**2. Animal models for inflammatory bowel disease: colitis**

The use of animal models is crucial for the investigation of the processes involved in the genesis of IBD. Although the development of the disease in animals does not present all the mechanisms observed in humans, animal models still are the most effective way to study the factors involved in the pathogenesis of BD. It would be difficult to conduct such a study in humans. Additionally, the animals are very useful for the assessment of new therapeutic approaches [13].

Over time, several experimental models of IBD were developed to conduct experimental studies, particularly mice and rats. The animal models of intestinal inflammation can be divided into four groups according to the type of induction namely: genetic modification, cell transfer, spontaneous inflammation and chemical agents [14–16].

The ideal experimental model is characterized by morphological disorders and intestinal inflammation, in addition to clinical symptoms, pathophysiology and development of the disease similar or equal to human condition IBD [17]. The chapter thus presents animal models developed for the study of and experimentation on colitis.

#### **2.1. Genetic modification**

The various manifestations characterized by chronic inflammation include inflammatory bowel diseases (IBDs), such as ulcerative colitis (UC) and Crohn's diseases (CD) [4, 5]. Their clinical presentations can be overlapping as well as distinct [6, 7]. UC is generally associated to superficial inflammation of the colon mucosa and CD comprises transmural damage that

The IBDs are common among white people between the ages of 20 and 40 years old and the second peak of the disease occurs around 55 years of age. The distribution of this disease in

The genesis of UC and CD involves multiple factors, such as genetic, environmental, intestinal microbiota and the presence of enteric infections. These factors may affect the immune

The treatment of IBD is considered unsatisfactory, because among other factors, cure may not be possible, only remission of the disease and/or treatment of symptoms. Several classes of drugs are currently used to treat IBD, such as aminosalicylates, corticosteroids and immunosuppressives [11]. The odds remain that these drugs have many side effects, are expensive

Therefore, concise experimental studies are needed to unravel the etiology and pathophysiological mechanisms of IBD for development of alternative treatments and/or more effective therapeutic agents to treat patients with ulcerative colitis. Thus, the use of experimental animal models becomes essential to elucidate the mechanism(s) involved and accelerate the

The use of animal models is crucial for the investigation of the processes involved in the genesis of IBD. Although the development of the disease in animals does not present all the mechanisms observed in humans, animal models still are the most effective way to study the factors involved in the pathogenesis of BD. It would be difficult to conduct such a study in humans. Additionally, the animals are very useful for the assessment of new therapeutic

Over time, several experimental models of IBD were developed to conduct experimental studies, particularly mice and rats. The animal models of intestinal inflammation can be divided into four groups according to the type of induction namely: genetic modification, cell transfer,

The ideal experimental model is characterized by morphological disorders and intestinal inflammation, in addition to clinical symptoms, pathophysiology and development of the disease similar or equal to human condition IBD [17]. The chapter thus presents animal mod-

may occur in any segment of the gastrointestinal tract (GI) [8].

214 Experimental Animal Models of Human Diseases - An Effective Therapeutic Strategy

males and females seems similar, though CD is more frequent in women [9].

system, by expanding and perpetuating the inflammatory process [10].

**2. Animal models for inflammatory bowel disease: colitis**

and lose their efficacy after a certain period of medication [12].

development of a specific and effective therapy.

spontaneous inflammation and chemical agents [14–16].

els developed for the study of and experimentation on colitis.

approaches [13].

The development and use of genetically modified animals have contributed to the investigation of various issues related to the IBD, and the most frequent are connected to the triggering of inflammation through the impairment of various functions such as epithelial barrier and detection of bacterial components, signaling of the innate immune response, immune regulation and signaling response to stress [18]. Studies involving the human genome have shown the association of more than 160 genes connected to IBD [19] (**Table 1**).

When the intestinal epithelial barrier is impaired, the intestinal mucosa has contact with bacteria from the lumen, which generates the inflammatory responses that will lead to the development of IBD. Studies have demonstrated the relationship between CD and certain genes involved in the intestinal epithelial barrier function. Animal models that express defects in this barrier are discussed and are essential in the investigation of IBD pathogenesis [18].

#### **a.** C57BL/6 mouse expressing a dominant negative N-cadherin (NCADΔ)

N-cadherin is a glycoprotein related to epithelial cell adhesion and is essential for normal development. Mice with a dominant-negative mutation of N-cadherin developed porous regions in the intestinal epithelium and intercellular adhesion disorder, developing transmural inflammation of the jejunum similar to CD at 3 months old. The organization of the small intestinal epithelium makes it possible to use chimeric mice, generated from normal blastocyts and genetically manipulated embryonic stem cells, to study cadherin function. Therefore, embryonic stem cells were transfected with a dominant negative N-cadherin mutant (NCAD*Δ*) under the control of promoters active in small intestinal epithelial cells and then introduced into C57BL/6 mouse blastocysts [20].

#### **b.** FVB mice

FVB mice originated from Swiss syngeneic strains subjected to processes that triggered intolerance or sensitivity to histamine. FVB mice were derived from the syngeneic Swiss strains, selected from crosses in which progenies received pertussis vaccination and challenged with histamine thus developing resistance or sensitivity to it. From this experimental system, two strains were selected: one resistant to the histamine factor (HSFR/N) and another sensitive (HSFS/N). Within the latter group, in the early 1970s, a group of eight syngeneic generations, HSFS/N, carrying Fv-1b alleles and susceptible to the Friend leukemia virus, lineage B, were selected. They are good breeders with large progenies and the eggs of the FVB/N lineage favor *in vitro* fertilization procedures since it has a huge pro-nucleus that facilitates DNA microinjection and the production of transgenic [21].

#### **c.** Muc2 knockout (Muc2−/−) and Muc2 heterozygous (Muc2+/−) mice

The surface of the intestinal mucosa has many components essential for its protection, such as MUC2 that has a lubricating function and also provides a protective barrier between the contents of the lumen and mucosal layers. Wild-type (Muc2<sup>+</sup> / + ), Muc2<sup>+</sup> / − and Muc2− / − littermates are mostly used and scores recorded weekly until the age of 16 weeks to obtain a disease activity index (DAI). The previously mentioned Muc2−/− mice were backcrossed onto a 129SV


this substance forms 80% of the mucus molecular weight. Approximately 30% of the individuals with UC have disorder in O-glycan synthesis. To study the role of O-glycans in intestinal tissue, the model was generated by crossing mice with loxP sites flanking C1galt1 (C1galt1f/f mice) with an intestinal epithelium-specific Cre-expressing transgenic line (Villin-Cre mice), giving rise to animals lacking C1galt1 in the intestinal epithelium, referred to as C1galt1−/− (IEC C1galt1−/−) mice specific for intestinal epithelial cells. All the animals with deletion of C1galt1 in intestinal epithelial cells developed distal colon inflammation at 12 weeks of age. Deletion of C1galt in epithelial cells was also induced in adult animals and, 10 days later, the

Use of Animal Models in the Study of Colitis http://dx.doi.org/10.5772/intechopen.75608 217

The multiple drug resistance gene (MDR1) codes the multiple drug carrier (P-glycoprotein) in intestinal epithelial cells. Around 25% of FVB mice with the gene MDR1a "deactivated" developed colitis at 1 year of age [24]. In the Japanese population, the MDR1 gene was related to susceptibility to late onset of UC [25]. To obtain FVB.mdr1a−/− mice, FVB control mice and mdr1a−/− mice were bred and maintained in the SPF facility. Mdr 1a−/− mice had been backcrossed onto the FVB strain for at least seven generations for models obtained at Taconic

