A40 GUT MICROBIOTA PROMOTES NUTRIENT AVAILABLITY AND PATHOGENESIS OF AN ATTACHING/ EFFACING BACTERIAL PATHOGEN

Background

Our gut microbiota plays an important role in protecting the gastrointestinal (GI) tract from invading enteric pathogens. Much of this colonization resistance is mediated by limiting nutrient availability, however, enteric pathogens have evolved strategies to subvert this competition, utilizing commensal metabolites to facilitate their infection. Access to nutrients is not only crucial for a pathogen’s metabolic fitness, but can also drive the expression of virulence factors, a process high in energy demands. In addition, enteric pathogens, such as the attaching and effacing (A/E) bacterium Citrobacter rodentium, must cross the colonic mucus layer that normally prevents their direct access to the underlying epithelium. Intestinal mucus is comprised of highly glycosylated mucins, with the sugar sialic acid frequently occupying the terminal position of their O-glycan side chains. We hypothesize that C. rodentium utilizes commensal-liberated mucin sugars, such as sialic acid, as nutrients and signals to promote its virulence.

Purpose

This study investigates the mechanisms by which A/E pathogens reach the colonic mucosal surface, and the role played by commensal microbes in facilitating the infection.

Method

Expression of virulence factors secreted by C. rodentium in the presence or absence of sialic acid was analyzed by SDS-PAGE and mass spectrometry. Next, we infected specific-pathogen free (SPF), germfree (GF), and previously GF C57Bl/6 mice mono-colonized with Bacteroides thetaotaomicron, a mucus-degrading commensal, to examine their susceptibility to C. rodentium and to measure the levels of free sialic acid in their feces.

Result(s)

Sensing of sialic acid by C. rodentium, was found to induce the secretion of several key virulence proteins, enhancing the pathogen’s migration across the colonic mucus layer and adhesion to the underlying epithelium. Access to sialic acid within the gut environment was enhanced in the presence of microbiota, as the levels of free sialic acid were low in GF mice. Interestingly, despite GF mice carrying very high C. rodentium burdens, passage across the mucus layer and infection of their colonic epithelium was impaired as compared to SPF mice. Notably, B. thetaotaomicron was found to degrade whole mucus in vitro, facilitating its consumption by C. rodentium for growth, while B. thetaotaomicron mono-colonized GF mice showed increased susceptibility to colonic infection by C. rodentium.

Conclusion(s)

We demonstrate that although commensal microbes promote colonization resistance, as an A/E pathogen infection establishes, specific commensal bacteria accelerate infection in the GI tract by releasing an important nutrient, ie. sialic acid, from mucus. Access to sialic acid promotes C. rodentium virulence by inducing the key virulence factors that facilitate its translocation across the mucus layer as well as adhesion to the epithelium, thereby expediting disease progression.

Please acknowledge all funding agencies by checking the applicable boxes below

CCC, CIHR, Other

Please indicate your source of funding;

CH.I.L.D. Foundation

Disclosure of Interest

None Declared

A15 GENETIC OR DIET-ASSOCIATED DEFECTS IN MUCUS FACILITATE ULCERATIVE COLITIS PATHOBIONT-DRIVEN COLITIS

Background

The Inflammatory Bowel Diseases (IBD), Crohn’s Disease (CD) and ulcerative colitis (UC) affect > 270,000 Canadians and are increasing in incidence. Ileal CD has been linked to the overgrowth of mucosal adherent E. coli. Recent studies have also implicated the adherence of Escherichia coli pathobionts to the colonic mucosa of UC patients. Using the representative UC E. coli pathobiont p19A, we recently demonstrated it aggravated chemical-induced colitis in susceptible mice, through the actions of the toxin alpha-hemolysin, and by adhering to the inflamed colonic mucosa via the adhesin FimH. It is less clear what host factors control susceptibility to the UC pathobionts. One of the potential candidates is the glycosylated mucin (Muc2) which forms the mucus layer that covers the colonic epithelium and is often impaired in UC patients.

Purpose

To define the role of mucus structure and function in determining susceptibility to the p19A pathobiont, and its ability to cause colitis in mice.

Method

In vitro growth was assessed to test p19A’s ability to utilize mucin-derived sugars as nutrients. Susceptibility to p19A was tested in two mouse models of colonic mucus impairment. The first is a mouse strain deficient in core 1 derived O-glycans in their intestinal epithelial cells (IEC C1galt1^-/-), resulting in reduced Muc2 glycosylation, and thus a thin and impaired mucus barrier. The second model involves feeding wildtype (WT) C57BL/6CR mice a fiber-free (FF) diet, resulting in a significantly thinner colonic mucus layer. The mice were subsequently orally gavaged with p19A and their susceptibility determined by p19A burdens, intestinal histopathology, inflammatory cytokine and short chain fatty acid (SCFA) production.

