Extra Thymi and Lesser Thymic Involution with Age in Long-Lived Naked Mole-Rats

Naked mole-rats show little decline of function until late life, are highly resistant to cancer, and live nine times longer than similarly sized rodent species. An important aspect of immune system aging in mammals is the atrophy of the thymus. Thymocytes created in the bone marrow migrate to the thymus where they mature into T cells of the adaptive immune system. As active thymic tissue is replaced with fat, in the process of thymic involution, this supply of T cells declines. Absent reinforcements, the T cell population of the body becomes ever more damaged, malfunctioning, exhausted, and senescent. Researchers here show that not only do naked mole-rats have much delayed thymic involution, but they also exhibit the presence of multiple thymi. Here, we provide the first characterization of the naked mole rat (NMR) thymus. We discovered that naked mole rats have an additional pair of cervical thymi. This is an unexpected finding as mammals, including humans and mice, as a rule, have only one bilateral thymus. Cervical thymi can occasionally be detected in mice, but their frequency is rare and they have unilateral appearance. Similarly, rare ectopic cervical human thymi had been reported in children. In contrast, cervical thymi are a principal component of NMR ontogenesis. Interestingly, among vertebrates, chickens have seven, sharks five, and amphibians three thymi. It is tempting to speculate that the presence of additional thymi in the naked mole rat may contribute...
Source: Fight Aging! - Category: Research Authors: Tags: Daily News Source Type: blogs