Abstract
Purpose: :
The mouse retina contains three kinds of basement membrane (BM) structures, the inner limiting membrane, Bruch’s membrane and the basement membrane surrounding the capillaries. All BMs are made up of laminin, collagen IV and nidogen (also referred to as entactin) protein families as well as the proteoglycan perlecan. We aim to investigate the expression and distribution of individual basement membrane components in three different diabetic mouse strains.
Methods: :
We analyzed eyes obtained from double heterozygous IR/IRS-1 mice, db/db mice and the respective wild types. Further C57BL/6J mice were rendered diabetic by five consecutive daily intraperitoneal injections of STZ (65mg/kg) while the non-treated group served as controls. After 4 and 6 months of diabetes (defined by blood glucose > 300mg/dl) eyes were enucleated and examined to describe differences between normal and diabetic retinal BMs. The specificity of antibodies against basement membrane proteins was ascertained through immunoblotting with proteins extracted from mouse retinae.
Results: :
Laminin and nidogen-1 were detected in all retinal BMs in diabetic and control retinae of all mouse strains. Furthermore, both proteins were abundant in the inner limiting membrane and in the capillary basement membranes. In all three mouse strains nidogen-2 was only barely detected in the inner limiting membrane just as collagen IV. While db/db- and IR/IRS-1 mice showed only small differences in the protein expression in comparison to the respective wild types marked changes were detected in STZ treated mice.The diabetic retinae of all three mouse strains have significantly thicker inner nuclear layer than non-diabetic retinae.
Conclusions: :
Our results show a participation of laminins, nidogens and collagen IV in the BM remodeling during diabetic retinopathy. The basement membranes within the three mouse strains are differently composed, especially with regard to the expression in the inner limiting membrane. These changes in the BMs composition may affect both the assembly and the function of the retina.
Keywords: diabetic retinopathy • Bruch's membrane • immunohistochemistry