The scarring of conjunctival filtering blebs after glaucomatous surgery is a leading cause of operation failure.Exploring the balance between matrix metalloproteinase-2 (MMP-2) and tissue inhibitor of matrix metalloproteinase-2 (TIMP-2) in conjunctival filtering bleb is very important for the study on pathogenesis of postoperative scarring.
This study was to evaluate the role of MMP-2 and TIMP-2 in wounding healing of subconjunctival tissue after filtering surgery in rats.
Sixty-three clean male SD rats were divided into normal control group and postoperative 1-day, 3-day, 5-day, 7-day, 14-day and 28-day group.The drainage tube was monocularly implanted into the anterior chamber of the rats to establish the filtering surgery models, and the operative response of the eyes was examined under the slit lamp microscope.The animals were sacrificed in corresponding time points, and the frozen sections of eyeballs were prepared, and the expressions of MMP-2 and TIMP-2 in conjunctival and subconjunctival tissues were detected using immunofluorescence technique.Western blot was employed to assay the dynamic expressions of MMP-2 and TIMP-2 proteins in conjunctival and subconjunctival tissues in different groups.The use and care of the rats complied with the Instruction Notions with Respect to Care for Laboratory by State Ministry of Science and Technology.
Filtering blebs were formed in all the operated eyes 1 day after surgery and remained for 7-17 days, with the average survival time of 12 days.Western blot assay revealed that the expression levels of MMP-2 protein in the filtering blebs of the normal control group were 121.67±4.37, and the expressions were gradually elevated from the postoperative 3-day group (183.67±5.61) until the postoperative 7-day group (230.50±8.48) and then gradually declined till the postoperative 28-day group (172.33±8.43) , showing a significant difference among the groups (F=280.18, P<0.05). In addition, the expression levels of TIMP-2 protein in filtering blebs of the normal control group were 102.50±6.25.The expression levels were gradually raised in postoperative 3-day group (162.67±7.00) and peaked in the postoperative 5-day group (232.00±11.03), and then the levels gradually reduced till the postoperative 28-day group (150.50±6.41), with a significant difference among the groups (F=145.34, P<0.05). Immunofluorescent staining showed that MMP-2 and TIMP-2 were weakly expressed in the conjunctival epithelium of the normal rats, while in the operated rats, strong fluorescence for MMP-2 and TIMP-2 was seen in both conjunctival epithelium and subconjunctival tissues of filtering blebs.
The expression trends of MMP-2 and TIMP-2 in the filtering blebs are consistent to the fibrosis process of conjunctival tissue, indicating that MMP-2 and TIMP-2 participate in the scar formation of conjunctival filtering bleb after glaucoma filtering surgery.