Expressions of TGF-β1 and MMP-9 in a guinea pig model of tympanosclerosis: possible role in the pathogenesis of this disorder

Tympanosclerosis and atherosclerosis plaques: a comparative analytical study on some new microbiological and immunohistochemical aspects

PURPOSE

The aim of this study was to compare chemical contents, expression of BMP-8a, and the presence of Mycoplasma and ExoS-ExoU exotoxins producing Pseudomonas aeruginosa in tympanosclerosis (TS) and atherosclerosis (AS) plaques.

METHODS

Thirty-six cases with TS and AS plaques (18 each) were selected and examined for chemical, immunohistochemical, and microbial analysis. SPSS ver. 21 and t test analysis were used for comparing the findings, and the level of significance was considered as p < 0.05.

RESULTS

TS plaques showed lower carbon, higher calcium, and phosphorous contents compared to AS plaques (p value < 0.05). Chlorine was detected in AS plaques (1.8 w%) which could probably be due to the presence of myeloperoxidase (MPO) in atherosclerotic artery. Contrary to spherical shape of the surface of TS plaques, AS plaques were needle shaped. BMP-8a expression in TS plaques (59.5%) was significantly higher (p value < 0.0001) than AS plaques (20%). Of the 18 TS specimens, 12, 14, and 3 were positive for ExoS, ExoU Pseudomonas aeruginosa, and Mycoplasma genes, respectively, while of the 18 AS specimens, 2, 2, and 3 were positive for ExoS, ExoU Pseudomonas aeruginosa, and Mycoplasma genes, respectively.

CONCLUSION

TS plaques are different from AS plaques in terms of elemental components, surface morphology, and BMP-8a expression. Therefore, different calcification process and pathogenesis may be responsible for these two diseases. The results of our study showed that both TS and AS plaques have genetic footprint of Mycoplasma, but the level of calcium concentration-dependent exotoxins genes was found only in TS plaques.

Role of TGF-β1-mediated epithelial-mesenchymal transition in the pathogenesis of tympanosclerosis

The present study aimed to explore the role of TGF-β1-mediated epithelial-mesenchymal transition (EMT) in the pathogenesis of tympanosclerosis. Sprague Dawley rats were injected with inactivated Streptococcus pneumoniae suspension to establish a rat model of tympanosclerosis. The rats were sacrificed 8 weeks after the model was established. H&E and von Kossa staining was used to observe the morphological changes of middle ear mucosa. Western blotting was used to detect the expression of TGF-β1 and EMT-associated proteins in the mucosa samples. Middle ear mucosal epithelial cells of rats were collected to establish a primary culture. The cultured cells were stimulated with TGF-β1 and the expression of EMT-associated proteins was detected by western blotting and immunofluorescence. In addition, the cells were treated with TGF-β receptor type I/II inhibitor and the expression level of EMT-associated proteins was detected by western blotting. Sclerotic lesions appeared on 72.4% of tympanic membranes, and marked inflammation, inflammatory cell infiltration and fibrosis were found in the middle ear mucosa of rat models of tympanosclerosis. In middle ear mucosa of rats with tympanosclerosis, the expression of mesenchymal cell markers increased and that of epithelial cell markers decreased compared with the control group. TGF-β1 stimulated the activation of the EMT pathway in middle ear mucosal epithelial cells, resulting in an increased expression of fibronectin and N-cadherin. In addition, a decreased expression level of EMT-associated proteins was observed when TGF-β1 was inhibited. In conclusion, the present study indicated that TGF-β1-mediated EMT may play an important role in the pathogenesis of tympanosclerosis.

Does calcemia influence the onset of myringosclerosis after myringotomy with the insertion of ventilation tubes?

INTRODUCTION

Myringosclerosis is one of the most frequent late complications of the insertion of ventilation tubes, and its aetiopathogenesis remains unknown. The calcification that occurs in the formation of myringosclerosis plaque raises the hypothesis of the presence of a calcium metabolism disorder. The objective is to determine whether calcemia contributes to the development of myringoscelerosis after insertion of ventilation tubes.

MATERIAL AND METHODS

A longitudinal, prospective, analytical cohort study was conducted in patients undergoing myringotomy with the insertion of ventilation tubes due to otitis media with effusion. Calcemia was evaluated pre-operatively and in the follow-up the appearance of myringosclerosis and the percentage of the tympanum involved were evaluated.

RESULTS

The study included 156 patients (297 ears), with calcemia values ranging from 7.6 to 10.2mg/dl. Myringosclerosis was identified in 35.4% of the operated ears. No relationship was found between the appearance of myringosclerosis and calcemia (p=.596). It was found, however, that the greater the percentage of the tympanum affected by myringosclerosis, the lower the calcemia values (p=.014).

CONCLUSION

The population studied had calcemia values within the normal range, which allows us to infer that no changes in calcium metabolism are required for the development of myringosclerosis. Moreover, unlike in previous studies, higher calcium levels are not associated with more myringosclerosis. Calcemia did not influence the appearance of myringosclerosis after myringotomy with the insertion of ventilation tubes.

