Aging, Cellular Senescence, and Progressive Multiple Sclerosis

Understanding the Complex Dynamics of Immunosenescence in Multiple Sclerosis: From Pathogenesis to Treatment

Immunosenescence, the gradual deterioration of immune function with age, holds profound implications for our understanding and management of multiple sclerosis (MS), a chronic autoimmune disease affecting the central nervous system. Traditionally diagnosed in young adults, advancements in disease-modifying therapies and increased life expectancy have led to a growing number of older individuals with MS. This demographic shift underscores the need for a deeper investigation into how age-related alterations in immune function shape the course of MS, influencing disease progression, treatment effectiveness, and overall patient outcomes. Age-related immunosenescence involves changes such as shifts in cytokine profiles, the accumulation of senescent immune cells, and compromised immune surveillance, collectively contributing to a state known as "inflammaging". In the context of MS, these immunological changes disturb the intricate balance between inflammatory and regulatory responses, thereby impacting mechanisms of central immune tolerance and peripheral regulation. This paper stands out by combining the most recent advancements in immunosenescence with both pathophysiological and treatment perspectives on multiple sclerosis, offering a cohesive and accessible discussion that bridges theory and practice, while also introducing novel insights into underexplored concepts such as therapy discontinuation and the latest senolytic, neuroprotective, and remyelination therapies. Enhancing our understanding of these complexities will guide tailored approaches to MS management, ultimately improving clinical outcomes for affected individuals.

Determinants and Biomarkers of Progression Independent of Relapses in Multiple Sclerosis

Clinical, pathological, and imaging evidence in multiple sclerosis (MS) suggests that a smoldering inflammatory activity is present from the earliest stages of the disease and underlies the progression of disability, which proceeds relentlessly and independently of clinical and radiological relapses (PIRA). The complex system of pathological events driving "chronic" worsening is likely linked with the early accumulation of compartmentalized inflammation within the central nervous system as well as insufficient repair phenomena and mitochondrial failure. These mechanisms are partially lesion-independent and differ from those causing clinical relapses and the formation of new focal demyelinating lesions; they lead to neuroaxonal dysfunction and death, myelin loss, glia alterations, and finally, a neuronal network dysfunction outweighing central nervous system (CNS) compensatory mechanisms. This review aims to provide an overview of the state of the art of neuropathological, immunological, and imaging knowledge about the mechanisms underlying the smoldering disease activity, focusing on possible early biomarkers and their translation into clinical practice. ANN NEUROL 2024;96:1-20.

Managing multiple sclerosis in individuals aged 55 and above: a comprehensive review

Multiple Sclerosis (MS) management in individuals aged 55 and above presents unique challenges due to the complex interaction between aging, comorbidities, immunosenescence, and MS pathophysiology. This comprehensive review explores the evolving landscape of MS in older adults, including the increased incidence and prevalence of MS in this age group, the shift in disease phenotypes from relapsing-remitting to progressive forms, and the presence of multimorbidity and polypharmacy. We aim to provide an updated review of the available evidence of disease-modifying treatments (DMTs) in older patients, including the efficacy and safety of existing therapies, emerging treatments such as Bruton tyrosine kinase (BTKs) inhibitors and those targeting remyelination and neuroprotection, and the critical decisions surrounding the initiation, de-escalation, and discontinuation of DMTs. Non-pharmacologic approaches, including physical therapy, neuromodulation therapies, cognitive rehabilitation, and psychotherapy, are also examined for their role in holistic care. The importance of MS Care Units and advance care planning are explored as a cornerstone in providing patient-centric care, ensuring alignment with patient preferences in the disease trajectory. Finally, the review emphasizes the need for personalized management and continuous monitoring of MS patients, alongside advocating for inclusive study designs in clinical research to improve the management of this growing patient demographic.

Impact of NLRP3 Depletion on Aging-Related Metaflammation, Cognitive Function, and Social Behavior in Mice

Immunosenescence and chronic inflammation associated with old age accompany brain aging and the loss of complex behaviors. Neuroinflammation in the hippocampus plays a pivotal role in the development of cognitive impairment and anxiety. However, the underlying mechanisms have not been fully explained. In this study, we aimed to investigate the disruption of insulin signaling and the mechanisms underlying metabolic inflammation ("metaflammation") in the brains of wild-type (WT) and NLRP3 knockout (KO) mice of different ages. We found a significant upregulation of the NLRP3 inflammasome in the hippocampus during aging, leading to an increase in the expression of phosphorylated metaflammation proteinases and inflammatory markers, along with an increase in the number of senescent cells. Additionally, metaflammation causes anxiety and impairs social preference behavior in aged mice. On the other hand, deletion of NLRP3 improves some behavioral and biochemical characteristics associated with aging, such as signal memory, neuroinflammation, and metabolic inflammation, but not anxious behavior. These results are associated with reduced IL-18 signaling and the PKR/IKKβ/IRS1 pathway as well as the SASP phenotype. In NLRP3 gene deletion conditions, PKR is down-regulated. Therefore, it is likely that slowing aging through various NLRP3 inhibition mechanisms will lessen the corresponding cognitive decline with aging. Thus, the genetic knockout of the NLRP3 inflammasome can be seen as a new therapeutic strategy for slowing down central nervous system (CNS) aging.

