Human embryonic gastric xenografts in nude mice: a new model of Helicobacter pylori infection

Animal models to study acute and chronic intestinal inflammation in mammals

Acute and chronic inflammatory diseases of the intestine impart a significant and negative impact on the health and well-being of human and non-human mammalian animals. Understanding the underlying mechanisms of inflammatory disease is mandatory to develop effective treatment and prevention strategies. As inflammatory disease etiologies are multifactorial, the use of appropriate animal models and associated metrics of disease are essential. In this regard, animal models used alone or in combination to study acute and chronic inflammatory disease of the mammalian intestine paired with commonly used inflammation-inducing agents are reviewed. This includes both chemical and biological incitants of inflammation, and both non-mammalian (i.e. nematodes, insects, and fish) and mammalian (i.e. rodents, rabbits, pigs, ruminants, dogs, and non-human primates) models of intestinal inflammation including germ-free, gnotobiotic, as well as surgical, and genetically modified animals. Importantly, chemical and biological incitants induce inflammation via a multitude of mechanisms, and intestinal inflammation and injury can vary greatly according to the incitant and animal model used, allowing studies to ascertain both long-term and short-term effects of inflammation. Thus, researchers and clinicians should be aware of the relative strengths and limitations of the various animal models used to study acute and chronic inflammatory diseases of the mammalian intestine, and the scope and relevance of outcomes achievable based on this knowledge. The ability to induce inflammation to mimic common human diseases is an important factor of a successful animal model, however other mechanisms of disease such as the amount of infective agent to induce disease, invasion mechanisms, and the effect various physiologic changes can have on inducing damage are also important features. In many cases, the use of multiple animal models in combination with both chemical and biological incitants is necessary to answer the specific question being addressed regarding intestinal disease. Some incitants can induce acute responses in certain animal models while others can be used to induce chronic responses; this review aims to illustrate the strengths and weaknesses in each animal model and to guide the choice of an appropriate acute or chronic incitant to facilitate intestinal disease.

Mouse models with human immunity and their application in biomedical research

Biomedical research in human beings is largely restricted to in vitro studies that lack complexity of a living organism. To overcome this limitation, humanized mouse models are developed based on immunodeficient characteristics of severe combined immunodeficiency (SCID) or recombination activating gene (Rag)(null) mice, which can accept xenografts. Peripheral constitution of human immunity in SCID or Rag(null) mice has been achieved by transplantation of mature human immune cells, foetal human thymus, bone marrow, liver tissues, lymph nodes or a combination of these, although efficiency needs to be improved. These mouse models with constituted human immunity (defined as humanized mice in the present text) have been widely used to investigate the basic principles of human immunobiology as well as complex pathomechanisms and potential therapies of human diseases. Here, elements of an ideal humanized mouse model are highlighted including genetic and non-genetic modification of recipient mice, transplantation strategies and proposals to improve engraftments. The applications of the humanized mice to study the development and response of human immune cells, human autoimmune diseases, virus infections, transplantation biology and tumour biology are reviewed as well.

Recombinant human thyrotropin stimulates thyroid angiogenesis in vivo

BACKGROUND

Endogenous TSH and rhTSH stimulate thyroid growth by a direct effect on thyrocytes. Our hypothesis was that rhTSH may also stimulate thyroid angiogenesis.

STUDY DESIGN

A normal human thyroid tissue sample was grafted into the epigastric area of 14 nude mice. Mice were divided in two groups of 7. The first group (treated mice) received rhTSH stimulation (0.014 UI/mouse/day for 3 weeks), while the second group (control mice) had saline. Histological study with special focus on vascular characteristics was performed by image analysis at day 21 for each graft. VEGF immunostaining score, determined by immunohistochemistry, was defined as the percentage of labeled thyrocytes score, plus an intensity score.

RESULTS

Thyroid follicles showed signs of increased colloid re-uptake activity in rhTSH group within a larger surface area than controls (p <0.01). Thyrocytes were taller in the rhTSH group (p <0.01). The diameter of capillary vessels was larger and the microvessels expansion more important in the rhTSH group (p <0.02). Relative capillary area, defined as the ratio between capillary area and follicular area, was also higher in the rhTSH group (p <0.02). VEGF immunostaining score was increased in the rhTSH group (p <0.01).

CONCLUSION

rhTSH stimulates angiogenesis and local VEGF expression in normal human thyroid.

Significance of cagA status and vacA subtypes of Helicobacter pylori in determining gastric histopathology: virulence markers of H. pylori and histopathology

BACKGROUND

It has been suggested that Helicobacter pylori strains containing the cytotoxin-associated gene A (cagA), and s1m1 genotype of vacuolating cytotoxin gene A (vacA) may have been associated with peptic ulcer disease. The aim of the present study was to analyze such an association of cagA presence and vacA subtypes of H. pylori with histopathological findings in patients with gastritis.

