The Role of Osteopontin in Microglia Biology: Current Concepts and Future Perspectives.

The innate immune landscape of the central nervous system (CNS), including the brain and the retina, consists of different myeloid cell populations with distinct tasks to fulfill. Whereas the CNS borders harbor extraparenchymal CNS-associated macrophages whose main duty is to build up a defense against invading pathogens and other damaging factors from the periphery, the resident immune cells of the CNS parenchyma and the retina, microglia, are highly dynamic cells with a plethora of functions during homeostasis and disease. Therefore, microglia are constantly sensing their environment and closely interacting with surrounding cells, which is in part mediated by soluble factors. One of these factors is Osteopontin (OPN), a multifunctional protein that is produced by different cell types in the CNS, including microglia, and is upregulated in neurodegenerative and neuroinflammatory conditions. In this review, we discuss the current literature about the interaction between microglia and OPN in homeostasis and several disease entities, including multiple sclerosis (MS), Alzheimer's and cerebrovascular diseases (AD, CVD), amyotrophic lateral sclerosis (ALS), age-related macular degeneration (AMD) and diabetic retinopathy (DR), in the context of the molecular pathways involved in OPN signaling shaping the function of microglia. As nearly all CNS diseases are characterized by pathological alterations in microglial cells, accompanied by the disturbance of the homeostatic microglia phenotype, the emergence of disease-associated microglia (DAM) states and their interplay with factors shaping the DAM-signature, such as OPN, is of great interest for therapeutical interventions in the future.

The role of interferon regulatory factor 8 for retinal tissue homeostasis and development of choroidal neovascularisation.

BACKGROUND: Microglia cells represent the resident innate immune cells of the retina and are important for retinal development and tissue homeostasis. However, dysfunctional microglia can have a negative impact on the structural and functional integrity of the retina under native and pathological conditions. METHODS: In this study, we examined interferon-regulatory factor 8 (Irf8)-deficient mice to determine the transcriptional profile, morphology, and temporospatial distribution of microglia lacking Irf8 and to explore the effects on retinal development, tissue homeostasis, and formation of choroidal neovascularisation (CNV). RESULTS: Our study shows that Irf8-deficient MG exhibit a considerable loss of microglial signature genes accompanied by a severely altered MG morphology. An in-depth characterisation by fundus photography, fluorescein angiography, optical coherence tomography and electroretinography revealed no major retinal abnormalities during steady state. However, in the laser-induced CNV model, Irf8-deficient microglia showed an increased activity of biological processes critical for inflammation and cell adhesion and a reduced MG cell density near the lesions, which was associated with significantly increased CNV lesion size. CONCLUSIONS: Our results suggest that loss of Irf8 in microglia has negligible effects on retinal homeostasis in the steady state. However, under pathological conditions, Irf8 is crucial for the transformation of resident microglia into a reactive phenotype and thus for the suppression of retinal inflammation and CNV formation.

Genotype-phenotype correlation in von Hippel-Lindau disease.

BACKGROUND/AIMS: Retinal haemangioblastomas (RH) remain a major cause of visual impairment in patients with von Hippel-Lindau (VHL) disease. Identification of genotype-phenotype correlation is an important prerequisite for better management, treatment and prognosis. METHODS: Retrospective, single-centre cohort study of 200 VHL patients. Genetic data and date of onset of RH, central nervous system haemangioblastomas (CNSH), pheochromocytoma/paraganglioma (PPGL), clear cell renal cell carcinoma (ccRCC) and pancreatic neuroendocrine neoplasm (PNEN) were collected. The number and locations of RH were recorded. RESULTS: The first clinical finding occurred at an age of 26 ± 14 years (y) [mean ± SD]. In 91 ± 3% (95% CI 88-94) of the patients, at least one RH occur until the age of 60y. A total of 42 different rare VHL gene variants in 166 patients were detected. A higher age-related incidence of RH, CNSH, ccRCC and PNEN was detected in patients with a truncating variant (TV) compared to patients with a single amino-acid substitution/deletion (AASD) (all p < 0.01), while it is reverse for PPGL (p < 0.01). Patients with a TV showed 0.10 ± 0.15 RH per y during their lifetime compared to 0.05 ± 0.07 in patients with AASD (p < 0.02). The median enucleation/phthisis-free survival time in patients with a TV was 56y (95% CI 50-62) compared to 78y (95% CI 75-81) in patients with AASD (p < 0.02). CONCLUSION: Compared to patients with AASD, patients with a TV develop RH, CNSH, ccRCC and PNEN earlier. They experience a higher number of RH and bear a higher risk of enucleation/phthisis. Thus, patients with a TV might be considered for a more intensive ophthalmological monitoring.

Comparison of Current Optical Coherence Tomography Angiography Methods in Imaging Retinal Hemangioblastomas.

