scholarly journals Retinoid isomerase inhibitors impair but do not block mammalian cone photoreceptor function

2018 ◽  
Vol 150 (4) ◽  
pp. 571-590 ◽  
Author(s):  
Philip D. Kiser ◽  
Jianye Zhang ◽  
Aditya Sharma ◽  
Juan M. Angueyra ◽  
Alexander V. Kolesnikov ◽  
...  
Keyword(s):  
Animal Models ◽  
Ex Vivo ◽  
Pigment Epithelium ◽  
Light Sensitivity ◽  
Ground Squirrels ◽  
Slow Phase ◽  
Acute Administration ◽  
Visual Cycle ◽  
Cone Photoreceptors

Visual function in vertebrates critically depends on the continuous regeneration of visual pigments in rod and cone photoreceptors. RPE65 is a well-established retinoid isomerase in the pigment epithelium that regenerates rhodopsin during the rod visual cycle; however, its contribution to the regeneration of cone pigments remains obscure. In this study, we use potent and selective RPE65 inhibitors in rod- and cone-dominant animal models to discern the role of this enzyme in cone-mediated vision. We confirm that retinylamine and emixustat-family compounds selectively inhibit RPE65 over DES1, the putative retinoid isomerase of the intraretinal visual cycle. In vivo and ex vivo electroretinography experiments in Gnat1−/− mice demonstrate that acute administration of RPE65 inhibitors after a bleach suppresses the late, slow phase of cone dark adaptation without affecting the initial rapid portion, which reflects intraretinal visual cycle function. Acute administration of these compounds does not affect the light sensitivity of cone photoreceptors in mice during extended exposure to background light, but does slow all phases of subsequent dark recovery. We also show that cone function is only partially suppressed in cone-dominant ground squirrels and wild-type mice by multiday administration of an RPE65 inhibitor despite profound blockade of RPE65 activity. Complementary experiments in these animal models using the DES1 inhibitor fenretinide show more modest effects on cone recovery. Collectively, these studies demonstrate a role for continuous RPE65 activity in mammalian cone pigment regeneration and provide further evidence for RPE65-independent regeneration mechanisms.

scholarly journals Cone photoreceptor reflectance variation in the northern tree shrew and thirteen-lined ground squirrel

2021 ◽  
pp. 153537022110295
Author(s):  
Mina Gaffney ◽  
Robert F Cooper ◽  
Jenna A Cava ◽  
Hannah M Follett ◽  
Alexander E Salmon ◽  
...  
Keyword(s):  
Animal Models ◽  
Adaptive Optics ◽  
Ground Squirrel ◽  
Light Propagation ◽  
Ex Vivo ◽  
Tree Shrew ◽  
Theoretical Models ◽  
Cone Photoreceptors ◽  
Cone Structure

In vivo images of human cone photoreceptors have been shown to vary in their reflectance both spatially and temporally. While it is generally accepted that the unique anatomy and physiology of the photoreceptors themselves drives this behavior, the exact mechanisms have not been fully elucidated as most studies on these phenomena have been limited to the human retina. Unlike humans, animal models offer the ability to experimentally manipulate the retina and perform direct in vivo and ex vivo comparisons. The thirteen-lined ground squirrel and northern tree shrew are two emerging animal models being used in vision research. Both models feature cone-dominant retinas, overcoming a key limitation of traditional rodent models. Additionally, each possesses unique but well-documented anatomical differences in cone structure compared to human cones, which can be leveraged to further constrain theoretical models of light propagation within photoreceptors. Here we sought to characterize the spatial and temporal reflectance behavior of cones in these species. Adaptive optics scanning light ophthalmoscopy (AOSLO) was used to non-invasively image the photoreceptors of both species at 5 to 10 min intervals over the span of 18 to 25 min. The reflectance of individual cone photoreceptors was measured over time, and images at individual time points were used to assess the variability of cone reflectance across the cone mosaic. Variability in spatial and temporal photoreceptor reflectance was observed in both species, with similar behavior to that seen in human AOSLO images. Despite the unique cone structure in these animals, these data suggest a common origin of photoreceptor reflectance behavior across species. Such data may help constrain models of the cellular origins of photoreceptor reflectance signals. These animal models provide an experimental platform to further explore the morphological origins of light capture and propagation.

