Mechanosensitive Piezo Channels in the Gastrointestinal Tract.

Sensation of mechanical forces is critical for normal function of the gastrointestinal (GI) tract and abnormalities in mechanosensation are linked to GI pathologies. In the GI tract there are several mechanosensitive cell types-epithelial enterochromaffin cells, intrinsic and extrinsic enteric neurons, smooth muscle cells and interstitial cells of Cajal. These cells use mechanosensitive ion channels that respond to mechanical forces by altering transmembrane ionic currents in a process called mechanoelectrical coupling. Several mechanosensitive ionic conductances have been identified in the mechanosensory GI cells, ranging from mechanosensitive voltage-gated sodium and calcium channels to the mechanogated ion channels, such as the two-pore domain potassium channels K2P (TREK-1) and nonselective cation channels from the transient receptor potential family. The recently discovered Piezo channels are increasingly recognized as significant contributors to cellular mechanosensitivity. Piezo1 and Piezo2 are nonselective cationic ion channels that are directly activated by mechanical forces and have well-defined biophysical and pharmacologic properties. The role of Piezo channels in the GI epithelium is currently under investigation and their role in the smooth muscle syncytium and enteric neurons is still not known. In this review, we outline the current state of knowledge on mechanosensitive ion channels in the GI tract, with a focus on the known and potential functions of the Piezo channels.

Effect of endogenous hydrogen sulfide on the transwall gradient of the mouse colon circular smooth muscle.

A transwall gradient in resting membrane potential (RMP) exists across the circular muscle layer in the mouse colon. This gradient is dependent on endogenous generation of CO. H2S is also generated in muscle layers of the mouse colon. The effect of endogenously generated H2S on the transwall gradient is not known. The aim was to investigate the role of endogenous H2S. Our results showed that the CSE inhibitor dl-propargylglycine (PAG, 500 µm) had no effect on the transwall gradient. However, in preparations pretreated with the nitric oxide synthase inhibitor N-nitro-l-arginine (l-NNA, 200 µm) and in nNOS-knockout (KO) mouse preparations, PAG shifted the transwall gradient in the depolarizing direction. In CSE-KO-nNOS-KO mice, the gradient was shifted in the depolarizing direction. Endogenous generation of NO was significantly higher in muscle preparations of CSE-KO mice compared to wild-type (WT) mice. The amplitude of NO-mediated slow inhibitory junction potentials (S-IJPs) evoked by electric field stimulation was significantly higher in CSE-KO mouse preparations compared to the amplitude of S-IJPs in wild-type mouse preparations. CSE was present in all submucosal ganglion neurons and in almost all myenteric ganglion neurons. Eleven per cent of CSE positive neurons in the submucosal plexus and 50% of CSE positive neurons in the myenteric plexus also contained nNOS. Our results suggest that endogenously generated H2S acts as a stealth hyperpolarizing factor on smooth muscle cells to maintain the CO-dependent transwall gradient and inhibits NO production from nNOS.

Achalasia secondary to neoplasia: a disease with a changing differential diagnosis.

Achalasia secondary to neoplasia is an uncommon entity, but recognition is paramount given the concern of missing a cancer diagnosis. Most case series of secondary achalasia occurred in prior decades raising the question of whether the underlying neoplastic causes have changed. All cases of achalasia secondary to neoplasia were reviewed at the Mayo Clinic from 2000 to the present. Cases were assessed for underlying cause of achalasia, whether achalasia was the primary presentation and demographic and clinical factors. Seventeen patients with achalasia secondary to neoplasia were identified. This was 1.5% of all patients with achalasia seen. The most common causes were adenocarcinoma of the esophagus, followed by breast and non-small cell lung cancer. No cases of gastric cancer were identified. Most patients had weight loss and rapid onset of symptoms but could not clearly be distinguished from primary achalasia. Nine patients presented with achalasia, whereas eight patients had known neoplasia. Five of these patients had a positive paraneoplastic panel suggestive of a paraneoplastic syndrome. Prognosis was generally poor except for patients with esophageal leiomyomatosis. This case series demonstrates a changing differential diagnosis for achalasia secondary to neoplasia with a higher number of patients presenting with a known primary and with a paraneoplastic syndrome. Awareness of secondary achalasia and its differentiation from primary causes is still essential.

