Researchers have developed a compound based on the thyroid hormone T3 that is able to repair damaged myelin in the brain of mice, a discovery that holds promise for healing myelin loss in patients with multiple sclerosis (MS), results of an early study reveal.
The compound combines a brain-penetrating agent and a chemical mimic of T3, and may be a future remyelination therapy delivered specifically to the central nervous system (CNS) — brain and spinal cord — with few side effects.
The study “Myelin repair stimulated by CNS-selective thyroid hormone action” was published in the journal JCI Insight.
During development, the active form of the thyroid hormone T3 promotes the formation of myelin-producing cells at the CNS; these cells are called oligodendrocytes. As a result, the myelin sheath around nerve fibers grows in the presence of this hormone.
However, using thyroid hormone has not been eyed as a potential remyelination therapy given its unwanted side-effects when delivered systemically (into the bloodstream) and affecting the entire body.
That’s why scientists at Oregon Health & Science University (OHSU), in collaboration with researchers from other institutions, devised a novel approach to address this limitation.
The team used sobetirome, a thyromimetic — a molecule that mimics T3, binding to and activating its natural receptor in the body.
Sobetirome is devoid of the adverse side effects associated with excess thyroid hormone, “and unique among thyromimetics for its ability to cross the blood-brain barrier and distribute to the CNS from a systemic dose” researchers wrote. The blood-brain barrier is a protective barrier between the brain’s blood vessels and the brain tissue.