Modeling Choroideremia Disease with Isogenic Induced Pluripotent Stem Cells.

Choroideremia (CHM) is a rare X-linked chorioretinal dystrophy causing progressive vision loss due to mutations in the CHM gene, leading to Rab escort protein 1 loss of function. CHM disease is characterized by a progressive degeneration of the choroid, the retinal pigment epithelium (RPE), and the retina. The RPE is a monolayer of polarized cells that supports photoreceptors, providing nutrients, growth factors, and ions, and removes retinal metabolism waste products, having a central role in CHM pathogenesis. Commonly used models such as ARPE-19 cells do not reproduce accurately the nature of RPE cells. Human induced pluripotent stem cells (hiPSCs) can be differentiated into RPE cells (hiPSC-RPE), which mimic key features of native RPE, being more suited to study retinal diseases. Therefore, we took advantage of hiPSCs to generate new human-based CHM models. Two isogenic hiPSC lines were generated through CRISPR/Cas9: a CHM knock-out line from a healthy donor and a corrected CHM patient line using a knock-in approach. The differentiated hiPSC-RPE lines exhibited critical morphological and physiological characteristics of native RPE, including the presence of the tight junction markers Claudin-19 and Zonula Occludens-1, phagocytosis of photoreceptor outer segments, pigmentation, a postmitotic state, and the characteristic polygonal shape. In addition, all the studied cells were able to form retinal organoids. This work resulted in the establishment of isogenic hiPSC lines, representing a new and important CHM cellular model. To our knowledge, this is the first time that isogenic cell lines have been developed to model CHM disease, providing a valuable tool for studying the mechanisms at the onset of RPE degeneration.

Identifying Imaging Predictors of Intermediate Age-Related Macular Degeneration Progression.

Purpose: Intermediate age-related macular degeneration (iAMD) is a risk factor for progression to advanced stages, but rates of progression vary between individuals. Predicting individual risk is advantageous for programing timely and effective treatment and for patient stratification into future clinical trials. Methods: We conducted a prospective and noninterventional study following patients with iAMD for 24 months. Optical coherence tomography parameters related with drusen, hyper-reflective foci (HRF), presence of incomplete retinal pigment epithelial and outer retinal atrophy (iRORA) and ellipsoid zone (EZ) status were explored at the baseline. Patients were reclassified at the end of the follow-up period and divided according to their progression. A risk prediction model for progression to late AMD was developed. Results: A total of 135 patients were enrolled in the study and 30.4% developed late disease. A multivariate logistic regression model was created using those optical coherence tomography parameters, further optimized by backward feature elimination. Parameters offering the best fit in prediction progression were presence of iRORA, EZ status, drusen area and presence of HRF. iRORA is the feature that provides a higher probability of developing late AMD (odds ratio, 12.91; P = 0.000), followed by EZ disruption status (odds ratio, 3.54; P = 0.0018). The area under the receiver operating characteristic curve calculated for the testing set was 0.77 (95% confidence interval, 0.56-0.98). Conclusions: The combination of iRORA and EZ disruption constitute a high risk of progression to complete RORA within 2 years. Translational Relevance: We propose a practical and useful model to help clinicians in their daily practice in predicting individual progression to advanced AMD.

Age-Related Changes of the Synucleins Profile in the Mouse Retina.

Alpha-synuclein (aSyn) plays a central role in Parkinson's disease (PD) and has been extensively studied in the brain. This protein is part of the synuclein family, which is also composed of beta-synuclein (bSyn) and gamma-synuclein (gSyn). In addition to its neurotoxic role, synucleins have important functions in the nervous system, modulating synaptic transmission. Synucleins are expressed in the retina, but they have been poorly characterized. However, there is evidence that they are important for visual function and that they can play a role in retinal degeneration. This study aimed to profile synucleins in the retina of naturally aged mice and to correlate their patterns with specific retinal cells. With aging, we observed a decrease in the thickness of specific retinal layers, accompanied by an increase in glial reactivity. Moreover, the aSyn levels decreased, whereas bSyn increased with aging. The colocalization of both proteins was decreased in the inner plexiform layer (IPL) of the aged retina. gSyn presented an age-related decrease at the inner nuclear layer but was not significantly changed in the ganglion cell layer. The synaptic marker synaptophysin was shown to be preferentially colocalized with aSyn in the IPL with aging. At the same time, aSyn was found to exist at the presynaptic endings of bipolar cells and was affected by aging. Overall, this study suggests that physiological aging can be responsible for changes in the retinal tissue, implicating functional alterations that could affect synuclein family function.

