An obvious use of stem cell research is to further the understanding of embryology. A lot of the research in this area is performed through gene knockout studies. Through these stem cell knockouts, several key genes in embryological development have been determined.
For example, a gene product called Nanog was shown to be required for stem cell pluripotency (Mitsui, 2003). Another protein, called ryanodine receptor (RyR2) is now known to be needed for developing heart myocytes to beat spontaneously (Yang, 2002). Individual discoveries such as this help form new paradigms of developmental embryology.
Stem cells serve as excellent cellular models for all types of cell-based research on many tissue types. They have the strong advantage of being a renewable, relatively homogeneous group of cells. Stem cells have assisted to elucidate structure-function relationships for everything from renal tubular physiology (Jaisser, 1998) to pancreatic cells (Herrera, 2002).
Stem cells are a good match for toxicology. Toxicology is the research into the toxic effect of various compounds or medications. Since the toxins may be harmful to humans, animal models such as mice or monkeys are the mainstay of toxicology. Animal models do suffer drawbacks: testing on some animals such as monkeys can be expensive, animals models do not precisely mirror human physiology, and some voice objections of animal cruelty (Davalia, 2004).
Stem cells offer a good alternative. For example, through organogenesis, one could test any chemical to screen for adverse effects on particular tissues. Instead of testing a new cosmetic on an animal's or human's actual skin, one could grow plates of skin and monitor for changes with application of the cosmetic. And since the organs would be of a reproducible cell line, it allows accurate comparison with control groups or competing compounds undergoing testing.
Teratogens are medications or other chemicals that have an adverse effect on a developing fetus in the womb. It is obviously difficult or impossible to perform clinical trials on humans to outrule teratogenic effects of new pharmaceuticals. Stem cells teratogen research would be a welcome addition to the current dependence on potentially unreliable animal models. Formalized in vitro stem cell teratogen tests are available (Genschow, 2000), and their findings correlate well to the embryological toxic effects in vivo (Scholz, 1999).
Moreover, stem cell research can be used to elucidate the actual mechanism of the toxic effect, helping to avoid the similar pitfall in future medications. For example, stem cells were used to show thalidomide's toxic effect was through formation of hydroxyl radicals that inhibited angiogenesis (Sauer, 2000).
Similar uses apply for pharmacology. For example, one can use a heart tissue stem cell line in vitro to reproducibly assess which medication works best to therapeutically regulate the heart beat, as well as then investigate the cellular effect of that medication to devise additional, improved drugs (Wobus, 1991).
Traditionally, most improvements in agriculture have been through hybrids and other selective breeding techniques. Since one of the world's most pressing problems is an insufficient food supply, many argue that novel approaches are required. Stem cells offer an opportunity for more rapid progression.
Since stem cells determine the end agricultural product, manipulation of the stem cell would permit pursuit of various desired outcomes such as increased hardiness against pestilence, ability to grow in desert climates, increased yield or lower cost. However, probably the example that most famously captured the public imagination is the poultry research into limb differentiation. Researchers tried to unravel the stem cell blueprint for embryonic limb development, so that the instead of a chicken having two wings and two legs, farmers could raise chickens having four drumsticks.
Many of the body's renewable cells are thought to have a slowly burning wick of reproductive capacity. The cells can divide to replace lost tissue, but in the process lose some of their ability to proliferate further. Over the years, the cumulative effect is responsible for the aging of the tissue.
Embryonic stem cells, on the other hand, have an unlimited capacity to self-replicate. The hypothetical reason why many adult body tissues have a built-in clock preventing unlimited renewal, but stem cells can renew indefinitely, is some extra protection against the body tissue cells developing into a cancerous tumor.
Understanding of how stem cells are able to continuously self-renew may lead to a more complete understanding of how the body ages, and subsequently lead to ideas on how to slow or even cease the aging of tissues (Krtolica, 2005).