Nat. Med. 25, 1566–1575 (2019).

Hematopoietic stem-cell (HSC) therapies require a reliable supply of specific types of stem cells. This supply, however, is limited by extensive differentiation of these cells when cultured. Hematopoietic stem and progenitor cells (HSPCs) are commonly cultured in hydrophobic flasks, as opposed to the hydrophilic in vivo conditions. These hydrophobic materials can lead to excessive production of reactive oxygen species (ROS), a trigger for HSPC differentiation, which may offer some explanation for the extensive ex vivo differentiation. Bai et al show that a super-hydrophilic, 3D zwitterionic matrix yields a substantial increase in self-renewal of HSPCs ex vivo by reducing excessive ROS production and precluding nonspecific differentiation. Using HSPCs derived from umbilical cord blood and bone marrow, they demonstrate a 73-fold increase in long-term HSC frequency and at least 24-week repopulating abilities in immunocompromised mice. The technique has potential to facilitate basic research on HSPCs, as well as clinical applications of HSC therapies.