Hyperpigmented epiretinal membrane in macular telangiectasia type 2: imaging characteristics and correlation with transretinal pigment migration.

OBJECTIVES: To explore the features of black hyperpigmentation in macular telangiectasia (MacTel) type 2 and correlate these findings with the characteristics of hyperpigmented epiretinal membranes (ERMs) using multimodal imaging. METHODS: A case series of three patients with MacTel type 2 and hyperpigmented ERMs imaged with colour fundus photography, fluorescein angiography (FA), spectral-domain optical coherence tomography (OCT) and swept-source OCT angiography. Registration of different types of imaging was done using ImageJ v1.53f51 (National Institutes of Health, USA). RESULTS: Three female patients with late-stage MacTel type 2 presented with unilateral hyperpigmented ERMs in the absence of peripheral retinal breaks. In one patient, an extensive ERM occurred along with a full-thickness macular hole (FTMH); in 2 patients, smaller ERMs were seen adjacent to superficial retinal veins. Serial imaging demonstrated that transretinal pigment migration preceded epiretinal proliferation of the hyperpigmented ERM towards superficial retinal veins. CONCLUSION: Hyperpigmented ERMs may occur in the late phases of MacTel type 2 following a FTMH or transretinal migration of pigmented cells to the retinal surface. Once on the retinal surface, black pigment cells seem to proliferate centripetally toward superficial retinal veins.

Macular Vascular Imaging and Connectivity Analysis Using High-Resolution Optical Coherence Tomography.

Purpose: To characterize macular blood flow connectivity in vivo using high-resolution optical coherence tomography (HighRes OCT). Methods: Cross-sectional, observational study. Dense (6-µm interscan distance) perifoveal HighRes OCT raster scans were performed on healthy participants. To mitigate the limitations of projection-resolved OCT-angiography, flow and structural data were used to observe the vascular structures of the superficial vascular complex (SVC) and the deep vascular complex. Vascular segmentation and rendering were performed using Imaris 9.5 software. Inflow and outflow patterns were classified according to vascular diameter and branching order from superficial arteries and veins, respectively. Results: Eight eyes from eight participants were included in this analysis, from which 422 inflow and 459 outflow connections were characterized. Arteries had direct arteriolar connections to the SVC (78%) and to the intermediate capillary plexus (ICP, 22%). Deep capillary plexus (DCP) inflow derived from small-diameter vessels succeeding ICP arterioles. The most prevalent outflow pathways coursed through superficial draining venules (74%). DCP draining venules ordinarily merged with ICP draining venules and drained independently of superficial venules in 21% of cases. The morphology of DCP draining venules in structural HighRes OCT is distinct from other vessels crossing the inner nuclear layer and can be used to identify superficial veins. Conclusions: Vascular connectivity analysis supports a hybrid circuitry of blood flow within the human parafoveal macula. Translational Relevance: Characterization of parafoveal macular blood flow connectivity in vivo using a precise segmentation of HighRes OCT is consistent with ground-truth microscopy studies and shows a hybrid circuitry.

Choroidal Vascular Impairment in Intermediate Age-Related Macular Degeneration.