Oligodendrocyte progenitor cells in Alzheimer's disease: from physiology to pathology

Oligodendrocyte progenitor cells (OPCs) play pivotal roles in myelin formation and phagocytosis, communicating with neighboring cells and contributing to the integrity of the blood-brain barrier (BBB). However, under the pathological circumstances of Alzheimer's disease (AD), the brain's microenvironment undergoes detrimental changes that significantly impact OPCs and their functions. Starting with OPC functions, we delve into the transformation of OPCs to myelin-producing oligodendrocytes, the intricate signaling interactions with other cells in the central nervous system (CNS), and the fascinating process of phagocytosis, which influences the function of OPCs and affects CNS homeostasis. Moreover, we discuss the essential role of OPCs in BBB formation and highlight the critical contribution of OPCs in forming CNS-protective barriers. In the context of AD, the deterioration of the local microenvironment in the brain is discussed, mainly focusing on neuroinflammation, oxidative stress, and the accumulation of toxic proteins. The detrimental changes disturb the delicate balance in the brain, impacting the regenerative capacity of OPCs and compromising myelin integrity. Under pathological conditions, OPCs experience significant alterations in migration and proliferation, leading to impaired differentiation and a reduced ability to produce mature oligodendrocytes. Moreover, myelin degeneration and formation become increasingly active in AD, contributing to progressive neurodegeneration. Finally, we summarize the current therapeutic approaches targeting OPCs in AD. Strategies to revitalize OPC senescence, modulate signaling pathways to enhance OPC differentiation, and explore other potential therapeutic avenues are promising in alleviating the impact of AD on OPCs and CNS function. In conclusion, this review highlights the indispensable role of OPCs in CNS function and their involvement in the pathogenesis of AD. The intricate interplay between OPCs and the AD brain microenvironment underscores the complexity of neurodegenerative diseases. Insights from studying OPCs under pathological conditions provide a foundation for innovative therapeutic strategies targeting OPCs and fostering neurodegeneration. Future research will advance our understanding and management of neurodegenerative diseases, ultimately offering hope for effective treatments and improved quality of life for those affected by AD and related disorders.

Autophagy, a critical element in the aging male reproductive disorders and prostate cancer: a therapeutic point of view

Autophagy is a highly conserved, lysosome-dependent biological mechanism involved in the degradation and recycling of cellular components. There is growing evidence that autophagy is related to male reproductive biology, particularly spermatogenic and endocrinologic processes closely associated with male sexual and reproductive health. In recent decades, problems such as decreasing sperm count, erectile dysfunction, and infertility have worsened. In addition, reproductive health is closely related to overall health and comorbidity in aging men. In this review, we will outline the role of autophagy as a new player in aging male reproductive dysfunction and prostate cancer. We first provide an overview of the mechanisms of autophagy and its role in regulating male reproductive cells. We then focus on the link between autophagy and aging-related diseases. This is followed by a discussion of therapeutic strategies targeting autophagy before we end with limitations of current studies and suggestions for future developments in the field.

Escape from senescence: molecular basis and therapeutic ramifications

Cellular senescence constitutes a stress response mechanism in reaction to a plethora of stimuli. Senescent cells exhibit cell-cycle arrest and altered function. While cell-cycle withdrawal has been perceived as permanent, recent evidence in cancer research introduced the so-called escape-from-senescence concept. In particular, under certain conditions, senescent cells may resume proliferation, acquiring highly aggressive features. As such, they have been associated with tumour relapse, rendering senescence less effective in inhibiting cancer progression. Thus, conventional cancer treatments, incapable of eliminating senescence, may benefit if revisited to include senolytic agents. To this end, it is anticipated that the assessment of the senescence burden in everyday clinical material by pathologists will play a crucial role in the near future, laying the foundation for more personalised approaches. Here, we provide an overview of the investigations that introduced the escape-from-senescence phenomenon, the identified mechanisms, as well as the major implications for pathology and therapy. © 2023 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Cell senescence-associated porphyrin metabolism affects the efficacy of aminolevulinic acid-photodynamic diagnosis in bladder cancer

Aminolevulinic acid-photodynamic diagnosis (ALA-PDD) is a promising alternative method to detect cancer cells because of its high specificity and low rate of side effects. Exogenous ALA is administered and accumulates as protoporphyrin IX (PpIX) in cancer cells, which then emit red fluorescence following light irradiation to enable surgeons to accurately identify and remove cancerous tissue. Recent reports suggested that PpIX failed to accumulate in some patients who underwent ALA-PDD. We hypothesized that cell senescence, which is a relatively inactive state, affects porphyrin accumulation in bladder cancer cells. In this study, we evaluated the relationship between cell senescence and porphyrin accumulation in affecting the efficacy of ALA-PDD. First, we utilized three bladder cancer cell lines to evaluate senescence-related indicators and establish a cell senescence model. Then, we identified the differences in porphyrin production and the proteins involved in porphyrin accumulation between old and young cells. We found that compared with young cells, old cells possessed higher concentration of PpIX and had lower ABCG2 expression. The increase in PpIX levels following ABCG2 inhibition is three times higher in old cells than in young cells, suggesting that cell senescence was closely related with porphyrin accumulation in cancer. In conclusion, we found that the efficacy of ALA-PDD and porphyrin accumulation was relatively high in senescent cancer cells and that inhibition of ABCG2 could improve the efficacy of ALA-PDD in young bladder cancer cells.

