Iron is a sensitive biomarker for inflammation in multiple sclerosis lesions

Cerebral iron accumulation in multiple sclerosis: Pathophysiology and therapeutic implications

Multiple sclerosis (MS) is a chronic autoimmune disorder of the central nervous system characterized by demyelination, neuroinflammation, and neurodegeneration. Recent studies highlight the role of cerebral iron (Fe) accumulation in exacerbating MS pathophysiology. Fe, essential for neural function, contributes to oxidative stress and inflammation when dysregulated, particularly in the brain's gray matter and demyelinated lesions. Advanced imaging techniques, including susceptibility-weighted and quantitative susceptibility mapping, have revealed abnormal Fe deposition patterns in MS patients, suggesting its involvement in disease progression. Iron's interaction with immune cells, such as microglia, releases pro-inflammatory cytokines, further amplifying neuroinflammation and neuronal damage. These findings implicate Fe dysregulation as a significant factor in MS progression, contributing to clinical manifestations like cognitive impairment. Therapeutic strategies targeting Fe metabolism, including Fe chelation therapies, show promise in reducing Fe-related damage, instilling optimism about the future of MS treatment. However, challenges such as crossing the blood-brain barrier and maintaining Fe homeostasis remain. Emerging approaches, such as Fe-targeted nanotherapeutics and biologics, offer new possibilities for personalized treatments. However, the journey is far from over. Continued research into the molecular mechanisms of Fe-induced neuroinflammation and oxidative damage is essential. Through this research, we can develop effective interventions that could slow MS progression and improve patient outcomes.

Decoding Brain Development and Aging: Pioneering Insights From MRI Techniques

ABSTRACT

The aging process induces a variety of changes in the brain detectable by magnetic resonance imaging (MRI). These changes include alterations in brain volume, fluid-attenuated inversion recovery (FLAIR) white matter hyperintense lesions, and variations in tissue properties such as relaxivity, myelin, iron content, neurite density, and other microstructures. Each MRI technique offers unique insights into the structural and compositional changes occurring in the brain due to normal aging or neurodegenerative diseases. Age-related brain volume changes encompass a decrease in gray matter and an increase in ventricular volume, associated with cognitive decline. White matter hyperintensities, detected by FLAIR, are common and linked to cognitive impairments and increased risk of stroke and dementia. Tissue relaxometry reveals age-related changes in relaxivity, aiding the distinction between normal aging and pathological conditions. Myelin content, measurable by MRI, changes with age and is associated with cognitive and motor function alterations. Iron accumulation, detected by susceptibility-sensitive MRI, increases in certain brain regions with age, potentially contributing to neurodegenerative processes. Diffusion MRI provides detailed insights into microstructural changes such as neurite density and orientation. Neurofluid imaging, using techniques like gadolinium-based contrast agents and diffusion MRI, reveals age-related changes in cerebrospinal and interstitial fluid dynamics, crucial for brain health and waste clearance. This review offers a comprehensive overview of age-related brain changes revealed by various MRI techniques. Understanding these changes helps differentiate between normal aging and pathological conditions, aiding the development of interventions to mitigate age-related cognitive decline and other symptoms. Recent advances in machine learning and artificial intelligence have enabled novel methods for estimating brain age, offering also potential biomarkers for neurological and psychiatric disorders.

Ferritinophagy promotes microglia ferroptosis to aggravate neuroinflammation induced by cerebral ischemia-reperfusion injury via activation of the cGAS-STING signaling pathway

Cerebral ischemia-reperfusion injury (CIRI) is a common and serious complication of reperfusion therapy in patients with ischemic stroke (IS). The regulation of microglia-mediated neuroinflammation to control CIRI has garnered considerable attention. The balance of iron metabolism is key to maintaining the physiological functions of microglia. Nuclear Receptor Coactivator 4 (NCOA4)-mediated ferritinophagy, an important pathway in regulating iron metabolism, is a promising intervention target. However, studies on the impacts of ferritinophagy on microglia-mediated neuroinflammation are lacking. This study aimed to identify potential treatments for CIRI-induced neuroinflammation by focusing on ferritinophagy and the specific mechanisms whereby iron metabolism regulates microglia-mediated neuroinflammation. CIRI induced the activation of ferritinophagy in microglia, characterized by the upregulation of NCOA4, downregulation of Ferritin Heavy Chain 1 (FTH1), and increased intracellular iron levels. This activation contributes to increased ferroptosis, oxidative stress, and the release of inflammatory factors. Silencing NCOA4 or application of the ferroptosis-specific inhibitor Ferrostatin-1 (Fer-1) effectively suppressed the CIRI-induced damage in vivo and in vitro. While Fer-1 addition did not inhibit the CIRI-activated ferritinophagy, it did partially reverse the alleviation of NCOA4 depletion-induced neuroinflammation, suggesting that ferroptosis is an essential intermediate step in ferritinophagy-induced neuroinflammatory damage. Furthermore, using IS-related transcriptomic data, the cGAS-STING pathway was identified as a crucial mechanism connecting ferritinophagy and ferroptosis. Specific inhibition of the cGAS-STING pathway reduced ferritinophagy-induced ferroptosis and neuroinflammation. In summary, our results indicated that ferritinophagy activates the cGAS-STING signaling pathway, which promotes the inflammatory response and oxidative stress in microglia in a ferroptosis-dependent manner, thereby exacerbating CIRI-induced neuroinflammation. These findings provide theoretical support for the clinical treatment of CIRI.

Association of iron deposition in MS lesion with remyelination capacity using susceptibility source separation MRI

OBJECTIVES

Susceptibility source-separation (χ-separation) MRI provides in-vivo proxy of myelin (diamagnetic susceptibility, χdia) and iron concentrations (paramagnetic susceptibility, χpara) in the central nervous system, potentially uncovering myelin- and iron-related pathology in multiple sclerosis (MS) lesions (e.g., demyelination, remyelination, and iron-laden microglia/macrophages formation). This study aims to monitor longitudinal changes in χpara and χdia signals within MS lesions using χ-separation and evaluate the association between lesional iron and remyelination capability.

METHODS

Fifty participants with MS (pwMS) were followed annually over a mean period of 3.3 years (SD = 1.8 years) with MRI, including χ-separation, and clinical assessments. To monitor lesions from their early stage (lesion age < 1 year), we identified newly-noted lesions (NNLs) and contrast-enhancing lesions (CELs), and tracked their longitudinal changes in χpara and χdia signals.

RESULTS

Twenty-three pwMS were detected with NNLs and/or CELs (38 NNLs, 31 CELs;7 overlapped). Among these lesions (62 lesions in total), 27 exhibited χpara hyperintensity, termed hyper-paramagnetic sign (HPS), indicating iron deposition "throughout" the lesion (not confined to rim sign). Early-stage HPS correlated with future remyelination failure detected by χdia myelin signals (P < 0.001). After adjustment, lesions with early HPS demonstrated an annual loss in myelin signal (-1.94 ppb/year), whereas those without early HPS exhibited annual recovery (+0.66 ppb/year). Participants with confirmed disability improvement (CDI) had fewer HPS-positive lesions at baseline than those without CDI (P < 0.001).

CONCLUSION

The presence of HPS is associated with impaired remyelination capacity and a lack of disease improvement in pwMS. Identifying HPS may help demarcate lesions more amenable to myelin repair therapies.

Quantitative susceptibility mapping is more sensitive and specific than phase imaging in detecting chronic active multiple sclerosis lesion rims: pathological validation

Quantitative susceptibility mapping and phase imaging are used to identify multiple sclerosis lesions with paramagnetic rims that slowly expand over time and are associated with earlier progression to disability, decreased brain volume and increased frequency of clinical relapse. However, the presence of iron-laden microglia/macrophages at the lesion rim and demyelination within the lesion both contribute to phase and quantitative susceptibility mapping images. Therefore, simultaneous pathological validation is needed to assess accuracies in identifying iron-positive lesions. MRI was performed on 15 multiple sclerosis brain slabs; 32 lesions of interest were processed for myelin, iron and microglial markers. Three experienced readers classified lesions as rim positive or negative on quantitative susceptibility mapping and phase; these classifications were compared with Perls' stain as the gold standard. All 10 of the quantitative susceptibility mapping-positive lesions had iron-positive rims on histology. Of the 16 phase-positive lesions, only 10 had iron-positive rims on histology. Using Perls' stain as the ground truth, the positive predictive value was 100% for quantitative susceptibility mapping and 63% for phase; the negative predictive value was 95% for quantitative susceptibility mapping and 94% for phase. Post-mortem imaging results demonstrate that quantitative susceptibility mapping is a more reliable indicator of an iron-positive rim compared with phase imaging.

Ferritin loss in astrocytes reduces spinal cord oxidative stress and demyelination in the experimental autoimmune encephalomyelitis (EAE) model

Demyelinating diseases such as multiple sclerosis (MS) cause myelin degradation and oligodendrocyte death, resulting in the release of toxic iron and iron-induced oxidative stress. Astrocytes have a large capacity for iron transport and storage, however the role of astrocytic iron homeostasis in demyelinating disorders is not completely understood. Here we investigate whether astrocytic iron metabolism modulates neuroinflammation, oligodendrocyte survival, and oxidative stress following demyelination. To this aim, we conditionally knock out ferritin in astrocytes and induce experimental autoimmune encephalomyelitis (EAE), an autoimmune-mediated model of demyelination. Ferritin ablation in astrocytes reduced the severity of disease in both the acute and chronic phases. The day of onset, peak disease severity, and cumulative clinical score were all significantly reduced in ferritin KO animals. This corresponded to better performance on the rotarod and increased mobility in ferritin KO mice. Furthermore, the spinal cord of ferritin KO mice display decreased numbers of reactive astrocytes, activated microglia, and infiltrating lymphocytes. Correspondingly, the size of demyelinated lesions, iron accumulation, and oxidative stress were attenuated in the CNS of ferritin KO subjects, particularly in white matter regions of the spinal cord. Thus, deleting ferritin in astrocytes reduced neuroinflammation, oxidative stress, and myelin deterioration in EAE animals. Collectively, these findings suggest that iron storage in astrocytes is a potential therapeutic target to lessen CNS inflammation and myelin loss in autoimmune demyelinating diseases.