Age-related macular degeneration (AMD) is a multifactorial disease, whose complete pathogenesis is still unclear. Local hemodynamics may play a crucial role in its manifestation and progression. To evaluate choroidal and retinal vascular parameters, a total of 134 eyes were analyzed, 100 with intermediate AMD and 34 age matched healthy controls. 131 eyes of 104 patients were eligible for complete image assessment and 3 eyes were excluded for insufficient image quality: Group 1: intermediate AMD (n = 97) and Group 2: healthy controls (n = 34). Spectral domain optic coherence tomography (SD-OCT) with enhanced depth imaging (EDI) and optic coherence tomography angiography (OCT-A) were acquired using Spectralis (Heidelberg Engineering). Choroid and retinal capillary plexus were evaluated and image binarization was used to obtain quantitative data. Mean age was 77.67 years old (YO) and 67.2% were women. Total subfoveal choroidal area and luminal area were significantly reduced in Group 1 compared with Group 2 (0.88 mm2 and 0.40 mm2 vs. 1.24 mm2 and 0.55 mm2, respectively) (p < 0.05). Regarding choriocapillary flow density, AMD eyes recorded reduced values (34.83%) compared with controls (36.25%) (p < 0.05). Chorioretinal vasculature is impaired in intermediate AMD patients and vascular parameters could be attractive new prognostic biomarkers. Future therapeutic approaches may target this vascular dysfunction and delay disease progression.

Formation of Lipofuscin-Like Autofluorescent Granules in the Retinal Pigment Epithelium Requires Lysosome Dysfunction.

Purpose: We aim to characterize the pathways required for autofluorescent granule (AFG) formation by RPE cells using cultured monolayers. Methods: We fed RPE monolayers in culture with a single pulse of photoreceptor outer segments (POS). After 24 hours the cells started accumulating AFGs that were comparable to lipofuscin in vivo. Using this model, we used a variety of light and electron microscopical techniques, flow cytometry and Western blot to analyze the formation of AFGs. We also generated a mutant RPE line lacking cathepsin D by gene editing. Results: AFGs seem to derive from incompletely digested POS-containing phagosomes and after 3 days are surrounded by a single membrane positive for lysosome markers. We show by various methods that lysosome-phagosome fusion is required for AFG formation, and that impairment of lysosomal pH or catalytic activity, particularly cathepsin D activity, enhances AF accumulation. Conclusions: We conclude that lysosomal dysfunction results in incomplete POS degradation and enhanced AFG accumulation.

Age-Related Macular Degeneration: Pathophysiology, Management, and Future Perspectives.

Among older adults, age-related macular degeneration (AMD) is a prevalent disabling condition that begins as subtle visual disturbances and can progress to permanent loss of central vision. In its late neovascular form, AMD is treatable with inhibitors of vascular endothelial growth factor, the key driver of exudative disease. In the atrophic form, treatment remains elusive. This review addresses the natural history of AMD - through early, intermediate, and advanced disease stages - and concentrates on diagnosis and risk stratification, deficiencies of current treatments, and the promising findings of emerging therapies.

Retinal Progression Biomarkers of Early and Intermediate Age-Related Macular Degeneration.

Early and intermediate AMD patients represent a heterogeneous population with an important but variable risk of progression to more advanced stages of the disease. The five-year progression from early and intermediate AMD to late disease is known to range from 0.4% to 53%. This wide variation explains the particular interest in searching predictive AMD biomarkers. Clinical parameters such as drusen size, presence of pigmentary abnormalities, and fellow eye status were, traditionally, the more important predictive elements. Multimodal retinal assessment (Color Fundus Photography, Optical Coherence Tomography, Optical Coherence Angiography and Fundus Autofluorescence) is providing new and accurate image biomarkers, useful in research and in daily practice. If individual progression risk could be anticipated, then management plans should be adapted accordingly, considering follow-up intervals and therapeutic interventions. Here, we reviewed the most important image progression biomarkers of early and intermediate AMD with relevant interest in clinical practice.

CORRELATION STUDY BETWEEN DRUSEN MORPHOLOGY AND FUNDUS AUTOFLUORESCENCE.

