Vestibular malformation in mice lacking Na-K-2Cl cotransporter 1 and expression of Na-K-2Cl cotransporter 1 in human vestibular end organs

Abstract

CONCLUSION: The Na-K-2Cl cotransporter-1 (NKCCl) may be essential for the maintenance and functioning of the vestibular morphology in mice and it is strongly expressed in human vestibular end organs. OBJECTIVE: NKCCl is a member of the cation-coupled chloride transporter which participates in salt transport and cell volume regulation in diverse tissues. NKCCl-deficient mice exhibit deafness, and show structural alterations in the cochlea. In addition to hearing loss, NKCCl-deficient mice show a shaker-waltzer behavior, which suggests a vestibular system defect. In this study we investigated the morphology of the vestibular system of NKCCl-deficient mice and also evaluated whether NKCCl mRNA and its protein are expressed in human vestibular end organs. MATERIAL AND METHODS: NKCCl-deficient and wild-type mice aged 4-5 weeks were sacrificed. Their heads were cut in the midsagittal plane, fixed and decalcified. For light microscopy, 5-microm sections were cut and stained with hematoxylin-eosin. Human vestibular end organs were harvested during acoustic tumor surgery via a translabyrinthine approach. Some of these end organs were used for total mRNA extraction and the remainder for immunostaining. Reverse transcriptase polymerase chain reaction and immunostaining were performed for NKCCl. RESULTS: The scala media of the cochleae of the NKCCl-deficient mice had collapsed but the bony labyrinth appeared unaffected. However, the semicircular canals (SCCs) were much smaller than those in the wild-type mice. Furthermore, the SCCs were completely missing in some NKCCl-deficient mice. NKCCl mRNA was expressed in both the human macula and crista ampullaris, and its protein was expressed mainly in the transitional and dark cell areas of the human crista ampullaris.