Inositol requiring enzyme 1α (IRE1 α) acts as a major stress sensor. The Villin-Cre transgenic mice expressing Cre recombinase specifically in intestinal epithelium is currently available. Floxed mice (Ire1 α flox/flox), in which the 121-nucleotide exon 2 of the Ern1 (i.e. Ire1 α) allele was flanked with two loxP recombination sites. Intestinal epithelia-specific Ire1 α knock-out mice (Ire1 α flox/flox-Villin-Cre) were produced therefore, by intercrossing the Ire1 α flox/flox mice with Villin-Cre mice. Animals without IRE1 α develop spontaneous colitis and are characterized by the loss of goblet cells, which causes the intestinal epithelial barrier to become non-

Animals with deactivation of nuclear factor-kappa B (NF-ĸβ) binding in intestinal epithelial cells, through conditional ablation of NEMO or both IKK1 (IKKa) and IKK2 (IKKb)— IKK subunits essential for NF-ĸβ activation, have an exacerbated response to luminal microbiota, which leads to the development of colitis with apoptosis of epithelial cells at the age of 6 weeks. To investigate the function of NF-ĸβ signaling in the gut epithelium *in vivo*, this was generated in mice lacking NEMO specifically in intestinal epithelial cells (NEMOIEC−KO mice) by crossing mice carrying loxP-flanked (floxed, FL) NEMO (Ikbkg) alleles with Villin-Cre transgenics. These experiments were performed using mice backcrossed into the C57BL/6 genetic background for at least five generations. They were used as wild-type controls. The mice used were housed in individually ventilated cage systems, in either specific pathogen-free or conventional animal facilities [27, 28]. Therefore, regardless of the immune system, intestinal cells clearly provide protection against bacte-

development of colitis was also observed [23].

**e.** *MDR1a−/− mice*

Farms [24].

functional [26].

**g.** *NEMOIEC−KO mice*

rial pathogens of the microbiota [18].

**f.** *Ire1 α flox/flox-Villin-Cre mice*

**Table 1.** Genetic models of colitis.

(Charles River, Maastricht, The Netherlands) genetic background for nine generations followed by intercrosses to breed animals homozygous for the Muc2 disruption. Mice lacking this component may develop IBD in the distal colon at approximately 5 weeks of age [22].

#### **d.** *Intestinal epithelial cell-specific C1galt1−/− (IEC C1galt1−/−) mice*

The enzyme β1, 3-galactosyltransferase 1 (C1galt1) is related to the synthesis of O-glycan in mucus-producing epithelial cells. The mucus transports a large amount of O-glycan, since this substance forms 80% of the mucus molecular weight. Approximately 30% of the individuals with UC have disorder in O-glycan synthesis. To study the role of O-glycans in intestinal tissue, the model was generated by crossing mice with loxP sites flanking C1galt1 (C1galt1f/f mice) with an intestinal epithelium-specific Cre-expressing transgenic line (Villin-Cre mice), giving rise to animals lacking C1galt1 in the intestinal epithelium, referred to as C1galt1−/− (IEC C1galt1−/−) mice specific for intestinal epithelial cells. All the animals with deletion of C1galt1 in intestinal epithelial cells developed distal colon inflammation at 12 weeks of age. Deletion of C1galt in epithelial cells was also induced in adult animals and, 10 days later, the development of colitis was also observed [23].

#### **e.** *MDR1a−/− mice*

The multiple drug resistance gene (MDR1) codes the multiple drug carrier (P-glycoprotein) in intestinal epithelial cells. Around 25% of FVB mice with the gene MDR1a "deactivated" developed colitis at 1 year of age [24]. In the Japanese population, the MDR1 gene was related to susceptibility to late onset of UC [25]. To obtain FVB.mdr1a−/− mice, FVB control mice and mdr1a−/− mice were bred and maintained in the SPF facility. Mdr 1a−/− mice had been backcrossed onto the FVB strain for at least seven generations for models obtained at Taconic Farms [24].

#### **f.** *Ire1 α flox/flox-Villin-Cre mice*

Inositol requiring enzyme 1α (IRE1 α) acts as a major stress sensor. The Villin-Cre transgenic mice expressing Cre recombinase specifically in intestinal epithelium is currently available. Floxed mice (Ire1 α flox/flox), in which the 121-nucleotide exon 2 of the Ern1 (i.e. Ire1 α) allele was flanked with two loxP recombination sites. Intestinal epithelia-specific Ire1 α knock-out mice (Ire1 α flox/flox-Villin-Cre) were produced therefore, by intercrossing the Ire1 α flox/flox mice with Villin-Cre mice. Animals without IRE1 α develop spontaneous colitis and are characterized by the loss of goblet cells, which causes the intestinal epithelial barrier to become nonfunctional [26].

#### **g.** *NEMOIEC−KO mice*

(Charles River, Maastricht, The Netherlands) genetic background for nine generations followed by intercrosses to breed animals homozygous for the Muc2 disruption. Mice lacking this component may develop IBD in the distal colon at approximately 5 weeks of age [22].

**Mutation Main results References**

epithelial cells

gastrointestinal tract

disorders; spontaneous colitis

and colitis

colitis

Absence of TCR α Spontaneous triggering of colitis [40] Absence of STAT3 in macrophages and neutrophils Spontaneous onset of colitis [41]

Absence of Gαi2 Triggering of colitis and colorectal cancer [44–46]

Absence of T-bet and T and B cells Onset of colitis similar to UC [48] Altered levels of TNF-α Development of inflammation of the ileum and

Super expression of IL-7 Spontaneous onset of colitis [53] Absence of Gpx1 and Gpx2 Triggering of colitis and ileitis [54] Specific deletion of XBP1 factor Development of ileitis [55]

organs

in the distal colon

Absence of enzyme A20 Inflammation in the intestine and in other

Lack of Muc2 Development of IBD in the distal colon [22] Specific deletion of C1galt1 in epithelial cells Inflammation in the distal colon [23] MDR1a gene deleted Development of colitis [24] Absence of IRE1 α Spontaneous colitis [26]

similar to that of patients with CD

Development of colitis with apoptosis of

Spontaneous inflammation in several organs

Autoimmune disease with colitis and other

Spontaneous development of colitis; chronic

Development of transmural colitis [43]

[20]

[27, 28]

[29, 30]

[32–34]

[38, 39]

[47]

[49–51]

[31]

Dominant-negative mutant N-cadherin Transmural inflammation in the jejunum

216 Experimental Animal Models of Human Diseases - An Effective Therapeutic Strategy

Absence of SMAD4 Inflammation through the entire

Nuclear kappa B (NF-kB) deactivated in intestinal

Specific deletion of type II receptor for TGB-β in CD4+-specific T cells and dendritic cells

Absence of IL-2 and deficiency of JAK 3

Absence of IL-10 and deletion of CRF2-4

Super expression of STAT4 and immunization with

(component of IL receptor)

(component of IL-10 receptor)

**Table 1.** Genetic models of colitis.

DNP-KLH/CFA

epithelial cells

The enzyme β1, 3-galactosyltransferase 1 (C1galt1) is related to the synthesis of O-glycan in mucus-producing epithelial cells. The mucus transports a large amount of O-glycan, since

