Transcript Integrating model organisms to the study of human IBD

Lauri Diehl, Sr. Scientist/Pathologist,
Genentech
December 5, 2014
Rodents are the model organisms of
choice for IBD-related research
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 Mouse most common used
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Inbred strains
Ease of genetic manipulation
Reagent availability
Cost
Housing space
 Spontaneous colitis occurs in several species
 Humane considerations
 Etiology?
Reliance on murine models is
controversial
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Virtually every major medical
Despite some outstanding drugdevelopment successes, the mouse
version of multiple sclerosis has been
worryingly unreliable at screening
human treatments.
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 J. Rice
prove the safety and efficacy of a new Nature Outlook
April 2012
treatment.
C. Everett Koop, M.D
Former U.S. Surgeon
General
(Genomic) responses in corresponding
mouse models correlate poorly with
(acute inflammatory) human
conditions…
J. Seok et al, PNAS, 2013
How are mouse colitis models used?
 Basic scientific research
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 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
What is the best IBD model?
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 Better question is “what do we need from this
model?”
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Genetics
Location of interest
Lesion of interest
Response to control
Cell type of interest
Molecule of interest
Pathway of interest
Experimental goals should drive
model choice
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 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
Commonly used “workhorse”
intestinal inflammation models
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 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
DSS colitis model is used to query
acute disease manifestations
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 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
Cox et al, 2012
Genetic considerations can be a basis
for model selection
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 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
Jostins et al, Nature, 2012
IL-10KO colitis model
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 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
Shah et al, Curr Allergy Asthma Rep, 2012
Model validation needs depend on
scientific question
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 General validation criteria
 Reproducibility
IL-10 KO respond to anti-TNF
 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
Does this look like Crohn’s disease?
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 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
Normal ileum
 Transmural inflammation, noncaseating
granulomas, no submucosal fibrosis
 TNFa inhibition is protective
TNFdeltaARE het
Crohn’s disease
Murine model of submucosal fibrosis
would be valuable
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 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
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Chronic streptomycin tx required
Presence of active infection is problematic
 Genetic models – TL1a transgenic
Salmonella enterica
Grassl et al, 2008
TL1A Transgenic mouse model
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 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?
Aiba et al, Med Inflam, 2013
Barrett et al, Am J Path, 2012
Crohn’s disease
Integrating model organisms to the
study of human IBD
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 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