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

Current challenges in secondary progressive multiple sclerosis: diagnosis, activity detection and treatment

Approximately 50% diagnosed with relapsing-remitting multiple sclerosis (RRMS) transition to secondary progressive multiple sclerosis (SPMS) within 20 years following disease onset. However, early diagnosis of SPMS and effective treatment remain important clinical challenges. The lack of established diagnostic criteria often leads to delays in identifying SPMS. Also, there are limited disease-modifying therapies (DMTs) available for progressive forms of MS, and these therapies require evidence of disease activity to be initiated. This review examines the challenges in diagnosing SPMS at an early stage and summarizes the current and potential use of biomarkers of disease progression in clinical practice. We also discuss the difficulties in initiating the DMTs indicated for active SPMS (aSPMS), particularly in patients already undergoing treatment with DMTs that suppress disease activity, which may mask the presence of inflammatory activity required for the therapy switch. The article also addresses the DMTs available for both active and non-active SPMS, along with the clinical trials that supported the approval of DMTs indicated for aSPMS or relapsing MS in Europe, which includes aSPMS. We also offer insights on when discontinuing these treatments may be appropriate.

Cellular rejuvenation protects neurons from inflammation-mediated cell death

In multiple sclerosis (MS), inflammation of the central nervous system results in demyelination, neuroaxonal injury, and cell death. However, the molecular signals responsible for injury and cell death in neurons are not fully characterized. Here, we profile the transcriptome of retinal ganglion cells (RGCs) in experimental autoimmune encephalomyelitis (EAE) mice. Pathway analysis identifies a transcriptional signature reminiscent of aged RGCs with some senescent features, with a comparable signature present in neurons from patients with MS. This is supported by immunostaining demonstrating alterations to the nuclear envelope, modifications in chromatin marks, and accumulation of DNA damage. Transduction of RGCs with an Oct4-Sox2-Klf4 adeno-associated virus (AAV) to rejuvenate the transcriptome enhances RGC survival in EAE and improves visual acuity. Collectively, these data reveal an aging-like phenotype in neurons under pathological neuroinflammation and support the possibility that rejuvenation therapies or senotherapeutic agents could offer a direct avenue for neuroprotection in neuroimmune disorders.

Assessment of relationships between epigenetic age acceleration and multiple sclerosis: a bidirectional mendelian randomization study

BACKGROUND

The DNA methylation-based epigenetic clocks are increasingly recognized for their precision in predicting aging and its health implications. Although prior research has identified connections between accelerated epigenetic aging and multiple sclerosis, the chronological and causative aspects of these relationships are yet to be elucidated. Our research seeks to clarify these potential causal links through a bidirectional Mendelian randomization study.

METHODS

This analysis employed statistics approaches from genome-wide association studies related to various epigenetic clocks (GrimAge, HannumAge, PhenoAge, and HorvathAge) and multiple sclerosis, utilizing robust instrumental variables from the Edinburgh DataShare (n = 34,710) and the International Multiple Sclerosis Genetics Consortium (including 24,091 controls and 14,498 cases). We applied the inverse-variance weighted approach as our main method for Mendelian randomization, with additional sensitivity analyses to explore underlying heterogeneity and pleiotropy.

RESULTS

Using summary-based Mendelian randomization, we found that HannumAge was associated with multiple sclerosis (OR = 1.071, 95%CI:1.006-1.140, p = 0.033, by inverse-variance weighted). The results suggest that an increase in epigenetic age acceleration of HannumAge promotes the risk of multiple sclerosis. In reverse Mendelian randomization analysis, no evidence of a clear causal association of multiple sclerosis on epigenetic age acceleration was identified.

CONCLUSIONS

Our Mendelian randomization analysis revealed that epigenetic age acceleration of HannumAge was causally associated with multiple sclerosis, and provided novel insights for further mechanistic and clinical studies of epigenetic age acceleration-mediated multiple sclerosis.

Epigenetic Clock: DNA Methylation as a Marker of Biological Age and Age-Associated Diseases

Age is one of the key criteria of human health used in practical medicine to predict the risk of common chronic diseases. However, biological age, which reflects the state of an individual organism, functional capabilities, social well-being, and risk of premature death from various causes, often does not coincide with chronological age. To determine biological age of a particular individuals and the rate of their aging, specific panels of DNA methylation markers called "epigenetic clock" (EC) were proposed. This review summarizes the data about the main types of ECs developed to date and their key characteristics. We described the results of works studying individual aging rates in common age-associated diseases and outlined main directions, development of which could expand application of ECs in fundamental and practical medicine. There is no doubt that revealing complex mechanisms underlying interaction between the rate of epigenetic aging and the risk of age-associated diseases could play a key role for prediction and early diagnosis, as well as for the development of preventive measures that could delay onset of the disease.

