Vestibular semicircular canal epithelium of the rat in culture on filter support: polarity and barrier properties

The inner ear of mammals contains the vestibular apparatus which is involve d in the maintenance of posture and balance. The tubular structure of the a pparatus is bathed by the potassium-rich endolymph and sodium-rich perilymp h in the luminal and abluminal compartments, respectively. The luminal comp artment is lined by a continuous epithelium with islets of receptor organs, which separates the luminal from the abluminal compartment. The present wo rk focuses on the epithelium, without the receptor organs, and shows that i t can be reconstituted in culture. The epithelium from 4-day-old Wistar rat s was grown on microporous membranes. High transepithelial electrical resis tances (4000-6000 Ohm.cm(2)) were achieved after 4-8 days in culture. The e pithelium was characterized by the presence of cytokeratin, ZO-1 protein, o ccludin, and the presence of tight junctions and kinocilia. The transepithe lial resistance of the cell monolayer withstood endolymph/perilymph dual ba thing when the apical pole of the cells was in contact with endolymph, but collapsed in the reverse configuration. Weak but statistically highly signi ficant basal to apical rubidium (Rb-86) transport was observed. These findi ngs show that this epithelium maintains its in vivo polarity and could enha nce the potassium composition of endolymph up to maturity. This new culture model, in which dual bathing is possible, should enable further in vitro s tudies of the sensory vestibular epithelia.