Molecular mechanisms of cellular senescence in neurodegenerative diseases

Neurodegenerative diseases, such as Alzheimer's and Parkinson's, are characterized by several pathological features, including selective neuronal loss, aggregation of specific proteins, and chronic inflammation. Aging is the most critical risk factor of these disorders. However, the mechanism by which aging contributes to the pathogenesis of neurodegenerative diseases is not clearly understood. Cellular senescence is a cell state or fate in response to stimuli. It is typically associated with a series of changes in cellular phenotypes such as abnormal cellular metabolism and proteostasis, reactive oxygen species (ROS) production, and increased secretion of certain molecules via senescence-associated secretory phenotype (SASP). In this review, we discuss how cellular senescence contributes to brain aging and neurodegenerative diseases, and the relationship between protein aggregation and cellular senescence. Finally, we discuss the potential of senescence modifiers and senolytics in the treatment of neurodegenerative diseases.

Polygenic risk score association with multiple sclerosis susceptibility and phenotype in Europeans

Polygenic inheritance plays a pivotal role in driving multiple sclerosis susceptibility, an inflammatory demyelinating disease of the CNS. We developed polygenic risk scores (PRS) of multiple sclerosis and assessed associations with both disease status and severity in cohorts of European descent. The largest genome-wide association dataset for multiple sclerosis to date (n = 41 505) was leveraged to generate PRS scores, serving as an informative susceptibility marker, tested in two independent datasets, UK Biobank [area under the curve (AUC) = 0.73, 95% confidence interval (CI): 0.72-0.74, P = 6.41 × 10-146] and Kaiser Permanente in Northern California (KPNC, AUC = 0.8, 95% CI: 0.76-0.82, P = 1.5 × 10-53). Individuals within the top 10% of PRS were at higher than 5-fold increased risk in UK Biobank (95% CI: 4.7-6, P = 2.8 × 10-45) and 15-fold higher risk in KPNC (95% CI: 10.4-24, P = 3.7 × 10-11), relative to the median decile. The cumulative absolute risk of developing multiple sclerosis from age 20 onwards was significantly higher in genetically predisposed individuals according to PRS. Furthermore, inclusion of PRS in clinical risk models increased the risk discrimination by 13% to 26% over models based only on conventional risk factors in UK Biobank and KPNC, respectively. Stratifying disease risk by gene sets representative of curated cellular signalling cascades, nominated promising genetic candidate programmes for functional characterization. These pathways include inflammatory signalling mediation, response to viral infection, oxidative damage, RNA polymerase transcription, and epigenetic regulation of gene expression to be among significant contributors to multiple sclerosis susceptibility. This study also indicates that PRS is a useful measure for estimating susceptibility within related individuals in multicase families. We show a significant association of genetic predisposition with thalamic atrophy within 10 years of disease progression in the UCSF-EPIC cohort (P < 0.001), consistent with a partial overlap between the genetics of susceptibility and end-organ tissue injury. Mendelian randomization analysis suggested an effect of multiple sclerosis susceptibility on thalamic volume, which was further indicated to be through horizontal pleiotropy rather than a causal effect. In summary, this study indicates important, replicable associations of PRS with enhanced risk assessment and radiographic outcomes of tissue injury, potentially informing targeted screening and prevention strategies.

Repurposing BCL-2 and Jak 1/2 inhibitors: Cure and treatment of HIV-1 and other viral infections

B cell lymphoma 2 (BCL-2) family proteins are involved in the mitochondrial apoptotic pathway and are key modulators of cellular lifespan, which is dysregulated during human immunodeficiency virus type 1 (HIV-1) and other viral infections, thereby increasing the lifespan of cells harboring virus, including the latent HIV-1 reservoir. Long-lived cells harboring integrated HIV-1 DNA is a major barrier to eradication. Strategies reducing the lifespan of reservoir cells could significantly impact the field of cure research, while also providing insight into immunomodulatory strategies that can crosstalk to other viral infections. Venetoclax is a first-in-class orally bioavailable BCL-2 homology 3 (BH3) mimetic that recently received Food and Drug Administration (FDA) approval for treatment in myeloid and lymphocytic leukemia. Venetoclax has been recently investigated in HIV-1 and demonstrated anti-HIV-1 effects including a reduction in reservoir size. Another immunomodulatory strategy towards reduction in the lifespan of the reservoir is Jak 1/2 inhibition. The Jak STAT pathway has been implicated in BCL-2 and interleukin 10 (IL-10) expression, leading to a downstream effect of cellular senescence. Ruxolitinib and baricitinib are FDA-approved, orally bioavailable Jak 1/2 inhibitors that have been shown to indirectly decay the HIV-1 latent reservoir, and down-regulate markers of HIV-1 persistence, immune dysregulation and reservoir lifespan in vitro and ex vivo. Ruxolitinib recently demonstrated a significant decrease in BCL-2 expression in a human study of virally suppressed people living with HIV (PWH), and baricitinib recently received emergency use approval for the indication of coronavirus disease 2019 (COVID-19), underscoring their safety and efficacy in the viral infection setting. BCL-2 and Jak 1/2 inhibitors could be repurposed as immunomodulators for not only HIV-1 and COVID-19, but other viruses that upregulate BCL-2 anti-apoptotic proteins. This review examines potential routes for BCL-2 and Jak 1/2 inhibitors as immunomodulators for treatment and cure of HIV-1 and other viral infections.

