The mannose receptor (CD206) identifies a population of colonic macrophages in health and inflammatory bowel disease.

To understand the contribution of mononuclear phagocytes (MNP), which include monocyte-derived intestinal macrophages, to the pathogenesis of inflammatory bowel disease (IBD), it is necessary to identify functionally-different MNP populations. We aimed to characterise intestinal macrophage populations in patients with IBD. We developed 12-parameter flow cytometry protocols to identify and human intestinal MNPs. We used these protocols to purify and characterize colonic macrophages from colonic tissue from patients with Crohn's disease (CD), ulcerative colitis (UC), or non-inflamed controls, in a cross-sectional study. We identify macrophage populations (CD45+CD64+ HLA-DR+) and describe two distinct subsets, differentiated by their expression of the mannose receptor, CD206. CD206+ macrophages expressed markers consistent with a mature phenotype: high levels of CD68 and CD163, higher transcription of IL-10 and lower expression of TREM1. CD206- macrophages appear to be less mature, with features more similar to their monocytic precursors. We identified and purified macrophage populations from human colon. These appear to be derived from a monocytic precursor with high CCR2 and low CD206 expression. As these cells mature, they acquire expression of IL-10, CD206, CD63, and CD168. Targeting the newly recruited monocyte-derived cells may represent a fruitful avenue to ameliorate chronic inflammation in IBD.

Hiatus hernia in healthy volunteers is associated with intrasphincteric reflux and cardiac mucosal lengthening without traditional reflux.

BACKGROUND AND AIMS: Hiatus hernia (HH) is a key mediator of gastro-oesophageal reflux disease but little is known about its significance in the general population. We studied the structure and function of the gastro-oesophageal junction in healthy volunteers with and without HH. METHODS: We compared 15 volunteers with HH, detected by endoscopy or MRI scan, but without gastro-oesophageal reflux disease with 15 controls matched for age, gender and body weight. Jumbo biopsies were taken across the squamocolumnar junction (SCJ). High-resolution pH metry (12 sensors) and manometry (36 sensors) were performed upright and supine, before and after a meal. The SCJ was marked with an endoscopically placed clip and visualised fluoroscopically. RESULTS: Cardiac mucosa was longer in volunteers with HH (3.5 vs 2.5 mm, p=0.01). There was no excessive acid reflux 5 cm above the upper border of the lower oesophageal sphincter (LOS) in either group but those with HH had short segment reflux 11 mm above the pH transition point after the meal when supine (pH<4 for 5.5% vs 0.3% of time, p=0.01). The SCJ and pH transition point were proximally displaced within the gastro-oesophageal junction in those with HH versus controls (p<0.05). The pH transition point was proximal to the peak LOS pressure point in HH subjects but distal to it in controls after the meal (p<0.05). When supine, the postprandial pH transition point crossed the SCJ in those with HH (p=0.03). CONCLUSIONS: Healthy volunteers with HH have increased intrasphincteric reflux and lengthening of cardiac mucosa in the absence of traditional transsphincteric reflux.

The Role of the Acid Pocket in Gastroesophageal Reflux Disease.

Gastroesophageal reflux disease is one of the commonest chronic conditions in the western world and its prevalence is increasing worldwide. The discovery of the acid pocket explained the paradox of acid reflux occurring more frequently in the postprandial period despite intragastric acidity being low due to the buffering effect of the meal. The acid pocket was first described in 2001 when it was detected as an area of low pH immediately distal to the cardia using dual pH electrode pull-through studies 15 minutes after a meal. It was hypothesized that there was a local pocket of acid close to the gastroesophageal junction that escapes the buffering effect of the meal, and that this is the source of postprandial acidic reflux. The presence of the acid pocket has been confirmed in other studies using different techniques including high-resolution pHmetry, Bravo capsule, magnetic resonance imaging, and scintigraphy. This review aims to describe what we know about the acid pocket including its length, volume, fluid constituents, and its relationship to the lower esophageal sphincter and squamocolumnar junction. We will discuss the possible mechanisms that lead to the formation of the acid pocket and examine what differences exist in patients who suffer from acid reflux. Treatments for reflux disease that affect the acid pocket will also be discussed.