Purpose: To compare spectral-domain (SD) and swept-source (SS) optical coherence tomography angiography (OCTA) for imaging retinal capillary hemangioblastomas (RCHs) in von Hippel-Lindau disease (VHLD). Methods: Prospective single-center cross-sectional study. Tumor size (TS) of perfused RCHs was assessed clinically in relation to the optic disc size. For both technologies, SD-OCTA and SS-OCTA, corresponding images with a scan size of 3 × 3 mm2 and 6 × 6 mm2, respectively, were overlaid according to the set of marker positions to determine the TS. Results: From 200 patients with VHLD, 48 patients showed 84 RCHs. SD-OCTA images of 39 RCHs (46.4%) and SS-OCTA images of 48 RCHs (57.2%) were suitable for analysis. The average in OCTA-measured TS of 1.60 ± 2.58 mm2 (range, 0.01-10.43) was congruent to the clinically assessed TS in 81.3% of cases (r = 0.86, P < 0.0001). TS measured in SD-OCTA compared to SS-OCTA showed similar values and a high correlation (all P < 0.0001). Nevertheless, despite the similarities, a slight trend in SS-OCTA was observed whereby with increasing TS, an elevated TS was detected compared to SD-OCTA (3 × 3-mm2 scans: mean difference of 0.03 ± 0.04  mm2, 6 × 6-mm2 scans: 0.08 ± 0.19 mm2). However, within the same imaging technology method, TS values almost did not differ (SD-OCTA: mean difference of 0.01 ± 0.02 mm2, SS-OCTA: 0.001 ± 0.01 mm2). Conclusions: OCTA may serve as an additional tool for diagnosis and monitoring of RCHs. Nevertheless, due to the differences between the technologies, the values cannot be used interchangeably. Translational Relevance: SD-OCTA and SS-OCTA are suitable to detect and monitor RCHs and provide a more detailed assessment about the TS than this is clinically possible.

[Advanced Training Curriculum at the Eye Center, University of Freiburg]. / Das Curriculum der strukturierten Facharztweiterbildung an der Klinik für Augenheilkunde des Universitätsklinikums Freiburg: ein Erfahrungsbericht.

BACKGROUND AND OBJECTIVE: Since 2006, at the Eye Center, University of Freiburg, an advanced-training curriculum has been used for medical specialists in ophthalmology. This training curriculum was evaluated for the years 2006 until 2017. METHODS: Internal quality management documents were worked through on the subject of training curriculum. Moreover, we analyzed the internet presence of the Eye Center Freiburg as well as its presentation of the training curriculum and the generally accessible annual reports. Furthermore, administrative personnel data were provided. Quantitative analyses were made with Microsoft Excel. RESULTS: A medical specialist's career is organized as follows: 1) Structured application procedure with evaluation through the Head of the Department, the section heads and the resident's representative. 2) Initial training through medical colleagues and a mentor. 3) Rotation through all sections and areas. 4a) Annual appraisal interviews. 4b) Definition of a career pathway after 3 years. 5) Regular participation in internal/external training sessions. 6) Research after 3 months. 7) Possibility of work shadowing in practices in the 5th year. For reconciling of work and family life, parental leave and part-time employment are possible. In the years between 2006 and 2017, the analyzed data show an increasing number of job interviews and employees. All interns reached the specialist qualification in ophthalmology during the investigation period, 48% additionally got the Fellow of the European Board of Ophthalmology (FEBO). CONCLUSIONS: Since 2006, a structured curriculum has existed for the training of medical specialists in ophthalmology at the Eye Center Freiburg. This is well documented on the homepage as well as in the internal quality management manual. The transparency, paired with the quality of the training program, leads to an increasing number of employees as well as the number of employees with specialist medical qualifications. This can be seen as an indicator for a successful curriculum which secures medical care and research.

Impact of angiogenic activation and inhibition on miRNA profiles of human retinal endothelial cells.

BACKGROUND: Human retinal microvascular endothelial cells (HRMVECs) are involved in the pathogenesis of retinopathy of prematurity. In this study, the microRNA (miRNA) expression profiles of HRMVECs were investigated under resting conditions, angiogenic stimulation (VEGF treatment) and anti-VEGF treatment. MATERIALS AND METHODS: The miRNA profiles of HRMVECs under resting and angiogenic conditions (VEGF treatment), as well as after addition of aflibercept, bevacizumab or ranibizumab were evaluated by analyzing the transcriptome of small non-coding RNAs. Differentially expressed miRNAs were validated using qPCR and classified using Gene Ontology enrichment analysis. RESULTS: Ten miRNAs were found to be significantly changed more than 2-fold. Seven of these miRNAs were changed between resting conditions and angiogenic stimulation. Four of these miRNAs (miR-139-5p/-3p and miR-335-5p/-3p) were validated by qPCR in independent experiments and were found to be associated with angiogenesis and cell migration in Gene Ontology analysis. In addition, analysis of the most abundant miRNAs in the HRMVEC miRNome (representing at least 1% of the miRNome) was conducted and identified miR-21-5p, miR-29a-3p, miR-100-5p and miR-126-5p/-3p to be differently expressed by at least 15% between resting conditions and angiogenic conditions. These miRNAs were found to be associated with apoptotic signaling, regulation of kinase activity, intracellular signal transduction, cell surface receptor signaling and positive regulation of cell differentiation in Gene Ontology analysis. No differentially regulated miRNAs between angiogenic stimulation and angiogenic stimulation plus anti-VEGF treatment were identified. CONCLUSION: In this study we characterized the miRNA profile of HRMVECs under resting, angiogenic and anti-angiogenic conditions and identified several miRNAs of potential pathophysiologic importance for angioproliferative retinal diseases. Our results have implications for possible miRNA-targeted angiomodulatory approaches in diseases like diabetic retinopathy or retinopathy of prematurity.

