Human Serum Albumin-Containing Xeno-Free Freezing Medium Optimized for Regenerative Medicine

Human-induced pluripotent stem (iPS) cells are expected to be used in regenerative medicine and drug toxicity tests. Earlier, human iPS cells were cryopreserved by the vitrification method because the slow freezing of human iPS cells resulted in low recovery following thawing. However, the vitrification method requires a high level of skill to rapidly prepare many frozen cell stocks. Furthermore, a dry shipper is necessary to transport the stocks of vitrified human iPS cells because simple transport of vitrified cell stocks on dry ice was impossible. Transportation using dry shippers is logistically cumbersome and expensive. In this study, we developed a new slow-freezing medium to prepare cell stocks that can be transported on dry ice without a dry shipper. This medium allowed the preparation of several stocks of frozen cells of the same lot simultaneously and their transportation on dry ice. Using human peripheral blood mononuclear cells (PBMCs) and human iPS cells, we investigated the optimal slow preservation solution. We found that a slow freezing medium containing 10% (v/v) dimethyl sulfoxide (DMSO) and 1% (v/v) human serum albumin (HSA) was optimal for cryopreservation of human PBMCs and iPS cells. This xeno-free freezing medium was shown to have the potential for application in the cryopreservation of cells used in regenerative medicine.