iPSC-derived retinal pigmented epithelial cells from patients with macular telangiectasia show decreased mitochondrial function.

Patient-derived induced pluripotent stem cells (iPSCs) provide a powerful tool for identifying cellular and molecular mechanisms of disease. Macular telangiectasia type 2 (MacTel) is a rare, late-onset degenerative retinal disease with an extremely heterogeneous genetic architecture, lending itself to the use of iPSCs. Whole-exome sequencing screens and pedigree analyses have identified rare causative mutations that account for less than 5% of cases. Metabolomic surveys of patient populations and GWAS have linked MacTel to decreased circulating levels of serine and elevated levels of neurotoxic 1-deoxysphingolipids (1-dSLs). However, retina-specific, disease-contributing factors have yet to be identified. Here, we used iPSC-differentiated retinal pigmented epithelial (iRPE) cells derived from donors with or without MacTel to screen for novel cell-intrinsic pathological mechanisms. We show that MacTel iRPE cells mimicked the low serine levels observed in serum from patients with MacTel. Through RNA-Seq and gene set enrichment pathway analysis, we determined that MacTel iRPE cells are enriched in cellular stress pathways and dysregulation of central carbon metabolism. Using respirometry and mitochondrial stress testing, we functionally validated that MacTel iRPE cells had a reduction in mitochondrial function that was independent of defects in serine biosynthesis and 1-dSL accumulation. Thus, we identified phenotypes that may constitute alternative disease mechanisms beyond the known serine/sphingolipid pathway.

Anti-retinal IgG antibodies in patients with early and advanced type 2 macular telangiectasia.

Type 2 idiopathic macular telangiectasia (MacTel-2) is a progressive adult-onset macular disease associated with bilateral perifoveal vascular changes, Muller cell degeneration and increased blood-retinal barrier permeability. The pathophysiological mechanisms of MacTel-2 remain unclear, however it was previously reported that anti-retinal antibodies in MacTel-2 patients are a significant feature of the disease. In this study, we aimed to compare the prevalence of anti-retinal antibodies in patients MacTel-2, healthy controls and patients with other retinal diseases. MacTel-2 patients diagnosed with multimodal imaging were enrolled and their disease severities were graded using spectral-domain optical coherence tomography. For comparison, patients with age-related macular degeneration (AMD), inherited retinal diseases (IRDs) or no retinal disease (healthy controls) were recruited as controls. Blood serum samples were screened for immunoglobulin G anti-retinal antibodies by western blotting, followed by densitometry analysis. Odds ratios (OR) with 95% confidence intervals (CI) were calculated and p < 0.05 considered statistically significant. Overall, anti-retinal antibody-positive cases were older (64 ± 15 vs 53 ± 17 years, p < 0.001) and females were more likely to develop anti-retinal antibodies (OR: 2.41, CI: 1.12-5.18). The frequency of anti-retinal antibody detection in MacTel-2 patients (n = 42, 36%) was not significantly different from healthy controls (n = 52, 25%) or IRD patients (n = 18, 25%) and the majority of MacTel-2 patients had no anti-retinal antibodies. In contrast, the frequency of anti-retinal antibody detection was significantly higher in patients with AMD (n = 15, 73%, p < 0.001). The lack of a greater anti-retinal antibody frequency or specificity in the MacTel-2 cohort suggests that antibody mediated immunological mechanisms may play a less significant role in MacTel-2 disease pathogenesis.

Genetic disruption of serine biosynthesis is a key driver of macular telangiectasia type 2 aetiology and progression.

BACKGROUND: Macular telangiectasia type 2 (MacTel) is a rare, heritable and largely untreatable retinal disorder, often comorbid with diabetes. Genetic risk loci subtend retinal vascular calibre and glycine/serine/threonine metabolism genes. Serine deficiency may contribute to MacTel via neurotoxic deoxysphingolipid production; however, an independent vascular contribution is also suspected. Here, we use statistical genetics to dissect the causal mechanisms underpinning this complex disease. METHODS: We integrated genetic markers for MacTel, vascular and metabolic traits, and applied Mendelian randomisation and conditional and interaction genome-wide association analyses to discover the causal contributors to both disease and spatial retinal imaging sub-phenotypes. RESULTS: Genetically induced serine deficiency is the primary causal metabolic driver of disease occurrence and progression, with a lesser, but significant, causal contribution of type 2 diabetes genetic risk. Conversely, glycine, threonine and retinal vascular traits are unlikely to be causal for MacTel. Conditional regression analysis identified three novel disease loci independent of endogenous serine biosynthetic capacity. By aggregating spatial retinal phenotypes into endophenotypes, we demonstrate that SNPs constituting independent risk loci act via related endophenotypes. CONCLUSIONS: Follow-up studies after GWAS integrating publicly available data with deep phenotyping are still rare. Here, we describe such analysis, where we integrated retinal imaging data with MacTel and other traits genomics data to identify biochemical mechanisms likely causing this disorder. Our findings will aid in early diagnosis and accurate prognosis of MacTel and improve prospects for effective therapeutic intervention. Our integrative genetics approach also serves as a useful template for post-GWAS analyses in other disorders.

