Embryo Project Encyclopedia Articles

According to the US National Institutes of Health (NIH), the standard American source on stem cell research, three characteristics of stem cells differentiate them from other cell types: (1) they are unspecialized cells that (2) divide for long periods, renewing themselves and (3) can give rise to specialized cells, such as muscle and skin cells, under particular physiological and experimental conditions. When allowed to grow in particular environments, stem cells divide many times. This ability to proliferate can yield millions of stem cells over several months. As long as the stem cells remain unspecialized, meaning they lack tissue-specific structures, they are able to sustain long-term self-renewal.

Edward Donnall Thomas, an American physician and scientist, gained recognition in the scientific community for conducting the first bone marrow transplant, a pioneering form of hematopoietic stem cell transplantation (HSCT). Bone marrow transplants are considered to be the first successful example of tissue engineering, a field within regenerative medicine that uses hematopoietic stem cells (HSCs) as a vehicle for treatment. Prior to Thomas's groundbreaking work, most blood-borne diseases, including certain inherited and autoimmune diseases, were considered lethal.

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.

Tissue engineering is a field of regenerative medicine that integrates the knowledge of scientists, physicians, and engineers into the construction or reconstruction of human tissue. Practitioners of tissue engineering seek to repair, replace, maintain, and enhance the abilities of a specific tissue or organ by means of living cells. More often than not stem cells are the form of living cells used in this technology. Tissue engineering is one of the disciplines involved in translating knowledge of developmental biology into the clinical setting. One focus that this field has taken is the understanding of tissue and organ development during embryogenesis, as this knowledge will open avenues to new applications of this technology.

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.

James Alexander Thomson, affectionately known as Jamie Thomson, is an American developmental biologist whose pioneering work in isolating and culturing non-human primate and human embryonic stem cells has made him one of the most prominent scientists in stem cell research. While growing up in Oak Park, Illinois, Thomson's rocket-scientist uncle inspired him to pursue science as a career. Born on 20 December 1958, Thomson entered the nearby University of Illinois Urbana-Champaign nineteen years later as a National Merit Scholar majoring in biophysics. He became fascinated with development via the encouragement and influence of Fred Meins, one of his undergraduate professors. After graduating as a Phi Beta Kappa scholar, Thomson took his interest in biology to the University of Pennsylvania where he earned two doctorate degrees: one in veterinary medicine, completed in 1985, and the other in molecular biology, completed in 1988. It was during his graduate years that Thomson began working with embryonic stem cells.

On 2 December 2007, Science published a report on creating human induced pluripotent stem (iPS) cells from human somatic cells: "Induced Pluripotent Stem Cell Lines Derived from Human Somatic Cells." This report came from a team of Madison, Wisconsin scientists: Junying Yu, Maxim A. Vodyanik, Kim Smuga-Otto, Jessica Antosiewicz-Bourget, Jennifer L. Frane, Shulan Tian, Jeff Nie, Gudrun A. Jonsdottir, Victor Ruotti, Ron Stewart, Igor I. Slukvin, and James A. Thomson. Earlier that year Shinya Yamanaka at Kyoto University, Japan published a similar paper,"Generation of Germline-Competent Induced Pluripotent Stem Cells," in Nature. Both papers independently identified four genes used to reprogram human somatic cells to pluripotent stem cells, which are cells that have the ability to develop into any specialized cell type making up the body. The reprogrammed somatic cells were referred to as iPS cells and they exhibit fundamental qualities of human embryonic stem (ES) cells.

The discovery of hematopoietic stem cells (HSCs) provided a pioneering step in stem cell research. HSCs are a type of multipotent adult stem cell, characterized by their ability to self-renew and differentiate into erythrocyte (red blood cell) and leukocyte (white blood cell) cell lineages. In terms of function, these cells are responsible for the continual renewal of the erythrocytes, leukocytes, and platelets in the body through a process called hematopoiesis. They also play an important role in the formation of vital organs such as the liver and spleen during fetal development. The early biological knowledge obtained from the studies of HSCs established the base of knowledge for understanding other stem cell systems. In addition, these cells have a vital role in furthering stem cell research for clinical applications. Regenerative medicine is a field of medicine that has applied HSCs to the treatment of blood-borne diseases such as leukemia and lymphoma and of cancer patients undergoing chemotherapy.

Renowned physician and scientist William Harvey is best known for his accurate description of how blood circulates through the body. While his published work on the circulation of blood is considered the most important of his academic life, Harvey also made significant contributions to embryology with the publication of his book Exercitationes de Generatione Animalium in 1651. In this book he established several theories that would set the stage for modern embryology and addressed many embryological issues including conception, embryogenesis, and spontaneous generation.

John D. Gearhart is a renowned American developmental geneticist best known for leading the Johns Hopkins University research team that first identified and isolated human pluripotent stem cells from human primordial germ cells, the precursors of fully differentiated germ cells. Born in Western Pennsylvania, Gearhart lived on the family farm located in the Allegheny Mountains for the first six years of his life. After his coal-miner father died, Gearhart' s mother and younger brother stayed on the farm while he and his older brother were sent to Girard College, an all-male school for orphans located in inner city Philadelphia, Pennsylvania. Gearhart remained at the college, where he was a mediocre student, for the next ten years-1950 to 1960-while receiving his first through twelfth-grade education. After completing secondary school, he entered Pennsylvania State University, pursuing a Bachelor of Science in Biological Science with dreams of becoming the world's best pomologist.