The Role Of Hypoxia-Inducible Factor 1 Alpha In The Regulation Of Human Meibomian Gland Epithelial Cells

PURPOSE. We recently discovered that a hypoxic environment is beneficial for meibomian gland (MG) function. The mechanisms underlying this effect are unknown, but we hypothesize that it is due to an increase in the levels of hypoxia-inducible factor 1 alpha (HIF1 alpha). In other tissues, HIF1 alpha is the primary regulator of cellular responses to hypoxia, and HIF1 alpha expression can be induced by multiple stimuli, including hypoxia and hypoxia-mimetic agents. The objective of this study was to test our hypothesis.METHODS. Human eyelid tissues were stained for HIF1 alpha. Immortalized human MG epithelial cells (IHMGECs) were cultured for varying time periods under normoxic (21% O-2) or hypoxic (1% O-2) conditions, in the presence or absence of the hypoxia-mimetic agent roxadustat (Roxa). IHMGECs were then processed for the analysis of cell number, HIF1 alpha expression, lipid-containing vesicles, neutral and polar lipid content, DNase II activity, and intracellular pH.RESULTS. Our results show that HIF1 alpha protein is present in human MG acinar epithelial cells in vivo. Our findings also demonstrate that exposure to 1% O-2 or to Roxa increases the expression of HIF1 alpha, the number of lipid-containing vesicles, the content of neutral lipids, and the activity of DNase II and decreases the pH in IHMGECs in vitro.CONCLUSIONS. Our data support our hypothesis that the beneficial effect of hypoxia on the MG is mediated through an increased expression of HIF1 alpha.