Swallowing-related muscle inflammation and fibrosis induced by a single dose of radiation exposure in mice.

BACKGROUND: Although radiotherapy is commonly used to treat head and neck cancer, it may lead to radiation-associated dysphagia (RAD). There are various causes of RAD, however, the mechanism has not yet been fully identified. Currently, the only effective treatment for RAD is rehabilitation. Additionally, there are few available animal models of RAD, necessitating the development of new models to establish and evaluate RAD treatments. We hypothesize that radiation-induced neck muscle fibrosis could be one of the causes of RAD due to impairment of laryngeal elevation. Therefore, in this study, we focused on the changes in inflammation and fibrosis of the strap muscles (Sternohyoid, Sternothyroid, and Thyrohyoid muscles) after a single-dose irradiation. This research aims to provide a reference animal model for future studies on RAD. RESULTS: Compared to control mice, those treated with 72-Gy, but not 24-Gy, irradiation had significantly increased tumor necrosis factor-α (TNF-α) (p < 0.01) and α-smooth muscle actin (αSMA) (p < 0.05) expression at 10 days and significantly increased expression levels of motif chemokine ligand-2 (CCL2), α-SMA, tumor growth factor-ß1 (TGF-ß1), type1 collagen, and interleukin-1ß (IL-1ß) (p < 0.05) in the muscles at 1 month by real-time PCR analysis. The results of immunohistochemistry showed that the deposition of type 1 collagen gradually increased in extracellular space after radiation exposure, and the positive area was significantly increased at 3 months compared to non-irradiated control. CONCLUSIONS: A single dose of 72-Gy irradiation induced significant inflammation and fibrosis in the strap muscles of mice at 1 month, with immunohistochemical changes becoming evident at 3 months. This cervical irradiation-induced fibrosis model holds potential for establishing an animal model for RAD in future studies. LEVEL OF EVIDENCE: N/A.

Distribution of glucocorticoid receptors and 11ß-hydroxysteroid dehydrogenase isoforms in the human inner ear.

HYPOTHESIS: Glucocorticoids (GCs) are widely used as a therapeutic modality for the inner ear disorders including Ménière's disease (MD). The concentration of GCs in the target cells is known to be regulated by 11ß-hydroxysteroid dehydrogenase (11ß-HSD), an enzyme complex responsible for the conversion of hormonally active cortisol into inactive cortisone. There is no morphologic indication of glucocorticoid receptors (GRs) and 11ß-HSD isoforms (11ß-HSD1 and 2) in human inner ear. OBJECTIVES: The objectives of this study are to determine whether GRs and the isoforms of 11ß-HSD are present in human inner ear tissues and to reveal their precise distribution. STUDY DESIGN: This study investigated the expression of GRs and 11ß-HSD isoforms (11ß-HSD1 and 2) in the human inner ear. METHODS: In humans, immunostaining of GRs, 11ß-HSD1, and 11ß-HSD2 was performed in the stria vascularis (SV) and the vestibular tissues, whereas in the cochlear tissues except for the SV, only GRs were investigated. RESULTS: Immunoreactivity of GRs was detected in the SV, outer hair cells, inner hair cell, spiral ligament, Reissner's membrane, vestibular hair cells, vestibular nerve, transitional cells, and dark cells of the crista ampullaris. 11ß-HSD1 was observed in the SV, the apical area of the vestibular hair cells, the transitional cells, and the dark cells. However, no immunoreactivity of 11ß-HSD2 was observed. CONCLUSION: Those data indicate that different local steroid regulation by GRs and the isoforms of 11ß-HSD is present in various parts of the human inner ear tissues and that the tissues are a direct therapeutic target of glucocorticoids in the inner ear diseases.

Distribution of glucocorticoid receptors and 11 beta-hydroxysteroid dehydrogenase isoforms in the rat inner ear.

11ß-hydroxysteroid dehydrogenase (11ß-HSD) is an enzyme complex responsible for the conversion of hormonally active cortisol to inactive cortisone, and two isoforms of the enzyme (11ß-HSD1 and 11ß-HSD2) have been cloned and characterized. An immunohistochemical study was performed to determine the precise distribution of glucocorticoid receptors (GRs) and the isoforms of 11ß-HSD in the rat (postnatal day 1, 4, 10, and adult). Immunoreactivity of GRs was detected in the stria vascularis (SV), the outer hair cells (OHCs), the inner hair cells (IHCs), the spiral ligament (SLig), the spiral limbus (SLib), the spiral ganglion cells (SGCs), Reissner's membrane (RM), the cochlear nerve (CN), the vestibular hair cells (VHCs), the dark cells (DCs), and the vestibular nerve (VN) in the rats. Immunostaining of 11ß-HSD1 was observed in almost all the tissues in the cochlea and the vestibule except SLig, SLib, SGCs, CN, VHCs, and VN during all developmental stages, whereas, immunoreactivity of 11ß-HSD2 was not detected in any of the inner ear tissues. A polymerase chain reaction (PCR) study was also performed on GRs, 11ß-HSD1, and 11ß-HSD2 in the OC, SV and vestibule of the postnatal rats, and revealed that mRNAs were detected in all those and tissues in all the developmental days of postnatal days 1, 4, and 10. This data indicates that expression of GRs and 11ß-HSD isoforms in the inner ear is tissue and age-specific, and that different local steroid regulation by GRs and the isoforms of 11ß-HSD is present in each part of the inner ear.

