Principles of stem cell biology and cancer: future applications and therapeutics. Edited by T. Regad, T. J. Sayers and R. C. Rees. John Wiley & Sons (2015)
1. Isolation and characterization of human embryonic stem cells and future applications in tissue engineering therapies
1.2. Basic characterization of hESCs
Human ESCs typically form compact flat colonies with defined colony borders (Figure 1.2). This morphology is like that of mouse epiblast stem cells, with which hESCs share most similarity, and in contrast to that of mESCs, which form characteristic discrete domed colonies. The hESC possesses a nucleus with distinctive nucleoli and little cytoplasm when viewed by phase-contrast microscopy. These characteristics, together with colony formation, provide effective initial identification. Although hESCs dissociate readily with a variety of enzymes and protocols (i.e. low salt conditions) to disrupt cell – cell adhesion, their survival is poor, with single cell colony-forming capacity often less than 1%. For this reason, most standard passaging involves clumps or sheets of hESCs to limit apoptosis. In contrast, human embryonic germ cells (hEGCs), which are also pluripotent (Shamblott et al., 1998), form spherical colonies, which unlike hESCs are refractory to standard cell dissociation methods.
Figure 1.2. Human ESCs grow as flat colonies on a matrix or feeder cell-coated dish.