Ependymal cells and neurodegenerative disease: outcomes of compromised ependymal barrier function

Within the central nervous system, ependymal cells form critical components of the blood-cerebrospinal fluid barrier and the cerebrospinal fluid-brain barrier. These barriers provide biochemical, immunological and physical protection against the entry of molecules and foreign substances into the cerebrospinal fluid while also regulating cerebrospinal fluid dynamics, such as the composition, flow and removal of waste from the cerebrospinal fluid. Previous research has demonstrated that several neurodegenerative diseases, such as Alzheimer's disease and multiple sclerosis, display irregularities in ependymal cell function, morphology, gene expression and metabolism. Despite playing key roles in maintaining overall brain health, ependymal barriers are largely overlooked and understudied in the context of disease, thus limiting the development of novel diagnostic and treatment options. Therefore, this review explores the anatomical properties, functions and structures that define ependymal cells in the healthy brain, as well as the ways in which ependymal cell dysregulation manifests across several neurodegenerative diseases. Specifically, we will address potential mechanisms, causes and consequences of ependymal cell dysfunction and describe how compromising the integrity of ependymal barriers may initiate, contribute to, or drive widespread neurodegeneration in the brain.

Nintedanib induces senolytic effect via STAT3 inhibition

Selective removal of senescent cells, or senolytic therapy, has been proposed to be a potent strategy for overcoming age-related diseases and even for reversing aging. We found that nintedanib, a tyrosine kinase inhibitor, selectively induced the death of primary human dermal fibroblasts undergoing RS. Similar to ABT263, a well-known senolytic agent, nintedanib triggered intrinsic apoptosis in senescent cells. Additionally, at the concentration producing the senolytic effect, nintedanib arrested the cell cycle of nonsenescent cells in the G1 phase without inducing cytotoxicity. Interestingly, the mechanism by which nintedanib activated caspase-9 in the intrinsic apoptotic pathway differed from that of ABT263 apoptosis induction; specifically, nintedanib did not decrease the levels of Bcl-2 family proteins in senescent cells. Moreover, nintedanib suppressed the activation of the JAK2/STAT3 pathway, which caused the drug-induced death of senescent cells. STAT3 knockdown in senescent cells induced caspase activation. Moreover, nintedanib reduced the number of senescence-associated β-galactosidase-positive senescent cells in parallel with a reduction in STAT3 phosphorylation and ameliorated collagen deposition in a mouse model of bleomycin-induced lung fibrosis. Consistently, nintedanib exhibited a senolytic effect through bleomycin-induced senescence of human pulmonary fibroblasts. Overall, we found that nintedanib can be used as a new senolytic agent and that inhibiting STAT3 may be an approach for inducing the selective death of senescent cells. Our findings pave the way for expanding the senolytic toolkit for use in various aging statuses and age-related diseases.

Epigenetic clock indicates accelerated aging in glial cells of progressive multiple sclerosis patients

Background

Multiple sclerosis (MS) is a chronic inflammatory neurodegenerative disease of the central nervous system (CNS) characterized by irreversible disability at later progressive stages. A growing body of evidence suggests that disease progression depends on age and inflammation within the CNS. We aimed to investigate epigenetic aging in bulk brain tissue and sorted nuclei from MS patients using DNA methylation-based epigenetic clocks.

Methods

We applied Horvath’s multi-tissue and Shireby’s brain-specific Cortical clock on bulk brain tissue (n = 46), sorted neuronal (n = 54), and glial nuclei (n = 66) from post-mortem brain tissue of progressive MS patients and controls.

Results

We found a significant increase in age acceleration residuals, corresponding to 3.6 years, in glial cells of MS patients compared to controls (P = 0.0024) using the Cortical clock, which held after adjustment for covariates (P_adj = 0.0263). The 4.8-year age acceleration found in MS neurons (P = 0.0054) did not withstand adjustment for covariates and no significant difference in age acceleration residuals was observed in bulk brain tissue between MS patients and controls.

Conclusion

While the findings warrant replication in larger cohorts, our study suggests that glial cells of progressive MS patients exhibit accelerated biological aging.

