Distant Organs Research Articles

Advances in cancer mechanobiology: Metastasis, mechanics, and materials.

Within the tumor microenvironment (TME), tumor cells are exposed to numerous mechanical forces, both internally and externally, which contribute to the metastatic cascade. From the initial growth of the tumor to traveling through the vasculature and to the eventual colonization of distant organs, tumor cells are continuously interacting with their surroundings through physical contact and mechanical force application. The mechanical forces found in the TME can be simplified into three main categories: (i) shear stress, (ii) tension and strain, and (iii) solid stress and compression. Each force type can independently impact tumor growth and progression. Here, we review recent bioengineering strategies, which have been employed to establish the connection between mechanical forces and tumor progression. While many cancers are explored in this review, we place great emphasis on cancers that are understudied in their response to mechanical forces, such as ovarian and colorectal cancers. We discuss the major steps of metastatic transformation and present novel, recent advances in model systems used to study how mechanical forces impact the study of the metastatic cascade. We end by summarizing systems that incorporate multiple forces to expand the complexity of our understanding of how tumor cells sense and respond to mechanical forces in their environment. Future studies would also benefit from the inclusion of time or the aspect of mechanical memory to further enhance this field. While the knowledge of mechanical forces and tumor metastasis grows, developing novel materials and in vitro systems are essential to providing new insight into predicting, treating, and preventing cancer progression and metastasis.

Multilayered Immunity by Tissue-Resident Lymphocytes in Cancer.

Lymphocytes spanning the entire innate-adaptive spectrum can stably reside in tissues and constitute an integral component of the local defense network against immunological challenges. In tight interactions with the epithelium and endothelium, tissue-resident lymphocytes sense antigens and alarmins elicited by infectious microbes and abiotic stresses at barrier sites and mount effector responses to restore tissue homeostasis. Of note, such a host cell-directed immune defense system has been recently demonstrated to surveil epithelial cell transformation and carcinoma development, as well as cancer cell metastasis, at selected distant organs and thus represents a primordial cancer immune defense module. Here we review how distinct lineages of tissue-resident innate lymphoid cells, innate-like Tcells, and adaptive Tcells participate in a form of multilayered cancer immunity in murine models and patients, and how their convergent effector programs may be targeted through both shared and private regulatory pathways for cancer immunotherapy. Expected final online publication date for the Annual Review of Immunology, Volume 42 is April 2024. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Lemierre’s syndrome in pediatric population

Introduction: Lemierre’s syndrome is a rare, potentially fatal complication of upper respiratory tract infections, occurring mainly in young, previously healthy individuals. It is defined as postanginal septicaemia accompanied by thrombosis of the internal jugular vein and formation of abscesses in distant organs. Characteristic symptoms include deterioration of patient’s condition on the 4th–7th day of the management of primary infection, with the recurrence of fever and unilateral swelling and painfulness of the neck. Aims: The analysis of pediatric cases of Lemierre’s syndrome as described in the literature over the last 30 years; presentation of own experience and clinical observations in pediatric patients receiving treatment for Lemierre’s syndrome. Material and methods: A search of the literature available through the PubMed platform was carried out using the query terms “Lemierre syndrome” and “children”. A total of 73 pediatric cases reported on in papers published in English literature within the time span of 1980 through 2023 were included in the analysis. Results: As shown by the analysis of the 73 pediatric cases of Lemierre’s syndrome, the most common causes of the disease were acute pharyngitis and acute otitis media. The presence of the bacterial species Fusobacterium necrophorum was established in the blood cultures of more than one half of the patient group. Distant complications were most frequently observed in the lungs while the most common locations of thrombosis included the internal jugular vein and the sigmoid sinus. Intravenous antibiotic therapy was delivered to all patients, many of whom required additional surgical intervention and/or anticoagulation treatment. Conclusions: In most cases, Lemierre’s syndrome is a complication of acute pharyngitis and acute otitis media. Despite the presence of severe distant organ complications and extensive thrombotic lesions within the venous vessels, complete recovery is achieved in most cases in the pediatric population. The treatment of Lemierre’s syndrome is based primarily on broad-spectrum antibiotic therapy, with surgical interventions and/or anticoagulant therapy being also required in some cases. As of the present, no uniform guidelines have been established for the use of anticoagulant therapy, particularly in the pediatric population.