METHODS

Sixty-five independent H. pylori strains isolated from Turkish patients with gastritis were analyzed. The antral biopsy specimens were processed for culture and histopathology. Histopathological features were recorded and graded according to updated Sydney system. The vacA subtypes and cagA gene were tested by polymerase chain reaction.

RESULTS

Mild degree of antral density was associated with mild degree of gastric neutrophil infiltration (P = 0.010). Positive cagA status correlated significantly with the presence of atrophy (P = 0.035) and neutrophil infiltration (P < 0.001), but not with H. pylori density (P = 0.754) nor the degree of mononuclear cell infiltration (P = 0.945). The vacA subtypes were independent of gastric histopathology. The odds ratios for atrophy and neutrophil infiltration of cagA+ versus cagA- strains were 3.62 (95% confidence interval [CI]: 1.04-12.66) and 53.18 (95%CI: 11.08-255.23), respectively.

CONCLUSION

The presence of the cagA gene is strongly associated with atrophic and active gastritis. Distinct vacA subtypes of H. pylori appear to have no association with histopathological findings of gastritis.

Efficacy of sulforaphane in eradicating Helicobacter pylori in human gastric xenografts implanted in nude mice

Sulforaphane, an isothiocyanate abundant in the form of its glucosinolate precursor in broccoli sprouts, has shown in vitro activity against Helicobacter pylori. We evaluated the effect of sulforaphane in vivo against this bacterium by using human gastric xenografts in nude mice. H. pylori was completely eradicated in 8 of the 11 sulforaphane-treated grafts. This result suggests that sulforaphane might be beneficial in the treatment of H. pylori-infected individuals.

Breaking the species barrier: use of SCID mouse-human chimeras for the study of human infectious diseases

Mouse-human chimeras have become a novel way to model the interactions between microbial pathogens and human cells, tissues or organs. Diseases studied with human xenografts in severe combined immunodeficient (SCID) mice include Pseudomonas aeruginosa infection in cystic fibrosis, group A streptococci and impetigo, bacillary and amoebic dysentery, and AIDS. In many cases, disease in the human xenograft appears to accurately reproduce the disease in humans, providing a powerful model for identifying virulence factors, host responses to infection and the effects of specific interventions on disease. In this review, we summarize recent studies that have used mouse-human chimeras to understand the pathophysiology of specific bacterial and protozoan infections.

Clostridium difficile toxin B is an inflammatory enterotoxin in human intestine

BACKGROUND & AIMS

Clostridium difficile causes antibiotic-associated diarrhea and pseudomembranous colitis, diseases afflicting millions of people each year. Although C. difficile releases 2 structurally similar exotoxins, toxin A and toxin B, animal experiments suggest that only toxin A mediates diarrhea and enterocolitis. However, toxin A-negative/toxin B-positive strains of C. difficile recently were isolated from patients with antibiotic-associated diarrhea and colitis, indicating that toxin B also may be pathogenic in humans.

METHODS

Here we used subcutaneously transplanted human intestinal xenografts in immunodeficient mice to generate a chimeric animal model for C. difficile toxin-induced pathology of human intestine.

RESULTS

We found that intraluminal toxin B, like equivalent concentrations of toxin A, induced intestinal epithelial cell damage, increased mucosal permeability, stimulated interleukin (IL)-8 synthesis, and caused an acute inflammatory response characterized by neutrophil recruitment and tissue damage. Laser capture microdissection and real-time quantitative reverse-transcription polymerase chain reaction (RT-PCR) showed that intestinal epithelial cell-specific IL-8 gene expression also was increased significantly after luminal exposure to C. difficile toxins in vivo.

CONCLUSIONS

We conclude that C. difficile toxin B, like toxin A, is a potent inflammatory enterotoxin for human intestine. Future therapeutic or vaccine strategies for C. difficile infection therefore need to target both toxins.

