Search

The thymus is a vital organ for functional immune systems, and is the site of T cell development, which plays a central role in cellular immune defenses. Unlike other major organs, the thymus is highly dynamic in size and structure. It shrinks immediately upon bacterial infection, aging, pregnancy, mental stress, nutritional deficiency, and more. The reduction in size and function of the thymus during such biological events is called thymic involution or thymic atrophy; thymic involution is a particularly important issue because dysfunctional T cell immunity increases the risks of tumorigenesis and infectious diseases. However, the molecular mechanisms underlying thymic involution remain obscure. Our recent study indicated that blood vessels are remodeled during thymic involution that occurs upon aging, estradiol-treatment, or nutritional deficiency. We also found that prostanoid synthesis is induced during thymic involution. Treatment with non-steroidal anti-inflammatory drugs (NSAIDs), aspirin or etodolac, at least partially inhibited thymic involution-induced remodeling of the blood vessels, suggesting that prostanoids are involved in blood vessel remodeling. Our results revealed the potential role of blood vessel remodeling during thymic involution, which can lead to biological stress-induced immunosenescence.

The surgical replacement of human vessels using fresh allografts (homograft) has been reported as useful means. Nevertheless, little is known about preservation effect and immunological consequences using TC199 solution. In this study, defined inbred strains of rats were used. The aorta was extracted from Buffalo rats and preserved for 1, 2, and 3 weeks in TC199 solution at 4 degrees C. The preserved graft was then implanted into the Buffalo rats heterotopically, in the abdominal aorta, in the autotransplant group (AUTO) and into the Lewis rat in the allotransplant group (ALLO). The graft patency and histology including immunohistochemical stain (IgG, IgM, and C3 complement) were assessed at 2 weeks after transplantation. In AUTO, the patency was 100% with grafts 1 and 2 weeks' preservation, and 80% with 3 weeks' preservation. In the ALLO, patency was 100% with grafts with one week's preservation, 80% in those with 2 weeks' preservation and 0% those with in 3 weeks' preservation. Histology revealed that fibroblasts and endothelial cells were significantly deteriorated in 3 weeks' preservation in auto transplantation, however, they were well-maintained in 2 weeks' preservation. In the allo-transplantation group, histological deterioration began after 2 weeks preservation. Immunohistochemical staining showed significant deposits of IgG, IgM and C3 in ALLO. Significant infiltration of antibodies was seen in deteriorated tissue due to prolongation of the preservation periods. These results suggested that freshly preserved allograft was antigenic and 2 weeks preservation using TC199 solution was possible in the rat model.