Cell renewal and gene expression in the trachea of hamster at different ages

The tracheal mucosa of the Syrian golden hamster has been extensively employed as a model system for respiratory tract cell renewal, injury, and carcinogenesis. However, baseline cell kinetic data are not available for normal juvenile and adolescent animals in which the mucosa and cartilage are rapidly enlarging. The objective of this research was to elucidate alterations in cell kinetics, epithelial morphology, and gene expression in the trachea of hamsters at different ages. Cell kinetics were examined by 3H-thymidine labeling indices, morphology by light and electron microscopic examination, and gene expression by slot blot analysis. Results showed that mucosal epithelium of the young and adolescent hamster undergoes cyclic necrosis and cell shedding, exposing portions of the elastic basal lamina. Epithelial shedding was associated with hyperplasia and squamous metaplasia. Additionally, the labeling indices of mucosal epithelial cells and chondroblasts also exhibited variable patterns which were associated with a cyclic pattern of expression of c-fos and c-erbB2 proto-oncogenes and epidermal growth factor receptor.