A defined serum‐free culture system for human long‐term haematopoietic stem cells

Summary Long‐term repopulating haematopoietic stem cells (LT‐HSCs) have the ability to reconstitute the entire haematopoietic system following transplantation permanently. Despite great achievements in HSC transplantation, the limited transplantable HSC number, especially LT‐HSCs, remains critical for successful transplantation and broader applications. In this study, we established a defined serum‐free culture system for in vitro expansion of LT‐HSCs. This culture system (E1) expanded LT‐HSCs from umbilical cord blood, human mobilization peripheral blood and bone marrow. These E1‐expanded HSCs reconstituted the haematopoietic and immune systems in primary and secondary transplanted mice in a short time. Better haematopoietic reconstitution was observed in secondary xenografted mice. Moreover, we obtained the comprehensive expression profile and cellular components of LT‐HSCs from umbilical cord blood. Our study provides a valuable tool for LT‐HSC research and may improve clinical applications of HSCs.