Increased expression of hypoxia-inducible factor-1 alpha and its impact on transcriptional changes and prognosis in malignant tumours of the ocular adnexa.

PURPOSE: To investigate the expression profile of the hypoxia-inducible transcription factor-1α (HIF-1α) and its downstream targets in malignancies of the ocular adnexa and to determine its relevance as a prognostic factor for clinical outcome. METHODS: We included 49 subjects with malignant tumours (25 squamous cell carcinomas (SCC), 15 non-Hodgkin lymphomas, 9 melanomas) and 30 patients with benign tumours of the ocular adnexa (13 papillomas, 7 reactive lymphoid hyperplasias (RLHs) and 10 nevi) as controls. We quantified HIF-1α protein expression by immunohistochemistry and assessed the association between HIF-1α and clinical outcome via Kaplan-Meier analysis. Furthermore, we assessed the expression of HIF-1α downstream factors by transcriptional sequencing using the MACE (massive analysis of cDNA ends) technology. RESULTS: SCCs revealed a strong HIF-1α expression in 61% of tumour cells in comparison with only 22% in papillomas (p < 0.0001). In contrast, malignant melanomas and lymphomas revealed a similar HIF-1α expression compared with nevi and RLHs. Transcriptional sequencing and Gene Ontology Cluster analysis demonstrated 37 hypoxia-associated factors, including HIF-1α, VEGF, SFRP1 and LOXL2 that are significantly increased in SCC and may contribute to tumour proliferation, angiogenesis, and metastasis. Association analysis between HIF-1α immunoreactivity and clinical outcome revealed a trend towards an unfavourable prognosis in malignant tumours with increased HIF-1α expression. CONCLUSIONS: HIF-1α protein is increased in malignant tumours of the ocular adnexa, which is associated with an increase in multiple HIF-1α-downstream factors and a trend towards an unfavourable clinical outcome.

Sema3f Protects Against Subretinal Neovascularization In Vivo.

Pathological neovascularization of the outer retina is the hallmark of neovascular age-related macular degeneration (nAMD). Building on our previous observations that semaphorin 3F (Sema3f) is expressed in the outer retina and demonstrates anti-angiogenic potential, we have investigated whether Sema3f can be used to protect against subretinal neovascularization in two mouse models. Both in the very low-density lipid-receptor knockout (Vldlr-/-) model of spontaneous subretinal neovascularization as well as in the mouse model of laser-induced choroidal neovascularization (CNV), we found protective effects of Sema3f against the formation of pathologic neovascularization. In the Vldlr-/- model, AAV-induced overexpression of Sema3f reduced the size of pathologic neovascularization by 56%. In the laser-induced CNV model, intravitreally injected Sema3f reduced pathologic neovascularization by 30%. Combined, these results provide the first evidence from two distinct in vivo models for a use of Sema3f in protecting the outer retina against subretinal neovascularization.

Value of Optical Coherence Tomography Angiography Imaging in Diagnosis and Treatment of Hemangioblastomas in von Hippel-Lindau Disease.

BACKGROUND AND OBJECTIVE: The introduction of optical coherence tomography angiography (OCTA) provides new insights into the retinal vasculature. The aim of this study was to explore the value of OCTA in imaging retinal hemangioblastomas and monitoring laser treatment in patients with von Hippel-Lindau (VHL) disease. PATIENTS AND METHODS: Ten eyes of 10 patients with VHL disease were included in this retrospective case series. All patients underwent complete ophthalmological work-up including OCTA for retinal and optic nerve head hemangioblastoma. RESULTS: Two patients showed retinal scars and no recurrence of hemangioblastoma in OCTA. Three patients revealed recurrent hemangioblastomas. Two patients demonstrated a new hemangioblastoma. Three patients showed hemangioblastomas of the optic nerve head. Successful laser photocoagulation could be monitored with OCTA. CONCLUSIONS: Screening for retinal hemangioblastomas with OCTA alone is not possible. OCTA may help to distinguish hemangioblastomas and other lesions in VHL disease, especially after treatment and allows the differentiation from harmless non-vascular lesions in questionable cases. [Ophthalmic Surg Lasers Imaging Retina. 2016;47:935-946.].