Cell types are the basic building blocks of multicellular organisms and are extensively diversified in animals. Despite recent advances in characterizing cell types, classification schemes remain ambiguous. We propose an evolutionary definition of a cell type that allows cell types to be delineated and compared within and between species. Key to cell type identity are evolutionary changes in the 'core regulatory complex' (CoRC) of transcription factors, that make emergent sister cell types distinct, enable their independent evolution and regulate cell type-specific traits termed apomeres. We discuss the distinction between developmental and evolutionary lineages, and present a roadmap for future research.
The function of the meibomian gland in the upper and lower eyelids is critical to maintaining homeostasis at the ocular surface. Highly specialized meibocytes within the gland must differentiate and accumulate intracellular lipid droplets that are released into the tear film following rupture of the cell membrane. Proteases and their inhibitors have been recognized as key players in remodeling extracellular matrices and promoting the normal integrity of glandular tissue. They modulate a wide range of biological processes, such as cell proliferation and differentiation, and can contribute to disease when aberrantly expressed. Deciphering the role of proteolytic activity in the meibomian gland offers an opportunity to gain a more comprehensive and fundamental understanding of the developmental, physiological, and pathological processes associated with this gland.
The cornea is a transparent avascular tissue on the anterior segment of the eye responsible for providing refractive power and forming a protective barrier against the external environment. Infectious and inflammatory conditions can compromise the structure of the cornea, leading to visual impairment and blindness. Galectins are a group of β-galactoside-binding proteins expressed by immune and non-immune cells that play pivotal roles in innate and adaptive immunity. In this brief review, we discuss how different members of this family of proteins affect both pro-inflammatory and anti-inflammatory responses in the cornea, particularly in the context of infection, transplantation and wound healing. We further describe recent research showing beneficial effects of galectin-targeted therapy in corneal diseases.
The glycocalyx is a dense and diverse coat of glycans and glycoconjugates responsible for maintaining cell surface integrity and regulating the interaction of cells with the external environment. Transmembrane mucins such as MUC1 and MUC16 comprise a major component of the epithelial glycocalyx and are currently used to monitor disease progression in cancer. At the ocular surface, multiple lines of evidence indicate that abnormal expression of the enzymes responsible for glycan biosynthesis during pathological conditions impairs the glycosylation of transmembrane mucins. It is now becoming clear that these changes contribute to modify the interaction of mucins with galectin-3, a multimeric lectin crucial for preserving the ocular surface epithelial barrier. This review highlights the potential of using the epithelial glycocalyx as a reliable source for the generation of biomarkers to diagnose and monitor ocular surface disease.
Glycosylation is an important and common form of posttranscriptional modification of proteins in cells. During the last decade, a vast array of biological functions has been ascribed to glycans because of a rapid evolution in glycomic technologies. Glycogenes that are highly expressed at the human ocular surface include families of glycosyltransferases, proteoglycans, and glycan degradation proteins, as well as mucins and carbohydrate-binding proteins, such as the galectins. On the apical glycocalyx, mucin O-glycans promote boundary lubrication, prevent bacterial adhesion and endocytic activity, and maintain epithelial barrier function through interactions with galectins. The emerging roles attributed to glycans are contributing to the appreciation of their biological capabilities at the ocular surface.
Mucins are an ancient group of glycoproteins that provide viscoelastic, lubricating and hydration properties to fluids bathing wet surfaced epithelia. They are involved in the protection of underlying tissues by forming a barrier with selective permeability properties. The expression, processing and spatial distribution of mucins are often determined by organ-specific requirements that in the eye involve protecting against environmental insult while allowing the passage of light. The human ocular surface epithelia have evolved to produce an extremely thin and watery tear film containing a distinct soluble mucin product secreted by goblet cells outside the visual axis. The adaptation to the ocular environment is notably evidenced by the significant contribution of transmembrane mucins to the tear film, where they can occupy up to one-quarter of its total thickness. This article reviews the tissue-specific properties of human ocular mucins, methods of isolation and detection, and current approaches to model mucin systems recapitulating the human ocular surface mucosa. This knowledge forms the fundamental basis to develop applications with a promising biological and clinical impact.
