Embryo Project Encyclopedia

In 2006, Kazutoshi Takahashi and Shinya Yamanaka reprogrammed mice fibroblast cells, which can produce only other fibroblast cells, to become pluripotent stem cells, which have the capacity to produce many different types of cells. Takahashi and Yamanaka also experimented with human cell cultures in 2007. Each worked at Kyoto University in Kyoto, Japan. They called the pluripotent stem cells that they produced induced pluripotent stem cells (iPSCs) because they had induced the adult cells, called differentiated cells, to become pluripotent stem cells through genetic manipulation. Yamanaka received the Nobel Prize in Physiology or Medicine in 2012, along with John Gurdon, as their work showed scientists how to reprogram mature cells to become pluripotent. Takahashi and Yamanaka's 2006 and 2007 experiments showed that scientists can prompt adult body cells to dedifferentiate, or lose specialized characteristics, and behave similarly to embryonic stem cells (ESCs).

The South Korean government passed the Bioethics and Biosafety Act, known henceforth as the Bioethics Act, in 2003 and it took effect in 2005. South Korea's Ministry of Health and Welfare proposed the law to the South Korean National Assembly to allow the progress of biotechnology and life sciences research in South Korea while protecting human research subjects with practices such as informed consent. The Bioethics Act establishes a National Bioethics Committee in Seoul, South Korea. The Bioethics Act is the first law in South Korea to regulate research on embryonic stem cells and in vitro fertilization. Most South Korean bioethical policies rely on this act and its provisions.

In November 1998, two independent reports were published concerning the first isolation of pluripotent human stem cells, one of which was "Derivation of Pluripotent Stem Cells from Cultured Human Primordial Germ Cells." This paper, authored by John D. Gearhart and his research team - Michael J Shamblott, Joyce Axelman, Shunping Wang, Elizabeith M. Bugg, John W. Littlefield, Peter J. Donovan, Paul D. Blumenthal, and George R. Huggins - was published in Proceedings of the National Academy of Science soon after James A. Thomson and his research team published "Embryonic Stem Cell Lines Derived from Human Blastocysts" in Science. Gearhart 's paper suggested that pluripotent human stem cells, which have the ability to develop into all cell types that make up the body, could be derived from primordial germ cells, which are precursors of fully differentiated germ cells, isolated from embryos. At the time, Gearhart was a professor of obstetrics and gynecology at Johns Hopkins University School of Medicine. With a background in genetics, he had devoted the majority of his research to how genes regulate tissue and embryo formation. However, the successful isolation of mice embryonic stem cells encouraged Gearhart to pursue the isolation of similar cells in humans. The principal difference between human embryonic stem (ES) cells, which Thomson 's team derived, and human embryonic germ (EG) cells, which Gearhart 's team derived, is that human embryonic germ cells are derived from early germ cells. Nonetheless, they are thought to share similar properties to human embryonic stem cells.

On 9 August 2001, US President George W. Bush gave an eleven-minute speech from his ranch in Crawford, Texas, on the ethics and fate of federal funding for stem cell research. Bush also announced the creation of a special council to oversee stem cell research. In the speech President Bush acknowledged the importance of issues surrounding stem cell research to many Americans, presented different arguments in favor of and opposing embryonic stem cell research, and explained his decision to limit but not completely eliminate potential federal funding for embryonic stem cell (ESC) research. The speech was important to embryology as a field because it determined the US government's policy on funding human ESC research for the eight years of George W. Bush's administration.

Induced pluripotent stem cells (iPSCs) are studied carefully by scientists not just because they are a potential source of stem cells that circumvents ethical controversy involved with experimentation on human embryos, but also because of their unique potential to advance the field of regenerative medicine. First generated in a lab by Kazutoshi Takahashi and Shinya Yamanaka in 2006, iPSCs have the ability to differentiate into cells of all types. If scientists discover how to induce differentiated cells to return to a pluripotent state using a method that leaves the iPSCs safe for transplantation, then patients could receive stem cell transplants with cells containing their own DNA. This would presumably remove the danger of transplant rejection that comes with foreign cell transplantation.

Induced Pluripotent Stem Cells (iPSCs) are cells derived from non-pluripotent cells, such as adult somatic cells, that are genetically manipulated so as to return to an undifferentiated, pluripotent state. Research on iPSCs, initiated by Shinya Yamanaka in 2006 and extended by James Thompson in 2007, has so far revealed the same properties as embryonic stem cells (ESCs), making their discovery potentially very beneficial for scientists and ethicists alike. By avoiding the destruction of embryos and the complicated technique and resource requirements of ESCs, iPSCs may prove more practical and attractive than ESC research in the study of pluripotent stem cells.

In 1964, authors James Till, Ernest McCulloch, and Louis Siminovitch, published A Stochastic Model of Stem Cell Proliferation, Based on The Growth of Spleen Colony-Forming Cells, which discussed possible mechanisms that control stem cell division. The authors wrote the article following their experiments with spleens of irradiated mice to demonstrate the existence of stem cells, had unknown properties. In their previous experiments, Till and McCulloch noticed that many similar-looking colonies of cells formed on the spleens of irradiated mice, but those colonies had a highly variable number of stem cells. They could not explain why some stem cells gave rise to many stem cells while others only gave rise to a few. In the article, the authors propose an explanation for how stem cells divide and renew, and provide both a greater understanding as to how cancerous tissues may arise due to unchecked stem cell division as well how stem cells can aid in cancer therapy.

Shinya Yamanaka gained international prominence after publishing articles detailing the successful generation of induced pluripotent stem (iPS) cells, first in mice, then in humans. Yamanaka induced somatic cells to act like human embryonic stem cells (hESCs), allowing researchers to experiment with non-embryonic stem cells with a similar capacity as hESCs. The research involving iPS cells therefore offered new potential for research and application in medical treatment, without many of the ethical objections that hESC research entailed.

In the July 2007 issue of Nature, Keisuke Okita, Tomoko Ichisaka, and Shinya Yamanaka added to the new work on induced pluripotent stem cells (iPSCs) with their "Generation of Germline-Competent Induced Pluripotent Stem Cells" (henceforth abbreviated "Generation"). The authors begin the paper by noting their desire to find a method for inducing somatic cells of patients to return to a pluripotent state, a state from which the cell can differentiate into any type of tissue but cannot form an entire organism. If this is made possible, the authors claim, the ethical controversy surrounding the use of embryonic stem cells (ES cells) and the dangers of patient rejection of donated ES cells could be bypassed completely.

The purpose of regenerative medicine, especially tissue engineering, is to replace damaged tissue with new tissue that will allow the body to resume normal function. The uniqueness of tissue engineering is that it can restore normal structure in addition to repairing tissue function, and is often accomplished using stem cells. The first type of tissue engineering using stem cells was hematopoietic stem cell transplantation (HSCT), a surgical procedure in which hematopoietic stem cells (HSCs) are infused into a host to treat a variety of blood diseases, cancers, and immunodeficiencies. While there is a standard procedure for the infusion of these cells into a donor, variations in the sources of hematopoietic stem cells, and in the relationship between donor and recipient, do produce some variability in the procedure.