Smouldering-Associated Worsening in Multiple Sclerosis: An International Consensus Statement on Definition, Biology, Clinical Implications, and Future Directions

Despite therapeutic suppression of relapses, multiple sclerosis (MS) patients often experience subtle deterioration, which extends beyond the definition of "progression independent of relapsing activity." We propose the concept of smouldering-associated-worsening (SAW), encompassing physical and cognitive symptoms, resulting from smouldering pathological processes, which remain unmet therapeutic targets. We provide a consensus-based framework of possible pathological substrates and manifestations of smouldering MS, and we discuss clinical, radiological, and serum/cerebrospinal fluid biomarkers for potentially monitoring SAW. Finally, we share considerations for optimizing disease surveillance and implications for clinical trials to promote the integration of smouldering MS into routine practice and future research efforts. ANN NEUROL 2024;96:826-845.

The lung-brain axis in multiple sclerosis: Mechanistic insights and future directions

Multiple sclerosis is a chronic inflammatory demyelinating disease of the central nervous system with progressive lifelong disability. Current treatments are particularly effective at the early inflammatory stage of the disease but associate with safety concerns such as increased risk of infection. While clinical and epidemiological evidence strongly support the role of a bidirectional communication between the lung and the brain in MS in influencing disease risk and severity, the exact processes underlying such relationship appear complex and not fully understood. This short review aims to summarize key findings and future perspectives that might provide new insights into the mechanisms underpinning the lung-brain axis in MS.

Physiological aging and inflammation-induced cellular senescence may contribute to oligodendroglial dysfunction in MS

Aging affects all cell types in the CNS and plays an important role in CNS diseases. However, the underlying molecular mechanisms driving these age-associated changes and their contribution to diseases are only poorly understood. The white matter in the aging brain as well as in diseases, such as Multiple sclerosis is characterized by subtle abnormalities in myelin sheaths and paranodes, suggesting that oligodendrocytes, the myelin-maintaining cells of the CNS, lose the capacity to preserve a proper myelin structure and potentially function in age and certain diseases. Here, we made use of directly converted oligodendrocytes (dchiOL) from young, adult and old human donors to study age-associated changes. dchiOL from all three age groups differentiated in an comparable manner into O4 + immature oligodendrocytes, but the proportion of MBP + mature dchiOL decreased with increasing donor age. This was associated with an increased ROS production and upregulation of cellular senescence markers such as CDKN1A, CDKN2A in old dchiOL. Comparison of the transcriptomic profiles of dchiOL from adult and old donors revealed 1324 differentially regulated genes with limited overlap with transcriptomic profiles of the donors' fibroblasts or published data sets from directly converted human neurons or primary rodent oligodendroglial lineage cells. Methylome analyses of dchiOL and human white matter tissue samples demonstrate that chronological and epigenetic age correlate in CNS white matter as well as in dchiOL and resulted in the identification of an age-specific epigenetic signature. Furthermore, we observed an accelerated epigenetic aging of the myelinated, normal appearing white matter of multiple sclerosis (MS) patients compared to healthy individuals. Impaired differentiation and upregulation of cellular senescence markers could be induced in young dchiOL in vitro using supernatants from pro-inflammatory microglia. In summary, our data suggest that physiological aging as well as inflammation-induced cellular senescence contribute to oligodendroglial pathology in inflammatory demyelinating diseases such as MS.

Roles of Epigenetics and Glial Cells in Drug-Induced Autism Spectrum Disorder

Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by severe deficits in social communication and interaction, repetitive movements, abnormal focusing on objects, or activity that can significantly affect the quality of life of the afflicted. Neuronal and glial cells have been implicated. It has a genetic component but can also be triggered by environmental factors or drugs. For example, prenatal exposure to valproic acid or acetaminophen, or ingestion of propionic acid, can increase the risk of ASD. Recently, epigenetic influences on ASD have come to the forefront of investigations on the etiology, prevention, and treatment of this disorder. Epigenetics refers to DNA modifications that alter gene expression without making any changes to the DNA sequence. Although an increasing number of pharmaceuticals and environmental chemicals are being implicated in the etiology of ASD, here, we specifically focus on the molecular influences of the abovementioned chemicals on epigenetic alterations in neuronal and glial cells and their potential connection to ASD. We conclude that a better understanding of these phenomena can lead to more effective interventions in ASD.

The Impact of Aging on Multiple Sclerosis

PURPOSE OF REVIEW

Multiple sclerosis (MS) is a chronic, immune-mediated demyelinating disorder of the central nervous system. Age is one of the most important factors in determining MS phenotype. This review provides an overview of how age influences MS clinical characteristics, pathology, and treatment.

