Abstract
Purpose: :
Schlemm’s canal (SC) and trabecular meshwork (TM) cells are the two cell types that populate the human conventional outflow pathway and regulate intraocular pressure. SC and TM cells in culture have been useful toward understanding their role in conventional outflow homeostasis. Currently available markers that distinguish SC and TM cells in culture are limited and motivated the present study.
Methods: :
SC and TM cells were isolated from human cadaver eyes and cultured in vitro as described previously. Cell lysates were collected from multiple cell strains from each cell type and were analyzed after a period of at least a week at confluence (n=4 SC strains and n=3 TM strains). Lysates were subjected to SDS-PAGE followed by western blot analyses using antibodies that recognize different vascular endothelial markers as probes. Candidate marker proteins included: ERG1/2/3, Robo1, Robo4, alpha-6 integrin, Slug, Snail and TEK/TIE2.
Results: :
SC and TM cells did not differ appreciably in their expression of many of the candidate proteins: ERG1/2/3, Robo1, Robo4 or TEK/TIE2. In contrast, SC cells expressed two proteins differentially from TM cells, the laminin-specific integrin subunit, alpha-6, and the transcriptional repressor, Slug. Differential integrin alpha-6 expression was confirmed by immunohistochemistry in human ocular tissues and Slug by RT-PCR in multiple cell strains.
Conclusions: :
While TM and SC both form monolayer structures, some endothelial responsibilities and several endothelial markers, SC cells differentially express at least two proteins which likely reflect a distinction in cellular responsibilities in vivo.
Keywords: trabecular meshwork • outflow: trabecular meshwork