Should We Consider Neurodegeneration by Itself or in a Triangulation with Neuroinflammation and Demyelination? The Example of Multiple Sclerosis and Beyond

Neurodegeneration is preeminent in many neurological diseases, and still a major burden we fail to manage in patient's care. Its pathogenesis is complicated, intricate, and far from being completely understood. Taking multiple sclerosis as an example, we propose that neurodegeneration is neither a cause nor a consequence by itself. Mitochondrial dysfunction, leading to energy deficiency and ion imbalance, plays a key role in neurodegeneration, and is partly caused by the oxidative stress generated by microglia and astrocytes. Nodal and paranodal disruption, with or without myelin alteration, is further involved. Myelin loss exposes the axons directly to the inflammatory and oxidative environment. Moreover, oligodendrocytes provide a singular metabolic and trophic support to axons, but do not emerge unscathed from the pathological events, by primary myelin defects and cell apoptosis or secondary to neuroinflammation or axonal damage. Hereby, trophic failure might be an overlooked contributor to neurodegeneration. Thus, a complex interplay between neuroinflammation, demyelination, and neurodegeneration, wherein each is primarily and secondarily involved, might offer a more comprehensive understanding of the pathogenesis and help establishing novel therapeutic strategies for many neurological diseases and beyond.

Fueling neurodegeneration: metabolic insights into microglia functions

Microglia, the resident immune cells of the central nervous system, emerge in the brain during early embryonic development and persist throughout life. They play essential roles in brain homeostasis, and their dysfunction contributes to neuroinflammation and the progression of neurodegenerative diseases. Recent studies have uncovered an intricate relationship between microglia functions and metabolic processes, offering fresh perspectives on disease mechanisms and possible treatments. Despite these advancements, there are still significant gaps in our understanding of how metabolic dysregulation affects microglial phenotypes in these disorders. This review aims to address these gaps, laying the groundwork for future research on the topic. We specifically examine how metabolic shifts in microglia, such as the transition from oxidative phosphorylation and mitochondrial metabolism to heightened glycolysis during proinflammatory states, impact the disease progression in Alzheimer's disease, multiple sclerosis, Parkinson's disease, amyotrophic lateral sclerosis, and Huntington's disease. Additionally, we explore the role of iron, fatty and amino acid metabolism in microglial homeostasis and repair. Identifying both distinct and shared metabolic adaptations in microglia across neurodegenerative diseases could reveal common therapeutic targets and provide a deeper understanding of disease-specific mechanisms underlying multiple CNS disorders.

Prognostic significance of paramagnetic rim lesions in multiple sclerosis: A systematic review

The diagnostic potential of paramagnetic rim lesions (PRLs) has been previously established; however, the prognostic significance of these lesions has not previously been consistently described. This study aimed to establish the prognostic role of PRLs in MS with respect to the Expanded Disability Status Scale (EDSS) and rates of disability progression. Databases of PubMed, EMBASE, Scopus and reference lists of selected articles were searched up to 29/04/2023. The review was conducted in accordance with PRISMA guidelines and was registered prospectively on PROSPERO (CRD42023422052). 7 studies were included in the final review. All of the eligible studies found that patients with PRLs tend to have higher baseline EDSS scores. Longitudinal assessments revealed greater EDSS progression in patients with PRLs over time in most studies. However, the effect of location of PRLs within the central nervous system were not assessed across the studies. Only one study investigated progression independent of relapse activity (PIRA) and showed that this clinical entity occurred in a greater proportion in patients with PRLs. This review supports PRLs as a predictor of EDSS progression. This measure has widespread applicability, however further multicentre studies are needed. Future research should explore the impact of PRLs on silent disability, PIRA, take into account different MS phenotypes and the topography of PRLs in prognosis.

Investigating the relationship between thalamic iron concentration and disease severity in secondary progressive multiple sclerosis using quantitative susceptibility mapping: Cross-sectional analysis from the MS-STAT2 randomised controlled trial

Background

Deep grey matter pathology is a key driver of disability worsening in people with multiple sclerosis. Quantitative susceptibility mapping (QSM) is an advanced magnetic resonance imaging (MRI) technique which quantifies local magnetic susceptibility from variations in phase produced by changes in the local magnetic field. In the deep grey matter, susceptibility has previously been validated against tissue iron concentration. However, it currently remains unknown whether susceptibility is abnormal in older progressive MS cohorts, and whether it correlates with disability.

Objectives

To investigate differences in mean regional susceptibility in deep grey matter between people with secondary progressive multiple sclerosis (SPMS) and healthy controls; to examine in patients the relationships between deep grey matter susceptibility and clinical and imaging measures of disease severity.

Methods

Baseline data from a subgroup of the MS-STAT2 trial (simvastatin vs. placebo in SPMS, NCT03387670) were included. The subgroup underwent clinical assessments and an advanced MRI protocol at 3T. A cohort of age-matched healthy controls underwent the same MRI protocol. Susceptibility maps were reconstructed using a robust QSM pipeline from multi-echo 3D gradient-echo sequence. Regions of interest (ROIs) in the thalamus, globus pallidus and putamen were segmented from 3D T1-weighted images, and lesions segmented from 3D fluid-attenuated inversion recovery images. Linear regression was used to compare susceptibility from ROIs between patients and controls, adjusting for age and sex. Where significant differences were found, we further examined the associations between ROI susceptibility and clinical and imaging measures of MS severity.

Results

149 SPMS (77% female; mean age: 53 yrs; median Expanded Disability Status Scale (EDSS): 6.0 [interquartile range 4.5-6.0]) and 33 controls (52% female, mean age: 57) were included.Thalamic susceptibility was significantly lower in SPMS compared to controls: mean (SD) 28.6 (12.8) parts per billion (ppb) in SPMS vs. 39.2 (12.7) ppb in controls; regression coefficient: -12.0 [95% confidence interval: -17.0 to -7.1], p < 0.001. In contrast, globus pallidus and putamen susceptibility were similar between both groups.In SPMS, a 10 ppb lower thalamic susceptibility was associated with a +0.13 [+0.01 to +0.24] point higher EDSS (p < 0.05), a -2.4 [-3.8 to -1.0] point lower symbol digit modality test (SDMT, p = 0.001), and a -2.4 [-3.7 to -1.1] point lower Sloan low contrast acuity, 2.5% (p < 0.01).Lower thalamic susceptibility was also strongly associated with a higher T2 lesion volume (T2LV, p < 0.001) and lower normalised whole brain, deep grey matter and thalamic volumes (all p < 0.001).

Conclusions

The reduced thalamic susceptibility found in SPMS compared to controls suggests that thalamic iron concentrations are lower at this advanced stage of the disease. The observed relationships between lower thalamic susceptibility and more severe physical, cognitive and visual disability suggests that reductions in thalamic iron may correlate with important mechanisms of clinical disease progression. Such mechanisms appear to intimately link reductions in thalamic iron with higher T2LV and the development of thalamic atrophy, encouraging further research into QSM-derived thalamic susceptibility as a biomarker of disease severity in SPMS.

The relation between BTK expression and iron accumulation of myeloid cells in multiple sclerosis

Activation of Bruton's tyrosine kinase (BTK) has been shown to play a crucial role in the proinflammatory response of B cells and myeloid cells upon engagement with B cell, Fc, Toll-like receptor, and distinct chemokine receptors. Previous reports suggest BTK actively contributes to the pathogenesis of multiple sclerosis (MS). The BTK inhibitor Evobrutinib has been shown to reduce the numbers of gadolinium-enhancing lesions and relapses in relapsing-remitting MS patients. In vitro, BTK inhibition resulted in reduced phagocytic activity and modulated BTK-dependent inflammatory signaling of microglia and macrophages. Here, we investigated the protein expression of BTK and CD68 as well as iron accumulation in postmortem control (n = 10) and MS (n = 23) brain tissue, focusing on microglia and macrophages. MS cases encompassed active, chronic active, and inactive lesions. BTK+ and iron+ cells positively correlated across all regions of interests and, along with CD68, revealed highest numbers in the center of active and at the rim of chronic active lesions. We then studied the effect of BTK inhibition in the human immortalized microglia-like HMC3 cell line in vitro. In particular, we loaded HMC3 cells with iron-dextran and subsequently administered the BTK inhibitor Evobrutinib. Iron treatment alone induced a proinflammatory phenotype and increased the expression of iron importers as well as the intracellular iron storage protein ferritin light chain (FTL). BTK inhibition of iron-laden cells dampened the expression of microglia-related inflammatory genes as well as iron-importers, whereas the iron-exporter ferroportin was upregulated. Our data suggest that BTK inhibition not only dampens the proinflammatory response but also reduces iron import and storage in activated microglia and macrophages with possible implications on microglial iron accumulation in chronic active lesions in MS.

