Reflux injury of esophageal mucosa: experimental studies in animal models of esophagitis, Barrett's esophagus and esophageal adenocarcinoma

Using simple interrupted suture anastomoses may impair translatability of experimental rodent oesophageal surgery

Background/purpose: Irreproducibility and missing translatability are major drawbacks in experimental animal studies. Hand-sewn anastomoses in oesophageal surgery are usually continuous, whereas those in experimental oesophageal surgery are widely performed using the simple interrupted technique. It has been implicated to be inferior in tolerating anastomotic tension, which we aimed to test in rats due to their importance as an animal model in oesophageal surgery.Methods: We determined linear breaking strengths for the native oesophagus (n = 10), the simple interrupted suture anastomosis (n = 11), and the simple stitch (n = 9) in 8-week old Sprague-Dawley rats. Experiments were powered to a margin of error of 10% around the results of exploratory investigations. The comparison of anastomotic resilience between native organ and simple interrupted suture anastomosis was a priori powered to 99%.Results: Native oesophagi sustained traction forces of 4.25 N (95% CI: 4.03-4.58 N), but the simple interrupted suture anastomosis had only 38.6% (Δ= -2.78 N, 95% CI: -2.46 to -3.11 N, p < .0001) of the resilience of native oesophagi.Conclusions: Oesophageal division and re-anastomosis markedly decreases resilience to traction forces compared to the native organ. This effect is even more pronounced in rats compared to other species and might impair transferability of results.

Columnar epithelium morphology after esophagectomy: clinical insight into the development of Barrett's esophagus

BACKGROUND

The presence of Barrett's mucosa in the esophageal remnant is a result of post-esophagectomy anastomotic site exposure to gastric acid and is regarded as a human model of Barrett's esophagus onset. Here, we attempted to clarify the relationship between duodenogastric reflux and formation of columnar epithelium by following the changes over time after esophagectomy.

METHODS

A total of 96 patients underwent esophagectomy due to superficial cancer from April 2000 to March 2018 were included in this study. Cases were divided into two groups according to the reconstruction technique after esophagectomy as either the gastric pull-up (Ga) group and ileocolonic interposition (Ic) group. Previously obtained endoscopic pictures of the cases were reviewed retrospectively and chronologically.

RESULTS

There were 24 cases of columnar epithelium in the Ga group (42%) and 1 in the Ic group (2.6%) (P < 0.01) with 32 reflux cases (56%) in the Ga group and 1 (2.6%) in the Ic group (P < 0.01). Reflux precedes the development of columnar epithelium in both the Ga- and Ic groups. Multivariate analysis revealed surgical technique (odds ratio 10.6, 95% CI 1.2-97.5, P = 0.037) and reflux (odds ratio 4.5, 95% CI 1.3-15.6, P = 0.0017) as risk factors.

CONCLUSIONS

The development of columnar epithelium was preceded by reflux comprising principally gastric acid and was strongly associated with a strong inflammatory state.

Gastroesophageal reflux disease and atrial fibrillation: Insight from autonomic cardiogastric neural interaction

BACKGROUND

The relationship between gastroesophageal reflux disease (GERD) and atrial fibrillation (AF) has been previously reported. However, the detailed mechanism remains unknown. In this study, we investigated the effects of acid reflux on the intrinsic cardiac autonomic nervous system, atrial/ventricular electrophysiology, and AF inducibility.

METHODS

Eighteen rabbits were randomized into three groups: acid reflux (group 1, n = 6), control (group 2, n = 6), and acid reflux with periesophageal vagal blockade (group 3, n = 6). Atrial and ventricular effective refractory periods (ERPs) and AF inducibility were checked at baseline and then hourly until 5 hours after the experiment.

RESULTS

Three hours after the experiment, atrial ERP prolongation was noted in groups 2 and 3 (P < .05), whereas shortening of the atrial ERPs was observed in group 1, compared with the baseline. However, no changes were observed in ventricular ERPs in the three groups. The AF inducibility was higher in group 1 than in groups 2 and 3. Pathological examination showed clear esophageal mucosal breaks in groups 1 and 3.

CONCLUSIONS

In this study, we found that the antimuscarinic blockade prevents GERD induced changes to atrial electrophysiology and susceptibility to AF-making it highly likely that autonomic activity is important in mediating this effect.

Conjugated Bile Acids Promote Invasive Growth of Esophageal Adenocarcinoma Cells and Cancer Stem Cell Expansion via Sphingosine 1-Phosphate Receptor 2-Mediated Yes-Associated Protein Activation

Esophageal adenocarcinoma (EAC) is the sixth leading cause of cancer deaths worldwide and has been dramatically increasing in incidence over the past decade. Gastroesophageal reflux and Barrett esophagus are well-established risk factors for disease progression. Conjugated bile acids (CBAs), including taurocholate (TCA), represent the major bile acids in the gastroesophageal refluxate of advanced Barrett esophagus and EAC patients. Our previous studies suggested that CBA-induced activation of sphingosine 1-phosphate receptor 2 (S1PR2) plays a critical role in promoting cholangiocarcinoma cell invasive growth. However, the role of CBAs in EAC development and underlying mechanisms remains elusive. In the current study, we identified that the expression level of S1PR2 is correlated to invasiveness of EAC cells. TCA significantly promoted cell proliferation, migration, invasion, transformation, and cancer stem cell expansion in highly invasive EAC cells (OE-33 cells), but had less effect on the lower invasive EAC cells (OE-19 cells). Pharmacologic inhibition of S1PR2 with specific antagonist JTE-013 or knockdown of S1PR2 expression significantly reduced TCA-induced invasive growth of OE-33 cells, whereas overexpression of S1PR2 sensitized OE-19 cells to TCA-induced invasive growth. Furthermore, TCA-induced activation of S1PR2 was closely associated with YAP and β-catenin signaling pathways. In conclusion, CBA-induced activation of the S1PR2 signaling pathway is critically involved in invasive growth of EAC cells and represents a novel therapeutic target for EAC.