Bioinformatics analysis for the identification of Sprouty-related EVH1 domain-containing protein 3 expression and its clinical significance in thyroid carcinoma

The poorly differentiated thyroid carcinoma (THCA) subtype is associated with an aggressive disease course, a less favorable overall prognosis, and an increased risk of distant organ metastasis. In this study, our objective was to explore the potential utility of the Sprouty-related EVH1 domain-containing protein 3 (SPRED3) as a biomarker for early diagnosis and prognosis in THCA patients. The differentially expressed prognostic-related genes associated with THCA were identified by querying The Cancer Genome Atlas (TCGA) database. The difference in the expression of the SPRED3 gene between thyroid carcinoma (THCA) tissues and normal tissues was analyzed using data from The Cancer Genome Atlas (TCGA) and further validated through immunohistochemistry. Univariate and multivariate Cox regression models were used, along with clinical information from THCA patients, to analyze the prognostic value of the SPRED3 gene in THCA patients. Functional enrichment analysis was subsequently performed to elucidate the molecular mechanisms underlying the regulatory effects of the SPRED3 gene on thyroid carcinoma. Additionally, we calculated the percentage of infiltrating immune cells in THCA patients and evaluated their correlation with SPRED3 gene expression. Compared with those in noncancerous thyroid tissue, the gene and protein expression levels of SPRED3 were found to be elevated in thyroid carcinoma tissues. Furthermore, the expression of SPRED3 in thyroid carcinoma exhibited significant correlations with tumor location, histological grade, pathological stage, and tumor node metastasis classification (TNM) stage. Univariate and multivariate Cox proportional hazards (Cox) regression analyses demonstrated that SPRED3 could serve as an independent prognostic factor for predicting the overall survival of THCA patients. The results of functional enrichment analysis suggested the potential involvement of SPRED3 in the regulation of extracellular matrix organization, epidermal development, signaling receptor activator activity, skin development, receptor ligand activity, glycosaminoglycan binding, neuroactive ligand‒receptor interaction, the IL-17 signaling pathway, and the PI3K-Akt signaling pathway. Additionally, there were significant correlations between the expression level of the SPRED3 gene and the infiltration of various immune cells (eosinophils, central memory T cells, neutrophils, macrophages, and NK cells) within the thyroid tumor microenvironment. SPRED3 can be used as a prognostic biomarker in patients with THCA could potentially be therapeutic target for THCA.

The Keratinocyte in the Picture Cutaneous Melanoma Microenvironment.

Melanoma progression is a multistep evolution from a common melanocytic nevus through a radial superficial growth phase, the invasive vertical growth phase finally leading to metastatic dissemination into distant organs. Melanoma aggressiveness largely depends on the propensity to metastasize, which means the capacity to escape from the physiological microenvironment since tissue damage due to primary melanoma lesions is generally modest. Physiologically, epidermal melanocytes are attached to the basement membrane, and their adhesion/migration is under the control of surrounding keratinocytes. Thus, the epidermal compartment represents the first microenvironment responsible for melanoma spread. This complex process involves cell-cell contact and a broad range of secreted bioactive molecules. Invasion, or at the beginning of the microinvasion, implies the breakdown of the dermo-epidermal basement membrane followed by the migration of neoplastic melanocytic cells in the superficial papillary dermis. Correspondingly, several experimental evidences documented the structural and functional rearrangement of the entire tissue surrounding neoplasm that in some way reflects the atypia of tumor cells. Lastly, the microenvironment must support the proliferation and survival of melanocytes outside the normal epidermal-melanin units. This task presumably is mostly delegated to fibroblasts and ultimately to the self-autonomous capacity of melanoma cells. This review will discuss remodeling that occurs in the epidermis during melanoma formation as well as skin changes that occur independently of melanocytic hyperproliferation having possible pro-tumoral features.

Anticancer Therapy Targeting Cancer-Derived Extracellular Vesicles.

