In 1998, scientists reported three separate sets of research findings related to the isolation and potential use of human embryonic stem cells.
Two of the 1998 reports were published by independent teams of scientists that had accomplished the isolation and culture of human embryonic stem cells (hereafter referred to as h ES cells) and human embryonic germ cells (hereafter referred to as h EG cells).
The report was not published in a scientific journal and therefore did not meet the higher standard of peer review, but the company claimed that its scientists had caused human somatic cells to revert to the primordial state by fusing them with cow eggs.
From this fusion product, a small clump of cells resembling ES cells appears to have been isolated (Wade, 1998).
Such a procedure was recently described by a group of Korean scientists (Hwang et al., 2004).
The advantage of using NT to derive h ES cells is that the nuclear genomes of the resulting h ES cells would be identical with those of the donors of the somatic cells.Hematopoietic (blood-forming) adult stem cells from bone marrow or from umbilical cord blood give rise to all the cells of the blood.Skin cell transplants similarly rely on the transfer of skin stem cells.In some countries there are statutory bans on the use of NT for reproductive purposes (see Chapter 4).Finally, promising research has been conducted with adult stem cells (Lanza et al., 2004; Wagers and Weissman, 2004).Other stem cells are less committed and retain the potential to differentiate into many types of cells.It is believed that stem cells also form reservoirs of repair cells to replace cells and tissues that degenerate over the life span of the organism.One report described the work of James Thomson and his co-workers at the University of Wisconsin, who derived h ES cells from a human blastocyst, comprising about 200 cells, donated by a couple that had received infertility treatments (Thomson et al., 1998).Their accomplishment was significant, because h ES cells are considered by many to be the most fundamental and extraordinary of the stem cells; unlike the more differentiated adult stem cells or other cell types, they are pluripotent.Stem cells are capable of self-renewal and also of differentiation into specialized cells.Some stem cells are more committed to a particular developmental fate than others; for example, they divide and mature into cells of a specific type or limited spectrum of types (such as heart, muscle, blood, or brain cells).