OCLN and hydatidiform mole: These observations, however, do not minimize the importance of ZO-1 and occludin for a healthy STB, particularly since in hydatidiform moles, characterized by hyperplasia of the trophoblastic tissue and distention of the chorioninc villi by fluid, the expression of ZO-1 and occludin is downregulated and their distribution in the STB changes from the cell borders to the cytoplasm [10].