Abstract
Abstract: :
Purpose:Most cases of glaucoma are associated with an elevated intraocular pressure which is due to an increased resistance encountered by aqueous humor outflow. The outflow pathway includes cellular barriers composed of trabecular meshwork (TM) cells and schlemm's canal endothelial (SCE) cells. To investigate whether the myocilin gene contributes to the regulation of the barrier properties of human TM and SCE cells, we have overexpressed in both cell types the wild-type human myocilin protein and measured directly the flow resistance of each cell type. Methods:Confluent monolayers of human TM or SCE cells grown on a porous filter support or in a six well plate were transduced with replication deficient recombinant adenovirus containing the full coding cDNA of the human wild-type myocilin gene driven by the cytomegalovirus promoter (AdhTIG3). The flow across the TM or SCE cells in vitro was measured directly and the flow resistance determined. Results:Western blot analysis of the AdhTIG3 transduced TM cells showed overexpression of the 55-57 kDa myocilin protein. Measurement of fluid flow across the cultured TM cells revealed a ten fold decrease in fluid flow resistance in the myocilin transduced cells compared to controls (which consisted of cells transduced with viral vehicles and cells that were not transduced). In contrast, overexpression of the myocilin gene in SCE cells did not result in a change in the fluid flow resistance. Conclusion:These findings suggest that the function of myocilin is cell type dependent. While it has no effect on the barrier properties of the SCE cells, it plays a major role in facilitating transendothelial fluid flow across monolayers of human TM cells. The role of SCE cells as a cellular barrier is accepted by most investigators. However, how TM cells might function as a barrier is not so apparent. Thus it seems surprising that we did not observe a myocilin mediated effect on barrier properties of SCE cells. However these findings are similar to others obtained by using organ cultures transduced with AdhTIG3 (T. B., J Glaucoma 10, 329-39, 2001). Transduction of mutated constructs of myocilin in TM and SCE cells will be important to further investigate myocilin's role in the cellular barrier functions in these two cell types.
Keywords: 503 outflow: trabecular meshwork • 307 adenovirus • 417 gene/expression