Study of the influence of angiostatin intravitreal injection on vascular leakage in retina and iris of the experimental diabetic rats.

To examine the effect of an intravitreal injection of angiostatin on vascular leakage in retina and iris of the diabetes and study its possible mechanism. Experimental diabetes was induced in 24 rats by an intravenous injection of streptozotocin (STZ) during 48 adult rats. Three groups were randomization distributed of them. There were 8 of both normal and diabetic rats in each group. STZ-diabetic rats and age-matched normal rats received an intravitreal injection of 5 microl of sterile PBS (Phosphate Buffered Saline) into the right eye, and the left eye was non-injected in the group A; Angiostatin was injected into the vitreous of the right eye (7.5 microg/5 microl/eye), and the left eye received the same volume of sterile PBS as the control in the group B and C. The vascular permeability of retina and iris was measured using the Evans blue method at 2 days following the injection in the group A and B. Expression of VEGF in retina was evaluated using western blot analysis 24 hours following the injection in the group C. Diabetic rats showed significant increases of vascular permeability in the retina (P < 0.01) and iris (P < 0.05). Angiostatin-injected eyes showed significant decreases in vascular permeability in the retina (P < 0.01) and iris (P < 0.05) comparing with the PBS-injected eyes in STZ-diabetic rats. In contrast, intravitreal injection of the same dose of angiostatin into the age-matched normal rats did not result in any significant reduction in vascular permeability in the retina and iris, when compared with the contralateral eye with PBS injection (P > 0.05). Angiostatin injection significantly reduced VEGF level in the retinas of STZ-diabetic rats but did not affect retinal VEGF level in normal rats. Angiostatin significantly reduce pathological vascular permeability in the retina and iris of STZ-diabetic rats but not in normal rats. Angiostatin down-regulates VEGF expression and thus, blocks the major cause of vascular leakage in the diabetic retina. Therefore, angiostatin may have a therapeutic potential in the treatment of diabetic macular edema, cystoid macular edema, uveitis and other diseases with vascular leakage.