Postoperative ileus, which develops after each abdominal surgical procedure, is an iatrogenic disorder characterized by a transient inhibition of gastrointestinal motility. Its pathophysiology is ...complex involving pharmacological (opioids, anesthetics), neural, and immune-mediated mechanisms. The early neural phase, triggered by activation of afferent nerves during the surgical procedure, is short lasting compared to the later inflammatory phase. The latter starts after 3-6 h and lasts several days, making it a more interesting target for treatment. Insight into the triggers and immune cells involved is of great importance for the development of new therapeutic strategies. In this chapter, the pathogenesis and the current therapeutic approaches to treat postoperative ileus are discussed.
Background
Electrical stimulation of the cervical vagus nerve (VNS) prevents postoperative ileus (POI) in mice. As this approach requires an additional cervical procedure, we explored the possibility ...of peroperative abdominal VNS in mice and human.
Methods
The effect of cervical and abdominal VNS was studied in a murine model of POI and lipopolysaccharide (LPS)‐induced sepsis. Postoperative ileus was quantified by assessment of intestinal transit of fluorescent dextran expressed as geometric center (GC). Next, the effect of cervical and abdominal VNS on heart rate was determined in eight Landrace pigs to select the optimal electrode for VNS in human. Finally, the effect of sham or abdominal VNS on LPS‐induced cytokine production of whole blood was studied in patients undergoing colorectal surgery.
Key Results
Similar to cervical VNS, abdominal VNS significantly decreased LPS‐induced serum tumor necrosis factor‐α (TNFα) levels (abdominal VNS: 366±33 pg/mL vs sham: 822±105 pg/mL; P<.01). In line, in a murine model of POI, abdominal VNS significantly improved intestinal transit (GC: sham 5.1±0.2 vs abdominal VNS: 7.8±0.6; P<.01) and reduced intestinal inflammation (abdominal VNS: 35±7 vs sham: 80±8 myeloperoxidase positive cells/field; P<.05). In pigs, heart rate was reduced by cervical VNS but not by abdominal VNS. In humans, abdominal VNS significantly reduced LPS‐induced IL8 and IL6 production by whole blood.
Conclusions & Inferences
Abdominal VNS is feasible and safe in humans and has anti‐inflammatory properties. As abdominal VNS improves POI similar to cervical VNS in mice, our data indicate that peroperative abdominal VNS may represent a novel approach to shorten POI in man.
Vagus nerve stimulation (VNS) has anti‐inflammatory effects in immune‐mediated disorders such as sepsis and postoperative ileus. Traditionally, VNS has always been performed at cervical level. In this article, we evaluated the anti‐inflammatory properties of abdominal VNS in sepsis and postoperative ileus, thus avoiding additional incisions in the neck.
Post-infectious irritable bowel syndrome (PI-IBS) is a common gastrointestinal disorder characterized by persistent abdominal pain despite recovery from acute gastroenteritis. The underlying ...mechanisms are unclear, although long-term changes in neuronal function, and low grade inflammation of the bowel have been hypothesized. We investigated the presence and mechanism of neuronal sensitization in a unique cohort of individuals who developed PI-IBS following exposure to contaminated drinking water 7 years ago. We provide direct evidence of ongoing sensitization of neuronal signaling in the bowel of patients with PI-IBS. These changes occur in the absence of any detectable tissue inflammation, and instead appear to be driven by pro-nociceptive changes in the gut micro-environment. This is evidenced by the activation of murine colonic afferents, and sensitization responses to capsaicin in dorsal root ganglia (DRGs) following application of supernatants generated from tissue biopsy of patients with PI-IBS. We demonstrate that neuronal signaling within the bowel of PI-IBS patients is sensitized 2 years after the initial infection has resolved. This sensitization appears to be mediated by a persistent pro-nociceptive change in the gut micro-environment, that has the capacity to stimulate visceral afferents and facilitate neuronal TRPV1 signaling.