scholarly journals Shedding new light on the generation of the visual chromophore

2020 ◽  
Vol 117 (33) ◽  
pp. 19629-19638 ◽  
Author(s):  
Krzysztof Palczewski ◽  
Philip D. Kiser
Keyword(s):  
Pigment Epithelium ◽  
Retinal Pigment ◽  
Visual Pigments ◽  
Visual Cycle ◽  
Cone Photoreceptors ◽  
The Face ◽  
A Cell ◽  
Regeneration Pathway ◽  
Continuous Rod

The visual phototransduction cascade begins with acis–transphotoisomerization of a retinylidene chromophore associated with the visual pigments of rod and cone photoreceptors. Visual opsins release their all-trans-retinal chromophore following photoactivation, which necessitates the existence of pathways that produce 11-cis-retinal for continued formation of visual pigments and sustained vision. Proteins in the retinal pigment epithelium (RPE), a cell layer adjacent to the photoreceptor outer segments, form the well-established “dark” regeneration pathway known as the classical visual cycle. This pathway is sufficient to maintain continuous rod function and support cone photoreceptors as well although its throughput has to be augmented by additional mechanism(s) to maintain pigment levels in the face of high rates of photon capture. Recent studies indicate that the classical visual cycle works together with light-dependent processes in both the RPE and neural retina to ensure adequate 11-cis-retinal production under natural illuminances that can span ten orders of magnitude. Further elucidation of the interplay between these complementary systems is fundamental to understanding how cone-mediated vision is sustained in vivo. Here, we describe recent advances in understanding how 11-cis-retinal is synthesized via light-dependent mechanisms.

scholarly journals Long-Term Oral Treatment with Non-Hypoglycemic Dose of Glibenclamide Reduces Diabetic Retinopathy Damage in the Goto-KakizakiRat Model

Pharmaceutics ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 1095
Author(s):  
Marianne Berdugo ◽  
Kimberley Delaunay ◽  
Cécile Lebon ◽  
Marie-Christine Naud ◽  
Lolita Radet ◽  
...  
Keyword(s):  
Diabetic Retinopathy ◽  
Vision Loss ◽  
Ex Vivo ◽  
Pigment Epithelium ◽  
Oral Treatment ◽  
Retinal Pigment ◽  
Retinal Function ◽  
Acute Administration ◽  
One Year

Diabetic retinopathy (DR) remains a major cause of vision loss, due to macular edema, retinal ischemia and death of retinal neurons. We previously demonstrated that acute administration of glibenclamide into the vitreous, or given orally at a non-hypoglycemic dose, protected the structure and the function of the retina in three animal models that each mimic aspects of diabetic retinopathy in humans. In this pilot study, we investigated whether one year of chronic oral glibenclamide, in a non-hypoglycemic regimen (Amglidia®, 0.4 mg/kg, Ammtek/Nordic Pharma, 5 d/week), could alleviate the retinopathy that develops in the Goto-Kakizaki (GK) rat. In vivo, retinal function was assessed by electroretinography (ERG), retinal thickness by optical coherence tomography (OCT) and retinal perfusion by fluorescein and indocyanin green angiographies. The integrity of the retinal pigment epithelium (RPE) that constitutes the outer retinal barrier was evaluated by quantitative analysis of the RPE morphology on flat-mounted fundus ex vivo. Oral glibenclamide did not significantly reduce the Hb1Ac levels but still improved retinal function, as witnessed by the reduction in scotopic implicit times, limited diabetes-induced neuroretinal thickening and the extension of ischemic areas, and it improved the capillary coverage. These results indicate that low doses of oral glibenclamide could still be beneficial for the prevention of type 2 diabetic retinopathy. Whether the retinas ofpatients treated specifically with glibenclamideare less at risk of developing diabetic complications remains to be demonstrated.

scholarly journals Ocular Toxoplasmosis: Mechanisms of Retinal Infection and Experimental Models

