Purpose: To identify genes upregulated in perfused, intact human trabecular meshwork (TM) in response to elevated intraocular pressure (IOP).
Method: Two pairs of anterior segments of normal human eyes from postmortem donors were placed in culture and perfused 24 hours at constant flow (3 microl/min). After reaching baseline, the flow of one eye from each pair was raised to obtain an incremental pressure (deltaP) of 50 mm Hg for 6 hours. The anterior segments were then quickly frozen in liquid nitrogen, and their TMs were dissected for RNA extraction. SMART cDNA libraries were generated from control and high-pressure human TM RNAs and hybridized to sets of identical high-density cDNA gene arrays. These arrays contained 18,376 human expressed sequence tags (ESTs), corresponding to both characterized and unknown genes. Differentially expressed genes were identified by different-intensity hybridization signals and confirmed by semi-quantitative polymerase chain reaction.
Results: Eleven genes were found to be consistently upregulated in the human TM by elevated IOP: interleukin-6, preprotachykinin-1, secretogranin-II, cathepsin-L, stromelysin-1, thymosin-beta4, alpha-tubulin, alphaB-crystallin, glyceraldehyde-3-phosphate dehydrogenase, metallothionein and Cu/Zn superoxide dismutase. The products of these genes are involved in vascular permeability, secretion, extracellular matrix remodeling, cytoskeleton reorganization, and reactive oxygen species scavenging.
Conclusions: Elevated IOP induced specific upregulation of 11 physiologically relevant genes. On the basis of their known activities, the products of each of these genes might predict homeostatic mechanisms similar to those involved in the regulation of blood vessel permeability. We hypothesize that similar mechanisms might be involved in regulating flow through Schlemm's Canal endothelium.