Thymosins in multiple sclerosis and its experimental models: moving from basic to clinical application

Background: Multiple sclerosis (MS) afflicts more than 2.5 million individuals worldwide and this number is increasing over time. Within the past years, a great number of disease-modifying treatments have emerged; however, efficacious treatments and a cure for MS await discovery. Thymosins, soluble hormone-like peptides produced by the thymus gland, can mediate immune and non-immune physiological processes and have gained interest in recent years as therapeutics in inflammatory and autoimmune diseases. Methods: Pubmed was searched with no time constraints for articles using a combination of the keywords "thymosin/s" or "thymus factor/s" AND "multiple sclerosis", mesh terms with no language restriction. Results: Here, we review the state-of-the-art on the effects of thymosins on MS and its experimental models. In particular, we describe what is known in this field on the roles of thymosin-alpha 1 (T alpha 1) and -beta 4 (T beta 4) as potential anti-inflammatory as well as neuroprotective and remyelinating molecules and their mechanisms of action. Conclusion: Based on the data that T alpha 1 and T beta 4 act as anti-inflammatory molecules and as inducers of myelin repair and neuronal protection, respectively, a possible therapeutic application in MS for T alpha 1 and T beta 4 alone or combined with other approved drugs may be envisaged. This approach is reasonable in light of the current clinical usage of T alpha 1 and data demonstrating the safety, tolerability and efficacy of T beta 4 in clinical practice.