Abstract
Induced pluripotent stem (iPS) cells have attracted attention as a promising cell source for medical treatment that could replace marrow stromal cells (MSCs) and adipose tissue-derived stem cells (ASCs). These pluripotent cells can be induced in vitro and in vivo to differentiate into various tissues and organs. The cells will be useful for regenerative medicine, cell therapy, and drug screening. Vitrification is used, as well as a rapid-freeze method, for colony-forming iPS cells. However, the method requires a high degree of technical skill. We herein report a more convenient method for freezing iPS cells in suspension. We examined the proliferation potency of cryopreserved mouse iPS cells using culture medium, 10% DMSO, 10% glycerol, 5% DMSO, 5% glycerol, 5% DMSO + 5% glycerol, cell-freezing medium-DMSO, cell-freezing medium-glycerol, Cell Banker 1, Cell Banker 1+, Cell Banker 2, and Cell Banker 3 as cryopreservation solutions. Among them, Cell Banker 3 showed the highest efficacy in terms of the proliferation of mouse iPS cells. The mouse iPS cells cryopreserved in Cell Banker 3 at -80°C for 12 months maintained a high proliferation rate and an undifferentiated status. The formation of teratomas was also examined. In conclusion, Cell Banker 3 allows for freezing of iPS cells in suspension.