Retinal vein occlusion is a common retinal vascular diseases.Thromblysis and anticoagulation therapies are main approaches.However, systemic thrombolysis is relatively inefficient, and it often enhances the risk of hemorrhage.
This study was to investigate the therapeutic effects of PLM-ΔK, a kringle deficiency mutant of plasmin, on photochemically induced branch retinal vein occlusion (BRVO) after intravitreal injection.
BRVO models were established by the combination of caudal vein injection of Rose Bengal with argon laser radiation of periphery area of retinal veins in SD rats.Forty model rats were randomized into balance salt solution (BSS) group and 0.01 U, 0.02 U, 0.03 U PLM-ΔK group, and 10 μl corresponding drug was intravtreally injected 12 hours after modeling.Ophthalmoscopy and fundus fluorescein angiography (FFA) were performed to observe the change of retinal veins.The animals were sacrificed 3 days after intravitreal injection, and hematoxylin and eosin staining was used for the histopathological and ultrastructural examination of retinas.The retina of the rats was isolated for the stretched preparation of retina.The expressions of fibronectin (FN) and laminin (LN) in eyeball wall were assayed by immunofluorescence technology.The use and care of the animals complied with Statement of the Association for Research in Vision and Ophthalmology.
The revascularization of over 2 retinal veins was found in 0, 3, 6 and 8 rats in the BBS group and 0.01 U, 0.02 U, 0.03 U PLM-ΔK group 3 days after intravitreal injection, respectively, showing a significant difference among the groups (χ2=9.635, P=0.022), and the rat number with revascularization in 0.01 U PLM-ΔK group was not significantly different from that in BSS group (Z=-1.558, P=0.119), but the difference between 0.03 U PLM-ΔK group and 0.01 U PLM-ΔK group was significant (Z=-2.762, P=0.006). In the third day after intravitreal injection, retinal vein thrombus were found in the BSS group under the light microscope, and angiogenesis was seen on the retinal flatmount nuclear.In the 0.03 U PLM-ΔK group, posterior vitreal detachment was exhibited under the light microcope, and no retinal new vessel and cell damage were seen.FN was strongly expressed in the inner limiting membrane (ILM) layer, photocyte layer, outer limiting membrane (OLM) layer, choroid and scleral layer, and LN was expressed mainly in the ILM, OLM and scleral layer in the BSS group.However, the expression intensities of FN and LN were obviously weakened in the 0.03 U PLM-ΔK group.
Intravitreal injection of PLM-ΔK can enhance the reperfusion of occluded branch retinal vein and serve as a potential therapeutic drug for BRVO.Also it can permeate into choroid after intravitreal injection to degradate FN and LN.