A look into retinal organoids: methods, analytical techniques, and applications

Abstract

Inherited retinal diseases (IRDs) cause progressive loss of light-sensitive photoreceptors in the eye and can lead to blindness. Gene-based therapies for IRDs have shown remarkable progress in the past decade, but the vast majority of forms remain untreatable. In the era of personalised medicine, induced pluripotent stem cells (iPSCs) emerge as a valuable system for cell replacement and to model IRD because they retain the specific patient genome and can differentiate into any adult cell type. Three-dimensional (3D) iPSCs-derived retina-like tissue called retinal organoid contains all major retina-specific cell types: amacrine, bipolar, horizontal, retinal ganglion cells, Müller glia, as well as rod and cone photoreceptors. Here, we describe the main applications of retinal organoids and provide a comprehensive overview of the state-of-art analysis methods that apply to this model system. Finally, we will discuss the outlook for improvements that would bring the cellular model a step closer to become an established system in research and treatment development of IRDs.

Self-Organization of the Retina during Eye Development, Retinal Regeneration In Vivo, and in Retinal 3D Organoids In Vitro

“…The differences found in the structure of the developing retina and the levels of gene expression are explained by the conditions of cultivation and the lack of in vitro interstitial interactions [ 223 ]. The latter is often emphasized in the literature [ 228 , 229 , 230 ]. The lack of the RPE and lens has been noted to be a cause of changes in the effects of extrinsic factors and morphogen gradients [ 231 , 232 ].…”

“…Retinal organoids allow drug screening and disease modeling, as well as combining them with new genome editing tools. Some perspective and major goals of this work are considered in recent publications [ 229 , 230 , 249 ]. A special field is the use of hiPSC-derived organoids of the retina suffering from one or another genetic retinal disorder (patient-specific organoids) [ 250 , 251 , 252 ].…”

“…Omics datasets combined with the advanced culture methodology can be applied to retinal organoid models, which will help understand the intricate process of human retinogenesis and retinal disease [ 220 ]. Retinal organoids are discussed as a source of cells, including young photoreceptors, as well as NR fragments that may be transplanted and compensate for cell deficit in the diseased, degenerating the retina [ 230 , 253 , 254 ]. The experience of deriving retinal organoids from PSCs should facilitate attempts to grow organoids from adult mammal retina cells, which are the retinal regenerative reserve.…”

Brain and Retinal Organoids for Disease Modeling: The Importance of In Vitro Blood–Brain and Retinal Barriers Studies

“…In accordance, other reviewers highlighted the limitations of retinal organoid technologies [ 99 , 100 , 101 ]. Despite initial successful attempts at modeling inherited retinal dystrophies [ 102 ], the high complexity and low yield in current protocols remain substantial technical challenges [ 100 ], and many questions remain still open [ 11 , 99 ].…”

Multimodal spatiotemporal phenotyping of human organoid development

“…Retinal organoids generated from induced pluripotent stem cells (iPSCs) offer an inroad into studying human retina development, identifying mechanisms of disease, and facilitating the discovery of new treatments (Brancati et al, 2020). From the breakthrough discovery that optic cups spontaneously self-organize in three-dimensional PSC-derived cultures in vitro (Eiraku et al, 2011; Nakano et al, 2012; Sasai, 2013), multiple different protocols to generate human retinal organoids have been developed (Afanasyeva et al, 2021; Cowan et al, 2020; Zhong et al, 2014). Retinal organoids are composed of diverse neural cell types - rod and cone photoreceptors (PRs), bipolar cells (BCs), horizontal cells (HCs), amacrine cells (ACs), retinal ganglion cells (RGCs), and Müller glia (MG).…”