ABSTRACT
Leucine-rich repeat-containing G protein-coupled receptor 5 (LGR5), a target of Wnt signaling, is reportedly a marker of intestine, stomach, and hair follicle stem cells in mice. To gain a novel insight into the role of LGR5 in human corneal tissue, we performed gain- and loss-of-function studies. The findings of this study show for the first time that LGR5 is uniquely expressed in the peripheral region of human corneal endothelial cells (CECs) and that LGR5((+)) cells have some stem/progenitor cell characteristics, and that in human corneal endothelium, LGR5 is the target molecule and negative feedback regulator of the Hedgehog (HH) signaling pathway. Interestingly, the findings of this study show that persistent LGR5 expression maintained endothelial cell phenotypes and inhibited mesenchymal transformation (MT) through the Wnt pathway. Moreover, R-spondin-1, an LGR5 ligand, dramatically accelerated CEC proliferation and also inhibited MT through the Wnt pathway. These findings provide new insights into the underlying homeostatic regulation of human corneal endothelial stem/progenitor cells by LGR5 through the HH and Wnt pathways.