Central Vein Sign and Paramagnetic Rim Lesions: Susceptibility Changes in Brain Tissues and Their Implications for the Study of Multiple Sclerosis Pathology

Multiple sclerosis (MS) is the most common acquired inflammatory and demyelinating disease in adults. The conventional diagnostic of MS and the follow-up of inflammatory activity is based on the detection of hyperintense foci in T2 and fluid-attenuated inversion recovery (FLAIR) magnetic resonance imaging (MRI) and lesions with brain-blood barrier (BBB) disruption in the central nervous system (CNS) parenchyma. However, T2/FLAIR hyperintense lesions are not specific to MS and the MS pathology and inflammatory processes go far beyond focal lesions and can be independent of BBB disruption. MRI techniques based on the magnetic susceptibility properties of the tissue, such as T2*, susceptibility-weighted images (SWI), and quantitative susceptibility mapping (QSM) offer tools for advanced MS diagnostic, follow-up, and the assessment of more detailed features of MS dynamic pathology. Susceptibility-weighted techniques are sensitive to the paramagnetic components of biological tissues, such as deoxyhemoglobin. This capability enables the visualization of brain parenchymal veins. Consequently, it presents an opportunity to identify veins within the core of multiple sclerosis (MS) lesions, thereby affirming their venocentric characteristics. This advancement significantly enhances the accuracy of the differential diagnostic process. Another important paramagnetic component in biological tissues is iron. In MS, the dynamic trafficking of iron between different cells, such as oligodendrocytes, astrocytes, and microglia, enables the study of different stages of demyelination and remyelination. Furthermore, the accumulation of iron in activated microglia serves as an indicator of latent inflammatory activity in chronic MS lesions, termed paramagnetic rim lesions (PRLs). PRLs have been correlated with disease progression and degenerative processes, underscoring their significance in MS pathology. This review will elucidate the underlying physical principles of magnetic susceptibility and their implications for the formation and interpretation of T2*, SWI, and QSM sequences. Additionally, it will explore their applications in multiple sclerosis (MS), particularly in detecting the central vein sign (CVS) and PRLs, and assessing iron metabolism. Furthermore, the review will discuss their role in advancing early and precise MS diagnosis and prognostic evaluation, as well as their utility in studying chronic active inflammation and degenerative processes.

Targeting epidermal growth factor receptor and its downstream signaling pathways by natural products: A mechanistic insight

The epidermal growth factor receptor (EGFR) is a transmembrane receptor tyrosine kinase (RTK) that maintains normal tissues and cell signaling pathways. EGFR is overactivated and overexpressed in many malignancies, including breast, lung, pancreatic, and kidney. Further, the EGFR gene mutations and protein overexpression activate downstream signaling pathways in cancerous cells, stimulating the growth, survival, resistance to apoptosis, and progression of tumors. Anti-EGFR therapy is the potential approach for treating malignancies and has demonstrated clinical success in treating specific cancers. The recent report suggests most of the clinically used EGFR tyrosine kinase inhibitors developed resistance to the cancer cells. This perspective provides a brief overview of EGFR and its implications in cancer. We have summarized natural products-derived anticancer compounds with the mechanistic basis of tumor inhibition via the EGFR pathway. We propose that developing natural lead molecules into new anticancer agents has a bright future after clinical investigation.

An update on the role of magnetic resonance imaging in predicting and monitoring multiple sclerosis progression

INTRODUCTION

While magnetic resonance imaging (MRI) is established in diagnosing and monitoring disease activity in multiple sclerosis (MS), its utility in predicting and monitoring disease progression is less clear.

AREAS COVERED

The authors consider changing concepts in the phenotypic classification of MS, including progression independent of relapses; pathological processes underpinning progression; advances in MRI measures to assess them; how well MRI features explain and predict clinical outcomes, including models that assess disease effects on neural networks, and the potential role for machine learning.

EXPERT OPINION

Relapsing-remitting and progressive MS have evolved from being viewed as mutually exclusive to having considerable overlap. Progression is likely the consequence of several pathological elements, each important in building more holistic prognostic models beyond conventional phenotypes. MRI is well placed to assess pathogenic processes underpinning progression, but we need to bridge the gap between MRI measures and clinical outcomes. Mapping pathological effects on specific neural networks may help and machine learning methods may be able to optimize predictive markers while identifying new, or previously overlooked, clinically relevant features. The ever-increasing ability to measure features on MRI raises the dilemma of what to measure and when, and the challenge of translating research methods into clinically useable tools.

Susceptibility-based imaging aids accurate distinction of pediatric-onset MS from myelin oligodendrocyte glycoprotein antibody-associated disease

BACKGROUND

Myelin oligodendrocyte glycoprotein (MOG) antibody-associated disease (MOGAD) and pediatric-onset multiple sclerosis (POMS) share clinical and magnetic resonance imaging (MRI) features but differ in prognosis and management. Early POMS diagnosis is essential to avoid disability accumulation. Central vein sign (CVS), paramagnetic rim lesions (PRLs), and central core lesions (CCLs) are susceptibility-based imaging (SbI)-related signs understudied in pediatric populations that may help discerning POMS from MOGAD.

METHODS

T2-FLAIR and SbI (three-dimensional echoplanar imaging (3D-EPI)/susceptibility-weighted imaging (SWI) or similar) were acquired on 1.5T/3T scanners. Two readers assessed CVS-positive rate (%CVS+), and their average score was used to build a receiver operator curve (ROC) assessing the ability to discriminate disease type. PRLs and CCLs were identified using a consensual approach.

RESULTS

The %CVS+ distinguished 26 POMS cases (mean age 13.7 years, 63% females, median EDSS 1.5) from 14 MOGAD cases (10.8 years, 35% females, EDSS 1.0) with ROC = 1, p < 0.0001, (cutoff 41%). PRLs were only detectable in POMS participants (mean 2.1±2.3, range 1-10), discriminating the two conditions with a sensitivity of 69% and a specificity of 100%. CCLs were more sensitive (81%) but less specific (71.43%).

CONCLUSION

The %CVS+ and PRLs are highly specific markers of POMS. After proper validation on larger multicenter cohorts, consideration should be given to including such imaging markers for diagnosing POMS at disease onset.

Myeloid cell iron uptake pathways and paramagnetic rim formation in multiple sclerosis

In multiple sclerosis (MS), sustained inflammatory activity can be visualized by iron-sensitive magnetic resonance imaging (MRI) at the edges of chronic lesions. These paramagnetic rim lesions (PRLs) are associated with clinical worsening, although the cell type-specific and molecular pathways of iron uptake and metabolism are not well known. We studied two postmortem cohorts: an exploratory formalin-fixed paraffin-embedded (FFPE) tissue cohort of 18 controls and 24 MS cases and a confirmatory snap-frozen cohort of 6 controls and 14 MS cases. Besides myelin and non-heme iron imaging, the haptoglobin-hemoglobin scavenger receptor CD163, the iron-metabolizing markers HMOX1 and HAMP as well as immune-related markers P2RY12, CD68, C1QA and IL10 were visualized in myeloid cell (MC) subtypes at RNA and protein levels across different MS lesion areas. In addition, we studied PRLs in vivo in a cohort of 98 people with MS (pwMS) via iron-sensitive 3 T MRI and haptoglobin genotyping by PCR. CSF samples were available from 38 pwMS for soluble CD163 (sCD163) protein level measurements by ELISA. In postmortem tissues, we observed that iron uptake was linked to rim-associated C1QA-expressing MC subtypes, characterized by upregulation of CD163, HMOX1, HAMP and, conversely, downregulation of P2RY12. We found that pwMS with [Formula: see text] 4 PRLs had higher sCD163 levels in the CSF than pwMS with [Formula: see text] 3 PRLs with sCD163 correlating with the number of PRLs. The number of PRLs was associated with clinical worsening but not with age, sex or haptoglobin genotype of pwMS. However, pwMS with Hp2-1/Hp2-2 haplotypes had higher clinical disability scores than pwMS with Hp1-1. In summary, we observed upregulation of the CD163-HMOX1-HAMP axis in MC subtypes at chronic active lesion rims, suggesting haptoglobin-bound hemoglobin but not transferrin-bound iron as a critical source for MC-associated iron uptake in MS. The correlation of CSF-associated sCD163 with PRL counts in MS highlights the relevance of CD163-mediated iron uptake via haptoglobin-bound hemoglobin. Also, while Hp haplotypes had no noticeable influence on PRL counts, pwMS carriers of a Hp2 allele might have a higher risk to experience clinical worsening.

Dysregulation of humoral immunity, iron homeostasis, and lipid metabolism is associated with multiple sclerosis progression

BACKGROUND

Though most patients with multiple sclerosis (MS) presented earlier on as a relapsing-remitting (RR) disease, disability progression eventually occurred. Uncovering the mechanisms underlying progression may facilitate the unmet need for developing therapies to prevent progression. Benign MS (BMS), a rare form of MS, is the opposite from secondary progressive MS (SPMS) in that it lacks disease progression defined as Expanded Disability Status Scale (EDSS) ≤3 after at least 15 years of disease onset. BMS is characterized by rare and mild relapses with complete remission of clinical symptoms (lower activity of the disease) and lack of progression. Our study aims to identify transcriptomic and immunological differences between BMS and SPMS to unravel the pathogenesis of disease progression.

METHODS

We took multi-modal approaches with microarrays, flow cytometry, and lipidomics by three-way comparisons of patients with BMS vs. RRMS (low disease activity vs. moderate or severe activity), RRMS vs. SPMS (continued activity vs. complete transformation into progressive phase) as well as BMS vs. SPMS, matched for age and disease-duration (low disease activity and no progression vs. progression with or without activity).

RESULTS

We found that patients with RRMS and SPMS have a significantly higher percentage of B cells than those with BMS. BMS shows a different transcriptomic profile than SPMS. Many of the differentially expressed genes (DEGs) are involved in B cell-mediated immune responses. Additionally, long-chain fatty acids (LCFA), which can act as inflammatory mediators, are also altered in SPMS. Overall, our data suggest a role for the dysregulation of B cell differentiation and function, humoral immunity, and iron and lipid homeostasis in the pathogenesis of MS disease progression.

CONCLUSION

BMS has a unique transcriptomic and immunological profile compared to RRMS and SPMS. These differences will allow for personalized precision medicine and may ultimately lead to the discovery of new therapeutic targets for disease progression.

