title: Altered expression of transforming growth factor beta 1 and matrix metalloproteinase-9 results in elevated intraocular pressure in mice.
abstract: OBJECTIVE
  Extracellular matrix remodeling is thought to have profound effects on tissue architecture and associated function. We have shown previously that overexpression of transforming growth factor beta (TGFβ), which stimulates matrix accumulation, results in altered morphology, cataract, and ocular hypertension in rodents. We have further shown that TGFβ-induced cataracts can be mitigated through inhibition of the matrix metalloproteinases (MMP) MMP-2 and MMP-9. We therefore sought to determine whether loss of MMP expression also altered TGFβ-induced changes in intraocular pressure (IOP).
  
  
  METHODS
  To carry out this study, TGFβ1 transgenic mice were bred onto a MMP-9 null background. IOP measurements were made at 1- to 2-, 2- to 3-, and 3- to 4-month time points using a TonoLab rebound tonometer. Histological and immunofluorescence findings were obtained at the same time points.
  
  
  RESULTS
  Our results demonstrate that lens-specific expression of TGFβ1 in mice results in altered morphology of the anterior segment and an accompanying significant increase in IOP. TGFβ1 transgenic mice bred onto the MMP-9 null background exhibited a further increase in IOP. Interestingly, the MMP-9-deficient animals (without the TGFβ transgene), which exhibited normal angle morphology, had increased IOP levels compared to their wild-type littermates.
  
  
  CONCLUSIONS
  These results indicate that TGFβ and MMP-9 likely act independently in regulating IOP. Additionally, MMP-9 plays an important role in maintaining IOP, and further investigation into the mechanisms of MMP-9 activity in the anterior angle may give clues to how extracellular matrix remodeling participates in ocular hypertension and glaucoma.
authors.affiliation: Department of Pathology and Molecular Medicine, McMaster University Health Science Centre, Rm 1R10, 1200 Main St. West. Hamilton, ON, Canada.
authors.forename: Jennifer V
authors.initials: JV
authors.lastname: Robertson
authors.forename: Anuja
authors.initials: A
authors.lastname: Siwakoti
authors.forename: Judith A
authors.initials: JA
authors.lastname: West-Mays
mesh_terms: D000199:Actins / Q000378:metabolism; D000818:Animals; D015820:Cadherins / Q000378:metabolism; D002448:Cell Adhesion; D024141:Collagen Type IV / Q000378:metabolism; D003315:Cornea / Q000378:metabolism; D007429:Intraocular Pressure / Q000502:physiology*; D007498:Iris / Q000378:metabolism; D020780:Matrix Metalloproteinase 9 / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D013194:Staining and Labeling; D013997:Time Factors; D053773:Transforming Growth Factor beta1 / Q000378:metabolism*
chemical_list: D000199:Actins; D015820:Cadherins; D024141:Collagen Type IV; C508961:Tgfb1 protein, mouse; D053773:Transforming Growth Factor beta1; C544013:alpha-smooth muscle actin, mouse; D020780:Matrix Metalloproteinase 9; C501830:Mmp9 protein, mouse
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