The transwall gradient across the mouse colonic circular muscle layer is carbon monoxide dependent.

Gastric and small intestinal circular smooth muscle layers have a transwall resting membrane potential (RMP) gradient that is dependent on release of carbon monoxide (CO) from interstitial cells of Cajal (ICCs). Our aim was to determine whether a RMP gradient exists in the mouse colon and whether the gradient is CO dependent. Microelectrodes were used to record RMPs from muscle cells at different depths of the circular muscle layer from wild-type and heme oxygenase-2-knockout (HO-2-KO) mice. A transwall RMP gradient was present in wild-type mice. The CO scavenger oxyhemoglobin (20 µM) and the heme oxygenase inhibitor chromium mesoporphyrin IX (CrMP, 5 µM) abolished the transwall gradient. The gradient was absent in HO-2-KO mice. Tetrodotoxin (1 µM) caused a significant depolarization in circular smooth muscle cells throughout the circular muscle layer and abolished the transwall gradient. Removal of the submucosal neurons abolished the gradient. The majority of submucosal neurons contained HO-2 immunoreactivity (HO-2-IR), while ICCs did not. These data show for the first time that a transwall gradient exists across the circular smooth muscle layer of the mouse colon, that the gradient is due to CO, and that the source of CO is the submucosal neurons.

Audit of suspected chronic intestinal pseudo-obstruction in patients with gynecologic cancer.

PURPOSE: To describe chronic intestinal pseudo-obstruction (IPO) syndromes that occur after radiotherapy or chemotherapy (or both) for gynecologic cancer. METHODS: All 48 patients in the study population had a history of gynecologic cancer, treatment with radiotherapy or chemotherapy (or both), and suspected chronic IPO. The final diagnosis was based on clinical symptoms, radiographic imaging, motility studies, and surgical findings. Treatment was expectant for 27 patients and surgical for 21. RESULTS: In six of the 21 surgical patients, the final diagnosis was mechanical obstruction. In the other 15, it was IPO syndrome: six had an idiopathic dysfunction (ID) and nine had a thick fibrinous coating (FC) on the serosal surface. Intestines of these 15 patients had patent lumens but decreased motility. The ID and FC groups differed in mean age, chemotherapy administration, and mean time from radiotherapy to surgery. Symptoms improved in 67% of FC patients compared with 17% of ID patients. Among patients treated expectantly, symptoms improved in 50% of the ID patients and in 38% of the FC patients. Motility studies were useful for distinguishing ID from FC or mechanical obstruction. CONCLUSION: Clinical history and motility studies may assist in diagnosing IPO syndrome in gynecologic cancer patients treated with radiotherapy or chemotherapy (or both) and in identifying patients who might benefit from surgical intervention.

Expression of RAD21 immunoreactivity in myenteric neurons of the human and mouse small intestine.

BACKGROUND: RAD21 is a double-strand-break repair protein and component of the cohesin complex with key roles in cellular functions. A RAD21 loss-of-function mutation was found in cases of chronic intestinal pseudo-obstruction (CIPO) with associated enteric neuronal loss. Analysis of RAD21 expression in the enteric nervous system is lacking, thus we aimed to characterize RAD21 immunoreactivity (IR) in myenteric ganglia. METHODS: Double labeling immunofluorescence in mouse and human jejunum was used to determine colocalization of RAD21 with HuC/D, PGP9.5, neuronal nitric oxide synthase (nNOS), neuropeptide Y (NPY), choline acetyl transferase (ChAT), Kit, platelet-derived growth factor receptor-α (PDGFRα), and glial fibrillary acid protein (GFAP) IRs. RESULTS: A subset of PGP9.5- and HuC/D-IR neuronal cell bodies and nerve fibers in the myenteric plexus of human and mouse small intestine also displayed cytoplasmic RAD21-IR Cytoplasmic RAD21-IR was found in 43% of HuC/D-IR neurons in adult and neonatal mice but did not colocalize with nNOS. A subset of ChAT-positive neurons had cytoplasmic RAD21-IR Punctate RAD21-IR was restricted to the nucleus in most cell types consistent with labeling of the cohesin complex. Cytoplasmic RAD21-IR was not detected in interstitial cells of Cajal, fibroblast-like cells or glia. Subsets of neurons in primary culture exhibited cytoplasmic RAD21-IR Suppression of RAD21 expression by shRNA knockdown abolished RAD21-IR in cultured neurons. CONCLUSIONS: Our data showing cytoplasmic RAD21 expression in enteric neurons provide a basis toward understanding how mutations of this gene may contribute to altered neuronal function/survival thus leading to gut-motor abnormalities.

