Lauri Diehl, Sr. Scientist/Pathologist, Lauri Diehl, Sr. Scientist/Pathologist, GenentechGenentech

December 5, 2014December 5, 2014

Mouse most common used Inbred strains Ease of genetic manipulation Reagent availability Cost Housing space

Spontaneous colitis occurs in several species Humane considerations Etiology?

Rodents are the model organisms of choice for IBD-

related research

Reliance on murine models is controversial

Virtually every major medical advance for both humans and animals has been achieved through biomedical research using animal models to study and find a cure for a disease and through animal testing to prove the safety and efficacy of a newtreatment.

C. Everett Koop, M.DFormer U.S. SurgeonGeneral

Despite some outstanding drug-development successes, the mouse version of multiple sclerosis has been worryingly unreliable at screening human treatments.J. RiceNature OutlookApril 2012

(Genomic) responses in corresponding mouse models correlate poorly with (acute inflammatory) human conditions…J. Seok et al, PNAS, 2013

Basic scientific research

Mucosal immunology IBD pathogenesis Anatomic and immunologic differences between human and mouse

Preclinical efficacy testing Drives industry decision making Predictive value?

Pharmacokinetics Biomarker studies

Predictive and/or pharmacodynamic markers Earlier and more diverse hypothesis testing

How are mouse colitis models used?

Better question is “what do we need from this

model?” Genetics Location of interest Lesion of interest Response to control Cell type of interest Molecule of interest Pathway of interest

What is the best IBD model?

Many murine colitis/enteritis models exist

Genetic (spontaneous or induced) Chemical

Degree of characterization varies Pathway involvement Impact of local microflora environment

Degree of technical difficulty varies may influence model selection inappropriately

Published data should be approached with caution

Experimental goals should drive model choice

Chemical-induced colitis

DSS colitis, TNBS colitis Rapid and reproducible induction of colitis Use widely available mouse strains

Immune-mediated colitis models Transfer colitis, IL-10KO colitis May be more technically challenging and time

consuming

Commonly used “workhorse” intestinal inflammation models

Dextran sodium sulfate in drinking

water Widely used for preclinical efficacy

studies Suitable for genetically modified mice Study duration varies and may impact

pathway involvement Has minimal T cell involvement Best suited for studying epithelial

(short duration) or myeloid/innate immune (longer duration) effects

DSS colitis model is used to query acute disease

manifestations

Cox et al, 2012

More than 160 IBD susceptibility genes/loci

identified with many shared between UC and Crohn’s

Are models based on human genetics useful for preclinical efficacy or biomarker studies? IL-10 KO TL1A (TNSF15) Tg

Genetic considerations can be a basis for model selection

Jostins et al, Nature, 2012

Human IL-10 and IL-10R polymorphisms associated with very

early onset IBD (dx at less than 6 years of age) Loss of function mutations Severe disease, colon only

IL-10KO – spontaneous chronic colon inflammation Gradual onset, variable disease penetrance

Mouse strain dependent 129/Sv > Balb/c > C57BL/6

Microflora dependent Amplified by NSAIDS

Benefits and caveats as an IBD model? Pathway of interest represented? May need to validate in model

IL-10KO colitis model

Shah et al, Curr Allergy Asthma Rep, 2012

Model validation needs depend on scientific question

General validation criteria Reproducibility

Disease incidence IL-10KO often requires piroxicam tx

Experimental observation Specific validation criteria

Response to control treatment Treatment response in IL-10KO

Anti-TNF therapy – variable Anti-p40 – highly effective Relationship to human response?

Pathways of interest Anatomic localization of lesions

Colon vs. intestine, mucosal vs. submucosal Especially for fibrosis questions

Scheinin et al, Clin Exp Immunol, 2003

IL-10 KO respond to anti-TNF

Does this look like Crohn’s

disease? Does TNFdeltaARE model phenocopy CD?

Chronic TNFa elevation Deletion of TNF AU-rich elements (ARE)

ARE mediate TNFa transcript degradation Posttranscriptional regulatory mechanism Kontoyiannis et al, Immunity, 1999

Ileitis and arthritis Transmural inflammation, noncaseating

granulomas, no submucosal fibrosis TNFa inhibition is protective

Normal ileum

TNFdeltaARE het

Crohn’s disease

No animal model described which develops the

morphologic features of human fibrostenotic disease Rat models described (not widely used)

Mouse models preferred Chronic inflammation, no smooth muscle proliferation

Mouse models have been described Chemical models – chronic DSS, chronic TNBS Infectious models – chronic Salmonella

Chronic streptomycin tx required Presence of active infection is problematic

Genetic models – TL1a transgenic

Murine model of submucosal fibrosis would be valuable

Salmonella enterica

Grassl et al, 2008

TL1A interaction with DR3 increases IFN-g and IL-17

Polymorphism may predispose to fibrostenotic disease in Crohn’s patients

Tg mice (T or myeloid cell overexpression) develop mild enteritis Ileal involvement and collagen deposition (“fibrosis”), no

smooth muscle proliferation Is this suitable for specific questions? What validation

would be needed?

TL1A Transgenic mouse model

Barrett et al, Am J Path, 2012Aiba et al, Med Inflam, 2013 Crohn’s disease

Understanding the suitability of animal models is

important when evaluating published data Successful integration of animal models into IBD

research requires a clear understanding of the scientific question.

There is no model which is suitable for every question and, for some questions, none of the established models may be ideal. We need to guide the discussion toward questions

which can enable successful study decisions and make best use of scarce resources

Integrating model organisms to the study of human IBD