Page 280 - Haematologica - Vol. 105 n. 6 - June 2020

Transfusion Medicine
Ferrata Storti Foundation
Haematologica 2020 Volume 105(6):1738-1749
Genetic platelet depletion is superior in platelet transfusion compared to current models
Manuel Salzmann,1 Waltraud C. Schrottmaier,1 Julia B. Kral-Pointner,1 Marion Mussbacher,1 Julia Volz,3 Bastian Hoesel,1 Bernhard Moser,1 Sonja Bleichert,1,2 Susanne Morava,1 Bernhard Nieswandt,3
Johannes A. Schmid1 and Alice Assinger1
1Institute of Vascular Biology and Thrombosis Research, Medical University of Vienna, Vienna, Austria, 2Department of Surgery, General Hospital, Medical University Vienna, Vienna, Austria and 3Institute of Experimental Biomedicine, University Hospital and Rudolf Virchow Center, University of Würzburg, Würzburg, Germany
ABSTRACT
Genetically modified mice have advanced our knowledge on platelets in hemostasis and beyond tremendously. However, mouse models harbor certain limitations, including availability of platelet specific transgenic strains, and off-target effects on other cell types. Transfusion of genetically modified platelets into thrombocytopenic mice circumvents these problems. Additionally, ex vivo treatment of platelets prior to transfu- sion eliminates putative side effects on other cell types. Thrombocytopenia is commonly induced by administration of anti-platelet antibodies, which opsonize platelets to cause rapid clearance. However, antibodies do not dif- ferentiate between endogenous or exogenous platelets, impeding transfu- sion efficacy. In contrast, genetic depletion with the inducible diphtheria toxin receptor (iDTR) system induces thrombocytopenia via megakary- ocyte ablation without direct effects on circulating platelets. We compared the iDTR system with antibody-based depletion methods regarding their utility in platelet transfusion experiments, outlining advantages and disad- vantages of both approaches. Antibodies led to thrombocytopenia within two hours and allowed the dose-dependent adjustment of the platelet count. The iDTR model caused complete thrombocytopenia within four days, which could be sustained for up to 11 days. Neither platelet depletion approach caused platelet activation. Only the iDTR model allowed efficient platelet transfusion by keeping endogenous platelet levels low and main- taining exogenous platelet levels over longer time periods, thus providing clear advantages over antibody-based methods. Transfused platelets were fully functional in vivo, and our model allowed examination of transgenic platelets. Using donor platelets from already available genetically modified mice or ex vivo treated platelets, may decrease the necessity of platelet-spe- cific mouse strains, diminishing off-target effects and thereby reducing ani- mal numbers.
Introduction
Platelets are anucleate cells, which derive from bone marrow megakaryocytes. Beyond their central role in hemostasis, platelets fulfill important functions in inflammation and infection,1 atherogenesis2 and tissue regeneration.3 Genetically modified mice are valuable tools to investigate the role of platelet function in hemostasis and beyond in complex in vivo systems. However, ascertaining the spe- cific contribution of platelets in global knockout mice can be challenging. Usage of the tissue-specific Cre/loxP system is one possibility to circumvent this problem and enables the investigation of a genetic modification in selected cell types. Mouse lines expressing Cre recombinase via the platelet- and megakaryocyte-specific platelet factor 4 (PF4)4 or the glycoprotein (GP) 1bα promoters5 are essential to delineate distinct platelet mediated effects in complex physiological and patho- physiological settings. However, crossing of mice is expensive and time-consuming
Correspondence:
ALICE ASSINGER
alice.assinger@meduniwien.ac.at
Received: March 19, 2019. Accepted: September 19, 2019. Pre-published: September 19, 2019.
doi:10.3324/haematol.2019.222448
Check the online version for the most updated information on this article, online supplements, and information on authorship & disclosures: www.haematologica.org/content/105/6/1738
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