Background
Postoperative ileus (POI) is characterized by a transient inhibition of gastrointestinal (GI) motility after abdominal surgery mediated by the inflammation of the muscularis externa (ME). ...The aim of this study was to identify alterations in the enteric nervous system that may contribute to the pathogenesis of POI.
Methods
Gastrointestinal transit, contractility of isolated smooth muscle strips and inflammatory parameters were evaluated at different time points (1.5 h to 10 days) after intestinal manipulation (IM) in mice. Immune‐labeling was used to visualize changes in myenteric neurons.
Key Results
Intestinal manipulation resulted in an immediate inhibition of GI transit recovering between 24 h and 5 days. In vitro contractility to K+ (60 mM) or carbachol (10−9 to 10−4 M) was biphasically suppressed over 24 h after IM (with transient recovery at 6 h). The first phase of impaired myogenic contractility was associated with increased expression of TNF‐α, IL‐6 and IL‐1α. After 24 h, we identified a significant reduction in electrical field stimulation‐evoked contractions and relaxations, lasting up to 10 days after IM. This was associated with a reduced expression of chat and nos1 genes.
Conclusions & Inferences
Intestinal manipulation induces two waves of smooth muscle inhibition, most likely mediated by inflammatory cytokines, lasting up to 3 days after IM. Further, we here identify a late third phase (>24 h) characterized by impaired cholinergic and nitrergic neurotransmission persisting after recovery of muscle contractility. These findings illustrate that POI results from inflammation‐mediated impaired smooth muscle contraction, but also involves a long‐lasting impact of IM on the enteric nervous system.
We aimed to identify alterations in the enteric nervous system that may contribute to the pathogenesis of postoperative ileus. Surgical manipulation of the intestine induced two phases of muscle dysfunction over 24 h and a late prolonged phase of impaired neurotransmission. Our data show that intestinal surgery affect both muscle cells and neurons and different inflammatory mechanisms underlie the different phases.
Purpose
Cervical vagus nerve stimulation (VNS) prevents manipulation-induced intestinal inflammation and improves intestinal transit in a mouse model of postoperative ileus (POI). Cervical VNS, ...however, is accompanied by cardiovascular and respiratory side effects. In view of potential clinical application, we therefore evaluated the safety and feasibility of abdominal VNS via laparoscopic approach in a porcine model.
Methods
Six pigs were used in a non-survival study for both cervical and abdominal VNS. Two cardiac pacing electrodes were positioned around the right cervical and posterior abdominal vagus nerve and connected to an external stimulator. VNS was performed using four different settings (5 and 20 Hz, 0.5 and 1 ms pulse width) during 2 min with ECG recording. Laparoscopic VNS was timed and videotaped, and technical difficulties were noted. A validated National Aeronautics and Space Administration Task Load Index (NASA-TLX) questionnaire was used to evaluate the task and workload.
Results
The procedure was completed in all pigs with 4-port laparoscopic technique. Cervical and abdominal VNS were performed after correct identification and isolation of the nerve, and positioning of the electrodes around the nerve. Median laparoscopic operating time was 16 min (range 8–33 min), and median NASA-TLX was 31 (range 11–74). No major complications were encountered. Reduction of heart rate was between 5.5 and 14 % for cervical VNS and undetectable for abdominal VNS.
Conclusion
In a porcine model, laparoscopic VNS is feasible and safe with cardiac pacing electrodes and may lead to a similar novel approach in humans in the near future.
Current methods for spatial transcriptomics are limited by low spatial resolution. Here we introduce a method that integrates spatial gene expression data with histological image data from the same ...tissue section to infer higher-resolution expression maps. Using a deep generative model, our method characterizes the transcriptome of micrometer-scale anatomical features and can predict spatial gene expression from histology images alone.
Background
The orexigenic peptide ghrelin has anti‐inflammatory properties in colitis, however, the mechanism of action and the immune cells targeted remain still to be elucidated. Here, we assessed ...the possible effect of ghrelin on T helper (Th) cells in a T cell transfer model of chronic colitis.