Obtaining a clear assessment of the anterior segment is critical for disease diagnosis and management in ophthalmic telemedicine. The anterior segment can be imaged with slit lamp cameras, robotic remote controlled slit lamps, cell phones, cell phone adapters, digital cameras, and webcams, all of which can enable remote care. The ability of these devices to identify various ophthalmic diseases has been studied, including cataracts, as well as abnormalities of the ocular adnexa, cornea, and anterior chamber. This article reviews the current state of anterior segment imaging for the purpose of ophthalmic telemedical care.
Use of ophthalmic telemedicine for patients with age-related macular degeneration (AMD) has shown remarkable advances over recent years. The recent COVID pandemic accelerated this transition since in-person evaluation of elderly patients at high risk for advanced AMD and severe vision loss were also at higher risk for complications from COVID infection. To date, ophthalmic telemedicine has been successfully used in remote retinal consultation by general ophthalmologists for AMD management, hybrid testing visits with both in-office testing and remote evaluation, as well as early successes in home-based remote monitoring of patients with high-risk AMD. We therefore review the current literature and evidence base related to ophthalmic telemedicine for AMD.
Importance: Individuals with autosomal dominant mutations for Alzheimer disease are valuable in determining biomarkers present prior to the onset of cognitive decline, improving the ability to diagnose Alzheimer disease as early as possible. Optical coherence tomography (OCT) has surfaced as a potential noninvasive technique capable of analyzing central nervous system tissues for biomarkers of Alzheimer disease. Objective: To evaluate whether OCT can detect early retinal alterations in carriers of the presenilin 1 (PSEN1 [OMIM 104311]) E280A mutation who are cognitively unimpaired. Design, Setting, and Participants: A cross-sectional imaging study conducted from July 13, 2015, to September 16, 2020, included 10 carriers of the PSEN1 E280A mutation who were cognitively unimpaired and 10 healthy noncarrier family members, all leveraged from a homogenous Colombian kindred. Statistical analysis was conducted from September 9, 2017, to September 16, 2020. Main Outcomes and Measures: Mixed-effects multiple linear regression was performed to compare the thickness values of the whole retina and individual retinal layers on OCT scans between mutation carriers and noncarriers. Simple linear-effects and mixed-effects multiple linear regression models were used to assess whether age was an effect modifier for PSEN1 mutation of amyloid β levels and retinal thickness, respectively. Fundus photographs were used to compare the number of arterial and venous branch points, arterial and venous tortuosity, and fractal dimension. Results: This study included 10 carriers of the PSEN1 E280A mutation who were cognitively unimpaired (7 women [70%]; mean [SD] age, 36.3 [8.1] years) and 10 healthy noncarrier family members (7 women [70%]; mean [SD] age, 36.4 [8.2] years). Compared with noncarrier controls, PSEN1 mutation carriers who were cognitively unimpaired had a generalized decrease in thickness of the whole retina as well as individual layers detected on OCT scans, with the inner nuclear layer (outer superior quadrant, β = -3.06; P = .007; outer inferior quadrant, β = -2.60; P = .02), outer plexiform layer (outer superior quadrant, β = -3.44; P = .03), and outer nuclear layer (central quadrant, β = -8.61; P = .03; inner nasal quadrant, β = -8.39; P = .04; inner temporal quadrant, β = -9.39; P = .02) showing the greatest amount of statistically significant thinning. Age was a significant effect modifier for the association between PSEN1 mutation and amyloid β levels in cortical regions (β = 0.03; P = .001) but not for the association between PSEN1 mutation and retinal thickness. No statistical difference was detected in any of the vascular parameters studied. Conclusions and Relevance: These findings suggest that OCT can detect functional and morphologic changes in the retina of carriers of familial Alzheimer disease who are cognitively unimpaired several years before clinical onset, suggesting that OCT findings and retinal vascular parameters may be biomarkers prior to the onset of cognitive decline.
