The role of occludin in vascular barrier function in vivo: do we need to re-examine?

While these findings are novel and objective, we feel it may be necessary to interpret the data with caution regarding to equating the decrease of occludin expression with blood-brain barrier dysfunction in this and other related research. Since its discovery by Shoichiro Tsukita, a pioneer in the field of tight junction, most of the data in literature about the causal role of occludin in barrier function are from in vitro experiments. [...]occludin-deficient mice do not display a perturbation of barrier function, with a complex pathophysiological and inexplicable phenotype [2] which even disappointed its discoverer Shoichiro Tsukita. [...]few reports regarding the in vivo barrier function of occludin mainly focused on epithelial cells [3]. In another recent report dedicated to the memory of Dr. Shoichiro Tsukita, occludin deficiency in mice causes deafness while not affecting the tight junction structure or barrier [5]. [...]due to the lack of vascular barrier disruption in occludin-deficient mice, additional in vivo animal experiments may be needed to make the conclusions for those studying the role of occludin in vascular barrier function in vivo and those using occludin expression as an indicator of blood-brain barrier function more reliable.