Shin-ichiro Kitajiri

Compartmentalization established by claudin-11-based tight junctions in stria vascularis is required for hearing through generation of endocochlear potential

Claudins are cell adhesion molecules working at tight junctions (TJs) that are directly involved in compartmentalization in multicellular organisms. The cochlea includes a rather peculiar compartment filled with endolymph. This compartment is characterized by high K+ concentration (∼150 mM) and a positive endocochlear potential (∼90 mV; EP), both indispensable conditions for cochlear hair cells to transduce acoustic stimuli to electrical signals. These conditions are thought to be generated by the stria vascularis, which is adjacent to the endolymph compartment. The stria vascularis itself constitutes an isolated compartment delineated by two epithelial barriers, marginal and basal cell layers. Because TJs of basal cells are primarily composed of claudin-11, claudin-11-deficient (Cld11-/-) mice were generated with an expectation that the compartmentalization in stria vascularis in these mice would be affected. Auditory brainstem response measurements revealed that Cld11-/- mice suffered from deafness; although no obvious gross morphological malformations were detected in Cld11-/- cochlea, freeze-fracture replica electron microscopy showed that TJs disappeared from basal cells of the stria vascularis. In good agreement with this, tracer experiments showed that the basal cell barrier was destroyed without affecting the marginal cell barrier. Importantly, in the endolymph compartment of Cld11-/- cochlea, the K+ concentration was maintained around the normal level (∼150 mM), whereas the EP was suppressed down to ∼30 mV. These findings indicated that the establishment of the stria vascularis compartment, especially the basal cell barrier, is indispensable for hearing ability through the generation/maintenance of EP but not of a high K+ concentration in the endolymph.

Radixin deficiency causes deafness associated with progressive degeneration of cochlear stereocilia

Ezrin/radixin/moesin (ERM) proteins cross-link actin filaments to plasma membranes to integrate the function of cortical layers, especially microvilli. We found that in cochlear and vestibular sensory hair cells of adult wild-type mice, radixin was specifically enriched in stereocilia, specially developed giant microvilli, and that radixin-deficient (Rdx − / −) adult mice exhibited deafness but no obvious vestibular dysfunction. Before the age of hearing onset (∼2 wk), in the cochlea and vestibule of Rdx − / − mice, stereocilia developed normally in which ezrin was concentrated. As these Rdx − / − mice grew, ezrin-based cochlear stereocilia progressively degenerated, causing deafness, whereas ezrin-based vestibular stereocilia were maintained normally in adult Rdx − / − mice. Thus, we concluded that radixin is indispensable for the hearing ability in mice through the maintenance of cochlear stereocilia, once developed. In Rdx − / − mice, ezrin appeared to compensate for radixin deficiency in terms of the development of cochlear stereocilia and the development/maintenance of vestibular stereocilia. These findings indicated the existence of complicate functional redundancy in situ among ERM proteins.

Analysis of the ‘angulin’ proteins LSR, ILDR1 and ILDR2 – tricellulin recruitment, epithelial barrier function and implication in deafness pathogenesis

Summary Tricellular tight junctions (tTJs) seal the extracellular space at tricellular contacts (TCs), where the corners of three epithelial cells meet. To date, the transmembrane proteins tricellulin and lipolysis-stimulated lipoprotein receptor (LSR) are known to be molecular components of tTJs. LSR recruits tricellulin to tTJs, and both proteins are required for the full barrier function of epithelial cellular sheets. In the present study, we show that two LSR-related proteins, immunoglobulin-like domain-containing receptor (ILDR) 1 and ILDR2, are also localized at TCs and recruit tricellulin. At least one of LSR, ILDR1 and ILDR2 was expressed in most of the epithelial tissues in mice. The expressions of LSR, ILDR1 and ILDR2 were generally complementary to each other, although LSR and ILDR1 were co-expressed in some epithelia. ILDR1 was required for the establishment of a strong barrier of the epithelium, similar to LSR, when introduced into cultured epithelial cells, whereas ILDR2 provided a much weaker barrier. We further analyzed human ILDR1, mutations in which cause a familial deafness, DFNB42, and found that most DFNB42-associated ILDR1 mutant proteins were defective in recruitment of tricellulin. We also found that tricellulin mutant proteins associated with another familial deafness, DFNB49, were not recruited to TCs by ILDR1. These findings show the heterogeneity of the molecular organization of tTJs in terms of the content of LSR, ILDR1 or ILDR2, and suggest that ILDR1-mediated recruitment of tricellulin to TCs is required for hearing. Given their common localization at epithelial cell corners and recruitment of tricellulin, we propose to designate LSR, ILDR1 and ILDR2 as angulin family proteins.

Relief of Post-Tonsillectomy Pain by Release of Lidocaine From Fibrin Glue

Objectives Pain inevitably develops after resection of the palatine tonsil (tonsillectomy). Therefore, we applied a mixture of lidocaine and fibrin glue to the tonsillar fossae immediately after tonsillectomy and evaluated its analgesic effects.

