Corneal organoids – Future perspectives
Authors: Balmer Pierre 
Published: December 2022

AbstractOrganoids are currently a high topic in development and is employed as a model system mimicking human tissue. This promising technology offers a potential tool to investigate disease mechanisms for further clinical applications.Organoids recapitulate the cellular diversity, arrangement, gene‐expression, and functional aspects of a targeted organ. These organoids can be used for multiple kind of large‐scale projects, such as therapy development. In this course, we will discuss strategies to generate corneal organoids, their characterization, their perspectives in life science and pre‐clinical approaches and review the current state of research while focusing on corneal organoids and compare their advantages and limitations to animal model.As a start, cells with correct viability are required. It exists multiple sources of stem cells able to generate organoids in vitro, adult corneal cells isolated from biopsies have the advantage to generate organoids resembling the organ source, but the collection has the disadvantage to be invasive. An alternative and highly valuable approach to generate organoid is from pluripotent stem cells, carrying the potential to differentiate into most cell types of the body and are subdivided into embryonic stem cells, derived from the inner cell mass of preimplantation embryos, and induced pluripotent stem cells (IPSCs) reprogrammed from adult cells. These adult cells can be collected from a skin biopsy, blood or interfollicular epidermis.Once cells are collected, organoids can be generated by several approaches, but remains on the same principles: stem cells are forced into aggregates to start the neural induction, then neural vesicle are excised and put in culture, in which specific cell‐types of the cornea will migrate and form the three corneal layers and will follow maturation and selection. Currently methods are in development to reduce this labor‐intensive manual handling and produce a large‐scale generation of corneal organoids, while keeping a high success rate and low variability.When corneal organoids are generated, their correct characterization needs to be investigated. As the cornea has a particular cell arrangement of multiple layers, a certain cell density and transparency, corneal organoids need to have similar characteristics to the human cornea. For this, classical methodology as live‐imaging or immunostainings are highly used to define their correct cell arrangement and new technologies such as Single Cell RNA‐seq are used to compare the gene expression profile of multiple cell type and assess the homeostasis of corneal organoids compared to human cornea.Finally, corneal organoids are available for multiple downstream applications. As therapeutic approaches, organoids can be used as a living biobank or to model corneal diseases, either by using cells from affected patients or by base editing, introducing a causative mutation into the genome. Either patient‐derived or control organoids have the high potential to develop gene therapy, optogenetics, be a source of transplantable cells to replace generating tissue or screen small molecules treatments.