Intestinal epithelial Cldn-7 regulates intestinal inflammation by altering the gut microbiota.

BACKGROUND AND AIM: Tight junctions maintain gut homeostasis by forming a physical barrier that protects the gut from invasion by microbiota. Cldn-7 is an important component involved in this protection, but the relationship between Cldn-7, intestinal inflammation, and gut microbiota has not been clarified. Here, we hypothesize that Cldn-7 depletion affects intestinal inflammation by altering the gut microbiota. METHODS: Based on the induced intestinal condition of Cldn-7 knockout mice (Cldn7fl/fl;villin-CreaERT2), we established the intestinal flora depletion model and colitis model by antibiotic drinking and feeding with dextran sodium sulfate (DSS). The environment of Cldn-7 gene deletion mice was changed by co-housing experiment. AB-PAS staining and Muc2 were used to detect the effect of co-housing and Cldn-7 deficiency on the mucus layer after flora depletion. qRT-PCR was used to detect the expression of intestinal inflammatory factors and AMPs in mice. Feces were collected and proportions of microbiota were analyzed by 16 S rRNA amplicon sequencing. RESULTS: Mice in the co-housing experiment had altered intestinal microbiota, including diversity, composition, and functional prediction, compared to controls. Intestinal inflammation was restored to some extent following altered intestinal microbiota. The intestinal inflammation caused by Cldn-7 deficiency and susceptibility to DSS could be reduced after antibiotic administration compared to controls, in terms of phenotype, pathological changes, inflammatory factors, mucus barrier, and expression of AMPs. CONCLUSIONS: In analyses of intestinal tissues, colitis induction, and gut microbiota in mice with intestinal disruption of Cldn-7, we found this protein to prevent intestinal inflammation by regulating the gut microbiota. Cldn-7might therefore be an important mediator of host-microbiome interactions. Our research has revealed that Cldn-7 plays an indispensable role in maintaining intestinal homeostasis by regulating the gut microbiota and impacting intestinal inflammation. These findings provide new insights into the pathogenesis of ulcerative colitis.

Claudin-7 is essential for the maintenance of colonic stem cell homoeostasis via the modulation of Wnt/Notch signalling.

Intestinal stem cells (ISCs) play a crucial role in the continuous self-renewal and recovery of the intestinal epithelium. In previous studies, we have revealed that the specific absence of Claudin-7 (Cldn-7) in intestinal epithelial cells (IECs) can lead to the development of spontaneous colitis. However, the mechanisms by which Cldn-7 maintains homeostasis in the colonic epithelium remain unclear. Therefore, in the present study, we used IEC- and ISC-specific Cldn-7 knockout mice to investigate the regulatory effects of Cldn-7 on colonic Lgr5+ stem cells in the mediation of colonic epithelial injury and repair under physiological and inflammatory conditions. Notably, our findings reveal that Cldn-7 deletion disrupts the self-renewal and differentiation of colonic stem cells alongside the formation of colonic organoids in vitro. Additionally, these Cldn-7 knockout models exhibited heightened susceptibility to experimental colitis, limited epithelial repair and regeneration, and increased differentiation toward the secretory lineage. Mechanistically, we also established that Cldn-7 facilitates the proliferation, differentiation, and organoid formation of Lgr5+ stem cells through the maintenance of Wnt and Notch signalling pathways in the colonic epithelium. Overall, our study provides new insights into the maintenance of ISC function and colonic epithelial homoeostasis.

The role of intestinal microecology in inflammatory bowel disease and colorectal cancer: A review.

Intestinal microecology is a dominant and complex microecological system in human body. Generally, intestinal microecosystem consists of normal symbiotic flora and its living environment (including intestinal epithelial tissue and intestinal mucosal immune system). Commensal flora is the core component of microecology. Both structures of intestinal mucosa and functions of immune system are essential to maintain homeostasis of intestinal microecosystem. Under normal conditions, intestinal microorganisms and intestinal mucosa coordinate with each other to promote host immunity. When certain factors in the intestine are altered, such as disruption of the intestinal barrier causing dysbiosis of the intestinal flora, the immune system of the host intestinal mucosa makes a series of responses, which leads to the development of intestinal inflammation and promotes colorectal cancer. In this review, to further understand the relationship between intestinal microecology and intestinal diseases, we systematically elaborate the composition of the intestinal mucosal immune system, analyze the relationship between intestinal flora and mucosal immune system, and the role of intestinal flora on intestinal inflammatory diseases and colorectal cancer.

Clinical outcomes of parenchymal-sparing versus anatomic resection for colorectal liver metastases: a systematic review and meta-analysis.

BACKGROUND: The advantages of parenchymal-sparing resection (PSR) over anatomic resection (AR) of colorectal liver metastases (CRLM) remain controversial. Here, we aim to evaluate their safety and efficacy. METHODS: A systematic review and meta-analysis of short-term perioperative outcomes and long-term oncological outcomes for PSR and AR were performed by searching Pubmed, Embase, the Cochrane Library and Web of Science databases. RESULTS: Twenty-two studies were considered eligible (totally 7228 patients: AR, n = 3154 (43.6%) vs. PSR, n = 4074 (56.4%)). Overall survival (OS, HR = 1.08, 95% CI: 0.95-1.22, P = 0.245) and disease-free survival (DFS, HR = 1.09, 95% CI: 0.94-1.28, P = 0.259) were comparable between the two groups. There were no significant differences in 3-year OS, 5-year OS, 3-year DFS, 5-year DFS, 3-year liver recurrence-free survival (liver-RFS) and 5-year liver-RFS. In terms of perioperative outcome, patients undergoing AR surgery were associated with prolonged operation time (WMD = 51.48 min, 95% CI: 29.03-73.93, P < 0.001), higher amount of blood loss (WMD = 189.92 ml, 95% CI: 21.39-358.45, P = 0.027), increased intraoperative blood transfusion rate (RR = 2.24, 95% CI: 1.54-3.26, P < 0.001), prolonged hospital stay (WMD = 1.00 day, 95% CI: 0.34-1.67, P = 0.003), postoperative complications (RR = 2.28, 95% CI: 1.88-2.77, P < 0.001), and 90-day mortality (RR = 3.08, 95% CI: 1.88-5.03, P < 0.001). While PSR surgery was associated with positive resection margins (RR = 0.77, 95% CI: 0.61-0.97, P = 0.024), intrahepatic recurrence (RR = 0.90, 95% CI: 0.82-0.98, P = 0.021) and repeat hepatectomy (RR = 0.64, 95% CI: 0.55-0.76, P < 0.001). CONCLUSION: Considering relatively acceptable heterogeneity, PSR had better perioperative outcomes without compromising oncological long-term outcomes. However, these findings must be carefully interpreted, requiring more supporting evidence. TRIAL REGISTRATION: PROSPERO registration number: CRD42023445332.