Losartan Attenuates Scar Formation in Filtering Bleb After Trabeculectomy

Abstract

PURPOSE.To examine the effects of losartan on scar formation after trabeculectomy and on fibrotic changes of human Tenon's fibroblasts (HTFs). METHODS.Trabeculectomy was performed on New Zealand rabbits. They were randomized to receive one of the following treatments: 0.9% normal saline, mitomycin-C, or one of the three doses of losartan. Bleb morphology, IOP, and histopathology examination were performed. Primary cultured HTFs were treated with losartan or vehicle, with or without angiotensin II (Ang II). Cell proliferation was assessed by Cell Counting Kit-8 assay, and cell migration was detected by scratch wound and transwell assay. Transdifferentiation was evaluated through the expression of a-smooth muscle actin (a-SMA) by immunofluorescence, real-time PCR, and Western blot. The expression of fibronectin (FN) was evaluated by real-time PCR and Western blot.RESULTS. An amount of 5 mg/mL of losartan subconjunctival injection significantly decreased IOP postoperatively and attenuated wound healing of the filtering bleb in the rabbit model. Immunostaining results showed less myofibroblast and collagen deposition around the bleb area in the losartan-treated eyes. Losartan (10 À5 M) in vitro significantly attenuated Ang II's stimulatory effects on proliferation and migration of HTFs. Expressions of a-SMA and FN in these cells were also decreased by losartan pretreatment.CONCLUSIONS. Losartan attenuates scar formation of filtering bleb after trabeculectomy likely via decreasing proliferation, migration, transdifferentiation, and extracellular matrix deposition of Tenon's fibroblasts. These results indicate that losartan may be an effective therapeutic agent in preventing bleb scar formation and in improving surgical outcome after trabeculectomy.

Inhibitory Effects of Angiotensin II Receptor Blockade on Human Tenon Fibroblast Migration and Reactive Oxygen Species Production in Cell Culture

“…In their study, losartan (10 –5 M) decreased HTF cell proliferation compared to the control by 20.4%, migration by 48.3% at 24 hours, and transdifferentiation and ECM (extracellular matrix) synthesis by almost 2-fold. 31 Additionally, they also indicated that losartan (5 mg/mL) attenuated bleb scarring after trabeculectomy in rabbit eyes with a 77.8% inhibition compared to control. 31 …”

“…A previous study 30 established the promoting effect of Ang II on fibrosis in vivo after trabeculectomy in rabbits and in vitro using HTFs. Since then, Shi et al 31 also showed that losartan attenuated scar formation in vivo and in vitro. In their study, losartan (10 –5 M) decreased HTF cell proliferation compared to the control by 20.4%, migration by 48.3% at 24 hours, and transdifferentiation and ECM (extracellular matrix) synthesis by almost 2-fold.…”

“…Our findings of this drug class are consistent with the results of recently published studies as we also demonstrated the inhibitory effect of angiotensin receptor blockade (AT1) on fibrosis in human Tenons. 30 – 32 …”

“…While exploration of ocular tissue-specific elements of the RAS, and implications of this in wound healing remain at an early stage, there are recent reports demonstrating higher expression of AT1R, AT2R, and angiotensin II in rabbit Tenon fibroblasts after trabeculectomy, 30 as well as potential therapeutic avenues created by the RAS in the eye. 31 , 32 …”

“…Losartan, the first approved AT1R blocker attenuates scar formation after trabeculectomy in vivo and in vitro, possibly via inhibitory effects on proliferation, migration, trans-differentiation and extracellular matrix deposition. 31 Olmesartan, another angiotensin receptor blocker (ARB), also inhibits fibroblast proliferation in vivo and in vitro. 32 …”