Induction of cyclooxygenase-2 in anterior uveal tissue following glaucoma filtration surgery in rabbits

Purpose. The success of glaucoma filtration surgery is dependent on limiting the proliferation of subconjunctival fibroblasts. Since production of prostaglandins is known to be increased following ocular surgery, and prostaglandins have been demonstrated to affect fibroblast proliferation, this study was undertaken to determine whether cyclooxygenase-2 (COX2) is induced in anterior uveal tissue following glaucoma surgery. Methods. One of the following surgical procedures were performed on the right eye of New Zealand white albino rabbits: 1) standard trabeculectomy, 2) aborted trabeculectomy following scleral flap dissection (i.e. sclerectomy not performed), 3) peripheral iridectomy through a limbal incision, and 4) trabeculectomy without peripheral iridectomy. The animals were sacrificed at 1 hr and 3 hrs post-surgery. The total RNA from the arterior uveal tissue of the operated right eyes and the unoperated left eyes was isolated. The total RNA was treated with DNAase and reprecipitated prior to cDNA synthesis using MMLV. PCR was carried out using a primer set specific for rabbit COX2 which produced a PCR product of 501 bp. Results. PCR performed on cDNA from operated eyes undergoing standard trabeculectomy, peripheral iridectomy, and trabeculectomy without iridectomy (1 hr and 3 hrs post-surgery) produced a band at the expected size; sequencing verified these PCR products to be COX2. PCR of cDNA from the corresponding unoperated eyes did not produce any detectable bands. In eyes undergoing aborted trabeculectomy, no detectable PCR bands were identified in either the operated or the corresponding unoperated eyes. Conclusions. COX2 expression in anterior uveal tissue is not constitutively expressed and is upregulated soon after filtration surgery and peripheral iridectomy. Entry into the anterior chamber appears to be the crucial step in eliciting this expression of COX2, since aborted trabeculectomy eyes, in which the eye was not entered, did not demonstrate any COX2 expression. Induction of COX2 may play an early role in the stimulation of subconjunctival fibroblast proliferation.