Combining use of captopril and losartan attenuates the progress of Streptococcus pneumoniae-induced tympanosclerosis through the suppression of TGF-β1 expression

Objectives

In this study, using an Streptococcus pneumoniae-induced tympanosclerosis (TS) model, we explored the effects of captopril and losartan in the treatment of TS and the possible mechanisms.

Study Design

A prospective experimental animal study.

Methods

We set up the TS models in both guinea pig and wistar rat by inoculation of type-3 Streptococcus pneumoniae microorganisms and then treated the animals with the combining use of captopril and losartan. Otomicroscopy was employed to observe the development of TS. Auditory brainstem response was used to test the hearing function of animals. Hematoxylin-eosin and von Kossa staining were performed to determine the morphological changes and calcium depositions. The protein expressions of transforming growth factor β1 (TGF-β1) were assessed by western blot and immunohistochemistry staining, and the mRNA level of TGF-β1 was measured by quantitative reverse transcription- polymerase chain reaction.

Results

The combining use of captopril and losartan attenuated TS responses in terms of a decrease in the TS incidence and the ABR threshold, a reduction of hyalinization and calcification in the middle ear mucosa and the thickness of the mucosa. In addition, the TGF-β1 expression was decreased at both protein and mRNA levels.

Conclusion

Our data indicate, for the first time, that the combining use of captopril and losartan obviously attenuates TS progress through inhibiting the overexpressing of TGF-β1.

Altered response of fibroblasts from human tympanosclerotic membrane to interacting mast cells: implication for tissue remodeling

Several lines of evidence suggest that a tympanosclerotic (TMS) lesion often develops secondary to acute and chronic otitis media. Histological findings indicate that fibroblasts and inflammatory cells, including mast cells, play a key role in the tympanosclerotic plaque formation. However, details on the functional characteristics of tympanosclerotic fibroblasts (Fs(TMS)) are scanty. Therefore the aim of our study was to examine the activity of human fibroblasts from tympanosclerotic lesions and to evaluate the influence of stimulated by crosslinking of IgE receptor mast cells (HMC-1(FcɛRI)) on fibroblast functional behavior. We observed that fibroblasts from normal tympanic membrane (Fs(TM)) released less TNF-α, TGF-β1 and IL-6 compared to Fs(TMS). Fs(TMS) but not Fs(TM) upon interaction with HMC-1(FcɛRI) released increased quantities of TNF-α and TGF-β1. Exposing the fibroblast to HMC-1(FcɛRI) cells resulted in an increased synthesis of proteins including collagen. We noted that the COL2A1 transcript level increased ∼5- and ∼12-fold in Fs(TM) and Fs(TMS) co-cultured with HMC-1(FcɛRI), respectively. Both Fs(TM) and Fs(TMS) upon maintenance in the primary culture released significant quantities of matrix metalloproteinase 9 (MMP-9). However, Fs(TMS) released ∼5-fold more MMP-9 activity compared to the Fs(TM) cultures. The mast cell-induced release of TNF-α, TGF-β1 and MMP-9 sustained for a longer time in Fs(TMS) cultures compared to Fs(TM). Concluding, our data strongly indicate that increased fibroblast sensitivity to mast cell stimulation greatly contributes to the excessive fibrosis and pathological remodeling of the tympanic membrane. We postulate that the persistency of the Fs(TMS) activated state could be an important factor in the pathogenesis of tympanosclerosis.

Levels of reactive oxygen species in rat tympanic membranes after incisional versus radiofrequency myringotomy

OBJECTIVE

A close relationship between reactive oxygen species (ROS) and myringosclerosis, which is a common complication of myringotomy, was recently reported. The objective of this study was to measure ROS levels directly in rat tympanic membranes using luminol-aided chemiluminescence (CL) in order to compare the levels of ROS after incisional and radiofrequency (RF) myringotomy.

METHODS

Fifteen Sprague-Dawley rats were separated into three groups of five animals each. Bilateral myringotomies were made using an appropriate myringotomy lancet in Group 1 and RF in Group 2. Group 3 served as the control group with no myringotomy. Twenty-four hours after the procedure, all tympanic membranes were inspected with an otomicroscope and then excised for the measurement of ROS using luminol-aided CL.

RESULTS

The mean ROS level in Group 1 was significantly higher than that in Groups 2 and 3 (p<0.05 for both). The difference in mean ROS level between Groups 2 and 3 was not significant (p>0.05). Otomicroscopy revealed increased vascularity and vessel dilation in all tympanic membranes that underwent myringotomy. Vascular dilation was observed in the annular region in the vessels that passed along the long arm of the malleus, in addition to the vessels feeding the anterior and posterior tympanomalleolar folds.

CONCLUSIONS

Although the relationship between ROS and the development of myringosclerosis after myringotomy has been demonstrated, the present study is the first to compare incisional and RF myringotomy based on the measurement of ROS levels. Our results indicate that the increase in ROS due to myringotomy was greater following incisional myringotomy than RF myringotomy.