EPITHELIAL BARRIER INTEGRITY DURING IN-VITRO WOUND REPAIR OF THE AIRWAY EPITHELIUM

The surface epithelium of the airway mucosa forms a continuous barrier to a wide number of noxious substances present in the lumen. The rest oration of the barrier integrity after injury represents a key issue i n the defense capacity of the airway epithelium. Using an in vitro wou nd repair model of the airway epithelium, we investigated the dynamic of the restoration of the epithelial barrier integrity during the woun d repair process. Airway epithelial cells in culture were chemically w ounded by sodium hydroxide. The immunolocalization of zonula occludens 1 (ZO-1), a cytoplasmic protein associated with the tight junctions, was examined during the wound repair process. Junctional integrity was examined by analyzing the transepithelial resistance (TER) and the pe rmeability to [H-3]mannitol and by visualizing the permeability to lan thanum nitrate during 5 days after injury. Immediately after injury, w e simultaneously observed a 36.7% decrease in the TER and a 74.9% rise in the permeability to [H-3]mannitol. In addition, lanthanum nitrate penetrated ill the intercellular spaces in the repairing area, which w as also characterized by the absence of ZO-1 staining, as opposed to n onrepairing cells. TER and [H-3]mannitol flux values as well as lantha num nitrate and ZO-1 localizations were found to be similar to those o bserved in confluent cultures only 1 to 2 days after complete wound cl osure. This study demonstrates that using our culture model, confluent airway epithelial cells form a continuous and efficient barrier with tight junctions. Epithelial integrity is affected immediately after in jury and is completely restored within 1 to 2 days after wound closure . During such a period of time, the airway epithelium may remain expos ed to the noxious effect of environment in vivo, which can prevent the epithelial barrier restoration by modifying tight junction formation.