The role of the complement system in Multiple Sclerosis: A review

The complement system has been involved in the pathogenesis of multiple neuroinflammatory and neurodegenerative conditions. In this review, we evaluated the possible role of complement activation in multiple sclerosis (MS) with a focus in progressive MS, where the disease pathogenesis remains to be fully elucidated and treatment options are limited. The evidence for the involvement of the complement system in the white matter plaques and gray matter lesions of MS stems from immunohistochemical analysis of post-mortem MS brains, in vivo serum and cerebrospinal fluid biomarker studies, and animal models of Experimental Autoimmune Encephalomyelitis (EAE). Complement knock-out studies in these animal models have revealed that this system may have a “double-edge sword” effect in MS. On the one hand, complement proteins may aid in promoting the clearance of myelin degradation products and other debris through myeloid cell-mediated phagocytosis. On the other, its aberrant activation may lead to demyelination at the rim of progressive MS white matter lesions as well as synapse loss in the gray matter. The complement system may also interact with known risk factors of MS, including as Epstein Barr Virus (EBV) infection, and perpetuate the activation of CNS self-reactive B cell populations. With the mounting evidence for the involvement of complement in MS, the development of complement modulating therapies for this condition is appealing. Herein, we also reviewed the pharmacological complement inhibitors that have been tested in MS animal models as well as in clinical trials for other neurologic diseases. The potential use of these agents, such as the C5-binding antibody eculizumab in MS will require a detailed understanding of the role of the different complement effectors in this disease and the development of better CNS delivery strategies for these compounds.

Cognitive Decline in Older People with Multiple Sclerosis—A Narrative Review of the Literature

Several important questions regarding cognitive aging and dementia in older people with multiple sclerosis (PwMS) are the focus of this narrative review: Do older PwMS have worse cognitive decline compared to older people without MS? Can older PwMS develop dementia or other neurodegenerative diseases such as Alzheimer’s disease (AD) that may be accelerated due to MS? Are there any potential biomarkers that can help to determine the etiology of cognitive decline in older PwMS? What are the neural and cellular bases of cognitive aging and neurodegeneration in MS? Current evidence suggests that cognitive impairment in MS is distinguishable from that due to other neurodegenerative diseases, although older PwMS may present with accelerated cognitive decline. While dementia is prevalent in PwMS, there is currently no consensus on defining it. Cerebrospinal fluid and imaging biomarkers have the potential to identify disease processes linked to MS and other comorbidities—such as AD and vascular disease—in older PwMS, although more research is required. In conclusion, one should be aware that multiple underlying pathologies can coexist in older PwMS and cause cognitive decline. Future basic and clinical research will need to consider these complex factors to better understand the underlying pathophysiology, and to improve diagnostic accuracy.

Reactive and Senescent Astroglial Phenotypes as Hallmarks of Brain Pathologies

Astrocytes, as the most abundant glial cells in the central nervous system, are tightly integrated into neural networks and participate in numerous aspects of brain physiology and pathology. They are the main homeostatic cells in the central nervous system, and the loss of astrocyte physiological functions and/or gain of pro-inflammatory functions, due to their reactivation or cellular senescence, can have profound impacts on the surrounding microenvironment with pathological outcomes. Although the importance of astrocytes is generally recognized, and both senescence and reactive astrogliosis have been extensively reviewed independently, there are only a few comparative overviews of these complex processes. In this review, we summarize the latest data regarding astrocyte reactivation and senescence, and outline similarities and differences between these phenotypes from morphological, functional, and molecular points of view. A special focus has been given to neurodegenerative diseases, where these phenotypic alternations of astrocytes are significantly implicated. We also summarize current perspectives regarding new advances in model systems based on astrocytes as well as data pointing to these glial cells as potential therapeutic targets.

Genetically predicted telomere length and multiple sclerosis

BACKGROUND

Previous epidemiological studies have indicated a role for telomere length in multiple sclerosis (MS) severity and phenotype. However, these studies failed to establish the causality between telomere length and MS susceptibility. Hence, we performed two-sample Mendelian randomization (MR) analysis to explore the causal relationship between telomere length and MS susceptibility.

METHODS

We used data of genetic variants associated with leukocyte telomere length as instrumental variables (IVs), which was identified from the largest and latest genome-wide association study (GWAS) from UK Biobank (UKB) with 472,174 participants. Summary data of MS was obtained from the International Multiple Sclerosis Genetics Consortium. We performed two-sample MR analyses using the inverse-variance weighted method as the primary approach. Other MR approaches, including the MR-Egger, the inverse variance weighted (multiplicative random effects), weighted median, simple median, weighted mode-based methods, and Causal Analysis Using Summary Effect estimates (CAUSE), were also conducted to detect the result robustness.

RESULTS

The genetic liability to longer telomere length was associated with a higher risk of MS susceptibility (odds ratio [OR] per one-SD telomere length, 1.91; 95% confidence interval [CI], 1.48-2.47; P = 8.04 × 10^-7). The results remained consistent across multiple sensitivity analyses.

CONCLUSIONS

Our study supports the causal relationship between longer telomere length and increased risk of MS susceptibility.

