Experimental Study On Intravitreous Injection With Domestic Triamcinolone Acetonide For Rabbits Retinal Edema

Objective:To investigate the effect of intravitreous injection with conventional dosage of domestic triamcinolone acetonide (TA) on structure and function of rabbits retina, explore the mechanism of intravitreous injection for retinal edema, provide a theoretic base for the application of TA in clinic.Methods:Part one Forty-eight healthy purebred New Zealand white rabbits randomly divided into two groups underwent intravitreous injection .The right eye of animal of the first group was injected with sterile saline solution 0.1ml as the control A group;and the left eye was injected with TA suspension 4mg (0.1ml) as the B experimental group;The right eye of animal of the second group was injected with TA 0.1ml without excipient as the C experimental group,the excipient removed was supplemented with sterile saline solution;and the left eye was injected with excipient 0.1ml separated from TA suspension as the D experimental group. Flash electroretinography (FERG) was performed on each animal before intravitreous injection, 3 days,2 weeks and 1 month after the injection. After the examination the animal was killed and the eyeballs were extirpated at the three points of time after the injection. The ultrastructural changes of the retina were observed by light and electron microscopy. Part two Six of thirty animals didn't do anything as normal group. The model of retinal edema was established with argon laser photocoagulation to retinal vein in other twenty-four healthy purebred New Zealand white rabbits. The right eye of each animal was injected with TA suspension 4mg (0.1ml) as the TA treated group, and the left eye wasn't injected anything as the control group. Six of the twenty-four animals were killed randomly 3 days, 1week, 2 weeks, and 1 month after the injection. The structure changes of the retinal edema were observed by light microscopy. The expression of VEGF mRNA and IL-6 were observed respectively by hybridization in situ and immunohistochemical method. All the results were analysised by image analysis system of IPP6.0.Results: No significant difference was found in the latent period of b-wave of FERG before and after the injection,but the amplitudes of b-wave of FERG was lower in all the groups than that before the treatment in a short time after the injection(P<0.01). The amplitudes of b-wave of FERG was still lower in the excipient group 1 month after the injection (P<0.01), but other groups almost received. The results of light and electron microscopy showed the ultrastructural changes of the retina in the excipient group at all the three points of time after the injection, only short-time ultrastructural changes in the other groups. The model of retinal edema was established in all the eyes. The degree of retinal edema in TA treated group was lower than that in control group.VEGF expressed in retina tissues at all points of time in control group, but IL-6 only expressed at early time in control group. The expressions of VEGF mRNA and IL-6 in TA treated group were lower than that in control group(p<0.05)Conclusions:Intravitreous injection of domestic TA suspension with the dosage of 4mg may make the ultrastructure changes and function of retina in short term, but the changes are temporal and reversible, and may mainly come from the excipient. VEGF play an important role in the progress of retinal edema after retinal vein occlusion, and IL-6 might also play some roles. Intravitreous injection of domestic TA may lower the expression of VEGF mRNA and IL-6 in the model of retinal edema effectively and protect the retina.