Developmental patterns of mucin gene expression in human fetal small intestinal xenografts maintained in severe-combined immunodeficient mice

The lack of a suitable animal model that expresses human intestinal mucin genes limits the study of mucin function. The aim of this study was to examine whether human fetal intestinal xenografts, known to model host-restricted interactions with human-specific pathogens, express mucin genes in an appropriate developmental pattern when transplanted into severe-combined immunodeficient (scid) mice. Expression profiles for eight mucin genes were examined in human fetal ileal xenografts transplanted ectopically into scid mice for 10 wk. In situ hybridization was performed on fetal, xenograft, and adult intestinal tissue sections with 35S-labeled oligonucleotides specific to human tandem repeat sequences for MUC1, MUC2, MUC3, MUC4, MUC5AC, MUC5B, MUC6, and MUC7. Hybridization patterns observed with the MUC2, MUC3, MUC4, and MUC5AC probes demonstrated that mucin gene expression in xenografted fetal intestine was comparable to third trimester fetal and/or adult tissues. MUC2 and MUC5AC were expressed in a developmental-specific fashion. MUC5AC, expressed in first and early second trimester fetal bowel, was never detected in intestinal xenografts. MUC2 expression displayed a late fetal and/or adult-type hybridization pattern. MUC3 and MUC4 were not developmentally expressed. Appropriate developmental regulation of known intestinal mucin genes was recorded in ectopically grafted human fetal intestinal xenografts. Adult-like patterns of mucin gene expression in this model system will permit future studies aimed at characterizing cis/trans-acting factors that regulate mucin gene expression and function during development, disease, and wound healing and also in mucin-pathogen interactions during host defense.

Influence of Lewis antigen expression by Helicobacter pylori on bacterial internalization by gastric epithelial cells

The role of Helicobacter pylori lipopolysaccharide (LPS) Lewis antigens in infection is still not well known. We investigated the influence of Lewis antigen expression by H. pylori on its internalization by AGS cells and the epithelium of human gastric xenografts in nude mice using isogenic mutants in LPS biosynthetic genes. In vivo, colonization rates were unaffected by the change in H. pylori Lewis antigen expression, whereas the number of viable intracellular bacteria was significantly higher with wild-type H. pylori strains expressing Lewis antigens when compared to the isogenic mutants in both models. H. pylori strains expressing more Lewis X antigens (Le(x)) were internalized at a higher rate than those expressing less Le(x), type II Lewis antigens (Le(a) or Le(b)) alone, or no Lewis antigens. Thus, Lewis antigens appear to be involved in the internalization of H. pylori by the gastric epithelium.

Sulforaphane inhibits extracellular, intracellular, and antibiotic-resistant strains of Helicobacter pylori and prevents benzo[a]pyrene-induced stomach tumors

Gastric infection with Helicobacter pylori is a cosmopolitan problem, and is especially common in developing regions where there is also a high prevalence of gastric cancer. These infections are known to cause gastritis and peptic ulcers, and dramatically enhance the risk of gastric cancer. Eradication of this organism is an important medical goal that is complicated by the development of resistance to conventional antimicrobial agents and by the persistence of a low level reservoir of H. pylori within gastric epithelial cells. Moreover, economic and practical problems preclude widespread and intensive use of antibiotics in most developing regions. We have found that sulforaphane [(-)-1-isothiocyanato-(4R)-(methylsulfinyl)butane], an isothiocyanate abundant as its glucosinolate precursor in certain varieties of broccoli and broccoli sprouts, is a potent bacteriostatic agent against 3 reference strains and 45 clinical isolates of H. pylori [minimal inhibitory concentration (MIC) for 90% of the strains is Collapse

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MESH Headings

• Agaricales
• Amoxicillin/pharmacology
• Animals
• Anticarcinogenic Agents/pharmacology
• Benzo(a)pyrene
• Brassica
• Clarithromycin/pharmacology
• Drug Resistance, Microbial
• Female
• Helicobacter pylori/drug effects
• Helicobacter pylori/growth & development
• Helicobacter pylori/isolation & purification
• Humans
• Isothiocyanates
• Metronidazole/pharmacology
• Mice
• Mice, Inbred ICR
• Phytotherapy
• Stomach Neoplasms/chemically induced
• Stomach Neoplasms/microbiology
• Stomach Neoplasms/prevention & control
• Sulfoxides
• Thiocyanates/pharmacology

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Grants

• R01 CA094076 NCI NIH HHS
• CA 94076 NCI NIH HHS

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Affiliation(s)

Jed W Fahey Lewis B. and Dorothy Cullman Cancer Chemoprotection Center, Department of Pharmacology and Molecular Sciences, The Johns Hopkins University School of Medicine, 725 North Wolfe Street, Baltimore, MD 21205-2185, USA.
Xavier Haristoy
Patrick M Dolan
Thomas W Kensler
Isabelle Scholtus
Katherine K Stephenson
Paul Talalay
Alain Lozniewski

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Xenografted human whole embryonic and fetal entoblastic organs develop and become functional adult-like micro-organs

BACKGROUND AND AIMS

The aim of this study was to study the morphological and functional development in vivo of whole human embryonic and fetal stomachs, intestines, tracheas, and lungs, which would otherwise be ethically and technically impossible to perform in utero, by microsurgically grafting these organs into nude mice.

