bioethics

In the 3 to 5 day old embryo, called a blastocyst, a small group of about 30 cells called the inner cell mass gives rise to the hundreds of highly specialized cells needed to make up an adult organism.

Also, scientists acknowledge that many of the tests they do use may not be good indicators of the cells' most important biological properties and functions. Nevertheless, laboratories that grow human embryonic stem cell lines use several kinds of tests. These tests include. Growing and subculturing the stem cells for many months. This ensures that the cells are capable of long-term self-renewal.

stem cells

For instance, if the starting stem cells are derived from the inner cell mass of the embryo, they can generate many cell types of the body derived from all three embryonic cell types: endoderm, mesoderm and ectoderm. Stem cells with this property are said to be pluripotent. Embryonic stem cells are one kind of pluripotent stem cell. Another cell type, embryonic germ cells are also pluripotent, but they are derived at a later stage of development.

For instance, if the starting stem cells are derived from the inner cell mass of the embryo, they can generate many cell types of the body derived from all three embryonic cell types: endoderm, mesoderm and ectoderm. Stem cells with this property are said to be pluripotent. Embryonic stem cells are one kind of pluripotent stem cell. Another cell type, embryonic germ cells are also pluripotent, but they are derived at a later stage of development.

The successful generation of an unlimited supply of dopamine neurons could make neurotransplantation widely available for Parkinson's patients at some point in the future. Scientists are trying to understand two fundamental properties of stem cells that relate to their long-term self-renewal: 1) why can embryonic stem cells proliferate for a year or more in the laboratory without differentiating, but most adult stem cells cannot; and 2) what are the factors in living organisms that normally regulate stem cell proliferation and self-renewal? Discovering the answers to these questions may make it possible to understand how cell proliferation is regulated during normal embryonic development or during the abnormal cell division that leads to cancer.

Growing cells in the laboratory is known as cell culture. Human embryonic stem cells are isolated by transferring the inner cell mass into a plastic laboratory culture dish that contains a nutrient broth known as culture medium.

stem cell research

Human embryonic germ cells, in contrast, are derived from a five- to ten-week-old fetus. Adult stem cells typically generate the cell types of the tissue in which they reside. A blood-forming adult stem cell in the bone marrow, for example, normally gives rise to the many types of blood cells such as red blood cells, white blood cells and platelets.

Therefore, an important area of research is understanding the signals in a mature organism that cause a stem cell population to proliferate and remain unspecialized until the cells are needed for repair of a specific tissue.

stem cell research

Each cycle of subculturing the cells is referred to as a passage. After six months or more, the original 30 cells of the inner cell mass yield millions of embryonic stem cells. Embryonic stem cells that have proliferated in cell culture for six or more months without differentiating, are pluripotent, and appear genetically normal, are referred to as an embryonic stem cell line.

Importantly, such information would enable scientists to grow embryonic and adult stem cells more efficiently in the laboratory. Up to Stem cells are unspecialized. One of the fundamental properties of a stem cell is that it does not have any tissue-specific structures that allow it to perform specialized functions.

Examining the chromosomes under a microscope. This is a method to assess whether the chromosomes are damaged or if the number of chromosomes has changed. It does not detect genetic mutations in the cells. Determining whether the cells can be subcultured after freezing, thawing, and replating.

embryonic stem cells

PD is caused by a progressive degeneration and loss of dopamine (DA)-producing neurons, which leads to tremor, rigidity, and hypokinesia (abnormally decreased mobility). It is thought that PD may be the first disease to be amenable to treatment using stem cell transplantation. Factors that support this notion include the knowledge of the specific cell type (DA neurons) needed to relieve the symptoms of the disease.

Stem cells with this property are said to be pluripotent. Embryonic stem cells are one kind of pluripotent stem cell. Another cell type, embryonic germ cells are also pluripotent, but they are derived at a later stage of development.

Nevertheless, laboratories that grow human embryonic stem cell lines use several kinds of tests. These tests include. Growing and subculturing the stem cells for many months. This ensures that the cells are capable of long-term self-renewal. Scientists inspect the cultures through a microscope to see that the cells look healthy and remain undifferentiated. Using specific techniques to determine the presence of surface markers that are found only on undifferentiated cells.

embryonic stem cells

Many years of detailed study of the biology of mouse stem cells led to the discovery, in 1998, of how to isolate stem cells from human embryos and grow the cells in the laboratory.

The embryos used in these studies were created for infertility purposes through in vitro fertilization procedures and when they were no longer needed for that purpose, they were donated for research with the informed consent of the donor.

Examples of such plasticity include blood cells becoming neurons, liver cells that can be made to produce insulin, and hematopoietic stem cells that can develop into heart muscle.

Therefore, in order to develop such treatments scientists are intensively studying the fundamental properties of stem cells, which include: 1) determining precisely how stem cells remain unspecialized and self renewing for many years; and 2) identifying the signals that cause stem cells to become specialized cells. This primer on stem cells is intended for anyone who wishes to learn more about the biological properties of stem cells, the important questions about stem cells that are the focus of scientific research, and the potential use of stem cells in research and in treating disease.