Iron in multiple sclerosis - Neuropathology, immunology, and real-world considerations

Iron is an essential element involved in a multitude of bodily processes. It is tightly regulated, as elevated deposition in tissues is associated with diseases such as multiple sclerosis (MS). Iron accumulation in the central nervous system (CNS) of MS patients is linked to neurotoxicity through mechanisms including oxidative stress, glutamate excitotoxicity, misfolding of proteins, and ferroptosis. In the past decade, the combination of MRI and histopathology has enhanced our understanding of iron deposition in MS pathophysiology, including in the pro-inflammatory and neurotoxicity of iron-laden rims of chronic active lesions. In this regard, iron accumulation may not only have an impact on different CNS-resident cells but may also promote the innate and adaptive immune dysfunctions in MS. Although there are discordant results, most studies indicate lower levels of iron but higher amounts of the iron storage molecule ferritin in the circulation of people with MS. Considering the importance of iron, there is a need for evidence-guided recommendation for dietary intake in people living with MS. Potential novel therapeutic approaches include the regulation of iron levels using next generation iron chelators, as well as therapies to interfere with toxic consequences of iron overload including antioxidants in MS.

Ferroptosis in Neurological Disease

Iron accumulation in the CNS occurs in many neurological disorders. It can contribute to neuropathology as iron is a redox-active metal that can generate free radicals. The reasons for the iron buildup in these conditions are varied and depend on which aspects of iron influx, efflux, or sequestration that help maintain iron homeostasis are dysregulated. Iron was shown recently to induce cell death and damage via lipid peroxidation under conditions in which there is deficient glutathione-dependent antioxidant defense. This form of cell death is called ferroptosis. Iron chelation has had limited success in the treatment of neurological disease. There is therefore much interest in ferroptosis as it potentially offers new drugs that could be more effective in reducing iron-mediated lipid peroxidation within the lipid-rich environment of the CNS. In this review, we focus on the molecular mechanisms that induce ferroptosis. We also address how iron enters and leaves the CNS, as well as the evidence for ferroptosis in several neurological disorders. Finally, we highlight biomarkers of ferroptosis and potential therapeutic strategies.

Neurodegeneration and its potential markers in the diagnosing of secondary progressive multiple sclerosis. A review

Approximately 70% of relapsing-remitting multiple sclerosis (RRMS) patients will develop secondary progressive multiple sclerosis (SPMS) within 10-15 years. This progression is characterized by a gradual decline in neurological functionality and increasing limitations of daily activities. Growing evidence suggests that both inflammation and neurodegeneration are associated with various pathological processes throughout the development of MS; therefore, to delay disease progression, it is critical to initiate disease-modifying therapy as soon as it is diagnosed. Currently, a diagnosis of SPMS requires a retrospective assessment of physical disability exacerbation, usually over the previous 6-12 months, which results in a delay of up to 3 years. Hence, there is a need to identify reliable and objective biomarkers for predicting and defining SPMS conversion. This review presents current knowledge of such biomarkers in the context of neurodegeneration associated with MS, and SPMS conversion.

Quantitative susceptibility mapping of the normal-appearing white matter as a potential new marker of disability progression in multiple sclerosis

OBJECTIVES

To investigate the normal-appearing white matter (NAWM) susceptibility in a cohort of newly diagnosed multiple sclerosis (MS) patients and to evaluate possible correlations between NAWM susceptibility and disability progression.

METHODS

Fifty-nine patients with a diagnosis of MS (n = 53) or clinically isolated syndrome (CIS) (n = 6) were recruited and followed up. All participants underwent neurological examination, blood sampling for serum neurofilament light chain (sNfL) level assessment, lumbar puncture for the quantification of cerebrospinal fluid (CSF) β-amyloid1-42 (Aβ) levels, and brain MRI. T2-weighted scans were used to quantify white matter (WM) lesion loads. For each scan, we derived the NAWM volume fraction and the WM lesion volume fraction. Quantitative susceptibility mapping (QSM) of the NAWM was calculated using the susceptibility tensor imaging (STI) suite. Susceptibility maps were computed with the STAR algorithm.

RESULTS

Primary progressive patients (n = 9) showed a higher mean susceptibility value in the NAWM than relapsing-remitting (n = 44) and CIS (n = 6) (p = 0.01 and p = 0.02). Patients with a higher susceptibility in the NAWM showed increased sNfL concentration (ρ = 0.38, p = 0.004) and lower CSF Aβ levels (ρ = -0.34, p = 0.009). Mean NAWM susceptibility turned out to be a predictor of the expanded disability status scale (EDSS) worsening at follow-up (β = 0.41, t = 2.66, p = 0.01) and of the MS severity scale (MSSS) (β = 0.38, t = 2.43, p = 0.019).

CONCLUSIONS

QSM in the NAWM seems to predict the EDSS increment over time. This finding might provide evidence on the role of QSM in identifying patients with an increased risk of early disability progression.

KEY POINTS

• NAWM-QSM is higher in PPMS patients than in RRMS. • NAWM-QSM seems to be a predictor of EDSS worsening over time. • Patients with higher NAWM-QSM show increased sNfL concentration and lower CSF Aβ levels.

Roles and regulation of microglia activity in multiple sclerosis: insights from animal models

As resident macrophages of the CNS, microglia are critical immune effectors of inflammatory lesions and associated neural dysfunctions. In multiple sclerosis (MS) and its animal models, chronic microglial inflammatory activity damages myelin and disrupts axonal and synaptic activity. In contrast to these detrimental effects, the potent phagocytic and tissue-remodelling capabilities of microglia support critical endogenous repair mechanisms. Although these opposing capabilities have long been appreciated, a precise understanding of their underlying molecular effectors is only beginning to emerge. Here, we review recent advances in our understanding of the roles of microglia in animal models of MS and demyelinating lesions and the mechanisms that underlie their damaging and repairing activities. We also discuss how the structured organization and regulation of the genome enables complex transcriptional heterogeneity within the microglial cell population at demyelinating lesions.

The role of iron metabolism in the pathogenesis and treatment of multiple sclerosis

Multiple sclerosis is a severe demyelinating disease mediated by cells of the innate and adaptive immune system, especially pathogenic T lymphocytes that produce the pro-inflammatory cytokine granulocyte-macrophage colony stimulating factor (GM-CSF). Although the factors and molecules that drive the genesis of these cells are not completely known, some were discovered and shown to promote the development of such cells, such as dietary factors. In this regard, iron, the most abundant chemical element on Earth, has been implicated in the development of pathogenic T lymphocytes and in MS development via its effects on neurons and glia. Therefore, the aim of this paper is to revise the state-of-art regarding the role of iron metabolism in cells of key importance to MS pathophysiology, such as pathogenic CD4+ T cells and CNS resident cells. Harnessing the knowledge of iron metabolism may aid in the discovery of new molecular targets and in the development of new drugs that tackle MS and other diseases that share similar pathophysiology.

Relationship between paramagnetic rim lesions and slowly expanding lesions in multiple sclerosis

BACKGROUND

Magnetic resonance imaging (MRI) markers for chronic active lesions in MS include slowly expanding lesions (SELs) and paramagnetic rim lesions (PRLs).

OBJECTIVES

To identify the relationship between SELs and PRLs in MS, and their association with disability.

METHODS

61 people with MS (pwMS) followed retrospectively with MRI including baseline susceptibility-weighted imaging, and longitudinal T1 and T2-weighted scans. SELs were computed using deformation field maps; PRLs were visually identified. Mixed-effects models assessed differences in Expanded Disability Status Scale (EDSS) score changes between the group defined by the presence of SELs and or PRLs.

RESULTS

The median follow-up time was 3.2 years. At baseline, out of 1492 lesions, 616 were classified as SELs, and 80 as PRLs. 92% of patients had ⩾ 1 SEL, 56% had ⩾ 1 PRL, while both were found in 51%. SELs compared to non-SELs were more likely to also be PRLs (7% vs. 4%, p = 0.027). PRL counts positively correlated with SEL counts (ρ= 0.28, p = 0.03). SEL + PRL + patients had greater increases in EDSS over time (beta = 0.15/year, 95% confidence interval (0.04, 0.27), p = 0.009) than SEL+PRL-patients.

CONCLUSION

SELs are more numerous than PRLs in pwMS. Compared with either SELs or PRLs found in isolation, their joint occurrence was associated with greater clinical progression.

Quantitative MRI in Multiple Sclerosis: From Theory to Application

Quantitative MR imaging techniques allow evaluating different aspects of brain microstructure, providing meaningful information about the pathophysiology of damage in CNS disorders. In the study of patients with MS, quantitative MR imaging techniques represent an invaluable tool for studying changes in myelin and iron content occurring in the context of inflammatory and neurodegenerative processes. In the first section of this review, we summarize the physics behind quantitative MR imaging, here defined as relaxometry and quantitative susceptibility mapping, and describe the neurobiological correlates of quantitative MR imaging findings. In the second section, we focus on quantitative MR imaging application in MS, reporting the main findings in both the gray and white matter compartments, separately addressing macroscopically damaged and normal-appearing parenchyma.

χ-Separation Imaging for Diagnosis of Multiple Sclerosis versus Neuromyelitis Optica Spectrum Disorder

Background Use of χ-separation imaging can provide surrogates for iron and myelin that relate closely to abnormal changes in multiple sclerosis (MS) lesions. Purpose To evaluate the appearances of MS and neuromyelitis optica spectrum disorder (NMOSD) brain lesions on χ-separation maps and explore their diagnostic value in differentiating the two diseases in comparison with previously reported diagnostic criteria. Materials and Methods This prospective study included individuals with MS or NMOSD who underwent χ-separation imaging from October 2017 to October 2020. Positive (χ_pos) and negative (χ_neg) susceptibility were estimated separately by using local frequency shifts and calculating R2' (R2' = R2* - R2). R2 mapping was performed with a machine learning approach. For each lesion, presence of the central vein sign (CVS) and paramagnetic rim sign (PRS) and signal characteristics on χ_neg and χ_pos maps were assessed and compared. For each participant, the proportion of lesions with CVS, PRS, and hypodiamagnetism was calculated. Diagnostic performances were assessed using receiver operating characteristic (ROC) curve analysis. Results A total of 32 participants with MS (mean age, 34 years ± 10 [SD]; 25 women, seven men) and 15 with NMOSD (mean age, 52 years ± 17; 14 women, one man) were evaluated, with a total of 611 MS and 225 NMOSD brain lesions. On the χ_neg maps, 80.2% (490 of 611) of MS lesions were categorized as hypodiamagnetic versus 13.8% (31 of 225) of NMOSD lesions (P < .001). Lesion appearances on the χ_pos maps showed no evidence of a difference between the two diseases. In per-participant analysis, participants with MS showed a higher proportion of hypodiamagnetic lesions (83%; IQR, 72-93) than those with NMOSD (6%; IQR, 0-14; P < .001). The proportion of hypodiamagnetic lesions achieved excellent diagnostic performance (area under the ROC curve, 0.96; 95% CI: 0.91, 1.00). Conclusion On χ-separation maps, multiple sclerosis (MS) lesions tend to be hypodiamagnetic, which can serve as an important hallmark to differentiate MS from neuromyelitis optica spectrum disorder. © RSNA, 2022 Supplemental material is available for this article.