Parasitologia ◽  
2021 ◽  
Vol 1 (2) ◽  
pp. 50-60
Author(s):  
Veronica Rodriguez Fernandez ◽  
Giovanni Casini ◽  
Fabrizio Bruschi
Keyword(s):  
Ex Vivo ◽  
Cell Damage ◽  
Pigment Epithelium ◽  
Retinal Pigment ◽  
Treatment Strategies ◽  
Experimental Models ◽  
Ocular Toxoplasmosis ◽  
Cell Infection

Ocular toxoplasmosis (OT) is caused by the parasite Toxoplasma gondii and affects many individuals throughout the world. Infection may occur through congenital or acquired routes. The parasites enter the blood circulation and reach both the retina and the retinal pigment epithelium, where they may cause cell damage and cell death. Different routes of access are used by T. gondii to reach the retina through the retinal endothelium: by transmission inside leukocytes, as free parasites through a paracellular route, or after endothelial cell infection. A main feature of OT is the induction of an important inflammatory state, and the course of infection has been shown to be influenced by the host immunogenetics. On the other hand, there is evidence that the T. gondii phenotype also has an impact on the distribution of the pathology in different areas. Although considerable knowledge has been acquired on OT, a deeper knowledge of its mechanisms is necessary to provide new, more targeted treatment strategies. In particular, in addition to in vitro and in vivo experimental models, organotypic, ex vivo retinal explants may be useful in this direction.

scholarly journals An Ex Vivo Vessel Injury Model to Study Remodeling

2018 ◽  
Vol 27 (9) ◽  
pp. 1375-1389 ◽  
Author(s):  
Mehmet H. Kural ◽  
Guohao Dai ◽  
Laura E. Niklason ◽  
Liqiong Gui
Keyword(s):  
Shear Stress ◽  
Animal Models ◽  
Intimal Hyperplasia ◽  
Vascular Remodeling ◽  
Ex Vivo ◽  
Vessel Injury ◽  
Injury Model ◽  
Human Arteries

Objective: Invasive coronary interventions can fail due to intimal hyperplasia and restenosis. Endothelial cell (EC) seeding to the vessel lumen, accelerating re-endothelialization, or local release of mTOR pathway inhibitors have helped reduce intimal hyperplasia after vessel injury. While animal models are powerful tools, they are complex and expensive, and not always reflective of human physiology. Therefore, we developed an in vitro 3D vascular model validating previous in vivo animal models and utilizing isolated human arteries to study vascular remodeling after injury. Approach: We utilized a bioreactor that enables the control of intramural pressure and shear stress in vessel conduits to investigate the vascular response in both rat and human arteries to intraluminal injury. Results: Culturing rat aorta segments in vitro, we show that vigorous removal of luminal ECs results in vessel injury, causing medial proliferation by Day-4 and neointima formation, with the observation of SCA1+ cells (stem cell antigen-1) in the intima by Day-7, in the absence of flow. Conversely, when endothelial-denuded rat aortae and human umbilical arteries were subjected to arterial shear stress, pre-seeding with human umbilical ECs decreased the number and proliferation of smooth muscle cell (SMC) significantly in the media of both rat and human vessels. Conclusion: Our bioreactor system provides a novel platform for correlating ex vivo findings with vascular outcomes in vivo. The present in vitro human arterial injury model can be helpful in the study of EC-SMC interactions and vascular remodeling, by allowing for the separation of mechanical, cellular, and soluble factors.

scholarly journals Consequences of mitral valve prolapse on chordal tension: Ex vivo and in vivo studies in large animal models

2011 ◽  
Vol 142 (6) ◽  
pp. 1585-1587 ◽  
Author(s):  
Mathieu Granier ◽  
Morten O. Jensen ◽  
Jesper L. Honge ◽  
Alain Bel ◽  
Philippe Menasché ◽  
...  
Keyword(s):  
Mitral Valve ◽  
Animal Models ◽  
Mitral Valve Prolapse ◽  
Ex Vivo ◽  
In Vivo Studies ◽  
Large Animal ◽  
Large Animal Models

Transduodenal–transpapillary endopancreatic surgery with a rigid resectoscope: experiments on ex vivo, in vivo animal models and human cadavers