PURPOSE: To correlate drusen morphology and outer retinal status with autofluorescence (AF) imaging in patients with intermediate age-related macular degeneration. METHODS: Drusen type and morphology were analyzed using color fundus photography and spectral-domain optic coherence tomography, whereas fundus AF was used for drusen AF evaluation. Additional structural changes on spectral-domain optic coherence tomography, such as disruption of external limiting membrane, ellipsoid zone, and retinal pigment epithelium/Bruch membrane complex, as well as the presence of choroidal hypertransmission at correspondent locations were also evaluated and correlated with fundus AF findings. Spearman's correlation coefficient was used to analyze the correlation between spectral-domain optic coherence tomography morphological characteristics of drusen and AF appearance of the corresponding drusen. Strength of correlation was calculated (r), and a P value < 0.05 was considered statistically significant. RESULTS: Two hundred and twenty-eight drusen from 53 eyes of 53 patients were analyzed, 130 soft drusen (57.02%) and 98 cuticular drusen (42.98%). Sixty percent of the drusen were isoautofluorescent (n = 136), 35% hyperautofluorescent (n = 80), and 5% hypoautofluorescent (n = 12). We found positive correlation between drusen AF and hyperreflective foci (r = 0.4). Outer retinal layers morphology (external limiting membrane and ellipsoid zone status and hypertransmission) also correlates with autofluorescent findings (r = 0.3). CONCLUSION: Multimodal imaging reveals a broad spectrum of ultrastructural changes, which may reflect different stages in the evolution of drusen. Our results suggest that drusen morphological characteristics and autofluorescent findings are correlated but other factors or cofactors may be involved. The described correlations will help us understand new progression biomarkers of nonexudative age-related macular degeneration.

Neuroprotection or Neurotoxicity of Illicit Drugs on Parkinson's Disease.

Parkinson's Disease (PD) is currently the most rapid growing neurodegenerative disease and over the past generation, its global burden has more than doubled. The onset of PD can arise due to environmental, sporadic or genetic factors. Nevertheless, most PD cases have an unknown etiology. Chemicals, such as the anthropogenic pollutant 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and amphetamine-type stimulants, have been associated with the onset of PD. Conversely, cannabinoids have been associated with the treatment of the symptoms'. PD and medical cannabis is currently under the spotlight, and research to find its benefits on PD is on-going worldwide. However, the described clinical applications and safety of pharmacotherapy with cannabis products are yet to be fully supported by scientific evidence. Furthermore, the novel psychoactive substances are currently a popular alternative to classical drugs of abuse, representing an unknown health hazard for young adults who may develop PD later in their lifetime. This review addresses the neurotoxic and neuroprotective impact of illicit substance consumption in PD, presenting clinical evidence and molecular and cellular mechanisms of this association. This research area is utterly important for contemporary society since illicit drugs' legalization is under discussion which may have consequences both for the onset of PD and for the treatment of its symptoms.

Transfer of extracellular vesicle-microRNA controls germinal center reaction and antibody production.

Intercellular communication orchestrates effective immune responses against disease-causing agents. Extracellular vesicles (EVs) are potent mediators of cell-cell communication. EVs carry bioactive molecules, including microRNAs, which modulate gene expression and function in the recipient cell. Here, we show that formation of cognate primary T-B lymphocyte immune contacts promotes transfer of a very restricted set of T-cell EV-microRNAs (mmu-miR20-a-5p, mmu-miR-25-3p, and mmu-miR-155-3p) to the B cell. Transferred EV-microRNAs target key genes that control B-cell function, including pro-apoptotic BIM and the cell cycle regulator PTEN. EV-microRNAs transferred during T-B cognate interactions also promote survival, proliferation, and antibody class switching. Using mouse chimeras with Rab27KO EV-deficient T cells, we demonstrate that the transfer of small EVs is required for germinal center reaction and antibody production in vivo, revealing a mechanism that controls B-cell responses via the transfer of EV-microRNAs of T-cell origin. These findings also provide mechanistic insight into the Griscelli syndrome, associated with a mutation in the Rab27a gene, and might explain antibody defects observed in this pathogenesis and other immune-related and inflammatory disorders.

The synthetic cannabinoid JWH-018 modulates Saccharomyces cerevisiae energetic metabolism.