MATERIALS AND METHODS

Five hundred fifty-seven human organs obtained from legally aborted embryos and fetuses of 6-10 weeks were microsurgically grafted into nude mice for 1 to 273 days. Following different grafting times, biopsies were taken for optical and electron microscopy, in situ hybridization, and cellular kinetics studies. A catheter was introduced into the human organs in order to collect and analyze secretions.

RESULTS

All of the grafts took successfully. Macroscopic growth was fast during the first 6 to 10 weeks, following which organ size was stable. In situ hybridization studies detected only a minute level of mouse mesenchymal chimerism in the grafts. The different epithelial cells differentiated, became of adult type, and remained normal during the remainder of the grafting periods. The pH of gastric juice from stomachs grafted for 10 to over 90 days dropped from 8.0 +/- 0.1 to 1.58 +/- 0.29 over this time period (P < 0.001), intrinsic factor levels were stable, and pepsin ranged from 6.8 +/- 7.8 to 134 +/- 51 units (P < 0.001).

CONCLUSIONS

These results demonstrate that the development of entoblastic organs from human embryos and fetuses microsurgically grafted into nude mice is similar to that occurring in utero. As such, this method provides a model for the analysis of whole human organs in development and later normal adult-like micro-organs for physiological, therapeutic, and pathological studies.

Morphologic and functional development of whole human fetal stomachs grafted into nude mice

To study in vivo the cellular differentiation and secretion of human developing fetal stomach, ethically and technically impossible to perform in utero, 256 fetal stomachs were xenografted. Human stomachs from 6- to 10-week-old fetuses were grafted for 1-273 days into nude mice. Biopsies for immunohistochemistry, hybridization and electron microscopy were taken and a catheter introduced into the human stomach. Macroscopic growth was fast and cells in S phase were numerous during the first 9 weeks, then the stomach size was stable and the gastric mucosa, of adult type, remained normal. In situ hybridization detected only a minute mouse mesenchymal chimerism in the graft. Chromogranin A, intrinsic factor and H+/K+ adenosine triphosphatase were immunohistolocally detected in epithelial cells 20 days after grafting, gastrin was detected after 30 days and pepsinogen after 60 days. The pH in gastric juice, which was at 8.0 +/- 0.1 from days 10-25, dropped from 4.39 +/- 1.80 at 30 days to 1.58 +/- 0.29 at 90 days. Intrinsic factor was stable and pepsin ranged from 6.8 +/- 7.8 to 134 +/- 51 units at 90 days. The differentiation of the epithelial cells in xenografts was very accelerated in comparison to that in utero.

Bactericidal properties of the chloroform fraction from rhizomes of Aristolochia paucinervis Pomel

The deffated chloroform fraction (APRC) obtained from the rhizomes of Aristolochia paucinervis Pomel (Aristolochiaceae) has a high bacteriostatic activity against bacterial strains like Clostridium perfringens ATCC 13124 and Enterococcus faecalis ATCC 29212. Here, we report the bactericidal activity of APRC against both strains which was evaluated by using time-to kill assays. The results showed that APRC produced an intense time-dependent bactericidal effect against C. perfringens, achieving over a 24 h-period a 5log10-unit decrease in CFU/ml at a concentration > or =1.25 x MIC. In contrast, when tested against E. faecalis, APRC exhibited a concentration-dependent killing activity at concentrations of 1.25 x MIC and 2.5 x MIC, yielding to a decrease of 1.5 and 2.5log10-unit in CFU/ml at 4 h, respectively. However, substantial regrowth of E. faecalis occurred within 24 h. Ultrastructural alterations were observed for both exposed microorganisms by scanning and transmission electron microscopy.

The gastrointestinal ecosystem: a precarious alliance among epithelium, immunity and microbiota

The gastrointestinal (GI) tract is a complex ecosystem generated by the alliance of GI epithelium, immune cells and resident microbiota. The three components of the GI ecosystem have co-evolved such that each relies on the presence of the other two components to achieve its normal function and activity. Experimental systems such as cell culture, germ-free animal models and intestinal isografts have demonstrated that each member of the GI ecosystem can follow a predetermined developmental pathway, even if isolated from the other components of the ecosystem. However, the presence of all three components is required for full physiological function. Genetic or functional alterations of any one component of this ecosystem can result in a broken alliance and subsequent GI pathology. A more detailed understanding of the interactions among microbiota, GI epithelium and the immune system should provide insight into multiple human disease states.