In healthy volunteers, immunohistochemistry supports squamous to columnar metaplasia as mechanism of expansion of cardia, aggravated by central obesity.

INTRODUCTION: Recently, we showed that the length of cardiac mucosa in healthy volunteers correlated with age and obesity. We have now examined the immunohistological characteristics of this expanded cardia to determine whether it may be due to columnar metaplasia of the distal oesophagus. METHODS: We used the squamocolumnar junction (SCJ), antral and body biopsies from the 52 Helicobacter pylori-negative healthy volunteers who had participated in our earlier physiological study and did not have hiatus hernia, transsphincteric acid reflux, Barrett's oesophagus or intestinal metaplasia (IM) at cardia. The densities of inflammatory cells and reactive atypia were scored at squamous, cardiac and oxyntocardiac mucosa of SCJ, antrum and body. Slides were stained for caudal type homeobox 2 (CDX-2), villin, trefoil factor family 3 (TFF-3) and liver-intestine (LI)-cadherin, mucin MUC1, Muc-2 and Muc-5ac. In addition, biopsies from 15 Barrett's patients with/without IM were stained and scored as comparison. Immunohistological characteristics were correlated with parameters of obesity and high-resolution pH metry recording. RESULTS: Cardiac mucosa had a similar intensity of inflammatory infiltrate to non-IM Barrett's and greater than any of the other upper GI mucosae. The immunostaining pattern of cardiac mucosa most closely resembled non-IM Barrett's showing only slightly weaker CDX-2 immunostaining. In distal oesophageal squamous mucosa, expression of markers of columnar differentiation (TFF-3 and LI-cadherin) was apparent and these correlated with central obesity (correlation coefficient (CC)=0.604, p=0.001 and CC=0.462, p=0.002, respectively). In addition, expression of TFF-3 in distal oesophageal squamous mucosa correlated with proximal extension of gastric acidity within the region of the lower oesophageal sphincter (CC=-0.538, p=0.001). CONCLUSIONS: These findings are consistent with expansion of cardia in healthy volunteers occurring by squamo columnar metaplasia of distal oesophagus and aggravated by central obesity. This metaplastic origin of expanded cardia may be relevant to the substantial proportion of cardia adenocarcinomas unattributable to H. pylori or transsphincteric acid reflux.

Waist belt and central obesity cause partial hiatus hernia and short-segment acid reflux in asymptomatic volunteers.

OBJECTIVE: There is a high incidence of inflammation and metaplasia at the gastro-oesophageal junction (GOJ) in asymptomatic volunteers. Additionally, the majority of patients with GOJ adenocarcinomas have no history of reflux symptoms. We report the effects of waist belt and increased waist circumference (WC) on the physiology of the GOJ in asymptomatic volunteers. DESIGN: 12 subjects with normal and 12 with increased WC, matched for age and gender were examined fasted and following a meal and with waist belts on and off. A magnet was clipped to the squamo-columnar junction (SCJ). Combined assembly of magnet-locator probe, 12-channel pH catheter and 36-channel manometer was passed. RESULTS: The waist belt and increased WC were each associated with proximal displacement of SCJ within the diaphragmatic hiatus (relative to upper border of lower oesophageal sphincter (LOS), peak LOS pressure point and pressure inversion point, and PIP (all p<0.05). The magnitude of proximal migration of SCJ during transient LOS relaxations was reduced by 1.6-2.6 cm with belt on versus off (p=0.01) and in obese versus non-obese (p=0.04), consistent with its resting position being already proximally displaced. The waist belt, but not increased WC, was associated with increased LOS pressure (vs intragastric pressure) and movement of pH transition point closer to SCJ. At 5 cm above upper border LOS, the mean % time pH <4 was <4% in all studied groups. Acid exposure 0.5-1.5 cm above SCJ was increased, with versus without, belt (p=0.02) and was most marked in obese subjects with belt. CONCLUSIONS: Our findings indicate that in asymptomatic volunteers, waist belt and central obesity cause partial hiatus herniation and short-segment acid reflux. This provides a plausible explanation for the high incidence of inflammation and metaplasia and occurrence of neoplasia at the GOJ in subjects without a history of reflux symptoms.

