Myocilin Levels in Primary Open-angle Glaucoma and Pseudoexfoliation Glaucoma Human Aqueous Humor

Abstract

Purpose-To determine the concentration of myocilin in primary open-angle and pseudoexfoliation glaucoma aqueous humor.Methods-Aqueous humor was collected during surgery from patients with primary open-angle glaucoma (POAG), pseudoexfoliation glaucoma (PEXG), and elective cataract removal (control). Volume-equivalent aqueous samples were separated on SDS-PAGE gradient gels. Quantification of myocilin levels was performed using Western blots probed with two independent N-terminal polyclonal anti-myocilin antibodies (AB1 and AB2) followed by densitometry. Myocilin levels in aqueous humor were quantified by plotting the densitometry readings of the aqueous samples against a recombinant myocilin standard curve. Total protein concentration was determined by Bradford protein assay. Transforming growth factor beta 2 (TGFβ2) levels were assessed by ELISA.Results-Myocilin levels are significantly elevated in human POAG aqueous humor when compared to control aqueous humor (AB1: 0.66 ± 0.53 ng/μl vs. 0.23 ± 0.20 ng/μl, p<0.001; AB2: 0.98 ± 0.59 ng/μl vs. 0.65 ± 0.5 ng/μl, p<0.03; mean ± SD). Myocilin makes up a larger percent of the total protein in POAG aqueous humor compared to control aqueous (AB1: 0.26 ± 0.20% vs. 0.10 ± 0.20%, p<0.001; AB2: 0.43 ± 0.32% vs. 0.28 ± 0.18%, p<0.05). In contrast to POAG, myocilin levels were not elevated in PEXG aqueous humor when compared to control aqueous humor. No correlation between myocilin and TGFβ2 levels was observed.Conclusions-Myocilin is elevated in POAG, but not PEXG aqueous humor.

Biomarkers in primary open angle glaucoma

“…Myocilin levels were tested in control AH and compared to the levels of POAG and pseudoexfoliation glaucoma AH to determine whether levels of myocilin are altered in these glaucoma subsets. These levels were signifi cantly elevated in human POAG AH when compared with control AH (105) . A more recent study demonstrated that myocilin expression is not altered in the blood of POAG patients, unlike myocilin expression in the corresponding TM cultures (108) .…”

“…The protein is found in both intracellular and extracellular spaces, and has been linked to elevations in intraocular pressure. TM issue from POAG, low-tension glaucoma, and pseudoexfoliation glaucoma had increased myocilin immunoreactivity when compared to normal tissue (105) . Steroid treatment of monolayer TM cells or cultured human anterior segments showed a time and pressure dependent increase in myocilin protein production and secretion.…”

“…Rats that spontaneously develop increased IOP had a 4-fold increase in myocilin transcription. Myocilin is present in AH where it may serve as a marker for the glaucomatous state (105) . Evidence supports a role for elevated myocilin levels in canine glaucomatous AH particularly in breeds with primary glaucoma.…”

“…Steroid treatment of monolayer TM cells or cultured human anterior segments showed a time and pressure dependent increase in myocilin protein production and secretion. Perfusion of human anterior segment organ culture with recombinant myocilin increases outfl ow resistance (105) . Furthermore, animal models show a correlation between increased myocilin levels and elevated IOP.…”

Bioactive Lysophospholipids: Role in Regulation of Aqueous Humor Outflow and Intraocular Pressure in the Context of Pathobiology and Therapy of Glaucoma

“…[23][24][25][26][27][28] A great deal of effort has gone into exploring how these different bioactive agents influence TM tissue properties and cell biology in the context of AH outflow in both in vitro and in vivo studies. 15,16,24,[29][30][31][32][33][34][35][36] These efforts are beginning to unravel the participation of several different intracellular signaling mechanisms, including Rho GTPase, Wnt, ECM/ mechanotransduction, integrins, nitric oxide, PKC, BMPs/ SMADs, MAP kinases, and others, in regulating contractile properties of TM cells, ECM turnover, adhesive interactions, biomechanical properties, permeability, and survival of outflow pathway tissues and cells.…”