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

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.