Matrix glycosaminoglycans and proteoglycans in human cornea organoids and similarities with fetal corneal stages.

PURPOSE: We developed human cornea organoids (HCOs) from induced pluripotent stem cells (iPSCs) where single-cell RNA-sequence (scRNA-seq) analysis suggested similarity with developing rather than mature human corneas. We performed immunohistology to determine the presence of corneal glycosaminoglycans as an assessment of maturity. We undertook a detailed comparison of the HCO scRNA-seq data with a recent scRNA-seq study of human fetal corneas at different stages to gauge the HCO's maturity. METHODS: We generated HCOs from a second iPSC line, NCRM-1, to assess the reproducibility of HCO development. We stained sections from both HCO lines with Alcian blue and picrosirius red to determine deposition of sulfated glycosaminoglycans and fibrillar collagens. We immunolocalized glycosaminoglycan biosynthetic enzymes and proteoglycan core proteins. The scRNA-seq data from IMR90.4 HCOs were compared to that of fetal corneas using MetaNeighbor analysis to assess the similarity of HCOs to different stages of human corneal development. RESULTS: The MetaNeighbor analysis suggests closer alignment of the IMR90.4 HCOs with 17-18 post-conception week fetal human corneas. HCOs from both iPSC lines deposit sulfated glycosaminoglycans and fibrillar collagens. Immunohistology showed chondroitin/dermatan sulfate (CS/DS) and keratan sulfate in the presumptive stromal and some epithelial layers. The NCRM-1-derived HCOs show increased CS/DS staining compared to the IMR90.4 derived HCOs. CONCLUSIONS: Both HCO lines show similar developmental patterns and timeline. The NCRM-1 HCO line may have more glycosaminoglycan deposition. Overall, the glycosaminoglycan deposition pattern is consistent with an immature tissue. Optimizations based on our current findings may yield more mature stromal cells and cornea-typical proteoglycans.