Modelling therapies to prevent surgical adhesions

Abstract

Peritoneal injury, in particular post-surgery, often leads to adhesions, bands of scar tissue joining visceral organs to each other or to the inner abdominal body wall. Such adhesions can cause intestinal obstruction, infertility in women, and potentially chronic pelvic pain. Current therapy relies on physical barriers with the intention of keeping damaged tissues apart, however, they do not have efficacy in all situations. Therefore, new ways to prevent adhesions from forming are required. Surface mesothelial cells are proposed to influence adhesion formation due to their ability to undergo mesothelial to mesenchymal transition (MMT). Transforming growth factor-beta 1 (TGF-beta1) plays an important role in MMT induction while Bone morphogenic protein 4 (BMP4) prevents MMT so may be a promising therapeutic factor to reduce adhesion formation. As the half-life of intra-peritoneal administered factors is short, drug delivery vehicles may offer a solution. This project addresses the hypothesis that novel peptide hydrogels act as barriers to maintain tissue separation during the critical period of peritoneal repair, and as drug delivery vehicles releasing BMP4 resulting in adhesion prevention. The project uses both in vitro human and mouse mesothelial cells and in vivo surgical models to test the efficacy of BMP4 in the prevention of adhesions delivered using fabricated hydrogel vehicles. A systematic review was initially conducted to assess the impact of postoperative abdominal adhesions in veterinary practice. Results from the 92 publications found showed that cats were most susceptible to adhesions, followed by cows and then horses with previous abdominal haemorrhage and peritonitis episodes related to prevalence. Overall, findings suggest that adhesions post-surgery are a major problem in veterinary practice similar to the medical field but further studies are required to determine their full impact. Next, human mesothelial cells were co-cultured with a variety of peptide hydrogels (Peptigels, Manchester Biogel) to assess their suitability as barriers. Alpha 1, 2, and 3 Peptigels were biocompatible, whereas Alpha 5 Peptigel caused a significant loss of cell viability. Furthermore, these Peptigels did not induce MMT of human and mouse mesothelial cells, whereas TGF-beta1 induced a morphological change and a significant increase in mesenchymal marker expression indicative of MMT. In vivo, Alpha 2 Peptigel was found to persist for up to 12 days using non-invasive fluorescence imaging after intraperitoneal application in mice. However, Alpha 2 Peptigel displayed no efficacy in adhesion prevention in a mouse caecal-side wall abrasion model compared with surgical controls. BMP4 prevented TGF-beta1- induced MMT of mouse mesothelial cells in vitro although when delivered with or without Alpha 2 hydrogel in vivo, BMP4 did not prevent adhesion formation compared with no-treatment control. In conclusion, novel peptide hydrogels are biocompatible in the peritoneum and show promise as drug delivery vehicles for adhesion prevention. Further studies are required to optimise the concentration of BMP4 for hydrogel delivery intraperitoneally, assess its release kinetics and determine efficacy using additional post-surgical adhesion models.

Date of Award	31 Dec 2022
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Alberto Saiani (Supervisor), Sarah Herrick (Supervisor) & Adrian Woolf (Supervisor)