CXCL12 in early mesenchymal progenitors is required for haematopoietic stem-cell maintenance.

Haematopoietic stem cells (HSCs) primarily reside in the bone marrow where signals generated by stromal cells regulate their self-renewal, proliferation and trafficking. Endosteal osteoblasts and perivascular stromal cells including endothelial cells, CXCL12-abundant reticular cells, leptin-receptor-positive stromal cells, and nestin-green fluorescent protein (GFP)-positive mesenchymal progenitors have all been implicated in HSC maintenance. However, it is unclear whether specific haematopoietic progenitor cell (HPC) subsets reside in distinct niches defined by the surrounding stromal cells and the regulatory molecules they produce. CXCL12 (chemokine (C-X-C motif) ligand 12) regulates both HSCs and lymphoid progenitors and is expressed by all of these stromal cell populations. Here we selectively deleted Cxcl12 from candidate niche stromal cell populations and characterized the effect on HPCs. Deletion of Cxcl12 from mineralizing osteoblasts has no effect on HSCs or lymphoid progenitors. Deletion of Cxcl12 from osterix-expressing stromal cells, which include CXCL12-abundant reticular cells and osteoblasts, results in constitutive HPC mobilization and a loss of B-lymphoid progenitors, but HSC function is normal. Cxcl12 deletion from endothelial cells results in a modest loss of long-term repopulating activity. Strikingly, deletion of Cxcl12 from nestin-negative mesenchymal progenitors using Prx1-cre (Prx1 also known as Prrx1) is associated with a marked loss of HSCs, long-term repopulating activity, HSC quiescence and common lymphoid progenitors. These data suggest that osterix-expressing stromal cells comprise a distinct niche that supports B-lymphoid progenitors and retains HPCs in the bone marrow, and that expression of CXCL12 from stromal cells in the perivascular region, including endothelial cells and mesenchymal progenitors, supports HSCs.

Kupffer cells protect liver sinusoidal endothelial cells from Fas-dependent apoptosis in sepsis by down-regulating gp130.

Endothelial cell (EC) dysfunction is a key feature of multiple organ injury, the primary cause of fatality seen in critically ill patients. Although the development of EC dysfunction in the heart and lung is well studied in sepsis, it remains unclear in the liver. Herein, we report that liver sinusoidal ECs (LSECs; defined as CD146(+)CD45(-)) exhibit increased intercellular adhesion molecule-1 (CD54) and Fas in response to sepsis induced by cecal ligation and puncture (CLP). By using magnetically enriched LSEC (CD146(+)) populations, we show evidence of marked apoptosis, with a twofold decline in viable LSECs in CLP animals compared with sham controls. These changes and increased serum alanine aminotransferase levels were all mitigated in septic Fas(-/-) and Fas ligand(-/-) animals. Although we previously reported increased numbers of Fas ligand expressing CD8(+) T lymphocytes in the septic liver, CD8(+) T-cell deficiency did not reverse the onset of LSEC apoptosis/damage. However, Kupffer cell depletion with clodronate liposomes resulted in greater apoptosis and Fas expression after CLP and a decrease in glycoprotein 130 expression on LSECs, suggesting that STAT3 activation may protect these cells from injury. Our results document a critical role for death receptor-mediated LSEC injury and show the first evidence that Kupffer cells are essential to the viability of LSECs, which appears to be mediated through glycoprotein 130 expression in sepsis.

Modeling dysbiosis of human NASH in mice: Loss of gut microbiome diversity and overgrowth of Erysipelotrichales.