Result(s)

When tested in vitro, the p19A pathobiont was found to use an array of mucin-derived sugars as sole carbon source to proliferate. Following oral gavage of WT mice fed a normal diet, immunostaining identified p19A within the colonic mucus but it did not reach the colonic mucosa or cause disease. In contrast, p19A was found at the colonic mucosal surface of mucus-defective IEC C1galt1^-/- mice (as compared to IEC C1galt1^flox/flox mice) and in WT mice fed a fiber-free diet. This mucosal adherence was associated with increased body weight loss during the course of infection, as well as increased p19A burdens, colonic pathology and pro-inflammatory cytokine expression. Especially fiber-free diet-fed mice showed reduced SCFA levels in their feces at baseline. When the mice were given exogenous SCFA (tributyrin) orally, p19A infection was reduced.

Conclusion(s)

Our results indicate that UC E. coli pathobionts are able to dwell within colonic mucus and utilize mucin sugars as nutrients. Moreover, they can reach the mucosal surface and induce colitis in hosts suffering genetic or diet-based mucus dysfunction. In part, this susceptibility reflects the important role played by mucus in the production of SCFA, suggesting potential therapeutic approaches for patients suffering UC.

Please acknowledge all funding agencies by checking the applicable boxes below

CCC, CIHR

Disclosure of Interest

None Declared

Application of the neuropeptide NPVF to enhance angiogenesis and osteogenesis in bone regeneration

The brain-bone regulatory system regulates skeletal homeostasis via bioactive neuropeptides, yet the underlying mechanism remains elusive. Here, we report the role of the neuropeptide VF (NPVF, VPNLPQRF-NH2) in enhancing both angiogenesis and osteogenesis in a rat skeletal system and the potential pathways involved. An in vitro study revealed that NPVF not only promotes migration and angiogenesis of human umbilical vein endothelial cells (HUVECs) by activating NPFFR1, which leads to upregulation of miR-181c-3p and downregulation of Argonaute1 (AGO1), but also mediates osteogenic differentiation of bone mesenchymal stem cells (BMSCs) via the Wnt/β-catenin signaling pathway. To improve the stability and bioavailability and thus efficacy of NPVF as a promoter of in vivo bone regeneration, we genetically engineered amyloid-NPVF-fusion proteins and utilized them as self-assembling nanofiber coatings to treat bone defects in a rat calvarial defect model. We found that a porous hydroxyapatite scaffold loaded with the NPVF peptide-fused amyloid coating substantially enhanced angiogenesis and site-specific fresh bone in-growth when implanted in calvarial defects. Taken together, our work uncovered a previously undefined crosstalk between the brain and bone by unveiling the role of NPVF in bone tissue and demonstrated a viable method for promoting bone tissue repairs based upon self-assembling NPVF-containing protein coatings.

A novel signature constructed by super-enhancer-related genes for the prediction of prognosis in hepatocellular carcinoma and associated with immune infiltration

Background

Super-enhancer (SE) refers to a regulatory element with super transcriptional activity, which can enrich transcription factors and drive gene expression. SE-related genes play an important role in the pathogenesis of malignant tumors, including hepatocellular carcinoma (HCC).

Methods

The SE-related genes were obtained from the human super-enhancer database (SEdb). Data from the transcriptome analysis and related clinical information with HCC were obtained from The Cancer Genome Atlas (TCGA) and the International Cancer Genome Consortium (ICGC) database. The upregulated SE-related genes from TCGA-LIHC were identified by the DESeq2R package. Multivariate Cox regression analysis was used to construct a four-gene prognostic signature. According to the median risk score, HCC patients were divided into high-risk and low-risk group patients.

Results

The Kaplan-Meier (KM) curve showed that a significantly worse prognosis was found for the high-risk group (P<0.001). In the TCGA-LIHC dataset, the area under the curve (AUC) values were 0.737, 0.662, and 0.667 for the model predicting overall survival (OS) over 1-, 3-, and 5- years, respectively, indicating the good prediction ability of our prediction model. This model's prognostic value was further validated in the LIRI-JP dataset and HCC samples (n=65). Furthermore, we found that higher infiltration level of M0 macrophages and upregulated of CTLA4 and PD1 in the high-risk group, implying that immunotherapy could be effective for those patients.

