A COMPARISON BETWEEN THE EPITHELIAL TIGHT JUNCTION MORPHOLOGY OF HUMAN EXTRAPULMONARY BRONCHI AND RAT TRACHEA

Animal models have been used to investigate the involvement of epithel ial tight junctions in the pathogenesis of human airway disease. Howev er, no previous study has compared the tight junction morphologies of human and animal species in order to relate findings in animal models to human disease. In the present study, we therefore undertook a compr ehensive quantitative evaluation of tight junction morphology, to dete rmine what similarities or differences may exist in rat and human airw ays. Human tissue was obtained from grossly and histologically normal extrapulmonary bronchi from lungs resected for pulmonary tumour (n=8); rat tracheal epithelium was acquired from Sprague-Dawley specific pat hogen-free animals (n=12). The tight junction morphologies of the two species were compared with respect to junctional depth, number of stra nds and junctional complexity. The basic architectural arrangement of the tight junctions in both species was found to be similar; however, tight junctions in rat tissues were less deep, comprised fewer strands , and had fewer strand interconnections compared with those in the hum an samples. The number of strands per interconnection was similar in t he two species. We conclude that, in spite of a general similarity of rat and human airway epithelial tight junctions, there are specific qu antitative details of morphology which need to be considered when atte mpting to extrapolate to the human the results of studies of airway ep ithelial permeability conducted in the rat. The precise biological sig nificance of these differences, as yet, remains unclear.