New Target for Prevention and Treatment of Neuroinflammation: Microglia Iron Accumulation and Ferroptosis

Microglia play an important role in maintaining central nervous system homeostasis and are the major immune cells in the brain. In response to internal or external inflammatory stimuli, microglia are activated and release numerous inflammatory factors, thus leading to neuroinflammation. Inflammation and microglia iron accumulation promote each other and jointly promote the progression of neuroinflammation. Inhibiting microglia iron accumulation prevents neuroinflammation. Ferroptosis is an iron-dependent phospholipid peroxidation-driven type of cell death regulation. Cell iron accumulation causes the peroxidation of cell membrane phospholipids and damages the cell membrane. Ultimately, this process leads to cell ferroptosis. Iron accumulation or phospholipid peroxidation in microglia releases a large number of inflammatory factors. Thus, inhibiting microglia ferroptosis may be a new target for the prevention and treatment of neuroinflammation.

Geochemistry of multiple sclerosis in Finland

Multiple sclerosis (MS) affects some 3 million people around the world and the prevalence is increasing. The MS incidence increases with distance from the equator forming a north-to-south gradient. The cause of this gradient and the cause of MS in general are largely unknown. Sulphide-bearing marine and lake sediments, when exposed to oxygen after drainage, form sulphuric acid resulting in the development of acid sulphate soils. From these soils major neurotoxic metals such as iron, aluminum and manganese and trace metals such as nickel, copper and cadmium are released into the surrounding environment. As these soils are largely used for farming, obvious routes to human metal exposure exist. Here we compare the distribution of acid sulphate soils in Finland to the geographic localisation of MS cases using data from a national acid sulphate soil mapping project and historical MS distribution data. Finland has among the highest MS prevalences in the world and several independent nationwide surveys have shown the highest prevalence in western Finland, stable over time. Acid sulphate soil distribution colocalizes with MS, both on a regional (nationwide) scale and local (proximity to rivers) scale. A toxicokinetic LADME model for MS pathogenesis is presented. We propose that neurotoxic metals leaching from acid sulphate soils contribute to the clustering of MS in Finland.

Toward In Vivo MRI of the Tissue Proton Exchange Rate in Humans

Quantification of proton exchange rate (kex) is a challenge in MR studies. Current techniques either have low resolutions or are dependent on the estimation of parameters that are not measurable. The Omega plot method, on the other hand, provides a direct way for determining kex independent of the agent concentration. However, it cannot be used for in vivo studies without some modification due to the contributions from the water signal. In vivo tissue proton exchange rate (kex) MRI, based on the direct saturation (DS) removed Omega plot, quantifies the weighted average of kex of the endogenous tissue metabolites. This technique has been successfully employed for imaging the variation in the kex of ex vivo phantoms, as well as in vivo human brains in healthy subjects, and stroke or multiple sclerosis (MS) patients. In this paper, we present a brief review of the methods used for kex imaging with a focus on the development of in vivo kex MRI technique based on the DS-removed Omega plot. We then review the recent clinical studies utilizing this technique for better characterizing brain lesions. We also outline technical challenges for the presented technique and discuss its prospects for detecting tissue microenvironmental changes under oxidative stress.

Longitudinal clinical study of patients with iron rim lesions in multiple sclerosis

Background:

Iron rims (IRs) surrounding white matter lesions (WMLs) are suggested to predict a more severe disease course. Only small longitudinal cohorts of patients with and without iron rim lesions (IRLs) have been reported so far.

Objective:

To assess whether the presence and number of IRLs in patients with clinically isolated syndrome (CIS) and multiple sclerosis (MS) are associated with long-term disability or progressive disease.

Methods:

Ninety-one CIS/MS patients were recruited between 2008 and 2013 and scanned with 7 T magnetic resonance imaging (MRI). Expanded Disability Status Scale (EDSS) was used to calculate Age-related Multiple Sclerosis Severity Score (ARMSS) at the time of scan and at the latest clinical follow-up after 9 years. WMLs were assessed for the presence of IRL using Susceptibility weighted imaging (SWI)-filtered phase images.

Results:

In all, 132 IRLs were detected in 42 patients (46%); 9% of WMLs had IRs; 54% of the cohort had no rims, 30% had 1–3 rims and 16% had ⩾4. Patients with IRL had a higher EDSS and ARMSS. Presence of IRL was also a predictor of long-term disability, especially in patients with ⩾4 IRLs. IRLs have a greater impact on disability compared to the WML number and volume.

Conclusion:

The presence and number of perilesional IR on MRI hold prognostic value for long-term clinical disability in MS.

Quantitative susceptibility mapping of basal ganglia iron is associated with cognitive and motor functions that distinguish spinocerebellar ataxia type 6 and type 3

Background

In spinocerebellar ataxia type 3 (SCA3), volume loss has been reported in the basal ganglia, an iron-rich brain region, but iron content has not been examined. Recent studies have reported that patients with SCA6 have markedly decreased iron content in the cerebellar dentate, coupled with severe volume loss. Changing brain iron levels can disrupt cognitive and motor functions, yet this has not been examined in the SCAs, a disease in which iron-rich regions are affected.

Methods

In the present study, we used quantitative susceptibility mapping (QSM) to measure tissue magnetic susceptibility (indicating iron concentration), structural volume, and normalized susceptibility mass (indicating iron content) in the cerebellar dentate and basal ganglia in people with SCA3 (n = 10) and SCA6 (n = 6) and healthy controls (n = 9). Data were acquired using a 7T Philips MRI scanner. Supplemental measures assessed motor, cognitive, and mood domains.

Results

Putamen volume was lower in both SCA groups relative to controls, replicating prior findings. Dentate susceptibility mass and volume in SCA6 was lower than in SCA3 or controls, also replicating prior findings. The novel finding was that higher basal ganglia susceptibility mass in SCA6 correlated with lower cognitive performance and greater motor impairment, an association that was not observed in SCA3. Cerebellar dentate susceptibility mass, however, had the opposite relationship with cognition and motor function in SCA6, suggesting that, as dentate iron is depleted, it relocated to the basal ganglia, which contributed to cognitive and motor decline. By contrast, basal ganglia volume loss, rather than iron content, appeared to drive changes in motor function in SCA3.

Conclusion

The associations of higher basal ganglia iron with lower motor and cognitive function in SCA6 but not in SCA3 suggest the potential for using brain iron deposition profiles beyond the cerebellar dentate to assess disease states within the cerebellar ataxias. Moreover, the role of the basal ganglia deserves greater attention as a contributor to pathologic and phenotypic changes associated with SCA.

Myelinated axons are the primary target of hemin-mediated oxidative damage in a model of the central nervous system

Iron released from oligodendrocytes during demyelination or derived from haemoglobin breakdown products is believed to amplify oxidative tissue injury in multiple sclerosis (MS). However, the pathophysiological significance of iron-containing haemoglobin breakdown products themselves is rarely considered in the context of MS and their cellular specificity and mode of action remain unclear. Using myelinating cell cultures, we now report the cytotoxic potential of hemin (ferriprotoporphyrin IX chloride), a major degradation product of haemoglobin, is 25-fold greater than equimolar concentrations of free iron in myelinating cultures; a model that reproduces the complex multicellular environment of the CNS. At low micro molar concentrations (3.3 - 10 μM) we observed hemin preferentially binds to myelin and axons to initiate a complex detrimental response that results in targeted demyelination and axonal loss but spares neuronal cell bodies, astrocytes and the majority of oligodendroglia. Demyelination and axonal loss in this context are executed by a combination of mechanisms that include iron-dependent peroxidation by reactive oxygen species (ROS) and ferroptosis. These effects are microglial-independent, do not require any initiating inflammatory insult and represent a direct effect that compromises the structural integrity of myelinated axons in the CNS. Our data identify hemin-mediated demyelination and axonal loss as a novel mechanism by which intracerebral degradation of haemoglobin may contribute to lesion development in MS.

Multidimensional overview of neurofilament light chain contribution to comprehensively understanding multiple sclerosis

Multiple sclerosis (MS) is an inflammatory neurodegenerative disease characterized by demyelination, progressive axonal loss, and varying clinical presentations. Axonal damage associated with the inflammatory process causes neurofilaments, the major neuron structural proteins, to be released into the extracellular space, reaching the cerebrospinal fluid (CSF) and the peripheral blood. Methodological advances in neurofilaments’ serological detection and imaging technology, along with many clinical and therapeutic studies in the last years, have deepened our understanding of MS immunopathogenesis. This review examines the use of light chain neurofilaments (NFLs) as peripheral MS biomarkers in light of the current clinical and therapeutic evidence, MS immunopathology, and technological advances in diagnostic tools. It aims to highlight NFL multidimensional value as a reliable MS biomarker with a diagnostic-prognostic profile while improving our comprehension of inflammatory neurodegenerative processes, mainly RRMS, the most frequent clinical presentation of MS.

