Conversion of adult endothelium to immunocompetent haematopoietic stem cells
Developmental pathways that orchestrate the fleeting transition of endothelial cells into haematopoietic stem cells remain undefined. Here we demonstrate a tractable approach for fully converting adult mouse endothelial cells to haematopoietic stem cells (rEC-HSCs) through transient expression of genes encoding the transcription factors Fosb, Gfi1, Runx1, and Spi1 (also known as Fgrs) and vascular-niche-derived angiocrine factors. The induction phase (day 0–8) of conversion is initiated by expression of Fgrs in mature endothelial cells, which results in endogenous Runx1 expression. During the specification phase (day 8–20), Runx1+ Fgrs-transduced endothelial cells commit to a haematopoietic fate yielding rEC-HSCs that no longer require Fgrs expression. The vascular niche drives a robust self-renewal and expansion phase of rEC-HSCs (at day 20–28). rEC-HSCs have a transcriptome and long-term self-renewal capacity similar to those of adult haematopoietic stem cells, are competent for clonal engraftment and serial primary and secondary multi-lineage reconstituting potential, including antigen-dependent adaptive immune function. Inhibition of TGF-β and CXCR7 or activation of BMP and CXCR4 signalling enhanced generation of rEC-HSCs. Conversion of endothelial cells into autologous authentic engraftable haematopoietic stem cells could aid treatment of haematological disorders.All cell preparations were routinely tested for mycoplasma contamination.We thank J. Downing at St. Jude Hospital for providing the Runx1-IRES-GFP reporter mice. Floxed Cxcr4 mice were provided by Y.-R. Zou (the Feinstein Institute for Medical Research). We are grateful to V. Sandler for constructive discussions.R.L., W.S., K.S., and S.R. are supported by Ansary Stem Cell Institute (ASCI), New York State Department of Health grants (NYSDOH) (C026878, C028117, C029156, C030160), NIH-R01 (DK095039, HL119872, HL128158, HL115128, HL099997) and U54 CA163167, the Starr foundation TRI-Institution stem cell core project, Tri-Institutional Stem Cell Initiative grants (TRI-SCI#2013-032, #2014-023, #2016-013, and fellowships), R.L., A.R.T., and S.R. by the Qatar National Priorities Research Program (NPRP 8-1898-3-392), B.K. by NIH-T32 HD060600. J.M.B. is supported by the ASCI, TRI-SCI #2013-022 and #2014-004, Leukemia & Lymphoma Society (LLS) grant 0859-15, and NIH-R01 (CA204308, HL133021); J.M.S by the ASCI, Taub Foundation Grants Program, TRI-SCI#2014-023 and #2016-024, LLS grant 2299-14, (NYSDOH) C029156, C030160, ECRIP, and NIH R01 (HL119872, HL128158) and by Cancer Research & Treatment Fund (CR&T). J.M.S. and S.R. by the ECRIP, NYSDOH.Supplementary Information is available in the online version of the paper.Competing interests: S.R. is the founder and a non-paid consultant to Angiocrine Bioscience. J.M.B. receives research funding from Angiocrine Bioscience, and M.G. is an employee of Angiocrine Bioscience.