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In vivo MRI evaluation of early postnatal development in normal and impaired rat eyes. Sci Rep 2021; 11:15513. [PMID: 34330952 PMCID: PMC8324881 DOI: 10.1038/s41598-021-93991-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/25/2020] [Accepted: 07/01/2021] [Indexed: 11/08/2022] Open
Abstract
This study employed in vivo 7-T magnetic resonance imaging (MRI) to evaluate the postnatal ocular growth patterns under normal development or neonatal impairments in Sprague-Dawley rats. Using T2-weighted imaging on healthy rats from postnatal day (P) 1 (newborn) to P60 (adult), the volumes of the anterior chamber and posterior chamber (ACPC), lens, and vitreous humor increased logistically with ACPC expanding by 33-fold and the others by fivefold. Intravitreal potassium dichromate injection at P1, P7, and P14 led to T1-weighted signal enhancement in the developing retina by 188-289%. Upon unilateral hypoxic-ischemic encephalopathy at P7, monocular deprivation at P15, and monocular enucleation at P1, T2-weighted imaging of the adult rats showed decreased ocular volumes to different extents. In summary, in vivo high-field MRI allows for non-invasive evaluation of early postnatal development in the normal and impaired rat eyes. Chromium-enhanced MRI appeared effective in examining the developing retina before natural eyelid opening at P14 with relevance to lipid metabolism. The reduced ocular volumes upon neonatal visual impairments provided evidence to the emerging problems of why some impaired visual outcomes cannot be solely predicted by neurological assessments and suggested the need to look into both the eye and the brain under such conditions.
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Berkowitz BA, Bissig D, Roberts R. MRI of rod cell compartment-specific function in disease and treatment in vivo. Prog Retin Eye Res 2015; 51:90-106. [PMID: 26344734 DOI: 10.1016/j.preteyeres.2015.09.001] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2015] [Revised: 08/26/2015] [Accepted: 09/01/2015] [Indexed: 10/23/2022]
Abstract
Rod cell oxidative stress is a major pathogenic factor in retinal disease, such as diabetic retinopathy (DR) and retinitis pigmentosa (RP). Personalized, non-destructive, and targeted treatment for these diseases remains elusive since current imaging methods cannot analytically measure treatment efficacy against rod cell compartment-specific oxidative stress in vivo. Over the last decade, novel MRI-based approaches that address this technology gap have been developed. This review summarizes progress in the development of MRI since 2006 that enables earlier evaluation of the impact of disease on rod cell compartment-specific function and the efficacy of anti-oxidant treatment than is currently possible with other methods. Most of the new assays of rod cell compartment-specific function are based on endogenous contrast mechanisms, and this is expected to facilitate their translation into patients with DR and RP, and other oxidative stress-based retinal diseases.
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Affiliation(s)
- Bruce A Berkowitz
- Dept. of Anatomy and Cell Biology, Wayne State University School of Medicine, Detroit, MI, USA; Dept. Of Ophthalmology, Wayne State University School of Medicine, Detroit, MI, USA.
| | - David Bissig
- Dept. of Anatomy and Cell Biology, Wayne State University School of Medicine, Detroit, MI, USA
| | - Robin Roberts
- Dept. Of Ophthalmology, Wayne State University School of Medicine, Detroit, MI, USA
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Berkowitz BA, Gorgis J, Patel A, Baameur F, Gurevich VV, Craft CM, Kefalov VJ, Roberts R. Development of an MRI biomarker sensitive to tetrameric visual arrestin 1 and its reduction via light-evoked translocation in vivo. FASEB J 2014; 29:554-64. [PMID: 25351983 DOI: 10.1096/fj.14-254953] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Rod tetrameric arrestin 1 (tet-ARR1), stored in the outer nuclear layer/inner segments in the dark, modulates photoreceptor synaptic activity; light exposure stimulates a reduction via translocation to the outer segments for terminating G-protein coupled phototransduction signaling. Here, we test the hypothesis that intraretinal spin-lattice relaxation rate in the rotating frame (1/T1ρ), an endogenous MRI contrast mechanism, has high potential for evaluating rod tet-ARR1 and its reduction via translocation. Dark- and light-exposed mice (null for the ARR1 gene, overexpressing ARR1, diabetic, or wild type with or without treatment with Mn2+, a calcium channel probe) were studied using 1/T1ρ MRI. Immunohistochemistry and single-cell recordings of the retinas were also performed. In wild-type mice with or without treatment with Mn2+, 1/T1ρ of avascular outer retina (64% to 72% depth) was significantly (P < 0.05) greater in the dark than in the light; a significant (P < 0.05) but opposite pattern was noted in the inner retina (<50% depth). Light-evoked outer retina Δ1/T1ρ was absent in ARR1-null mice and supernormal in overexpressing mice. In diabetic mice, the outer retinal Δ1/T1ρ pattern suggested normal dark-to-light tet-ARR1 translocation and chromophore content, conclusions confirmed ex vivo. Light-stimulated Δ1/T1ρ in inner retina was linked to changes in blood volume. Our data support 1/T1ρ MRI for noninvasively assessing rod tet-ARR1 and its reduction via protein translocation, which can be combined with other metrics of retinal function in vivo.
