| Background and ObjectiveOne of common ocular trauma, alkali injury on cornea surface, can result in severe inflammation reaction and then corneal neovascularization (CNV). CNV can change the immune privilege of cornea. CNV are the major cause of not only severe vision impairment but also rejection after penetrating keratoplasty. The exact mechanism of CNV is unknown and thus ideal medical treatments of CNV are still lack. Investigation about the mechanism and the antiangiogenic drug is extremely important.TNF-αis a pleiotropic cytokine which is secreted mainly by active macrophages and monocytes mediates proinflammatory functions and host defense mechanism after cornea injury. TNF-αis also believed to play a critical role in corneal inflammation and ulceration. The recent study suggests a pivotal role of TNF-αin corneal wound healing and CNV, but the exact mechanism is unknown. It is still unknown about the role and mechanism of exogenous TNF-αon alkali injury induced CNV. The present study focused on the effect of recombinant murine TNF-αeye drops on alkali injury induced CNV and the expression of VEGF which is probably mainly derived from the intra-corneal infiltrating macrophages.Materials and Methods1. 15 BALB/c mice were burned on central cornea of left eye by 1mol/L NaOH for 40s combine with epithelial denudation, then divided into three groups (5 mice each group): 0.2% sodium hyaluronate control group, 100μg/ml TNF-αtreated group, 500μg/ml TNF-αtreated group. The eye drops were applied twice daily and last one week. CNV was observed by ophthalmic microscope. Corneal microvessel densities of each group were detected at 14th day after alkali injury by CD31 immunohistochemical analysis. The effect of recombinant murine TNF-αon alkali injury induced CNV was observed.2. After alkali injury, 20 BALB/c mice were divided into two groups (10 mice each group): 0.2% sodium hyaluronate control group, 100μg/ml TNF-αtreated group. The eye drops were applied twice daily. At day 2 and day 4 after injury, 5 mouse of each group were killed randomly and the corneas were taken, VEGF expressions in the corneal tissue were detected by RT-PCR.3. In another serial of experiment, macrophages were depleted by Cl2MDP-lip. 10 BALB/c mice were divided into two groups (5 mice each group): Cl2MDP-lip treated group and PBS-lip control group. After alkali injury, all mice were given 100μg/ml TNF-αeye drops twice daily and last one week. Macroscopic CNV was observed by ophthalmic microscope, calculated the length and area of CNV on day 14 after injury. The length and area of CNV between Cl2MDP-lip experimental group and control group were compared.Result1. Corneal microvessel density as determined by CD31 immunostaining in 100μg/ml TNF-αtreated group were greater than those of control group, the difference is statistically significant. No significant difference was found between 500μg/ml TNF-αtreated group with control group.2. The intra-corneal VEGF mRNA expression in the early phase (day 2, day 4) after alkali injury in 100μg/ml TNF-αtreated group were greater than that in control group.3. Length and area of CNV in the Cl2MDP-lip group were less than that in control group (P<0.05). Macrophage depletion significantly attenuated the facilitative effect of 100μg/ml TNF-αon alkali injury induced CNV.Conclusion1. Low dose but not high dose recombinant murine TNF-αcan promote the development of alkali injury induced CNV.2. The mechanism of TNF-αpromote alkali injury induced CNV is probably that it can enhanced macrophage recruitment as well as macrophage VEGF production.3. TNF-αmaybe a good target in the future for clinical intervene CNV.
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