Efficacy of Disease Modifying Therapies in Progressive MS and How Immune Senescence May Explain Their Failure

The advent of disease modifying therapies (DMT) in the past two decades has been the cornerstone of successful clinical management of multiple sclerosis (MS). Despite the great strides made in reducing the relapse frequency and occurrence of new signal changes on neuroimaging in patients with relapsing remitting MS (RRMS) by approved DMT, it has been challenging to demonstrate their effectiveness in non-active secondary progressive MS (SPMS) and primary progressive MS (PPMS) disease phenotypes. The dichotomy of DMT effectiveness between RRMS and progressive MS informs on distinct pathogeneses of the different MS phenotypes. Conversely, factors that render patients with progressive MS resistant to therapy are not understood. Thus far, age has emerged as the main correlate of the transition from RRMS to SPMS. Whether it is aging and age-related factors or the underlying immune senescence that qualitatively alter immune responses as the disease transitions to SPMS, that diminish DMT effectiveness, or both, is currently not known. Here, we will discuss the role of immune senescence on different arms of the immune system, and how it may explain relative DMT resistance.

Why stem/progenitor cells lose their regenerative potential

Nowadays, it is clear that adult stem cells, also called as tissue stem cells, play a central role to repair and maintain the tissue in which they reside by their self-renewal ability and capacity of differentiating into distinct and specialized cells. As stem cells age, their renewal ability declines and their capacity to maintain organ homeostasis and regeneration is impaired. From a molecular perspective, these changes in stem cells properties can be due to several types of cell intrinsic injury and DNA aberrant alteration (i.e epigenomic profile) as well as changes in the tissue microenviroment, both into the niche and by systemic circulating factors. Strikingly, it has been suggested that aging-induced deterioration of stem cell functions may play a key role in the pathophysiology of the various aging-associated disorders. Therefore, understanding how resident stem cell age and affects near and distant tissues is fundamental. Here, we examine the current knowledge about aging mechanisms in several kinds of adult stem cells under physiological and pathological conditions and the principal aging-related changes in number, function and phenotype that determine the loss of tissue renewal properties. Furthermore, we examine the possible cell rejuvenation strategies. Stem cell rejuvenation may reverse the aging phenotype and the discovery of effective methods for inducing and differentiating pluripotent stem cells for cell replacement therapies could open up new possibilities for treating age-related diseases.

Frailty and falls in people living with multiple sclerosis

OBJECTIVE

To explore the association between frailty and history of falls in people living with multiple sclerosis (MS).

DESIGN

Secondary analysis.

SETTING

University research laboratories in the United States and Israel.

PARTICIPANTS

118 people with relapsing-remitting MS [age=48.9 years (SD=10.0); 74.6% female; expanded disability status scale (EDSS) range=1.0-6.0] were studied in this cross-sectional analysis.

INTERVENTION

Not applicable.

MAIN OUTCOMES

A frailty index was calculated from 40 health deficits by following standard validated procedures. The number of falls (12-month history) was recorded.

RESULTS

Overall, 33.9%, 29.7%, and 36.4% of participants were classified as non-frail, moderately frail, and severely frail, respectively. The frailty index was significantly correlated (ρ=0.37, p<0.001) with higher scores on the EDSS. In univariable negative binomial regression analysis, the frailty index was associated with a higher number of falls (IRR=3.33, 95%CI[1.85-5.99], p<0.001). After adjustment for age, gender and EDSS, frailty remained strongly associated with history of falls (IRR=2.78, 95%CI[1.51-5.10], p=0.001).

CONCLUSION

The current study identifies a significant relationship between frailty and history of falls in MS, independent of age, gender, and disease severity. These findings support the notion that frailty is a syndrome related to, but independent of, disability in MS.

Age at Disease Onset Associates With Oxidative Stress, Neuroinflammation, and Impaired Synaptic Plasticity in Relapsing-Remitting Multiple Sclerosis

Age at onset is the main risk factor for disease progression in patients with relapsing-remitting multiple sclerosis (RR-MS). In this cross-sectional study, we explored whether older age is associated with specific disease features involved in the progression independent of relapse activity (PIRA). In 266 patients with RR-MS, the associations between age at onset, clinical characteristics, cerebrospinal fluid (CSF) levels of lactate, and that of several inflammatory molecules were analyzed. The long-term potentiation (LTP)-like plasticity was studied using transcranial magnetic stimulation (TMS). Older age was associated with a reduced prevalence of both clinical and radiological focal inflammatory disease activity. Older patients showed also increased CSF levels of lactate and that of the pro-inflammatory molecules monocyte chemoattractant protein 1 (MCP-1)/CCL2, macrophage inflammatory protein 1-alpha (MIP-1α)/CCL3, and interleukin (IL)-8. Finally, TMS evidenced a negative correlation between age and LTP-like plasticity. In newly diagnosed RR-MS, older age at onset is associated with reduced acute disease activity, increased oxidative stress, enhanced central inflammation, and altered synaptic plasticity. Independently of their age, patients with multiple sclerosis (MS) showing similar clinical, immunological, and neurophysiological characteristics may represent ideal candidates for early treatments effective against PIRA.

Characteristics of secondary progressive multiple sclerosis: Disease activity and provision of care in Germany - A registry-based/multicentric cohort study

BACKGROUND

The tailored immunomodulatory treatment strategy for secondary progressive multiple sclerosis (SPMS) depends on disease activity.

