Study On The Signal Pathway Of SOST-mediated Tympanosclerosis Formation

Objective The aim of this study was to establish an experimental tympanosclerosis(TS)model in rats.Methods 34 SD rats were randomly divided into two groups: an experimental group(n=17)and a control group(n=17).The left tympanic cavities in the experimental group were inoculated with Methicillin-resistant staphylococcus aureus(MRSA),while the control group was not treated.The changes of tympanic membranes were examined and recorded at four time points: the first week,the second week,the fourth week and the sixth week.Haematoxylin and eosin(HE)staining was adopted to observe the morphological changes of the tympanic membrane and middle ear mucosa in the sixth week.Results In the end of first week,all the rats in experimental group were survived.However,no calcification was detected in any of these ears.In the end of second week,one rat in experimental group died of pulmonary infection.And,calcifications were detected in 4 left ears among the 16 rats.In the end of fourth week,two rats in the experimental group died of pulmonary infection and one rat died because of overdose anaesthesia.And,calcifications were detected in 7 left ears and 3 right ears among the 13 rats.In the end of sixth week,two rats in the experimental group died of pulmonary infection.And,calcifications were detected in 54.5% ears(12/22)among the 11 rats,including 7 left ears and 5 right ears.Two rats in control group died because of overdose anaesthesia.There were no changes among the 15 survived rats until the sixth weekend.Morphological changes such as mucosa incrassation,inflammatory cells infiltration,fibrous tissue proliferation and interstitial tissue incrassation could be found in the experimental group.These changes occurred not only in the experimental ears but also in the contralateral ears.Conclusion To our knowledge,we firstly presented evidence that tympanosclerosis can also occurred in the contralateral ears during the formation processes of MRSA-induced TS and this phenomenon is involved with the function of exotoxin secreted by MRSA.Thus,intratympanic inoculation of MRSA is a novel approach for establishing an experimental TS model and provides a clinical bridge to explore the pathogenesis of TS.Objective The aim of this study was to investigate the expression of SOST protein in an experimental tympanosclerosis model and its possible role in the pathogenesis of it.Methods Paraffin sections were divided into normal group,left calcification group,right calcification group and non-calcification group.Immunohistochemistry(IHC)was performed to detect the expression of SOST,P-ERK1/2,Wnt3 a and ?-catenin.Half of fresh middle ear tissues were divided into positive group,normal group,left calcification group,right calcification group and non-calcification group.Western blot(WB)analysis was performed to assess the expression of SOST.The other half of fresh middle ear tissues were divided into normal group,left calcification group,right calcification group and non-calcification group.Western blot(WB)analysis was performed to assess the expression of P-ERK1/2,Wnt3 a and ?-catenin.Results SOST proteins were widely distributed in tympanic membrane and middle era mucosa of both experimental group and normal group,and the positions were consistent.In tympanic membrane,SOST proteins were mainly distributed in cytoplasm of epithelial cells.In middle ear mucosa,SOST proteins were mainly distributed in cytoplasm of epithelial cells and gland cells.All of P-ERK1/2,Wnt3 a and ?-catenin proteins could be detected in middle ear of both experimental group and normal group.SOST expression in calcification group was significantly higher than that in positive group,normal group and non-calcification group(P<0.05).There was no statistical difference between left calcification group and right calcification group on expression of SOST(P>0.05)and there was no statistical difference in positive group,normal group,and non-calcification group too(P>0.05).All of P-ERK1/2,Wnt3a and ?-catenin expressions in calcification group were significantly higher than that in normal group and non-calcification group(P<0.05).There was no statistical difference between left calcification group and right calcification group on expressions of P-ERK1/2,Wnt3 a and ?-catenin(P>0.05)and there was no statistical difference in normal group and non-calcification group too(P>0.05).Conclusion SOST protein may participate in inflammation processes of tympanosclerosis by regulating the ERK1/2-MAPK pathway and it is involved into the pathogenesis of tympanosclerosis by regulating the Wnt3 a pathway.