The present disclosure relates to a method of reducing heterogeneity in antibodies during culturing, wherein the heterogeneity is due to proportion of charge variant of the antibody. The disclosure also comprises a process of growing cells in a cell culture system that results in antibodies with the reduced heterogeneity. In one embodiment antibody heterogeneity is reduced by the addition of divalent transitional metal ions such as zinc (Zn.sup.2+) to the cell culture medium. In another embodiment antibody heterogeneity is reduced by decreasing the osmolality of the cell culture medium.

Provided are defined culture media for culturing pluripotent stem cells in a suspension culture devoid of substrate adherence, the defined culture media comprising an effective amount of a protease inhibitor; a GSK3 inhibitor and at least one agent selected from the group consisting of a protease inhibitor and a WNT3A polypeptide; a WNT3A polypeptide and a stabilizing agent thereof with the proviso that said stabilizing agent is not a lipid vesicle; and/or a GSK3 inhibitor, with the proviso that the medium is devoid of an ERK1/2 inhibitor. Also provided are cell cultures and methods of suing same.