Methods
Disease was induced in the recombination activating gene 1 knockout mice (Rag1−/−) by adoptive transfer of naïve Th cells from ghrelin receptor knockout mice (GRLN‐R−/−) or littermate wild‐type (WT) mice. The course and severity of colitis was assessed by monitoring body weight, diarrhea score, histological analysis, gene expression, and flow cytometry analysis. The possible effects of ghrelin on Th cell proliferation, polarization, and apoptosis was examined in vitro.
Key Results
Our data showed that Rag1−/− mice injected with GRLN‐R−/− Th cells displayed increased severity of colitis compared to mice injected with WT Th cells. In addition, Rag1−/− mice injected with GRLN‐R−/− Th cells had significantly higher intestinal inflammation and increased accumulation of Th1 and Th17 cells in the colon. In vitro, ghrelin directly affected proliferation of Th cells and induced apoptosis whereas it did not influence Th cell polarization.
Conclusion & Inferences
Our observations suggest that ghrelin modulates Th effector cells in the gut controlling proliferation and inducing apoptosis. Our findings further support the use of ghrelin as a novel therapeutic option to treat intestinal inflammatory diseases.
The expression of the orexigenic hormone ghrelin and its receptor has been reported on various immune cells including T helper (Th) cells both in humans and rodents. Based on the above, and taking into account the large expression of ghrelin in the bowel mucosa, we hypothesized that this peptide may directly modulate intestinal Th cells during colonic inflammation. Hence, we used a well‐characterized model of Th cell‐induced chronic colitis that allowed us to study the influence of ghrelin receptor specifically on Th cells. In this study, we observed that the lack of ghrelin signaling in Th cells significantly worsens colitis with increased colonic inflammation. Our data revealed a specific immunomodulatory effect of ghrelin on Th cells, making the ghrelin receptor a suitable therapeutic candidate to treat chronic intestinal inflammatory diseases.
Spatially resolved transcriptomics has enabled precise genome-wide mRNA expression profiling within tissue sections. The performance of methods targeting the polyA tails of mRNA relies on the ...availability of specimens with high RNA quality. Moreover, the high cost of currently available spatial resolved transcriptomics assays requires a careful sample screening process to increase the chance of obtaining high-quality data. Indeed, the upfront analysis of RNA quality can show considerable variability due to sample handling, storage, and/or intrinsic factors. We present RNA-Rescue Spatial Transcriptomics (RRST), a workflow designed to improve mRNA recovery from fresh frozen specimens with moderate to low RNA quality. First, we provide a benchmark of RRST against the standard Visium spatial gene expression protocol on high RNA quality samples represented by mouse brain and prostate cancer samples. Then, we test the RRST protocol on tissue sections collected from five challenging tissue types, including human lung, colon, small intestine, pediatric brain tumor, and mouse bone/cartilage. In total, we analyze 52 tissue sections and demonstrate that RRST is a versatile, powerful, and reproducible protocol for fresh frozen specimens of different qualities and origins.
Up to 20% of people worldwide develop gastrointestinal symptoms following a meal
, leading to decreased quality of life, substantial morbidity and high medical costs. Although the interest of both ...the scientific and lay communities in this issue has increased markedly in recent years, with the worldwide introduction of gluten-free and other diets, the underlying mechanisms of food-induced abdominal complaints remain largely unknown. Here we show that a bacterial infection and bacterial toxins can trigger an immune response that leads to the production of dietary-antigen-specific IgE antibodies in mice, which are limited to the intestine. Following subsequent oral ingestion of the respective dietary antigen, an IgE- and mast-cell-dependent mechanism induced increased visceral pain. This aberrant pain signalling resulted from histamine receptor H
-mediated sensitization of visceral afferents. Moreover, injection of food antigens (gluten, wheat, soy and milk) into the rectosigmoid mucosa of patients with irritable bowel syndrome induced local oedema and mast cell activation. Our results identify and characterize a peripheral mechanism that underlies food-induced abdominal pain, thereby creating new possibilities for the treatment of irritable bowel syndrome and related abdominal pain disorders.
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