Age-related changes in the cellular composition and epithelial organization of the mouse trachea. Mus musculus

We report here senescent changes in the structure and organization of the mucociliary pseudostratified epithelium of the mouse trachea and the main stem bronchi. We confirm previous reports of the graduate appearance of age-related, gland-like structures (ARGLS) in the submucosa, espeically in the intercartilage regions and carina. Immunohistochemistry shows these structures contain ciliated and secretory cells and Krt5+ basal cells, but not the myoepithelial cells or ciliated ducts typical of normal submucosal glands. Data suggests they arise de novo by budding from teh surface epithelium rather than by delayted growth of small or cryptic submucosal glands. In old mice the surface epithelium contains fewer cells per unit length than in young mice and the proportion of Krt5+, p63+ basal cells is reduced in both males and females. However, there appears to be no significant difference in the ability of basal stem cells isolated from individual young and old mice to form clonal tracheospheres in culture or in the ability of the pithelium to repair after damage by inhaled sulfur dioxide. Gene expression analysis by Affymetrix microarray and quantitative PCR, as well as immunohistochemistry and flow sorting studies, are consistent with low-grade chronic inflammation in the tracheas of old versus young mice. The significance of these changes for ARGL formation are not clear since several treatments that induce acute inflammation in young mice did not result in budding of the surface epithelium. Overall design: Total RNA from distal tracheas and carinas of four young (2 month) and four older (14 month) C57Bl/6 female mice was extracted using QIAshredder and RNeasy Micro Kits (QIAGEN). The quality was checked with a 2100 Bioanalyzer (Agilent Technologies). Total RNA was processed using Ambion MessageAmpTM Premier by the Duke Microarray Facility. Standard Affymetrix protocols and Affymetrix GeneChip® Mouse Genome 430 2.0 Array chips were used to generate .cel files.