Abstract
Purpose :
Albinism refers to a group of genetically heterogeneous disorders, typically characterized by a lack of melanin in the eyes, skin, or hair of affected individuals. In addition, patients present ocular abnormalities such as nystagmus, foveal hypoplasia, and chiasmal misrouting, resulting in visual impairment. We recently proposed a retinal pigmentation pathway describing how specific melanosomal impairments cause different forms of albinism. To model this in vitro, we compared retinal organoids of albinism patients and controls to observe potential differences between developing retinal ganglion cells (RGCs) and retinal pigmented epithelium (RPE).
Methods :
Retinal organoids were generated from human OCA1 and FHONDA patient-derived iPSCs and controls. Briefly, stem cell clumps were embedded in Matrigel drops to develop into embryoid bodies for 4 days, before being plated as neurospheres. After 14 days in culture, neurospheres were scraped and cultured in a floating environment to develop into retinal organoids. Samples were taken at day 25, day 44 and day 63, and analysed through RT-PCR and immunohistochemistry (IHC).
Results :
Retinal organoids from control cells showed normal pigmented RPE areas with tight cobblestone structures. FHONDA patient-derived organoids also showed pigmented RPE, as expected. In contrast, OCA1 patient-derived organoids showed cobblestone RPE areas devoid of pigment. A range of ipsilateral and contralateral retinal ganglion cell markers, RPE markers, and disease-causing genes, including ZIC2, ISL2, MITF, BEST1, TYR and SLC38A8 were analysed through RT-PCR. Over time, the expression of a number of key genes involved in either albinism subtype differed when compared to the control. This could also be observed using IHC analysis.
Conclusions :
We developed a new stem cell-derived retinal organoid model to study different albinism subtypes, and observed notable differences between both subtypes and the control organoids which reflect the in vivo situation. This can be used to further model human albinism and its effect on the development of different RGC subtypes and axonal guidance.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.