title: TGF-β2-mediated ocular hypertension is attenuated in SPARC-null mice.
abstract: OBJECTIVE
  Transforming growth factor-β2 (TGF-β2) has been implicated in the pathogenesis of primary open-angle glaucoma through extracellular matrix (ECM) alteration among various mechanisms. Secreted protein acidic and rich in cysteine (SPARC) is a matricellular protein that regulates ECM within the trabecular meshwork (TM), and is highly upregulated by TGF-β2. We hypothesized that, in vivo, SPARC is a critical regulatory node in TGF-β2-mediated ocular hypertension.
  
  
  METHODS
  Empty (Ad.empty) or TGF-β2-containing adenovirus (Ad.TGF-β2) was injected intravitreally into C57BL6-SV129 WT and SPARC-null mice. An initial study was performed to identify a stable period for IOP measurement under isoflurane. The IOP was measured before injection and every other day for two weeks using rebound tonometry. Additional mice were euthanized at peak IOP for immunohistochemistry.
  
  
  RESULTS
  The IOP was stable under isoflurane during minutes 5 to 8. The IOP was significantly elevated in Ad.TGF-β2-injected (n = 8) versus Ad.empty-injected WT (n = 8) mice and contralateral uninjected eyes during days 4 to 11 (P < 0.03). The IOPs were not significantly elevated in Ad.TGF-β2-injected versus Ad.empty-injected SPARC-null mice. However, on day 8, the IOP of Ad.TGF-β2-injected SPARC-null eyes was elevated compared to that of contralateral uninjected eyes (P = 0.0385). Immunohistochemistry demonstrated that TGF-β2 stimulated increases in collagen IV, fibronectin, plasminogen activator inhibitor-1 (PAI-1), connective tissue growth factor (CTGF), and SPARC in WT mice, but only PAI-1 and CTGF in SPARC-null mice (P < 0.05).
  
  
  CONCLUSIONS
  SPARC is essential to the regulation of TGF-β2-mediated ocular hypertension. Deletion of SPARC significantly attenuates the effects of TGF-β2 by restricting collagen IV and fibronectin expression. These data provide further evidence that SPARC may have an important role in IOP regulation and possibly glaucoma pathogenesis.
authors.affiliation: Department of Ophthalmology, Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston, Massachusetts, United States.
authors.forename: Swarup S
authors.initials: SS
authors.lastname: Swaminathan
authors.affiliation: Department of Ophthalmology, Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston, Massachusetts, United States.
authors.forename: Dong-Jin
authors.initials: DJ
authors.lastname: Oh
authors.affiliation: Department of Ophthalmology, Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston, Massachusetts, United States.
authors.forename: Min Hyung
authors.initials: MH
authors.lastname: Kang
authors.affiliation: Ophthalmology Research/Glaucoma Research, Novartis Institutes for Biomedical Research, Fort Worth, Texas, United States.
authors.forename: Allan R
authors.initials: AR
authors.lastname: Shepard
authors.affiliation: Department of Pharmaceutical Sciences and North Texas Eye Research Institute, University of North Texas Health Sciences Center, Fort Worth, Texas, United States.
authors.forename: Iok-Hou
authors.initials: IH
authors.lastname: Pang
authors.affiliation: Department of Ophthalmology, Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston, Massachusetts, United States.
authors.forename: Douglas J
authors.initials: DJ
authors.lastname: Rhee
mesh_terms: D000818:Animals; D000869:Anterior Eye Segment / Q000378:metabolism / Q000473:pathology; D004195:Disease Models, Animal; D015151:Immunoblotting; D007150:Immunohistochemistry; D007429:Intraocular Pressure / Q000187:drug effects*; D058449:Intravitreal Injections; D051379:Mice; D008810:Mice, Inbred C57BL; D009798:Ocular Hypertension / Q000139:chemically induced / Q000378:metabolism* / Q000503:physiopathology; D015676:Osteonectin / Q000096:biosynthesis* / Q000187:drug effects; D053781:Transforming Growth Factor beta2 / Q000008:administration & dosage* / Q000009:adverse effects
chemical_list: D015676:Osteonectin; C578250:SPARC protein, mouse; D053781:Transforming Growth Factor beta2
keywords: SPARC; TGF-β2; intraocular pressure; matricellular proteins