Expression of keratinocyte growth factor and its receptor in noncholesteatomatous and cholesteatomatous chronic otitis media.

INTRODUCTION: The purpose of the study was to test a hypothesis that the keratinocyte growth factor (KGF) is a key factor in the pathologic difference between cholesteatomatous (C-COM) and noncholesteatomatous chronic otitis media (NC-COM). We compared the expression levels of KGF and its receptor (KGFR) and the proliferation activity of epithelial cells between NC-COM and C-COM. METHODS: The epithelial lesion was surgically excised with subepithelial tissue from 18 patients with NC-COM and 70 patients with C-COM, and was processed for immunohistochemistry for KGF and KGFR. We also examined the proportion of proliferating epithelial cells using Ki-67 and the extent of infiltrating B and T cells. RESULTS: Keratinocyte growth factor was positive in 5 of 18 (28%) NC-COM specimens and in 61 of 69 (88%) C-COM specimens (p < 0.0001). Furthermore, 37 (60%) C-COM specimens were positive for KGFR, but none of NC-COM were positive (0%; p < 0.01). The Ki-67 labeling index (LI) was significantly smaller in NC-COM than in C-COM (p < 0.001). B-Cell LI was almost similar in the 2 groups. T-Cell LI was significantly higher in C-COM than in NC-COM (p < 0.0001). Interestingly, T-cell LI in NC-COM was higher in KGF-positive tissues than in KGF-negative tissues (p < 0.05). CONCLUSION: The results indicated that coexpression of KGF and KGFR seems to explain the pathologic difference between C-COM and NC-COM, and that KGF may play an important role in the development of cholesteatoma.

Influence of topical application of basic fibroblast growth factor upon inner ear.

BACKGROUND: Basic fibroblast growth factor (b-FGF) has recently been shown to have a positive effect on the treatment of postoperative mastoid cavity problem, but its ototoxicity has not been investigated. OBJECTIVE: To investigate the effect of b-FGF on the inner ear of guinea pigs. STUDY DESIGN AND SETTING: In groups A (n = 10) and B (n =11), b-FGF was applied into the left external auditory canal and the middle ear, respectively. The right ear served as a control. At 1 week after b-FGF administration, the endocochlear DC potential (EP) was measured, and morphology of the cochleae was examined by scanning electron microscopy. RESULTS: In group A, the EP values of experimental ears and controls were 90.0 +/- 8.4 (mV, mean +/- SD) and 89.4 +/- 4.3 (P > 0.05). In group B, the values were 86.5 +/- 11.4 and 87.5 +/- 6.1, respectively, (P > 0.05). Morphological findings showed no damage on the cochlear. CONCLUSION: Application of b-FGF to the external and middle ears does not seem to have an apparent risk of ototoxicity.

Topical application of 5-fluorouracil on attic cholesteatoma results in downregulation of keratinocyte growth factor and reduction of proliferative activity.

To investigate the cell-biological effect of topically applied 5-fluorouracil (5-FU) on middle ear cholesteatoma, 12 attic cholesteatomas were treated with topical application of 5-FU cream, two to five times with an interval of 2 weeks (5-FU group). The control group comprised 65 cholesteatoma that were not treated with 5-FU. All lesions were later excised surgically and processed for immunohistochemical analyses of Ki-67, keratinocyte growth factor (KGF) and its receptor (KGFR). 5-FU significantly reduced the expression of KGF, did not change KGFR expression, and significantly reduced the Ki-67 labeling index, relative to the control group. The effect of 5-FU on cholesteatoma seems to be mediated, at least in part, through downregulation of KGF in stromal cells and reduction of the proliferative activity of epithelial cells.

Does topical application of 5-fluorouracil ointment influence inner ear function?

OBJECTIVE: To investigate the effect of 5-fluorouracil (5-FU) ointment on the inner ear of guinea pigs. STUDY DESIGN AND SETTING: In group A (n = 7), 5-FU ointment was applied into the left external auditory canal. In group B (n = 10), 5-FU ointment was applied to the left middle ear through myringotomy. In both groups, the right ear served as a control. One week later the endocochlear DC potential (EP) was measured and morphology of the cochleae was examined using scanning electron microscopy (SEM) and light microscopy. RESULTS: In group A, there was no significant difference between the EP values of the experimental side and the control side. In group B, there was a statistically significant difference between them (P < 0.05). Morphologic findings showed no damage. CONCLUSION: 5-FU ointment application to the external ear seems to be safe but its application to the middle ear may pose some risk of ototoxicity.