title: Rat silicone hydrogel contact lens model: effects of high- versus low-Dk lens wear.
abstract: OBJECTIVE
  This study used a rat contact lens (CL) model to test if high- versus low-Dk lens wear caused changes in (1) conjunctival Langerhans cell (LC) number or location; (2) Bcl-2 expression; and (3) infection risk.
  
  
  METHODS
  Female, Lewis rats wore a high- or low-Dk CL continuously for 2 weeks. Afterward, corneas were harvested and processed for ADPase activity to identify LCs, for immunostaining and for real time-polymerase chain reaction. Contact lens-wearing rats also were challenged with Pseudomonas aeruginosa by placing a bacterial-soaked CL on the eye followed by topical delivery of bacteria. After 48 hrs, slit lamp examination and real time-polymerase chain reaction were used to evaluate the corneal response.
  
  
  RESULTS
  Conjunctival LC were significantly increased after low- versus high-Dk CL wear (P<0.0001). In contrast, conjunctival LC in non-lens wearing rats was not significantly different from the high-Dk lens wearing group. Bcl-2 mRNA levels were significantly decreased in low- versus high-Dk CL wearing rats, while Bax, FasL, caspase 3, and caspase 9 levels were unchanged. Immunostaining for Bcl-2 showed fewer positively stained epithelial cells in the low- versus high-Dk lens wearing group. After bacterial challenge, 30% of low- versus none of the high-Dk CL wearing corneas became infected and showed increased mRNA levels for several proinflammatory cytokines/chemokines, inducible nitric oxide synthase and matrix metalloproteinase-9.
  
  
  CONCLUSIONS
  Low- versus high-Dk or non-CL wear led to an increased number of conjunctival LC, decreased Bcl-2 levels, and increased the risk of bacterial infection.
authors.affiliation: Department of Anatomy & Cell Biology, Wayne State University School of Medicine, Detroit, MI 48201, USA.
authors.forename: Yunfan
authors.initials: Y
authors.lastname: Zhang
authors.forename: Manal M
authors.initials: MM
authors.lastname: Gabriel
authors.forename: Mary F
authors.initials: MF
authors.lastname: Mowrey-McKee
authors.forename: Ronald P
authors.initials: RP
authors.lastname: Barrett
authors.forename: Sharon
authors.initials: S
authors.lastname: McClellan
authors.forename: Linda D
authors.initials: LD
authors.lastname: Hazlett
mesh_terms: D000818:Animals; D002452:Cell Count; D003228:Conjunctiva / Q000473:pathology*; D003261:Contact Lenses / Q000009:adverse effects*; D003315:Cornea / Q000382:microbiology; D004198:Disease Susceptibility; D015536:Down-Regulation; D004867:Equipment Design; D005123:Eye / Q000378:metabolism; D015818:Eye Infections, Bacterial / Q000453:epidemiology / Q000209:etiology*; D005260:Female; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate; D015994:Incidence; D007801:Langerhans Cells / Q000473:pathology; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics; D011552:Pseudomonas Infections / Q000453:epidemiology / Q000209:etiology*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D011917:Rats, Inbred Lew; D020133:Reverse Transcriptase Polymerase Chain Reaction; D018570:Risk Assessment; D012828:Silicones
chemical_list: D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger; D012828:Silicones; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate