TLR4介导的中耳胆脂瘤骨质破坏及其致聋机制研究

TLR which has been proved by our previously study to be involved in middle ear immune response, is a newly discovered pattern recognition receptor. Middle ear cholesteatoma is a common disease and is characterized by bone destruction that could cause deafness through unkown mechanism. No studies revealed whether TLR was involved in bone destruction casused by cholesteatoma of middle ear. Our preliminary experiments indicated that the expression of TLR4 increased significantly and was positively correlated with bone destruction and the level of hearing loss. Further cholesteatoma model was established in TLR4 konck out mices ears in which inflammatory reaction was reduced, cholesteatoma volunme was narrowed, bone destruction and hearing loss was alleviated, comparing with WT mice, which indicated that TLR4 played a key role in bone destruction casused by cholesteatoma. However, what is the mechanism of TLR4 mediated bone destruction？ More preliminary experiments indicated that immune response was alleviated, and the expression of TRAF6 and RANKL, as well as osteoclasts decreased in TLR4 knock out mices. Therefore, based on our study, the thesis that TLR4 induce bone destruction by promoting macrophages differentiation into osteocalsts via RANKL-RANK-TRAF6 signalling pathway was firstly presented. This study will explore the specific role of TLR4 signalling pathway in bone destruction caused by cholesteatoma through in vivo and in vitro experiments. So that it could clarify the molecular mechanism of bone destruction and explore a novel target for the prevent and treatment of cholesteatoma mediated bone destruction.

TLR是新近发现的模式识别受体，我们前期研究证明其参与中耳免疫反应。中耳胆脂瘤是一种以骨质破坏为特征的致聋性疾病，其机制不明，TLR是否参与中耳胆脂瘤骨质破坏，目前无文献报道。预实验显示：TLR4在中耳胆脂瘤中表达显著上调，且与骨质破坏及听力损失程度呈正相关；并且TLR4基因敲除小鼠的中耳胆脂瘤体积变小、骨质破坏和听力损失减轻，证实TLR4在胆脂瘤骨质破坏中起关键作用。那么，TLR4介导胆脂瘤骨质破坏的机制是什么？进一步预实验显示：TLR4敲除后中耳炎症反应减弱、TRAF6和RANKL表达下调，抑制破骨细胞形成。由此，我们首次提出"TLR4激活RANKL-RANK-TRAF6信号通路，诱导巨噬细胞向破骨细胞分化，破坏骨质"假说。本课题将通过体内、外实验揭示TLR4信号通路激活在胆脂瘤骨质破坏中的作用，为明确中耳胆脂瘤骨质破坏的分子机制提供实验依据，并为防治中耳胆脂瘤骨质破坏开辟新思路

中耳胆脂瘤是一种以角化细胞过度增殖和进行性骨质破坏为特征的炎症性致聋性疾病。我们的研究发现病原菌感染可促进中耳胆脂瘤破骨能力显著增强。与先天性胆脂瘤相比，TLR4在中耳胆脂瘤中表达显著上调，且与胆脂瘤的侵袭程度，骨质破坏及听力损失程度呈正相关；并进一步通过小鼠胆脂瘤模型证实TLR4在胆脂瘤骨质破坏中起关键作用, 即TLR4基因敲除小鼠的中耳胆脂瘤体积、骨质破坏和听力损失较较WT小鼠减轻。那么，TLR4介导胆脂瘤骨质破坏的机制是什么？我们进一步研究发现TLR4基因敲除后，能显著减轻促炎反应但不影响细菌清楚，可抑制TRAP-RANKL的激活，从而减少破骨细胞激活。此外，我们研究亦发现髓样诱发受体（Triggering receptor－2expressed on myeloid cells TREM2）可放大TLR4介导的炎症反应，协同TLR4促进MMP2，MMP9分泌，破骨细胞激活，从而增强骨质破坏。并且，TREM2促中耳胆脂瘤骨质破坏是依赖于TLR4信号通路的。我们的研究证实TLR4为胆脂瘤中耳炎骨质破坏致聋的关键分子，并探索了可能的机制，为寻找可能的药物作用和治疗靶点，开发新的防治措施和治疗手段，降低其致聋率，提供了直接的实验依据。