OBJECTIVE

To assess the real-world situation in monitoring disease activity in SPMS patients and to identify associations of resulting subgroups with demographics, symptomatology, and therapy METHODS: This study included 4,263 SPMS patients from the German MS register (GMSR). For the classification into 'active' and 'inactive' according to relapse activity and MRI findings during the year prior to the latest clinical visit, we used the following definitions: active - gadolinium enhancing (Gd+)/new T2 lesions or ≥1 relapse, inactive - neither Gd+/new T2 lesions nor relapses. The active, inactive, and unclassifiable patients were compared in terms of clinical data, socio-demographics, symptomatology, healthcare, and DMT.

RESULTS

Classification was possible for 1,513 (35.5%) SPMS patients, with 467 classified as active and 1,046 as inactive. For the classification, MRI data was available for 33.2% of the 4,263 patients. Higher MRI frequencies were observed for younger patients (OR 1.22 [1.12,1.33] per 10 years) with short disease duration (OR 1.19 [1.09, 1.30] per 10 years) (p < 0.001).

CONCLUSION

MRI coverage was low, especially in elderly SPMS patients. Roughly one third of the SPMS patients presented markers of disease activity in the last year. Overall, the clinical differences (concerning symptomatology and care) between patients with active and inactive SPMS were small.

Improved assessment of overall health in variably aged murine models of Multiple Sclerosis with a novel frailty index tool

The experimental autoimmune encephalomyelitis (EAE) model is the most commonly used animal model of Multiple Sclerosis (MS). However, phenotypic characterization of mice based on the traditional 5-point clinical paralysis scale does not fully capture disease progression. The frailty index (FI) conceptualizes frailty as the accumulation of health deficits and it is widely used to assess overall health in aging humans and pre-clinical models. Here we adapted an established mouse FI tool for use in EAE mice and determined whether this could evaluate general signs of health in variably aged female EAE mice. The EAE-Clinical FI included 34 items related to clinical signs and deficits characteristic of aging and MS. This tool clearly showed more detailed EAE progression and severity at all ages, highlighting changes in systems other than motor paralysis measured with the traditional 5-point paralysis scale. When we induced disease at 3- and 6-months-of-age, mice showed typical EAE clinical manifestations with peak disease severity between 17-19 days post-induction and mean frailty scores of 0.36 ± 0.04 (3-month-old) and 0.43 ± 0.05 (6-month-old). By contrast, disease severity peaked after 14 days in 12-month-old mice. They showed atypical signs including wobbling, early belly drag, and splayed hindlegs that were better captured with the EAE-Clinical FI. Peak frailty scores also were higher than those of younger animals (0.54 ± 0.04). As MS most often develops in young to middle-aged people, this new tool may have significant value for use in EAE animal studies as first step towards translation to people with MS.

Remyelination therapies for multiple sclerosis: optimizing translation from animal models into clinical trials

Introduction: Multiple sclerosis (MS) is the most common inflammatory disease of the central nervous system (CNS). Demyelination, the main pathology in MS, contributes to clinical symptoms and long-term neurological deficits if left untreated. Remyelination, the natural repair of damaged myelin by cells of the oligodendrocyte lineage, occurs in MS, but eventually fails in most patients as they age. Encouraging timely remyelination can restore axon conduction and minimize deficits.Areas covered: We discuss and correlate human MS pathology with animal models, propose methods to deplete resident oligodendrocyte progenitor cells (OPCs) to determine whether mature oligodendrocytes support remyelination, and review remyelinating agents, mechanisms of action, and available clinical trial data.Expert opinion: The heterogeneity of human MS may limit successful translation of many candidate remyelinating agents; some patients lack the biological targets necessary to leverage current approaches. Development of therapeutics for remyelination has concentrated almost exclusively on mobilization of innate OPCs. However, mature oligodendrocytes appear an important contributor to remyelination in humans. Limiting the contribution of OPC mediated repair in models of MS would allow the evaluation of remyelination-promoting agents on mature oligodendrocytes. Among remyelinating reagents reviewed, only rHIgM22 targets both OPCs and mature oligodendrocytes.

What telomeres teach us about MS

While the precise mechanisms driving progressive forms of MS are not fully understood, patient age has clear impact on disease phenotype. The very young with MS have high relapse rates and virtually no progressive disease, whereas older patients tend to experience more rapid disability accumulation with few relapses. Defining a patient's biological age may offer more precision in determining the role of aging processes in MS phenotype and pathophysiology than just working with an individual's birthdate. The most well recognized measurement of an individual's "biological clock" is telomere length (TL). While TL may differ across tissue types in an individual, most cells TL correlate well with leukocyte TL (LTL), which is the most common biomarker used for aging. LTL has been associated with risk for aging related diseases and most recently with higher levels of disability and brain atrophy in people living with MS. LTL explains 15% of the overall association of chronological age with MS disability level. While LTL may be used just as a biomarker of overall somatic aging processes, triggering of the DNA damage response by telomere attrition leads to senescence pathways that are likely highly relevant to a chronic autoimmune disease. Considering reproductive aging factors, particularly ovarian aging in women, which correlates with LTL and oocyte telomere length, may complement measurements of somatic aging in understanding MS progression. The key to stopping non-relapse related progression in MS might lie in targeting pathways related to biological aging effects on the immune and nervous systems.

