Lis, R. et al. Nature 545, 439–445 (2017).

Sugimura, R. et al. Nature 545, 432–438 (2017).

Blood research and therapeutics for blood disorders would greatly benefit from a ready source of stem and progenitor cells. Although hematopoietic stem cells (HSCs) have been produced by many routes and from many sources, they generally fail to exhibit long-term engraftment in stem-cell-depleted bone marrow or to generate functional immune cells. Sugimura et al. screened transcription factors in human pluripotent-stem-cell-derived hemogenic endothelium (a blood-producing fetal tissue) and identified a set of seven that confer HSC-like long-term engraftment in a mouse host. Lis et al. started with endothelial cells from adult mice and used a combination of four transcription factors and coculture with an inductive vascular niche to generate HSCs that exhibit long-term engraftment, as well as antigen-dependent adaptive immune function. The two studies bring the greatly anticipated prospect of cultured blood much closer to reality.