**d.** *Intestinal epithelial cell-specific C1galt1−/− (IEC C1galt1−/−) mice*

Animals with deactivation of nuclear factor-kappa B (NF-ĸβ) binding in intestinal epithelial cells, through conditional ablation of NEMO or both IKK1 (IKKa) and IKK2 (IKKb)— IKK subunits essential for NF-ĸβ activation, have an exacerbated response to luminal microbiota, which leads to the development of colitis with apoptosis of epithelial cells at the age of 6 weeks. To investigate the function of NF-ĸβ signaling in the gut epithelium *in vivo*, this was generated in mice lacking NEMO specifically in intestinal epithelial cells (NEMOIEC−KO mice) by crossing mice carrying loxP-flanked (floxed, FL) NEMO (Ikbkg) alleles with Villin-Cre transgenics. These experiments were performed using mice backcrossed into the C57BL/6 genetic background for at least five generations. They were used as wild-type controls. The mice used were housed in individually ventilated cage systems, in either specific pathogen-free or conventional animal facilities [27, 28]. Therefore, regardless of the immune system, intestinal cells clearly provide protection against bacterial pathogens of the microbiota [18].

#### *2.1.1. Transgenic animal models expressing colitis through modulation of immune regulatory agents*

Mice with several genetic disorders associated with immune regulation were examined, revealing the development of colitis that was related to different substances [18]. These models with genetic modifications that affect immune regulation and trigger IBD are discussed below.

Similarly, IL-10 is a regulatory cytokine with IBD susceptibility genes not only in adults but also in children [35–37]. IL-10 deficient mice develop spontaneous colitis [38]. Mice with deleted CRF2-4, a component of the IL-10 receptor, develop splenomegaly and disorders such

Use of Animal Models in the Study of Colitis http://dx.doi.org/10.5772/intechopen.75608 219

The T cell receptor (TCR) is essential for the recognition of antigens by T cells. Approximately 60% of mice without TCR α, TCR component, developed Th2-mediated spontaneous colitis. The animals used in this study were produced by crossing TCR β × mutant mice with TCR mutant mice, and generated TCR β × gamma double mutant mice, which are deficient both in αβ and γ cells. By mutating, the recombination-activating gene RAG-1 mice totally deficient

The transcription factor, signal transducer and activator of transcription 3 (STAT3) acts in the control of various innate immune responses such as differentiation of Th17 cells and epithelial renovation. Its gene is susceptible to UC and CD [35, 36]. Animals with intestinal epithelial cells deficient in STAT3 developed spontaneous colitis. In response to inflammatory stimuli, LysMcre/Statflox/− mice develop enterocolitis even though they produce more IL-10 than normal animals in the same condition. To disrupt the Stat3 gene specifically in macrophages and neutrophils, two types of animals were crossed, mice in which the Stat3 gene is flanked by two loxP sites (Stat3flox/flox) and the other mouse in which the Cre cDNA is inserted into the

STAT4 is a transcription signal transducer and activator factor that acts in the development of Th1 cells. Its gene was considered susceptible to UC in individuals with white skin [42]. Transgenic mice with super expression of STAT4 when immunized with 2,4- dinitrophenolkeyhole limpet hemocyanin/Complete Freund's Adjuvant (DNP-KLH/CFA) to activate the cytomegalovirus (CMV) developed transmural colitis. The murine STAT-4 cDNA was cloned downstream of the CMV promoter into the pcDNA3.1 expression vector (Invitrogen, San Diego, CA) yielding the pcDNA3.1S4 vector. A 3.6-kp *NruI/PvuII* fragment of pcDNA3.1S4 containing the STAT-4 expression cassette was microinjected into pronuclei of fertilized eggs of FVB/NHSD mice. Mice were maintained under specific pathogen-free conditions in iso-

Gαi2 signal transduction proteins participate in a wide signaling system. Mice that lack Gαi2 proteins showed dysfunctions related to T cells and developed colitis when they were 3–4 weeks old and colorectal cancer at approximately 3–4 months of age. Gαi2-deficient (Gαi2−/−) mice on a 129SvEv X C57BL/6 background (backcrossed four or five generations into 129SvEv and then intercrossed) and on a pure 129SvEv background were used [44–46].

A20 is an enzyme related to ubiquitin, which in turn is associated to NF-ĸβ1 activation. It acts in the prevention of tissue destruction and inflammation mediated by innate immune cells, in addition to regulating skin differentiation. To study the functions of A20 *in vivo*, A20-deficient

as chronic colitis [39].

lated cages [43].

**d.** Gαi2−/− mice

**e.** A20−/−mice

**c.** Mice with T cell-related mutations

in mature T and B lymphocytes were produced [40].

lysozyme M gene by a knock-in approach (LysMcre mice) [41].

#### **a.** Type II receptor for TGF-β or SMAD4 absence

The transforming growth factor-beta 1 (TGF-β1) acts both in immune regulation and in the differentiation of regulatory T cells. Transgenic animals with dominant-negative mutant TGF-β type II receptor in specific CD4+ T cells showed spontaneous inflammation at around 3–4 months of age, and there was increased expression of Th1 and Th2 cytokines in several body organs such as colon, liver, stomach, duodenum, pancreas and kidney. These animals were created by using DNA microinjection into (C57BL/6xC3H) F1 fertilized oocytes, which results in six transgene-positive mice. All pups in the experimental cycle appeared normal at 2 weeks of age, but three died between 2 and 4 weeks of age. Three remaining transgenepositive mice appeared healthy and were bred; their progeny was further used to identify transgenic lines expressing a functional dominant-negative TGF-β receptor type II [29].

Animals with specific deletion of type II receptor for TGF-β in typical dendritic cells developed several inflammations, including colitis. Thus, B6.129S6-Tgfbr2tm1hlm mice, carrying homozygous loxP site insertion flanking exon 2 of Tgfbr2 gene is currently available and obtainable from the National Cancer Institute (Frederick, MD) mouse repository (strain 01XN5) and other laboratories. CD11c-Cre transgenic mice (B6.Cg-Tg(Itgax-cre)1-1Reiz/J), OT-II transgenic mice (B6.Cg-Tg(TcraTcrb)425Cbn/J), Rag1−/− (B6.129S7-Rag1tm1Mom/J) and wild-type C57BL/6 J are all obtainable by researchers. The mouse model with CD-specific T*gfbr2* deletion highlights the critical importance of TGF-β signaling in CDs in the maintenance of immune homeostasis and in the prevention of autoimmunity [30].

SMAD4 acts as a mediator in intracellular signaling of TGF-β. To inactivate specifically Smad4 in T cells, it was necessary to cross mice with a transgene encoding a Cre-recombinase driven by the Lck promoter (Smad4co/co; Lck-Cre) or the CD4 promoter (Smad4co/co; CD4-Cre) with the strain carrying the Smad4 conditional allele (Smad4co/co). Mice without SMAD4 in specific T cells and those without SMAD4 in CD4+ T cells had inflammation through the entire gastrointestinal tract at 3 months of age [31].

**b.** Mutations affecting the interleukin receptor (IL-2)

Interleukin-2 (IL-2) is related to activated-induced cell death and to the triggering of regulatory T cells function. Deficient IL-2 mice develop spontaneous autoimmune colitis, gastritis, hepatitis, pneumonia, pancreatitis, nephritis and hemolytic anemia [32]. Janus tyrosine kinase 3 (JAK 3) acts as a transducer of interleukin-2 receptor common gamma chain. Deficiency of JAK 3 led to the spontaneous development of colitis in mice [33]. The animal model that uses IL-2 is characterized by association of colitis with the autoimmune mechanism, which was demonstrated in the spontaneous onset of colitis without the presence of microorganisms [34].

