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Endothelial protein C receptor supports hematopoietic stem cell engraftment and expansion in Mpl-deficient mice

Saskia Kohlscheen, Franziska Schenk, Marcel G.E. Rommel, Katharina Cullmann and Ute Modlich

Key points

  • Lentiviral Epcr expression rescued phenotypic LT-HSC in the model of Mpl-deficient aplastic anemia.

  • Lineage marker negative, Epcr positive BM cells comprise the population with engraftment potential.

Abstract

Thrombopoietin (Thpo)/Mpl signaling controls hematopoietic stem cell (HSC) self-renewal and quiescence, however, how these two seemingly opposing functions are controlled is not well understood. By transplantation of lentiviral transduced hematopoietic cells in the Mpl-deficient mouse model we addressed whether known or predicted Thpo target genes were able to rescue the Mpl-deficient phenotype of the mice. Among the tested genes we identified endothelial protein C receptor (Epcr) to expand HSC with long-term (LT)-HSC surface phenotype in Mpl-/- mice and to enable secondary transplantation of Mpl-deficient BM. Epcr-transduced Mpl-/- HSC enter quiescence earlier after transplantation than control transduced Mpl-/- cells and upregulated expression of the anti-apoptotic gene Bcl-xL. Also in the wildtype background, Epcr expression marked the engrafting population in the BM. Furthermore, Epcr expression in Mpl-/- hematopoiesis increased the number of megakaryocytes in the BM. In vitro Thpo supported the surface expression of Epcr on primary murine hematopoietic stem and progenitor cells. With these data we add new insights into Thpo-dependent influence on HSC engraftment after transplantation. This may be of use for the in vitro manipulation of HSC, also in the context of gene therapy.

  • Submitted March 9, 2018.
  • Accepted January 15, 2019.