High temporal resolution gastric emptying breath tests in mice.

BACKGROUND: Gastric emptying is a complex physiological process regulating the division of a meal into smaller partitions for the small intestine. Disrupted gastric emptying contributes to digestive disease, yet current measures may not reflect different mechanisms by which the process can be altered. METHODS: We have developed high temporal resolution solid and liquid gastric emptying breath tests in mice using [13 C]-octanoic acid and off axis- integrated cavity output spectroscopy (OA-ICOS). Stretched gamma variate and 2-component stretched gamma variate models fit measured breath excretion data. KEY RESULTS: These assays detect acceleration and delay using pharmacological (7.5 mg/kg atropine) or physiological (nutrients, cold exposure stress, diabetes) manipulations and remain stable over time. High temporal resolution resolved complex excretion curves with 2 components, which was more prevalent in mice with delayed gastric emptying following streptozotocin-induced diabetes. There were differences in the gastric emptying of Balb/c vs C57Bl6 mice, with slower gastric emptying and a greater occurrence of two-phase gastric emptying curves in the latter strain. Gastric emptying of C57Bl6 could be accelerated by halving the meal size, but with no effect on the occurrence of two-phase gastric emptying curves. A greater proportion of two-phase gastric emptying was induced in Balb/c mice with the administration of PYY (8-80 nmol) 60 min following meal ingestion. CONCLUSIONS AND INFERENCES: Collectively, these results demonstrate the utility of high temporal resolution gastric emptying assays. Two-phase gastric emptying is more prevalent than previously reported, likely involves intestinal feedback, but contributes little to the overall rate of gastric emptying.

Curriculum for neurogastroenterology and motility training: A report from the joint ANMS-ESNM task force.

Although neurogastroenterology and motility (NGM) disorders are some of the most frequent disorders encountered by practicing gastroenterologists, a structured competency-based training curriculum developed by NGM experts is lacking. The American Neurogastroenterology and Motility Society (ANMS) and the European Society of Neurogastroenterology and Motility (ESNM) jointly evaluated the components of NGM training in North America and Europe. Eleven training domains were identified within NGM, consisting of functional gastrointestinal disorders, visceral hypersensitivity and pain pathways, motor disorders within anatomic areas (esophagus, stomach, small bowel and colon, anorectum), mucosal disorders (gastro-esophageal reflux disease, other mucosal disorders), consequences of systemic disease, consequences of therapy (surgery, endoscopic intervention, medications, other therapy), and transition of pediatric patients into adult practice. A 3-tiered training curriculum covering these domains is proposed here and endorsed by all NGM societies. Tier 1 NGM knowledge and training is expected of all gastroenterology trainees and practicing gastroenterologists. Tier 2 knowledge and training is appropriate for trainees who anticipate NGM disorder management and NGM function test interpretation being an important part of their careers, which may require competency assessment and credentialing of test interpretation skills. Tier 3 knowledge and training is undertaken by trainees interested in a dedicated NGM career and may be restricted to specific domains within the broad NGM field. The joint ANMS and ESNM task force anticipates that the NGM curriculum will streamline NGM training in North America and Europe and will lead to better identification of centers of excellence where Tier 2 and Tier 3 training can be accomplished.

Relating gastric scintigraphy and symptoms to motility capsule transit and pressure findings in suspected gastroparesis.

