| [Objective] Corneal neovascularization(CNV) is a sight-threatening condition usually induced by inflammatory, infectious, degenerative, and traumatic disorders of the ocular surface. Due to multiple factors and cross segments, the explicit mechanism of CNV is not determined. So far there is no specific effective treatment against this neovascularization and the management of patients with CNV has always been a tough job in ophthalmology. So it is of important significanes to pursue positively different mechanisms involved in the angiogenesis of cornea, and a combined treament with different mechanism may, aiming at the complex pross of CNV ,synergistically inhibit angiogenesis and achieve better therapeutic response. At the initial stage of new blood vessel formation ,the digestion of the extracellular matrix(ECM) barrier underlying the blood vessel endothelial cell layers and the chemotaxis and migration of capillary endothelial cells to respond to an angiogenic stimulus by the activity of Zn2+-dependent metalloproteinase(MMP) is essential . In the study ,CNV was induced by sutures in the corneas of Sprague-Dawley(SD) rats. To observe the expression and activity of matrix metalloproteinase-2 , and to probe into the possible regulating mechanism of MMP implicated in the regulation of corneal angiogenesis;To evaluate the effect of Captopril, an inhibitor of angiotensin converting enzyme, on the growth of CNV, and its cross mechanism was also determined . [Methods] (1)CNV model was induced by placement of 3 interrupted sutures in the corneal stroma of male Sprague-Dawley rat, which was divided into single model and binocular model. Using Digital Slit Lamp Image system to observe the dynamicly developing characters of CNV,including before suturing and 2d,4d,6d,8d after suturing. Neovascularized corneas were harvested at 8d and the pathological changes were observed.(2)With CNV single model, The expression of MMP-2mRNA was examined by Real-time RT-PCR, and the protein level and activity of MMP-2 were detected by gelatin zymography and immunohistochemistry(Evision).(3)With CNV binocular model which was divided into normal cornea control group, Corneal neovascularization control group, captopril treated orally group, captopril subconjunctival injection group and dexamethasone subconjunctival injection group, the CNV condition and area were compaired between different groups and the expression of VEGFmRNA level was determined by reverse transcription-polymerase chain reaction,and its protein level was determined by immunohistochemistry. [Results] (1)The newly formed vessels occurred clearly at 4d in suture-induced cornea and regularly proliferated toward the suture site. Corneal edema increased gradually and the length of blood vessels reached the sites of sutures at 8d within 50% quadrant of conea.(2)The Real-time RT-PCR revealed no significant differences of MMP-2mRNA between normal corneas and the corneas of CNV(t test of Ct,P>0.05); MMP-2 immunoreactivities were absent or lowly expressed predominantly in the corneal epithelium of normal corneas. They increased in CNV, mainly localized to the areas of new vessel formation; The gelatin zymography results showed 62kDa activated MMP-2 were not detectable in normal corneas while the levels of both 72kDa latented and 62kDa activated MMP-2 were significantly elevated during corneal neovascularization. (3)Both the captopril treated orally and subconjunctivaly injected inhibited corneal neovascularization significantly,and the later is more as effective as that of the same dosage of dexamethasone subconjunctivaly injected. (4) The normal rat corneas did not or weakly express VEGF in the basis epithelium,The expression of VEGF increased notely in CNV and were suppressed significantly in the group subconjunctivaly injected with captopril. The expression of VEGFmRNA level paralled that of protein level. [Conclusions] (1) The suture-induced corneal neovascularization at 8d in the rat can be used as an ideal model to observe quantitative a... |
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