BACKGROUND & AIM: Non-alcoholic steatohepatitis (NASH) is a severe form of non-alcoholic fatty liver disease (NAFLD) that is responsible for a growing fraction of cirrhosis and liver cancer cases worldwide. Changes in the gut microbiome have been implicated in NASH pathogenesis, but the lack of suitable murine models has been a barrier to progress. We have therefore characterized the microbiome in a well-validated murine NASH model to establish its value in modeling human disease. METHODS: The composition of intestinal microbiota was monitored in mice on a 12- or 24-week NASH protocol consisting of high fat, high sugar Western Diet (WD) plus once weekly i.p injection of low-dose CCl4. Additional mice were subjected to WD-only or CCl4-only conditions to assess the independent effect of these variables on the microbiome. RESULTS: There was substantial remodeling of the intestinal microbiome in NASH mice, characterized by declines in both species diversity and bacterial abundance. Based on changes to beta diversity, microbiota from NASH mice clustered separately from controls in principal coordinate analyses. A comparison between WD-only and CCl4-only controls with the NASH model identified WD as the primary driver of early changes to the microbiome, resulting in loss of diversity within the 1st week. A NASH signature emerged progressively at weeks 6 and 12, including, most notably, a reproducible bloom of the Firmicute order Erysipelotrichales. CONCLUSIONS: We have established a valuable model to study the role of gut microbes in NASH, enabling us to identify a new NASH gut microbiome signature.

Fecal IgA Levels Are Determined by Strain-Level Differences in Bacteroides ovatus and Are Modifiable by Gut Microbiota Manipulation.

Fecal IgA production depends on colonization by a gut microbiota. However, the bacterial strains that drive gut IgA production remain largely unknown. Here, we assessed the IgA-inducing capacity of a diverse set of human gut microbial strains by monocolonizing mice with each strain. We identified Bacteroides ovatus as the species that best induced gut IgA production. However, this induction varied bimodally across different B. ovatus strains. The high IgA-inducing B. ovatus strains preferentially elicited more IgA production in the large intestine through the T cell-dependent B cell-activation pathway. Remarkably, a low-IgA phenotype in mice could be robustly and consistently converted into a high-IgA phenotype by transplanting a multiplex cocktail of high IgA-inducing B. ovatus strains but not individual ones. Our results highlight the critical importance of microbial strains in driving phenotype variation in the mucosal immune system and provide a strategy to robustly modify a gut immune phenotype, including IgA production.

IBD-INFO Questionnaire: A Multicenter French Up-to-Date Survey of Patient Knowledge in Inflammatory Bowel Disease.

Background: It has been demonstrated in many chronic conditions, including inflammatory bowel disease (IBD), that better patient knowledge about pathology and treatment improves the course and management of disease. The aim of this study was to develop an updated self-questionnaire to assess patients' level of knowledge of IBD. Methods: The IBD-INFO included 3 parts: an original part (Q1) and 2 parts from the translation of the preexisting questionnaires Crohn's and Colitis Knowledge score (CCKNOW) (Q2) and Crohn's and Colitis Pregnancy Knowledge score (CCPKNOW) (Q3). The reliability and discriminatory ability of the questionnaire were validated in 3 groups of non-IBD volunteers with various theoretical knowledge levels. The final questionnaire (64 validated questions) was then tested on 364 in- and out- IBD patients from 4 French university hospitals. The score for each part of the questionnaire was calculated, and factors associated with low scores were identified by univariate and multivariate logistic regression analyses. Results: The scores obtained by the 3 non-IBD volunteer groups differed significantly (P < 0.0001), and the IBD-INFO questionnaire showed excellent internal reliability and consistency (α = 0.98). The median total score obtained by the IBD patients was 27/64 (range, 0-59), and scores for Q1, Q2, and Q3 were, respectively, 10/23 (range, 0-21), 11/24 (range, 0-23), and 4/17 (range, 0-16). In multivariate analysis, lack of a university degree, not being a member of a patient association, not receiving anti-tumor necrosis factor alpha (anti-TNFα) treatment, duration of IBD ≤3 years, male sex, and age >38 years were independent risk factors of a poor IBD-INFO knowledge score. The areas of knowledge least mastered were vaccination, IBD-related cancers, treatments, and pregnancy. Conclusions: Using the IBD-INFO, an updated self-administered questionnaire built to assess IBD patients' knowledge, several risk factors have been highlighted that allow better targeting of patients and areas requiring an improvement in the level of information.