Background: Experimental data suggest that bacterial translocation (BT) promotes systemic inflammation, portal hypertension, and circulatory dysfunction in advanced chronic liver disease (ACLD). Methods: Patients with ACLD undergoing hepatic venous pressure gradient (HVPG) measurement and absence of acute decompensation or infections were included (n = 249). Serum biomarkers of BT (lipopolysaccharide [LPS], lipoteichoic acid [LTA], bacterial DNA [bactDNA]), systemic inflammation and markers of circulatory dysfunction were assessed. T-cell subsets in intestinal biopsies (n = 7 ACLD, n = 4 controls) were analyzed by flow cytometry. Results: Patients had a median HVPG of 18 (12–21) mmHg and 56% had decompensated ACLD. LPS (0.04 [0.02–0.06] vs. 0.64 [0.30–1.06] EU/mL), LTA (4.53 [3.58–5.97] vs. 43.2 [23.2–109] pg/mL), and detection of bactDNA (≥ 5 pg/mL; 5% vs. 41%) were markedly higher in patients with ACLD than healthy controls (n = 40; p < 0.001) but were similar between different clinical stages of compensated and decompensated ACLD and displayed no meaningful correlation with HVPG and systemic hemodynamics. TNF-α and IL-10 correlated with LPS (Spearman’s r_s = 0.523, p < 0.001/r_s = 0.143, p = 0.024) but not with LTA. Presence of bactDNA was associated with higher LPS (0.54 [0.28–0.95] vs. 0.88 [0.32–1.31] EU/mL, p = 0.001) and TNF-α (15.3 [6.31–28.1] vs. 20.9 [13.8–32.9] pg/mL). Patients with ACLD exhibited a decreased CD4:CD8-ratio and increased T_H1-cells in the intestinal mucosa as compared to controls. During a median FU of 14.7 (8.20–26.5) months, bacterial antigens did not predict decompensation or liver-related death (in contrast to HVPG, IL-6, and MAP) as well as infections at 24 months. Conclusion: BT occurs already in early ACLD stages and triggers a systemic inflammatory response via TNF-α and IL-10. Interestingly, BT markers showed no clear correlation with portal hypertension and circulatory dysfunction in patients with stable ACLD. Clinical trial number: NCT03267615.

Hepatic immune function is compromised during cirrhosis. This study investigated the immune features of liver sinusoidal endothelial cells (LSECs) in two experimental models of cirrhosis. Dendritic cells, hepatic macrophages, and LSECs were isolated from carbon tetrachloride and bile duct-ligated rats. Gene expression of innate receptors, bacterial internalization, co-stimulatory molecules induction, and CD4+ T cell activation and differentiation were evaluated. Induced bacterial peritonitis and norfloxacin protocols on cirrhotic rats were also carried out. LSECs demonstrated an active immunosurveillance profile, as shown by transcriptional modulation of different scavenger and cell-adhesion genes, and their contribution to bacterial internalization. LSECs significantly increased their expression of CD40 and CD80 and stimulated CD4+ T cell activation marker CD71 in both models. The pro-inflammatory Th17 subset was expanded in CCl₄-derived LSECs co-cultures. In the bile duct ligation (BDL) model, CD4+ T cell differentiation only occurred under induced bacterial peritonitis conditions. Differentiated pro-inflammatory Th cells by LSECs in both experimental models were significantly reduced with norfloxacin treatment, whereas Foxp3 tolerogenic Th CD4+ cells were expanded. Conclusion: LSECs’ participation in the innate-adaptive immune progression, their ability to stimulate pro-inflammatory CD4+ T cells expansion during liver damage, and their target role in norfloxacin-induced immunomodulation granted a specific competence to this cell population in cirrhosis.

Background: The global burden of liver disease and cirrhosis has been progressively increasing in the last decade. The interplay between gut microbiota and immune system and the bidirectional relationship with the liver, known as the gut-liver axis, has arisen as a fundamental aspect of liver disease. Summary: Alterations of the gut microbiome have been described and include both dysbiotic microbial signatures and intestinal bacterial overgrowth. The integrity of the intestinal epithelial barrier is essential for preventing the access of harmful substances and bacterial products into the host. Bacterial translocation due to altered host-microbiota interactions triggers local immune cell activation and facilitates a chronic inflammatory state that can ultimately lead to immune exhaustion, characteristic of cirrhosis. In cirrhosis, breakdown of the gut vascular barrier allows access of bacterial products to portal blood circulation and facilitates their influx into the liver, further contributing to disease progression. Key Messages: A better understanding of the contributing factors to pathological bacterial translocation and the impact of dysbiosis in liver disease will lead to achieve innovative therapeutic strategies in cirrhosis.

