Stem Cells

Abstract

There are different types of stem cells; but all of them have two abilities in common: self-renewal and differentiation. Those abilities allow their use for stem cell transplantation—to regenerate the host’s blood-forming system. The term “stem cell” seems to have first appeared in the scientific literature in 1868, written by the German biologist Ernst Haeckel. Studies and the search for stem cells probably came up in 1945, during the aftermath of the bombings in Hiroshima and Nagasaki. People who had a prolonged period exposed to lower doses of radiation could not regenerate they hematopoiesis with white blood cells and platelets, and they died. Higher doses of radiation also killed the stem cells of the intestinal tract, resulting in more rapid death. Based on that, researchers demonstrated that doses of whole-body X-irradiation caused the same radiation syndromes and death due to hematopoietic failure approximately 2 weeks after minimum radiation exposures. Shielding a single bone or the spleen from radiation prevented those irradiation syndromes. Thereafter, researchers showed that whole-body irradiated mice could be rescued from hematopoietic failure by injecting cells from blood-forming organs such as the bone marrow. In 1956, it was demonstrated that the injected bone marrow cells directly regenerates the blood-forming system, rather than releasing factors to cause the repairing of irradiation damage. It all led to the only known treatment nowadays for hematopoietic failure following whole-body irradiation, which is the stem cell transplantation to regenerate blood-forming system in the hosts [4, 36, 46, 48].