Allergic airway inflammation in mice:

Similarities and differences with human asthma

A.J.M. van OosterhoutLab. Allergology & Pulmonary Diseases

Groningen Research Institute for Asthma & COPD

University Medical Center GroningenNetherlands

Acute allergic reactionWheezingBronchoconstriction

Histamine

Th2 cell

IL-4IL-5IL-13

Chronic diseaseEosinophilsGoblet cells/mucusAirway hyperreactivity

Danger signal

Epithelial cells

B cellDendritic cell Mastcell

IL-4IgEIgE

Th2 cell

Allergic sensitization Asthma manifestations

Natural history of allergic asthma

Advantages of mouse model Genetic homogeneity Identical age Well-controlled environment (food,

specified pathogens, climate) Availability of isolated tissues or cells Time-series; induction vs effector phase Experimental conditions/therapeutics “Toolbox” (gene-targeting, immunology)

Disadvantages“the mouse trap”

HDM (protease-active)

aerosol

Basics of mouse asthma models

Allergic sensitisation; IgE / Th2

Ovalbumin (harmless)+/- Alum adjuvant(Th2-skewing)

Repeated allergen provocation

Airway manifestationsof asthma

aerosol

aerosol

Tolerance

Specific IgE ++ ++

MC degranulation +++ ++ (serotonin)

Early bronchoconstriction +++ +

Late bronchoconstriction +/- (50%) -

AHR (vivo) +++ +

BAL eosinophils (%) 10-20% 20-80%

EOs degranulation +++ +

Th2 driven + +++

Goblet/mucus ++ ++

Fibrosis +++ ++

Basement membrane +++ +

Smooth muscle hyperplasia

+++ +/-

Airway vascular remodeling ++ +

Many critics on mouse models

Nasal breathing High levels of antigen/allergen needed Systemic sensitisation is not the

natural history in humans Ovalbumin is a not an aero-allergen Lung anatomy is very different No late-phase bronchoconstrictive

reaction

}HDM

Critics on mouse modelscontinued….

Severity of AHR is small compared to humans No persistent AHR; remission upon long-term

challenge No models of chronic asthma cq remodelling Many eosinophils reminiscent of allergic

alveolitis No substantial eosinophil degranulation (Too) strong Th2 biased Steroid sensitive but doubts on predictability

for human intervention

Airway hyperreactivity

0 1.6 3.1 6.2 12.5 25 500.0

2.5

5.0

7.5

10.0

*

*

*

Saline Ovalbumin

Penh

Methacholine (mg/ml)

But, we can make a better mouse…

Severe AHR:Associated with eosinophil degranulation

Ochkur e.a. JI 178 (2007) 7889

IL-5 (T-cell) & eotaxin-2 (epithelial) double transgenic mouse

Acceptable statements General cellular and molecular pathways are similar A mouse model cannot encompass all genetic and environ-

mental factors causing asthma in a single human individual Asthma is not a single disease but a syndrome, likewise, it can

not be modelled by a single (inbred) mouse model Mouse models are usefull to model specific pathways/

processes involved in asthma, not the whole syndrome Animal models are required for pre-clinical drug testing Mouse model are excellent for immunological studies; other

species (e.g. guinea-pig, sheep etc) may be more suitable for other research questions

Mouse models can identify novel (susceptibility) genes implicated in asthma (e.g. TIM1, CaCC1)

Provocative statements

Without mouse models, causal relationships can hardly be established in asthma and it remains descriptive phenomenology

Many novel concepts originate from animal (a.o. mouse) models

Real progress in our understanding of asthma is dependent on animal (mouse) models

Humans should not be put at risk if the research question can also be addressed in an animal model (e.g. pre- and ante-natal experimentation)

We can learn from the differences between human asthma and mouse models

CommunicateIterative hand-in-hand progress of mouse models & human asthma

“Translational research”

Basic scientist Clinicians

Epidemiologists, etc etc

How can we model chronic

severe asthma?

In both directions

Recommendations for mouse models

Use an aeroallergen (e.g. house-dust mite, pollen) in stead of innocuous antigen (ovalbumin)

Allergic sensitization by inhalation only Repeated low dose inhalation challenge Confirm non-invasive lung function

(Buxco) with invasive technique

Acknowledgements

Examplesnew concepts/discoveries

1986 1995 2001 1999 Mouse

Th1/Th2 balance

Treg cells CaCC1 TIM-1

NK T-cells

1991 2001 ‘02/’03 2006 Human

(1) vascular inflammation in the mouse tissue (black arrows) as compared with absence of inflammation in vessels from the human tissue (black arrows);

(2) smooth muscle is present in bundles in the human tissue (green arrows), whereas there is only a very modest band of possible myofibroblasts below the basement membrane (green arrows) in the mouse airway;

(3) submucosal glands are present in the human tissue (open arrows) but absent in the mouse airway;

(4) simple single-layered columnar epithelium in the mouse airway with more complex epithelial layer in the human airway.

Wenzel & Holgate, AJRCCM 174 (2006) 1173

PC20 methacholine (mg/ml)

EG

2+ (

cells

/mm

2)

400

300

200

100

0

0.01 0.1 1 10 100

Rs = -0.58p = 0.001

Sont et al. Thorax 1996;51:496-501

Lung branching pattern

Zosky & Sly, CEA 37 (2007) 973

6-8 branches

20-23 branches

“absent small airways pathology”

Extreme peribronchial (↓, inset) and perivascular (▼) inflammation in a “standard” mouse model of asthma (top panel) that is more akin to allergic alveolitis than asthma.

Mouse model of asthma using repeated low-dose challenges over a period of weeks, resulting in a more moderate level of inflammation that is localized in the main conducting airways

Zosky & Sly, CEA 37 (2007) 973

Basics of mouse asthma models

Allergic sensitisation; IgE / Th2

Ovalbumin (harmless)+/- Alum adjuvant(Th2-skewing)

Repeated allergen provocation

Airway manifestationsof asthma

aerosol

aerosol

ToleranceRemission

Airway remodelling

Thickened basement membrane

Morphologic Changes in Asthma

Subbasement MembraneThickening

Mucus

Mucous GlandHypertrophy

VascularDilation Edema

SubepithelialFibrosis

EpithelialDamage

Inflammatory Cell

InfiltrationSmooth MuscleHypertrophy