Synthetic cannabinoids are a group of novel psychoactive substances with similar properties to Δ9-THC. Among the vast number of synthetic cannabinoids, designed to be tested in clinical trials, JWH-018 was the first novel psychoactive substance found in the recreational drug marketplace. The consumption of JWH-018 shows typical effects of CB1 agonists including sedation, cognitive dysfunction, tachycardia, postural hypotension, dry mouth, ataxia and psychotropic effects, but appeared to be more potent than Δ9-THC. However, studies on human cells have shown that JWH-018 toxicity depends on the cellular line used. Despite these studies, the underlying molecular mechanisms to JWH-018 action has not been clarified yet. To understand the impact of JWH-018 at molecular and cellular level, we used Saccharomyces cerevisiae as a model. The results showed an increase in yeast growth rate in the presence of this synthetic cannabinoid due to an enhancement in the glycolytic flux at expense of a decrease in pentose phosphate pathway, judging by 2D-Gel proteomic analysis, qRT-PCR experiments and ATP measurements. Overall, our results provide insights into molecular mechanisms of JWH-018 action, also indicating that Saccharomyces cerevisiae is a good model to study synthetic cannabinoids.

Identification of novel protein phosphatases as modifiers of alpha-synuclein aggregation in yeast.

Alpha-synuclein (aSyn) is a key player in a group of neurodegenerative diseases commonly known as synucleinopathies. Recent findings indicate phosphorylation in several aSyn residues can modulate its aggregation and subcellular localization, thereby affecting pathological processes. However, the precise molecular mechanisms governing aSyn phosphorylation are still unclear. Recent studies investigated the role of various families of protein kinases, such as the polo-like kinases, G protein-coupled receptor kinases or casein kinases. In contrast, our understanding of the phosphatases involved in the dephosphorylation of aSyn is rather limited. Here, we exploited the unique toolbox of the yeast Saccharomyces cerevisiae in order to identify novel phosphatases capable of modulating aSyn phosphorylation, inclusion formation and toxicity of human aSyn. In summary, given the association between aSyn phosphorylation and pathology in Parkinson's disease and other synucleinopathies, modulation of this post-translational modification may constitute an attractive target for therapeutic intervention.

(Poly)phenol-digested metabolites modulate alpha-synuclein toxicity by regulating proteostasis.

Parkinson's disease (PD) is an age-related neurodegenerative disease associated with the misfolding and aggregation of alpha-synuclein (aSyn). The molecular underpinnings of PD are still obscure, but nutrition may play an important role in the prevention, onset, and disease progression. Dietary (poly)phenols revert and prevent age-related cognitive decline and neurodegeneration in model systems. However, only limited attempts were made to evaluate the impact of digestion on the bioactivities of (poly)phenols and determine their mechanisms of action. This constitutes a challenge for the development of (poly)phenol-based nutritional therapies. Here, we subjected (poly)phenols from Arbutus unedo to in vitro digestion and tested the products in cell models of PD based on the cytotoxicity of aSyn. The (poly)phenol-digested metabolites from A. unedo leaves (LPDMs) effectively counteracted aSyn and H2O2 toxicity in yeast and human cells, improving viability by reducing aSyn aggregation and inducing its clearance. In addition, LPDMs modulated pathways associated with aSyn toxicity, such as oxidative stress, endoplasmic reticulum (ER) stress, mitochondrial impairment, and SIR2 expression. Overall, LPDMs reduced aSyn toxicity, enhanced the efficiency of ER-associated protein degradation by the proteasome and autophagy, and reduced oxidative stress. In total, our study opens novel avenues for the exploitation of (poly)phenols in nutrition and health.

Yeast models of Parkinson's disease-associated molecular pathologies.

The aging of the human population is resulting in an increase in the number of people afflicted by neurodegenerative disorders such as Parkinson's disease (PD), creating tremendous socio-economic challenges. This requires the urgent for the development of effective therapies, and of tools for early diagnosis of the disease. However, our understanding of the molecular mechanisms underlying PD pathogenesis is still incomplete, hampering progress in those areas. In recent years, the progression made in genetics has considerably contributed to our knowledge, by identifying several novel PD genes. Furthermore, many cellular and animal models have proven their value to decipher pathways involved in PD development. In this review we highlight the value of the yeast Saccharomyces cerevisiae as a model for PD. This unicellular eukaryote has contributed to our understanding of the cellular mechanisms targeted by most important PD genes and offers an excellent tool for discovering novel players via powerful and informative high throughput screens that accelerate further validation in more complex models.

