The thymus, a primary lymphoid organ, provides a complex environment essential for the generation of the T lymphocyte repertoire. Thymic alterations occur during life, either in the context of thymic involution during aging, or in the pathophysiological context of Myasthenia Gravis (MG). These changes involve complex regulatory networks, in which microRNAs (miRNAs) are key players.
In this article, a Franco-American team involving researchers from the Myology Centre for Research of the Institute of Myology analyzed the role of miRNAs in the maturation and differentiation of thymocytes supported by thymic epithelial cells. They compared the data in the literature concerning the role of mouse thymic miRNAs with the original data obtained from a study of human thymic miRnome. The authors identified a set of highly expressed miRNAs defined as ThymiR and studied the expression of miRNAs in infants versus adults to determine which ones are associated with human thymic involution.
Thymic changes are also commonly seen in MG, an autoimmune disease that results in the production of anti-acetylcholine receptor antibodies (AChR) that lead to muscle weakness. There are alterations such as thymoma in patients with late-onset MG and hyperplasia with ectopic germinal centers (GC) in patients with early onset (EOMG). Expression of thymic mRNA has been studied in AChR-MG patients in both thymoma-associated MG (TAMG) and EMOG, and their function across their mRNA targets has been studied. Most thymic miRNAs deregulated in EOMG are associated with the development of GC, such as miR-7, miR-24, miR-139, miR-143, miR-145, miR-146, miR-150, miR-452, miR – 548 or thymic inflammation, such as miR-125b, miR-146 or miR-29. Understanding these pathways can provide therapeutic targets or biomarkers of disease manifestations.