Similarly, IL-10 is a regulatory cytokine with IBD susceptibility genes not only in adults but also in children [35–37]. IL-10 deficient mice develop spontaneous colitis [38]. Mice with deleted CRF2-4, a component of the IL-10 receptor, develop splenomegaly and disorders such as chronic colitis [39].

**c.** Mice with T cell-related mutations

*2.1.1. Transgenic animal models expressing colitis through modulation of immune regulatory* 

**a.** Type II receptor for TGF-β or SMAD4 absence

218 Experimental Animal Models of Human Diseases - An Effective Therapeutic Strategy

Mice with several genetic disorders associated with immune regulation were examined, revealing the development of colitis that was related to different substances [18]. These models with genetic modifications that affect immune regulation and trigger IBD are discussed below.

The transforming growth factor-beta 1 (TGF-β1) acts both in immune regulation and in the differentiation of regulatory T cells. Transgenic animals with dominant-negative mutant TGF-β type II receptor in specific CD4+ T cells showed spontaneous inflammation at around 3–4 months of age, and there was increased expression of Th1 and Th2 cytokines in several body organs such as colon, liver, stomach, duodenum, pancreas and kidney. These animals were created by using DNA microinjection into (C57BL/6xC3H) F1 fertilized oocytes, which results in six transgene-positive mice. All pups in the experimental cycle appeared normal at 2 weeks of age, but three died between 2 and 4 weeks of age. Three remaining transgenepositive mice appeared healthy and were bred; their progeny was further used to identify transgenic lines expressing a functional dominant-negative TGF-β receptor type II [29].

Animals with specific deletion of type II receptor for TGF-β in typical dendritic cells developed several inflammations, including colitis. Thus, B6.129S6-Tgfbr2tm1hlm mice, carrying homozygous loxP site insertion flanking exon 2 of Tgfbr2 gene is currently available and obtainable from the National Cancer Institute (Frederick, MD) mouse repository (strain 01XN5) and other laboratories. CD11c-Cre transgenic mice (B6.Cg-Tg(Itgax-cre)1-1Reiz/J), OT-II transgenic mice (B6.Cg-Tg(TcraTcrb)425Cbn/J), Rag1−/− (B6.129S7-Rag1tm1Mom/J) and wild-type C57BL/6 J are all obtainable by researchers. The mouse model with CD-specific T*gfbr2* deletion highlights the critical importance of TGF-β signaling in CDs in the mainte-

SMAD4 acts as a mediator in intracellular signaling of TGF-β. To inactivate specifically Smad4 in T cells, it was necessary to cross mice with a transgene encoding a Cre-recombinase driven by the Lck promoter (Smad4co/co; Lck-Cre) or the CD4 promoter (Smad4co/co; CD4-Cre) with the strain carrying the Smad4 conditional allele (Smad4co/co). Mice without SMAD4 in specific T cells and those without SMAD4 in CD4+ T cells had inflammation

Interleukin-2 (IL-2) is related to activated-induced cell death and to the triggering of regulatory T cells function. Deficient IL-2 mice develop spontaneous autoimmune colitis, gastritis, hepatitis, pneumonia, pancreatitis, nephritis and hemolytic anemia [32]. Janus tyrosine kinase 3 (JAK 3) acts as a transducer of interleukin-2 receptor common gamma chain. Deficiency of JAK 3 led to the spontaneous development of colitis in mice [33]. The animal model that uses IL-2 is characterized by association of colitis with the autoimmune mechanism, which was demonstrated in the spontaneous onset of colitis without the presence of

nance of immune homeostasis and in the prevention of autoimmunity [30].

through the entire gastrointestinal tract at 3 months of age [31].

**b.** Mutations affecting the interleukin receptor (IL-2)

microorganisms [34].

*agents*

The T cell receptor (TCR) is essential for the recognition of antigens by T cells. Approximately 60% of mice without TCR α, TCR component, developed Th2-mediated spontaneous colitis. The animals used in this study were produced by crossing TCR β × mutant mice with TCR mutant mice, and generated TCR β × gamma double mutant mice, which are deficient both in αβ and γ cells. By mutating, the recombination-activating gene RAG-1 mice totally deficient in mature T and B lymphocytes were produced [40].

The transcription factor, signal transducer and activator of transcription 3 (STAT3) acts in the control of various innate immune responses such as differentiation of Th17 cells and epithelial renovation. Its gene is susceptible to UC and CD [35, 36]. Animals with intestinal epithelial cells deficient in STAT3 developed spontaneous colitis. In response to inflammatory stimuli, LysMcre/Statflox/− mice develop enterocolitis even though they produce more IL-10 than normal animals in the same condition. To disrupt the Stat3 gene specifically in macrophages and neutrophils, two types of animals were crossed, mice in which the Stat3 gene is flanked by two loxP sites (Stat3flox/flox) and the other mouse in which the Cre cDNA is inserted into the lysozyme M gene by a knock-in approach (LysMcre mice) [41].

STAT4 is a transcription signal transducer and activator factor that acts in the development of Th1 cells. Its gene was considered susceptible to UC in individuals with white skin [42]. Transgenic mice with super expression of STAT4 when immunized with 2,4- dinitrophenolkeyhole limpet hemocyanin/Complete Freund's Adjuvant (DNP-KLH/CFA) to activate the cytomegalovirus (CMV) developed transmural colitis. The murine STAT-4 cDNA was cloned downstream of the CMV promoter into the pcDNA3.1 expression vector (Invitrogen, San Diego, CA) yielding the pcDNA3.1S4 vector. A 3.6-kp *NruI/PvuII* fragment of pcDNA3.1S4 containing the STAT-4 expression cassette was microinjected into pronuclei of fertilized eggs of FVB/NHSD mice. Mice were maintained under specific pathogen-free conditions in isolated cages [43].

#### **d.** Gαi2−/− mice

Gαi2 signal transduction proteins participate in a wide signaling system. Mice that lack Gαi2 proteins showed dysfunctions related to T cells and developed colitis when they were 3–4 weeks old and colorectal cancer at approximately 3–4 months of age. Gαi2-deficient (Gαi2−/−) mice on a 129SvEv X C57BL/6 background (backcrossed four or five generations into 129SvEv and then intercrossed) and on a pure 129SvEv background were used [44–46].