Serial Endoscopic Evaluation of Esophageal Disease in a Cancer Model: A Paradigm Shift for Esophageal Adenocarcinoma (EAC) Drug Discovery and Development

A rat model of surgically induced reflux recapitulates the development and progression of human esophageal adenocarcinoma (EAC). In this study, reflux was induced in rats followed by postoperative endoscopy with biopsy, to diagnose and monitor disease progression. Overall, percentage agreement between visual endoscopy and gold standard histology was 95%, with disease-specific classification accuracies of 100% and 75% for Barrett's with dysplasia and EAC, respectively. Additionally, the percentage agreement for biopsy in tumors >4 mm was 75%. Thereby, establishing endoscopic evaluation as a reliable tool to assess disease progression and provide biopsies for downstream correlates in a de novo EAC model.

Pathology, Chemoprevention, and Preclinical Models for Target Validation in Barrett Esophagus

Despite esophageal adenocarcinoma (EAC) being the most widespread among gastrointestinal cancers, with an 11-fold increase in the risk of cancer for patients with Barrett esophagus (BE), its prognosis is still poor. There is a critical need to better perceive the biology of cancer progression and identification of specific targets that are the hallmark of BE's progression. This review explores the established animal models of BE, including genetic, surgical and nonsurgical approaches, potential chemoprevention targets, and the reasoning behind their applications to prevent Barrett-related EAC. The key methodological features in the design feasibility of relevant studies are also discussed. Cancer Res; 78(14); 3747-54. ©2018 AACR.

Preclinical models for the study of Barrett's carcinogenesis

Barrett's esophagus (BE) is clinically significant, as it is the only known precursor lesion for esophageal adenocarcinoma. To develop improved therapies for the treatment of BE, a greater understanding of the disease process at the molecular genetic level is needed. However, achieving a greater understanding will require improved preclinical models so that the disease process can be more closely studied and novel therapies can be tested. Our concise review highlights progress in the development of preclinical models for the study of BE and identifies the most suitable model in which to test novel therapies.

The association between sleeve gastrectomy and histopathologic changes consistent with esophagitis in a rodent model

BACKGROUND

As the association between sleeve gastrectomy (SG) and gastroesophageal reflux disease remains unclear, the aim of this study was to evaluate whether performance of SG impacts the development and severity of esophagitis in a rodent model.

SETTING

University Hospital.

METHODS

Wistar rats (Charles River Institute, Wilmington, MA) were fed a high fat diet (HFD) for 4 months and then were divided into 3 cohorts of nearly equal mean weight: HFD only (n = 25), sham operation+HFD (n = 29), and SG+HFD (n = 19). Animals were euthanized at 12 weeks. The esophagus was harvested en-bloc and processed for histologic assessment by a board certified pathologist, blinded to the animal treatment group. Reflux was graded by severity and defined as the presence of inflammation in the esophageal squamous mucosa.

RESULTS

Rats who underwent SG had significantly increased reflux severity, compared with sham and HFD alone (21.1% versus 0% versus 4.5%, P = .02), respectively. No difference was demonstrated in negative, mild, or moderate esophagitis between the control, sham, and sleeve groups. Using nonparametric ANOVA, the mean severity score for severe esophagitis was significantly increased in the SG group versus sham or HFD group (1.5 versus .81 versus 1.36, P = .0202) respectively. Following multinomial logistic regression to assess for confounding variables to the severity scores, final weight, and change in weight, had no effect on severity of esophagitis between the 3 groups (P > .373).

CONCLUSIONS

SG is independently associated with histopathologic changes consistent with severe esophagitis in an animal model, likely secondary to gastroesophageal reflux.

Gold nanorods and curcumin-loaded nanomicelles for efficient in vivo photothermal therapy of Barrett's esophagus

Aim: Provide an enhanced local drug delivery, nanoparticle(s) to minimize systemic effects and achieve enhanced permeability and drug retention into abnormal cells and stroma. Materials & methods: Here a simultaneous loading of lipophilic gold nanorods (GNRs) and curcumin into polymeric nanomicelles made of biocompatible PLGA-b-PEG copolymer through a double re-emulsification process has been developed. Results: Initial results in vitro on Barrett's esophagus and esophageal adenocarcinoma cell lines demonstrated a significant reduction in cell viability with curcumin and GNRs exposure (p < 0.05). In vivo Barrett's-associated animal model confirmed these results with successful in vivo demonstrated eradication of all high-grade dysplastic premalignant cancer cells. Conclusion: The synthesis of this novel nanosystem containing GNRs and curcumin is safe and effective in treating and eradicating premalignant esophageal adenocarcinoma.

Regenerative Medicine Strategies for Esophageal Repair

Pathologies that involve the structure and/or function of the esophagus can be life-threatening. The esophagus is a complex organ comprising nonredundant tissue that does not have the ability to regenerate. Currently available interventions for esophageal pathology have limited success and are typically associated with significant morbidity. Hence, there is currently an unmet clinical need for effective methods of esophageal repair. The present article presents a review of esophageal disease along with the anatomic and functional consequences of each pathologic process, the shortcomings associated with currently available therapies, and the latest advancements in the field of regenerative medicine with respect to strategies for esophageal repair from benchtop to bedside.

