Involvement of platelet coagulation and inflammation in the endothelium of Schlemm's canal.

PURPOSE: To investigate whether the endothelial cells of Schlemm's canal (ECSCs) are connected to lymphatic vessels or are involved in platelet coagulation and inflammation, by comparing them to lung tissue cells.

METHODS: Three normal eyes, trabeculectomy specimens of 6 early-onset primary open-angle glaucoma (POAG), 15 late-onset POAG, and 6 normal-tension glaucoma (NTG), and lung tissues from 10 normal autopsy cases were used. The specimens were processed for light microscopy of immunohistochemical staining. The antibodies used in this study were von Willebrand factor (vWF) and thrombomodulin for evaluating the platelet coagulation system, CD 34 as a marker for blood vessels, platelet/endothelial cell adhesion molecule (PECAM-1) and E-selectin for evaluating the involvement of inflammation, and D2-40 as a marker for lymphatic vessels.

RESULTS: Thrombomodulin, CD 34, PECAM-1 and E-selectin were detected in ECSCs, the endothelial cells of Sondermann's canal, and the endothelial cells of alveolar capillaries in the lung (EACL), whereas vWF was negative in those cells. Sondermann's canal was often found in compact juxtacanalicular tissue (JCT) in eyes with early-onset POAG. D2-40 was positive in the endothelial cells of lymphatic vessels in the lung (ELVL) and trabecular cells. In early-onset POAG, trabecular cells in JCT were mostly negative for D2-40.

CONCLUSIONS: ECSCs and EACLs are suggested to have developed specifically for their functions from the aspects of the anti-platelet coagulation system and may be involved in inflammation for leukocyte infiltration. D2-40 and thrombomodulin seem to be useful for evaluating morphologic abnormality in POAG.