Morphologic Change of the Vestibular Organ in the Na+-K+-2Cl- Cotransporter Deficiency Mouse

ABSTRACT

BACKGROUND AND OBJECTIVES: The Na+-K+-2Cl- cotransporter-1 (NKCC1) is a member of the cation-coupled chloride transporter that participates in salt transport and cell volume regulation in diverse tissues. NKCC1 deficient mice exhibit deafness, and have structural alterations in the cochlea. In addition to hearing loss, NKCC1-deficient mice show a shaker-waltzer behavior, which suggests a vestibular system defect. This study investigated the morphology of the vestibular system of NKCC1-deficient mice. In addition, this study evaluated whether NKCC1 mRNA and its protein are expressed in human vestibular end organs. MATERIALS AND METHOD: NKCC1-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 m sections were cut, and stained with hematoxylin and eosin. Human vestibular end organs were harvested during acoustic tumor surgery via translabyrinthine approach. Some of these end organs were used for the total mRNA extraction and the remainder was used for immunostaining. RT-PCR was performed for NKCC1. RESULTS: The scala media of the cochlear of the NKCC1-deficient mice were collapsed but the bony labyrinth of the cochlea appeared unaffected. However, the semicircular canals (SCCs) were much smaller than those in the wild type. Furthermore, the SCCs were completely missing in some NKCC1-deficient mice. NKCC1 mRNA was expressed in both human macula and crista ampullaris and its protein was expressed mainly in the transitional and dark cell area of the human crista ampullaris. CONCLUSION: NKCC1 may be essential for maintaining the vestibular morphology and its function in mice and NKCC1 is well expressed in human vestibular end organs.