BACKGROUND: Wireless motility capsule (WMC) findings are incompletely defined in suspected gastroparesis. We aimed to characterize regional WMC transit and contractility in relation to scintigraphy, etiology, and symptoms in patients undergoing gastric emptying testing. METHODS: A total of 209 patients with gastroparesis symptoms at NIDDK Gastroparesis Consortium centers underwent gastric scintigraphy and WMCs on separate days to measure regional transit and contractility. Validated questionnaires quantified symptoms. KEY RESULTS: Solid scintigraphy and liquid scintigraphy were delayed in 68.8% and 34.8% of patients; WMC gastric emptying times (GET) were delayed in 40.3% and showed 52.8% agreement with scintigraphy; 15.5% and 33.5% had delayed small bowel (SBTT) and colon transit (CTT) times. Transit was delayed in ≥2 regions in 23.3%. Rapid transit was rarely observed. Diabetics had slower GET but more rapid SBTT versus idiopathics (P ≤ .02). GET delays related to greater scintigraphic retention, slower SBTT, and fewer gastric contractions (P ≤ .04). Overall gastroparesis symptoms and nausea/vomiting, early satiety/fullness, bloating/distention, and upper abdominal pain subscores showed no relation to WMC transit. Upper and lower abdominal pain scores (P ≤ .03) were greater with increased colon contractions. Constipation correlated with slower CTT and higher colon contractions (P = .03). Diarrhea scores were higher with delayed SBTT and CTT (P ≤ .04). CONCLUSIONS & INFERENCES: Wireless motility capsules define gastric emptying delays similar but not identical to scintigraphy that are more severe in diabetics and relate to reduced gastric contractility. Extragastric transit delays occur in >40% with suspected gastroparesis. Gastroparesis symptoms show little association with WMC profiles, although lower symptoms relate to small bowel or colon abnormalities.

5-HT receptors on interstitial cells of Cajal, smooth muscle and enteric nerves.

The majority of the body's serotonin (5-HT) is produced by the gastrointestinal tract. 5-HT has several functions in the gastrointestinal tract. 5-HT is a paracrine signalling molecule released from enterochromaffin cells, a survival and proliferating factor and a neurotransmitter. The actions of 5-HT are transduced by a large family of 5-HT receptors, several of which are expressed on different gastrointestinal cell types including enteric nerves, smooth muscle and interstitial cells of Cajal (ICC). This review will summarize recent advances in understanding the role of 5-HT in regulating function of ICC, and the expression and function of 5-HT receptors on muscle and enteric nerves in human tissue. Rodent ICC express several 5-HT receptors including 5-HT(2B) receptors which regulate ICC survival and proliferation. Human smooth muscle and enteric neurons also express several 5-HT receptor subtypes. Expression and function of these receptors is significantly different from small laboratory animals. 5-HT(7) receptor activation causes relaxation of muscle, whereas 5-HT(2B) receptors increase muscle activity. The 5-HT(4) receptor appears to mediate both inhibition and activation of smooth muscle involving myogenic as well as neural actions. Despite the abundant expression of 5-HT(3) receptors in the human enteric nervous system no functional correlate has been as yet demonstrated.

Mechanosensitive ion channels in interstitial cells of Cajal and smooth muscle of the gastrointestinal tract.

Normal gastrointestinal (GI) motility is required to mix digestive enzymes and food and to move content along the GI tract. Underlying the complex motor patterns of the gut are electrical events that reflect ion flux across cell membranes. Smooth muscle electrical activity is directly influenced by GI interstitial cells of Cajal, whose rhythmic oscillations in membrane potential in part determine the excitability of GI smooth muscle and its response to neuronal input. Coordinated activity of the ion channels responsible for the conductances that underlie ion flux in both smooth muscle and interstitial cells is a requisite for normal motility. These conductances are regulated by many factors, including mechanical stress. Recent studies have revealed mechanosensitivity at the level of the ion channels, and the mechanosensor within the channel has been identified in many cases. This has led to better comprehension of the role of mechanosensitive conductances in normal physiology and will undoubtedly lead to understanding of the consequences of disturbances in these conductances.