The Senolytic Drug JQ1 Removes Senescent Cells via Ferroptosis

BACKGROUND

Ferroptosis is an iron-dependent, non-apoptotic programmed cell death. Cellular senescence contributes to aging and various age-related diseases through the expression of a senescence-associated secretory phenotype (SASP). Senescent cells are often resistant to ferroptosis via increased ferritin and impaired ferritinophagy. In this study, we investigated whether treatment with JQ1 could remove senescent cells by inducing ferroptosis.

METHODS

Senescence of human dermal fibroblasts was induced in vitro by treating the cells with bleomycin. The senolytic effects of JQ1 were evaluated using a SA-β gal assay, annexin V analysis, cell counting kit-8 assay, and qRT-PCR. Ferroptosis following JQ1 treatment was evaluated with qRT-PCR and BODIPY staining.

RESULTS

At a certain range of JQ1 concentrations, JQ1 treatment reduced the viability of bleomycin-treated cells (senescent cells) but did not reduce that of untreated cells (non-senescent cells), indicating that JQ1 treatment can selectively eliminate senescent cells. JQ1 treatment also decreased SASP expression only in senescent cells. Subsequently, JQ1 treatment reduced the expression of ferroptosis-resistance genes in senescent cells. JQ1 treatment induced lipid peroxidation in senescent cells but not in non-senescent cells.

CONCLUSION

The data indicate that JQ1 can eliminate senescent cells via ferroptosis. This study suggests ferroptosis as a new mechanism of senolytic therapy.

Stopping disease-modifying therapy in relapsing and progressive multiple sclerosis

PURPOSE OF REVIEW

To assess the reasons for considering discontinuation of disease-modifying therapies (DMTs)in patients with multiple sclerosis (MS). Relevant aspects of the natural history, pathology, and immunology are analyzed.

RECENT FINDINGS

A number of retrospective observational studies in aggregate indicate that stopping DMTs may be attempted in older individuals with stable disease. Prognostic factors have been identified informing about the risk of recurrence of disease activity after DMT discontinuation.

SUMMARY

Several clinical scenarios provide a rationale to stop DMTs in people with MS. Cumulative evidence has been gathered recently allowing us to more precisely weigh the risks against the benefits. This information aids in the decision process.

Molecular mechanisms and cardiovascular implications of cancer therapy-induced senescence

Cancer treatment has been associated with accelerated aging that can lead to early-onset health complications typically experienced by older populations. In particular, cancer survivors have an increased risk of developing premature cardiovascular complications. In the last two decades, cellular senescence has been proposed as an important mechanism of premature cardiovascular diseases. Cancer treatments, specifically anthracyclines and radiation, have been shown to induce senescence in different types of cardiovascular cells. Additionally, clinical studies identified increased systemic markers of senescence in cancer survivors. Preclinical research has demonstrated the potential of several approaches to mitigate cancer therapy-induced senescence. However, strategies to prevent and/or treat therapy-induced cardiovascular senescence have not yet been translated to the clinic. In this review, we will discuss how therapy-induced senescence can contribute to cardiovascular complications. Thereafter, we will summarize the current in vitro, in vivo, and clinical evidence regarding cancer therapy-induced cardiovascular senescence. Then, we will discuss interventional strategies that have the potential to protect against therapy-induced cardiovascular senescence. To conclude, we will highlight challenges and future research directions to mitigate therapy-induced cardiovascular senescence in cancer survivors.

Senescent Microglia: The Key to the Ageing Brain?

Ageing represents the single biggest risk factor for development of neurodegenerative disease. Despite being such long-lived cells, microglia have been relatively understudied for their role in the ageing process. Reliably identifying aged microglia has proven challenging, not least due to the diversity of cell populations, and the limitations of available models, further complicated by differences between human and rodent cells. Consequently, the literature contains multiple descriptions and categorisations of microglia with neurotoxic phenotypes, including senescence, without any unifying markers. The role of microglia in brain homeostasis, particularly iron storage and metabolism, may provide a key to reliable identification.

Effects of Late-Life Caloric Restriction on Age-Related Alterations in the Rat Cortex and Hippocampus

Background: A major problem of aging is the disruption of metabolic homeostasis. This is particularly relevant in the brain where it provokes neurodegeneration. Caloric restriction is a physiologic intervention known to delay the deleterious consequences of aging in several species ranging from yeast to mammals. To date, most studies on experimental models have started this dietary intervention from weaning, which is very difficult to be translated to human beings. Here, we study the effects of a more realistic dietary regimen in rats, starting at an advanced age and lasting for six months. Methods: we analyzed in the cortex and hippocampus, the proteins involved in the energetic balance of the cells, cholesterol metabolism, oxidative stress response, inflammation, synaptic impairment, and brain trophism. Results: our results suggest that caloric restriction in late life can revert only some age-related changes studied here.