Extracellular vesicles (EVs) are natural lipid nanoparticles secreted by most types of cells. In malignant cancer, EVs derived from cancer cells contribute to its progression and metastasis by facilitating tumor growth and invasion, interfering with anticancer immunity, and establishing premetastasis niches in distant organs. In recent years, multiple strategies targeting cancer-derived EVs have been proposed to improve cancer patient outcomes, including inhibiting EV generation, disrupting EVs during trafficking, and blocking EV uptake by recipient cells. Developments in EV engineering also show promising results in harnessing cancer-derived EVs as anticancer agents. Here, we summarize the current understanding of the origin and functions of cancer-derived EVs and review the recent progress in anticancer therapy targeting these EVs.

Current Advances in the Use of Tissue Engineering for Cancer Metastasis Therapeutics.

Cancer is a leading cause of death worldwide and results in nearly 10 million deaths each year. The global economic burden of cancer from 2020 to 2050 is estimated to be USD 25.2 trillion. The spread of cancer to distant organs through metastasis is the leading cause of death due to cancer. However, as of today, there is no cure for metastasis. Tissue engineering is a promising field for regenerative medicine that is likely to be able to provide rehabilitation procedures to patients who have undergone surgeries, such as mastectomy and other reconstructive procedures. Another important use of tissue engineering has emerged recently that involves the development of realistic and robust in vitro models of cancer metastasis, to aid in drug discovery and new metastasis therapeutics, as well as evaluate cancer biology at metastasis. This review covers the current studies in developing tissue-engineered metastasis structures. This article reports recent developments in in vitro models for breast, prostate, colon, and pancreatic cancer. The review also identifies challenges and opportunities in the use of tissue engineering toward new, clinically relevant therapies that aim to reduce the cancer burden.

SATB1 mediated tumor colonization and β-catenin nuclear localization are associated with colorectal cancer progression

ABSTRACT Colorectal cancer (CRC) is a malignancy with high incidence and poor prognosis. It is urgent to identify valuable biomarkers for early diagnosis and potent therapeutic targets. It has been reported that SATB1 is associated with the malignant progression in CRC. To explore the role of SATB1 in CRC progression and the underlying mechanism, we evaluated the expression of SATB1 in the paired CRC tissues with immunohistochemistry. The results showed that the expression of SATB1 in lymph node metastasis was higher than that in primary lesion, and that in distant organ metastasis was higher than that in primary lesion. The retrospective analysis showed that patients with high expression of SATB1 had a significantly worse prognosis than those with negative and moderate expression. In vitro experiments that employing SATB1 over-expressing and depleted CRC cell lines confirmed that SATB1 contributes to cell proliferation and colonization, while inhibiting cell motility. Furthermore, the tissue immunofluorescence assay, Co-IP and Western blot were conducted to reveal that SATB1 induced translocation of β-catenin and formed a protein complex with it in the nuclei. In conclusion, SATB1 mediated tumor colonization and β-catenin nuclear localization are associated with the malignant progression and poor prognosis of CRC.

Simultaneous Expression of CD70 and POSTN in Cancer-Associated Fibroblasts Predicts Worse Survival of Colorectal Cancer Patients.

Colorectal cancer (CRC) is one of the most common gastrointestinal cancers worldwide, with high morbidity and mortality rates. The evidence for the tumor-supporting capacities of cancer-associated fibroblasts (CAFs) that modulate cancer cell proliferation, invasion, metastasis, and tumor immunity, including in CRC, has been attracting attention. The present study examined the expression status of CD70 and POSTN in CRC and analyzed their association with clinicopathological features and clinical outcomes. In the present study, in total 15% (40/269) and 44% (119/269) of cases exhibited CD70 and POSTN expression on CAFs, respectively. Co-expression of CD70 and POSTN was detected in 8% (21/269) of patients. Fluorescent immunohistochemistry identified the co-expression of CD70 and POSTN with FAP and PDPN, respectively. ACTA2 was not co-expressed with CD70 or POSTN in CRC CAFs. CRC with CD70+/POSTN+ status in CAFs was significantly associated with distant organ metastasis (p = 0.0020) or incomplete resection status (p = 0.0011). CD70+/POSTN+ status tended to associate with advanced pT stage (p = 0.032) or peritoneal metastasis (p = 0.0059). Multivariate Cox hazards regression analysis identified CD70+/POSTN+ status in CAFs [hazard ratio (HR) = 3.78] as a potential independent risk factor. In vitro experiments revealed the activated phenotypes of colonic fibroblasts induced by CD70 and POSTN, while migration and invasion assays identified enhanced migration and invasion of CRC cells co-cultured with CD70- and POSTN-expressing colonic fibroblasts. On the basis of our observations, CD70 and POSTN immunohistochemistry can be used in the prognostication of CRC patients. CRC CAFs may be a promising target in the treatment of CRC patients.