Clinical features and prognostic factors in 71 eyes over 20 years from patients with Coats' disease in Korea.

This retrospective study assesses the clinical features, treatment strategies, and long-term outcomes of patients with Coats' disease in Korea. Multimodal imaging and medical records of consecutive patients treated between July 2000 and April 2020 at two tertiary centers were evaluated based on onset age (adult vs. childhood [< 18 years]). Factors associated with final visual acuity (VA) and risk of treatment failure were assessed. A total of 71 eyes of 67 patients were included, with subgrouping by onset age showing 45% childhood and 55% adult cases. Overall, Stage 2 disease was most common at presentation (76%), though childhood cases had more Stage 3b (22% vs. 3%, P = 0.02) and greater clock hours of retinal telangiectasia (7 vs. 5, P = 0.005). First-line treatment included laser (25%), combined laser/anti-VEGF (23%), cryotherapy (20%), surgery (16%), and anti-VEGF only (9%). Cryotherapy was associated with a higher risk for secondary interventions (OR 11.8, P < 0.001), required in 56% overall. Despite a 3-line VA decrease in 34% overall, adult cases had superior final VA (P = 0.037). Multivariable regression showed that the number of anti-VEGF injections performed during the initial treatment period was associated with a 9.4 letter improvement in vision (P = 0.041). We observed a higher proportion of adult-onset Coats' disease than previously reported in other non-Asian populations. An aggressive treatment with the addition of anti-VEGF may yield the most favorable long-term visual outcomes.

Subretinal Mononuclear Cells in Coats' Disease Studied with RPE65 and CD163: Evidence for Histiocytoid Pigment Epithelial Cells.

PURPOSE: To evaluate the mononuclear cells in the subretinal exudate in Coats' disease. DESIGN: Retrospective case series. METHODS: Five enucleated globes and 1 cytology sample from a patient with Coats' disease and 1 case of chronic retinal detachment following repair of an open globe injury were examined immunohistochemically to identify intraretinal and subretinal exudative cells. The 2 biomarkers were RPE65 for retinal pigment epithelium and CD163 for histiocytes, each tagged with different chromogens, yellow for pigment epithelium and purple for CD163-positive (CD163+) monocytes/histiocytes. Expression levels were sought from both biomarkers together and singly. A color shift to red in the cells' chromogenic reaction indicated the simultaneous presence of the 2 biomarkers. RESULTS: Most of the mononuclear cells in Coats' disease samples were CD163+ (purple), and a minority were RPE65+ (yellow). An intermediate number of cells were RPE65+/CD163+ (orange-red). The eye with a chronic retinal detachment had an equal distribution of CD163+ and RPE65+/CD163+ cells. CONCLUSIONS: RPE has several well-delineated phenotypes and functions. In normal visual physiology, the pigment epithelium supports photoreceptors and participates in their renewal by phagocytosis of the tips of the photoreceptors. The expression of CD163, a feature of hematopoietically derived monocytes, together with RPE65 in the retinal pigment epithelium, supports differentiation toward histiocytes. Yellow staining of detached pigment epithelial cells were rare. The presence of histiocytoid pigment epithelium at the Bruch membrane probably also has implications for macular degeneration.

Optical coherence tomographic features of macular telangiectasia type 2: Korean Macular Telangiectasia Type 2 Study-Report No. 1.

We analysed the imaging findings of macular telangiectasia (MacTel) type 2 in Korea using spectral domain optical coherence tomography (SD-OCT) and investigated their relationship with visual acuity and clinical stages. A retrospective multicentre cross-sectional study was conducted in six tertiary hospitals in Korea and included 129 patients. We analysed all the SD-OCT images encompassing the macular area. Hyporeflective cavities (77.7%) were the most frequently detected abnormalities in SD-OCT. Disruption of the external limiting membrane, ellipsoid zone, and interdigitation zone were found in 67 (40.4%), 87 (52.4%), and 94 eyes (56.6%), respectively. Four eyes (2.4%) had lamellar macular hole, and five eyes (3.0%) full-thickness macular hole. Neovascularisation, either subretinal or intraretinal, was found in 14 eyes (8.4%). Eyes with outer retinal hyperreflective band disruption had lower visual acuity than those without them. The presented characteristic clinical features of OCT in MacTel type 2 can not only aid in differentiating this disease from others but are also helpful for better judgement of the disease stage in daily clinical practice. Inner retinal hyporeflective cavities without outer retinal abnormalities on SD-OCT, although classified as severity scale 3, could be considered a relatively early stage in the disease process in terms of vision.