Central obesity in asymptomatic volunteers is associated with increased intrasphincteric acid reflux and lengthening of the cardiac mucosa.

BACKGROUND & AIMS: In the West, a substantial proportion of subjects with adenocarcinoma of the gastric cardia and gastroesophageal junction have no history of reflux. We studied the gastroesophageal junction in asymptomatic volunteers with normal and large waist circumferences (WCs) to determine if central obesity is associated with abnormalities that might predispose individuals to adenocarcinoma. METHODS: We performed a study of 24 healthy, Helicobacter pylori-negative volunteers with a small WC and 27 with a large WC. Abdominal fat was quantified by magnetic resonance imaging. Jumbo biopsy specimens were taken across the squamocolumnar junction (SCJ). High-resolution pH-metry (12 sensors) and manometry (36 sensors) were performed in upright and supine subjects before and after a meal; the SCJ was visualized fluoroscopically. RESULTS: The cardiac mucosa was significantly longer in the large WC group (2.5 vs 1.75 mm; P = .008); its length correlated with intra-abdominal (R = 0.35; P = .045) and total abdominal (R = 0.37; P = .034) fat. The SCJ was closer to the upper border of the lower esophageal sphincter (LES) in subjects with a large WC (2.77 vs 3.54 cm; P = .02). There was no evidence of excessive reflux 5 cm above the LES in either group. Gastric acidity extended more proximally within the LES in the large WC group, compared with the upper border (2.65 vs 4.1 cm; P = .027) and peak LES pressure (0.1 cm proximal vs 2.1 cm distal; P = .007). The large WC group had shortening of the LES, attributable to loss of the distal component (total LES length, 3 vs 4.5 cm; P = .043). CONCLUSIONS: Central obesity is associated with intrasphincteric extension of gastric acid and cardiac mucosal lengthening. The latter might arise through metaplasia of the most distal esophageal squamous epithelium and this process might predispose individuals to adenocarcinoma.

Measuring movement and location of the gastroesophageal junction: research and clinical implications.

Understanding the physiology of gastroesophageal junction (GEJ) is important as failure of its function is associated with reflux disease, hiatus hernia, and cancer. In recent years, there have been impressive developments in high resolution technologies allowing measurement of luminal pressure, pH, and impedance. One obvious deficiency is the lack of technique to monitor the movement and location of the GEJ over a prolonged period of time. Proximal movement of the GEJ during peristalsis and transient lower esophageal sphincter relaxations (TLESRs) is due to shortening of the longitudinal muscle of the esophagus. Techniques for measuring shortening include fluoroscopic imaging of mucosal clip, high-frequency intraluminal ultrasound, and high resolution manometry, but these techniques have limitations. Short segment reflux is recently found to be more common than traditional reflux and may account for the high prevalence of intestinal metaplasia and cancer seen at GEJ. While high resolution pHmetry is available, there is no technique that can reliably and continuously measure the position of the squamocolumnar junction. A new technique is recently reported allowing a precise and continuous measurement of the GEJ based on the principle of Hall effect. Reported studies have validated its accuracy both on the bench and against the gold standard, fluoroscopy. It has been used alongside high resolution manometry in studying the behavior of the GEJ during TLESRs and swallows. While there are challenges associated with this new technique, there are promising ongoing developments. There is exciting time ahead in research and clinical applications for this new technique.

Effect of nitrite delivered in saliva on postprandial gastro-esophageal function.