Translational research on esophageal adenocarcinoma: from cell line to clinic

Human esophageal adenocarcinoma (EAC) cell lines have made a substantial contribution to elucidating mechanisms of carcinogenesis and drug discovery. Model research on EAC relies almost entirely on a relatively small set of established tumor cell lines because appropriate animal models are lacking. Nowadays, more than 20% of all fundamental translational research studies regarding EAC are partially or entirely based on these cell lines. The ready availability of these cell lines to investigators worldwide have resulted in more than 250 publications, including many examples of important biomedical discoveries. The high genomic similarities (but certainly not completely identical) between the EAC cell lines and their original tumors provide rational for their use. Recently, in a collaborative effort all available EAC cell lines have been verified resulting in the establishment of a reliable panel of 10 EAC cell lines. It could be expected that the value of these cell lines increases as unlimited source of tumor material because new biomedical techniques require more tumor cells and the supply of viable tumor cells is diminishing because of neoadjuvant chemo(radio)therapy of patients with EAC. Here, we review the history of the EAC cell lines and their utility in translational research and biomedical discovery.

Involvement of luminal nitric oxide in the pathogenesis of the gastroesophageal reflux disease spectrum

Over the last 3 decades, the incidence of esophageal adenocarcinoma has dramatically increased in Western countries; a similar increase may be observed in Asian countries in the near future. Esophageal adenocarcinoma arises from a sequential gastroesophageal reflux disease (GERD) spectrum from reflux erosive esophagitis, to Barrett's esophagus, and finally to esophageal adenocarcinoma. At present, gastric acid and bile are assumed to be primarily involved in the etiology of the GERD spectrum. We reported in 2002 that, at the gastroesophageal junction in humans, abundant amounts of nitric oxide (NO) are generated luminally through the entero-salivary re-circulation of dietary nitrate. Since then, we have carried out a series of experiments to demonstrate that NO diffuses into the adjacent epithelium at cytotoxic levels. This diffusion results in disruption of the epithelial barrier function, exacerbation of inflammation, acceleration of columnar transformation in the esophagus (Barrett's esophagus) via the induction of caudal-type homeobox 2, and the shifting of carcinogenic N-nitroso compound formation from the luminal to epithelial compartment. These results suggest that, in addition to conventionally recognized causative factors, luminal NO could also be involved in the pathogenesis of the GERD spectrum. In addition, we recently showed that there is a prominent gender-related difference in NO-related cytotoxicity in the esophagus and that estrogen attenuated the esophageal tissue damage via the estrogen receptor in female rats. The role of estrogen in attenuating the esophageal tissue damage in NO-related esophageal damage could explain the well-recognized male predominance in the GERD spectrum in humans.

Establishing magnetic resonance imaging as an accurate and reliable tool to diagnose and monitor esophageal cancer in a rat model

OBJECTIVE

To assess the reliability of magnetic resonance imaging (MRI) for detection of esophageal cancer in the Levrat model of end-to-side esophagojejunostomy.

BACKGROUND

The Levrat model has proven utility in terms of its ability to replicate Barrett's carcinogenesis by inducing gastroduodenoesophageal reflux (GDER). Due to lack of data on the utility of non-invasive methods for detection of esophageal cancer, treatment efficacy studies have been limited, as adenocarcinoma histology has only been validated post-mortem. It would therefore be of great value if the validity and reliability of MRI could be established in this setting.

METHODS

Chronic GDER reflux was induced in 19 male Sprague-Dawley rats using the modified Levrat model. At 40 weeks post-surgery, all animals underwent endoscopy, MRI scanning, and post-mortem histological analysis of the esophagus and anastomosis. With post-mortem histology serving as the gold standard, assessment of presence of esophageal cancer was made by five esophageal specialists and five radiologists on endoscopy and MRI, respectively.

RESULTS

The accuracy of MRI and endoscopic analysis to correctly identify cancer vs. no cancer was 85.3% and 50.5%, respectively. ROC curves demonstrated that MRI rating had an AUC of 0.966 (p<0.001) and endoscopy rating had an AUC of 0.534 (p = 0.804). The sensitivity and specificity of MRI for identifying cancer vs. no-cancer was 89.1% and 80% respectively, as compared to 45.5% and 57.5% for endoscopy. False positive rates of MRI and endoscopy were 20% and 42.5%, respectively.

CONCLUSIONS

MRI is a more reliable diagnostic method than endoscopy in the Levrat model. The non-invasiveness of the tool and its potential to volumetrically quantify the size and number of tumors likely makes it even more useful in evaluating novel agents and their efficacy in treatment studies of esophageal cancer.

Stromal cells participate in the murine esophageal mucosal injury response

We identified α-smooth muscle actin (α-SMA)- and vimentin-expressing spindle-shaped esophageal mesenchymal cells in the adult and neonate murine esophageal lamina propria. We hypothesized that these esophageal mesenchymal cells express and secrete signaling and inflammatory mediators in response to injury. We established primary cultures of esophageal mesenchymal cells using mechanical and enzymatic digestion. We demonstrate that these primary cultures are nonhematopoietic, nonendothelial, stromal cells with myofibroblast-like features. These cells increase secretion of IL-6 in response to treatment with acidified media and IL-1β. They also increase bone morphogenetic protein (Bmp)-4 secretion in response to sonic hedgehog. The location of these cells and their biological functions demonstrate their potential role in regulating esophageal epithelial responses to injury and repair.

