Group 2: Animal models for mast cell research
Group members
Folkerts J (PhD student, NL [email protected]), Levi T (MSc student, IL [email protected]), Rudich N
(PhD student, IL [email protected]), Sałkowska A (PhD student, PL [email protected]),
Stegurova L (PhD student, CZ [email protected]), Woidacki K (Post-doc, DE
[email protected]), Tiligada K (Trainer, EL [email protected])
During the last decades the developed models enlightened the central role of MCs and
basophils in multiple physiological and pathophysiological pathways. Yet, there is still a
great need for the improvement of existing and the development of novel reliable in vivo
animal models to be used in the search of mast cell (MC) function. The aim of Group 2
exercise was to compare and critically evaluate one established [1] and two new [2-3] in
vivo animal models related to MC research.
One of the established models for studying MC-mediated responses during the early
allergic reactions (EAR) and pharmacological approaches related to allergy treatment is
the guinea pig, as described in the paper by Riley et al [1]. According to the authors,
contrary to mice, the respiratory tract of guinea pigs contains higher numbers of MCs,
which secrete mediators that induce airway smooth muscle contraction. Riley et al. [1]
investigated whether the EAR may be circumvented by the administration of different
combinations of agents that inhibit the function/synthesis of main MC mediators. These
included the CysLT1 receptor antagonist montelukast, the histamine H1 receptor
antagonist pyrilamine and the prostanoid biogenesis inhibitor indomethacin. The
authors concluded that, as in humans, the guinea pig allergic inflammation model
exhibits EAR, supporting its suitability for the in vivo identification of mast cell mediators
that contribute to the development of asthma, histamine and leukotrienes being major
contributors of the EAR. Moreover, they proposed that combination therapy with
selective inhibitors of key mediators could improve asthma management. However,
there were major limitations in this study, including the absence of dose-response
curves as well as the insufficient justification for the selection of the drugs used and the
relevance of OVA sensitization to the human disease. More importantly, the results
provided limited, if any, novel information related to both the (patho)physiology and
treatment of EAR and MC role/function.
On the other hand, two new models were proposed to serve as powerful tools in the
functional role of MCs in immune responses [2-3].
In 2011, Da’as and colleagues [2] proposed that the zebrafish intestine MCs possess
FcεRI-like receptors that may mediate immune responses. In this model, the increased
plasma tryptase levels observed upon stimulation with C48/80 or Aeromonas
salmonicida were inhibited by the administration of ketotifen, a histamine receptor
antagonist and MC membrane stabilizing agent. However, some limitations need to be
mentioned: (a) tryptase, but no other MC mediator, was quantified; (b) the large
variability of tryptase levels and the normalization to human tryptase activity levels raise
questions regarding the use of tryptase as a reliable indicator of MC activation; (c) the
authors did not adequately comment on other immune cells that showed morphological
similarities to MCs, including basophils and eosinophils; (d) functional assays aimed to
validate the TLR and FcεRI functions have not been performed in this model; (e) the
inhibition of the IgE-mediated pathway would be a useful approach to support the
experiments regarding the IgE-mediated response. In conclusion, this study provided
preliminary data (with no follow-up to our knowledge) that the zebrafish may serve as a
potential model for studying basic MC behavior and functionality. Additional solid
evidence is required to support the reported findings.
1
Group 2: Animal models for mast cell research
The translation of findings from animal models to human (patho)physiology remains an
obstacle in biomedical research. Physiological readouts of allergic responses can
greatly differ between mouse and man, thereby reducing the potential for generating
new therapeutic approaches. Recently, Ito et al [3] established a human allergy model
by using the human IL-3/GM-CSF-transgenic NOG mice. In contrast to other humanized
mouse models, the transplantation of hematopoietic human CD34+ cells was associated
with the development of FcεR-expressing mature MCs and basophils based on bearing
human IL-3 and GM-CSF genes. These mice where capable of developing passive
cutaneous anaphylaxis induced either by nitrophenylacetyl (NP) or serum from cedar
pollinosis patients. However, although successful allergic reactions, including histamine
release, were confirmed in the passive cutaneous anaphylaxis model, in most humans,
active sensitization occurs. Moreover, there is a need for comparison studies to address
any differences between allergic responses induced in classical mouse strains and
transplanted humanized mice. In conclusion, the humanized mouse models may be a
useful tool for developing anti-allergic drugs in the future and the findings are a
significant step forward in translational medicine. Yet, this model needs to be validated
in additional allergic settings, such as asthma, atopic dermatitis and food allergy.
In summary, we would like to emphasize that the reliability of in vivo animal
models presents some limitations yet to be resolved in order to reach beneficial
end-points. These include the need for the standardization of validation protocols
as well as the harmonization of the suitability of a number of mediators and
surface components that are used as markers in MC-related responses, the
appropriateness of sensitization triggers/protocols, the properties of
pharmacologically active agents, including the recently described ligand-directed
signaling, etc. In addition, research using experimental animals needs to take into
consideration animal strain and gender differences, besides age and diurnal
variations, the threshold and baseline responses as well as the importance of
considering inter- and intra-species variations related to immune cell-cell
interaction, particularly in the case of Tg and humanized mouse models.
Finally, as experimental animals differ from humans in various aspects, including
MC/basophil phenotypes and behavior, we would like to propose the ‘visibility’ of
negative results and the establishment of a comparative definition of MCs and
basophils, consisting of a list of the minimal anatomical and functional
(physiological, biochemical, genetic) characteristics of these cells in humans and
in various experimental animal species.
Acknowledgements
We would like to thank the organizers for the warm hospitality and for providing this excellent opportunity
to study mast cells and basophils during this very productive training school in the Holy Land.
Training Material
[1] Riley JP, Fuchs B, Sjöberg L, Nilsson GP, Karlsson L, Dahlén SE, Rao NL, Adner M (2013). Mast
cell mediators cause early allergic bronchoconstriction in guinea-pigs in vivo: a model of relevance to
asthma. Clin Sci (Lond) 125:533-42. doi: 10.1042/CS20130092. PubMed PMID: 23799245
[2] Da'as S, Teh EM, Dobson JT, Nasrallah GK, McBride ER, Wang H, Neuberg DS, Marshall JS, Lin
TJ, Berman JN (2011) Zebrafish mast cells possess an FcɛRI-like receptor and participate in innate
and adaptive immune responses. Dev Comp Immunol 35:125-34. doi: 10.1016/j.dci.2010.09.001.
PubMed PMID: 20849876
[3] Ito R, Takahashi T, Katano I, Kawai K, Kamisako T, Ogura T, Ida-Tanaka M, Suemizu H, Nunomura
S, Ra C, Mori A, Aiso S, Ito M (2013) Establishment of a human allergy model using human IL3/GM-CSF-transgenic NOG mice. J Immunol 191:2890-9. doi: 10.4049/jimmunol.1203543. PubMed
PMID: 23956433
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Group_2_Abstract - Mast Cell