Conclusion

These results provide further evidence that the unique SE-related gene model could accurately predict the prognosis of HCC.

[Progress in perioperative management of ABO-incompatible pediatric liver transplantation]

ABO incompatible(ABO-I) liver grafts will affect the prognosis of liver transplantation. With the improvement of perioperative treatment,including plasma exchange,rituximab,splenectomy,etc.,the prognosis of ABO-I liver transplantation has been greatly improved. Because children's immune systems are not fully developed,the perioperative management of ABO-I pediatric liver transplantation is significantly different from that of adults. Reducing the perioperative anti-donor ABO antibody titer is the key to the perioperative management of ABO-I liver transplantation. This article summarizes literatures on the perioperative management of ABO-I pediatric liver transplantation, including the perioperative anti-rejection regimen in pediatric recipients of different ages, splenectomy, postoperative monitoring and postoperative complications, etc.

[Clinical characteristics of 18 children with chronic nonbacterial osteomyelitis]

Objective: To investigate the clinical features of children with chronic nonbacterial osteomyelitis (CNO), and raise awareness among clinicians. Methods: In this retrospective study, 18 patients with CNO who were diagnosed in Children's Hospital of Fudan University from January 2015 to December 2021 were included. Results: Eighteen children with CNO (12 males, 6 females) were identified. Their age at onset was 9 (5, 11) years, the delay in diagnosis was 2 (1, 6) months, and follow-up-was 17 (8, 34) months. The most common symptoms were fever in 14 children, as well as bone pain and (or) arthralgia in 14 children. In terms of laboratory results, normal white blood cell counts were observed at onset in 17 patients; increased erythrocyte sedimentation rate (ESR) in all patients; increased C reactive protein (CRP) over the normal value in 14 patients. Of the 18 patients, 2 had positive antinuclear antibodies, while none had positive human leukocyte antigen-B27 or rheumatoid factor. Imaging examination revealed that all the patients had symmetrical and multifocal skeletal lesions. The number of structural lesions detected by imaging investigation was 8 (6, 11). The most frequently affected bones were tibia in 18 patients and femur in 17 patients. Bone biopsy was conducted in 14 patients and acute or chronic osteomyelitis manifested with inflammatory cells infiltration were detected. Magnetic resonance imaging (MRI) found bone lesions in all the patients and bone scintigraphy were positive in 13 patients. All the patients were treated with nonsteroidal anti-inflammatory drugs, among whom 10 cases also treated with oral glucocorticoids, 9 cases with traditional disease modifying anti-rheumatic drugs, 8 cases with bisphosphonates and 6 cases with tumor necrosis factor inhibitors. The pediatric chronic nonbacterial osteomyelitis disease activity score, increased by 70% or more in 13 patients within the initial 6-month follow-up. Conclusions: The clinical manifestations of CNO are lack of specificity. The first symptom of CNO is fever, with or without bone pain and (or) arthralgia, with normal peripheral blood leukocytes, elevated CRP and (or) ESR. Whole body bone scanning combined with MRI can early detect osteomyelitis at subclinical sites, and improve the diagnostic rate of CNO.

Effect of ventilation mode on postoperative pulmonary complications following lung resection surgery: a randomised controlled trial

The effect of intra-operative mechanical ventilation modes on pulmonary outcomes after thoracic surgery with one-lung ventilation has not been well established. We evaluated the impact of three common ventilation modes on postoperative pulmonary complications in patients undergoing lung resection surgery. In this two-centre randomised controlled trial, 1224 adults scheduled for lung resection surgery with one-lung ventilation were randomised to one of three groups: volume-controlled ventilation; pressure-controlled ventilation; and pressure-control with volume guaranteed ventilation. Enhanced recovery after surgery pathways and lung-protective ventilation protocols were implemented in all groups. The primary outcome was a composite of postoperative pulmonary complications within the first seven postoperative days. The outcome occurred in 270 (22%), with 87 (21%) in the volume control group, 89 (22%) in the pressure control group and 94 (23%) in the pressure-control with volume guaranteed group (p = 0.831). The secondary outcomes also did not differ across study groups. In patients undergoing lung resection surgery with one-lung ventilation, the choice of ventilation mode did not influence the risk of developing postoperative pulmonary complications. This is the first randomised controlled trial examining the effect of three ventilation modes on pulmonary outcomes in patients undergoing lung resection surgery.