Chiba University Graduate School of Medicine, Department of Ophthalmology, Chuo-ku, Chiba, Japan.
RIKEN Center for Biosystems Dynamics Research, Laboratory for Retinal Regeneration, Minato-jima, Chuo-ku, Kobe, Hyogo, Japan.
Invest Ophthalmol Vis Sci. 2024 Oct 1;65(12):8. doi: 10.1167/iovs.65.12.8.
Retinitis pigmentosa represents a leading cause of blindness in developed countries, yet effective treatments for the disease remain unestablished. Previous studies have demonstrated the potential of stem cell-derived retinal organoid (SC-RO) sheet transplantation to form host-graft synapses and to improve light responsiveness in animal models of retinal degeneration. However, the detailed microstructures of these de novo synapses and their functional contribution have not been well elucidated. This study aims to (1) elucidate the microstructures of the host-graft synapse, and (2) investigate the overall distribution and contribution of these synapses to host retinal light responses.
We identified host-graft synapses using a reporter system in mouse SC-RO and rd1 mice, a well-established model of end-stage retinal degeneration. Correlative array tomography was used to reveal the microstructure of host-graft synapses. Furthermore, we developed a semi-automated algorithm that robustly detects the host-graft photoreceptor synapses in the overall grafted area using the same reporter system in flat-mount retinas. We then integrated the spatial distribution of the host-graft synapses with light responses detected by multi-electrode array recording.
Correlative array tomography revealed that host-graft synapses recapitulate the developmental process of photoreceptor synapse formation involving horizontal cells first and then rod bipolar cells. By integrating the spatial distribution of host-graft synapse and multi-electrode array recording, we showed that the number of light-responsive host retinal ganglion cells is positively correlated with the local density of host-graft synapses.
De novo host-graft synapses recapitulate the developmental microstructure of the photoreceptor synapse, and their formation contributes to the light responsiveness after SC-RO transplantation.
色素性视网膜炎是发达国家致盲的主要原因，但该疾病仍缺乏有效的治疗方法。先前的研究表明，干细胞衍生的视网膜类器官（SC-RO）片移植具有形成宿主-移植物突触并改善视网膜变性动物模型中光反应的潜力。然而，这些新形成的突触的详细微观结构及其功能贡献尚未得到很好的阐明。本研究旨在：（1）阐明宿主-移植物突触的微观结构；（2）研究这些突触的总体分布及其对宿主视网膜光反应的贡献。
我们使用报告系统在小鼠 SC-RO 和 rd1 小鼠中鉴定宿主-移植物突触，rd1 小鼠是一种成熟的视网膜退化终末期模型。相关的面层析技术用于揭示宿主-移植物突触的微观结构。此外，我们开发了一种半自动算法，该算法使用相同的报告系统在平面视网膜中对整个移植区域中的宿主-移植物光感受器突触进行稳健检测。然后，我们将宿主-移植物突触的空间分布与多电极阵列记录检测到的光反应进行整合。
相关面层析技术显示，宿主-移植物突触再现了光感受器突触形成的发育过程，首先涉及水平细胞，然后是视杆双极细胞。通过整合宿主-移植物突触的空间分布和多电极阵列记录，我们表明对光有反应的宿主视网膜神经节细胞的数量与局部宿主-移植物突触密度呈正相关。
新形成的宿主-移植物突触再现了光感受器突触的发育微观结构，其形成有助于 SC-RO 移植后的光反应。
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