The effect of Sildenafil ,a phosphodiesterase-5 inhibitor, on tendonhealing: An experimental study of rat model on injuried achilles tendon

The Achilles tendon, the most durable tendon in the human body, is also one of the most commonly injured tendons. Sildenafil Citrate is a selective phosphodiesterase -5 inhibitor. As a result of its mechanism of action, it has effects such as vasodilatation, inhibiting platelet aggregation, stimulating angiogenesis, and proangiogenic factor upregulation, stimulating apoptosis and adhesion of fibroblasts, and reducing inflammation. In this study, we aimed to investigate the histopathological and biomechanical effects of Sildenafil Citrate on surgically applied Achilles tendons by conducting a study showing the effect of Sildenafil Citrate, which was not previously in the literature, on the healing of the Achilles tendon. Forty-eight Wistar-albino rats weighing 350-400 grams were randomly divided into groups, 6 in each group, as the study group given Sildenafil Citrate and the control group given saline, respectively. Under ketamine and xylazine anesthesia, 48 rats were divided into 2 groups of twenty-four, as the group that was given Sildenafil and the control group, by creating and repairing an Achilles tendon rupture model. . Each group was divided into four groups among themselves and a total of eight groups were formed. . During the entire experiment, rats were housed in eight separate cages, six of each. The study group of the first group and the control group were sacrificed at the end of 1 week and Achilles tendon samples were taken. After that, Achilles tendon samples were taken by sacrifying the second group at the end of 14 days, the third group at 21 days and the fourth group at the end of 28 days, respectively. The removed Achilles tendons were examined histopathologically and biomechanically. In our study, the maximum strength of the Achilles tendons, which were examined biomechanically, was evaluated according to weeks. We found that there was no significant difference between the Sildenafil Citrate group and the control group in group 1. There was no significant biomechanical difference between the study and control groups in group 2. In group 3, that is, When group given Sildenafil Citrate for 21 days and the control group were evaluated in terms of their maximum strength, we found that there was a statistically significant difference between them (p:0.008). Likewise, when the study group and control group of Group 4 were compared with each other in terms of biomechanics, we saw that there was a significant difference between them (p:0.004). Neovascularization, fibroblastic proliferation, fibrosis and inflammation parameters were evaluated in order to evaluate the healing of the Achilles tendon histopathologically. The groups were evaluated in terms of neovascularization, we found a statistically significant difference (p:0.001). Likewise, when we evaluated the groups in terms of fibroblastic proliferation, we found a statistically significant difference (p:0.035). When the groups were evaluated in terms of fibrosis, a statistically significant difference was found (p:0.017). Finally, when the groups were evaluated in terms of inflammation, it was seen that there was a statistically significant difference (p:0.036). In our study; We can say that sildenafil citrate does not affect the strength of the tendon biomechanically in the acute period, but as the number of days given the drug increases, it biomechanically accelerates tendon healing and creates a stronger tendon. In terms of histopathology, we can say that Sildenafil Citrate has a positive effect on tendon healing. Keywords: Sildenafil, rat, achilles tendon, rat, PDE-5