Effect of angiotensin II pathway inhibitors on post-surgical adhesion band formation: a potential repurposing of old drugs.

<bold>Background: </bold>In this study we investigated the therapeutic potential of angiotensin II pathway inhibitors in attenuating post-surgical adhesion band formation in tendon injury.<bold>Method: </bold>We assigned 30 Wistar albino rats to 5 groups, including negative control, positive control, sham, Telmisartan- and Enalapril-treated groups (n=6). Telmisartan and Enalapril at a dose of 10 mg/kg were administered intraperitoneally for 21 days. Hematoxylin-Eosin, and Masson's trichrome staining were used to measure the inflammatory cell accumulation and collagen deposition in the Achilles tendon tissue sections. Oxidative stress markers were analyzed in tissue samples by spectrophotometric methods. Properties of Achilles tendon adhesions were compared based on Tang and Ishiyama scoring systems in the presence and absence of angiotensin II pathway inhibitors.<bold>Results: </bold>Telmisartan and Enalapril reduced severity, length, and density of surgical-induced tendon adhesion at site of injury (***p < 0.001). Our results showed that administration of angiotensin II pathway inhibitors decreased infiltration of inflammatory cells to the injured area (*p < 0.05) and suppressed inflammation by regulating oxidative stress markers including MDA (***p < 0.001), total thiol (***p < 0.001), CAT (***p < 0.001), and SOD (***p < 0.001), in post-operative Achilles tendon tissues. Significant lower collagen deposition and formation of fibrotic tissues was seen in Telmisartan- and Enalapril-treated groups as detected by Masson's trichrome staining which correlated with a decrease in quantity (**p < 0.01) and grading of fibrosis score (***p < 0.001), in adhesive tissues. Moreover, inhibition of angiotensin II pathway could also ameliorate mechanical properties including ultimate load (***p < 0.001), and ultimate stress (*p < 0.05) in injured Tendons.<bold>Conclusion: </bold>Our results showed that ssuppression of inflammation and fibrosis are two mechanisms by which Telmisartan and Enalapril elicit potent protective responses post Achilles tendon injuries. [ABSTRACT FROM AUTHOR]