#### **e.** A20−/−mice

A20 is an enzyme related to ubiquitin, which in turn is associated to NF-ĸβ1 activation. It acts in the prevention of tissue destruction and inflammation mediated by innate immune cells, in addition to regulating skin differentiation. To study the functions of A20 *in vivo*, A20-deficient (A20−/−) was generated by gene targeting. Rodents that lack this enzyme developed inflammation in various organs, including bowel, when they were 3–6 weeks olds [47].

selenium-dependent and can reduce a broad range of hydroperoxides. The inflammatory process is associated with increased lipid peroxidation, and hydroperoxide appears to mediate IBD-related symptoms. To clarify the role of GPX in the intestinal epithelial cells, a homozygous double-KO mice with interruption in the expression of Gpx1 and Gpx2 genes was generated. These animals have signs and symptoms related to inflammatory bowel disease. The Ye-Shih Ho (Wayne State University, Detroit, MI) generated Gpx1-KO mice, as C57BL/6 J and 129Sv/J hybrids. Likewise, the generation of Gpx2-KO mice as B6 and 129S3 hybrids occurred at the City of Hope (COH; Duarte, CA) Transgenic Mouse Core. These mice were housed at the COH Animal Resources Center in ventilated cage racks. So, it was possible to verify that mice deficient in Gpx1 and GPX2 developed spontaneous colitis and ileitis GPX2 at about

Use of Animal Models in the Study of Colitis http://dx.doi.org/10.5772/intechopen.75608 221

The transcription factor XBP1 is involved in the response to ER stress. XBP1 was related to CD and UC. To understand the function of this factor, Xbp1 exon 2 was almost completely disrupted in the intestinal tissue (small intestine and colon). Mice with specific deletion of this factor in intestinal epithelial cells developed spontaneous ileitis due to the lack of Paneth cells

The referred methodology induces intestinal inflammation through selective transfer of certain types of immune cells in animals with impaired immune systems (RAG-1 knockout and RAG-2 knockout and SCID pigs). The study based on these models allows the investigation of immune factors, particularly the role of pathogenic T cells and T cell-mediated colitis on

The transfer of T CD4+ cells with high levels of protein CD45RB to mice deficient in T cells (RAG−/− or SCID) is the transfer methodology most commonly used to induce colitis, and it increases intestinal inflammation approximately 5–10 weeks after the transfer [56–58]. This method causes an inflammation similar to that of models that use chemical agents and is characterized by hyperplasia and inflammation in the colon, generally causing the death of

**Models Main results References**

**SheLAg-specific CD4+ T cells** Colitis caused by one single bacterial antigen [62]

regardless of the animal's microbiota

[56–61]

[63]

**CD4 + CD45RBhi** Intestinal inflammation with Th1 responses to antigens of bacteria in the lumen

**Hsp60-specific CD8+ T cells** Severe inflammation in the mucosa of the small intestine,

**Table 2.** Adoptive transfer models of intestinal inflammation.

3 weeks of age [54].

that secrete protective cells [55].

**2.2. Adoptive transfer model of colitis**

mucosal inflammation [18] (**Table 2**).

**a.** CD4+ CD45RBhi model

the animal [59].

#### **f.** T-bet−/− mice

T-bet is a transcription factor that regulates the differentiation of T cells into Th1 cells. To investigate whether the T-bet's protective function is linked to innate immunity, the T-bet−/− mouse developed on the RAG2−/− background was examined. The mice experimental model that lacked the T-bet factor showed no colitis. On the other hand, a new mouse model through which animals without T-bet were crossed with RAG2 mice lacking T and B cells showed the development of colitis similar to what occurs in UC at 4 weeks of age, therefore, T-bet expression protects against colitis and T-bet−/− × RAG2−/− mice develop spontaneous colitis [48].

#### **g.** TNF ΔARE mice

TNF-α is related to the onset of CD, because of the development of spontaneous inflammation in the ileum of mice with increased TNF-α activity [49]. Animals with intrinsic defect related to post-transcriptional regulation of TNF mRNA (TNF ΔARE rat model) developed inflammation, especially in the terminal ileum and subsequently in the proximal colon [50, 51]. To develop TNFΔARE mice, a 69bp deletion encompassing TNF ARE was conducted in embryonic stem cells in conjunction with the neomycin resistance marker (neo) flanked by loxP sequences. The excision of the neon gene and generation of TNFΔARE rat lines was due to the transient expression of the Cre recombinase in fertilized oocytes from the previously mentioned mice. The TNFΔARE homozygous mice developed early pathologies and also had a short shelf life. To reverse this problem, the effects of the TNFΔARE mutation on TNF biosynthesis were investigated in TNFΔARE/− hemizygous mice generated by the crossing of TNFΔARE/+ to TNFΔARE/− mice. The use of hemizygous TNFΔARE/− mice made it possible to investigate the regulatory role of the ARE element in a monoallelic system without the interference of a wild type TNF allele in the generation of TNF. So, a defective function of ARE may be etiopathogenic for the development of analogous human pathologies, in this case, Crohn's-like inflammatory bowel disease.

#### **h.** SRα/IL-7 mice

IL-7 has an important role in the homeostasis of T cells, and the gene linked to the IL-7 receptor was related to UC [35, 36]. To study the IL-7 role, it was critical to develop the model SRα/ IL-7 transgenic mice using 2.1 kb SRα/lL-7 DNA fragment that was linearized by AatH and ApaU digestion. Microinjection into the pronuclei of fertilized eggs of C57BL/6 J mice was performed with ~10<sup>3</sup> copies of the SRα/lL-7 DNA fragment according to the standard procedure [52]. Rodents with super expression of IL-7 developed spontaneous colitis at about 4–12 weeks of age [53].

**i.** Double-KO mice deficient in both Gpx1 and Gpx2 gene expression

Activation of endoplasmic reticulum (ER) stress responses of intestinal epithelial cells to the metabolic by products of bacteria in the intestinal lumen is necessary for intestinal homeostasis and prevention of chronic inflammation [18]. The glutathione peroxidase (GPX) enzyme is selenium-dependent and can reduce a broad range of hydroperoxides. The inflammatory process is associated with increased lipid peroxidation, and hydroperoxide appears to mediate IBD-related symptoms. To clarify the role of GPX in the intestinal epithelial cells, a homozygous double-KO mice with interruption in the expression of Gpx1 and Gpx2 genes was generated. These animals have signs and symptoms related to inflammatory bowel disease. The Ye-Shih Ho (Wayne State University, Detroit, MI) generated Gpx1-KO mice, as C57BL/6 J and 129Sv/J hybrids. Likewise, the generation of Gpx2-KO mice as B6 and 129S3 hybrids occurred at the City of Hope (COH; Duarte, CA) Transgenic Mouse Core. These mice were housed at the COH Animal Resources Center in ventilated cage racks. So, it was possible to verify that mice deficient in Gpx1 and GPX2 developed spontaneous colitis and ileitis GPX2 at about 3 weeks of age [54].

The transcription factor XBP1 is involved in the response to ER stress. XBP1 was related to CD and UC. To understand the function of this factor, Xbp1 exon 2 was almost completely disrupted in the intestinal tissue (small intestine and colon). Mice with specific deletion of this factor in intestinal epithelial cells developed spontaneous ileitis due to the lack of Paneth cells that secrete protective cells [55].

#### **2.2. Adoptive transfer model of colitis**

The referred methodology induces intestinal inflammation through selective transfer of certain types of immune cells in animals with impaired immune systems (RAG-1 knockout and RAG-2 knockout and SCID pigs). The study based on these models allows the investigation of immune factors, particularly the role of pathogenic T cells and T cell-mediated colitis on mucosal inflammation [18] (**Table 2**).

#### **a.** CD4+ CD45RBhi model

(A20−/−) was generated by gene targeting. Rodents that lack this enzyme developed inflamma-

T-bet is a transcription factor that regulates the differentiation of T cells into Th1 cells. To investigate whether the T-bet's protective function is linked to innate immunity, the T-bet−/− mouse developed on the RAG2−/− background was examined. The mice experimental model that lacked the T-bet factor showed no colitis. On the other hand, a new mouse model through which animals without T-bet were crossed with RAG2 mice lacking T and B cells showed the development of colitis similar to what occurs in UC at 4 weeks of age, therefore, T-bet expression protects against colitis and T-bet−/− × RAG2−/− mice develop spontaneous colitis [48].