PURPOSE: Mutation of RGR, encoding retinal G-protein coupled receptor was originally reported in association with retinal dystrophy in 1999. A single convincing recessive variant segregated perfectly in one family of five affected and two unaffected siblings. At least one further individual, homozygous for the same variant has since been reported. The aim of this report was to reevaluate the findings in consideration of data from a whole genome sequencing (WGS) study of a large cohort of retinal dystrophy families. METHODS: Whole genome sequencing was performed on 599 unrelated probands with inherited retinal disease. Detailed phenotyping was performed, including clinical evaluation, electroretinography, fundus photography, fundus autofluorescence imaging (FAF) and spectral-domain optical coherence tomography (OCT). RESULTS: Overall we confirmed that affected individuals from six unrelated families were homozygous for both the reported RGR p.Ser66Arg variant and a nearby frameshifting deletion in CDHR1 (p.Ile841Serfs119*). All had generalized rod and cone dysfunction with severe macular involvement. An additional proband was heterozygous for the same CDHR1/RGR haplotype but also carried a second null CDHR1 mutation on a different haplotype. A comparison of the clinical presentation of the probands reported here with other CDHR1-related retinopathy patients shows the phenotypes to be similar in presentation, severity, and rod/cone involvement. CONCLUSIONS: These data suggest that the recessive retinal disorder previously reported to be due to homozygous mutation in RGR is, at least in part, due to variants in CDHR1 and that the true consequences of RGR knock-out on human retinal structure and function are yet to be determined.
PURPOSE: To report a case of successful medical treatment with oral posaconazole in refractory fungal keratitis caused by Paecilomyces lilacinus. METHODS: Case report. RESULTS: A 57-year-old male, soft contact lens wearer presented with irritation, pain, photophobia, and reduced vision. Slit-lamp examination showed a large corneal epithelial defect with a peripheral infiltrate. The patient did not improve on fortified topical antibiotics. After the diagnosis of P. lilacinus fungal keratitis, oral voriconazole and topical antifungal therapy were started. Despite antifungal therapy, progressive disease required therapeutic penetrating keratoplasty. Postoperatively, because of clinical signs of recurrence and in vivo confocal microscopy findings of presumed hyphae in the cornea, intracameral miconazole was injected and oral posaconazole was started. The patient improved and demonstrated no hyphae 6 weeks after starting posaconazole. When posaconazole was stopped, the cornea remained clear with excellent acuity. However, because of acute graft rejection 2 months after stopping posaconazole, keratoprosthesis was implanted, with no evidence of infection at surgery or during the 3.5-year follow-up. CONCLUSIONS: To the best of our knowledge, this is the first report on the use of oral posaconazole for Paecilomyces keratitis. Posaconazole might be indicated in the treatment of refractory Paecilomyces keratitis that is resistant to conventional therapy.
PURPOSE: To provide an update summarizing the biologic pathways governing von Hippel-Lindau (VHL) disease pathogenesis and to provide an overview of systemic manifestations as well as screening recommendations. METHODS: A PubMed search of the English language literature was reviewed using the following search terms: von Hippel-Lindau, von Hippel-Lindau disease, and VHL. Of 6,696 publications, the most current and pertinent information related to the pathogenesis and systemic aspects of VHL disease were included in this review. RESULTS: von Hippel-Lindau disease is one of the most frequently occurring multisystem familial cancer syndromes. The disease results from germline mutation in the VHL tumor suppressor gene on the short arm of chromosome 3. Mutation in the VHL gene affects multiple cellular processes including transcriptional regulation, extracellular matrix formation, apoptosis, and, in particular, the cellular adaptive response to hypoxia. As a result, there is widespread development of vascular tumors affecting the retina, brain, and spine, as well as a spectrum of benign and malignant tumors and/or cysts in visceral organs. CONCLUSION: The ophthalmologist plays a key role in VHL disease diagnosis, as retinal hemangioblastoma is frequently the first disease manifestation. Screening guidelines for individuals with known VHL disease, and those at risk of VHL disease, help to ensure early detection of potentially vision-threatening and life-threatening disease.