Can the rat be used as a valid model of human esophageal adenocarcinoma?

Animal models of Barrett's metaplasia and esophageal adenocarcinoma are important to further characterize the disease and test potential therapies. This paper reviews the development of the surgical model of esophageal adenocarcinoma in the rat and considers whether this model provides a biologically accurate representation of Barrett's esophagus and esophageal adenocarcinoma in humans.

Bile acid and inflammation activate gastric cardia stem cells in a mouse model of Barrett-like metaplasia

Esophageal adenocarcinoma (EAC) arises from Barrett esophagus (BE), intestinal-like columnar metaplasia linked to reflux esophagitis. In a transgenic mouse model of BE, esophageal overexpression of interleukin-1β phenocopies human pathology with evolution of esophagitis, Barrett-like metaplasia and EAC. Histopathology and gene signatures closely resembled human BE, with upregulation of TFF2, Bmp4, Cdx2, Notch1, and IL-6. The development of BE and EAC was accelerated by exposure to bile acids and/or nitrosamines, and inhibited by IL-6 deficiency. Lgr5(+) gastric cardia stem cells present in BE were able to lineage trace the early BE lesion. Our data suggest that BE and EAC arise from gastric progenitors due to a tumor-promoting IL-1β-IL-6 signaling cascade and Dll1-dependent Notch signaling.

Acid-induced COX-2 expression and prostaglandin E2 production via activation of ERK1/2 and p38 MAPK in cultured feline esophageal smooth muscle cells

Cyclooxygenase (COX)-2 is known to play an important role in inflammatory conditions such as reflux esophagitis resulting from acid reflux. In this study, we tested whether an acidic medium (pH 4.0) induces an increase in COX-2 expression or PGE(2) production, and explored the implication of mitogen-activated protein kinases (MAPKs) activation in these responses in cultured cat esophageal smooth muscle cells. Acidic cytotoxicity was assessed and expression changes in COXs or phosphorylated MAPKs were analyzed by Western blotting. PGE(2) production was measured by immunoassay. No significant decrease in cell viability was observed for 6 h exposure to acidic medium. COX-2 expression and PGE(2) production significantly increased to maximal levels at 6 h exposure to acidic medium. The cells also exhibited significant activation of ERK1/2 and p38 MAPK, but not JNK within 10 min under acidic medium. The increments of COX-2 expression and PGE(2) production by acidic medium were decreased by pretreatment with PD98059 or SB202190, respectively. These results suggest that acidic environments may enhance the COX-2 expression and PGE(2) production through activation of ERK1/2 and p38 MAPK in the cultured cat esophageal smooth muscle cells.

The association of manganese superoxide dismutase expression in Barrett's esophageal progression with MnTBAP and curcumin oil therapy

BACKGROUND

The aim of this study was to investigate the relationship between reflux induced bile insult and MnSOD expression, as well as to examine therapies to preserve MnSOD expression. Additionally, we sought to examine the relationship between MnSOD protein expression and MnSOD enzymatic activity.

METHODS

MnSOD protein expression was determined by Western blot assay and enzymatic activity was determined by SOD assay. The enzymatic activity of the Het-1A and Bar-T cells were compared both before and after treatments.

RESULTS

MnSOD expression in Het-1A cells was decreased after bile salt exposure. The cells that received MnTBAP or curcumin oil pretreatment showed increased MnSOD expression compared with control untreated cells. The Bar-T cells showed an increase in MnSOD expression after treatment with bile salts. The cells that were pretreated with MnTBAP displayed a larger increase in MnSOD expression compared with the cells that were not pretreated prior to bile salt exposure. The MnSOD activity was significantly different between the untreated cell lines (P = 0.01) and after treatment with bile salt (P = 0.03). Additionally, Bar-T cells had significantly less MnSOD activity than Het-1A cells after each of the pretreatments.

CONCLUSIONS

We demonstrated preservation of MnSOD expression in Het-1A cells that were pretreated with antioxidants including MnTBAP, curcumin oil, and certain berry extracts. Additionally, we demonstrated that Bar-T cells have significantly less MnSOD activity than Het-1A cells. These finding have important implications for future studies regarding chemoprevention and the treatment of esophageal cancer.

Barrett's esophagus and animal models

The following on Barrett's esophagus (BE) and animal models contains commentaries on the factors of BE carcinogenesis; a duodenoesophageal reflux model; translation of targeted therapies for esophageal adenocarcinoma; and novel target regimens selected through a proteomics screen.

Effect on pro-inflammatory and antioxidant genes and bioavailable distribution of whole turmeric vs curcumin: Similar root but different effects

Curcuma longa is a perennial member of the Zingiberaceae family, and cultivated mainly in India, and Southeast Asia. The hypothesis for this study is that turmeric will have distinctive effects from curcumin due to the presence of other bioactive compounds. Thirty Eight-week old Sprague-Dawley rats were separated into three oral feeding groups. Group 1, standard rat chow, Control diet - AIN 93M, group 2 - Curcumin - 700ppm or 0.7g/kg diet, and group 3 - Turmeric - 14,000ppm or 14g/kg diet for a total of 3weeks. One group of rats were feed all three diets only and another group underwent esophagoduodenal anastomosis to evaluate the effects of bioavailability. Curcumin diet did not increase the transcription of mRNA of TNF-alpha, IL-6, iNOS, and COX-2. The average fold change in the mRNAs level was not significant. Whereas turmeric diet increases the levels of IL-6 (1.9-fold, p=0.05), iNOS (4.39-fold, p=0.02), IL-8 (3.11-fold, p=0.04), and COX-2 (2.02-fold, p=0.05), suggesting that turmeric either was more bioavailable or had more affect on pro-inflammatory genes compare to curcumin diet. We have demonstrated the molecular effects of curcumin and turmeric in the role as an anti-inflammatory therapy. However, significant bioavailable differences do occur and must be considered in further chemopreventative investigative trials the setting of reflux esophagitis, Barrett's esophagus, and other upper gastrointestinal cancers.

p73 protein regulates DNA damage repair

Although the p53 tumor suppressor is relatively well characterized, much less is known about the functions of other members of the p53 family, p73 and p63. Here, we present evidence that in specific pathological conditions caused by exposure of normal cells to bile acids in acidic conditions, p73 protein plays the predominant role in the DNA damage response. These pathological conditions frequently occur during gastric reflux in the human esophagus and are associated with progression to esophageal adenocarcinoma. We found that despite strong DNA damage induced by bile acid exposure, only p73 (but not p53 and p63) is selectively activated in a c-Abl kinase-dependent manner. The activated p73 protein induces DNA damage repair. Using a human DNA repair PCR array, we identified multiple DNA repair genes affected by p73. Two glycosylases involved in base excision repair, SMUG1 and MUTYH, were characterized and found to be transcriptionally regulated by p73 in DNA damage conditions. Using a surgical procedure in mice, which recapitulates bile acid exposure, we found that p73 deficiency is associated with increased DNA damage. These findings were further investigated with organotypic and traditional cell cultures. Collectively our studies demonstrate that p73 plays an important role in the regulation of DNA damage repair.

Early morbidity encountered in the dietary-related mouse model of Barrett's esophagus: a question of zinc?

Recently, a mouse model for Barrett's esophagus based on a zinc-deficient diet supplemented with deoxycholic bile acids has been published. The aim of this study was to attempt to reproduce these data and extend them by employing genetically modified mice and intraperitoneal iron supplementation. The study design encompassed six experimental groups (wild type, Apc-mutant and Smad4-mutant mice, with or without iron injections), with all animals fed with the zinc-deficient diet supplemented with deoxycholic bile acids. All treatments were started at 3-5 weeks of age (the majority [78%] at 5 weeks). Animals were scheduled for euthanasia at two distinct time points, namely at 3 and 6 months of age. All mice showed signs of considerable distress already 4 weeks after the start of the modified diets, and had to be euthanized before the first evaluation time point (mean age 9.3 weeks, range 5-15 weeks). No differences were observed between wild type and genetically modified mice, or between animals with or without iron supplementation. On histological examination, we could not detect any lesions (Barrett's esophagus-like or tumors) other than esophagitis. In the currently presented experimental settings, we were not able to reproduce the mouse model according to which Barrett's-like lesions could be detected in animals fed with the zinc-deficient diet supplemented with deoxycholic bile acids.

Exogenous luminal nitric oxide exposure accelerates columnar transformation of rat esophagus

Exposure of the esophageal mucosa to refluxed gastroduodenal contents is recognized to be an important risk factor for Barrett's esophagus (BE). At the human gastroesophageal junction, nitric oxide is generated luminally through the enterosalivary recirculation of dietary nitrate, and in cases with gastroesophageal reflux, the site of luminal nitric oxide generation could shift to the distal esophagus. The aim of this study is to investigate whether exogenous luminal nitric oxide could promote the development of BE in rats. Sodium nitrite plus ascorbic acid were administered to a rat surgical model of BE, in which the gastroduodenal contents were refluxed into the esophagus to generate exogenous luminal nitric oxide in the esophagus by the acid-catalyzed chemical reaction between the 2 reagents. The emergence of BE was evaluated histologically in the early phase (several weeks) after the surgery with or without exogenous nitric oxide administration. To elucidate the histogenesis of BE, CDX2, MUC2 and MUC6 expressions were investigated immunohistochemically. Coadministration of sodium nitrite plus ascorbic acid significantly accelerated the timing of emergence and increased the area of BE compared with controls. Administration of either reagent alone did not show any promotive effects on BE formation. Immunohistochemically, the columnar epithelium thus induced was similar to the specialized intestinal metaplasia in human BE. The results of this animal model study suggest that exogenous luminal nitric oxide could be involved in the pathogenesis of the columnar transformation of the esophagus. Further studies in human are warranted.

New models of neoplastic progression in Barrett's oesophagus

Research in Barrett's oesophagus, and neoplastic progression to OAC (oesophageal adenocarcinoma), is hobbled by the lack of good pre-clinical models that capture the evolutionary dynamics of Barrett's cell populations. Current models trade off tractability for realism. Computational models are perhaps the most tractable and can be used both to interpret data and to develop intuitions and hypotheses for neoplastic progression. Tissue culture models include squamous cell lines, Barrett's oesophagus cell lines and OAC cell lines, although it was recognized recently that BIC-1, SEG-1 and TE-7 are not true OAC cell lines. Some of the unrealistic aspects of the micro-environment in two-dimensional tissue culture may be overcome with the development of three-dimensional organotypic cultures of Barrett's oesophagus. The most realistic, but least tractable, model is a canine surgical model that generates reflux and leads to an intestinal metaplasia. Alternatively, rat surgical models have gained popularity and should be tested for the common genetic features of Barrett's oesophagus neoplastic progression in humans including loss of CDKN2A (cyclin-dependent kinase inhibitor 2A) and TP53 (tumour protein 53), generation of aneuploidy and realistic levels of genetic diversity. This last feature will be important for studying the effects of cancer-prevention interventions. In order to study the dynamics of progression and the effects of an experimental intervention, there is a need to follow animals longitudinally, with periodic endoscopic biopsies. This is now possible and represents an exciting opportunity for the future.

New models of neoplastic progression in Barrett's oesophagus

Research in Barrett's oesophagus, and neoplastic progression to OAC (oesophageal adenocarcinoma), is hobbled by the lack of good pre-clinical models that capture the evolutionary dynamics of Barrett's cell populations. Current models trade off tractability for realism. Computational models are perhaps the most tractable and can be used both to interpret data and to develop intuitions and hypotheses for neoplastic progression. Tissue culture models include squamous cell lines, Barrett's oesophagus cell lines and OAC cell lines, although it was recognized recently that BIC-1, SEG-1 and TE-7 are not true OAC cell lines. Some of the unrealistic aspects of the micro-environment in two-dimensional tissue culture may be overcome with the development of three-dimensional organotypic cultures of Barrett's oesophagus. The most realistic, but least tractable, model is a canine surgical model that generates reflux and leads to an intestinal metaplasia. Alternatively, rat surgical models have gained popularity and should be tested for the common genetic features of Barrett's oesophagus neoplastic progression in humans including loss of CDKN2A (cyclin-dependent kinase inhibitor 2A) and TP53 (tumour protein 53), generation of aneuploidy and realistic levels of genetic diversity. This last feature will be important for studying the effects of cancer-prevention interventions. In order to study the dynamics of progression and the effects of an experimental intervention, there is a need to follow animals longitudinally, with periodic endoscopic biopsies. This is now possible and represents an exciting opportunity for the future.

Dietary freeze-dried black raspberry's effect on cellular antioxidant status during reflux-induced esophagitis in rats

INTRODUCTION

Esophageal cancer consists of two distinct types, esophageal adenocarcinoma (EAC) and squamous cell carcinoma, both of which differ significantly in their etiology. Freeze-dried black raspberry (BRB) has been consistent in its ability to modulate the biomarkers and reduce the incidence of carcinogen-induced squamous cell carcinoma in rats. In our previous studies in the esophagoduodenal anastomosis (EDA) model, we have shown that the early modulation of manganese superoxide dismutase (MnSOD) significantly correlates with the development of reflux-induced EAC in rats. In this study we looked at the short-term effects of a BRB-supplemented diet on the modulation of antioxidant enzymes in reflux-induced esophagitis.

METHODS

Male SD rats (8 wk old; n = 3-5) were randomized into three groups--sham-operated, fed control AIN-93M diet (SH-CD), EDA operated and fed either control diet (EDA-CD) or 2.5% (w/w) BRB diet (EDA-BRB). The effect of both reflux and dietary supplementation was analyzed 2 and 4 wk after EDA surgery.

RESULTS

Animals in the EDA groups had significantly lower weight gain and diet intake compared to SH-CD (P < 0.05). The sham-operated animals received an average esophagitis score of 0.1 ± 0.1; this increased significantly in EDA-CD animals to 1.8 ± 0.14 (P < 0.001 versus SH-CD) and in EDA-BRB group to 1.7 ± 0.06 (P < 0.001 versus SH-CD), with BE changes also present. However, dietary supplementation of BRB did not alter or ameliorate the grade of esophagitis or the induction of BE. BRB diet caused a 43% increase in MnSOD levels compared to EDA-CD (0.73 ± 0.16; P = 0.09); however, this effect was not statistically significant and at 4 wk, EDA-CD (0.58 ± 0.12) showed an increase in MnSOD expression compared to SH-CD (0.34 ± 0.01).

CONCLUSIONS

In conclusion, our data suggest that dietary BRB does not increase the levels of cellular antioxidant enzymes or reduce the levels of lipid peroxidation compared to a control diet, in a short-term study of gastroesophageal reflux induction in the EDA animal model. However, it remains to be tested whether this is indicative of its ineffectiveness to inhibit reflux-induced EAC incidence over the long term.

The resistance of esophageal adenocarcinoma to bile salt insult is associated with manganese superoxide dismutase expression

BACKGROUND

Bile acids are implicated as etiologic agents in esophageal cancer. We sought to analyze the impact of bile acid exposure on esophageal epithelial cells, Barrett's metaplastic cells (BE), esophageal adenocarcinoma cells (EAC), and esophageal squamous carcinoma cell (ESC). We sought to determine if cellular resistance is related to manganese superoxide dismutase expression.

METHODS

Cells were exposed to sodium choleate (CA), sodium deoxycholate (DCA), sodium glycocholate (GCA), sodium taurocholate (TCA), or a 1:1 mixture (MIX) of reagents at concentrations in the range 0.2-0.8 mM. Cell viability was evaluated by MTT assay. Manganese superoxide dismutase (MnSOD) expression was analyzed by Western blot. Statistical analysis was performed using SPSS ver. 17.0, SPSS Inc., Chicago, IL.

RESULTS

Bile salt exposure inhibited cell viability in esophageal squamous cells in time- and growth-dependent manner. There was a 50% decrease in cell viability from 4 to 24 h. BE, EAC, and ESC cell lines were more resistant to bile insult. In untreated cell lines, MnSOD expression was significantly decreased in EAC and ESC cell lines compared with esophageal squamous epithelial cells and BE cells (P=0.002). Exposure of ESC cells to bile salt increased MnSOD expression.

CONCLUSION

The confirmation of the role of reactive oxygen species (ROS) and bile acids in esophageal carcinogenesis has interesting implications for chemoprevention in patients with reflux esophagitis and Barrett's esophagus. Further studies are necessary to assess the preventative role of antioxidant supplementation.

Positive correlation of image analysis by mini-endoscopy with micro-PET scan and histology in rats after esophagoduodenal anastomosis

BACKGROUND

Visual inspection of induced carcinogenic transformation is of crucial interest when evaluating growth patterns and therapeutic effects. In previous studies we have used micro-PET scan to analyze the esophageal adenocarcinoma (EAC) transformation in an intact rat model of esophagoduodenal anastomosis (EDA), in which intestinal metaplasia and EAC were reproduced successfully. Our current study aimed to test the feasibility of evaluating the outcomes of our EDA model with a recently developed mini-endoscope.

METHODS

EDA was performed as described previously. Postoperative rats underwent evaluation with upper endoscopy with the mini-endoscope (±endoscopic biopsy) and a micro-PET scan with (18)F-FDG 3 months after the EDA procedure. Rats were euthanized and the esophagi were collected for histological observation, immunohistochemical staining, and TdT labeling assay. We compared the endoscopic images with the radiographic images of (18)F-FDG uptake by micro-PET scan and correlated the endoscopic images with the histological changes in the EDA rats.

RESULTS

The endoscope provided visualization of the entire esophageal tract and upper stomach, with the smallest detectable lesion being 0.5 mm in diameter. Mini-endoscopy was performed regularly and was tolerated without any significant procedure-related alterations in the esophageal tract. The visualized esophageal lesion correlated well with the micro-PET image and the histological changes in the EDA rats.

CONCLUSIONS

The new mini-endoscope constitutes a practical and reliable tool for diagnosis and regular follow-up of the esophagus in rats. Lesions identified by endoscopic observation were consistent with the changes found in the micro-PET scan, histopathology, and alteration of cellular and molecular events in esophageal mucosa. This instrument will allow for serial endoscopic evaluations, similar to endoscopic screening in humans, which will significantly enhance the preclinical development and evaluation of experimental intravesical antitumor therapies.

Diet composition affects surgery-associated weight loss in rats with a compromised alimentary tract

BACKGROUND

Esophageal adenocarcinoma (EAC) is the fastest growing cancer in terms of incidence and has a high mortality rate. The animal model to study EAC uses esophagoduodenal anastomosis (EDA) to induce mixed-reflux (bile/acid) causing esophagitis, Barrett's esophagus, and EAC sequence within 6 mo. However, the lack of fully functional stomach in these rats leads to the development of malnutrition.

METHODS

We have assessed the ability of a chemically pure, purified ingredient diet (AIN-93M) to reduce surgery-associated malnutrition in rats that have undergone the EDA-surgery. Animals were either sham- (SH) or EDA-operated and fed either a grain-based rodent diet (RD) (SH-RD, n=3; EDA-RD, n=10) or a purified diet (PD) (SH-PD, n=4; EDA-PD, n=11). The animals were weighed periodically for assessment of weight gain and euthanized at the end of 24 wk to measure esophageal tumor incidence.

RESULTS

Animals that underwent sham surgery continued to gain weight throughout the study period and no tumors were detected. The EDA-operated animals had significantly lower weight gain compared with sham animals. There was no significant difference in weight gain among EDA animals fed two different types of diets until 9 wk after the surgery. After 9 wk, EDA-RD continued to lose weight significantly, whereas the weight loss leveled in EDA-PD (P<0.001). At termination, neither tissue histopathology nor tumor incidence was significantly different between the groups.

CONCLUSION

These results show that compared with a natural ingredient diet, a purified ingredient diet can reduce surgery-associated weight loss in rats with a compromised alimentary tract. This reduction in malnutrition has the potential to reduce the confounding effects of weight loss on future animal studies reported.

CDX2 hox gene product in a rat model of esophageal cancer

Background

Barrett's mucosa is the precursor of esophageal adenocarcinoma. The molecular mechanisms behind Barrett's carcinogenesis are largely unknown. Experimental models of longstanding esophageal reflux of duodenal-gastric contents may provide important information on the biological sequence of the Barrett's oncogenesis.

Methods

The expression of CDX2 hox-gene product was assessed in a rat model of Barrett's carcinogenesis. Seventy-four rats underwent esophago-jejunostomy with gastric preservation. Excluding perisurgical deaths, the animals were sacrificed at various times after the surgical treatment (Group A: <10 weeks; Group B: 10–30 weeks; Group C: >30 weeks).

Results

No Cdx2 expression was detected in either squamous epithelia of the proximal esophagus or squamous cell carcinomas. De novo Cdx2 expression was consistently documented in the proliferative zone of the squamous epithelium close to reflux ulcers (Group A: 68%; Group B: 64%; Group C: 80%), multilayered epithelium and intestinal metaplasia (Group A: 9%; Group B: 41%; Group C: 60%), and esophageal adenocarcinomas (Group B: 36%; Group C: 35%). A trend for increasing overall Cdx2 expression was documented during the course of the experiment (p = 0.001).

