Nella Kevin T, Norton Benjamin M, Chang Hsiang-Tsun, Heuer Rachel A, Roque Christian B, Matsuoka Akihiro J
Department of Otolaryngology-Head and Neck Surgery, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA; Department of Mechanical Engineering, Robert R. McCormick School of Engineering and Applied Science, Northwestern University, Evanston, IL 60208, USA.
Department of Otolaryngology-Head and Neck Surgery, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA.
Acta Biomater. 2022 Oct 1;151:360-378. doi: 10.1016/j.actbio.2022.08.035. Epub 2022 Aug 22.
Although cochlear implant (CI) technology has allowed for the partial restoration of hearing over the last few decades, persistent challenges (e.g., poor performance in noisy environments and limited ability to decode intonation and music) remain. The "electrode-neuron gap" is inherent to these challenges and poses the most significant obstacle to advancing past the current plateau in CI performance. We propose the development of a "neuro-regenerative nexus"-a biological interface that doubly preserves native spiral ganglion neurons (SGNs) while precisely directing the growth of neurites arising from transplanted human pluripotent stem cell (hPSC)-derived otic neuronal progenitors (ONPs) toward the native SGN population. We hypothesized that the Polyhedrin Delivery System (PODS®-recombinant human brain-derived neurotrophic factor [rhBDNF]) could stably provide the adequate BDNF concentration gradient to hPSC-derived late-stage ONPs to facilitate otic neuronal differentiation and directional neurite outgrowth. To test this hypothesis, a finite element model (FEM) was constructed to simulate BDNF concentration profiles generated by PODS®-rhBDNF based on initial concentration and culture device geometry. For biological validation of the FEM, cell culture experiments assessing survival, differentiation, neurite growth direction, and synaptic connections were conducted using a multi-chamber microfluidic device. We were able to successfully generate the optimal BDNF concentration gradient to enable survival, neuronal differentiation toward SGNs, directed neurite extension of hPSC-derived SGNs, and synaptogenesis between two hPSC-derived SGN populations. This proof-of-concept study provides a step toward the next generation of CI technology. STATEMENT OF SIGNIFICANCE: Our study demonstrates that the generation of in vitro neurotrophin concentration gradients facilitates survival, neuronal differentiation toward auditory neurons, and directed neurite extension of human pluripotent stem cell-derived auditory neurons. These findings are indispensable to designing a bioactive cochlear implant, in which stem cell-derived neurons are integrated into a cochlear implant electrode strip, as the strategy will confer directional neurite growth from the transplanted cells in the inner ear. This study is the first to present the concept of a "neuro-regenerative nexus" congruent with a bioactive cochlear implant to eliminate the electrode-neuron gap-the most significant barrier to next-generation cochlear implant technology.
尽管在过去几十年里，人工耳蜗（CI）技术已使听力得到部分恢复，但一些持续性挑战（如在嘈杂环境中表现不佳以及解码语调与音乐的能力有限）依然存在。“电极 - 神经元间隙”是这些挑战的内在因素，也是阻碍人工耳蜗性能突破当前瓶颈的最重大障碍。我们提议开发一种“神经再生连接体”——一种生物界面，它既能双重保留天然螺旋神经节神经元（SGN），又能精确引导源自人多能干细胞（hPSC）的耳神经元前体细胞（ONP）长出的神经突向天然SGN群体生长。我们假设多角体蛋白递送系统（PODS® - 重组人脑源性神经营养因子[rhBDNF]）能够稳定地为hPSC来源的晚期ONP提供足够的BDNF浓度梯度，以促进耳神经元分化和定向神经突生长。为验证这一假设，构建了一个有限元模型（FEM），以根据初始浓度和培养装置几何形状模拟由PODS® - rhBDNF产生的BDNF浓度分布。为对FEM进行生物学验证，使用多腔微流控装置进行了评估细胞存活、分化、神经突生长方向和突触连接的细胞培养实验。我们成功地生成了最佳BDNF浓度梯度，以实现存活、向SGN的神经元分化、hPSC来源的SGN的定向神经突延伸以及两个hPSC来源的SGN群体之间的突触形成。这项概念验证研究为下一代人工耳蜗技术迈出了一步。重要性声明：我们的研究表明，体外神经营养因子浓度梯度的产生有助于存活、向听觉神经元的神经元分化以及人多能干细胞来源的听觉神经元的定向神经突延伸。这些发现对于设计一种生物活性人工耳蜗至关重要，在这种人工耳蜗中，干细胞来源的神经元被整合到人工耳蜗电极条中，因为该策略将使移植细胞在内耳中实现定向神经突生长。本研究首次提出了与生物活性人工耳蜗相一致的“神经再生连接体”概念，以消除电极 - 神经元间隙——这是下一代人工耳蜗技术的最重大障碍。