Regulation of interstitial cells of Cajal in the mouse gastric body by neuronal nitric oxide.

The factors underlying the survival and maintenance of interstitial cells of Cajal (ICC) are not well understood. Loss of ICC is often associated with loss of neuronal nitric oxide synthase (nNOS) in humans, suggesting a possible link. The aim of this study was to determine the effect of neuronal NO on ICC in the mouse gastric body. The volumes of ICC were determined in nNOS(-/-) and control mice in the gastric body and in organotypic cultures using immunohistochemistry, laser scanning confocal microscopy and three-dimensional reconstruction. ICC numbers were determined in primary cell cultures after treatment with an NO donor or an NOS inhibitor. The volumes of myenteric c-Kit-immunoreactive networks of ICC from nNOS(-/-) mice were significantly reduced compared with control mice. No significant differences in the volumes of c-Kit-positive ICC were observed in the longitudinal muscle layers. ICC volumes were either decreased or unaltered in the circular muscle layer after normalization for the volume of circular smooth muscle. The number of ICC was increased after incubation with S-nitroso-N-acetylpenicillamine and decreased by N(G)-nitro-l-arginine. Neuronally derived NO modulates ICC numbers and network volume in the mouse gastric body. NO appears to be a survival factor for ICC.

Species dependent expression of intestinal smooth muscle mechanosensitive sodium channels.

A mechanosensitive Na(+) current carried by Na(v)1.5 is present in human intestinal circular smooth muscle and contributes to regulation of intestinal motor function. Expression of this channel in different species is unknown. Our aim was to determine if Na(+) currents and message for the alpha subunit of the Na(+) channel (SCN5A) are found in circular smooth muscle cells of human, dog, pig, mouse and guinea pig jejunum. Currents were recorded using patch clamp techniques. Message for SCN5A was investigated using laser capture microdissection and reverse transcription polymerase chain reaction (RT-PCR). Na(+) currents were identified consistently in human and dog smooth muscle cells; however, Na(+) current was not found in pig (0/20) or guinea pig smooth muscle cells (0/21) and found only one mouse cell (1/21). SCN5A mRNA was found in circular muscle of human, dog, and mouse, but not in pig or guinea pig, and not in mouse longitudinal or mucosal layers. In summary, SCN5A message is expressed in, and Na(+) current recorded from, circular muscle layer of human and dog but not from pig and guinea pig. These data show that there are species differences in expression of the SCN5A-encoded Na(v)1.5 channel, suggesting species-specific differences in the electrophysiological response to mechanical and depolarizing stimuli.

Tumor necrosis factor alpha derived from classically activated "M1" macrophages reduces interstitial cell of Cajal numbers.

BACKGROUND: Delayed gastric emptying in diabetic mice and humans is associated with changes in macrophage phenotype and loss of interstitial cells of Cajal (ICC) in the gastric muscle layers. In diabetic mice, classically activated M1 macrophages are associated with delayed gastric emptying, whereas alternatively activated M2 macrophages are associated with normal gastric emptying. This study aimed to determine if secreted factors from M1 macrophages could injure mouse ICC in primary culture. METHODS: Cultures of gastric ICC were treated with conditioned medium (CM) from activated bone marrow-derived macrophages (BMDMs) and the effect of CM was quantified by counting ICC per high-powered field. KEY RESULTS: Bone marrow-derived macrophages were activated to a M1 or M2 phenotype confirmed by qRT-PCR. Conditioned medium from M1 macrophages reduced ICC numbers by 41.1%, whereas M2-CM had no effect as compared to unconditioned, control media. Immunoblot analysis of 40 chemokines/cytokines found 12 that were significantly increased in M1-CM, including tumor necrosis factor alpha (TNF-α). ELISA detected 0.697±0.03 ng mL-1 TNF-α in M1-CM. Recombinant mouse TNF-α reduced Kit expression and ICC numbers in a concentration-dependent manner (EC50 = 0.817 ng mL-1 ). Blocking M1-CM TNF-α with a neutralizing antibody preserved ICC numbers. The caspase inhibitor Z-VAD.fmk partly preserved ICC numbers (cells/field; 6.63±1.04, 9.82±1.80 w/Z-VAD.fmk, n=6, P<.05). CONCLUSIONS & INFERENCES: This work demonstrates that TNF-α secreted from M1 macrophages can result in Kit loss and directly injure ICC in vitro partly through caspase-dependent apoptosis and may play an important role in ICC depletion in diabetic gastroparesis.

