Endothelia of Schlemm's canal and trabecular meshwork: distinct molecular, functional, and anatomic features

The purpose of this study was to compare human endothelial cells from Schlemm's canal (SCEs) and the trabecular meshwork (TMEs) in terms of ZO-1 isoform expression, hydraulic conductivity (HC) properties, and "giant" vacuole (GV) formation. The principal study methods were Western blot, RT-PCR, immunofluorescence, and perfusion chambers. Blot signals for ⁺-and ^--isoforms were similar in SCEs but less intense for the ⁺-relative to the ^--signal in TMEs. With the anti-⁺ antibody used at 1/50 dilution, binding occurred at cell borders of both cell types, but only to SCEs when used at a 1/200 dilution in vitro and in vivo. SCEs were more resistive than TMEs (HC = 0.66 vs. 1.32 µl·min^-1·mmHg^-1·cm^-2; P < 0.001) when perfused from apex to base. When perfused in the other direction, SCEs were again more resistive (5.23 vs. 9.04 µl·min^-1·mmHg^-1·cm^-2; P < 0.01). GV formation occurred only in SCEs as a function of flow direction, perfusion pressure, and time. We conclude that SCEs and TMEs have distinctive phenotypic properties involving their content of ZO-1 isoforms, barrier function, and GV formation. tight junctions; ZO-1; giant vacuoles; conductivity