Coats retinopathy with pachychoroid and central serous chorioretinopathy in the fellow eye.

A 37-year-old man presented with blurring of vision and scotoma in the left eye since last 2 weeks and has a history of poor vision in his right eye since childhood. On examination, his best corrected visual acuity in the right eye was counting finger 1 m and 20/20, N/12 in the left eye. Fundus examination revealed features of Coats disease in the right eye and central serous chorioretinopathy (CSCR) in the left eye. He was given intravitreal triamcinolone acetonide injection in the right eye for reducing subretinal exudation. Simultaneously, focal laser photocoagulation was done to the CSCR leaks in the left eye to prevent the possible worsening of CSCR due to steroid injection in the fellow eye. He underwent cryotherapy to the retinal telangiectatic vessels 3 weeks after steroid injection in the right eye. Optical coherence tomography (OCT) of both eyes showed pachy vessels with a compression of overlying choriocapillaries. After 1 month, the condition of the right eye was unchanged and the CSCR in the left eye was completely resolved with the recovery of near visual acuity.

A 10-year review of histopathological findings of enucleated eyes from a tertiary-care center, Pakistan.

OBJECTIVE: To determine the histopathology of enucleated eye specimens. METHODS: The 10-year inventory was conducted at Aga Khan University Hospital, Karachi, and comprised all histopathology reports of enucleated eye specimens received from January 2007 to December 2016 by the Section of Histopathology, Department of Pathology. SPSS 19 was used for data analysis. RESULTS: A total of 232 ocular tissue specimens from 231 patients were evaluated. Ocular tumours were the most common histopathological diagnosis 186(80%). Among tumours, retinoblastoma was the most common 137(59%) followed by malignant melanoma 31(13%) and squamous cell carcinoma 15(6.5%). Overall, 16(6.9%) specimens had degenerative changes secondary to different ocular disorders. Staphyloma and Coat's disease was diagnosed in 3(1.3%) cases each. In 4(1.7%) cases, there was no formal diagnosis. CONCLUSIONS: Early identification of tumours may allow for conservative management and limit the need for enucleations.

Overlap between telangiectasia and photoreceptor loss increases with progression of macular telangiectasia type 2.

OBJECTIVES: To examine the topographical correlation between ellipsoid zone loss and telangiectasia in the deep capillary plexus in patients with macular telangiectasia type 2 (MacTel). METHODS: 38 eyes (20 subjects) diagnosed with MacTel were imaged with OCTA between March 2016 and June 2019 in this single center, cross-sectional observational study. The en face OCTA and OCT were evaluated for areas of deep capillary plexus telangiectasia and ellipsoid zone loss, respectively, and their outlines were superimposed to study their overlap (mm2). The primary outcome was percentage of overlap and its relationship to MacTel stage. Secondary outcomes included the relationship between neovascularization and hyperreflective foci as well as correlations between ellipsoid zone loss, deep capillary plexus telangiectasia and visual acuity. RESULTS: In nonproliferative MacTel stage, ellipsoid zone loss was localized to margins of telangiectatic areas (mean overlap = 15.2%). In proliferative stages, ellipsoid zone loss showed a higher degree of overlap with telangiectatic areas (mean overlap = 62.8%). Overlap increased with advancing MacTel stages, with an overall average of 45.3%. Overlap correlated highly with ellipsoid zone loss (r = 0.831; p<0.0001). Telangiectasia was present in all 38 eyes (range: 0.08mm2-0.99mm2), while ellipsoid zone loss was absent in 6 (range: 0.00-3.32mm2). Visual acuity correlated most strongly with ellipsoid zone loss (r = 0.569; p = 0.0002), followed by overlap (r = 0.544; p = 0.0004), and finally, telangiectasia (r = 0.404; p<0.0118). Presence of hyperreflective foci on OCT correlated with the presence and intraretinal location of neovascularization. CONCLUSIONS: Ellipsoid zone loss occurs at the margins of deep capillary plexus telangiectasia in nonproliferative MacTel, with progressively increasing overlap as MacTel advances, peaking in proliferative disease. Deep capillary plexus telangiectasia and its overlap with ellipsoid zone loss are two promising markers of nonproliferative MacTel, while hyper-reflective foci are markers for proliferative MacTel.

