De-Differentiation of Corneal Epithelial Cells Into Functional Limbal Epithelial Stem Cells After the Ablation of Innate Stem Cells.

Abstract

Regeneration after tissue injury is often associated with cell fate plasticity, which restores damaged or lost cells. Here, we examined the de-differentiation of corneal epithelial cells (CECs) into functional limbal epithelial stem cells (LESCs) after the ablation of innate stem cells. The regeneration of LESCs after the ablation of innate LESCs was identified by a set of markers: ApoE+/Cx43low/CK12-. CK14-CreERT2 or Slc1a3-CreERT mice were crossed with reporter mice to trace the fate of CECs. YAP-TEAD inhibitor verteporfin (VTP) and LATS inhibitor TRULI were used to examine the role of Hippo/YAP pathway in the de-differentiation of CECs. LESCs-ablation cornea showed to be functionally normal, including the maintenance of corneal transparency, prevention of conjunctivalization, and wound healing rate equivalent to that of normal cornea. ApoE+/Cx43low/CK12- LESCs regenerated at the limbus at 6 days after the ablation of innate stem cells, and maintained for at least 6 months. Corneal epithelial lineage tracing showed that CECs migrated back to the limbus after the ablation of innate stem cells, and de-differentiated into active and quiescent LESCs (aLESCs and qLESCs), which participated in corneal epithelial homeostasis and wound healing, respectively, like their innate counterparts. However, when the limbus niche was destroyed by NaOH (1 M, 5 seconds), CECs that occupied the limbus could not de-differentiate into ApoE+/Cx43low/CK12- LESCs and cornea developed into conjunctivalization. In addition, the protein level and activity of YAP increased at the early stage (1-2 days) after the ablation of limbal epithelium, and decreased when the de-differentiation occurred. The YAP-TEAD inhibitor VTP promoted the de-differentiation, whereas LATS inhibitor TRULI inhibited the de-differentiation of CECs. However, the persistent activation of YAP prevented the de-differentiation of CECs after an additional NaOH burn to the limbal stroma, and VTP could not rescue the capacity of CECs to de-differentiate into LESCs. These results reveal the de-differentiation of CECs into functional LESCs after the ablation of innate stem cells, and suggest potential role of Hippo/YAP pathway in the de-differentiation of CECs in vivo.