Modeling allergic asthma: from in vitro assays to virtual patients

Animal models of asthma: value, limitations and opportunities for alternative approaches

Asthma remains an area of considerable unmet medical need. Few new drugs have made it to the clinic during the past 50 years, with many that perform well in preclinical animal models of asthma, failing in humans owing to lack of safety and efficacy. The failure to translate promising drug candidates from animal models to humans has led to questions about the utility of in vivo studies and to demand for more predictive models and tools based on the latest technologies. Following a workshop with experts from academia and the pharmaceutical industry, we suggest here a disease modelling framework designed to better understand human asthma, and accelerate the development of safe and efficacious new asthma drugs that go beyond symptomatic relief.

Ultrastructural changes of platelets and fibrin networks in human asthma: a qualitative case study

Platelets and fibrin networks play an important role in asthma and the BALB/c asthmatic mouse model has previously been successfully used to study platelet ultrastructure. In control BALB/c mice, major, thick fibers and minor thin fibers and tight, platelet aggregates with typical pseudopodia formation, are present. Minor fibers of asthmatic mice have a netlike appearance covering the major fibers, whereas the platelets seem to form loosely connected, granular aggregates. The question that now arises is whether platelets and fibrin networks of humans with asthma will have the same ultrastructure as seen in the BALB/c asthmatic model. In order to answer this question, ultrastructure of platelets and fibrin networks from two participants (controlled asthma and uncontrolled, chronic asthma) were studied and compared with that of human controls and BALB/c asthmatic mice. Peak flow measurements of the controls and patients were also assessed. Results showed that similar platelet and fibrin network ultrastructure is found in uncontrolled, human participants and BALB/c asthmatic animals. The challenge when using animal models is always whether the model adequately mimics the human disease; the current research, therefore, shows morphological support for the use of this model in the study of asthma. These morphological results may also provide additional information to plan treatment regimes for sufferers of this very debilitating disease.

Comparative ultrastructural analyses of platelets and fibrin networks using the murine model of asthma

The murine Balb/c asthma model has been used successfully for a number of in vivo immunological applications and for testing novel therapeutics, and it is a reliable, clinically relevant facsimile of the human disease. Here we investigate whether this model can be used to study other components of the human body, e.g. ultrastructure. In particular, we investigate the effect of the phytomedicine Euphorbia hirta (used to treat asthma), on the ultrastructure of fibrin as well as platelets, cellular structures that both play an important role in the coagulation process. Hydrocortisone is used as positive control. Ultrastructure of the fibrin networks and platelets of control mice were compared to mice that were asthmatic, treated with two concentrations of hydrocortisone and one concentration of the plant material. Results indicate control mice possess major, thick fibers and minor thin fibers as well as tight round platelet aggregates with typical pseudopodia formation. Minor fibers of asthmatic mice have a netlike appearance covering the major fibers, while the platelets seem to form loosely connected, granular aggregates. Both concentrations of hydrocortisone make the fibrin more fragile and that platelet morphology changes form a tight platelet aggregate to a more granular aggregate not closely fused to each other. We conclude that E. hirta does not impact on the fragility of the fibrin and that it prevents the minor fibers to form the dense netlike layer over the major fibers, as is seen in untreated asthmatic mice. This ultrastructural morphology might give us better insight into asthma and the possible new treatment regimes.

Are mouse models of allergic asthma useful for testing novel therapeutics?

Experimental mouse allergic asthma is a reliable, clinically relevant facsimile of human disease. The focus here is to demonstrate that antigen-induced mouse allergic asthma is a useful model for testing novel therapeutics. Furthermore, it is especially crucial to treat mice during established disease, either during ongoing clinically manifest disease or to prevent disease relapses. In addition, our results indicate that lung Th2 resting memory cells are important targets for the treatment of allergic asthma.