Abstract
Purpose: :
The presence of CD44, a receptor for hyaluronans, is being investigated in dogs of different breeds with glaucoma, being mostly primary, including those from the POAG colony of Beagles, with one example of secondary. We have examined the localization of CD44 in these glaucomatous canine eyes by immuno–histochemistry.
Methods: :
Paraffin–embedded specimens from the anterior uveas of 12 Beagles with inherited glaucoma (3–mos– to 13–yrs–old) and age–matched normal Beagles and 9 other dogs (Chow, Cocker Spaniel, Italian Greyhound, Miniature Poodle, Yorkshire Terrier and Mixed Breed) with primary or secondary glaucoma (7–14–yrs–old) were sectioned and then were incubated with monoclonal anti–human CD44 IgG (R & D Systems, Inc.) overnight at 4 degrees C. Specimens were incubated with secondary antibody either with biotinylated link followed by peroxidase–labeled streptavidin and then by substrate–chromogen for light microscopy.
Results: :
Within normal canine specimens, cells of the nonpigmented epithelium (NPE) of the CB processes stained diffusely for CD44 within their cytoplasm, being strongest in the youngest animals. Among the glaucomatous dogs, the cytoplasm of the NPE generally localized more than the age–matched normals, especially among the Beagles with advanced POAG, which often had clusters of cells that reacted intensely. Within the normal iridocorneal angle (ICA), the trabecular meshwork and adjacent sclera reacted positively for CD44, being strongest in the youngest eyes, becoming weaker with age. Within the glaucomatous eyes, CD44 localization within the ICA and adjacent region was greater than that of age–matched normals among the moderate and advanced POAG Beagles. CD44 localization among the other breeds varied from light to intense and depended in part on the degree of ICA collapse. CD44 localization in the specimen with secondary glaucoma was less intense than that seen in the primary cases.
Conclusions: :
Immuno–localization of CD44 in the normal and glaucomatous canine eye was successfully observed among 8 different breeds. Changes in the apparent activity of CD44 within the aqueous humor outflow pathway of individuals with spontaneous glaucoma are associated with the disease progression seen in Beagles with POAG. When comparing immuno–localization of CD44 among the selected breeds with primary glaucoma, differences occur both at the level of the NPE and the ICA, possibly reflecting differences in the progression of various types of canine primary glaucoma.
Keywords: immunohistochemistry • ciliary body • trabecular meshwork