Abstract
The crucial attribute of a stem cell is its ability to differentiate into multiple tissue types. As such, it is not surprising that stem cells have attracted enormous interest because of their potential uses in regenerative medicine. The availability of cells that could grow to replace damaged or defective tissues may well revolutionize medicine, though we should not lose sight of their potential for providing an understanding of basic mechanisms of differentiation. Culture of Human Stem Cells is a practical laboratory book written by recognized experts in the field, providing clear and detailed protocols for isolating and working with human stem cells.
The first chapter, by Glyn Stacey and Jonathan Auerbach, covers important issues of quality control. After reminding us of the many embarrassing instances during the history of tissue culture where supposedly unique differentiated cell lines have proved not to be what they seemed (robust HeLa cells have been particularly troublesome in this regard, infiltrating and taking over other cell lines), the authors describe the scrupulous attention to technique and laboratory management needed to prevent contamination of stem cells by microorganisms or other cell lines. How, though, can we be certain that stem cell lines are really what we think they are? The range of assays being developed for this purpose is discussed by Stacey and Auerbach, but as they make clear there is no simple test that allows unequivocal identification of a human stem cell. At the simplest level, isoenzymes can be used to confirm that the cells are derived from the expected species. Antigenic markers are useful and widely used, though ‘embryonic stem cell markers’ are not unique for this cell type, and it is likely that gene expression arrays will be used increasingly in the future. The key characteristic of a stem cell has to be its ability to differentiate into almost any tissue in the body (pluripotent) or at least a limited number of differentiated cell types (multipotent). Because the definitive test of pluripotency (germ line competence) is clearly not acceptable for human cells, other indirect assays are described, which involve the ability to form teratomas in immunocompromised mice, generation of ‘embryoid bodies’ with the three germ layers, and differentiation in vitro into cell types representing the three germ layers.
Subsequent chapters follow a clear pattern with detailed protocols presented in a standardized format that includes lists of specialist equipment and reagents required. Five chapters deal with various aspects of cells derived from human embryos, which possess the most protean character, but which not surprisingly give rise to the greatest number of ethical problems. These chapters present methods for establishing and maintaining new lines, as well as conditions used for coaxing cells to differentiate into neural cells or cardiomyocytes. Other chapters describe isolation of stem cells from sources that present fewer ethical difficulties, but yield cells that are likely to have more limited capabilities for differentiation. The derivation of stem cells from umbilical cord blood and newborn dental pulp seem particularly promising approaches. Other chapters describe adult stem cells derived from a variety of sources including bone marrow, cornea, mammary and adipose tissue. Adult stem cells are likely to be tissue-specific and usually dormant until there is a need for repair or regeneration. They generally constitute a very small fraction of cells in any one tissue, making their isolation difficult. Nevertheless, transplantation of bone marrow stem cells is a well-established procedure, and potential applications for multipotent stem cells derived from adult tissues are not difficult to see. Some of the directions these cells can be persuaded to take (e.g. differentiation of stem cells from adipose tissue into neuronal cells) are quite unexpected for the uninitiated, however. The chapter on mammary stem cells by Labarge, Petersen and Bissell provides a good example of a system in which stem cell studies are providing insights into normal and pathological differentiation. Use of three-dimensional cultures has enabled Bissell's group to recreate mammary lobular architecture in vitro from stem cells, providing a powerful system for investigating physiological interactions between different cell types in this tissue, as well as loss of controls in mammary cancer.
With multiple traps lying in wait for the unwary, work on stem cells is not an undertaking for the faint-hearted. For those seriously thinking of taking this bold step – and for those already working on stem cells – this is a genuinely useful book full of practical advice that is presented in a clear and logical manner. Discussion of the potential uses to which stem cells may eventually be put is generally limited, however, and the interested reader would have to look elsewhere for an in-depth discussion of the complex ethical arguments that surround this topic.