Abstract
Purpose: :
To investigate the effect of hypoxia on the squamous metaplasia of corneal limbal epithelium.
Methods: :
Human corneal limbal explants were cultured under airlift condition in hypoxia with or without Notch inhibitor DAPT, or in a normoxial manner, for 10 days. Epithelial cell proliferation and differentiation were studied using certain markers such as Ki67, p63, Pax6, K10, and K12 keratins. Activation of p38 MAPK and Notch signaling pathways was determined by immunostaining and western blot. Rabbit corneal limbal epithelial cells were cultured under airlift conditions in normoxia or hypoxia for seven days. The differentiation of rabbit limbal epithelial cells was investigated by immunostaining of K12 and K10 keratins, and real-time PCR of K12, K10, and Pax6.
Results: :
Hyper-proliferation and abnormal epidermal differentiation of human corneal limbal epithelium was induced by air exposure under normoxic condition. Hyper-proliferation was augmented, while abnormal epidermal differentiation was inhibited when limbal explant was cultured in air exposure under hypoxia. Notch signaling pathway was activated in corneal limbal epithelium under hypoxia, accompanied with down-regulation of p38 MAPK signaling pathway. Addition of Notch inhibitor under hypoxic condition restored activation of p38 MAPK, and resulted in recidivation of abnormal differentiation even under hypoxic condition. Furthermore, the abnormal differentiation of rabbit limbal epithelial cells was also blocked under hypoxia in airlift condition, otherwise was prominent in normoxic airlift culture.
Conclusions: :
Hypoxic condition can prevent abnormal epidermal differentiation while enhance proliferation of corneal limbal epithelial cells. Hypoxia coupled with air exposure can be utilized in tissue engineering of corneal limbal epithelial cell sheet.
Keywords: hypoxia • cornea: epithelium • differentiation