Inhibitory effect of ILK-siRNA-AAV on scar formation after glaucoma filtering surgery in rats

Objective

To investigate the role of integrin-linked kinase (ILK)-small interfering RNA (siRNA)-adeno-associated virus (AAV) in scar formation after glaucoma filtering surgery in rat eyes.

Methods

Forty-eight Sprague Dawley rats of SPF grade, aged 8 to 9 weeks old, were selected and divided into blank control group, ILK-siRNA-AAV group, NC-siRNA-AAV group and mitomycin C (MMC) group by random number table method, with 12 rats in each group.Left eyes of the rats were taken as experimental eyes, and no intervention was administered to fellow eyes.The bulbar conjunctival filtering bleb after glaucoma filtration surgery in rats was established by anterior chamber drainage tube implantation.One day after operation, phosphate buffer solution, ILK-siRNA-AAV, and NC-siRNA-AAV were injected into the filtering bleb of blank control group, ILK-siRNA-AAV group and NC-siRNA-AAV group, 5 μl each group, respectively.Cotton tablets containing 0.4 mg/ml MMC were placed under conjunctival flap for 5 minutes during operation in MMC group.Intraocular pressure (IOP) was measured with a handheld tonometer before surgery and at 1, 2, 3, 7, 14, 21, 28 days after surgery.Formation of filtering blebs in rats was observed with a surgical microscope at 1, 2, 3, 7, 14, 21, 28 days after operation, and the bleb survival time was calculated by Kaplan-Meier survival analysis.The mRNA and protein expression levels of ILK in conjunctival and subconjunctival tissues at the surgical sites were detected by reverse transcription PCR and Western blot, respectively, on the 28th day after operation.Silencing of ILK gene was identified.Effect of ILK gene silencing on the morphology of drainage pathway was observed by hematoxylin-eosin staining.Effect of ILK gene silencing on collagen fiber deposition in the bulbar conjunctiva at filtration area was examined by Masson staining, and the percentage of positive area of collagen fiber staining in the total tissue visual field was calculated.The use and care of the animals complied with the ARVO Statement.This research protocol was approved by an Ethics Committee of Xi’an Jiaotong University (No.2013-772).

Results

There were statistically significant differences in IOP at different time points between before and after surgery among four groups (F_group=76.84, P<0.001; F_time=114.49, P<0.001). The IOP of ILK-siRNA-AAV group on the 1st, 7th, 14th and 28th day after operation and the IOP of MMC group on the 2nd, 3rd, 7th, 14th and 28th day after operation were lower than those of blank control group, and the differences were statistically significant (all at P<0.05). The IOP of ILK-siRNA-AAV group was lower on 7th, 14th, 21st and 28th day after operation than those of NC-siRNA-AAV group, with statistically significant differences (all at P<0.05). The bleb survival time of blank control group, NC-siRNA-AAV group, ILK-siRNA-AAV group and MMC group was (3.50±1.51), (5.00±3.41), (31.50±3.15) and (31.33±2.46) days, respectively, with a significant difference among them (F=395.83, P<0.05). The bleb survival time of ILK-siRNA-AAV group and MMC group was higher than that of blank control group and NC-siRNA-AAV group, and the differences were statistically significant (all at P<0.05). There were statistically significant differences in the relative expression levels of ILK mRNA and protein among four groups (F=222.32, 752.69; both at P<0.05), and the relative expression levels of ILK mRNA and protein were significantly lower in ILK-siRNA-AAV group than blank control group and NC-siRNA-AAV group, and the differences were statistically significant (all at P<0.05). Proliferative fibrous connective tissue and a large number of cells at surgical sites were found in blank control group and NC-siRNA-AAV group, and the fibroblasts were of a high density and grew in clumps.In ILK-siRNA-AAV group, the bulbar conjunctiva was thin, and the arrangement of fibrous connective tissue was loose, and a few proliferative fibroblasts were found.In MMC group, the conjunctival fibrous layer was loose and thin, forming cavities, and scarce cells were found.There was statistically significant difference in the percentage of collagen fiber positive staining area among four groups (F=741.66, P<0.05). The positive staining percentage of ILK-siRNA-AAV group and MMC group was significantly lower than that of blank control group, among which there was lower positive staining percentage in ILK-siRNA-AAV group than NC-siRNA-AAV group, and the differences were statistically significant (all at P<0.05).

Conclusions

Silencing of ILK can inhibit the scar formation after glaucoma filtering surgery and maintain low IOP in rats.

Glaucoma; Filtering surgery; Integrin-linked kinase; Gene silencing; Small interfering RNA; Adeno-associated virus; Scar formation; SD rats