Mechanisms of Sensory Hair Cell Survival and Death

我们的基础科学研究主要集中在毛细胞应激时激活的信号转导和细胞间通讯途径。 我们先前研究了热休克蛋白（HSP）在促进应激条件下毛细胞存活中的作用。我们表明HSP诱导是内耳中的关键应激反应，其可以保护毛细胞免受主要应激，包括暴露于两类耳毒性药物（即，氨基糖苷类抗生素和顺铂）。 我们发现，HSP表达的促生存诱导在毛细胞中相对较低，而在支持细胞和常驻巨噬细胞中更稳健。 这些数据表明，毛细胞可能有一个降低的能力，以诱导自主促生存信号在应激反应，并支持细胞和巨噬细胞的非自主信号作为促生存信号的关键介质时，毛细胞处于应激状态。 我们先前发现，胶质样支持细胞在应激诱导的反应中分泌HSP 70，保护毛细胞免受耳毒性药物引起的死亡。 今年，我们已经证明分泌性外泌体作为支持细胞和毛细胞之间发生的非自主细胞信号传导的介质。 外泌体是一类携带蛋白质和核酸货物并可影响受体细胞功能的细胞外囊泡。 我们的数据表明，外泌体的释放是热休克的保护作用所必需的，并且分离的外泌体减少耳毒性药物诱导的毛细胞死亡。 我们已经证明，HSP 70与毛细胞上的TLR 4相互作用来介导这种保护作用。 这些数据以手稿的形式提交给了《临床研究杂志》，得到了好评。 我们目前正在根据审稿人的意见对这份手稿进行修订。 我们的转化研究包括临床前实验，旨在开发治疗方法，以保护暴露于耳毒性药物或其他毛细胞应激的人类的听力。 为了实现这一目标，我们目前正在研究外泌体是否可以被设计为临床治疗听力损失的治疗递送载体。 在第二项转化研究中，我们检查了铂类化疗药物的药代动力学，以确定内耳中铂的摄取与顺铂耳毒性之间的关系。 我们的初步数据表明，顺铂很容易进入耳蜗并无限期地留在那里，而卡铂在很大程度上被排除在耳蜗之外，不会导致听力损失。 奥沙利铂治疗导致耳蜗对铂的一些摄取，但无听力损失。 当本研究完成时，数据将用于生成关于血液迷路屏障的铂进入/排除机制的假设。 临床研究：我们正在研究他汀类药物在多大程度上减少顺铂引起的人类听力损失。 我们正在回顾性和前瞻性地研究这一点。 我们正在与罗切斯特大学耳鼻喉科和沃尔特里德国家军事医学中心合作进行回顾性研究，以检查这个问题。 今年，我们增加了一个新的合作网站，马萨诸塞州眼耳医院，以检查他汀类药物是否减少患有头颈癌的成年人顺铂引起的听力损失。 此外，我们有一项正在进行的前瞻性研究，在该研究中，我们正在测试头颈癌患者在顺铂治疗开始前和顺铂治疗停止后的听力，以确定他汀类药物是否减少该患者人群中的顺铂耳毒性。 这项研究的标题是听力损失和他汀类药物对接受顺铂放化疗治疗的头颈部鳞状细胞癌患者的影响，其ClinicalTrials.gov标识符为NCT 03225157。 到目前为止，这项研究已经纵向检查了超过30名接受顺铂治疗头颈部癌症的受试者的听力变化。

Our basic science studies are focused on the signal transduction and intercellular communication pathways that are activated in response to hair cell stress. We previously examined the roles of heat shock proteins (HSPs) in promoting survival of hair cells under stress. We showed that HSP induction is a critical stress response in the inner ear that can protect hair cells against major stresses, including exposure to both classes of ototoxic drugs (i.e., the aminoglycoside antibiotics and cisplatin). We showed that pro-survival induction of HSP expression is relatively low in hair cells and is more robust in supporting cells and resident macrophages. These data indicate that hair cells may have a reduced capacity to induce autonomous pro-survival signaling in response to stress, and that non-autonomous signals from supporting cells and macrophages function as critical mediators of pro-survival signaling when hair cells are under stress. We showed previously that glia-like supporting cells secrete HSP70 in a stress-induced response that protects hair cells against death caused by exposure to ototoxic drugs. This year we have demonstrated that secretory exosomes act as mediators of the non-autonomous cellular signaling that occurs between supporting cells and hair cells. Exosomes are a class of extracellular vesicles that carry protein and nucleic acid cargo and can influence function of recipient cells. Our data indicate that exosome release is required for the protective effect of heat shock, and isolated exosomes reduce ototoxic drug-induced hair cell death. We have shown that HSP70 interacts with TLR4 on hair cells to mediate this protection. These data were submitted in manuscript form to Journal of Clinical Investigation, which returned favorable reviews. We are currently working on revisions to this manuscript based on the comments of the Reviewers. Our translational studies consist of preclinical experiments aimed at developing therapies to preserve hearing in humans exposed to ototoxic drugs or other hair cell stresses. Toward this goal we are currently examining whether exosomes can be engineered as therapeutic delivery vehicles for clinical treatment of hearing loss. In a second translational study we have examined the pharmacokinetics of platinum-based chemotherapy drugs to determine the relationship between platinum uptake in the inner ear and cisplatin ototoxicity. Our preliminary data suggest that cisplatin readily enters the cochlea and remains there indefinitely, while carboplatin is largely excluded form the cochlea and does not cause hearing loss. Oxaliplatin treatment results in some cochlear uptake of platinum but no hearing loss. When this study is complete, the data will be used to generate hypotheses about the mechanisms of platinum entry/exclusion by the blood-labyrinth barrier. Clinical studies: We are examining the extent to which statins reduce cisplatin-induced hearing loss in humans. We are studying this both retrospectively and prospectively. We have ongoing retrospective studies in collaboration with University of Rochester Otolaryngology Department and Walter Reed National Military Medical Center to examine this question. This year we added a new collaborative site, Massachusetts Eye and Ear Infirmary, to examine whether statins reduce cisplatin-induced hearing loss in adults with head and neck cancer. In addition, we have an ongoing prospective study in which we are testing hearing of head and neck cancer patients before onset of cisplatin therapy and after cessation of cisplatin therapy to determine if statins reduce cisplatin ototoxicity in this patient population. This study is entitled Hearing Loss and the Effects of Statin Drugs in People With Head and Neck Squamous Cell Carcinoma Treated With Cisplatin Chemoradiation, and its ClinicalTrials.gov Identifier is NCT03225157. To date this study has longitudinally examined hearing changes in over 30 subjects taking cisplatin for treatment of head and neck cancer.