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Affiliation(s)
- Bruce A Berkowitz
- Department of Anatomy and Cell Biology and Department of Ophthalmology, Wayne State University, Detroit, Michigan, USA;
| | | | | | - Faiza Baameur
- Department of Pharmacology, Vanderbilt University, Nashville, Tennessee, USA
| | - Vsevolod V Gurevich
- Department of Pharmacology, Vanderbilt University, Nashville, Tennessee, USA
| | - Cheryl M Craft
- Mary D. Allen Laboratory for Vision Research, USC Eye Institute, and Department of Ophthalmology and Department of Cell and Neurobiology, Keck School of Medicine of the University of Southern California, Los Angeles, California, USA; and
| | - Vladimir J Kefalov
- Department of Ophthalmology and Visual Sciences, Washington University in St. Louis, St. Louis, Missouri, USA
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Ramos de Carvalho JE, Verbraak FD, Aalders MC, van Noorden CJ, Schlingemann RO. Recent advances in ophthalmic molecular imaging. Surv Ophthalmol 2013; 59:393-413. [PMID: 24529711 DOI: 10.1016/j.survophthal.2013.09.005] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2012] [Revised: 09/23/2013] [Accepted: 09/24/2013] [Indexed: 12/30/2022]
Abstract
The aim of molecular imaging techniques is the visualization of molecular processes and functional changes in living animals and human patients before morphological changes occur at the cellular and tissue level. Ophthalmic molecular imaging is still in its infancy and has mainly been used in small animals for pre-clinical research. The goal of most of these pre-clinical studies is their translation into ophthalmic molecular imaging techniques in clinical care. We discuss various molecular imaging techniques and their applications in ophthalmology.
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Affiliation(s)
- J Emanuel Ramos de Carvalho
- Ocular Angiogenesis Group, Departments of Ophthalmology and Cell Biology and Histology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands; Department of Ophthalmology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
| | - Frank D Verbraak
- Department of Ophthalmology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
| | - Maurice C Aalders
- Department of Biomedical Engineering and Physics, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
| | - Cornelis J van Noorden
- Ocular Angiogenesis Group, Departments of Ophthalmology and Cell Biology and Histology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
| | - Reinier O Schlingemann
- Ocular Angiogenesis Group, Departments of Ophthalmology and Cell Biology and Histology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands; Department of Ophthalmology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands; Netherlands Institute for Neuroscience, Royal Academy of Sciences, Amsterdam, The Netherlands.