Magnesium hydride attenuates intestinal barrier injury during hemorrhage shock by regulating neutrophil extracellular trap formation via the ROS/MAPK/PAD4 pathway

Magnesium hydride (MgH2) is a hydrogen storage material that is known for its high capacity and safety and is capable of releasing hydrogen in a controlled manner when administered orally. This release of hydrogen has been associated with a range of biological effects, including anti-inflammatory properties, antioxidant activity, and protection of the intestinal barrier. Previous research has shown that neutrophil extracellular traps (NETs) play a role in the dysfunction of the intestinal barrier in conditions such as sepsis and critical illnesses. However, it remains unclear as to whether MgH2 can protect the intestinal barrier by inhibiting NET formation, and the underlying mechanisms have yet to be elucidated. A rat model of hemorrhagic shock was created, and pretreatment or posttreatment procedures with MgH2 were performed. After 24 h, samples from the small intestine and blood were collected for analysis. In vitro, human neutrophils were incubated with either phorbol-12-myristate-13-acetate (PMA) or MgH2. Reactive oxygen species generation and the expression of key proteins were assessed. The results demonstrated that MgH2 administration led to a decrease in inflammatory cytokines in the serum and mitigated distant organ dysfunction in rats with HS. Furthermore, MgH2 treatment reversed histopathological damage in the intestines, improved intestinal permeability, and enhanced the expression of tight junction proteins (TJPs) during HS. Additionally, MgH2 treatment was found to suppress NET formation in the intestines. In vitro pretreatment with MgH2 alleviated intestinal monolayer barrier disruption that was induced by NETs. Mechanistically, MgH2 pretreatment reduced ROS production and NET formation, inhibited the activation of ERK and p38, and suppressed the expression of the PAD4 protein. These findings indicated that MgH2 may inhibit NET formation in a ROS/MAPK/PAD4-dependent manner, which reduces NET-related intestinal barrier damage, thus offering a novel protective role in preventing intestinal barrier dysfunction during HS.

Functional annotation with expression validation identifies novel metastasis-relevant genes from post-GWAS risk loci in sporadic colorectal carcinomas

BackgroundColorectal cancer (CRC) is the third highest incidence cancer and is the leading cause of cancer mortality worldwide. Metastasis to distal organ is the major cause of cancer mortality. However,...

The Long-Distance Transport of Some Plant Hormones and Possible Involvement of Lipid-Binding and Transfer Proteins in Hormonal Transport.

Adaptation to changes in the environment depends, in part, on signaling between plant organs to integrate adaptive response at the level of the whole organism. Changes in the delivery of hormones from one organ to another through the vascular system strongly suggest that hormone transport is involved in the transmission of signals over long distances. However, there is evidence that, alternatively, systemic responses may be brought about by other kinds of signals (e.g., hydraulic or electrical) capable of inducing changes in hormone metabolism in distant organs. Long-distance transport of hormones is therefore a matter of debate. This review summarizes arguments for and against the involvement of the long-distance transport of cytokinins in signaling mineral nutrient availability from roots to the shoot. It also assesses the evidence for the role of abscisic acid (ABA) and jasmonates in long-distance signaling of water deficiency and the possibility that Lipid-Binding and Transfer Proteins (LBTPs) facilitate the long-distance transport of hormones. It is assumed that proteins of this type raise the solubility of hydrophobic substances such as ABA and jasmonates in hydrophilic spaces, thereby enabling their movement in solution throughout the plant. This review collates evidence that LBTPs bind to cytokinins, ABA, and jasmonates and that cytokinins, ABA, and LBTPs are present in xylem and phloem sap and co-localize at sites of loading into vascular tissues and at sites of unloading from the phloem. The available evidence indicates a functional interaction between LBTPs and these hormones.