TNF-α is related to the onset of CD, because of the development of spontaneous inflammation in the ileum of mice with increased TNF-α activity [49]. Animals with intrinsic defect related to post-transcriptional regulation of TNF mRNA (TNF ΔARE rat model) developed inflammation, especially in the terminal ileum and subsequently in the proximal colon [50, 51]. To develop TNFΔARE mice, a 69bp deletion encompassing TNF ARE was conducted in embryonic stem cells in conjunction with the neomycin resistance marker (neo) flanked by loxP sequences. The excision of the neon gene and generation of TNFΔARE rat lines was due to the transient expression of the Cre recombinase in fertilized oocytes from the previously mentioned mice. The TNFΔARE homozygous mice developed early pathologies and also had a short shelf life. To reverse this problem, the effects of the TNFΔARE mutation on TNF biosynthesis were investigated in TNFΔARE/− hemizygous mice generated by the crossing of TNFΔARE/+ to TNFΔARE/− mice. The use of hemizygous TNFΔARE/− mice made it possible to investigate the regulatory role of the ARE element in a monoallelic system without the interference of a wild type TNF allele in the generation of TNF. So, a defective function of ARE may be etiopathogenic for the development of analogous human pathologies, in this

IL-7 has an important role in the homeostasis of T cells, and the gene linked to the IL-7 receptor was related to UC [35, 36]. To study the IL-7 role, it was critical to develop the model SRα/ IL-7 transgenic mice using 2.1 kb SRα/lL-7 DNA fragment that was linearized by AatH and ApaU digestion. Microinjection into the pronuclei of fertilized eggs of C57BL/6 J mice was

cedure [52]. Rodents with super expression of IL-7 developed spontaneous colitis at about

Activation of endoplasmic reticulum (ER) stress responses of intestinal epithelial cells to the metabolic by products of bacteria in the intestinal lumen is necessary for intestinal homeostasis and prevention of chronic inflammation [18]. The glutathione peroxidase (GPX) enzyme is

**i.** Double-KO mice deficient in both Gpx1 and Gpx2 gene expression

copies of the SRα/lL-7 DNA fragment according to the standard pro-

tion in various organs, including bowel, when they were 3–6 weeks olds [47].

220 Experimental Animal Models of Human Diseases - An Effective Therapeutic Strategy

**f.** T-bet−/− mice

**g.** TNF ΔARE mice

**h.** SRα/IL-7 mice

performed with ~10<sup>3</sup>

4–12 weeks of age [53].

case, Crohn's-like inflammatory bowel disease.

The transfer of T CD4+ cells with high levels of protein CD45RB to mice deficient in T cells (RAG−/− or SCID) is the transfer methodology most commonly used to induce colitis, and it increases intestinal inflammation approximately 5–10 weeks after the transfer [56–58]. This method causes an inflammation similar to that of models that use chemical agents and is characterized by hyperplasia and inflammation in the colon, generally causing the death of the animal [59].


**Table 2.** Adoptive transfer models of intestinal inflammation.

This model of cell transfer triggers Th1 responses to bacteria in the lumen [60]. After cell transfer, naive T cells react to antigens of the luminal bacteria and expand rapidly in the lymph nodes and colon mucosa, becoming oligoclonal. The presence of pathogenic effector Th1 cells was possible due to the absence of regulatory T cells [18, 61].

The wounds observed in this mouse model occur in the ileocecal region and the colon. Clinical manifestations begin at 3–4 weeks of age and last up to 10–12 weeks of age, approximately. The characteristics of the colitis developed by this methodology are similar to those of CD

Use of Animal Models in the Study of Colitis http://dx.doi.org/10.5772/intechopen.75608 223

Investigation of the mechanisms of CD can be based on the model that uses SAMP1/YitFc mice, where there is spontaneous and/or severe inflammation of the terminal segment of the ileum, which is the primary site of the wounds in CD, this disease model in animals also resembles human CD with regard to histologic features [15, 70, 71]. For the purposes of these experiments, a colony of SAMP1/Yit mice in a barrier facility at the University of Virginia was established from animals provided by Yakult Central Institute for Microbiological Research (Tokyo, Japan). The SAMP1/Yit (H-2k) mouse strain was originally derived from AKR mice (original parents purchased from The Jackson Laboratories, Bar Harbor, Maine, USA) [70]. The findings from the adoptive transfer research have made it possible to infer that CD4+ T cells that generate a Th1-like cytokine profile, for example, IFN-γ and TNF, act as mediators of intestinal inflammation observed in SAMP1/

Experimental models of colitis induced by chemical agents are used in the analysis of pathological mechanisms of IBD as well as the development of therapeutic agents. The referred method facilitates the induction of colitis. Some chemicals, such as dextran sodium sulfate (DSS) and trinitrobenzene sulfonic acid (TNBS) are the most commonly used substances. Models with such agents have been used for more than 20 years for the investigation and

Induction of inflammation by chemical agents can cause disorders in the barrier of the intestinal mucosa and/or cause hapten-induced hypersensitivity reactions [18]. Several factors are related to the magnitude of the onset of colitis in models induced by chemical substances. Although these models do not have the complexity of human IBD, they can contribute to the

**Models Main results References**

**TBNS** Transmural colitis that resembles CD [80–82]

**Oxazolone** Inflammation of the distal colon with clinical similarities to UC [74]

[73, 74]

[80]

**2.4. Chemically induced models of intestinal inflammation**

circumstances that affect the development of IBD [16] (**Table 4**).

study of the processes involved in the control of the disease [72].

characteristics are similar to UC in humans

to CD

**Table 4.** Chemically induced models of intestinal inflammation.

**DSS** Diarrhea with bleeding, ulcerations and infiltration of granulocytes. Some

**DNBS** Extensive tissue damage and acute inflammatory process similar characteristics

[17, 69].

Yit mice.

**b.** SAMP1/YitFc model

**b.** SheLAg-specific CD4+ T cells

H. hepaticus Ag (SHelAg)-specific CD4+ Th1 clones transfer the disease to RAG1 knockout mice deficient in T cells and infected with a pathogenic bacterium (H. hepaticus) causing colitis between 7 and 8 weeks after the transfer, while the non-infected receptors did not develop colitis. It is inferred, therefore, that pathogenic T cells that respond to a single bacterial antigen may lead to the development of colitis [62].

**c.** Hsp60-specific CD8+ T cells

In general, heat shock proteins (HSP) are antigens considered potential targets to autoimmune disease. Then, the transfer of CD8+ T cells responsive to HSP60 for immunodeficient animals can trigger severe inflammation in the mucosa of the small intestine regardless of the animal's microbiota [63].

The severity of inflammation by adoptive transfer depends on the donor animal, as well as to the recipient [64, 65]. A study aimed to protocol standardization found that Balb/SCID mice develop a more severe and faster type of colitis C57BL/6 RAG-1−/− mice [66].

#### **2.3. Models of spontaneous colitis**

These models concern both the animals that develop spontaneous inflammation in the mucosa and those with inadequate mucosal immune response due to defect or genetic modification [56]. Spontaneous models are of great interest for the study of intestinal inflammation since, as in disease in humans, there is no external manipulation. The murine model C3H/HeJBir, for example, is characterized by chronic inflammation in the colon and in the cecal region [67] (**Table 3**).