We assessed the sustained delivery effect of poly (lactic-co-glycolic) acid (PLGA)/vitamin E (VitE) microspheres (MSs) loaded with glial cell-derived neurotrophic factor (GDNF) alone (GDNF-MSs) or combined with brain-derived neurotrophic factor (BDNF; GDNF/BDNF-MSs) on migration of the human adult retinal pigment epithelial cell-line-19 (ARPE-19) cells, primate choroidal endothelial (RF/6A) cells, and the survival of isolated mouse retinal ganglion cells (RGCs). The morphology of the MSs, particle size, and encapsulation efficiencies of the active substances were evaluated. In vitro release, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) cell viability, terminal deoxynucleotidyl transferase (TdT) deoxyuridine dUTP nick-end labelling (TUNEL) apoptosis, functional wound healing migration (ARPE-19; migration), and (RF/6A; angiogenesis) assays were conducted. The safety of MS intravitreal injection was assessed using hematoxylin and eosin, neuronal nuclei (NeuN) immunolabeling, and TUNEL assays, and RGC in vitro survival was analyzed. MSs delivered GDNF and co-delivered GDNF/BDNF in a sustained manner over 77 days. The BDNF/GDNF combination increased RPE cell migration, whereas no effect was observed on RF/6A. MSs did not alter cell viability, apoptosis was absent in vitro, and RGCs survived in vitro for seven weeks. In mice, retinal toxicity and apoptosis was absent in histologic sections. This delivery strategy could be useful as a potential co-therapy in retinal degenerations and glaucoma, in line with future personalized long-term intravitreal treatment as different amounts (doses) of microparticles can be administered according to patients' needs.
PURPOSE: We investigated the effects of a relatively inexpensive, non-invasive, short-term treatment with low-dose normobaric hyperoxia (NBH) on macular edema in patients with retinal vein occlusion (RVO). METHODS: Participants with macular edema associated with RVO were treated with 5 LPM of NBH via facemask (40% fraction of inspired oxygen, FIO2) for 3 h. Patients with non-fovea involving edema who elected to be observed returned for a second treatment 1 month later to test reproducibility. RESULTS: A 3-h session of NBH (n = 45) resulted in decreased maximum macular thickness (MMT) (mean 7.10%, t34=9.63 P<.001) and central macular thickness (CMT) (mean 4.64%, t34=6.90, P<.001) when compared to untreated eyes with RVO measured over the same period of time (n = 12) or their healthy fellow eye (n = 34; MMT:t34=-9.60, P<.001;CMT: t34=-6.72, P<.001). Patients who had a second NBH treatment 1 month later experienced a recurrence of their edema, but demonstrated a similar significant reduction in MMT and CMT after the second NBH treatment. CONCLUSIONS: Three-hour treatment with 40% FIO2 NBH results in a significant reduction in MMT and CMT. This study supports an ischemic mechanism for macular edema associated with retinal vein occlusion. TRANSLATIONAL RELEVANCE: Short-term low-dose normobaric hyperoxia is a simple, inexpensive, and ubiquitous treatment that may provide an alternate or adjunctive approach to treating macular edema in patients who are resistant to or cannot afford anti-VEGF medications.
PURPOSE: To identify factors predictive of remission of inflammation in new-onset anterior uveitis cases treated at tertiary uveitis care facilities.
DESIGN: Retrospective cohort study.
PARTICIPANTS: Patients seeking treatment at participating academic uveitis clinics within 90 days of initial diagnosis of anterior uveitis.
METHODS: Retrospective cohort study based on standardized chart review.