Use of embryonic human trachea grown in nude mice to patch-repair congenital tracheal stenosis

BACKGROUND

Long congenital tracheal stenosis is a life-threatening condition, and the available surgical treatments do not give satisfactory long-term results.

METHODS

Human embryonic tracheas were implanted in the abdominal cavities of nude mice until their differentiation was completed. These differentiated tracheas were used to patch-repair surgically induced tracheal stenosis in piglets. The human, mouse, or pig origin, of all the cells in the two successive xenotransplants in the nude mouse and the pig, was determined on tissue sections by in situ hybridization with species-specific DNA probes.

RESULTS

The transplanted pigs thrived and reached normal adulthood, irrespective of the administration of immunosuppressive treatment. The human tracheal tissue developed in nude mice conserved human structures, with the exception of feeding capillaries, which were of mouse origin. The tracheal patch in the adult healthy pigs comprised only pig cells organized into a fibrous scar, which was covered by normal pig epithelium.

CONCLUSIONS

Results suggest that human embryonic trachea grown in nude mice can be successfully used as patch tracheoplasty for long congenital tracheal stenosis without conventional immunosuppression.

Acid secretion and response to pentagastrin or omeprazole in human fetal stomach xenografts

BACKGROUND

The dual capacity of stomach tissue to secrete acid and to respond to secretagogues is indicative of the terminal stages of gastric functional maturation. In this study 6- to 10-week-old human fetal stomachs xenografted into nude mice were used to study parietal cells' functional maturation.

METHODS

Thirty-four transplants were microsurgically grafted either inside a pouch created on the nude peritoneum (n = 15) or on the host stomach and esophagus (n = 19). The mucosa of transplanted tissues was analyzed by immunohistochemical techniques to detect gastric cells. Gastric cell secretions were collected before and after pentagastrin or omeprazole treatment.

RESULTS

Parietal, G, and D cells were detected immunohistochemically only after 1 month of grafting. All xenografts actively secreted acid after 1 or 2 months' transplantation at each graft site. Acid secretion was significantly stimulated by intraperitoneally injected pentagastrin (mean pH +/- SD, 3.2 +/- 0.7 vs. 2.0 +/- 0.5; n = 10, P = 0.005) and was dramatically inhibited by intragastrically administered omeprazole (2.3 +/- 0.6 vs. 6.5 +/- 0.7; n = 15, P = 0.0007) after 5 hours.

CONCLUSION

Stomach xenografts were able to develop normally. Parietal cells were physiologically mature with functional proton pumps and active gastrin receptors, as demonstrated after omeprazole and pentagastrin treatment, respectively. Because stomach xenografts matured very rapidly, it is possible that a stomach xenograft model can be used for further studies on the functional maturation of human gastric epithelial cells, as well as the factors that influence this maturation in humans.

Manipulating the host to study bacterial virulence

The ability to manipulate animal hosts as well as bacterial pathogens greatly expands the utility of in vivo models of infection. For example, the construction of mice that harbor human tissues or express specific transgenes can provide ligand-receptor interactions that are essential for pathogenesis. Interactions between virulence factors and specific host defenses can sometimes be resolved by challenging selectively immuno deficient mice with bacteria containing virulence gene mutations. Transgenic animals expressing inducible reporters can be used to conveniently identify cells in which specific response pathways have been activated during infection. These and other approaches promise to improve the quality of information obtainable from in vivo assessments of pathogenesis.

Gastric penetration of amoxicillin in a human Helicobacter pylori-infected xenograft model

The delivery of antibiotics into Helicobacter pylori-infected human stomachs is still poorly understood. Human embryonic gastric xenografts in nude mice have recently been proposed as a new model for the study of H. pylori infection. Using this model, we compared the penetration of amoxicillin, after intraperitoneal administration of a dose of 20 mg/kg of body weight, into the gastric mucosae of infected and uninfected xenografts. The concentrations of this drug in serum and superficial gastric mucosae were determined at 20 min and 1 and 3 h after injection. Ten mice with H. pylori-infected grafts (n = 5) or uninfected grafts (n = 5) were studied. Mucosal samples were obtained by cryomicrotomy. The concentrations in serum were similar to those obtained in the serum of humans after oral administration of 1 g of amoxicillin. The mean area under the tissue concentration-versus-time curve from 0 to 3 h obtained for mice with infected grafts was significantly higher than that obtained for the animals with uninfected grafts (P = 0.01). These results suggest that the penetration of amoxicillin into the superficial gastric mucosa may be substantially increased in the case of H. pylori infection. Thus, human xenografts in nude mice represent a new, well-standardized model for investigation of systemic delivery of drugs into H. pylori-infected gastric mucosa.