The Neurovascular Niche: A Gathering Venue for Neuroinflammation and Remyelination in Multiple Sclerosis

In the central nervous system (CNS), the tissue microenvironment is continuously monitored and regulated to secure the unobstructed function of neurons and of their networks. This is a key function of the neurovascular niche (NVN), which is the interface between the cells of the nervous tissue and the cells and the content of blood vessels. It is enabled by the Blood-Brain Barrier, a structure formed by endothelial and perivascular cells, extracellular matrix, and astrocytes, and is manifested by the limited surveillance of the CNS from blood-derived cells. Multiple sclerosis (MS) is a devastating degenerative disorder, in which the myelin sheaths that enwrap neuronal axons are destroyed, leading, over time, to neurological symptoms. MS has a strong immunological component which is targeted in most of the current disease-modifying treatments. Nevertheless, regenerative interventions aiming at enhancing and restoring the endogenous remyelination potential of the CNS, driven by the abundant Oligodendrocyte Progenitor Cells (OPCs), have not been successfully developed so far. Here, we will review key information on the structure of the NVN, and we will summarize the evidence on the role of inflammation in the emergence and the progress of MS, with a focus on the active response of OPCs. We will also present recent experimental evidence on the role of less investigated cellular elements of the NVN, such as pericytes and platelets, in the regulation of OPCs. Finally, we will discuss current and future treatments for MS.