Abstract
Purpose: :
Diabetic retinopathy, a chronic inflammatory disease of the retina, is characterized by the early low grade inflammation leading to leucocyte migration and adhesion to the retinal vasculature. In this study, we have identified molecules that mediate retinal leukocyte migration and infiltration, resulting in the alteration of the blood retinal barrier.
Methods: :
To examine the role of CCL2 and Angiopoietin-2 in retinal leukocyte infiltration, we injected B6.129P2-Cx3cr16-GFP mice intravitreally with either recombinant mouse CCl2 or Ang2 and examined the retina by confocal imaging. These mice express Enhanced Green Fluorescent Protein (EGFP) in monocytes and microglia. In addition these mice were made diabetic and the extent of monocyte infiltration was determined. RNA was extracted from the retina and gene expression was analyzed using PCR based assays. In vitro studies using human retinal endothelial cells were also done to examine the expression of chemokines in response to high glucose conditions.
Results: :
Using B6.129P2-Cx3cr16-GFP mice, we found that intravitreal injection of recombinant CCl2 into the eye leads to the increased accumulation of monocytes in the retinal vessels as well as in the retinal tissue. This was further confirmed by increased expression of the F4/80 gene, a marker for monocytes. Injection of Ang2 upregulated the expression of CCL2 in the retina and also increased the infiltration of monocytes. In animals after 2 weeks of diabetes, there was a similar increase in the presence of activated monocytes and retinal microglia within the retinal tissues. In vitro studies demonstrate that the high glucose increases CCL2 expression in endothelial cells mediated by Ang2.
Conclusions: :
CCl2 and Ang2 together or independently mediate the migration of monocytes into the retina during the development of diabetic retinopathy. This monocyte migration and trafficking into the retina may play an important role in the alteration of the blood-retinal barrier, and provide a new therapeutic target in diabetic retinopathy.
Keywords: diabetic retinopathy • inflammation • cytokines/chemokines