RESOLUTION OF FOVEAL CYST AFTER THE RELEASE OF VITREOMACULAR ATTACHMENT IN EYE WITH MACULAR TELANGIECTASIA TYPE 2.

PURPOSE: To report a case of macular telangiectasia Type 2 that showed a resolution of a foveal cystic change accompanying the release of vitreomacular attachment. METHODS: Retrospective chart review. REPORT OF THE CASE: A 75-year-old man presented with a bilateral decrease in visual acuity and metamorphopsia. At the initial visit, the left eye demonstrated a hyporeflective foveal cyst and a perifoveal vitreous detachment on optical coherence tomography. The characteristic clinical findings were consistent with the diagnosis of macular telangiectasia Type 2. Fifteen months later, the patient returned with a remission of the metamorphopsia in the left eye. The left eye had a vitreous detachment from the macula, and the hyporeflective foveal cyst was completely resolved. CONCLUSION: At least in some cases, vitreous traction or attachment may play a role in the morphologic changes seen in macular telangiectasia Type 2.

SWEPT-SOURCE OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY ASSESSMENT OF FELLOW EYES IN COATS DISEASE.

PURPOSE: To assess foveal and parafoveal vasculature at superficial capillary plexus (SCP), deep capillary plexus, and choriocapillaris using optical coherence tomography angiography in the fellow eyes of patients with Coats disease. METHODS: Observational and prospective case series. Thirteen patients with unilateral Coats and 14 healthy age- and sex-matched controls were consecutively recruited at Manchester Royal Eye Hospital and the Department of Ophthalmology of San Raffaele Hospital. Both groups underwent complete ophthalmologic examination, including optical coherence tomography angiography (Topcon Corp) 3 mm × 3 mm scans. Images were imported into ImageJ software and binarized; foveal avascular zone area was manually outlined and vessel density analyzed in inner (foveal) and outer (parafoveal) areas of SCP, deep capillary plexus, and choriocapillaris. RESULTS: Fellow eyes disclosed a significant increase in the foveal vessel density of SCP (P = 0.04); in particular, superior and temporal quadrants showed more marked alterations (P = 0.02 and 0.04, respectively). Analysis of foveal avascular zone area revealed a significant enlargement in the SCP (P = 0.04). No correlation was found between fellow eyes and the stage of affected eyes. CONCLUSION: Fellow eyes of Coats patients carry quantitative foveal vascular alterations at SCP. These may represent markers of altered inner blood-retinal barrier, due to a bilateral defect in midcapillary angiogenesis.

RETINAL-CHOROIDAL ANASTOMOSIS IN MACULAR TELANGIECTASIA TYPE 2.

PURPOSE: To investigate the deep retinal vascular changes potentially present in macular telangiectasis Type 2 (MacTel 2) with projection resolved optical coherence tomography angiography including volume rendering. METHODS: Retrospective consecutive evaluation of patients with MacTel 2 in a community-based retinal referral practice with a comprehensive ophthalmologic examination to include optical coherence tomography and projection-resolved optical coherence tomography angiography with volume rendering. Main outcome measures were the characterization of vessel presence and anatomical arrangement in the outer retina. RESULTS: There were 26 eyes of 13 patients with a mean age of 64.9 (±11.3) years, and 6 were men. The mean visual acuity was logMAR 0.4 (Snellen equivalent 20/50). No eye had signs of choroidal neovascularization or exudation. Focal hyperpigmentation was seen in 13 (50%) and right-angle veins in 17 (65%) eyes. Retinal-choroidal anastomoses were seen in 17 (65%) eyes. These anastomoses typically occurred in multiple clusters of small vessels. The presence of anastomoses was associated with pigment (P < 0.001), although the anastomoses did not necessarily colocalize with the pigment, and right-angle veins (P < 0.001), which were found in every eye with a retinal-choroidal anastomosis. CONCLUSION: Retinal-choroidal anastomoses were commonly observed in eyes with MacTel 2 using projection-resolved optical coherence tomography angiography. One animal model for MacTel 2 uses very low-density lipoprotein receptor mutant mice and shows multiple retinal-choroidal anastomoses in the disease pathogenesis as well. These findings suggest MacTel 2 is more than just a neurodegenerative disease with secondary vascular abnormalities, as the choroid may be involved in the disease process.