OBJECTIVE: Acid reflux produces troublesome symptoms (heartburn) and complications including esophagitis, Barrett's esophagus, and adenocarcinoma. Reflux occurs due to excessive and inappropriate relaxation of the lower esophageal sphincter. An important mediator of this is nitric oxide, high concentrations of which are generated within the lumen when swallowed saliva meets gastric acid. Saliva contains nitrite, derived from the enterosalivary recirculation of dietary nitrate, which is reduced to nitric oxide by gastric acid. The aim of this study was to investigate whether salivary nitrite contributes to dysfunction of the lower esophageal sphincter. MATERIALS AND METHODS: In 20 volunteers, studies of gastro-esophageal function were performed on four separate days, following consumption of a standardized meal, with saliva nitrite concentrations modified differently each day by intra-oral nitrite infusion. RESULTS: The infusions produced an appropriate range in saliva nitrite concentrations, from below to well above the physiological range. The standardized meal induced expected physiological changes in gastro-esophageal function confirming the recordings were sensitive and robust. Esophageal acid exposure (primary outcome) was similar on each study day. Secondary outcomes, including number and duration of reflux events, rate of transient lower esophageal sphincter relaxations, lower esophageal sphincter pressure and rate of gastric emptying were also unaffected by variations in saliva nitrite concentration. CONCLUSIONS: Nitrite in swallowed saliva does not modify gastro-esophageal junction function or predispose to gastro-esophageal reflux. The wide range in saliva nitrite concentrations, the sensitivity of the physiological recordings and the number of subjects studied make it very unlikely that an effect has been missed.

Development and validation of a probe allowing accurate and continuous monitoring of location of squamo-columnar junction.

INTRODUCTION: Most pathology of the upper gastrointestinal tract now occurs close to the gastro-oesophageal squamo-columnar junction (SCJ). Studying the pathophysiology of this region even using high resolution pH, impedance and manometry is unreliable due to constant movement with respiration, swallowing and transient lower oesophageal sphincter relaxations. AIMS AND METHODS: A technique is reported allowing continuous real-time monitoring of the position of the SCJ. It involves endoscopically clipping a magnet (2 mm × 1 mm) to the SCJ and monitoring its position relative to a probe in the oesophago-gastric lumen. The latter has 26 Hall-Effect sensors mounted at 5mm spacing on a circuit board within a silicone tube. RESULTS: Bench studies: The recorded position of the magnet along the length of the probe was compared with its actual position. Accuracy was related to the distance between magnet and probe, orientation of the magnet relative to the probe and whether the magnet was anterior, posterior or lateral to the probe. Including all possible orientations of the magnet at or nearer than 10mm from the probe, the median accuracy along the length of probe was 2.4 mm (IQR 2.1 mm). The proportion of all possible orientations within 10mm of the probe giving an accuracy of ±10 mm was 88.9%. In vivo studies: With simultaneous fluoroscopy, eight healthy subjects were asked to perform normal breathing, deep breathing, water swallows and finally advancement and retraction of probe over a 12 cm segment. The position recorded by fluoroscopy and probe at each second interval were compared. The correlation co-efficient for all 224 position readings was 0.96 (95% CI: 0.89-0.96). No significant interference was observed when the probe was tested alongside high resolution pH and manometry. CONCLUSION: Used in conjunction with high resolution pH, impedance and manometry, this technique will allow for the first time detailed studies at the squamo-columnar junction.

Mechanism of association between BMI and dysfunction of the gastro-oesophageal barrier in patients with normal endoscopy.

