Non-Invasive Molecular Imaging of MAdCAM-1 in Endotoxin-Induced Uveitis

Abstract

Purpose: : Uveitis, an inflammatory disease, is a major cause of vision loss. During inflammation, leukocytes use L-selectin to bind to endothelial MAdCAM-1, to initiate the recruitment cascade. Role of MAdCAM-1 in the eye has been unknown. Utilizing our novel molecular imaging technique, we target MAdCAM-1 on retinal and choroidal endothelium to study its role in endotoxin induced uveitis (EIU).

Methods: : Uveitis was induced by injection of 100µg of lipopolysaccharide diluted in 0.1ml sterile saline into one hind footpad of Lewis rats. Anti-MAdCAM-1 mAb conjugated microspheres were injected systemically into anesthetized control and EIU animals. Microsphere adhesion to the endothelium of the choriocapillaris was investigated in anesthetized animals under physiologic flow conditions by scanning laser ophthalmoscopy (SLO). Subsequently, animals were perfused and retinal and choroidal flatmounts were prepared to assess the number of firmly adhering microspheres and leukocytes. Western blotting was performed to detect MAdCAM-1 expression.

Results: : Binding of anti-MAdCAM-1 mAb conjugated microspheres to the endothelium of the choriocapillaris was significantly higher 4h after EIU induction (2079±84.4, n=5), compared to normal controls (299.4±10.4, n=5, p<0.01). Microsphere interaction in the choriocapillaries remained significantly elevated by 24h after EIU induction, compared to normal controls (p<0.01). MAdCAM-1 protein expression was upregulated 24 and 72h after EIU induction.

Keywords: uveitis-clinical/animal model • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • choroid