Recent Advances on Immunosuppressive Drugs and Remyelination Enhancers for the Treatment of Multiple Sclerosis

Mammalian nervous systems depend crucially on myelin sheaths covering the axons. In the central nervous system, myelin sheaths consist of lipid structures that are generated from the membrane of oligodendrocytes (OL). These sheaths allow fast nerve transmission, protect axons and provide them metabolic support. In response to specific traumas or pathologies, these lipid structures can be destabilized and generate demyelinating lesions. Multiple sclerosis (MS) is an example of a demyelinating disease in which the myelin sheaths surrounding the nerve fibers of the brain and spinal cord are damaged. MS is the leading cause of neurological disability in young adults in many countries, and its incidence has been increasing in recent decades. Related to its etiology, it is known that MS is an autoimmune and inflammatory CNS disease. However, there are no effective treatments for this disease and the immunomodulatory therapies that currently exist have proven limited success since they only delay the progress of the disease. Nowadays, one of the main goals in MS research is to find treatments which allow the recovery of neurological disabilities due to demyelination. To this end, different approaches, such as modulating intracellular signaling or regulating the lipid metabolism of OLs, are being considered. Here, in addition to immunosuppressive or immunomodulatory drugs that reduce the immune response against myelin sheaths, we review a diverse group of drugs that promotes endogenous remyelination in MS patients and their use may be interesting as potential therapeutic agents in MS disease. To this end, we compile specific treatments against MS that are currently in the market with remyelination strategies that have entered into human clinical trials for future reparative MS therapies. The method used in this study is a systematic literature review on PubMed, Web of Science and Science Direct databases up to May 31, 2020. To narrow down the search results in databases, more specific keywords, such as "myelin sheath", "remyelination", "demyelination", "oligodendrocyte" and "lipid synthesis" were used to focus the search. We preferred papers published after January 2015, but did not exclude earlier seminal papers.