The therapeutic potential of embryonic stem cells: A focus on stem cell stability

Most therapeutic uses of stem cells demand that large numbers of cells are maintained in a Good Manufacturing Practice (GMP) facility, and envisage the development of a master depository from which a working bank of cells can be retrieved and differentiated into an appropriate phenotype for use. Likewise for gene- and drug-discovery processes, it is assumed that stable and genetically identical cells will eventually become available in large numbers. Critical for both of these assumptions is that the stem cells are stable during periods of amplification and differentiation. This review discusses the physiological features that must be assessed to measure stem cell stability, and proposes that genomic, epigenomic and mitochondrial markers, as well as functional measures of utility, should be considered. Recent findings suggesting that the level of cell stability is not homogeneous throughout all stem cells are also discussed.