Patent ID: 8415158

Claim:
A method of expanding pluripotent stem cells, said method comprising a) culturing the pluripotent stem cells on a solid surface in an adherent culture in a cell medium, the cell medium comprising a basal salt nutrient solution and an ErbB3 ligand, where the cell medium is essentially free of serum, wherein the pluripotent stem cells can give rise to all three germ layers and wherein the ErbB3 ligand binds to an ErbB3 receptor, which in turn dimerizes to an ErbB2 receptor to form an ErbB2/ErbB3 heterodimer, thereby activating the tyrosine kinase activity of the ErbB2 receptor in the ErbB2/ErbB3 heterodimer; and b) maintaining the pluripotent stem cells in the adherent culture in the cell medium and in appropriate culture conditions for more than one day, wherein the cell medium is changed periodically, wherein the pluripotent stem cells proliferate and do not differentiate.