Regenerative Medicine: Stem Cells and the Science of Monstrosity.

• Position: Book Review

M. Cooper, Regenerative Medicine: Stem Cells and the Science of Monstrosity, 30J. MED. ETHICS 12 (2004).

Most accounts of the history of stem cell research tell us that embryonic stem (ES) cells were first discovered, or rather isolated and characterized in 1981. But the history of ES cells can be traced back two decades earlier to studies on teratogenesis (the production of embryonal tumors) in mice. Embryonic stem cells were first identified by the scientist Leroy Stevens in the course of his investigations into teratomas and related cancers called teratocarcinomas.

From the very beginning, then, definitions of ES cells have been inextricably entangled with the monstrous properties of teratomas, teratocarcinomas and parthenogenetic growth. The question of their precise relationship to immortal, cancerous cells has recently returned to the fore of scientific debate.

Embryonal tumors are cancers that develop without any alteration in the cell's genetic material. Tumors of this kind usually occur in the ovary or the testis and are derived from the germ cells. The more common ovarian teratoma results from a process of spontaneous parthenogenesis, in which the egg is activated to growth without fertilization, but cannot lead to a live birth. Such tumors can be benign or malignant. In their non-malignant form, they are known to as mature teratomas and are characterized by limited growth and disorganized but highly differentiated tissue.

The result is a bizarre growth known as a teratoma, a disorganized mass of cells containing many varieties of differentiated tissue--skin, bone, glandular epithelium, and so on--mixed with undifferentiated stem cells that continue to divide and generate yet more of these differentiated tissues. These truly bizarre parthenogenetic growths have been found to contain sebum, clumps of matted hair, protruding lumps of bone, cartilage, bronchial and gastro-intestinal epithelium and even teeth (a recently reported...