Time course of ocular surface and lacrimal gland changes in a new scopolamine-induced dry eye model.
BACKGROUND
The aim of this study was to set up an animal model of dry eye showing disturbance in several components of the lacrimal functional unit, and to describe the time course of the appearance of clinical signs and inflammatory markers.


METHODS
Dry eye was induced in 6-week-old female Lewis rats by a systemic and continuous delivery of scopolamine via osmotic pumps implanted subcutaneously. We first determined the appropriate dose of scopolamine (6, 12.5, or 25 mg/day) for 28 days. In a second set of experiments, we determined markers after 1, 2, 3, 7, 10, 17, or 28 days of a 12.5-mg/day dose. Clinical signs of corneal dryness were evaluated in vivo using fluorescein staining. MHC II expression and mucin Muc5AC production were detected on the conjunctival epithelium using immunostaining. The level of IL-1beta, IL-6, TNF-alpha, and IFN-gamma mRNA was evaluated by real-time polymerase chain reaction in conjunctiva and exorbital lacrimal gland (LG). Lipids were extracted from the exorbital LG for fatty acid analysis.


RESULTS
Daily scopolamine doses of 12.5 mg and 25 mg applied for a 28-day period induced keratitis, a decrease in Muc5AC immunostaining density in the conjunctival epithelium, and modifications in the fatty acid composition of the exorbital LG. Animals treated with a 12.5-mg/day dose of scopolamine exhibited an increase in corneal fluorescein staining after 2, 10, and 28 days. All animals exhibited unilateral or bilateral keratitis after 17 days. In the conjunctival epithelium, a significant decrease in Muc5AC immunostaining density was observed at early and late time points, and MHC II expression tended to be increased after 1, 7, 10, and 28 days, without reaching statistical significance. The levels of TNF-alpha, IL-1beta and IL-6 mRNA were increased with scopolamine treatment in both conjunctiva and exorbital LG. Arachidonic acid and the Delta5 desaturase index were significantly increased in the exorbital LG of dry eye animals at each time point.


CONCLUSIONS
This systemic and continuous scopolamine-induced model of dry eye in the rat may represent a helpful tool to investigate moderate dry eye, and makes a contribution in the field of dry eye study.
Viau
Sabrina
S
Eye and Nutrition Research Group, UMR1129 FLAVIC, ENESAD, INRA, Université de Bourgogne, Dijon, France.
Maire
Marie-Annick
MA
Pasquis
Bruno
B
Grégoire
Stéphane
S
Fourgeux
Cynthia
C
Acar
Niyazi
N
Bretillon
Lionel
L
Creuzot-Garcher
Catherine P
CP
Joffre
Corinne
C
D000818:Animals; D003229:Conjunctival Diseases / Q000139:chemically induced / Q000378:metabolism* / Q000473:pathology; D003320:Corneal Ulcer / Q000139:chemically induced / Q000378:metabolism* / Q000473:pathology; D016207:Cytokines / Q000235:genetics / Q000378:metabolism; D004195:Disease Models, Animal; D015352:Dry Eye Syndromes / Q000139:chemically induced / Q000378:metabolism* / Q000473:pathology; D005231:Fatty Acids, Unsaturated / Q000378:metabolism; D005260:Female; D020397:Goblet Cells / Q000378:metabolism / Q000473:pathology; D000949:Histocompatibility Antigens Class II / Q000378:metabolism; D007765:Lacrimal Apparatus / Q000378:metabolism* / Q000473:pathology; D055271:Mucin 5AC; D009077:Mucins / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D011917:Rats, Inbred Lew; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012601:Scopolamine; D013997:Time Factors
D016207:Cytokines; D005231:Fatty Acids, Unsaturated; D000949:Histocompatibility Antigens Class II; C524680:Muc5ac protein, rat; D055271:Mucin 5AC; D009077:Mucins; D012333:RNA, Messenger; D012601:Scopolamine