Novel Culture Medium using a Small-molecule Agonist of Thrombopoetin Receptor
Poster Mar 20, 2015
Hondo M1; Nishino T2; Inamura M1
Hematopoietic stem cells (HSCs), defined by their capacity to self-renew and differentiate into all blood cell lineages, can be applied for transplantation therapy. Since a large number of HSCs are required for clinical use, improvement of techniques for expansion of HSCs ex vivo is a critical issue. Several cytokines have been used for this purpose. Thrombopoietin (TPO) is an essential cytokine that regulates megakaryocyte production and HSC proliferation via activating signaling through its receptor c- MPL. We have developed a small-molecule agonist (NR-101) of c-MPL and report that human HSCs are expanded efficiently ex vivo with NR-101. Using a new small-molecule agonist NR- 102 which is related to NR-101, we produced a novel culture medium, ReproHSCTM. The cost for culture of human HSC can be reduced by using this small-molecule.
Here we demonstrated that ReproHSCTM efficiently expands human CD34+CD38- primitive hematopoietic cells in culture and thereby enhances repopulating capacity of HSCs in NOD/SCID mice. Human blood cord CD34+ cells were cultured with ReproHSCTM supplemented with only Stem Cell Factor (SCF) for 7 days. The total cell number was increased about 40-fold during culture. CD34+ cells and CD34+CD38- cells were expanded 12- fold and 8.5-fold, respectively. We then transplanted expanded cells with ReproHSCTM supplemented with SCF and flt3 ligand for 14 days into NOD/SCID mice and analyzed the SCID-repopulating CD45+ cells with flow cytometry. The expanded cells established engraftment better than the fresh CD34+ cells did. These results indicate that ReproHSCTM is a novel medium suitable for the expansion of HSCs ex vivo.