Experimental Study On Prevention Of Posterior Capsule Opacification By Adenovirus-mediated HSV-TK/GCV System

Objective To investigate the preventing effect on posterior capsule opacification and the toxicity for eye anterior segment by adenovirus-mediated herpes simplex virus thymidine kinase/ganciclovir system.Methods 12 New Zealand White Rabbits were used and divided into 4 groups of 3 rabbits at random. After phacoemulsification, all rabbits were given intracameral injections of 0.1ml of BSS(in group 1 and 2) or adenoviral vector carrying the HSV-TK gene(in group 3 and 4). 12 hours after surgery, all rabbits were given intracameral injections of 0.1ml of BSS(in group 1 and 3) or GCV(in group 3 and 4)on a schedule of once daily for 3 days. examinations of the eye anterior segment and the posterior capsule were performed postoperatively. All animals were killed and the eyes were encleated 4 weeks postoperatively. PCO were observed using Miyake-Apple view. All the capsular bags were measured by wet weight and examinated histologically. The cornea,iris and ciliary body were also examinated histologically Results (1)Clinical examination: Mild corneal edema and aqueous humor opacity were observed in all the eyes within 3 days postoperatively, relieved gradually within 1 week postoperatively and recovered normally within 2weeks postoperatively. PCO was evaluated 4 weeks postoperatively. group 4 had low PCO scores, while each of the other three groups had high PCO scores. Statistical analysis showed a significant difference(versus group 1 P=0.008,versus group 2 P=0.003,versus group 3 P=0.004)between group 4 and the other three groups and no difference(P>0.05) was showed between group 1,2 and 3.(2)Observation Through Miyake-Apple view: Group 4 had small and thin PCO. However, each of the other three groups had large and thick PCO.(3)Assessment of the wet weight of the capsular bags: The wet weight of the capsular bags of group 4 was smaller than that of each of the other three groups[group 1:(79.88±4.97)mg, group 2:(80.52±6.03)mg, group 3:(80.30±3.64)mg, group 4:(53.30±3.49)mg]. Statistical analysis showed a significant difference (P<0.05) between group 4 and the other three groups and no difference (P>0.05) was showed between group 1,2 and 3.(4)Histological examination of the capsular bags: It could be seen in group 4 that a small amount of LECs at the capsular equator proliferated and migrated to the posterior capsule, forming a thin soemmering ring in the periphery of the capsular bags, forming thin fibromembrane which embodied monolay metaplastic fibroblast-like cells in the center of the capsular bags, or with no cells or cortical material in the center of the capsular bags. However, it could be seen in each of the other three groups that a large amount of LECs at the capsular equator proliferated and migrated to the posterior capsule, forming a dense soemmering ring. in the periphery of the capsular bags and thick fibromembrane which embodied multilay metaplastic fibroblast-like cells in the center of the capsular bags.(5) Evaluation of the toxicity: inflammatory reaction of iris and ciliary body was seen in group 4 and group 3 and not in group 1 and group 2. Inflammatory reaction in group 4 was severer than that in group 3.Conclusions Adenovirus-mediated HSV-TK/GCV system can effectively prevent PCO. However, it has toxicity for iris and ciliary body.