Experimentally validating CNVs helps estimate the rate at which IRDs might be solved by a CNV plus a more elusive variant.
Zantut PRA, Veras MM, Yariwake VY, Takahashi WY, Saldiva PH, Young LH, Damico FM, Fajersztajn L. Effects of cannabis and its components on the retina: a systematic review. Cutan Ocul Toxicol 2020;39(1):1-9.Abstract
Cannabis is the most prevalent drug in the world and its consumption is growing. Cannabinoid receptors are present in the human central nervous system. Recent studies show evidence of the effects of cannabinoids on the retina, and synthesising the results of these studies may be relevant for ophthalmologists. Thus, this review adopts standardised, systematic review methodology to investigate the effects of exposure to cannabis and components on the retina. We searched five online databases for the combined terms for outcome ("retina") and exposure ("cannabis"). Eligibility of studies were conducted by two independent reviewers, and risk of bias was assessed. We retrieved 495 studies, screened 229 studies, assessed 52 studies for eligibility, and included 16 studies for qualitative analysis. The cannabinoids most frequently investigated were delta-9-tetrahydrocannabinol (THC), abnormal cannabidiol, synthetic cannabinoid, and cannabidiol (CDB). The outcomes most studied were neuroretinal dysfunction, followed by vascular effects. The studies also included investigation of neuroprotective and anti-inflammatory effects and teratogenic effects. This review suggests that cannabinoids may have an important role in retinal processing and function.
Zhang Y, Wang K, Pan J, Yang S, Yao H, Li M, Li H, Lei H, Jin H, Wang F. Exosomes mediate an epithelial-mesenchymal transition cascade in retinal pigment epithelial cells: Implications for proliferative vitreoretinopathy. J Cell Mol Med 2020;Abstract
Exosomes have recently emerged as a pivotal mediator of many physiological and pathological processes. However, the role of exosomes in proliferative vitreoretinopathy (PVR) has not been reported. In this study, we aimed to investigate the role of exosomes in PVR. Transforming growth factor beta 2 (TGFß-2) was used to induce epithelial-mesenchymal transition (EMT) of retinal pigment epithelial (RPE) cells, as an in vitro model of PVR. Exosomes from normal and EMTed RPE cells were extracted and identified. We incubated extracted exosomes with recipient RPE cells, and co-cultured EMTed RPE cells and recipient RPE cells in the presence of the exosome inhibitor GW4869. Both experiments suggested that there are further EMT-promoting effects of exosomes from EMTed RPE cells. MicroRNA sequencing was also performed to identify the miRNA profiles in exosomes from both groups. We identified 34 differentially expressed exosomal miRNAs (P <. 05). Importantly, miR-543 was found in exosomes from EMTed RPE cells, and miR-543-enriched exosomes significantly induced the EMT of recipient RPE cells. Our study demonstrates that exosomal miRNA is differentially expressed in RPE cells during EMT and that these exosomal miRNAs may play pivotal roles in EMT induction. Our results highlight the importance of exosomes as cellular communicators within the microenvironment of PVR.
Zheng Q, Jones FK, Leavitt SV, Ung L, Labrique AB, Peters DH, Lee EC, Azman AS, Azman AS. HIT-COVID, a global database tracking public health interventions to COVID-19. Sci Data 2020;7(1):286.Abstract
The COVID-19 pandemic has sparked unprecedented public health and social measures (PHSM) by national and local governments, including border restrictions, school closures, mandatory facemask use and stay at home orders. Quantifying the effectiveness of these interventions in reducing disease transmission is key to rational policy making in response to the current and future pandemics. In order to estimate the effectiveness of these interventions, detailed descriptions of their timelines, scale and scope are needed. The Health Intervention Tracking for COVID-19 (HIT-COVID) is a curated and standardized global database that catalogues the implementation and relaxation of COVID-19 related PHSM. With a team of over 200 volunteer contributors, we assembled policy timelines for a range of key PHSM aimed at reducing COVID-19 risk for the national and first administrative levels (e.g. provinces and states) globally, including details such as the degree of implementation and targeted populations. We continue to maintain and adapt this database to the changing COVID-19 landscape so it can serve as a resource for researchers and policymakers alike.