Attenuation of intestinal ischemia-reperfusion-injury by anesthetics: a potentially protective effect of anesthetic management in experimental studies.

Intestinal ischemia-reperfusion injury (IRI) is a potentially severe clinical syndrome after major surgical procedures. In addition to causing intestinal mucosa injury, intestinal IRI further damages distant organs, causing the severity of the condition in patients. So far, effective therapy for intestinal IRI is still absent, and the survival rate of the patients is low. Previous experimental studies have shown that some anesthetics can alleviate intestinal IRI and protect organs while exerting their pharmacological effects, indicating that reasonable perioperative anesthesia management may provide potential benefits for patients to avoid intestinal IRI. These meaningful findings drive scholars to investigate the mechanism of anesthetics in treating intestinal IRI in-depth to discuss the possible new clinical uses. In the present mini-review, we will introduce the protective effects of different anesthetics in intestinal IRI to help us enrich our knowledge in this area.

Stroke and Distal Organ Damage: Exploring Brain-Kidney Crosstalk.

Stroke and kidney dysfunction represent significant public health challenges, yet the precise mechanisms connecting these conditions and their severe consequences remain unclear. Individuals experiencing chronic kidney disease (CKD) and acute kidney injury (AKI) are at heightened susceptibility to experiencing repeated strokes. Similarly, a reduced glomerular filtration rate is associated with an elevated risk of suffering a stroke. Prior strokes independently contribute to mortality, end-stage kidney disease, and cardiovascular complications, underscoring the pathological connection between the brain and the kidneys. In cases of AKI, various mechanisms, such as cytokine signaling, leukocyte infiltration, and oxidative stress, establish communication between the brain and the kidneys. The bidirectional relationship between stroke and kidney pathologies involves key factors such as uremic toxins, proteinuria, inflammatory responses, decreased glomerular filtration, impairment of the blood-brain barrier (BBB), oxidative stress, and metabolites produced by the gut microbiota. This review examines potential mechanisms of brain-kidney crosstalk underlying stroke and kidney diseases. It holds significance for comprehending multi-organ dysfunction associated with stroke and for formulating therapeutic strategies to address stroke-induced kidney dysfunction and the bidirectional pathological connection between the kidney and stroke.

Tropomyosin1 isoforms underlie epithelial to mesenchymal plasticity, metastatic dissemination, and resistance to chemotherapy in high-grade serous ovarian cancer

Phenotypic plasticity, defined as the ability of individual cells with stable genotypes to exert different phenotypes upon exposure to specific environmental cues, represent the quintessential hallmark of the cancer cell en route from the primary lesion to distant organ sites where metastatic colonization will occur. Phenotypic plasticity is driven by a broad spectrum of epigenetic mechanisms that allow for the reversibility of epithelial-to-mesenchymal and mesenchymal-to-epithelial transitions (EMT/MET). By taking advantage of the co-existence of epithelial and quasi-mesenchymal cells within immortalized cancer cell lines, we have analyzed the role of EMT-related gene isoforms in the regulation of epithelial mesenchymal plasticity (EMP) in high grade serous ovarian cancer. When compared with colon cancer, a distinct spectrum of downstream targets characterizes quasi-mesenchymal ovarian cancer cells, likely to reflect the different modalities of metastasis formation between these two types of malignancy, i.e. hematogenous in colon and transcoelomic in ovarian cancer. Moreover, upstream RNA-binding proteins differentially expressed between epithelial and quasi-mesenchymal subpopulations of ovarian cancer cells were identified that underlie differential regulation of EMT-related isoforms. In particular, the up- and down-regulation of RBM24 and ESRP1, respectively, represent a main regulator of EMT in ovarian cancer cells. To validate the functional and clinical relevance of our approach, we selected and functionally analyzed the Tropomyosin 1 gene (TPM1), encoding for a protein that specifies the functional characteristics of individual actin filaments in contractile cells, among the ovarian-specific downstream AS targets. The low-molecular weight Tpm1.8/9 isoforms are specifically expressed in patient-derived ascites and promote invasion through activation of EMT and Wnt signaling, together with a broad spectrum of inflammation-related pathways. Moreover, Tpm1.8/9 expression confers resistance to taxane- and platinum-based chemotherapy. Small molecule inhibitors that target the Tpm1 isoforms support targeting Tpm1.8/9 as therapeutic targets for the development of future tailor-made clinical interventions.