Conclusion

De novo expression of Cdx2 is an early event in the spectrum of the lesions induced by experimental gastro-esophageal reflux and should be considered as a key step in the morphogenesis of esophageal adenocarcinoma.

Different redox states in malignant and nonmalignant esophageal epithelial cells and differential cytotoxic responses to bile acid and honokiol

Esophageal adenocarcinoma (EAC) is a highly lethal cancer in western countries. EAC cells are believed to develop from esophageal epithelial cells through complex transformation processes involving inflammation and oxidative stress. The purpose of this study was to compare the redox status of malignant and nonmalignant esophageal epithelial cells and to test their responses to bile acid-induced oxidative stress and to treatment with honokiol (HNK), a natural product with anticancer activity. We demonstrated that esophageal adenocarcinoma cells express significantly higher levels of antioxidant molecules and were resistant to reactive oxygen species (ROS) stress induced by bile acid, but were sensitive to the cytotoxic action of HNK. Mechanistic study showed that HNK caused cancer cell death by disruption of mitochondrial transmembrane potential and was correlated with cyclophilin D (CypD) expression. Inhibition of CypD by cyclosporin A or abrogation of its expression by siRNA significantly suppressed the cytotoxicity of HNK, suggesting that CypD may be a key molecule that mediates the cytotoxicity. Our study suggests that the high antioxidant capacity in EAC cells confers on them the ability to survive the oxidative microenvironment in the reflux esophagus, and that HNK is a promising compound to kill the transformed cells preferentially.

Carcinogenesis of the upper gastrointestinal tract induced by N-methyl-N'-nitro-nitrosoguanidine and reflux of duodenal contents in the rat

PURPOSE

To investigate the combined effects of reflux of duodenal contents through the pylorus and treatment with N-methyl-N'-nitro-nitrosoguanidine (MNNG) on the development of lesions in the glandular stomach, at the gastrojejunal anastomosis and in the forestomach of rats.

METHODS

Eighty Male Wistar rats were divided into 4 groups: G1: MNNG + Reflux, G2: Reflux, G3: MNNG and G4: Gastrostomy. MNNG was given in the drinking water (100 mg/ml) for 12 weeks and then two groups (G1 and G2) were submitted to a gastrojejunal anastomosis followed by section of the afferent loop and suture of both stumps to allow reflux of duodenal contents through the pylorus. The animals were sacrificed 18 and 36 weeks after surgery. The lesions obtained in the antral mucosa, at the gastrojejunal anastomosis and in the forestomach were analysed histologically.

RESULTS

Duodenal reflux induced proliferative lesions at both glandular and squamous mucosa of the stomach. In the antrum, adenomatous hyperplasia (AH) was observed in 20% and 50% of the animals at the 18th and 36th weeks respectively. Aditionally 85% of the animals presented AH at the gastrojejunal anastomosis and 60% developed squamous hyperplasia at the squamous portion of the stomach. MNNG treatment plus duodenal reflux enhanced the development of malignant tumors at both glandular and squamous mucosa, since there were 30% of antral adenocarcinomas and 45% of squamous carcinomas at the 18th week and the frequency of these malignant tumors rose to 50% in the antrum and 65% in the squamous mucosa at the 36th week.

CONCLUSION

The reflux of duodenal contents through the pylorus enhanced the development of proliferative lesions, benign and malignant, in the glandular stomach and in the forestomach of rats.

Esophageal adenocarcinoma in "mice and men": back to basics!

Adenocarcinoma related to Barrett's esophagus (BE) is increasing in the West faster than any other cancer. There are many potential chemopreventive agents as well as predictive biomarkers of cancer progression, but what is required is a robust high-throughput model in which to test hypotheses preclinically. The pathophysiology of metaplasia and cancer has been studied in 10 animal species. Though they have considerable genetic divergence, anatomical dissimilarity, and experimental flaws, they have provided some data to test in the clinic, especially relating to activation of common genetic pathways, role of hypergastrinemia, and duodenogastric reflux in cancer progression. In this regard, the human postesophagectomy model, which has a 30% recurrence of BE within 3 yr and a 5% recurrence of adenocarcinoma over 10 yr, is now being utilized to understand how human metaplasia occurs. Furthermore, improved clinical trial designs mean that more sophisticated questions can be addressed in man.

American and Japanese rats of the same species: are they same?

BACKGROUND

We have previously reported a chronic acid reflux esophagitis model using Japanese Wistar male (JWM) rats. The aim of this study is to discuss unexpected differences encountered within the same species bred in different countries.

MATERIALS AND METHODS

In JWM rats via a midline laparotomy the limiting ridge of the stomach was ligated and the duodenum was covered with a small piece of an 18 Fr. catheter. We subsequently tried to reproduce the same model using American Wistar male (AWM) and subsequently with female (AWF) rats.

RESULTS

The 3-wk survival rate of AWM rats (30%) was significantly lower than for JWM rats (90%) due to differences in growth curve and eating behaviors. On the other hand, the growth curve of AWF rats was similar to JWM rats. Still, the 3-wk survival rate was only 40% mainly due to different eating patterns. Since then we have modified our postoperative care to include restricted access to food and other objects and have achieved a 3-wk survival of 80%, which is the same as JWM rats.

CONCLUSIONS

Growth curve and eating behavior of rats from different countries exhibit significant differences even within the same species. It is important that such differences be taken into account when reproducing animal models created elsewhere.