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Dong-Jin Oh, Min Hyung Kang, Kyu Ryong Choi, E. Helene Sage, Douglas J. Rhee; Adenoviral Gene Transfer of SPARC to Human Trabecular Meshwork Elevates Intraocular Pressure. Invest. Ophthalmol. Vis. Sci. 2011;52(14):4621.
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© ARVO (1962-2015); The Authors (2016-present)
SPARC-null mice have lower intraocular pressures (IOPs) than their wild-type counterparts. Expression of SPARC in adult tissues is frequently associated with excessive deposition of collagen and SPARC-null mice fail to generate a robust fibrotic response to pro-fibrotic stimuli. We studied the effect of SPARC on outflow facility and extracellular matrix (ECM) deposition in the perfused human anterior segments using adenoviral gene transfer of human SPARC (hSPARC).
Baseline facility was measured in paired human anterior segments (n=4 pairs), with a constant-flow perfused anterior segment system. The perfused human anterior segments were then injected transcorneally with 1 x 108 infectious units of adenoviruses, Ad5.CMV.hSPARC and Ad5.CMV.empty. Efficiency of gene transfer over time was verified by infecting cultured human trabecular meshwork (TM) cells and assaying for hSPARC expression, and also by assaying for hSPARC expression in the conditioned media and TM tissue of the perfused human anterior segments. Facility was measured for at least 7 days. At the final day of the perfusion, eyes were fixed and processed for immunolabeling study for hSPARC and ECM proteins.
Adenoviral-delivered hSPARC elevated outflow facility by 23% (p=0.04, n=4) compared with adenoviral controls. SPARC expression was increased 6 times at 50 MOI (multiplicity of infection) and 18.5 times at 100 MOI (n=8) in cultured TM cells. Immunoblotting revealed SPARC expression was increased 37 times in the conditioned media at Day 1 after adenoviral injection and 46 times in the TM tissues at the final day in the perfused human anterior segment system (n=4). Of the ECM proteins, collagen I, IV, and laminin were increased on immunolabeling. Collagen IV was detected more prominently in the inner wall of the Schlemm’s canal.
Outflow facility was elevated with SPARC overexpression by adenoviral delivery, which may come from the increased deposition of ECM proteins. The increase of collagen IV, the abundant collagen in the basal lamina, may be largely responsible for increase in outflow resistance.
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