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Apoptotic effects of platelet factor VIII on megakaryopoiesis: implications for a modified human FVIII for platelet‐based gene therapy
Author(s) -
Greene T. K.,
Lyde R. B.,
Bailey S. C.,
Lambert M. P.,
Zhai L.,
Sabatino D. E.,
Camire R. M.,
Arruda V. R.,
Poncz M.
Publication year - 2014
Publication title -
journal of thrombosis and haemostasis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.947
H-Index - 178
eISSN - 1538-7836
pISSN - 1538-7933
DOI - 10.1111/jth.12749
Subject(s) - hemostasis , platelet , genetic enhancement , coagulation , furin , thrombopoiesis , megakaryocyte , bone marrow , immunology , apoptosis , cancer research , microbiology and biotechnology , chemistry , gene , medicine , biology , progenitor cell , stem cell , biochemistry , enzyme
Summary Background Ectopically expressed B‐domainless factor VIII in megakaryocytes is stored in α‐granules, is effective in a number of murine hemostatic models, and is protected from circulating inhibitors. However, this platelet (p) FVIII has different temporal–spatial availability from plasma FVIII , with limited efficacy in other murine hemostatic models. Objectives and methods We sought to improve pFVIII hemostatic efficacy by expressing canine (c) FVIII , which has higher stability and activity than human (h) FVIII in FVIII null mice. Results and conclusions We found that pcFVIII was more effective than phFVIII at restoring hemostasis, but peak pcFVIII antigen levels were lower and were associated with greater megakaryocyte apoptosis than phFVIII. These new insights suggest that p FVIII gene therapy strategies should focus on enhancing activity rather than levels. We previously showed that modification of the PACE/furin cleavage site in hFVIII resulted in secretion of hFVIII primarily as a single‐chain molecule with increased biological activity. In megakaryocytes, this variant was expressed at the same level as phFVIII with a lentiviral bone marrow transplant approach to reconstitute FVIII null mice, but was more effective, resulting in near‐normal hemostasis in the cremaster laser injury model. These studies may have implications for pFVIII gene therapy in hemophilia A.