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Philip Plaeke, University of Antwerp, Wilrijk, Belgium

Intraperitoneal adhesions following surgery or peritonitis are responsible for a wide array of complications, including bowel obstruction, abdominal pain, and even infertility. Additionally, these adhesions tend to make subsequent abdominal procedures more challenging. Proteases, involved in the coagulation and fibrinolysis, have been presumed essential in the etiopathogenesis of adhesions.

Our experiments aimed to modulate adhesiogenesis by administering several protease inhibitors which act on several proteases involved in the coagulation and fibrinolytic pathways.

Intraperitoneal adhesions were induced in OF1 mice (Charles River, France) by cecal ligation and puncture (CLP; 50% ligation, single 21G puncture) under ketamine-xylazine anesthesia. Sham mice underwent a midline laparotomy without ligating or puncturing the cecum. Analgesia (buprenorphine) and fluid resuscitation were provided throughout the experiments. Mice were euthanized 48 hours later and adhesions were scored based on the number of abdominal tissues involved (extent) and the tenacity. The time between the abdominal skin incision and performing a ligation of the terminal ileum was quantified as an objective timed marker for the surgical easiness of access. An overview of the different protease inhibitors and experimental protocols are provided in Table 1. Statistical analysis was performed with SPSS v26, using one way ANOVA with Dunnett’s post-hoc test.

Only one adhesion was encountered after sham surgery, while the CLP procedure resulted in adhesions in all vehicle-treated mice (Table 1). The broad-spectrum protease inhibitor Nafamostat Mesylate (NFM), significantly and dose-dependently reduced the extent (Figure 1A) and tenacity of the adhesions, which resulted in less time required to achieve access to the ileum (p<0.001, Table 1). A preventive dose was needed to notice the beneficial effect. Another broad-spectrum protease inhibitor, UAMC-00050, which has less factor Xa inhibitory activity, failed to reduce adhesions. Similarly, GM6001, a broad-spectrum matrix metalloproteinase inhibitor, had no effects on adhesion formation and increased mortality (Table 1). Finally, specific inhibition of factor Xa with Enoxaparin significantly and firmly reduced the extent and tenacity of the adhesions (Table 1 and Figure 1B). As a result, the time required to gain access and ligate the ileum was no longer different from sham-operated mice.

Protease inhibitors significantly reduced the extent and severity of intraperitoneal adhesions under the condition that they were administered preventively and specifically targeted coagulation pathways, as demonstrated by our experiments with enoxaparin and NFM. Since these protease inhibitors should target the coagulation system, accurate titration and specification of the proteases involved need further study.

Table 1 – Overview of the different experimental regimens and different effects on the adhesion scores.

Figure 1 - Overview of the effects of Nafamostat Mesylate (A) and Enoxaparin (B) on the severity of adhesions in the CLP-model for sepsis.

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