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Emerging gene therapy clinical trials test the correction of hemophilia A (HA) by replacing factor VIII (FVIII) in autologous hematopoietic stem cells (HSCs). Although it is known that platelets, monocyte/macrophages, and mesenchymal stromal cells can secrete transgenic FVIII, a systematic examination of blood lineages as extrahepatic sources of FVIII, to our knowledge, has not yet been performed. In this study, we sought to provide a comprehensive map of native and lentivirus-based transgenic FVIII production from HSC stage to mature blood cells, through a flow cytometry analysis. In addition, we generated a model of transient HA in zebrafish based on antisense RNA, to assess the corrective potential of the FVIII-transduced HSCs. We discovered that FVIII production begins at the CD34+ progenitor stage after cytokine stimulation in culture. Among all mature white blood cells, monocytes are the largest producers of native FVIII and can maintain protein overexpression during differentiation from HSCs when transduced by a FVIII lentiviral vector. Moreover, the addition of the HSC self-renewal agonist UM171 to CD34+ cells during transduction expanded a subpopulation of CD14+/CD31+ monocytes with excellent ability to carry the FVIII transgene, allowing the correction of HA phenotype in zebrafish. Finally, the HA zebrafish model showed that f8 RNA is predominantly localized in the hematopoietic system at the larval stage, which indicates a potential contributory role of FVIII in hematopoiesis that warrants further investigation. We believe that this study may be of broad interest to hematologists and researchers striving to advance knowledge and permanent treatments for patients with HA.

•A flow cytometry–based blood screening revealed that HSC transmit native and lentiviral vector transgenic FVIII preferentially to CD14+/CD31+monocytes.•CD14+/CD31+monocytes derived from FVIII-transduced HSC rescued the bleeding phenotype in a novel zebrafish model of hemophilia A.

No relevant conflicts of interest to declare.

Introduction

Acute leukemias (AL) is a major cause of cancer death in young age. Extensive research is being conducted to identify novel and innovative approaches for leukemia treatment. Transcriptomic and epigenetic studies might help to discover potential targets, paving the way for molecular-targeted therapies.

No relevant conflicts of interest to declare.

FVIII deficiency or inactivity leads to coagulation malfunction known as Hemophilia A (HA). FVIII overactivity on the contrary is commonly linked to a hypercoagulability state. In steady state, FVIII remains quiescent by forming a non-covalent complex with vWF, and upon coagulation cascade activation, thrombin liberates active FVIII (FVIIIa) from vWF. FVIIIa binds to the plasma membrane of the platelets and other blood cells via its C2 domain phospholipids binding motif to exert its coagulative role.

Background:

Stevens: Travera: Current Employment. Parekh: Foundation Medicine Inc: Consultancy; Amgen: Research Funding; PFIZER: Research Funding; CELGENE: Research Funding; Karyopharm Inv: Research Funding.

No relevant conflicts of interest to declare.