Brief History of Stem Cell Research
The history of stem cell research began in the early 1960s when James Till and Ernest McCulloch and their colleagues at the University of Toronto came across reservoirs of cells in mice with the properties of stem cells: the abilities to self-renew and to differentiate into specialized cells. This discovery provided the groundwork for the 1998 development of the first embryonic stem cell lines. They found that these stem cells, which they had discovered in the bone marrow of mice, had the remarkable capacity to make all the cell types found in blood.
Researchers applied these findings to humans and so, a new history of stem cell research for therapy was born. In the late 1960s, researchers began to infuse hematopoietic stem cells from human adult bone marrow into patients to treat such blood diseases as leukemia and sickle cell anemia. They also developed more advanced techniques of harvesting hematopoietic stem cells to counteract non-Hodgkin’s lymphoma and other inherited blood disorders. In 1988, investigators introduced for the first time in the stem cell history, umbilical cord blood transplants into clinical practice. These also involved the infusion of hematopoietic stem cells into patients with diseases related to the blood.
Later (more recently), they have discovered additional stem cells that reside in such diverse tissues of the human body as brain, muscle, and skin. These sorts of stem cells have been dubbed adult stem cells, because they are found in human adults (this is a misnomer, because these cells are also found in infants, fetuses,placentas, and umbilical cord blood). Meanwhile, work continued in mice, and in 1981 scientists isolated embryonic stem cells from the inner cell mass of mouse embryos. They discovered that these cells could give rise to all the tissues that eventually make up a normal mouse, such as blood, brain, liver, kidney,and bone.
In the mid-1990s, scientists went on to derive embryonic stem cells from monkeys and found that stem cells from these primates had similar properties. The first documentation in stem cell research history, of the isolation of embryonic stem cells from human embryos, although not their culture, was by Arif Bongso and colleagues in 1994. These findings, taken together, suggested that embryonic stem cells could be used to develop new ways to repair or regenerate a wide variety of damaged cells and tissues in seriously ill patients and paved the way for the derivation and culture of human embryonic stem cells.
In 1998, James Thomson and colleagues at the University of Wisconsin announced that they had completed the first successful isolation and culture of human embryonic stem cells from five-day-old embryos. These embryos had been donated by couples who had embryos remaining after they had completed in vitro fertilization (IVF) procedures. In that same year, a group directed by John Gearhart of Johns Hopkins University isolated and cultured human embryonic germ cells (cells that can grow into sperm and eggs) from cadaveric fetuses five to nine weeks old. These fetuses had been donated for research after elective abortions.
Embryonic germ cells, they found, have properties similar to those of embryonic stem cells. These studies were of tremendous scientific interest in stem cells history, for such cells are pluripotent, meaning that they can develop into almost all of the more than 200 different known cell types of the body. Their isolation meant that scientists could study them in detail to learn how they differentiate into specific types of cells. However, embryonic germ cells have not proven as useful in research as embryonic stem cells, since they do not tend to proliferate in the same large numbers as the embryonic cells.
Therefore, when ‘‘embryonic stem cells’’ are mentioned, this is usually taken to refer to the sort of stem cells developed by Thomson rather than to human embryonic germ cells. Stem cell investigators today face the critical question of whether one of the two major sorts of human stem cells, adult or embryonic, might prove more effective in developing therapies for those with serious conditions or whether research on both should be pursued.
History of the Umbilical Cord Blood Transplantation