Paramagnetic Rim Lesions in Multiple Sclerosis: Comparison of Visualization at 1.5-T and 3-T MRI

BACKGROUND. Multiple sclerosis (MS) is characterized by both acute and chronic intrathecal inflammation. A subset of MS lesions show paramagnetic rims on susceptibility-weighted MRI sequences, reflecting iron accumulation in microglia. These para-magnetic rim lesions have been proposed as a marker of compartmentalized smoldering disease. Paramagnetic rim lesions have been shown at 7 T and, more recently, at 3 T. As susceptibility effects are weaker at lower field strength, it remains unclear if paramagnetic rim lesions are visible at 1.5 T. OBJECTIVE. The purpose of our study was to compare visualization of paramagnetic rim lesions using susceptibility-weighted imaging at 1.5-T and 3-T MRI in patients with MS. METHODS. This retrospective study included nine patients (five women, four men; mean age, 46.8 years) with MS who underwent both 1.5-T and 3-T MRI using a comparable susceptibility-weighted angiography (SWAN) sequence from the same manufacturer. Lesions measuring greater than 3 mm were annotated. Two reviewers independently assessed images at each field strength in separate sessions and classified the annotated lesions as isointense, diffusely paramagnetic, or paramagnetic rim lesions. Discrepancies were discussed at consensus sessions including a third reviewer. Agreement was assessed using kappa coefficients. RESULTS. Based on the 3-T consensus readings, 115 of 140 annotated lesions (82%) were isointense lesions, 16 (11%) were diffusely paramagnetic lesions, and nine (6%) were paramagnetic rim lesions; based on the 1.5-T consensus readings, 115 (82%) were isointense lesions, 14 (10%) were diffusely paramagnetic lesions, and 11 (8%) were para-magnetic rim lesions. The mean lesion diameter was 11.9 mm for paramagnetic rim lesions versus 6.4 mm for diffusely paramagnetic lesions (p = .006) and 7.8 mm for iso-intense lesions (p = .003). Interrater agreement for lesion classification as a paramagnetic rim lesion was substantial at 1.5 T (κ = 0.65) and 3 T (κ = 0.70). Agreement for paramagnetic rim lesions was also substantial between the consensus readings at the two field strengths (κ = 0.79). CONCLUSION. We show comparable identification of paramagnetic rim lesions at 1.5-T and 3-T MRI with substantial interrater agreement at both field strengths and substantial consensus agreement between the field strengths. CLINICAL IMPACT. Paramagnetic rim lesions may be an emerging marker of chronic neuroinflammation in MS. Their visibility at 1.5 T supports the translational potential of paramagnetic rim lesion identification to more widespread clinical settings, where 1.5-T scanners are prevalent.

Dysregulation of Iron Homeostasis in the Central Nervous System and the Role of Ferroptosis in Neurodegenerative Disorders

Significance: Iron accumulation occurs in the central nervous system (CNS) in a variety of neurological conditions as diverse as spinal cord injury, stroke, multiple sclerosis, Parkinson's disease, and others. Iron is a redox-active metal that gives rise to damaging free radicals if its intracellular levels are not controlled or if it is not properly sequestered within cells. The accumulation of iron occurs due to dysregulation of mechanisms that control cellular iron homeostasis. Recent Advances: The molecular mechanisms that regulate cellular iron homeostasis have been revealed in much detail in the past three decades, and new advances continue to be made. Understanding which aspects of iron homeostasis are dysregulated in different conditions will provide insights into the causes of iron accumulation and iron-mediated tissue damage. Recent advances in iron-dependent lipid peroxidation leading to cell death, called ferroptosis, has provided useful insights that are highly relevant for the lipid-rich environment of the CNS. Critical Issues: This review examines the mechanisms that control normal cellular iron homeostasis, the dysregulation of these mechanisms in neurological disorders, and more recent work on how iron can induce tissue damage via ferroptosis. Future Directions: Quick and reliable tests are needed to determine if and when ferroptosis contributes to the pathogenesis of neurological disorders. In addition, there is need to develop better druggable agents to scavenge lipid radicals and reduce CNS damage for neurological conditions for which there are currently few effective treatments. Antioxid. Redox Signal. 37, 150-170.

Peripheral Hemolysis in Relation to Iron Rim Presence and Brain Volume in Multiple Sclerosis

Background:

Iron rim lesions (IRLs) represent chronic lesion activity and are associated with a more severe disease course in multiple sclerosis (MS). How the iron rims around the lesions arise in patients with MS (pwMS), and whether peripheral hemolysis may be a source of iron in rim associated macrophages, is unclear.

Objective

To determine a potential correlation between peripheral hemolysis parameters and IRL presence in pwMS.

Methods

This retrospective study included pwMS, who underwent a 3T brain MRI between 2015 and 2020 and had a blood sample drawn at ± 2 weeks. Patients with vertigo served as a control group.

Results

We analyzed 75 pwMS (mean age 37.0 years [SD 9.0], 53.3% female) and 43 controls (mean age 38.3 years [SD 9.8], 51.2% female). Median number of IRLs was 1 (IQR 4), 28 (37.3%) pwMS had no IRLs. IRL patients showed significantly higher Expanded Disability Status Scale (EDSS) compared to non-IRL patients (median EDSS 2.3 [IQR 2.9] vs. 1.3 [IQR 2.9], p = 0.017). Number of IRLs correlated significantly with disease duration (r_s = 0.239, p = 0.039), EDSS (r_s = 0.387, p < 0.001) and Multiple Sclerosis Severity Scale (MSSS) (r_s = 0.289, p = 0.014). There was no significant difference in hemolysis parameters between non-IRL, IRL patients (regardless of gender and/or disease type) and controls, nor between hemolysis parameters and the number of IRLs. Total brain volume was associated with fibrinogen (β= −0.34, 95% CI −1.32 to −0.145, p = 0.016), and absolute cortical and total gray matter volumes were associated with hemoglobin (β = 0.34, 95% CI 3.39–24.68, p = 0.011; β = 0.33, 95% CI 3.29–28.95, p = 0.015; respectively).

Conclusion

Our data do not suggest an association between hemolysis parameters and IRL presence despite a significant association between these parameters and markers for neurodegeneration.

Magnetic Susceptibility Source Separation Solely from Gradient Echo Data: Histological Validation

Quantitative susceptibility mapping (QSM) facilitates mapping of the bulk magnetic susceptibility of tissue from the phase of complex gradient echo (GRE) MRI data. QSM phase processing combined with an R2* model of magnitude of multiecho gradient echo data (R2*QSM) allows separation of dia- and para-magnetic components (e.g., myelin and iron) that contribute constructively to R2* value but destructively to the QSM value of a voxel. This R2*QSM technique is validated against quantitative histology—optical density of myelin basic protein and Perls’ iron histological stains of rim and core of 10 ex vivo multiple sclerosis lesions, as well as neighboring normal appearing white matter. We found that R2*QSM source maps are in good qualitative agreement with histology, e.g., showing increased iron concentration at the edge of the rim+ lesions and myelin loss in the lesions’ core. Furthermore, our results indicate statistically significant correlation between paramagnetic and diamagnetic tissue components estimated with R2*QSM and optical densities of Perls’ and MPB stains. These findings provide direct support for the use of R2*QSM magnetic source separation based solely on GRE complex data to characterize MS lesion composition.

Susceptibility source separation from gradient echo data using magnitude decay modeling

BACKGROUND AND PURPOSE

The objective is to demonstrate feasibility of separating magnetic sources in quantitative susceptibility mapping (QSM) by incorporating magnitude decay rates R 2 ∗ $R_2^{\rm{*}}$ in gradient echo (GRE) MRI.

METHODS

Magnetic susceptibility source separation was developed using R 2 ∗ $R_2^{\rm{*}}$ and compared with a prior method using R 2 ' = R 2 ∗ - R 2 ${R^{\prime}_2} = R_2^* - {R_2}$ that required an additional sequence to measure the transverse relaxation rate R₂ . Both susceptibility separation methods were compared in multiple sclerosis (MS) patients (n = 17). Susceptibility values of negative sources estimated with R 2 ∗ $R_2^{\rm{*}}$ -based source separation in a set of enhancing MS lesions (n = 44) were correlated against longitudinal myelin water fraction (MWF) changes.

RESULTS

In in vivo data, linear regression of the estimated χ + ${\chi}^{+}$ and χ - ${\chi}^{-}$ susceptibility values between the R 2 ∗ $R_2^*$ - and the R 2 ' ${R^{\prime}_2}$ -based separation methods performed across 182 segmented lesions revealed correlation coefficient r = .96 and slope close .99. Correlation analysis in enhancing lesions revealed a significant positive association between the χ - ${\chi}^{-}$ increase at 1-year post-onset relative to 0 year and the MWF increase at 1 year relative to 0 year (β = -0.144, 95% confidence interval: [-0.199, -0.1], p = .0008) and good agreement between R 2 ' ${R^{\prime}_2}$ and R 2 ∗ $R_2^*$ methods (r = .79, slope = .95).

CONCLUSIONS

Separation of magnetic sources based solely on GRE complex data is feasible by combining magnitude decay rate modeling and phase-based QSM and χ - ${\chi}^{-}$ change may serve as a biomarker for myelin recovery or damage in acute MS lesions.

