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，HSP70与毛细胞上的TLR4相互作用来介导这种保护作用。 这些数据发表在Journal of Clinical Investigation上。 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。 此外，我们正在研究驻地巨噬细胞的作用，作为介导的毛细胞生存和死亡的小鼠全身顺铂治疗。 最后，我们最近表明，FDA批准的降胆固醇药物洛伐他汀减少顺铂诱导的小鼠听力损失（费尔南德斯等人，2020听力研究PMCID：PMC7080598） 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。 我们最近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完成了一项回顾性研究，以检查这个问题。 我们还完成了前瞻性研究，在该研究中，我们在顺铂治疗开始前和顺铂治疗停止后测试了头颈部癌症患者的听力，以确定他汀类药物是否降低该患者人群的顺铂耳毒性。 我们对前瞻性和回顾性研究的综合分析表明，接受顺铂治疗头颈部癌同时服用阿托伐他汀的受试者与未服用他汀类药物的受试者相比，顺铂诱导的听力损失的发生率和严重程度降低。 这些数据发表在Journal of Clinical Investigation（费尔南德斯等人2021 PMCID：PMC7773379）。 基于这些数据，我们开始了一项III期、随机、安慰剂对照研究，以确定阿托伐他汀在多大程度上降低该人群中顺铂诱导的听力损失。 该项目获得了2020年NIH Bench to Bedside奖。 本研究的人类受试者方案已获得NIH中心IRB的批准。

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 published in Journal of Clinical Investigation. 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 addition, we are examining the roles of resident macrophages as mediators of hair cell survival and death in mice treated with systemic cisplatin. Finally, we recently showed that the FDA-approved cholesterol-lowering drug lovastatin reduces cisplatin-induced hearing loss in mice (Fernandez et al., 2020 Hearing Research PMCID: PMC7080598) Clinical studies: We are examining the extent to which statins reduce cisplatin-induced hearing loss in humans. We recently completed a retrospective study in collaboration with University of Rochester Otolaryngology Department and Walter Reed National Military Medical Center to examine this question. We also completed our prospective study in which we tested the 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. Our analyses of the combined prospective and retrospective studies indicate that subjects undergoing cisplatin therapy to treat head and neck cancer who are concurrently taking atorvastatin experience reduced incidence and severity of cisplatin-induced hearing loss compared to subjects not taking a statin. These data were published in Journal of Clinical Investigation (Fernandez et al 2021 PMCID: PMC7773379). Based on these data, we have initiated development of a phase 3, randomized, placebo-controlled study to determine the extent to which atorvastatin reduces cisplatin-induced hearing loss in this population. This project was awarded a 2020 NIH Bench to Bedside Award. The human subjects protocol for this study has been approved by the NIH Central IRB.