Zhu Y, Cui Y, Wang JC, Lu Y, Zeng R, Katz R, Wu DM, Eliott D, Vavvas DG, Husain D, Miller JW, Kim LA, Miller JB. Different Scan Protocols Affect the Detection Rates of Diabetic Retinopathy Lesions by Wide-Field Swept-Source Optical Coherence Tomography Angiography. Am J Ophthalmol 2020;215:72-80.Abstract
PURPOSE: To compare different scan protocols of wide-field swept-source optical coherence tomography angiography (SS-OCTA) for the detection of diabetic retinopathy (DR) lesions. DESIGN: Comparison of diagnostic approaches. METHODS: A prospective, observational study was conducted at Massachusetts Eye and Ear from December 2018 to July 2019. Proliferative diabetic retinopathy (PDR), nonproliferative diabetic retinopathy (NPDR), and diabetic patients without DR were included. All patients were imaged using SS-OCTA using the following scan protocol: 3- × 3-mm Angio centered on the fovea; 6- × 6-mm Angio centered on the fovea and the optic disc; 15- × 9-mm Montage; and 12- × 12-mm Angio centered on the fovea and the optic disc. Images were independently evaluated by 2 graders for the presence or absence of DR lesions including microaneurysms, intraretinal microvascular abnormalities, neovascularization, nonperfusion areas, venous looping, and hard exudates. All statistical analyses were performed using commercial software. RESULTS: A total of 176 eyes in 119 participants were included in the study. The detection rate of neovascularization on 6- × 6-mm Angio centered on the fovea was approximately one-half that on 15- × 9-mm Montage (P < .05) imaging. Combining 6- × 6-mm Angio imaging centered on the fovea and the optic disc could increase the rate to approximately two-thirds (P < .05). The 12- × 12-mm Angio imaging centered on the combination of fovea and optic disc had detection rates comparable to those of 15- × 9-mm Montage imaging for all DR lesions (P > .05). For microaneurysms, 6- × 6-mm Angio had better performance than 15- × 9-mm Montage (P < .05). CONCLUSIONS: Wide-field SS-OCTA images were useful in detecting DR lesions. The 12- × 12-mm Angio imaging centered on the fovea and on the optic disc may be an optimal balance between speed and efficacy for evaluation of DR in clinical practice.
Zieske JD, Hutcheon AEK, Guo X. Extracellular Vesicles and Cell-Cell Communication in the Cornea. Anat Rec (Hoboken) 2020;303(6):1727-1734.Abstract
One question that has intrigued cell biologists for many years is, "How do cells interact to influence one another's activity?" The discovery of extracellular vesicles (EVs) and the fact that they carry cargo, which directs cells to undergo changes in morphology and gene expression, has revolutionized this field of research. Little is known regarding the role of EVs in the cornea; however, we have demonstrated that EVs isolated from corneal epithelial cells direct corneal keratocytes to initiate fibrosis. Intriguingly, our data suggest that EVs do not penetrate epithelial basement membrane (BM), perhaps providing a mechanism explaining the importance of BM in the lack of scarring in scrape wounds. Since over 100-million people worldwide suffer from visual impairment as a result of corneal scarring, the role of EVs may be vital to understanding the mechanisms of wound repair. Therefore, we investigated EVs in ex vivo and in vivo-like three-dimensional cultures of human corneal cells using transmission electron microscopy. Some of the major findings were all three major cell types (epithelial, fibroblast, and endothelial cells) appear to release EVs, EVs can be identified using TEM, and EVs appeared to be involved in cell-cell communication. Interestingly, while our previous publication suggests that EVs do not penetrate the epithelial BM, it appears that EVs penetrate the much thicker endothelial BM (Descemet's membrane). These findings indicate the huge potential of EV research in the cornea and wound healing, and suggest that during homeostasis the endothelium and stromal cells are in communication. Anat Rec, 2019. © 2019 The Authors. The Anatomical Record published by Wiley Periodicals, Inc. on behalf of American Association of Anatomists.
Zucker CL, Bernstein PS, Schalek RL, Lichtman JW, Dowling JE. A connectomics approach to understanding a retinal disease. Proc Natl Acad Sci U S A 2020;117(31):18780-18787.Abstract
Macular telangiectasia type 2 (MacTel), a late-onset macular degeneration, has been linked to a loss in the retina of Müller glial cells and the amino acid serine, synthesized by the Müller cells. The disease is confined mainly to a central retinal region called the MacTel zone. We have used electron microscopic connectomics techniques, optimized for disease analysis, to study the retina from a 48-y-old woman suffering from MacTel. The major observations made were specific changes in mitochondrial structure within and outside the MacTel zone that were present in all retinal cell types. We also identified an abrupt boundary of the MacTel zone that coincides with the loss of Müller cells and macular pigment. Since Müller cells synthesize retinal serine, we propose that a deficiency of serine, required for mitochondrial maintenance, causes mitochondrial changes that underlie MacTel development.
van Zyl T, Yan W, McAdams A, Peng Y-R, Shekhar K, Regev A, Juric D, Sanes JR. Cell atlas of aqueous humor outflow pathways in eyes of humans and four model species provides insight into glaucoma pathogenesis. Proc Natl Acad Sci U S A 2020;117(19):10339-10349.Abstract
Increased intraocular pressure (IOP) represents a major risk factor for glaucoma, a prevalent eye disease characterized by death of retinal ganglion cells; lowering IOP is the only proven treatment strategy to delay disease progression. The main determinant of IOP is the equilibrium between production and drainage of aqueous humor, with compromised drainage generally viewed as the primary contributor to dangerous IOP elevations. Drainage occurs through two pathways in the anterior segment of the eye called conventional and uveoscleral. To gain insights into the cell types that comprise these pathways, we used high-throughput single-cell RNA sequencing (scRNAseq). From ∼24,000 single-cell transcriptomes, we identified 19 cell types with molecular markers for each and used histological methods to localize each type. We then performed similar analyses on four organisms used for experimental studies of IOP dynamics and glaucoma: cynomolgus macaque (), rhesus macaque (), pig (), and mouse (). Many human cell types had counterparts in these models, but differences in cell types and gene expression were evident. Finally, we identified the cell types that express genes implicated in glaucoma in all five species. Together, our results provide foundations for investigating the pathogenesis of glaucoma and for using model systems to assess mechanisms and potential interventions.

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