title: Comparing the Effects of Particulate Matter on the Ocular Surfaces of Normal Eyes and a Dry Eye Rat Model.
abstract: OBJECTIVE
  To compare the effect of exposure to particulate matter on the ocular surface of normal and experimental dry eye (EDE) rat models.
  
  
  METHODS
  Titanium dioxide (TiO2) nanoparticles were used as the particulate matter. Rats were divided into 4 groups: normal control group, TiO2 challenge group of the normal model, EDE control group, and TiO2 challenge group of the EDE model. After 24 hours, corneal clarity was compared and tear samples were collected for quantification of lactate dehydrogenase, MUC5AC, and tumor necrosis factor-α concentrations. The periorbital tissues were used to evaluate the inflammatory cell infiltration and detect apoptotic cells.
  
  
  RESULTS
  The corneal clarity score was greater in the EDE model than in the normal model. The score increased after TiO2 challenge in each group compared with each control group (normal control vs. TiO2 challenge group, 0.0 ± 0.0 vs. 0.8 ± 0.6, P = 0.024; EDE control vs. TiO2 challenge group, 2.2 ± 0.6 vs. 3.8 ± 0.4, P = 0.026). The tear lactate dehydrogenase level and inflammatory cell infiltration on the ocular surface were higher in the EDE model than in the normal model. These measurements increased significantly in both normal and EDE models after TiO2 challenge. The tumor necrosis factor-α levels and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling-positive cells were also higher in the EDE model than in the normal model.
  
  
  CONCLUSIONS
  TiO2 nanoparticle exposure on the ocular surface had a more prominent effect in the EDE model than it did in the normal model. The ocular surface of dry eyes seems to be more vulnerable to fine dust of air pollution than that of normal eyes.
authors.affiliation: Department of Ophthalmology, Korea University College of Medicine, Seoul, South Korea.
authors.forename: Ji Yun
authors.initials: JY
authors.lastname: Han
authors.forename: Boram
authors.initials: B
authors.lastname: Kang
authors.forename: Youngsub
authors.initials: Y
authors.lastname: Eom
authors.forename: Hyo Myung
authors.initials: HM
authors.lastname: Kim
authors.forename: Jong Suk
authors.initials: JS
authors.lastname: Song
mesh_terms: D000818:Animals; D004195:Disease Models, Animal; D015352:Dry Eye Syndromes / Q000378:metabolism / Q000473:pathology*; D020287:In Situ Nick-End Labeling; D007770:L-Lactate Dehydrogenase / Q000032:analysis; D008297:Male; D053758:Nanoparticles / Q000633:toxicity; D052638:Particulate Matter / Q000633:toxicity*; D051381:Rats; D013666:Tears / Q000737:chemistry; D014025:Titanium / Q000633:toxicity; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
chemical_list: D052638:Particulate Matter; D014409:Tumor Necrosis Factor-alpha; C009495:titanium dioxide; D014025:Titanium; D007770:L-Lactate Dehydrogenase