Modeling ocular surface ion and water transport by generation of lipid- and mucin-producing human Meibomian gland and conjunctival epithelial cells.

Despite the importance of ocular surface in human physiology and diseases, little is known about ion channel expression, properties and regulation in ocular epithelial cells. Furthermore, human primary epithelial cells have rarely been studied in favor of rat, mouse and especially rabbit animal models. Here, we developed primary human Meibomian gland (hMGEC) and conjunctival (hConEC) epithelial cells. We show that hConEC and hMGEC produce MUC5AC and lipids, respectively. With cell cultures maintained at the air-liquid interface, we recorded transepithelial short-circuit currents by the Ussing chamber method. We identified in the apical membrane Na + , Cl − and K + ion channels; amiloride-sensitive ENaC, cAMP-dependent CFTR, UTP-dependent TMEM16a, and chromanol 293B-sensitive KCNQ1. At the basolateral membrane we identified bumetanide-sensitive NKCC and barium-sensitive K + channels. We also found that VIP, concentration-dependent (EC50 of 1-8 nM), stimulates the CFTR-dependent Isc in both cells. Western blot analysis confirms the expression in both cell cultures of βENaC subunit, CFTR, TMEM16a and KCNQ1 proteins. We recorded water influx by quantitative phase microscopy and identified a cAMP-dependent and mercury sensitive water flux and identified by western blot AQP3 and AQP5 proteins in hConEC and hMGEC. Taken together, we propose a model of the ion transports of human conjunctival and Meibomian gland epithelial cells that will set the stage for a future molecular dissection of the regulation of these transport proteins in the context of tear secretion and related diseases.