Stem cells

Long before stem cells became prime subjects in immortality research, stem cells were studied for their role in normal tissue maintenance.63 The idea was that individuals were constantly refurbished by stem cells, thereby maintaining life. The constant turnover of cells in the outer layer of skin (epidermis), the inner layer of the digestive track (absorptive cells), and blood and lymphatic systems were known since World War II. At that time, the advent of radioactive elements and labeled materials (especially tritiated thymidine) had made it practical to track cellular turnover.

Diminished production of particular materials associated with some diseases (e.g., insulin and diabetes) suggested that the sufferer's primary defect

might be abnormally low concentrations of replacement-stem cells. The potential of stem cells in therapy seemed enormous, and attempts to use stem cells therapeutically were well underway in the closing decades of the twentieth century: Fetal nerve precursors were transplanted to the brains of Parkinson's disease patients, and bone marrow was transplanted to patients suffering from leukemias, lymphomas, and other cancers.64

Most of the fundamental research on stem cells was done on embryonic or embryonal stem (ES) cells obtained from mouse preembryos or blastocysts and raised in tissue culture. These cells could differentiate into virtually any adult mouse cell upon reintroduction into developing mouse blastocysts. But, in the November 6, 1998 issue of the weekly science magazine, Science, the team led by James Thomson at the University of Wisconsin with funding from Geron Corporation of Menlo Park, California, announced that it had isolated and cultured human ES cells from 20 of 36 human blastocysts left over from in vitro fertilization.65 Thus, a virtually endless supply of human stem cells became available for research.

The November 10, 1998 issue of the journal, Proceedings of the National Academy of Sciences, followed with the announcement by John Gearhart and others at The Johns Hopkins University School of Medicine,66 likewise with funding from Geron Corporation, that primordial germ cells (PGCs), or germ stem (GS) cells had been isolated and cultured from the gonadal ridges and mesenteries of 5- to 9-week post-fertilization human embryos obtained by therapeutic abortion. These cells not only proliferated in tissue culture, but differentiated into a variety of cell types, including representatives of all three embryonic germ layers.67

The Thomson/Gearhart research did more than answer the question of whether human embryos and fetuses contain stem cells. Their research demonstrated that human stem cells could be amplified in tissue culture, theoretically removing the greatest block to stem-cell replacement therapy, namely, the difficulty of obtaining sufficient quantities of high-quality stem cells. The problem of quantity had plagued attempts to re-nervate the substantia nigra of Parkinson's disease patients with dopamine producing cells.

Like the cloning of Dolly, the isolation of stem cells had been accomplished in the private sector, and Geron stock nearly doubled its value following news of the breakthroughs. The United States Congress and parliaments in many countries had driven research on human stem cells into the private sector by placing human embryos and fetuses on the proscribed list of national granting agencies.

The politics of stem-cell research is as murky as the politics of cloning. Human stem-cell research with ES cells derived from preembryos and GS cells from aborted fetuses quickly runs afoul of abortion politics. After much hand wringing, on December 19, 2000, in an open vote, the British House of

Commons approved 366 to 174 new rules allowing scientists to derive and use stem cells from human embryos and perform experiments with nuclear transfer.68 In the United States, the National Bioethics Advisory Commission recommended easing the strictures on research utilizing human embryos and fetuses.69 President Clinton partially lifted the ban on cloning and President Bush has decided to allow research utilizing ES cells, although United States scientists will not receive support from the National Institutes of Health allowing them to cull human stem cells from the detritus of in vitro fertility clinics. Of course, entrepreneurial scientists will perform human stem-cell research, and the possibility of immortality research through stem cells will soon become global business.70

Stem-cell researchers will add ways for increasing longevity with the help of cybernetic devices and electronic prostheses, performing one or another miracle and enhancing well-being for great numbers of individuals who can afford the cost of these technologies. However, stem-cell therapy as such, like other longevity-enhancing devices, only delays the inevitable, and, like cloning, is not in and of itself the long-sought cure for mortality. The panacea for aging, however, is close at hand: It lies in combining the technologies of cloning and stem-cell therapy.

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