Ectopic Pituitary Adenoma With Malignant Transformation

We report here a case of ectopic pituitary adenoma with malignant transformation after repeated relapses. First, an ectopic pituitary adenoma producing follicle-stimulating hormone was found in the nasal cavity extending to the frontal cranial fossa. Despite repeated surgical resections of the tumor, it recurred three times in 2 years. The tumor gradually showed cellular atypia, mitosis, and necrosis. Immunohistochemical analyses revealed that the expressions of proliferating cell nuclear antigen and MIB-1 increased progressively. Moreover, the expression of p53 was detected at the second recurrence. Finally, at the third recurrence the tumor showed dissemination to the subarachnoid space and multiple metastases in the brain. The patient died of the tumor 10 months after the last resection. These findings indicate that the ectopic pituitary adenoma became malignant. To our knowledge, this is the first report on malignant transformation of ectopic pituitary adenoma. It is important to know that ectopic pituitary adenomas show malignant transformation and that the above parameters (proliferating cell nuclear antigen, MIB-1, and p53) may be useful indicators of the malignant potential of both ectopic and sellar pituitary tumors.

Deafness in occludin-deficient mice with dislocation of tricellulin and progressive apoptosis of the hair cells

ABSTRACT Occludin is the first identified protein in the tight junction (TJ), but its function has remained for the most part obscure. TJs have been demonstrated to play important roles in the inner ear function, and occludin is expressed in all the epithelial TJs in the inner ear. Thus, we examined the inner ears of occludin-deficient (Occ−/−) mice. Although inner ears initially developed normally in Occ−/− mice, apoptosis occurs in hair cells in the organ of Corti around day 12 after birth, and deafness develops. Since hair cell degeneration was not observed in cochlear explant cultures of Occ−/− mice, environmental changes were considered to be the trigger of cell death. As for the vestibular system, both the morphologies and functions are normal in Occ−/− mice. These phenotypes of Occ−/− mice are very similar with those of claudin-14 or claudin-9 deficient mice, leading us to speculate on the existence of imbalance induced by TJ abnormalities, such as localized ionic components. Moreover, the occludin deficiency led to dislocalization of tricellulin, a gene responsible for human deafness DFNB49. The deafness in Occ−/− mice may be due to this dislocalization of tricellulin.

Increased expression of integrin β-4 in papillary thyroid carcinoma with gross lymph node metastasis

Although the prognosis is generally good for patients with papillary thyroid carcinoma, gross nodal metastasis of carcinoma has a poor prognosis. It is necessary to clarify how carcinoma progresses to gross nodal metastasis in order to establish a cure. The adhesion molecule integrin β‐4 is considered to be related to cell migration and metastasis in many carcinomas. In the present study, we examined integrin β‐4 expression in 65 cases of human papillary thyroid carcinoma using immunohistochemical methods. Expression of integrin β‐4 was found in all papillary carcinomas, but in few normal thyrocytes. Interestingly, integrin β‐4 expression in the carcinomas with gross (˘3 cm) lymph node metastasis was significantly higher than that in carcinomas with small (<3 cm) or no lymph node metastasis. These results suggest that integrin β‐4 expression in thyroid carcinoma may play a role in the development of gross lymph node metastasis of papillary carcinomas.

Transnasal bamboo foreign body lodged in the sphenoid sinus

Transnasal sphenoid sinus foreign body is a rare condition. We report a very rare case of transnasal bamboo foreign body lodged in the sphenoid sinus without damages to the orbital wall or skull base. A 69-year-old man fell down onto a bamboo stick, which snapped after penetrating his face through the right nostril. CT demonstrated that the bamboo stick stuck into the middle meatus, penetrated the ethmoid sinus just medial to the lamina papyracea and reached to the sphenoid sinus. No abnormal findings were detected in the orbit or skull base. The foreign body was removed from the nasal cavity without any complication. The endoscope was useful for evaluating possible injuries in the orbit and skull base and confirming the absence of residual foreign bodies.

Radiosensitive hemangiopericytoma in the soft palate

Hemangiopericytomas are uncommon neoplasms of vascular origin, and rarely arise in the pharynx. We report a case of a 78-year-old female with hemangiopericytoma in her soft palate exhibiting prominent radiosensitivity. Hemangiopericytomas are considered to be radioresistant and wide local excision is a treatment of choice, but their nature is widely variable. In treating aggressive hemangiopericytomas, radiation therapy can be selected.

Disruption and restoration of cell–cell junctions in mouse vestibular epithelia following aminoglycoside treatment

The intracellular junction complexes, which consist of tight junctions (TJ), adherens junctions (AJ), and desmosomes, mediate cell-cell adhesion in epithelial cells. E-cadherin, which is a major component of AJ, plays a role not only in the maintenance of cell-cell junctions, but also in repressing cell proliferation. In this study, we examined changes of E-cadherin expression in mouse vestibular epithelia following local application of neomycin using immunohistochemistry and western blotting, and morphology of cell-cell junctions by transmission electron microscopy (TEM). Immunohistochemistry and western blotting revealed down-expression of E-cadherin and its consecutive recovery. TEM demonstrated temporal disruption of cell-cell junctions. Morphology of cell-cell junctions was more rapidly restored than recovery of E-cadherin expression. Transient disruption of cell-cell junctions and down-expression of E-cadherin is a rational response for the deletion of dying hair cells, and may be associated with a limited capacity for cell proliferations in mammalian vestibular epithelia following their rapid restoration.