High-resolution electrical mapping of porcine gastric slow-wave propagation from the mucosal surface.

BACKGROUND: Gastric motility is coordinated by bioelectrical slow waves, and gastric dysrhythmias are reported in motility disorders. High-resolution (HR) mapping has advanced the accurate assessment of gastric dysrhythmias, offering promise as a diagnostic technique. However, HR mapping has been restricted to invasive surgical serosal access. This study investigates the feasibility of HR mapping from the gastric mucosal surface. METHODS: Experiments were conducted in vivo in 14 weaner pigs. Reference serosal recordings were performed with flexible-printed-circuit (FPC) arrays (128-192 electrodes). Mucosal recordings were performed by two methods: (i) FPC array aligned directly opposite the serosal array, and (ii) cardiac mapping catheter modified for gastric mucosal recordings. Slow-wave propagation and morphology characteristics were quantified and compared between simultaneous serosal and mucosal recordings. KEY RESULTS: Slow-wave activity was consistently recorded from the mucosal surface from both electrode arrays. Mucosally recorded slow-wave propagation was consistent with reference serosal activation pattern, frequency (P≥.3), and velocity (P≥.4). However, mucosally recorded slow-wave morphology exhibited reduced amplitude (65-72% reduced, P<.001) and wider downstroke width (18-31% wider, P≤.02), compared to serosal data. Dysrhythmias were successfully mapped and classified from the mucosal surface, accorded with serosal data, and were consistent with known dysrhythmic mechanisms in the porcine model. CONCLUSIONS & INFERENCES: High-resolution gastric electrical mapping was achieved from the mucosal surface, and demonstrated consistent propagation characteristics with serosal data. However, mucosal signal morphology was attenuated, demonstrating necessity for optimized electrode designs and analytical algorithms. This study demonstrates feasibility of endoscopic HR mapping, providing a foundation for advancement of minimally invasive spatiotemporal gastric mapping as a clinical and scientific tool.

Early satiety and postprandial fullness in gastroparesis correlate with gastroparesis severity, gastric emptying, and water load testing.

BACKGROUND: Early satiety (ES) and postprandial fullness (PPF) are often present in gastroparesis, but the importance of these symptoms in gastroparesis has not been well-described. The aims were: (i) Characterize ES and PPF in patients with gastroparesis. (ii) Assess relationships of ES and PPF with etiology of gastroparesis, quality of life, body weight, gastric emptying, and water load testing. METHODS: Gastroparetic patients filled out questionnaires assessing symptoms (PAGI-SYM) and quality of life (PAGI-QOL, SF-36v2). Patients underwent gastric emptying scintigraphy and water load testing. KEY RESULTS: 198 patients with gastroparesis (134 IG, 64 DG) were evaluated. Early satiety was severe or very severe in 50% of patients. Postprandial fullness was severe or very severe in 60% of patients. Severity scores for ES and PPF were similar between idiopathic and diabetic gastroparesis. Increasing severity of ES and PPF were associated with other gastroparesis symptoms including nausea/vomiting, satiety/early fullness, bloating, and upper abdominal pain and GERD subscores. Increasing severity of ES and PPF were associated with increasing gastroparesis severity, decreased BMI, decreased quality of life from PAGI-QOL and SF-36 physical health. Increasing severity of ES and PPF were associated with increasing gastric retention of a solid meal and decreased volume during water load test. CONCLUSIONS & INFERENCES: Early satiety and PPF are commonly severe symptoms in both diabetic and idiopathic gastroparesis. Early satiety and PPF severity are associated with other gastroparesis symptom severities, body weight, quality of life, gastric emptying, and water load testing. Thus, ES and PPF are important symptoms characterizing gastroparesis. ClinicalTrials.gov number: NCT NCT01696747.