MiRNAs are short single‐stranded noncoding RNAs that participate as epigenetic regulators in inflammatory bowel disease. Most miRNAs detectable in serum are concentrated in exosomes, with relevant cargo for immunobiological processes. We set to evaluate the exosomes miRNAs content in the serum of patients with Crohn's disease (CD) and run a prospective observational study on CD patients on biological monotherapy and healthy controls. miRNA cargo was evaluated in peripheral blood‐derived exosomes. Serum autophagy and inflammatory substrates were measured. Patients were followed for 6 months. Patients ( n = 28) showed an overexpression of miR‐376a‐3p and a downregulation of miR‐20a‐5p compared to controls ( n = 10), without significant differences between patients according to biologics. Serum autophagy substrates ATG4C ( r = .57; p = .001) and ACRV1C ( r = .66; p = .001) inversely correlated with miR‐376a‐3p expression, whereas IGF1R correlated with miR‐20a‐5p expression ( r = .42; p = .02). Th1‐related cytokines correlated with miR‐376a‐3p expression, whereas the Th17‐associated cytokines inversely correlated with miR‐20a‐5p expression. Smoking ( β = −2.301 CI 95% −3.790/−0.811, p = .004) remained as independent factor related to the overexpression of miR‐376a‐3p, whereas diagnosis before 16 years of age ( β = 2.044 CI 95% 0.934/3.154, p = .001) and a younger age of patients ( β = −.720 CI 95% −0.108/−0.035, p = .001) were related to decreased miR‐20a‐5p expression. Seven patients (25%) had a flare in the 6‐month follow‐up. Patients with overexpression of miR‐376a‐3p at the baseline showed an increased risk of flare during this period (OR 0.475 [0.237–0.950], p = .035). Finally, a comparative miRNA signature between biologic monotherapies was also explored. Targeting miR‐376a‐3p and miR‐20a‐5p epigenetic regulators may yield homeostatic effects on relevant biological processes related to disease progression in CD patients.

Intestinal microbiota can modulate portal hypertension through the regulation of the intestinal vasculature. We have recently demonstrated that bacterial antigens activate Paneth cells (PCs) to secrete products that regulate angiogenesis and portal hypertension. In the present work we hypothesized that Paneth cells regulate the development of lymphatic vessels under the control of intestinal microbiota during experimental portal hypertension. We used a mouse model of inducible PCs depletion (Math1^Lox/LoxVilCreER^T2) and performed partial portal vein ligation (PPVL) to induce portal hypertension. After 14 days, we performed mRNA sequencing and evaluated the expression of specific lymphangiogenic genes in small intestinal tissue. Intestinal and mesenteric lymphatic vessels proliferation was assessed by immunohistochemistry. Intestinal organoids with or without PCs were exposed to pathogen-associated molecular patterns, and conditioned media (CM) was used to stimulate human lymphatic endothelial cells (LECs). The lymphangiogenic activity of stimulated LECs was assessed by tube formation and wound healing assays. Secretome analysis of CM was performed using label-free proteomics quantification methods. Intestinal immune cell infiltration was evaluated by immunohistochemistry. We observed that the intestinal gene expression pattern was altered by the absence of PCs only in portal hypertensive mice. We found a decreased expression of specific lymphangiogenic genes in the absence of PCs during portal hypertension, resulting in a reduced proliferation of intestinal and mesenteric lymphatic vessels as compared to controls. In vitro analyses demonstrated that lymphatic tube formation and endothelial wound healing responses were reduced significantly in LECs treated with CM from organoids without PCs. Secretome analyses of CM revealed that PCs secrete proteins that are involved in lipid metabolism, cell growth and proliferation. Additionally, intestinal macrophages infiltrated the ileal mucosa and submucosa of mice with and without Paneth cells in response to portal hypertension. Our results suggest that intestinal microbiota signals stimulate Paneth cells to secrete factors that modulate the intestinal and mesenteric lymphatic vessels network during experimental portal hypertension.