Hepcidin (rs10421768), Transferrin (rs3811647, rs1049296) and Transferrin Receptor 2 (rs7385804) Gene Polymorphism Might Be Associated with the Origin of Multiple Sclerosis

Multiple sclerosis (MS) is a demyelinating disease of the central nervous system in which there is a multifocal damage to the nerve tissue. Additionally, the literature emphasizes the excessive accumulation of iron in the central nervous system of patients, which is negatively correlated with their psychophysical fitness. Iron metabolism genes polymorphisms may modulate iron deposition in the body and thus affect the clinical course of MS. We aimed to assess the frequency of HAMP, TFR2, and TF polymorphisms in MS patients and their impact on the clinical course of the disease. The studied polymorphisms were identified by the Real-Time PCR using TaqMan technology. Neurological assessment by means of EDSS scale was conducted. This cross-sectional study included 176 patients, with the mean age of onset of symptoms at 30.6 years. The frequency of alleles of the studied polymorphisms was as follows: (a) HAMP rs10421768: A 75.9% (n = 267), G 24.1% (n = 65), (b) TF rs1049296: C 89.2% (n = 314), T 10.8% (n = 38), (c) TF rs3811647: A 39.8% (n = 140), G 60.2% (n = 212), (d) TFR2 rs7385804: A 59.1% (n = 59.1%), C 40.9% (n = 144). In the codominant inheritance model of TF rs1049269, it was shown that people with the CT genotype scored statistically significantly lower points in the EDSS scale at the time of diagnosis than those with the CC genotype (CC Me = 1.5, CT Me = 1.0 p = 0.0236). In the recessive model of TF inheritance rs3811647, it was noticed that the primary relapses were significantly more frequent in patients with at least one G allele compared with those with the AA genotype (AG + GG = 81.2%, AA = 18.8%, p = 0.0354). In the overdominant model rs7385804 TFR2, it was shown that among patients with the AA genotype, multiple sclerosis occurs significantly more often in relatives in a straight line compared with people with the AC and CC genotypes (AA = 100.0%, AC + CC = 0.0%, p = 0.0437). We concluded that the studied polymorphisms might affect the clinical course of MS.

Human serum albumin in neurodegeneration

Serum albumin (SA) exists in relatively high concentrations, in close contact with most cells. However, in the adult brain, except for cerebrospinal fluid (CSF), SA concentration is relatively low. It is mainly produced in the liver to serve as the main protein of the blood plasma. In the plasma, it functions as a carrier, chaperon, antioxidant, source of amino acids, osmoregulator, etc. As a carrier, it facilitates the stable presence and transport of the hydrophobic and hydrophilic molecules, including free fatty acids, steroid hormones, medicines, and metal ions. As a chaperon, SA binds to and protects other proteins. As an antioxidant, thanks to a free sulfhydryl group (-SH), albumin is responsible for most antioxidant properties of plasma. These functions qualify SA as a major player in, and a mirror of, overall health status, aging, and neurodegeneration. The low concentration of SA is associated with cognitive deterioration in the elderly and negative prognosis in multiple sclerosis (MS) and amyotrophic lateral sclerosis (ALS). SA has been shown to be structurally modified in neurological conditions such as Alzheimer's disease (AD). During blood-brain barrier damage albumin enters the brain tissue and could trigger epilepsy and neurodegeneration. SA is able to bind to the precursor agent of the AD, amyloid-beta (Aβ), preventing its toxic effects in the periphery, and is being tested for treating this disease. SA therapy may also be effective in brain rejuvenation. In the current review, we will bring forward the prominent properties and roles of SA in neurodegeneration.

SWI as an Alternative to Contrast-Enhanced Imaging to Detect Acute MS Lesions

BACKGROUND AND PURPOSE

Acute inflammatory activity of MS lesions is traditionally assessed through contrast-enhanced T1-weighted MR images. The aim of our study was to determine whether a qualitative evaluation of non-contrast-enhanced SWI of new T2-hyperintense lesions might help distinguish acute and chronic lesions and whether it could be considered a possible alternative to gadolinium-based contrast agents for this purpose.

MATERIALS AND METHODS

Serial MR imaging studies from 55 patients with MS were reviewed to identify 169 new T2-hyperintense lesions. Two blinded neuroradiologists determined their signal pattern on SWI, considering 5 categories (hypointense rings, marked hypointensity, mild hypointensity, iso-/hyperintensity, indeterminate). Two different blinded neuroradiologists evaluated the presence or absence of enhancement in postcontrast T1-weighted images of the lesions. The Fisher exact test was used to determine whether each category of signal intensity on SWI was associated with gadolinium enhancement.

RESULTS

The presence of hypointense rings or marked hypointensity showed a strong association with the absence of gadolinium enhancement (P < .001), with a sensitivity of 93.0% and a specificity of 82.9%. The presence of mild hypointensity or isohyperintensity showed a strong association with the presence of gadolinium enhancement (P < .001), with a sensitivity of 68.3% and a specificity of 99.2%.

CONCLUSIONS

A qualitative analysis of the signal pattern on SWI of new T2-hyperintense MS lesions allows determining the likelihood that the lesions will enhance after administration of a gadolinium contrast agent, with high specificity albeit with a moderate sensitivity. While it cannot substitute for the use of contrast agent, it can be useful in some clinical settings in which the contrast agent cannot be administered.

Disease correlates of rim lesions on quantitative susceptibility mapping in multiple sclerosis

Quantitative susceptibility mapping (QSM), an imaging technique sensitive to brain iron, has been used to detect paramagnetic rims of iron-laden active microglia and macrophages in a subset of multiple sclerosis (MS) lesions, known as rim+ lesions, that are consistent with chronic active lesions. Because of the potential impact of rim+ lesions on disease progression and tissue damage, investigating their influence on disability and neurodegeneration is critical to establish the impact of these lesions on the disease course. This study aimed to explore the relationship between chronic active rim+ lesions, identified as having a hyperintense rim on QSM, and both clinical disability and imaging measures of neurodegeneration in patients with MS. The patient cohort was composed of 159 relapsing-remitting multiple sclerosis patients. The Expanded Disability Status Scale (EDSS) and Brief International Cognitive Assessment for Multiple Sclerosis, which includes both the Symbol Digit Modalities Test and California Verbal Learning Test-II, were used to assess clinical disability. Cortical thickness and thalamic volume were evaluated as imaging measures of neurodegeneration. A total of 4469 MS lesions were identified, of which 171 QSM rim+ (3.8%) lesions were identified among 57 patients (35.8%). In a multivariate regression model, as the overall total lesion burden increased, patients with at least one rim+ lesion on QSM performed worse on both physical disability and cognitive assessments, specifically the Symbol Digit Modalities Test (p = 0.010), California Verbal Learning Test-II (p = 0.030), and EDSS (p = 0.001). In a separate univariate regression model, controlling for age (p < 0.001) and having at least one rim+ lesion was related to more cortical thinning (p = 0.03) in younger patients (< 45 years). Lower thalamic volume was associated with older patients (p = 0.038) and larger total lesion burden (p < 0.001); however, the association did not remain significant with rim+ lesions (p = 0.10). Our findings demonstrate a novel observation that chronic active lesions, as identified on QSM, modify the impact of lesion burden on clinical disability in MS patients. These results support further exploration of rim+ lesions for therapeutic targeting in MS to reduce disability and subsequent neurodegeneration.

Dimethyl Fumarate Reduces Inflammation in Chronic Active Multiple Sclerosis Lesions

Background and Objectives

To determine the effects of dimethyl fumarate (DMF) and glatiramer acetate on iron content in chronic active lesions in patients with multiple sclerosis (MS) and in human microglia in vitro.

Methods

This was a retrospective observational study of 34 patients with relapsing-remitting MS and clinically isolated syndrome treated with DMF or glatiramer acetate. Patients had lesions with hyperintense rims on quantitative susceptibility mapping, were treated with DMF or glatiramer acetate (GA), and had a minimum of 2 on-treatment scans. Changes in susceptibility in rim lesions were compared among treatment groups in a linear mixed effects model. In a separate in vitro study, induced pluripotent stem cell–derived human microglia were treated with DMF or GA, and treatment-induced changes in iron content and activation state of microglia were compared.

Results

Rim lesions in patients treated with DMF had on average a 2.77-unit reduction in susceptibility per year over rim lesions in patients treated with GA (bootstrapped 95% CI −5.87 to −0.01), holding all other variables constant. Moreover, DMF but not GA reduced inflammatory activation and concomitantly iron content in human microglia in vitro.

Discussion

Together, our data indicate that DMF-induced reduction of susceptibility in MS lesions is associated with a decreased activation state in microglial cells. We have demonstrated that a specific disease modifying therapy, DMF, decreases glial activity in chronic active lesions. Susceptibility changes in rim lesions provide an in vivo biomarker for the effect of DMF on microglial activity.

Classification of Evidence

This study provided Class III evidence that DMF is superior to GA in the presence of iron as a marker of inflammation as measured by MRI quantitative susceptibility mapping.

The mechanistic target of rapamycin as a regulator of metabolic function in oligodendroglia during remyelination

Despite evidence for prominent metabolic dysfunction within multiple sclerosis (MS) lesions, the mechanisms controlling metabolic shifts in oligodendroglia are poorly understood. The cuprizone model of demyelination and remyelination is a valuable tool for assessing metabolic insult during oligodendrocyte death and myelin degradation, closely resembling the distal oligodendrogliopathy seen in Pattern III MS lesions. In this review we discuss how metabolic processes in oligodendrocytes are disrupted in both MS and the cuprizone model, as well as the evidence for mechanistic target of rapamycin (mTOR) signaling as a key regulator of oligodendroglial metabolic function and efficient remyelination.

Fully automated detection of paramagnetic rims in multiple sclerosis lesions on 3T susceptibility-based MR imaging

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Paramagnetic rim lesions are an important subtype of multiple sclerosis lesion.

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Automated methods can accelerate the assessment of paramagnetic rim lesions.

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APRL automatically identifies and accurately classifies paramagnetic rim lesions.

Background and Purpose

The presence of a paramagnetic rim around a white matter lesion has recently been shown to be a hallmark of a particular pathological type of multiple sclerosis lesion. Increased prevalence of these paramagnetic rim lesions is associated with a more severe disease course in MS, but manual identification is time-consuming. We present APRL, a method to automatically detect paramagnetic rim lesions on 3T T2*-phase images.

Methods

T1-weighted, T2-FLAIR, and T2*-phase MRI of the brain were collected at 3T for 20 subjects with MS. The images were then processed with automated lesion segmentation, lesion center detection, lesion labelling, and lesion-level radiomic feature extraction. A total of 951 lesions were identified, 113 (12%) of which contained a paramagnetic rim. We divided our data into a training set (16 patients, 753 lesions) and a testing set (4 patients, 198 lesions), fit a random forest classification model on the training set, and assessed our ability to classify paramagnetic rim lesions on the test set.