RECENT FINDINGS

New methods for measuring aging have improved our understanding of the aging process in MS. New studies have characterized the molecular and cellular composition of chronic active or smoldering plaques in MS. These lesions are important contributors to disability progression in MS. These studies highlight the important role of immunosenescence and the innate immune system in sustaining chronic inflammation. Given these changes in immune function, several studies have assessed optimal treatment strategies in aging individuals with MS. MS phenotype is intimately linked with chronologic age and immunosenescence. While there are many unanswered questions, there has been much progress in understanding this relationship which may lead to more effective treatments for progressive disease.

Senescence marker p16INK4a expression in patients with multiple sclerosis

OBJECTIVES

Telomere attrition is associated with disability accumulation and brain atrophy in multiple sclerosis (MS). Downstream of telomere attrition is cellular senescence. We sought to determine differences in the cellular senescence marker p16INK4a expression between MS and healthy control participants and the association of p16INK4a expression with MS disability and treatment exposure.

METHODS

Patients meeting diagnostic criteria for MS and healthy controls were recruited for a cross-sectional pilot study. RNA was extracted from peripheral blood mononuclear cells (PBMCs) and p16INK4a expression levels were measured using qRT PCR. Spearman correlation coefficients and regression models were applied to compare expression levels to chronological age, assess case control differences, and determine associations with clinical outcome measures.

RESULTS

Fifty-two participants with MS (67 % female, ages 25-70) and 38 healthy controls (66 % female, ages 23-65) were included. p16INK4a levels were not linearly correlated with chronological age in MS (rhos = -0.01, p = 0.94) or control participants (rhos = 0.02, p = 0.92). Higher median p16INK4a levels were observed in the >50-year age group for MS (0.25, IQR 0.14-0.35) vs. controls (0.12, IQR 0.05-0.15) and in this age group B cell depletion therapy was associated with lower expression levels. p16INK4a expression was not associated with any of the measured MS disability outcomes.

DISCUSSION

Caution is needed with using p16INK4a expression level from PBMCs as an aging biomarker in MS participants, given lack of correlation with chronological age or large associations with clinical outcomes.

Biological aging in multiple sclerosis

Multiple sclerosis (MS) is most likely to adopt a progressive clinical course during middle age or beyond, and the number of older adults with MS is steadily increasing. Developing new strategies to manage progressive forms of MS, which do not respond to currently available disease-modifying therapies (DMTs), will require a deeper understanding of the mechanisms by which biological aging interacts with pathogenic pathways to propel disability accumulation. In experimental autoimmune encephalomyelitis (EAE), a widely used preclinical mouse model of MS, middle-aged animals experience a more severe and protracted clinical course than their younger counterparts. This exacerbated disease course is accompanied by persistent neuroinflammation. Clinical studies of age-related biomarkers, such as telomere length, senescence markers, and DNA methylation, suggest that biological aging is accelerated in people with MS compared with age- and sex-matched healthy controls. Furthermore, distinguishing biological age from chronological may afford more precision in determining aging effects in MS. Here we review the current literature on aging biology and its impact on MS pathogenesis. Future research on this topic may lead to the development of novel biomarkers and senotherapy agents that slow neurological decline in people with progressive MS by targeting relevant aging-related pathways.

Smoking affects epigenetic ageing of lung bronchoalveolar lavage cells in Multiple Sclerosis

BACKGROUND

A compelling body of evidence implicates cigarette smoking and lung inflammation in Multiple Sclerosis (MS) susceptibility and progression. Previous studies have reported epigenetic age (DNAm age) acceleration in blood immune cells and in glial cells of people with MS (pwMS) compared to healthy controls (HC).

OBJECTIVES

We aimed to examine biological ageing in lung immune cells in the context of MS and smoking.

METHODS

We analyzed age acceleration residuals in lung bronchoalveolar lavage (BAL) cells, constituted of mainly alveolar macrophages, from 17 pwMS and 22 HC in relation to smoking using eight DNA methylation-based clocks, namely AltumAge, Horvath, GrimAge, PhenoAge, Zhang, SkinBlood, Hannum, Monocyte clock as well as two RNA-based clocks, which capture different aspects of biological ageing.

RESULTS

After adjustment for covariates, five epigenetic clocks showed significant differences between the groups. Four of them, Horvath (Padj = 0.028), GrimAge (Padj = 4.28 × 10-7), SkinBlood (Padj = 0.001) and Zhang (Padj = 0.02), uncovered the sole effect of smoking on ageing estimates, irrespective of the clinical group. The Horvath, SkinBlood and Zhang clocks showed a negative impact of smoking while GrimAge detected smoking-associated age acceleration in BAL cells. On the contrary, the AltumAge clock revealed differences between pwMS and HC and indicated that, in the absence of smoking, BAL cells of pwMS were epigenetically 5.4 years older compared to HC (Padj = 0.028). Smoking further affected epigenetic ageing in BAL cells of pwMS specifically as non-smoking pwMS exhibited a 10.2-year AltumAge acceleration compared to pwMS smokers (Padj = 0.0049). Of note, blood-derived monocytes did not show any MS-specific or smoking-related AltumAge differences. The difference between BAL cells of pwMS smokers and non-smokers was attributable to the differential methylation of 114 AltumAge-CpGs (Padj < 0.05) affecting genes involved in innate immune processes such as cytokine production, defense response and cell motility. These changes functionally translated into transcriptional differences in BAL cells between pwMS smokers and non-smokers.