MAIN OUTCOME MEASURES: Factors predictive of remission (no disease activity without corticosteroid or immunosuppressive treatments at all visits during a 90-day period).
RESULTS: Nine hundred ninety eyes (687 patients) had a first-ever diagnosis of anterior uveitis within 90 days before initial presentation and had follow-up visits thereafter. The median follow-up time was 160 days. Systemic diagnoses with juvenile idiopathic arthritis (JIA; adjusted hazard ratio [aHR], 0.38; 95% confidence interval [CI], 0.19-0.74) and Behçet's disease (aHR, 0.10; 95% CI, 0.01-0.85) were associated with a lower incidence of uveitis remission. Cases of bilateral uveitis (aHR, 0.68; 95% CI, 0.54-0.87) and those with a history of cataract surgery before presentation (aHR, 0.51; 95% CI, 0.29-0.87) also had a lower incidence of remission. Regarding clinical findings at the initial visit, a high degree of vitreous cells at initial presentation was associated with a lower incidence of remission (for 1+ or more vs. none: aHR, 0.72; 95% CI, 0.55-0.95). An initial visual acuity of 20/200 or worse, with respect to 20/40 or better, also was predictive of a lower incidence of remission (aHR, 0.52; 95% CI, 0.32-0.86).
CONCLUSIONS: Factors associated with a lower incidence of remission among new-onset anterior uveitis cases included diagnosis with JIA, Behçet's disease, bilateral uveitis, history of cataract surgery, findings of 1+ or more vitreous cells at presentation, and an initial visual acuity of 20/200 or worse. Patients with these risk factors seem to be at higher risk of persistent inflammation; reciprocally, patients lacking these factors would be more likely to experience remission. Patients with risk factors for nonremission of uveitis should be managed taking into account the higher probability of a chronic inflammatory course.
The cornea and its adnexa pose a unique situation of a tightly defined set of requirements for its function. This includes: transparency, perfect built to obtain appropriate refractive power, protective barrier from microbial invaders. Moreso, the cornea also endures extreme external physical conditions (temperature, high and low humidity, winds and alike). All these functions are maintained while preserving a constant state of homogenous wetting. Toward that end the cornea is equipped with an elaborated network of sensory neural network. While enabling the blinking reflex and maintaining the physiological steady state of wetting, this neural network also makes the cornea prone to the discomfort that with or without associated changes seen on medical examination. ISOPT Clinical 2018 discussion touched upon this hypercomplex situation, addressing the role of inflammation and its resulting discomfort in dry eye conditions. The discussion also engulfed the emerging neuropathic pain syndrome that is recently gaining more attention. Another related topic was the utilization of autologous serum tears and its ability to provide amelioration to desperate patients. Finally, the panel discussed the issue of treating corneal infection, including when and how to utilize steroids in the course of therapy. We assume the reader will find interest in this discussion that directly addresses issues seen day in and day out in our busy clinics.