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Berkowitz BA, Bissig D, Dutczak O, Corbett S, North R, Roberts R. MRI biomarkers for evaluation of treatment efficacy in preclinical diabetic retinopathy. ACTA ACUST UNITED AC 2013; 7:393-403. [PMID: 23786440 DOI: 10.1517/17530059.2013.814639] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
INTRODUCTION One sober consequence of the current epidemic of diabetes mellitus is that an increasing number of people world-wide will partially or completely lose their sight to diabetic retinopathy. Clinically, the sight-threatening complications of diabetes are diagnosed and treated based on visible retinal lesions (e.g., dot-blot hemorrhages or retinal neovascularization). However, such anatomical microvascular lesions are slow to respond with treatment. Thus, there remains an urgent need for imaging biomarkers that are abnormal before retinal lesions are visibly apparent and are responsive to treatment. AREAS COVERED Here, the development of new MRI methods, such as manganese-enhanced MRI, for evaluating early diabetes-evoked retinal pathophysiology, and its usefulness in guiding new treatments for diabetic retinopathy are reviewed. EXPERT OPINION In diabetic retinopathy, not all important diagnostic and prognostic needs are well served by optical methods. In the absence of gross anatomy changes, critical times when drug intervention is most likely to be successful at reducing vision loss are missed by most light-based methods and thus provide little help in guiding diagnosis and treatment. For example, before clinical symptoms, is there an optimal time to intervene with drug therapy? Is a drug reaching its target? How does one assess optimal drug dose, schedule, and routes? How well do current experimental models mimic the clinical condition? As discussed herein, MRI is as an analytical tool for addressing these unmet needs. Future clinical applications of MRI can be envisioned such as in clinical trials to assess drug treatment efficacy, or as an adjunct approach to refine or clarify a difficult clinical case. New MRI-generated hypotheses about the pathogenesis of diabetic retinopathy and its treatment are discussed. In the coming years, a substantial growth in the development and application of MRI is expected to address relevant question in both the basic sciences and in the clinic.
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Affiliation(s)
- Bruce A Berkowitz
- Wayne State University, Department of Anatomy and Cell Biology, Detroit, MI, USA.
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Retinal Oxygen Saturation and Metabolism: How does it Pertain to Glaucoma? An Update on the Application of Retinal Oximetry in Glaucoma. Eur J Ophthalmol 2013; 23:465-72. [DOI: 10.5301/ejo.5000289] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/19/2013] [Indexed: 11/20/2022]
Abstract
Purpose To discuss the techniques and mechanisms of retinal oximetry with a focus on utilization of retinal oximetry in the assessment of retinal oxygen saturation in glaucoma. Methods We reviewed recent literature found by searching combinations of the following search terms: glaucoma, retinal oximetry, ocular blood flow, retinal blood flow, oxygen saturation. We also reviewed pertinent references from articles found in this search. Results Retinal oximetry offers the potential for directly assessing oxygen saturation in retinal tissue. This capability can contribute to the knowledge of ocular blood flow and its role in the pathogenesis of glaucoma. Conclusions Recent research has shown that retinal oximetry could become an important clinical tool in glaucoma. However, more research is needed to validate the reliability and reproducibility of retinal oximetry, and to fully deduce its clinical role in ocular diseases.
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Wright WS, Singh Yadav A, McElhatten RM, Harris NR. Retinal blood flow abnormalities following six months of hyperglycemia in the Ins2(Akita) mouse. Exp Eye Res 2012; 98:9-15. [PMID: 22440813 PMCID: PMC3340465 DOI: 10.1016/j.exer.2012.03.003] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2012] [Revised: 02/13/2012] [Accepted: 03/05/2012] [Indexed: 12/30/2022]
Abstract
The aim of this study was to characterize the microvascular flow abnormalities and oxygenation changes that are present following six months of hyperglycemia in the diabetic Ins2(Akita) mouse. Previous studies have shown decreased retinal blood flow in the first several weeks of hyperglycemia in rodents, similar to the decreases seen in the early stages of human diabetes. However, whether this alteration in the mouse retina continues beyond the initial weeks of diabetes has yet to be determined, as are the potential consequences of the decreased flow on retinal oxygenation. In this study, male Ins2(Akita) and age-matched C57BL/6 (non-diabetic) mice were maintained for a period of six months, at which time intravital microscopy was used to measure retinal blood vessel diameters, blood cell velocity, vascular wall shear rates, blood flow rates, and transient capillary occlusions. In addition, the presence of hypoxia was assessed using the oxygen-sensitive probe pimonidazole. The diabetic retinal microvasculature displayed decreases in red blood cell velocity (30%, p<0.001), shear rate (25%, p<0.01), and flow rate (40%, p<0.001). Moreover, transient capillary stoppages in flow were observed in the diabetic mice, but rarely in the non-diabetic mice. However, no alterations were observed in retinal hypoxia as determined by a pimonidazole assay, suggesting the possibility that the decreases seen in retinal blood flow may be dictated by a decrease in retinal oxygen utilization.
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Affiliation(s)
- William S. Wright
- Department of Molecular & Cellular Physiology, Louisiana State University Health Sciences Center, Shreveport, LA 71130
- Division of Natural Sciences and Engineering, University of South Carolina Upstate, Spartanburg, SC 29303
| | - Amit Singh Yadav
- Department of Molecular & Cellular Physiology, Louisiana State University Health Sciences Center, Shreveport, LA 71130
| | - Robert M. McElhatten
- Department of Molecular & Cellular Physiology, Louisiana State University Health Sciences Center, Shreveport, LA 71130
| | - Norman R. Harris
- Department of Molecular & Cellular Physiology, Louisiana State University Health Sciences Center, Shreveport, LA 71130
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Abstract
Glaucoma is the second leading cause of blindness. It affects retinal ganglion cells and the optic nerve. However, there is emerging evidence that glaucoma also affects other components of the visual pathway and visual cortex. There is a need to employ new methods of in vivo brain evaluation to characterize these changes. Magnetic resonance (MR) techniques are well suited for this purpose. We review data on the MR evaluation of the visual pathway and the use of MR techniques in the study of glaucoma, both in humans and in animal models. These studies demonstrated decreases in optic nerve diameter, localized white matter loss and decrease in visual cortex density. Studies on rats employing manganese-enhanced MRI showed that axonal transport in the optic nerve is affected. Diffusion tensor MRI revealed signs of degeneration of the optic pathway. Functional MRI showed decreased response of the visual cortex after stimulation of the glaucomatous eye. Magnetic resonance spectroscopy demonstrated changes in metabolite levels in the visual cortex in a rat model of glaucoma, although not in glaucoma patients. Further applications of MR techniques in studies of glaucomatous brains are indicated.
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Affiliation(s)
- Michal Fiedorowicz
- Department of Experimental Pharmacology, Polish Academy of Science Medical Research Centre, Warsaw, Poland.
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CHAN KEVINC, CHEUNG MATTHEWM, WU EDX. IN VIVOMULTIPARAMETRIC MAGNETIC RESONANCE IMAGING AND SPECTROSCOPY OF RODENT VISUAL SYSTEM. J Integr Neurosci 2010; 9:477-508. [DOI: 10.1142/s0219635210002524] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2010] [Accepted: 11/04/2010] [Indexed: 01/27/2023] Open
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Richdale K, Wassenaar P, Teal Bluestein K, Abduljalil A, Christoforidis JA, Lanz T, Knopp MV, Schmalbrock P. 7 Tesla MR imaging of the human eye in vivo. J Magn Reson Imaging 2010; 30:924-32. [PMID: 19856406 DOI: 10.1002/jmri.21959] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
PURPOSE To develop a protocol which optimizes contrast, resolution and scan time for three-dimensional (3D) imaging of the human eye in vivo using a 7 Tesla (T) scanner and custom radio frequency (RF) coil. MATERIALS AND METHODS Initial testing was conducted to reduce motion and susceptibility artifacts. Three-dimensional FFE and IR-TFE images were obtained with variable flip angles and TI times. T(1) measurements were made and numerical simulations were performed to determine the ideal contrast of certain ocular structures. Studies were performed to optimize resolution and signal-to-noise ratio (SNR) with scan times from 20 s to 5 min. RESULTS Motion and susceptibility artifacts were reduced through careful subject preparation. T(1) values of the ocular structures are in line with previous work at 1.5T. A voxel size of 0.15 x 0.25 x 1.0 mm(3) was obtained with a scan time of approximately 35 s for both 3D FFE and IR-TFE sequences. Multiple images were registered in 3D to produce final SNRs over 40. CONCLUSION Optimization of pulse sequences and avoidance of susceptibility and motion artifacts led to high quality images with spatial resolution and SNR exceeding prior work. Ocular imaging at 7T with a dedicated coil improves the ability to make measurements of the fine structures of the eye.
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Affiliation(s)
- Kathryn Richdale
- The Ohio State University College of Optometry, Columbus, Ohio, USA
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