ALK1 Loss Results in Vascular Hyperplasia in Mice and Humans Through PI3K Activation.

OBJECTIVE: ALK1 (activin-receptor like kinase 1) is an endothelial cell-restricted receptor with high affinity for BMP (bone morphogenetic protein) 9 TGF-ß (transforming growth factor-ß) family member. Loss-of-function mutations in ALK1 cause a subtype of hereditary hemorrhagic telangiectasia-a rare disease characterized by vasculature malformations. Therapeutic strategies are aimed at reducing potential complications because of vascular malformations, but currently, there is no curative treatment for hereditary hemorrhagic telangiectasia. APPROACH AND RESULTS: In this work, we report that a reduction in ALK1 gene dosage (heterozygous ALK1+/- mice) results in enhanced retinal endothelial cell proliferation and vascular hyperplasia at the sprouting front. We found that BMP9/ALK1 represses VEGF (vascular endothelial growth factor)-mediated PI3K (phosphatidylinositol 3-kinase) by promoting the activity of the PTEN (phosphatase and tensin homolog). Consequently, loss of ALK1 function in endothelial cells results in increased activity of the PI3K pathway. These results were confirmed in cutaneous telangiectasia biopsies of patients with hereditary hemorrhagic telangiectasia 2, in which we also detected an increase in endothelial cell proliferation linked to an increase on the PI3K pathway. In mice, genetic and pharmacological inhibition of PI3K is sufficient to abolish the vascular hyperplasia of ALK1+/- retinas and in turn normalize the vasculature. CONCLUSIONS: Overall, our results indicate that the BMP9/ALK1 hub critically mediates vascular quiescence by limiting PI3K signaling and suggest that PI3K inhibitors could be used as novel therapeutic agents to treat hereditary hemorrhagic telangiectasia.

Potential Effects of Hormone Therapy in Type 2 Idiopathic Macular Telangiectasia.

PURPOSE: To investigate the influence of hormone therapy with tamoxifen or estrogens on morphological changes in macular telangiectasia (MacTel) type 2 patients as revealed clinically in multiple imaging modalities. METHODS: Patients with a history of tamoxifen or estrogen use were selected from the cohort of the MacTel Study. A race-, age- and best-corrected visual acuity-matched group of MacTel participants not under hormone therapy served as the comparison group. The frequencies of typical features of the MacTel phenotype apparent in color fundus, red-free, fluorescein angiographic and optical coherence tomographic images were graded and analyzed statistically. RESULTS: Thirty-nine MacTel patients were included in the analyses, of whom 13 were receiving tamoxifen, 13 estrogens and 13 patients no hormone treatment. Patients treated with estrogens showed significantly fewer breaks in the ellipsoid zone on optical coherence tomography (7 eyes, 29.1%, vs. tamoxifen: 14 eyes, 53.8%, and vs. controls: 14 eyes, 53.8%, p = 0.04 in both analyses, Fisher exact test). Retinal crystalline deposits were significantly more frequent in patients receiving estrogens (12 eyes, 16.2%, vs. 2 eyes, 2.7%, p = 0.003, Fisher exact test). No significant between-group differences were apparent with regard to other features of the phenotype (extent of retinal low reflective spaces, late hyperfluorescence on fluorescein angiography or retinal thickness). CONCLUSIONS: Tamoxifen treatment does not seem to accentuate structural changes in patients with MacTel type 2. Treatment with estrogens may exhibit a neuroprotective effect as suggested by the decreased frequency of ellipsoid zone breaks in corresponding patients, although corroborative studies are warranted to confirm these exploratory data.

[Inefficacy of aflibercept in the treatment of idiopathic macular telangiectasia type 2 without neovascularization]. / Inefficacité de l'aflibercept dans le traitement des télangiectasies maculaires idiopathiques de type 2 sans néovascularisation.

Idiopathic macular telangectasia type 2 is a rare disease consisting primarily of bilateral macular capillary telangiectasia, alterations of the ellipsoid zone and intraretinal cysts that may appear as cystoid macular edema in the absence of neovascularization. Our goal was to study the efficacy of aflibercept in the treatment of these cysts. Thus, we performed a series of three intravitreal injections of aflibercept in the right eye of a woman with a typical presentation of macular telangectasia type 2 complicated by cystoid macular edema without neovascularization. These injections did not significantly improve the anatomical or functional results. Other studies investigating the efficacy of other anti-VEGF in this disease led mainly to a decrease in macular thickness on OCT after injection, without any functional improvement. The anti-VEGFs therefore appear to be of little value in treating MacTel 2 intraretinal cysts without neovascularization.