#### **a.** C3H/HeJBir mouse model

Because of the occurrence of soft, light-colored feces and/or secondary perianal ulceration, and histological evidence of colitis, without pathogens, mice of the C3H/HeJ strain are likely to have a genetic predisposition to develop a form of IBD, with perianal ulceration, it has the pedigree to generate a "high-susceptibility" substrain, C3H/HeJBir, with a high incidence of spontaneous colitis [68].


**Table 3.** Models of spontaneous colitis.

The wounds observed in this mouse model occur in the ileocecal region and the colon. Clinical manifestations begin at 3–4 weeks of age and last up to 10–12 weeks of age, approximately. The characteristics of the colitis developed by this methodology are similar to those of CD [17, 69].

### **b.** SAMP1/YitFc model

This model of cell transfer triggers Th1 responses to bacteria in the lumen [60]. After cell transfer, naive T cells react to antigens of the luminal bacteria and expand rapidly in the lymph nodes and colon mucosa, becoming oligoclonal. The presence of pathogenic effector Th1 cells

H. hepaticus Ag (SHelAg)-specific CD4+ Th1 clones transfer the disease to RAG1 knockout mice deficient in T cells and infected with a pathogenic bacterium (H. hepaticus) causing colitis between 7 and 8 weeks after the transfer, while the non-infected receptors did not develop colitis. It is inferred, therefore, that pathogenic T cells that respond to a single bacterial anti-

In general, heat shock proteins (HSP) are antigens considered potential targets to autoimmune disease. Then, the transfer of CD8+ T cells responsive to HSP60 for immunodeficient animals can trigger severe inflammation in the mucosa of the small intestine regardless of the

The severity of inflammation by adoptive transfer depends on the donor animal, as well as to the recipient [64, 65]. A study aimed to protocol standardization found that Balb/SCID mice

These models concern both the animals that develop spontaneous inflammation in the mucosa and those with inadequate mucosal immune response due to defect or genetic modification [56]. Spontaneous models are of great interest for the study of intestinal inflammation since, as in disease in humans, there is no external manipulation. The murine model C3H/HeJBir, for example, is characterized by chronic inflammation in the colon and in the cecal region [67] (**Table 3**).

Because of the occurrence of soft, light-colored feces and/or secondary perianal ulceration, and histological evidence of colitis, without pathogens, mice of the C3H/HeJ strain are likely to have a genetic predisposition to develop a form of IBD, with perianal ulceration, it has the pedigree to generate a "high-susceptibility" substrain, C3H/HeJBir, with a high incidence of

**Models Main results References C3H/HeJBir** Chronic inflammation in the colon and cecal region similar to CD [67, 69] **SAMP1/YitFc** Severe inflammation in the terminal ileum, similar to CD [70, 71]

develop a more severe and faster type of colitis C57BL/6 RAG-1−/− mice [66].

was possible due to the absence of regulatory T cells [18, 61].

222 Experimental Animal Models of Human Diseases - An Effective Therapeutic Strategy

**b.** SheLAg-specific CD4+ T cells

**c.** Hsp60-specific CD8+ T cells

**2.3. Models of spontaneous colitis**

**a.** C3H/HeJBir mouse model

spontaneous colitis [68].

**Table 3.** Models of spontaneous colitis.

animal's microbiota [63].

gen may lead to the development of colitis [62].

Investigation of the mechanisms of CD can be based on the model that uses SAMP1/YitFc mice, where there is spontaneous and/or severe inflammation of the terminal segment of the ileum, which is the primary site of the wounds in CD, this disease model in animals also resembles human CD with regard to histologic features [15, 70, 71]. For the purposes of these experiments, a colony of SAMP1/Yit mice in a barrier facility at the University of Virginia was established from animals provided by Yakult Central Institute for Microbiological Research (Tokyo, Japan). The SAMP1/Yit (H-2k) mouse strain was originally derived from AKR mice (original parents purchased from The Jackson Laboratories, Bar Harbor, Maine, USA) [70]. The findings from the adoptive transfer research have made it possible to infer that CD4+ T cells that generate a Th1-like cytokine profile, for example, IFN-γ and TNF, act as mediators of intestinal inflammation observed in SAMP1/ Yit mice.

#### **2.4. Chemically induced models of intestinal inflammation**

Experimental models of colitis induced by chemical agents are used in the analysis of pathological mechanisms of IBD as well as the development of therapeutic agents. The referred method facilitates the induction of colitis. Some chemicals, such as dextran sodium sulfate (DSS) and trinitrobenzene sulfonic acid (TNBS) are the most commonly used substances. Models with such agents have been used for more than 20 years for the investigation and circumstances that affect the development of IBD [16] (**Table 4**).

Induction of inflammation by chemical agents can cause disorders in the barrier of the intestinal mucosa and/or cause hapten-induced hypersensitivity reactions [18]. Several factors are related to the magnitude of the onset of colitis in models induced by chemical substances. Although these models do not have the complexity of human IBD, they can contribute to the study of the processes involved in the control of the disease [72].


**Table 4.** Chemically induced models of intestinal inflammation.

#### **a.** DSS approach

DSS methodology has been used to induce colitis since 1985 because the disease induced is very similar to the human disease [73]. Its mechanism of action is related to direct epithelial toxicity, which impacts on the epithelial barrier of the intestinal mucosa [18]. In the referred methodology, the substance is diluted in water for animal drinking, for a period ranging from 5 to 7 days. The inflammation induced by DSS has characteristics similar to diarrhea with bleeding, ulcerations and granulocyte infiltration. Dysplasia often occurs during the chronic stage of the inflammation, which is very similar to ulcerative colitis in humans [16, 74].

Oxazolone is generally administered after subcutaneous pre-sensitization (abdomen), which stimulates greater formation of Th2 cytokines and inflammation of the distal colon resem-

Like TBNS, oxazolone is also administered rectally. Acute inflammation of the distal mucosa and submucosa generally involves ulcers and infiltrations of neutrophils, macrophages and lymphocytes. The type of response triggered depends on the dose of the substance administered. Overall, this model is useful for the investigation of specific characteristics of the

**Type of induction Characteristics Limitations Advantages References**

in general

It analyzes the pathogenesis of IBD Investigation of certain inflammatory mediators and cellular interactions present in intestinal inflammation Study and better understanding of the complexity of multiple genes and the different types of polymorphisms observed in patients

Use of Animal Models in the Study of Colitis http://dx.doi.org/10.5772/intechopen.75608

> It encompasses methodologies that are considered easy to induce, and its simplicity allows it to be used in several experimental protocols

Investigation of specific route abnormalities and immune gut inflammation To study the role of regulatory T cells and mucosal immune

regulation

Because there is no intervention, it mimics the complex and multifactorial aspects that encompass the disease in humans

[14, 18, 19]

225

[14, 18]

[14, 18]

[14, 18, 66]

It tests the efficacy of new drugs in a lesser than other approached in a preclinical studies

It is not sufficient to understand and characterize the inflammatory and immunological processes involved in intestinal inflammation and the pathogenesis of IBD

It uses a factor (adaptive immunity) that is not the only necessary requirement for the development

Difficulty related to the acquisition of models (availability)

of IBD

bling ulcerative colitis [74].

inflammatory process in chronic IBD [72].

modification;

overexpression or absence of a non-functional gene/protein of interest in all cell types or in a particular cell type, acting on the promotion of inflammation by impairment of epithelial barrier function and bacterial sensing, innate immune signaling, immune regulation, and stress response signaling

inflammation by acting on the disturbance of the mucosal barrier, epithelial and/or by triggering reactions of hypersensitivity by hapten

inflammation in an immunodeficient host through the selective transfer of immune cell

The crossing of two types of rodents with different genetic contexts provided models that present spontaneous intestinal inflammation, without induced genetic alterations

**Table 5.** Comparative presentation of the various methods of colitis induction.

or interventions

**Genetic modification** Occurs by gene

**Chemical agents** It induces intestinal

**Cell transfer** It induces intestinal

**Spontaneous inflammation** types

The inflammatory immune response occurs immediately after disturbance of the intestinal epithelium, due to contact of the antigens in the lumen with the immune cells of the mucosa and submucosa areas [72].