Gastric-type adenocarcinoma of the uterine cervix: clinical features and future directions.

The concept of gastric-type mucinous carcinoma of the uterine cervix (GAS) has been accepted worldwide because of its aggressive clinical behaviour and the absence of high-risk human papilloma virus infection. The World Health Organization (WHO) 2020 classification divides cervical tumours into two categories: human papilloma virus-associated and human papilloma virus-independent. Hence, GAS is now classified as an human papilloma virus-independent gastric type. Because clinical studies have reported that GAS is refractory to conventional treatments such as chemotherapy and radiotherapy, especially at an advanced stage, and has aggressive features with widespread dissemination to unusual sites, such as the omentum, peritoneum and distant organs, it is urgent to establish new treatment strategies by comparing the molecular profiles of human papilloma virus-associated adenocarcinomas. A series of genetic mutations characteristic to GAS encourage the development of future treatment strategies such as targeted therapy and immunotherapy.

Significance of RCC2, Rac1 and p53 Expression in Breast Infiltrating Ductal Carcinoma; An Immunohistochemical Study.

The regulator of chromosome condensation 2 (RCC2) and RAS-related C3 botulinum toxin substrate 1 (Rac1) have been implicated in the promotion of breast cancer cell proliferation and migration. The signaling pathway involving p53/RCC2/Rac1 has been proposed to contribute to the regulation of colon cancer metastasis. However, until now, this pathway has not been thoroughly investigated in breast cancer. This study seeks to explore the influence of immunohistochemical expression and the correlation among RCC2, Rac1, and p53 in breast infiltrating ductal carcinoma (IDC). Immunostaining was performed on 120 breast IDC specimens using RCC2, Rac1, and p53 antibodies. Statistical analyses were conducted to examine the correlations between these antibodies. A Positive expression of RCC2, Rac1, and p53 was observed in 116 (96.7%), 120 (100%), and 33 (27.5%) of the breast cancer cases, respectively. RCC2, Rac1, and p53 demonstrated association with poor prognostic parameters such as frequent mitoses, high Ki-67 status, positive lymphovascular invasion (LVI), and advanced tumor stage. A highly significant direct correlation was found between each immunohistochemical marker and the other two markers. Shorter overall survival was linked to multifocal tumors (P=0.017), advanced tumor stage (T3) (P=0.010), Luminal B subtype (P=0.015), progressive disease (P=0.003), positive Her2neu status (P=0.008), and metastasis to distant organs (P<0.001). However, RCC2, Rac1, and p53 did not exhibit a significant association with overall survival. The high expression levels of RCC2, Rac1, and p53 in breast IDC suggest their potential role in tumor behavior. The association of RCC2 and Rac1 with poor prognostic parameters may serve as predictive indicators for aggressive tumors, thus implying that targeted therapy could be beneficial in the treatment of breast cancer.

Biological factors driving colorectal cancer metastasis.

Approximately 20% of colorectal cancer (CRC) patients present with metastasis at diagnosis. Among Stage I-III CRC patients who undergo surgical resection, 18% typically suffer from distal metastasis within the first three years following initial treatment. The median survival duration after the diagnosis of metastatic CRC (mCRC) is only 9 mo. mCRC is traditionally considered to be an advanced stage malignancy or is thought to be caused by incomplete resection of tumor tissue, allowing cancer cells to spread from primary to distant organs; however, increasing evidence suggests that the mCRC process can begin early in tumor development. CRC patients present with high heterogeneity and diverse cancer phenotypes that are classified on the basis of molecular and morphological alterations. Different genomic and nongenomic events can induce subclone diversity, which leads to cancer and metastasis. Throughout the course of mCRC, metastatic cascades are associated with invasive cancer cell migration through the circulatory system, extravasation, distal seeding, dormancy, and reactivation, with each step requiring specific molecular functions. However, cancer cells presenting neoantigens can be recognized and eliminated by the immune system. In this review, we explain the biological factors that drive CRC metastasis, namely, genomic instability, epigenetic instability, the metastatic cascade, the cancer-immunity cycle, and external lifestyle factors. Despite remarkable progress in CRC research, the role of molecular classification in therapeutic intervention remains unclear. This review shows the driving factors of mCRC which may help in identifying potential candidate biomarkers that can improve the diagnosis and early detection of mCRC cases.

