Abstract
Purpose :
A trabecular meshwork (TM) stem cell population, located in the “Insert” region beneath Schwalbe’s line, is thought to keep the aqueous humor outflow pathway populated. With aging and particularly in glaucoma, TM cellularity declines and intraocular pressure (IOP) homeostasis is lost. IOP elevation often results in progressive glaucomatous optic nerve damage and blindness. Our hypothesis is that differences in gene expression patterns of TM insert stem cells and mature TM cells will highlight key functional differences of these two cell types.
Methods :
The Insert and the TM were surgically dissected from paired aged normal human eyes and total RNA was used for RNASeq at the Massively Parallel Sequencing Shared Resource at Oregon Health & Science University. The data were analyzed with several bioinformatics and pathway programs. Immunohistochemistry was performed on human anterior segment tissue sections.
Results :
Of 52,209 transcript sequences found, 11,245 genes were expressed at similar levels in the Insert and TM. With adjusted P < 0.05, 3040 genes were higher in the TM and 2250 were higher in the Insert. Principal Component Analysis showed tight clustering within regions in paired eyes and significant biological variation between individuals. A subset of stem cell markers and genes associated with glaucoma were differentially expressed. Differences were also observed in pathway components previously shown to be involved in 1) the IOP homeostatic response; 2) the mechanical stretch response; 3) the laser trabeculoplasty mechanism; and 4) the molecules key in forming and regulating the aqueous humor outflow resistance. This indicates the latent readiness of the Insert stem cells to take over key TM cell functions. Cell cycle or checkpoint related genes higher in Insert included PDLIM2, NRG1, POU6F2 and FOXJ1, while those higher in TM included GAS7, CDC123, SOX2 and GAP43.
Conclusions :
These transcriptome data highlight resting Insert stem cell readiness and changes needed to transition to functional TM cells able to assist in IOP homeostasis. The cell division related differences suggest important control points that hold TM cells quiescent and hold Insert cells in typical stem cell slow division mode. These studies may facilitate progress towards improved clinical outcomes for glaucoma.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.