Abstract
Purpose :
Microglia have been implicated in contributing to multiple retinal diseases, including age-related macular degeneration, glaucoma, diabetic retinopathy, and uveitis. As such, there is interest in measures that enable the therapeutic modulation of microglial populations and physiology to alter disease outcomes. Here we explore microglial replacement as a means to manipulate microglial populations using human iPSC (hiPSC)-derived microglia.
Methods :
Human iPSC-derived microglia cells were obtained following embryonic body formation and induction with CSF1, CD34, TGFβ, and CXCL1. The resulting microglia were evaluated using RNAseq, immunohistochemical analysis and functional assessments. Subretinal transplantation of these hiPSC-derived microglia into immunodeficient and transgenic expressing hCSF1 mice following depletion of endogenous retinal microglia using CSF1R inhibitor (PLX5622). Stable integration of transplanted cells was evaluated 4 and 8 months following transplantation. In vivo injury responses of replaced microglia were tested using an RPE injury model.
Results :
Human iPSC-derived microglia expressed mature microglial signature genes including P2RY12, CX3CR1, AIF1, TREM2, as well as relevant transcription factors including PU.1, SALL1, RUNX1, but not MYB. Following subretinal injection into mouse eyes, hiPSC-derived microglia integrated into the ganglion cell layer, the inner and outer plexiform layers as ramified cells with a regular mosaic intercellular spacing typical in endogenous microglia. These cells expressed TMEM119, P2RY12, and CD11b, and were present in the retina as a stable population for up to 8 months. The migration, proliferation and phagocytosis phenotypes of replaced hiPSC-derived microglia are similar to that observed for endogenous retinal microglia.
Conclusions :
hiPSC-derived microglia can be successfully transplanted into microglia-depleted mouse retinas and can stably integrate into the host retina, resembling endogenous microglia in morphology, location, and expression of microglial markers. These replaced microglia show injury responses typical of those in endogenous microglia in the sodium iodate-induced RPE injury model.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.