Abstract：
Human stem cell-derived organoids enable both disease modeling and serve as a source of cells for transplantation. Human retinal organoids are particularly important as a source of human photoreceptors; however, the long differentiation period required and lack of vascularization in the organoid often results in a necrotic core and death of inner retinal cells before photoreceptors are fully mature. Manipulating the in vitro environment of differentiating retinal organoids through the incorporation of extracellular matrix components could influence retinal development. We investigated the addition of hyaluronan (HA), a component of the interphotoreceptor matrix, as an additive to promote long-term organoid survival and enhance retinal maturation. HA treatment had a significant reduction in the proportion of proliferating (Ki67+) cells and increase in the proportion of photoreceptors (CRX+), suggesting that HA accelerated photoreceptor commitment in vitro. HA significantly upregulated genes specific to photoreceptor maturation and outer segment development. Interestingly, prolonged HA-treatment significantly decreased the length of the brush border layer compared to those in control retinal organoids, where the photoreceptor outer segments reside; however, HA-treated organoids also had more mature outer segments with organized discs structures, as revealed by transmission electron microscopy. The brush border layer length was inversely proportional to the molar mass and viscosity of the hyaluronan added. This is the first study to investigate the role of exogenous HA, viscosity, and polymer molar mass on photoreceptor maturation, emphasizing the importance of material properties on organoid culture. STATEMENT OF SIGNIFICANCE: Retinal organoids are a powerful tool to study retinal development in vitro, though like many other organoid systems, can be highly variable. In this work, Shoichet and colleagues investigated the use of hyaluronan (HA), a native component of the interphotoreceptor matrix, to improve photoreceptor maturation in developing human retinal organoids. HA promoted human photoreceptor differentiation leading to mature outer segments with disc formation and more uniform and healthy retinal organoids. These findings highlight the importance of adding components native to the developing retina to generate more physiologically relevant photoreceptors for cell therapy and in vitro models to drive drug discovery and uncover novel disease mechanisms.
摘要：
人类干细胞衍生的类器官既可以进行疾病建模，又可以作为移植细胞的来源。人类视网膜类器官作为人类光感受器的来源特别重要；然而，在光感受器完全成熟之前，需要长的分化期和类器官缺乏血管化通常会导致坏死核心和内部视网膜细胞死亡。通过掺入细胞外基质成分来操纵分化视网膜类器官的体外环境可能会影响视网膜发育。我们调查了透明质酸（HA）的添加，感光体间基质的一种成分，作为促进长期类器官存活和增强视网膜成熟的添加剂。HA处理使增殖细胞(Ki67+)比例显著降低,光感受器(CRX+)比例增加,表明HA在体外加速了光感受器的定型。HA显著上调对光感受器成熟和外段发育特异的基因。有趣的是,与对照视网膜类器官相比，延长的HA处理显着减少了刷状边界层的长度，感光体外段驻留的地方；然而，HA处理的类器官也有更成熟的外节段，有组织的椎间盘结构，正如透射电子显微镜所揭示的。刷状边界层的长度与添加的透明质酸的摩尔质量和粘度成反比。这是第一个研究外源性HA的作用，粘度,和聚合物摩尔质量对光感受器成熟的影响，强调材料特性对类器官培养的重要性。重要声明：视网膜类器官是研究体外视网膜发育的有力工具，尽管像许多其他类器官系统一样，可以是高度可变的。在这项工作中,Shoichet及其同事研究了透明质酸（HA）的使用，光感受器间基质的天然成分，改善人类视网膜类器官发育中的光感受器成熟。HA促进人类光感受器分化，导致成熟的外节与椎间盘形成和更均匀和健康的视网膜类器官。这些发现强调了添加发育中的视网膜天然成分以产生更多生理相关的光感受器用于细胞疗法和体外模型以驱动药物发现和发现新的疾病机制的重要性。