INTRODUCTION: The association between body mass index (BMI) and gastro-oesophageal pressure gradient (GOPG) is incompletely understood. We examined the association between BMI and gastro-oesophageal (GO) barrier function and the effect of mechanically increasing intra-abdominal pressure on GO physiology. METHODS: (A) 103 dyspeptic patients with normal endoscopy underwent 24 h pH-metry and upper gastrointestinal manometry. Relationships between BMI and acid reflux, intragastric pressure (IGP), GOPG and lower oesophageal sphincter (LOS) pressure were calculated using bivariate correlations. (B) In 18 healthy volunteers, the effects of increasing IGP by abdominal belt on GO manometry were studied. RESULTS: (A) There was a linear correlation between BMI and oesophageal acid exposure in erect (R=0.35, p<0.001) and supine (R=0.40, p<0.001) positions. BMI was strongly associated with IGP (inspiration: R=0.66, p<0.001; expiration: R=0.78, p<0.001) and inspiratory GOPG (R=0.50, p<0.001). There were a positive correlation between BMI and inspiratory LOS pressure relative to atmospheric pressure (R=0.29, p=0.016) and a negative correlation with LOS pressure relative to IGP on expiration (R=-0.25, p=0.018). Logistic regression models using all significant manometric variables and relevant interactions revealed marked decline in the magnitude and significance of relationship between BMI and oesophageal acid exposure in supine (from OR 1.12 (95% CI 1.03 to 1.22), p=0.009, to 1.00 (0.86 to 1.17), p=0.999) and upright positions (from 1.11 (1.02 to 1.20), p=0.020, to 1.03 (0.89 to 1.18), p=0.717). (B) Application of the constricting abdominal belt produced similar manometric changes to those associated with increased BMI. However, the belt did not reproduce the reduced LOS pressure relative to IGP. CONCLUSION: The association between reflux and BMI may be largely explained by effects of increased intra-abdominal pressure. However, the reduced LOS pressure associated with BMI may be mediated by another mechanism or effects of chronic rather than acute elevation of intra-abdominal pressure.

Towards minimally invasive monitoring for gastroenterology - An external Squamocolumnar Junction Locator.

Transient lower oesophageal sphincter relaxations (TLOSRs) occur frequently and are the main mechanism of acid reflux. The only means of currently detecting TLOSRs is intra-luminal manometry and the probes themselves may stimulate TLOSRs. The squamo-columnar junction moves 4-5 centimeters proximally during TLOSRs and this provides a means of detecting such episodes. The objective of this work is to develop a sensor system capable of detecting the movement of a miniature magnet attached to the squamo-columnar junction from outside the body and thus allow detection of TLOSRs without the artifact associated with intraluminal detection probes. A GaAs Hall effect sensor was selected and an alternating current supply was developed with a combination of filters and a Phase Sensitive Detector, to detect the magnet. The oscillation frequency of the current was chosen in order to reduce electronic noise, and filtering outside this frequency means the signal to noise ratio was greatly improved. The phase sensitive detector was employed to accurately convert the amplitude of the sensor's output to a DC signal. With the addition of paired Flux Concentrators increases the range up to 10.2 centimetres, an improvement of 580% over commercial Hall effect sensors. The AC circuit and flux concentrator device far exceeds the sensitivity of the current Hall effect sensors supplied in the market, by rejecting noise and providing accurate measurement over significantly larger distances. The development of this sensor has applications beyond this specific medical device.

Genetics of gastroesophageal cancer: paradigms, paradoxes, and prognostic utility.

Hereditary diffuse gastric cancer and tylosis are autosomal dominant cancer susceptibility syndromes. Accumulating evidence also suggests a genetic contribution to Barrett's esophagus and adenocarcinoma, traditionally considered acquired disorders. In this article we review the current knowledge on the genetic mechanisms underlying hereditary diffuse gastric cancer, tylosis, and Barrett's esophagus. Hereditary diffuse gastric cancer is a paradigm for hereditary cancer susceptibility syndromes with E-cadherin implicated as the dominant oncogene in up to one-third of cases. Tylosis in contrast remains the paradox as whilst the putative abnormality has been localized to the long arm of chromosome 17, sequencing of this region has failed to reveal a disease causing mutation. In the case of Barrett's esophagus and adenocarcinoma, although a validated specific disease-associated gene is yet to be identified, the increasing body of evidence of a possible genetic link is paving the way for subsequent prognostic studies such as AspECT (Aspirin Esomeprazole Chemoprevention Trial). For the clinician these advances in understanding are already having implications for practice in terms of improved screening and the stratification of management strategies. As the mechanisms continue to be defined, there is the real possibility that these mechanisms could be exploited or subverted in the design of new therapies. In the meantime, however, clinicians should undertake rigorous biopsy programs to ensure early invasive lesions are detected.