CONCLUSIONS

BAL cells of pwMS display inflammation-related and smoking-dependent changes associated to epigenetic ageing captured by the AltumAge clock. Future studies examining potential confounders, such as the distribution of distinct BAL myeloid cell types in pwMS compared to control individuals in relation to smoking may clarify the varying performance and DNAm age estimations among epigenetic clocks.

The NHANES Biological Age Index demonstrates accelerated aging in MS patients

BACKGROUND

Chronological age is associated with disability accumulation in multiple sclerosis (MS). Biological age may give more precise estimates of aging pathways associations with MS severity. Both normal aging and accelerated aging from MS may negatively impact disease course. Multi-marker indices of aging, such as the NHANES biological age index (BAI), may be more robust than single biomarkers in capturing biological age and are strongly associated with mortality risk and aging-related diseases.

OBJECTIVE

We sought to investigate whether the NHANES BAI, utilizing readily available measures in the clinic, captures accelerating aging and correlates with disability in MS participants.

METHODS

We conducted a prospective, cross-sectional case-control pilot study. Consecutive patients who met the 2017 McDonald's Criteria for MS were recruited from May 2020 to May 2022 along with age-similar healthy controls. BAI components included blood pressure, FEV1, serum creatinine, C-reactive protein, blood-urea nitrogen, albumin, alkaline phosphatase, cholesterol, CMV IgG, and hemoglobin A1c. The index was calculated using the Klemara and Doubal method. Spearman correlation and multivariable linear regression models were used to assess the association between BAI and MS clinical outcomes.

RESULTS

A total of 51 MS (68.6% female) and 38 control (68.4% female) participants were recruited. BAI correlated with chronological age (CA) in MS (r2=0.90,p<0.0001) and control participants (r2 =0.87,p<0.0001). The mean BAI was 1.4 years older than CA in MS participants (range +15 to -10.5 years) and 2.2 years younger in control participants (range +11.2 to -14.1 years). In unadjusted Spearman analyses, BAI correlated with the timed 25-foot walk (T25FW, rhos=0.31, p = 0.045) and symbol digit modalities test (SDMT rhos = 0.35, p = 0.018). In a multivariable regression model, a 5-year older BAI was associated with a 1.2-point lower score on SDMT (95%CI -2.2 to -0.25, p = 0.014).

CONCLUSIONS

MS participants were biologically older than their own chronological age and age-similar controls. In this modest-sized pilot sample, there was strongest correlation for MS outcome measures between BAI and the SDMT. These results support further study of the BAI as a marker of biological age variability in MS.

Sex, aging and immunity in multiple sclerosis and experimental autoimmune encephalomyelitis: An intriguing interaction

Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system (CNS) with a profound neurodegenerative component early in the disease pathogenesis. Age is a factor with a well-described effect on the primary disease phenotype, namely, the relapsing-remitting vs. the primary progressive disease. Moreover, aging is a prominent factor contributing to the transition from relapsing-remitting MS (RRMS) to secondary progressive disease. However, sex also seems to, at least in part, dictate disease phenotype and evolution, as evidenced in humans and in animal models of the disease. Sex-specific gene expression profiles have recently elucidated an association with differential immunological signatures in the context of experimental disease. This review aims to summarize current knowledge stemming from experimental autoimmune encephalomyelitis (EAE) models regarding the effects of sex, either independently or as a factor combined with aging, on disease phenotype, with relevance to the immune system and the CNS.

The Role of Epigenetics in Neuroinflammatory-Driven Diseases

Neurodegenerative disorders are characterized by the progressive loss of central and/or peripheral nervous system neurons. Within this context, neuroinflammation comes up as one of the main factors linked to neurodegeneration progression. In fact, neuroinflammation has been recognized as an outstanding factor for Alzheimer's disease (AD), amyotrophic lateral sclerosis (ALS), Parkinson's disease (PD), and multiple sclerosis (MS). Interestingly, neuroinflammatory diseases are characterized by dramatic changes in the epigenetic profile, which might provide novel prognostic and therapeutic factors towards neuroinflammatory treatment. Deep changes in DNA and histone methylation, along with histone acetylation and altered non-coding RNA expression, have been reported at the onset of inflammatory diseases. The aim of this work is to review the current knowledge on this field.