Gastrointestinal and brain barriers: unlocking gates of communication across the microbiota-gut-brain axis.

Crosstalk between gut and brain has long been appreciated in health and disease, and the gut microbiota is a key player in communication between these two distant organs. Yet, the mechanisms through which the microbiota influences development and function of the gut-brain axis remain largely unknown. Barriers present in the gut and brain are specialized cellular interfaces that maintain strict homeostasis of different compartments across this axis. These barriers include the gut epithelial barrier, the blood-brain barrier and the blood-cerebrospinal fluid barrier. Barriers are ideally positioned to receive and communicate gut microbial signals constituting a gateway for gut-microbiota-brain communication. In this Review, we focus on how modulation of these barriers by the gut microbiota can constitute an important channel of communication across the gut-brain axis. Moreover, barrier malfunction upon alterations in gut microbial composition could form the basis of various conditions, including often comorbid neurological and gastrointestinal disorders. Thus, we should focus on unravelling the molecular and cellular basis of this communication and move from simplistic framing as 'leaky gut'. A mechanistic understanding of gut microbiota modulation of barriers, especially during critical windows of development, could be key to understanding the aetiology of gastrointestinal and neurological disorders.

A63 RESTRAINED STRESS IN MICE INDUCES TRANSLOCATION OF GUT COMMENSAL BACTERIAL INTO DISTAL ORGANS

Abstract Background Bacterial translocation is defined as the migration of bacteria from the intestinal lumen into extraintestinal tissues; this process has been implicated in the pathophysiology of gastrointestinal disorders including irritable bowel syndrome (IBS) and central nervous system disorders. In our recent study, we found that gut bacteria from patients with IBS can disrupt the mucus layer and penetrate into the lamina propria in our microbiota-humanized mouse model. It is well known that psychological stress triggers or exacerbates IBS symptoms. Furthermore, experimental stress models have been able to reproduce some features of IBS and demonstrate that gut bacteria can translocate into the mesenteric lymph node (MLN), liver, and spleen. These studies suggested that bacterial translocation might induce changes in behavior and brain function. However, the direct causal relationship between bacterial translocation and behavioral changes, and the mechanism of bacterial translocation remains unclear. Aims To investigate translocation of commensal bacteria within the gut wall and their migration into distant organs using a mouse stress model. Methods SPF C57BL/6 mice were split into 2 groups: restraint stress group (3 hrs x 7 days, n=9) and non-stress control group (n=8). After the last session of stress, we conducted light/dark preference and tail suspension tests. We collected jejunum, ileum, and colon samples for histology. We also sampled blood, MLN, liver, spleen, and brain for histology and bacterial cultures. The tissues were collected under aseptic conditions. The blood or organ homogenates were plated and incubated in aerobic and anaerobic conditions. Intestinal tissues were submitted to fluorescence in situ hybridization staining with a bacterial universal probe in combination with immunofluorescence to co-stain with e-cadherin and CD103. The images were taken by confocal microscopy. Results The chronic restrain stress-induced anxiety-like, but not depressive behavior, as assessed by the light/dark test. Compared to the controls, bacterial culture was more frequently positive in the stress group: blood (0% vs 25%), MLN (0% vs 50%), spleen (0% vs 25%), liver (0% vs 25%), and brain (25% vs 74%). The histology showed that intestinal bacteria were present within the gut wall and brain in the stress group. Interestingly, these bacteria co-localized with the goblet cells in the jejunum, ileum and colon, and CD103+ dendritic cells in the colon (Fig. 1). Conclusions We found that mice subjected to the restraint stress exhibit abnormal behavior, accompanied by bacterial infiltration into the gut wall, as well as bacterial translocation into distal organs, including brain. Our histology data suggest a potential contribution of goblet cells-dendritic cells pathway in commensal gut bacteria translocation in the restrained stress model. Intestinal bacteria were present within the gut wall in the stress group. Funding Agencies CIHR Farncombe Innovation Fund