Ageing is a major risk factor for developing many neurodegenerative diseases. Cellular senescence is a homeostatic biological process that has a key role in driving ageing. There is evidence that senescent cells accumulate in the nervous system with ageing and neurodegenerative disease and may predispose a person to the appearance of a neurodegenerative condition or may aggravate its course. Research into senescence has long been hindered by its variable and cell-type specific features and the lack of a universal marker to unequivocally detect senescent cells. Recent advances in senescence markers and genetically modified animal models have boosted our knowledge on the role of cellular senescence in ageing and age-related disease. The aim now is to fully elucidate its role in neurodegeneration in order to efficiently and safely exploit cellular senescence as a therapeutic target. Here, we review evidence of cellular senescence in neurons and glial cells and we discuss its putative role in Alzheimer’s disease, Parkinson’s disease and multiple sclerosis and we provide, for the first time, evidence of senescence in neurons and glia in multiple sclerosis, using the novel GL13 lipofuscin stain as a marker of cellular senescence.

Recent studies have revealed extensive neocortical pathology in multiple sclerosis (MS). The hippocampus is a unique archaeocortical structure understudied in MS. It plays a central role in episodic and anterograde memory—the most frequently impaired cognitive modalities in MS. This histopathological study aimed to investigate inflammatory demyelination and neurodegenerative changes in the MS archaeocortex. A detailed quantitative analysis was performed on hippocampal autopsy tissue from 45 progressive MS cases and seven controls. Forty‐one lesions were identified in 28 of the 45 hippocampal MS‐blocks examined, with percentage area of demyelination averaging 30.4%. The majority of lesions were chronic and subpially or subependymally located. Compared to controls, neuronal numbers were decreased by 27% in CA1 and 29.7% in CA3‐2. Furthermore, the size of neurones was decreased by 17.4% in CA1. There was evidence of gross hippocampal atrophy with a 22.3% reduction in the average cross‐sectional area, which correlated with neuronal loss. Our study provides evidence of substantial archaeocortical pathology largely resembling patterns seen in the neocortex and suggests that hippocampal involvement could contribute to memory impairments often seen in MS.

Introduction and objective: Monoclonal antibodies targeting the calcitonin gene-related peptide pathway (anti-CGRP mAbs) have shown promising efficacy in randomised clinical trials for the prevention of episodic and chronic migraine, but no head-to-head comparisons with established treatments are available. We aimed to examine absolute differences in benefit-risk ratios between anti-CGRP mAbs, topiramate and propranolol for the prevention of episodic migraine and between anti-CGRP mAbs, topiramate and onabotulinumtoxinA for the prevention of chronic migraine using a likelihood to help versus harm analysis. Methods: The number of patients needed to be treated for a patient to achieve ≥ 50% reduction in migraine days (NNTB_50%) was used as an effect size metric of efficacy. The number of patients needed to be treated for a patient to experience an adverse event that led to treatment discontinuation (NNTH_D-AE) was used as a measure of risk. Likelihood to help versus harm values – which are the ratios of NNTH:NNTB – were calculated using data from phase 3 randomised clinical trials. Results: All agents tested were more likely to be beneficial than harmful (likelihood to help versus harm > 1) with the exception of topiramate at 200 mg per day for the prevention of episodic migraine. Anti-CGRP mAbs in all tested doses had higher LHH values than propranolol or topiramate for episodic migraine and onabotulinumtoxinA or topiramate for chronic migraine prevention. Fremanezumab had the highest LHH ratio in episodic migraine and galcanezumab in chronic migraine. Conclusion: This analysis showed that anti-CGRP mAbs exhibit a more favourable benefit-risk ratio than established treatments for episodic and chronic migraine. Head-to-head studies are needed to confirm these results.