Role of the serosa in intestinal anastomotic healing: insights from in-depth histological analysis of human and murine anastomoses.

BACKGROUND: Anastomotic leakage following colorectal surgery remains a significant complication despite advances in surgical techniques. Recent findings on serosal injury repair in coelomic cavities, such as the peritoneum, challenge the current understanding of the cellular origins and mechanisms underlying intestinal anastomotic healing. Understanding the contribution of each layer of the intestinal wall during anastomotic healing is needed to find new therapeutic strategies to prevent anastomotic leakage. The aim of this experimental study was to investigate the role of the serosal layer of the intestinal wall in anastomotic healing. MATERIALS AND METHODS: Comprehensive histologic analysis of human and murine anastomoses was performed to elucidate histologic changes in the different intestinal layers during anastomotic healing. In vivo staining of the extracellular matrix (ECM) in the serosal layer was performed using a fluorophore-conjugated N-hydroxysuccinimide-ester before anastomosis surgery in a murine model. RESULTS: Histological examination of both human and murine anastomoses revealed that closure of the serosal layer occurred first during the healing process. In vivo serosal ECM staining demonstrated that a significant portion of the newly formed ECM within the anastomosis was indeed deposited onto the serosal layer. Furthermore, mesenchymal cells within the anastomotic scar were positive for mesothelial cell markers, podoplanin and Wilms tumour protein. CONCLUSIONS: In this experimental study, the results suggest that serosal scar formation is an important mechanism for anastomotic integrity in intestinal anastomoses. Mesothelial cells may significantly contribute to scar formation during anastomotic healing through epithelial-to-mesenchymal transition, potentially suggesting a novel therapeutic target to prevent anastomotic leakage by enhancing physiological healing processes.

Fractal analysis of extracellular matrix for observer-independent quantification of intestinal fibrosis in Crohn's disease.

Prevention of intestinal fibrosis remains an unresolved problem in the treatment of Crohn's disease (CD), as specific antifibrotic therapies are not yet available. Appropriate analysis of fibrosis severity is essential for assessing the therapeutic efficacy of potential antifibrotic drugs. The aim of this study was to develop an observer-independent method to quantify intestinal fibrosis in surgical specimens from patients with CD using structural analysis of the extracellular matrix (ECM). We performed fractal analysis in fibrotic and control histological sections of patients with surgery for CD (n = 28). To specifically assess the structure of the collagen matrix, polarized light microscopy was used. A score to quantify collagen fiber alignment and the color of the polarized light was established. Fractal dimension as a measure for the structural complexity correlated significantly with the histological fibrosis score whereas lacunarity as a measure for the compactness of the ECM showed a negative correlation. Polarized light microscopy to visualize the collagen network underlined the structural changes in the ECM network in advanced fibrosis. In conclusion, observer-independent quantification of the structural complexity of the ECM by fractal analysis is a suitable method to quantify the degree of intestinal fibrosis in histological samples from patients with CD.

Perioperative Low-Dose Prednisolone Treatment Has Beneficial Effects on Postoperative Recovery and Anastomotic Healing in a Murine Colitis Model.

BACKGROUND AND AIMS: High-dose glucocorticoid treatment has been identified as a risk factor for anastomotic leakage in patients with inflammatory bowel disease [IBD] undergoing bowel resection surgery. By contrast, active disease during surgery is also associated with elevated morbidity. Perioperative low-dose treatment might be beneficial regarding postoperative outcomes by controlling disease activity. The present study is the first to investigate the dose-dependent effect of perioperative prednisolone therapy in a murine IBD model combining dextran sodium sulphate [DSS] colitis with intestinal anastomosis surgery. METHODS: In 84 10-week-old wild-type mice, a colorectal anastomosis was performed using a microsurgical technique. Half the animals received induction of chemical colitis with 2% DSS via drinking water prior to surgery. In both groups, one-third of the animals received daily oral administration of high-dose [0.533 mg/kg] and one-third low-dose [0.133 mg/kg] prednisolone. Evaluation was performed on postoperative days 3 and 7. RESULTS: While high-dose prednisolone treatment led to an increased anastomotic leakage rate in mice under colitis, low-dose prednisolone treatment limited preoperative disease activity and did not influence the leakage rate. Histological examination showed a beneficial effect of low-dose prednisolone treatment on microscopic abscess formation at the anastomotic site in DSS mice as well as an increased anastomotic healing score. CONCLUSIONS: We demonstrate a beneficial effect of perioperative short-term low-dose prednisolone treatment on intestinal anastomotic healing in the context of colitis. Perioperative use of short-term low-dose prednisolone treatment might be beneficial in IBD patients who need to undergo surgery during active disease.