Results

The number of paramagnetic rim lesions per subject identified via our automated lesion labelling method was highly correlated with the gold standard count per subject, r = 0.86 (95% CI [0.68, 0.94]). The classification algorithm using radiomic features classified lesions with an area under the curve of 0.82 (95% CI [0.74, 0.92]).

Conclusion

This study develops a fully automated technique, APRL, for the detection of paramagnetic rim lesions using standard T1 and FLAIR sequences and a T2*phase sequence obtained on 3T MR images.

Iron Rims in Patients With Multiple Sclerosis as Neurodegenerative Marker? A 7-Tesla Magnetic Resonance Study

Introduction: Multiple sclerosis (MS) is a demyelinating and neurodegenerative disease of the central nervous system, characterized by inflammatory-driven demyelination. Symptoms in MS manifest as both physical and neuropsychological deficits. With time, inflammation is accompanied by neurodegeneration, indicated by brain volume loss on an MRI. Here, we combined clinical, imaging, and serum biomarkers in patients with iron rim lesions (IRLs), which lead to severe tissue destruction and thus contribute to the accumulation of clinical disability.

Objectives: Subcortical atrophy and ventricular enlargement using an automatic segmentation pipeline for 7 Tesla (T) MRI, serum neurofilament light chain (sNfL) levels, and neuropsychological performance in patients with MS with IRLs and non-IRLs were assessed.

Methods: In total 29 patients with MS [15 women, 24 relapsing-remitting multiple sclerosis (RRMS), and five secondary-progressive multiple sclerosis (SPMS)] aged 38 (22–69) years with an Expanded Disability Status Score of 2 (0–8) and a disease duration of 11 (5–40) years underwent neurological and neuropsychological examinations. Volumes of lesions, subcortical structures, and lateral ventricles on 7-T MRI (SWI, FLAIR, and MP2RAGE, 3D Segmentation Software) and sNfL concentrations using the Simoa SR-X Analyzer in IRL and non-IRL patients were assessed.

Results: (1) Iron rim lesions patients had a higher FLAIR lesion count (p = 0.047). Patients with higher MP2Rage lesion volume exhibited more IRLs (p <0.014) and showed poorer performance in the information processing speed tested within 1 year using the Symbol Digit Modalities Test (SDMT) (p <0.047). (2) Within 3 years, patients showed atrophy of the thalamus (p = 0.021) and putamen (p = 0.043) and enlargement of the lateral ventricles (p = 0.012). At baseline and after 3 years, thalamic volumes were lower in IRLs than in non-IRL patients (p = 0.045). (3) At baseline, IRL patients had higher sNfL concentrations (p = 0.028). Higher sNfL concentrations were associated with poorer SDMT (p = 0.004), regardless of IRL presence. (4) IRL and non-IRL patients showed no significant difference in the neuropsychological performance within 1 year.

Conclusions: Compared with non-IRL patients, IRL patients had higher FLAIR lesion counts, smaller thalamic volumes, and higher sNfL concentrations. Our pilot study combines IRL and sNfL, two biomarkers considered indicative for neurodegenerative processes. Our preliminary data underscore the reported destructive nature of IRLs.

Phenotyping of multiple sclerosis lesions according to innate immune cell activation using 18 kDa translocator protein-PET

Chronic active lesions are promotors of neurodegeneration and disease progression in multiple sclerosis. They harbour a dense rim of activated innate immune cells at the lesion edge, which promotes lesion growth and thereby induces damage. Conventional MRI is of limited help in identifying the chronic active lesions, so alternative imaging modalities are needed. Objectives were to develop a PET-based automated analysis method for phenotyping of chronic lesions based on lesion-associated innate immune cell activation and to comprehensively evaluate the prevalence of these lesions in the various clinical subtypes of multiple sclerosis, and their association with disability. In this work, we use 18 kDa translocator protein-PET imaging for phenotyping chronic multiple sclerosis lesions at a large scale. For this, we identified 1510 white matter T1-hypointense lesions from 91 multiple sclerosis patients (67 relapsing–remitting patients and 24 secondary progressive patients). Innate immune cell activation at the lesion rim was measured using PET imaging and the 18 kDa translocator protein-binding radioligand ¹¹C-PK11195. A T1-hypointense lesion was classified as rim-active if the distribution volume ratio of ¹¹C-PK11195-binding was low in the plaque core and considerably higher at the plaque edge. If no significant ligand binding was observed, the lesion was classified as inactive. Plaques that had considerable ligand binding both in the core and at the rim were classified as overall-active. Conventional MRI and disability assessment using the Expanded Disability Status Scale were performed at the time of PET imaging. In the secondary progressive cohort, an average of 19% (median, interquartile range: 11–26) of T1 lesions were rim-active in each individual patient, compared to 10% (interquartile range: 0–20) among relapsing–remitting patients (P = 0.009). Secondary progressive patients had a median of 3 (range: 0–11) rim-active lesions, versus 1 (range: 0–18) among relapsing–remitting patients (P = 0.029). Among those patients who had rim-active lesions (n = 63), the average number of active voxels at the rim was higher among secondary progressive compared to relapsing–remitting patients (median 158 versus 74; P = 0.022). The number of active voxels at the rim correlated significantly with the Expanded Disability Status Scale (R = 0.43, P < 0.001), and the volume of the rim-active lesions similarly correlated with the Expanded Disability Status Scale (R = 0.45, P < 0.001). Our study is the first to report in vivo phenotyping of chronic lesions at large scale, based on 18 kDa translocator protein-PET. Patients with higher disability displayed a higher proportion of rim-active lesions. The in vivo lesion phenotyping methodology offers a new tool for individual assessment of smouldering (rim-active) lesion burden.

Neuroinflammation: 2022 update

Besides important progress in the understanding of the pathological substrate of COVID-19-associated brain disease, major insights into mechanisms of neurodegeneration in human disease have been provided in neuropathological studies published in 2021. Recently developed techniques, which allow the simultaneous detection of a large battery of different molecules within single cells, have proven useful in the analysis of disease mechanisms in experimental and human neuroinflammatory conditions. They have elucidated protective and detrimental effects of activated microglia, which act in a stage and context-dependent manner in the induction and propagation of neurodegeneration. In addition, they emphasize the importance of synaptic damage and of selective neuronal vulnerability in the respective diseases. The results provide important new insights with high clinical relevance.

Cortical and phase rim lesions on 7 T MRI as markers of multiple sclerosis disease progression

In multiple sclerosis, individual lesion-type patterns on magnetic resonance imaging might be valuable for predicting clinical outcome and monitoring treatment effects. Neuropathological and imaging studies consistently show that cortical lesions contribute to disease progression. The presence of chronic active white matter lesions harbouring a paramagnetic rim on susceptibility-weighted magnetic resonance imaging has also been associated with an aggressive form of multiple sclerosis. It is, however, still uncertain how these two types of lesions relate to each other, or which one plays a greater role in disability progression. In this prospective, longitudinal study in 100 multiple sclerosis patients (74 relapsing-remitting, 26 secondary progressive), we used ultra-high field 7-T susceptibility imaging to characterize cortical and rim lesion presence and evolution. Clinical evaluations were obtained over a mean period of 3.2 years in 71 patients, 46 of which had a follow-up magnetic resonance imaging. At baseline, cortical and rim lesions were identified in 96% and 63% of patients, respectively. Rim lesion prevalence was similar across disease stages. Patients with rim lesions had higher cortical and overall white matter lesion load than subjects without rim lesions (P = 0.018-0.05). Altogether, cortical lesions increased by both count and volume (P = 0.004) over time, while rim lesions expanded their volume (P = 0.023) whilst lacking new rim lesions; rimless white matter lesions increased their count but decreased their volume (P = 0.016). We used a modern machine learning algorithm based on extreme gradient boosting techniques to assess the cumulative power as well as the individual importance of cortical and rim lesion types in predicting disease stage and disability progression, alongside with more traditional imaging markers. The most influential imaging features that discriminated between multiple sclerosis stages (area under the curve±standard deviation = 0.82 ± 0.08) included, as expected, the normalized white matter and thalamic volume, white matter lesion volume, but also leukocortical lesion volume. Subarachnoid cerebrospinal fluid and leukocortical lesion volumes, along with rim lesion volume were the most important predictors of Expanded Disability Status Scale progression (area under the curve±standard deviation = 0.69 ± 0.12). Taken together, these results indicate that while cortical lesions are extremely frequent in multiple sclerosis, rim lesion development occurs only in a subset of patients. Both, however, persist over time and relate to disease progression. Their combined assessment is needed to improve the ability of identifying multiple sclerosis patients at risk of progressing disease.

Alterations in Sensorimotor and Mesiotemporal Cortices and Diffuse White Matter Changes in Primary Progressive Multiple Sclerosis Detected by Adiabatic Relaxometry

Background: The research of primary progressive multiple sclerosis (PPMS) has not been able to capitalize on recent progresses in advanced magnetic resonance imaging (MRI) protocols.

Objective: The presented cross-sectional study evaluated the utility of four different MRI relaxation metrics and diffusion-weighted imaging in PPMS.

Methods: Conventional free precession T1 and T2, and rotating frame adiabatic T1ρ and T2ρ in combination with diffusion-weighted parameters were acquired in 13 PPMS patients and 13 age- and sex-matched controls.

Results: T1ρ, a marker of crucial relevance for PPMS due to its sensitivity to neuronal loss, revealed large-scale changes in mesiotemporal structures, the sensorimotor cortex, and the cingulate, in combination with diffuse alterations in the white matter and cerebellum. T2ρ, particularly sensitive to local tissue background gradients and thus an indicator of iron accumulation, concurred with similar topography of damage, but of lower extent. Moreover, these adiabatic protocols outperformed both conventional T1 and T2 maps and diffusion tensor/kurtosis approaches, methods previously used in the MRI research of PPMS.

Conclusion: This study introduces adiabatic T1ρ and T2ρ as elegant markers confirming large-scale cortical gray matter, cerebellar, and white matter alterations in PPMS invisible to other in vivo biomarkers.