Cellular senescence and failure of myelin repair in multiple sclerosis.

Remyelination is a physiological response to demyelinating events aiming to restore saltatory conduction and preserve axonal integrity. Resident oligodendrocyte precursor cells (OPC) of the CNS tissue under appropriate conditions are mobilized to proliferate, migrate, and differentiate, in order to produce new myelin sheaths in the demyelinated lesion. In multiple sclerosis (MS), the most common immune-mediated demyelinating disease, remyelination efficiency declines with increasing age and disease duration. As myelin regeneration attempts in clinical trials so far are scarce, and have been met with limited success, the need to explore new remyelinating strategies is more compelling. Recently, ageing and cellular senescence have been implicated in the pathophysiology of a number of neurodegenerative diseases, including multiple sclerosis. Evidence on OPC senescence brings forward the possibility of exploiting cellular senescence as a possible target for promoting the endogenous remyelinating capacity of the CNS. Here we discuss the data indicating how cellular senescence affects remyelination, and the putative benefits to be drawn through the use of senolytic or senomorphic therapies targeting senescent cell populations in MS.

Mitochondrial Homeostasis and Cellular Senescence.

Cellular senescence refers to a stress response aiming to preserve cellular and, therefore, organismal homeostasis. Importantly, deregulation of mitochondrial homeostatic mechanisms, manifested as impaired mitochondrial biogenesis, metabolism and dynamics, has emerged as a hallmark of cellular senescence. On the other hand, impaired mitostasis has been suggested to induce cellular senescence. This review aims to provide an overview of homeostatic mechanisms operating within mitochondria and a comprehensive insight into the interplay between cellular senescence and mitochondrial dysfunction.