Acute and chronic forms of the disease can be induced, according to the doses and treatment cycles. DSS was also used to induce IBD in transgenic and immunodeficient animals, and most of them are prone to intestinal inflammation. Also, the symptoms and the pathology are more severe with the association of this chemical agent [18]. DSS-induced colitis is frequently used in studies on innate immune processes involved in the onset of IBD and also in restoring the intestinal barrier integrity [72].

#### **b.** TBNS

In hapten-induced colitis, the TNBS substances dinitrobenzene sulfonic acid (DNBS) or oxazolone dissolved in ethanol can be administered rectally. The type of response triggered (Th1/ Th2) will depend on the hapten selected, as well as on the susceptibility of the animal, and route of administration of the chemical agent. Ethanol is used to disrupt the barrier of the intestinal mucosa, while the agent (TNBS, DNBS or oxazolone) is associated with an autologous protein or microbiota byproducts, becoming immunogenic, and triggering the interaction of specific antigens and cells of the immune system [18, 75, 76]. The IBD models induced by hapten, similar to those that use DSS, can also be applied in transgenic and immunodeficient animals, as well as in those susceptible to immune-mediated colitis [77–80].

In the beginning of the experiment with TNBS-induced model, one single dose can be administered, resulting in acute inflammation, with Th1 response occurring in 2–3 days. Initial sensitization with TNBS can be done by rectal application or via skin, and another administration must be performed 6 days later for the development of delayed hypersensitivity response to TNBS-haptenized colonic proteins [81].

TNBS is administered rectally with ethanol, amidst haptenization of the proteins from the microbiota and the emergence of T CD4+ cells. The severity and the extent of the inflammation depend on genetic factors inherent in the animals and the presence or absence of bacteria that activate T cells [71]. T CD4 + cells are strongly related to Th1-mediated immune responses through IL-12 cytokines, culminating in transmural colitis similar to CD [80, 82].

The IBD model that uses DNBS is similar to the one induced by TNBS, because there is extensive tissue damage and acute inflammatory process. Also, as it occurs in CD, it depends on T CD4+ cells [80].

Oxazolone is generally administered after subcutaneous pre-sensitization (abdomen), which stimulates greater formation of Th2 cytokines and inflammation of the distal colon resembling ulcerative colitis [74].

**a.** DSS approach

and submucosa areas [72].

the intestinal barrier integrity [72].

TNBS-haptenized colonic proteins [81].

CD4+ cells [80].

**b.** TBNS

DSS methodology has been used to induce colitis since 1985 because the disease induced is very similar to the human disease [73]. Its mechanism of action is related to direct epithelial toxicity, which impacts on the epithelial barrier of the intestinal mucosa [18]. In the referred methodology, the substance is diluted in water for animal drinking, for a period ranging from 5 to 7 days. The inflammation induced by DSS has characteristics similar to diarrhea with bleeding, ulcerations and granulocyte infiltration. Dysplasia often occurs during the chronic stage of the inflammation, which is very similar to ulcerative colitis in humans [16, 74].

224 Experimental Animal Models of Human Diseases - An Effective Therapeutic Strategy

The inflammatory immune response occurs immediately after disturbance of the intestinal epithelium, due to contact of the antigens in the lumen with the immune cells of the mucosa

Acute and chronic forms of the disease can be induced, according to the doses and treatment cycles. DSS was also used to induce IBD in transgenic and immunodeficient animals, and most of them are prone to intestinal inflammation. Also, the symptoms and the pathology are more severe with the association of this chemical agent [18]. DSS-induced colitis is frequently used in studies on innate immune processes involved in the onset of IBD and also in restoring

In hapten-induced colitis, the TNBS substances dinitrobenzene sulfonic acid (DNBS) or oxazolone dissolved in ethanol can be administered rectally. The type of response triggered (Th1/ Th2) will depend on the hapten selected, as well as on the susceptibility of the animal, and route of administration of the chemical agent. Ethanol is used to disrupt the barrier of the intestinal mucosa, while the agent (TNBS, DNBS or oxazolone) is associated with an autologous protein or microbiota byproducts, becoming immunogenic, and triggering the interaction of specific antigens and cells of the immune system [18, 75, 76]. The IBD models induced by hapten, similar to those that use DSS, can also be applied in transgenic and immunodefi-

In the beginning of the experiment with TNBS-induced model, one single dose can be administered, resulting in acute inflammation, with Th1 response occurring in 2–3 days. Initial sensitization with TNBS can be done by rectal application or via skin, and another administration must be performed 6 days later for the development of delayed hypersensitivity response to

TNBS is administered rectally with ethanol, amidst haptenization of the proteins from the microbiota and the emergence of T CD4+ cells. The severity and the extent of the inflammation depend on genetic factors inherent in the animals and the presence or absence of bacteria that activate T cells [71]. T CD4 + cells are strongly related to Th1-mediated immune responses

The IBD model that uses DNBS is similar to the one induced by TNBS, because there is extensive tissue damage and acute inflammatory process. Also, as it occurs in CD, it depends on T

cient animals, as well as in those susceptible to immune-mediated colitis [77–80].

through IL-12 cytokines, culminating in transmural colitis similar to CD [80, 82].

Like TBNS, oxazolone is also administered rectally. Acute inflammation of the distal mucosa and submucosa generally involves ulcers and infiltrations of neutrophils, macrophages and lymphocytes. The type of response triggered depends on the dose of the substance administered. Overall, this model is useful for the investigation of specific characteristics of the inflammatory process in chronic IBD [72].


**Table 5.** Comparative presentation of the various methods of colitis induction.

**Table 5** shows a comparative presentation of the various ways colitis disease is induced as discussed herein. Each of the several models discussed here have similarities with human IBD, and offer advantages for the study of certain aspects involved in the pathogenesis of the disease. Induction by chemical agents is often used widely by researchers mainly because it is easier, although it does not contribute to the elucidation of inflammatory and immunological processes involved in IBD [14, 18]. Genetic modification allows the study of specific aspects present in IBD; however, such form of induction does not allow to analyze the disease in a global way, and contributes less to the test of efficacy of new drugs [14, 18, 19]. Cellular transfer helps to study specific issues, contributing to the investigation of the role of regulatory T cells and mucosal immune regulation, but adaptive immunity alone does not act in the onset of IBD [14, 18]. The spine development of colitis reproduces the disease as in humans (since there is no intervention), allowing the investigation of complex and multifactor situations that are present in the disease, nevertheless, there is a low availability of models reported in the literature [14, 18, 66].

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