title: Dexamethasone Stiffens Trabecular Meshwork, Trabecular Meshwork Cells, and Matrix.
abstract: OBJECTIVE
  Treatment with corticosteroids can result in ocular hypertension and may lead to the development of steroid-induced glaucoma. The extent to which biomechanical changes in trabecular meshwork (TM) cells and extracellular matrix (ECM) contribute toward this dysfunction is poorly understood.
  
  
  METHODS
  Primary human TM (HTM) cells were cultured for either 3 days or 4 weeks in the presence or absence of dexamethasone (DEX), and cell mechanics, matrix mechanics and proteomics were determined, respectively. Adult rabbits were treated topically with either 0.1% DEX or vehicle over 3 weeks, and mechanics of the TM were determined.
  
  
  RESULTS
  Treatment with DEX for 3 days resulted in a 2-fold increase in HTM cell stiffness, and this correlated with activation of extracellular signal-related kinase 1/2 (ERK1/2) and overexpression of α-smooth muscle actin (αSMA). Further, the matrix deposited by HTM cells chronically treated with DEX is approximately 4-fold stiffer, more organized, and has elevated expression of matrix proteins commonly implicated in glaucoma (decorin, myocilin, fibrillin, secreted frizzle-related protein [SFRP1], matrix-gla). Also, DEX treatment resulted in a 3.5-fold increase in stiffness of the rabbit TM.
  
  
  CONCLUSIONS
  This integrated approach clearly demonstrates that DEX treatment increases TM cell stiffness concurrent with elevated αSMA expression and activation of the mitogen-activated protein kinase (MAPK) pathway, stiffens the ECM in vitro along with upregulation of Wnt antagonists and fibrotic markers embedded in a more organized matrix, and increases the stiffness of TM tissues in vivo. These results demonstrate glucocorticoid treatment can initiate the biophysical alteration associated with increased resistance to aqueous humor outflow and the resultant increase in IOP.
authors.affiliation: Department of Surgical and Radiological Sciences School of Veterinary Medicine, University of California Davis, Davis, California, United States.
authors.forename: Vijay Krishna
authors.initials: VK
authors.lastname: Raghunathan
authors.affiliation: Department of Surgical and Radiological Sciences School of Veterinary Medicine, University of California Davis, Davis, California, United States.
authors.forename: Joshua T
authors.initials: JT
authors.lastname: Morgan
authors.affiliation: Department of Surgical and Radiological Sciences School of Veterinary Medicine, University of California Davis, Davis, California, United States.
authors.forename: Shin Ae
authors.initials: SA
authors.lastname: Park
authors.affiliation: University of California Davis Genome Center Proteomics Core Facility, University of California Davis, Davis, California, United States.
authors.forename: Darren
authors.initials: D
authors.lastname: Weber
authors.affiliation: University of California Davis Genome Center Proteomics Core Facility, University of California Davis, Davis, California, United States.
authors.forename: Brett S
authors.initials: BS
authors.lastname: Phinney
authors.affiliation: Department of Surgical and Radiological Sciences School of Veterinary Medicine, University of California Davis, Davis, California, United States 3Department of Ophthalmology and Vision Sciences, School of Medicine, University of California Davis, Davis, C.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Murphy
authors.affiliation: Department of Surgical and Radiological Sciences School of Veterinary Medicine, University of California Davis, Davis, California, United States.
authors.forename: Paul
authors.initials: P
authors.lastname: Russell
mesh_terms: D000199:Actins / Q000378:metabolism; D000818:Animals; D001696:Biomechanical Phenomena / Q000187:drug effects; D015153:Blotting, Western; D002478:Cells, Cultured; D003907:Dexamethasone / Q000494:pharmacology*; D004548:Elasticity / Q000187:drug effects*; D005109:Extracellular Matrix / Q000187:drug effects / Q000378:metabolism; D016326:Extracellular Matrix Proteins / Q000378:metabolism; D020869:Gene Expression Profiling; D005938:Glucocorticoids / Q000494:pharmacology*; D006801:Humans; D020935:MAP Kinase Signaling System / Q000502:physiology; D040901:Proteomics; D011817:Rabbits; D014129:Trabecular Meshwork / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism
chemical_list: D000199:Actins; D016326:Extracellular Matrix Proteins; D005938:Glucocorticoids; D003907:Dexamethasone