Aschard H, Kang JH, Iglesias AI, Hysi P, Cooke Bailey JN, Khawaja AP, Allingham RR, Ashley-Koch A, Lee RK, Moroi SE, Brilliant MH, Wollstein G, Schuman JS, Fingert JH, Budenz DL, Realini T, Gaasterland T, Scott WK, Singh K, Sit AJ, Igo RP, Song YE, Hark L, Ritch R, Rhee DJ, Gulati V, Haven S, Vollrath D, Zack DJ, Medeiros F, Weinreb RN, Cheng C-Y, Chasman DI, Christen WG, Pericak-Vance MA, Liu Y, Kraft P, Richards JE, Rosner BA, Hauser MA, Hauser MA, Klaver CCW, van Duijn CM, Haines J, Wiggs JL, Pasquale LR. Genetic correlations between intraocular pressure, blood pressure and primary open-angle glaucoma: a multi-cohort analysis. Eur J Hum Genet 2017;25(11):1261-1267.Abstract
Primary open-angle glaucoma (POAG) is the most common chronic optic neuropathy worldwide. Epidemiological studies show a robust positive relation between intraocular pressure (IOP) and POAG and modest positive association between IOP and blood pressure (BP), while the relation between BP and POAG is controversial. The International Glaucoma Genetics Consortium (n=27 558), the International Consortium on Blood Pressure (n=69 395), and the National Eye Institute Glaucoma Human Genetics Collaboration Heritable Overall Operational Database (n=37 333), represent genome-wide data sets for IOP, BP traits and POAG, respectively. We formed genome-wide significant variant panels for IOP and diastolic BP and found a strong relation with POAG (odds ratio and 95% confidence interval: 1.18 (1.14-1.21), P=1.8 × 10-27) for the former trait but no association for the latter (P=0.93). Next, we used linkage disequilibrium (LD) score regression, to provide genome-wide estimates of correlation between traits without the need for additional phenotyping. We also compared our genome-wide estimate of heritability between IOP and BP to an estimate based solely on direct measures of these traits in the Erasmus Rucphen Family (ERF; n=2519) study using Sequential Oligogenic Linkage Analysis Routines (SOLAR). LD score regression revealed high genetic correlation between IOP and POAG (48.5%, P=2.1 × 10-5); however, genetic correlation between IOP and diastolic BP (P=0.86) and between diastolic BP and POAG (P=0.42) were negligible. Using SOLAR in the ERF study, we confirmed the minimal heritability between IOP and diastolic BP (P=0.63). Overall, IOP shares genetic basis with POAG, whereas BP has limited shared genetic correlation with IOP or POAG.
PURPOSE: Venous thromboembolic complications have been reported in association with coronavirus disease 2019 (COVID-19) infection. We raised awareness regarding a potential temporal association between COVID-19 infection and retinal vein occlusion (RVO). DESIGN: Multicenter, retrospective, nonconsecutive case series. SUBJECTS: Patients presenting with hemi-RVO (HRVO) or central RVO (CRVO) between March 2020 and March 2021, with confirmed COVID-19 infection, were included. The exclusion criteria were as follows: age >50 years, hypertension, diabetes, glaucoma, obesity, underlying hypercoagulable states, and those requiring intubation during hospitalization. METHODS: This was a multicenter, retrospective, nonconsecutive case series including patients presenting with hemi-RVO (HRVO) or central RVO (CRVO) between March 2020 and March 2021, with confirmed COVID-19 infection. The exclusion criteria were as follows: age >50 years, hypertension, diabetes, glaucoma, obesity, underlying hypercoagulable states, and those requiring intubation during hospitalization. MAIN OUTCOME MEASURES: Ophthalmic findings, including presenting and final visual acuity (VA), imaging findings, and clinical course. RESULTS: Twelve eyes of 12 patients with CRVO (9 of 12) or HRVO (3 of 12) after COVID-19 infection were included. The median age was 32 years (range, 18-50 years). Three patients were hospitalized, but none were intubated. The median time from COVID-19 diagnosis to ophthalmic symptoms was 6.9 weeks. The presenting VA ranged from 20/20 to counting fingers, with over half (7 of 12) having a VA of ≥20/40. OCT revealed macular edema in 42% of the eyes; of these, 80% (4 of 5) were treated with anti-VEGF injections. Ninety-two percent (11 of 12) had partial or complete resolution of ocular findings at final follow-up. Four eyes (33%) had retinal thinning, as determined using OCT, by the end of the study interval. The final VA ranged from 20/20 to 20/60, with 11 of the 12 (92%) eyes achieving a VA of ≥20/40 at a median final follow-up period of 13 weeks (range, 4-52 weeks). CONCLUSIONS: Although we acknowledge the high seroprevalence of COVID-19 and that a causal relationship cannot be established, we reported this series to raise awareness regarding the potential risk of retinal vascular events due to a heightened thromboinflammatory state associated with COVID-19 infection.