Rat silicone hydrogel contact lens model: effects of high- versus low-Dk lens wear.
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.
Zhang
Yunfan
Y
Department of Anatomy & Cell Biology, Wayne State University School of Medicine, Detroit, MI 48201, USA.
Gabriel
Manal M
MM
Mowrey-McKee
Mary F
MF
Barrett
Ronald P
RP
McClellan
Sharon
S
Hazlett
Linda D
LD
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
D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger; D012828:Silicones; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate