Quantitative imaging of the clearance systems in the eye and the brain

Deng, Wei; Liu, Crystal; Parra, Carlos; Sims, Jeffrey R.; Faiq, Muneeb A.; Sainulabdeen, Anoop; Song, Hana; Chan, Kevin C.

doi:10.21037/qims.2019.11.18

Cited by 12 publications

(5 citation statements)

References 74 publications

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“…In the retina, homeostasis and metabolism are regulated by Müller cells, a specialized type of retinal glial cell [47]. Similar to the glial cells that form the brain's glymphatic system, Müller cells express AQP-4 on their membranes [48]. The endfeet of the Müller cells not only ensheath the retinal vasculature and optic nerve but also form the inner limiting membrane separating the retina from the vitreous [49].…”

Section: Discussionmentioning

confidence: 99%

Exploring Vitreous Haze as a Potential Biomarker for Accelerated Glymphatic Outflow and Neurodegeneration in Multiple Sclerosis: A Cross-Sectional Study

Kaçar,

Coric,

Ometto

et al. 2023

Brain Sciences

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Background: The glymphatic system removes neurodegenerative debris. The ocular glymphatic outflow is from the eye to the proximal optic nerve. In multiple sclerosis (MS), atrophy of the optic nerve increases the glymphatic outflow space. Here, we tested whether vitreous haze (VH) can provide novel insights into the relationship between neurodegeneration and the ocular glymphatic system in MS. Methods: This cross-sectional study comprised 315 persons with MS and 87 healthy controls (HCs). VH was quantified from optical coherence tomography (OCT) volume scans. Neurodegeneration was determined on three-dimensional T1 (3DT1) MRI, lesion detection on fluid-attenuated inversion (FLAIR), and layer thickness on OCT. Generalized estimating equations, corrected for age, were used to analyze associations between VH and metrics for neurodegeneration, demographics, and clinical scales. Group differences were determined between mild, moderate, and severe disability. Results: On the group level, VH scores were comparable between MS and control (p = 0.629). In MS, VH scores declined with disease duration (β = −0.009, p = 0.004) and age (β = −0.007, p = 0.001). There was no relation between VH scores and higher age in HCs. In MS patients, VH was related to normalized gray (NGMV, β = 0.001, p = 0.011) and white matter volume (NWMV, β = 0.001, p = 0.003), macular ganglion cell–inner plexiform layer thickness (mGCIPL, β = 0.006, p < 0.001), and peripapillary retinal nerve fiber layer thickness (pRNFL, β = 0.004, p = 0.008). VH was significantly lower in severe compared to mild disability (mean difference −28.86%, p = 0.058). Conclusions: There is a correlation between VH on OCT and disease duration, more severe disability and lower brain volumes in MS. Biologically, these relationships suggest accelerated glymphatic clearance with disease-related atrophy.

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Section: Discussionmentioning

confidence: 99%

Exploring Vitreous Haze as a Potential Biomarker for Accelerated Glymphatic Outflow and Neurodegeneration in Multiple Sclerosis: A Cross-Sectional Study

Kaçar,

Coric,

Ometto

et al. 2023

Brain Sciences

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“…Future studies are warranted that use chromium-enhanced MRI in conjunction with visible-light optical coherence tomography to evaluate metabolic retinal development 73 . Prospective multiparametric MRI studies can also be conducted to analyze ocular physiology 10 , 74 , 75 – 78 and determine structure–function relationships 79 – 82 . While the parameters of the current curve fits appear comparable to an ex vivo study on cryosection without fixation 1 , immunohistochemistry can be incorporated after preclinical MRI to study the molecular mechanisms of ocular growth.…”

Section: Discussionmentioning

confidence: 99%

In vivo MRI evaluation of early postnatal development in normal and impaired rat eyes

Kancherla

Hamade

et al. 2021

Sci Rep

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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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“…Based on the evidence acquired through their measurements, the authors also argue that the ICG spectral stabilization process may vary between patients. This is particularly relevant because in vitro studies showed a relatively quick spectral stabilization of the ICG, and multiple authors had previously suggested the ICG concentration could be translated into absolute values of physiological parameters in the assessment of conscious and unconscious TBI patients managed with maximum medical treatment or decompressive craniectomy (20)(21)(22)(23)(24)(25). If the instability of ICG in vivo, as presumed according to this study, were to be confirmed by more in-depth analysis on larger sample sizes, the conclusions from Forcione et al (11) may call into question the capacity to obtain absolute parameters of cerebral blood flow and BBB damage from optical analyses, where the ICG optical properties are considered stable.…”

Section: Editorialmentioning

confidence: 99%

Breakthrough in the assessment of cerebral perfusion and vascular permeability after brain trauma through the adoption of dynamic indocyanine green-enhanced near-infrared spectroscopy

Ganau¹,

Iqbal²,

Ligarotti³

et al. 2020

Quant Imaging Med Surg

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Quantitative imaging of the clearance systems in the eye and the brain

Cited by 12 publications

References 74 publications

Exploring Vitreous Haze as a Potential Biomarker for Accelerated Glymphatic Outflow and Neurodegeneration in Multiple Sclerosis: A Cross-Sectional Study

Exploring Vitreous Haze as a Potential Biomarker for Accelerated Glymphatic Outflow and Neurodegeneration in Multiple Sclerosis: A Cross-Sectional Study

In vivo MRI evaluation of early postnatal development in normal and impaired rat eyes

Breakthrough in the assessment of cerebral perfusion and vascular permeability after brain trauma through the adoption of dynamic indocyanine green-enhanced near-infrared spectroscopy

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