Imaging of brain barrier inflammation and brain fluid drainage in human neurological diseases

Advances in neuroimaging of multiple sclerosis

PURPOSE OF REVIEW

To summarize recent advancements in understanding multiple sclerosis (MS) pathophysiology, predicting disease course, and monitoring treatment responses using MRI.

RECENT FINDINGS

Paramagnetic rim lesions (PRLs) are highly specific to MS and clinically relevant. Detected from the earliest disease phases, PRLs aid in distinguishing MS from other conditions, improving diagnostic accuracy. Moreover, PRLs are associated with more severe disability and measures of brain damage and may predict disease progression. Similarly, slowly expanding lesions (SELs) are associated with more severe disability and predict a more severe disease course. Disease-modifying therapies have limited effectiveness in reducing PRLs or SELs. Choroid plexus (CP) enlargement is associated with structural brain damage and clinical disability and predicts disease evolution. Enlarged perivascular spaces (ePVS) suggest microangiopathic changes rather than direct MS-related inflammation. Glymphatic dysfunction, evaluated using diffusion tensor image analysis along the perivascular space, emerges early in MS and correlates with disability, cognitive impairment, and structural brain damage. Aging and comorbidities exacerbate MS-related damage, complicating diagnosis and treatment. Emerging technologies, such as brain-age paradigms, aim to disentangle aging from MS-specific neurodegeneration.

SUMMARY

Advances in MRI have highlighted the clinical significance of chronic inflammation and glymphatic dysfunction as early contributors to MS progression as well as the interplay between aging, comorbidities and MS.

The optic nerve in spaceflight: novel concepts in the pathogenesis of optic disc edema in microgravity

PURPOSE OF REVIEW

Spaceflight-associated neuro-ocular syndrome (SANS) encompasses a unique constellation of neuro-ocular findings in astronauts, including optic disc edema (ODE), globe flattening, chorioretinal folds, and hyperopic refractive shift. Although there are numerous neuro-ocular findings in SANS, the purpose of this review is to describe the novel, emerging concepts of the pathogenesis for the ODE specifically in SANS.

RECENT FINDINGS

While the initial hypotheses on the pathogenesis of ODE in SANS focused on possible elevated intracranial pressures (i.e., papilledema), the most prominent current hypothesis is microgravity-induced cephalad fluid shift. More recent studies however suggest that the pathogenesis of the ODE in SANS is likely multifactorial including possible underlying metabolic and genetic components.

SUMMARY

We review the literature on ODE in SANS including recent work integrating the complex physiologic interactions of microgravity-induced disruption in intracerebral and intraocular fluid dynamics, vascular congestion, cellular stress responses, and genetic predisposition. We believe that the development of ODE in SANS is likely multifactorial in origin, and further understanding of the mechanical, cellular, metabolic, and genetic components is of utmost importance to develop future countermeasures in preparation for possible future crewed missions to the moon, the asteroid belt, and Mars.

Choroid Plexus as a Mediator of CNS Inflammation in Multiple Sclerosis

The pathophysiology of multiple sclerosis (MS) remains poorly understood despite decades of tremendous research efforts. Advances in neuroradiography coupled with availability of unbiased approaches including spatial transcriptomics, proteomics, metabolomics, and lipidomics that are compatible with brain and fluid specimens from patients raise hope that discovery of novel disease drivers is on the horizon. Once thought to be little more than salty bathwater, our modern understanding of cerebrospinal fluid (CSF) suggests the CSF as a compelling, critical regulator of brain function in health and disease. Recent studies in the field have reinvigorated interest in CSF as a medium to better understand MS and to deliver disease-modifying therapies. In turn, the choroid plexus, an epithelial tissue located within each brain ventricle that regulates CSF and forms a key blood-CSF barrier, is uniquely positioned to orchestrate neuroinflammation associated with MS. In this perspective review, we will discuss what is known about the choroid plexus as a conductor of immune responses and how it may propagate neuroinflammation associated with MS via the CSF.

The association between slow-wave sleep and choroid plexus calcifications in older adults. Results from the sleep disorders substudy of the Atahualpa Project cohort

OBJECTIVE

It has been suggested that choroid plexus calcifications (CPC) may be associated with glymphatic system dysfunction and with disturbed slow-wave (N3) sleep. If this is the case, volumetric analysis of CPC could be used to estimate the functional ability of the glymphatic system. However, data on this association is limited. This study aims to assess the association between percentages of N3 sleep - used as a putative marker of glymphatic system activity - and the volume of CPC in older adults.

PATIENTS AND METHODS

Community-dwelling individuals aged ≥60 years enrolled in the Atahualpa Project Cohort received head CTs (for automated determinations of CPC volume) and a single-night polysomnography (PSG) for quantification of N3 sleep percentages. Multivariate linear regression and non-parametric models were fitted to assess the association between these variables.

RESULTS

A total of 125 older adults (median age: 65 years; 32 % males) were included. The mean percentage of N3 sleep was 12.4±9.1 %, and the mean volume of CPC was 655±345.3 µL. Non-parametric locally weighted scatterplot smoothing showed that the volume of CPC increased as the percentage of N3 sleep increased, but only when N3 sleep is reduced (up to 12 % of total sleep time). The significance disappeared when PSG parameters were included in the model as well as in participants with normal N3 sleep percentages.

CONCLUSIONS

Study results suggest that in the presence of severe reductions in N3 sleep, increased CPC volume may be a manifestation of choroid plexus compensation or adaptation, and not necessarily dysfunction.

Novel human iPSC models of neuroinflammation in neurodegenerative disease and regenerative medicine

The importance of neuroinflammation in neurodegenerative diseases is becoming increasingly evident, and, in parallel, human induced pluripotent stem cell (hiPSC) models of physiology and pathology are emerging. Here, we review new advancements in the differentiation of hiPSCs into glial, neural, and blood-brain barrier (BBB) cell types, and the integration of these cells into complex organoids and chimeras. These advancements are relevant for modeling neuroinflammation in the context of prevalent neurodegenerative disorders, such as Alzheimer's disease (AD), Parkinson's disease (PD), and multiple sclerosis (MS). With awareness of current limitations, recent progress in the development and application of various hiPSC-derived models shows potential for aiding the identification of candidate therapeutic targets and immunotherapy approaches.