2017 ◽  
Vol 31 (10) ◽  
pp. 4131-4135 ◽  
Author(s):  
Philip C. Müller ◽  
Daniel C. Steinemann ◽  
Felix Nickel ◽  
Lukas Chinczewski ◽  
Beat P. Müller-Stich ◽  
...  
Keyword(s):  
Animal Models ◽  
Ex Vivo ◽  
Human Cadavers ◽  
In Vivo Animal Models

scholarly journals PEDF-Rpsa-Itga6 signaling regulates cortical neuronal morphogenesis

2020 ◽  
Author(s):  
Sara M. Blazejewski ◽  
Sarah A. Bennison ◽  
Ngoc T. Ha ◽  
Xiaonan Liu ◽  
Trevor H. Smith ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Neurodevelopmental Disorders ◽  
Ex Vivo ◽  
Pigment Epithelium ◽  
Apical Dendrite ◽  
Integrin Subunit ◽  
Spine Density ◽  
Neuronal Morphogenesis ◽  
Morphological Defects

AbstractNeuromorphological defects underlie neurodevelopmental disorders and functional defects. We identified a function for ribosomal protein SA (Rpsa) in regulating neuromorphogenesis using in utero electroporation to knockdown Rpsa, which results in apical dendrite misorientation, fewer/shorter extensions with decreased arborization, and decreased spine density with altered spine morphology. We investigated Rpsa’s ligand, pigment epithelium-derived factor (PEDF), and interacting partner on the plasma membrane, Integrin subunit α6 (Itga6). Rpsa, PEDF, and Itga6 knockdown cause similar phenotypes, with Rpsa and Itga6 overexpression rescuing morphological defects in PEDF deficient neurons in vivo. Additionally, Itga6 overexpression increases and stabilizes Rpsa expression on the plasma membrane by preventing ubiquitination of Rpsa. GCaMP6s was used to functionally analyze Rpsa knockdown via ex vivo calcium imaging. Rpsa deficient neurons showed less fluctuation in fluorescence intensity, suggesting defective sub-threshold calcium signaling. Our study identifies a role for PEDF-Rpsa-Itga6 signaling in neuromorphogenesis, thus implicating these molecules in the etiology of neurodevelopmental disorders and identifying them as potential therapeutic candidates.

scholarly journals Neuronal Replacement in Stem Cell Therapy for Stroke: Filling the Gap

2021 ◽  
Vol 9 ◽  
Author(s):  
Sara Palma-Tortosa ◽  
Berta Coll-San Martin ◽  
Zaal Kokaia ◽  
Daniel Tornero
Keyword(s):  
Stem Cell ◽  
Animal Models ◽  
Cell Therapy ◽  
Human Skin ◽  
Stem Cell Therapy ◽  
Ex Vivo ◽  
Functional Integration ◽  
Short Review ◽  
Neuronal Replacement

Stem cell therapy using human skin-derived neural precursors holds much promise for the treatment of stroke patients. Two main mechanisms have been proposed to give rise to the improved recovery in animal models of stroke after transplantation of these cells. First, the so called by-stander effect, which could modulate the environment during early phases after brain tissue damage, resulting in moderate improvements in the outcome of the insult. Second, the neuronal replacement and functional integration of grafted cells into the impaired brain circuitry, which will result in optimum long-term structural and functional repair. Recently developed sophisticated research tools like optogenetic control of neuronal activity and rabies virus monosynaptic tracing, among others, have made it possible to provide solid evidence about the functional integration of grafted cells and its contribution to improved recovery in animal models of brain damage. Moreover, previous clinical trials in patients with Parkinson’s Disease represent a proof of principle that stem cell-based neuronal replacement could work in humans. Our studies with in vivo and ex vivo transplantation of human skin-derived cells neurons in animal model of stroke and organotypic cultures of adult human cortex, respectively, also support the hypothesis that human somatic cells reprogrammed into neurons can get integrated in the human lesioned neuronal circuitry. In the present short review, we summarized our data and recent studies from other groups supporting the above hypothesis and opening new avenues for development of the future clinical applications.

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