Phagocytosis is a key function in various cells throughout the body. A deficiency in photoreceptor outer segment (POS) phagocytosis by the retinal pigment epithelium (RPE) causes vision loss in inherited retinal diseases and possibly age-related macular degeneration. To date, there are no effective therapies available aiming at recovering the lost phagocytosis function. Here, we developed a high-throughput screening assay based on RPE derived from human embryonic stem cells (hRPE) to reveal enhancers of POS phagocytosis. One of the hits, ramoplanin (RM), reproducibly enhanced POS phagocytosis and ensheathment in hRPE, and enhanced the expression of proteins known to regulate membrane dynamics and ensheathment in other cell systems. Additionally, RM rescued POS internalization defect in Mer receptor tyrosine kinase (MERTK) mutant hRPE, derived from retinitis pigmentosa patient induced pluripotent stem cells. Our platform, including a primary phenotypic screening phagocytosis assay together with orthogonal assays, establishes a basis for RPE-based therapy discovery aiming at a broad patient spectrum.

吞噬作用是全身各种细胞的关键功能。视网膜色素上皮 (RPE) 对光感受器外段 (POS) 吞噬作用的缺陷导致遗传性视网膜疾病和可能与年龄相关的黄斑变性的视力丧失。迄今为止，还没有旨在恢复失去的吞噬功能的有效疗法。在这里，我们开发了一种基于源自人类胚胎干细胞 (hRPE) 的 RPE 的高通量筛选试验，以揭示 POS 吞噬作用的增强剂。命中之一，ramoplanin (RM)，可重复地增强 hRPE 中的 POS 吞噬作用和包裹，并增强了已知可调节其他细胞系统中的膜动力学和包裹的蛋白质的表达。此外，RM 挽救了 Mer 受体酪氨酸激酶 (MERTK) 突变体 hRPE 中的 POS 内化缺陷，来源于视网膜色素变性患者诱导的多能干细胞。我们的平台，包括主要表型筛选吞噬作用测定和正交测定，为基于 RPE 的治疗发现奠定了基础，旨在广泛的患者范围。