Diabetic and idiopathic gastroparesis is associated with loss of CD206-positive macrophages in the gastric antrum.

BACKGROUND: Animal studies have increasingly highlighted the role of macrophages in the development of delayed gastric emptying. However, their role in the pathophysiology of human gastroparesis is unclear. Our aim was to determine changes in macrophages and other cell types in the gastric antrum muscularis propria of patients with diabetic and idiopathic gastroparesis. METHODS: Full thickness gastric antrum biopsies were obtained from patients enrolled in the Gastroparesis Clinical Research Consortium (11 diabetic, 6 idiopathic) and 5 controls. Immunolabeling and quantitative assessment was done for interstitial cells of Cajal (ICC) (Kit), enteric nerves protein gene product 9.5, neuronal nitric oxide synthase, vasoactive intestinal peptide, substance P, tyrosine hydroxylase), overall immune cells (CD45) and anti-inflammatory macrophages (CD206). Gastric emptying was assessed using nuclear medicine scintigraphy and symptom severity using the Gastroparesis Cardinal Symptom Index. RESULTS: Both diabetic and idiopathic gastroparesis patients showed loss of ICC as compared to controls (Mean [standard error of mean]/hpf: diabetic, 2.28 [0.16]; idiopathic, 2.53 [0.47]; controls, 6.05 [0.62]; P=.004). Overall immune cell population (CD45) was unchanged but there was a loss of anti-inflammatory macrophages (CD206) in circular muscle (diabetic, 3.87 [0.32]; idiopathic, 4.16 [0.52]; controls, 6.59 [1.09]; P=.04) and myenteric plexus (diabetic, 3.83 [0.27]; idiopathic, 3.59 [0.68]; controls, 7.46 [0.51]; P=.004). There was correlation between the number of ICC and CD206-positive cells (r=.55, P=.008). Enteric nerves (PGP9.5) were unchanged: diabetic, 33.64 (3.45); idiopathic, 41.26 (6.40); controls, 46.80 (6.04). CONCLUSION: Loss of antral CD206-positive anti-inflammatory macrophages is a key feature in human gastroparesis and it is associates with ICC loss.

Treatment of gastroparesis: a multidisciplinary clinical review.

This clinical review on the treatment of patients with gastroparesis is a consensus document developed by the American Motility Society Task Force on Gastroparesis. It is a multidisciplinary effort with input from gastroenterologists and other specialists who are involved in the care of patients with gastroparesis. To provide practical guidelines for treatment, this document covers results of published research studies in the literature and areas developed by consensus agreement where clinical research trials remain lacking in the field of gastroparesis.

Correlated gene expression encoding serotonin (5-HT) receptor 4 and 5-HT transporter in proximal colonic segments of mice across different colonization states and sexes.

The production and handling of serotonin (5-HT) is an important determinant of colonic motility and has been reported to be altered in gastrointestinal (GI) disorders such as irritable bowel syndrome (IBS). Recent studies suggest that the intestinal microbiota and sex of the host can influence expression of genes involved in 5-HT biosynthesis and signaling. While expression of genes in serotonergic pathways has been shown to be variable, it remains unclear whether genes within this pathway are coregulated. As a first step in that direction, we investigated potential correlations in relative mRNA expression of serotonergic genes, in the proximal colon isolated from male and female mice in different states of microbial association: germ-free (GF), humanized (ex-germ-free colonized with human gut microbiota, HM), and conventionally raised (CR) mice. Among the 10 pairwise comparisons conducted between five serotonergic transcripts, Tph1, Chga, Maoa, Slc6a4, and Htr4, we found a strong, positive correlation between colonic expression of Slc6a4 and Htr4 across different colonization states and sexes. We also identified a positive correlation between the expression of Tph1 and Chga; however, there were no correlations observed between any other tested pair of 5-HT-related transcripts. These data suggest that correlated expression of Slc6a4 and Htr4 likely involves coregulation of genes located on different chromosomes which modulate serotonergic activity in the gut. Further work will need to be done to understand the pathways and cell types responsible for this correlated expression, given the important role of 5-HT in gastrointestinal physiology.