PAX6-positive microglia evolve locally in hiPSC-derived ocular organoids

Abstract

Summary Microglia are the resident immune cells of the central nervous system (CNS). They govern the immunogenicity of the retina, which is considered to be part of the CNS; however, it is not known how microglia develop in the eye. Here, we studied human-induced pluripotent stem cells (hiPSCs) that had been expanded into a self-formed ectodermal autonomous multi-zone (SEAM) of cells that partially mimics human eye development. Our results indicated that microglia-like cells, which have characteristics of yolk-sac-like linage cells, naturally develop in 2D eye-like SEAM organoids, which lack any vascular components. These cells are unique in that they are paired box protein 6 (PAX6)-positive, yet they possess some characteristics of mesoderm. Collectively, the data support the notion of the existence of an isolated, locally developing immune system in the eye, which is independent of the body’s vasculature and general immune system.

A systematic characterization of microglia-like cell occurrence during retinal organoid differentiation

“…After week 4, optic cups are cut out and then cultured in suspension to allow the maturation of 3D-retinal organoids or alternative aggregates as we have described in this manuscript ( Figure 2 A). In contrast to Shiraki et al. (2022) , we identified microglia-like cells with IBA1.…”

“…Overall, we are convinced that the TMEM119 staining in Shiraki et al. (2022) does not represent microglia-like cells based on the discrepancy outlined before about the microglia phenotypes, our independently performed TMEM119 staining, and a potential alternative explanation of the role of TMEM119 during development, which might have been overshadowed by the preferential association of TMEM119 being a microglia-selective marker.…”

“…The performed RT-qPCR for other microglia markers by Shiraki et al. (2022) shows a high SD in the first 2–3 weeks and an overall low expression value suggesting low abundance.…”

“…(2022) , we identified microglia-like cells with IBA1. IBA1 is a well-established marker commonly used for hiPSC-derived microglia-like cells ( Abud et al., 2017 ; Douvaras et al., 2017 ; Haenseler et al., 2017 ; McQuade et al., 2018 ; Muffat et al., 2016 ; Pandya et al., 2017 ) and has not been used for immunostaining by Shiraki et al. (2022) .…”

“…A recent study by Shiraki et al. (2022) describes that PAX6-positive microglia evolved in hiPSC-derived ocular organoids ( Shiraki et al., 2022 ).…”