Abstract
Purpose: :
To better understand the role of the inner wall of Schlemm’s canal (SC) in the generation of outflow resistance, our goal was to characterize the expression of proteins that participate in intercellular junction assembly, particularly those that are endothelial-specific.
Methods: :
Primary cultures of SC cells and trabecular meshwork (TM) cells were isolated from human donor eyes and cultured as described previously. Messenger RNA was isolated from human SC (SC44, SC45, SC53, SC56) and TM cells (TM26, TM88, and TM89), as well as from human umbilical vein endothelial cells (HUVEC) and human microvascular endothelial cells (HMEC). RNA was transcribed into cDNA and then used in rtPCR analyses with primers specific for mRNA encoding tight junction (JAMs1-3, occludin, claudin-5, ZO-1), adherens junction (VE-cadherin, N-cadherin, p120, β-catenin) and endothelial (VEGF Receptor 1-3, PECAM-1) proteins. Comparisons between cDNA libraries of individual cell strains and types were accomplished using a primer set specific to GAPDH.
Results: :
The primary finding of our analyses was that SC cells expressed mRNA corresponding to VEGF receptor-1 and 2, while TM cells did not. In contrast, both cell types were negative for VEGF receptor-3 expression. SC cells also differentially expressed PECAM-1 and VE-cadherin, compared to TM cells. Interestingly, TM cells displayed consistently higher levels of N-cadherin, compared to SC cells in all strains tested. Messenger RNA for ZO-1, occludin, claudin-5, JAMs1-3, p120 and β-catenin was detected, and not significantly different between SC and TM cell strains.
Conclusions: :
Considering the role of VEGF in endothelial monolayer permeability and its presence in aqueous humor, our results suggest that VEGF receptors participate in the regulation of junctional assembly, and thus inner wall permeability, in Schlemm’s canal endothelial cells.
Keywords: gene/expression • vascular endothelial growth factor • cell adhesions/cell junctions