The effects of the novel A53E alpha-synuclein mutation on its oligomerization and aggregation.

α-synuclein (aSyn) is associated with both sporadic and familial forms of Parkinson's disease (PD), the second most common neurodegenerative disorder after Alzheimer's disease. In particular, multiplications and point mutations in the gene encoding for aSyn cause familial forms of PD. Moreover, the accumulation of aSyn in Lewy Bodies and Lewy neurites in disorders such as PD, dementia with Lewy bodies, or multiple system atrophy, suggests aSyn misfolding and aggregation plays an important role in these disorders, collectively known as synucleinopathies. The exact function of aSyn remains unclear, but it is known to be associated with vesicles and membranes, and to have an impact on important cellular functions such as intracellular trafficking and protein degradation systems, leading to cellular pathologies that can be readily studied in cell-based models. Thus, understanding the molecular effects of aSyn point mutations may provide important insight into the molecular mechanisms underlying disease onset.We investigated the effect of the recently identified A53E aSyn mutation. Combining in vitro studies with studies in cell models, we found that this mutation reduces aSyn aggregation and increases proteasome activity, altering normal proteostasis.We observed that, in our experimental paradigms, the A53E mutation affects specific steps of the aggregation process of aSyn and different cellular processes, providing novel ideas about the molecular mechanisms involved in synucleinopathies.

Analysis of Protein Oligomeric Species by Sucrose Gradients.

Protein misfolding, aggregation, and accumulation are a common hallmark in various neurodegenerative diseases. Invariably, the process of protein aggregation is associated with both a loss of the normal biological function of the protein and a gain of toxic function that ultimately leads to cell death. The precise origin of protein cytotoxicity is presently unclear but the predominant theory posits that smaller oligomeric species are more toxic than larger aggregated forms. While there is still no consensus on this subject, this is a central question that needs to be addressed in order to enable the design of novel and more effective therapeutic strategies. Accordingly, the development and utilization of approaches that allow the biochemical characterization of the formed oligomeric species in a given cellular or animal model will enable the correlation with cytotoxicity and other parameters of interest.Here, we provide a detailed description of a low-cost protocol for the analysis of protein oligomeric species from both yeast and mammalian cell lines models, based on their separation according to sedimentation velocity using high-speed centrifugation in sucrose gradients. This approach is an adaptation of existing protocols that enabled us to overcome existing technical issues and obtain reliable results that are instrumental for the characterization of the types of protein aggregates formed by different proteins of interest in the context of neurodegenerative disorders.

Yeast reveals similar molecular mechanisms underlying alpha- and beta-synuclein toxicity.

Synucleins belong to a family of intrinsically unstructured proteins that includes alpha-synuclein (aSyn), beta-synuclein (bSyn) and gamma-synuclein (gSyn). aSyn is the most studied member of the synuclein family due to its central role in genetic and sporadic forms of Parkinson's disease and other neurodegenerative disorders known as synucleionopathies. In contrast, bSyn and gSyn have been less studied, but recent reports also suggest that, unexpectedly, these proteins may also cause neurotoxicity. Here, we explored the yeast toolbox to investigate the cellular effects of bSyn and gSyn. We found that bSyn is toxic and forms cytosolic inclusions that are similar to those formed by aSyn. Moreover, we found that bSyn shares similar toxicity mechanisms with aSyn, including vesicular trafficking impairment and induction of oxidative stress. We demonstrate that co-expression of aSyn and bSyn exacerbates cytotoxicity, due to increased dosage of toxic synuclein forms, and that they are able to form heterodimers in both yeast and in human cells. In contrast, gSyn is not toxic and does not form inclusions in yeast cells. Altogether, our findings shed light into the question of whether bSyn can exert toxic effects and confirms the occurrence of aSyn/bSyn heterodimers, opening novel perspectives for the development of novel strategies for therapeutic intervention in synucleinopathies.