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Stem cells are considered pluripotent when they can differentiate into many different kinds of specialized tissue. Heralded as invaluable for new disease therapies, standardized protocols for handling of these pluripotent stem cells need to be ascertained. By establishing best practices, optimal protocols for the cryopreservation and recovery of pluripotent stem cells can be achieved. Recently published papers in Nature Protocolsadvocate the use of BioCision’s CoolCell® alcohol-free controlled-rate freezing container in the preservation, storage, and recovery of sensitive stem cells.The ATCC also now recommends the incorporation of a CoolCell container into their iPSC stem cell handling guide.

Below is a summary of considerations when freezing down pluripotent stem cells:

1) Media used for freezing: Usually contains a cryoprotective agent, such as 10% DMSO. Serum-free protein solutions as well as standard blood-serums are also an option.

2) Dissociation method: E.g trypsinization and mechanical separation have proven to be disadvantageous in the recovery of pluripotent stem cells.  Less harsh dissociation methods such as chelating agents like EDTA show promise.

3) Type of freezing method to use: Choices range from tissue-wrapped vials in Styrofoam boxes, to isopropanol filled containers, to expensive electronically-controlled rate freezers.  The accepted standard freezing rate for stem cells to -80°C is -1°C/minute [see table below for side-by-side comparision].

4) Temperature control is critical: During the entire process from cell handling, addition of freezing media, to freezing and thawing, the cells must be maintained at pre-determined temperatures.