title: Chronic ocular hypertensive rat model using microbead injection: comparison of polyurethane, polymethylmethacrylate, silica and polystyene microbeads.
abstract: OBJECTIVE
  To establish and assess an ocular hypertensive rat model using intracameral injection with various microbeads of different sizes and materials.
  
  
  METHODS
  Chronic elevation of intraocular pressure (IOP) was induced by the injection of various microbeads into the anterior chamber of Sprague-Dawley rat eyes. We compared the IOPs induced by the injection of different microbeads [7- and 17-µm polyurethane (PU), 7- and 15-µm polymethylmethacrylate (PMMA), 13-µm silica, and 15-µm polystyrene (PS)] and selected the appropriate microbeads for a chronic ocular hypertensive model in terms of IOP elevation and adverse events. IOP changes were observed for 4 weeks after microbead injections. Axonal degeneration was assessed with transmission electron microscopic photographs and RGC loss was assessed with retrograde labeling.
  
  
  RESULTS
  Seventy-eight rats were included. Three days after a single injection of microbeads, IOPs were increased by 24.0% by 7-µm PU microbeads, 101.8% by 17-µm PU microbeads, 56.6% by 7-µm PMMA microbeads, 22.0% by 15-µm PMMA microbeads, 153.0% by 13-µm silica microbeads, and 34.7% by 15-µm PS microbeads. 17-µm PU microbeads produced constant IOP elevation with good reproducibility (standard deviation of <6.5 mmHg). Silica injected eyes showed severe inflammation. Sustained IOP elevation by two injections of 17-µm PU microbeads resulted in a 42% axon loss and 36.5% RGC loss (p < 0.05, Mann-Whitney U test).
  
  
  CONCLUSIONS
  PU microbead injections offer an applicable and versatile model for a chronic ocular hypertensive model in rats. Among several biomaterials, PU microbeads produced a more stable IOP elevation without adverse events.
authors.affiliation: Department of Ophthalmology, CHA Bundang Medical Center, CHA Univertsity , Seongnam , Korea and.
authors.forename: Seungsoo
authors.initials: S
authors.lastname: Rho
authors.forename: Insung
authors.initials: I
authors.lastname: Park
authors.forename: Gong Je
authors.initials: GJ
authors.lastname: Seong
authors.forename: Naeun
authors.initials: N
authors.lastname: Lee
authors.forename: Chang-Kyu
authors.initials: CK
authors.lastname: Lee
authors.forename: Samin
authors.initials: S
authors.lastname: Hong
authors.forename: Chan Yun
authors.initials: CY
authors.lastname: Kim
mesh_terms: D000818:Animals; D000867:Anterior Chamber / Q000187:drug effects; D001369:Axons / Q000473:pathology; D002908:Chronic Disease; D004195:Disease Models, Animal; D056965:Injections, Intraocular; D007429:Intraocular Pressure / Q000187:drug effects*; D008297:Male; D008863:Microspheres; D009798:Ocular Hypertension / Q000209:etiology* / Q000503:physiopathology; D019904:Polymethyl Methacrylate / Q000737:chemistry; D011137:Polystyrenes / Q000737:chemistry; D011140:Polyurethanes / Q000737:chemistry; D051381:Rats; D017207:Rats, Sprague-Dawley; D012165:Retinal Ganglion Cells / Q000473:pathology; D012822:Silicon Dioxide / Q000737:chemistry; D013535:Suspensions / Q000009:adverse effects
chemical_list: D011137:Polystyrenes; D011140:Polyurethanes; D013535:Suspensions; D012822:Silicon Dioxide; D019904:Polymethyl Methacrylate
keywords: Chronic ocular hypertension; microbead; optic nerve; polyurethane; rat