History[ edit ] Though the concept of stem cell niche was prevailing in vertebrates, the first characterization of stem cell niche in vivo was worked out in Drosophila germinal development. The architecture of the stem-cell niche[ edit ] By continuous intravital imaging in mice, researchers were able to explore the structure of the stem cell niche and to obtain the fate of individual stem cells SCs and their progeny over time in vivo. In particular in intestinal crypt,  two distinct groups of SCs have been identified:
Where can I get more information? What are the unique properties of all stem cells? Stem cells differ from other kinds of cells in the body. All stem cells—regardless of their source—have three general properties: Stem cells are capable of dividing and renewing themselves for long periods.
Unlike muscle cells, blood cells, or nerve cells—which do not normally replicate themselves—stem cells may replicate many times, or proliferate. A starting population of stem cells that proliferates for many months in the laboratory can yield millions of cells.
If the resulting cells continue to be unspecialized, like the parent stem cells, the cells are said to be capable of long-term self-renewal. Scientists are trying to understand two fundamental properties of stem cells that relate to their long-term self-renewal: Why can embryonic stem cells proliferate for a year or more in the laboratory without differentiating, but most adult stem cells cannot; and What are the factors in living organisms that normally regulate Biology comparison of two stem cells 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. Such information would also enable scientists to grow embryonic and non-embryonic stem cells more efficiently in the laboratory.
The specific factors and conditions that allow stem cells to remain unspecialized are of great interest to scientists. It has taken scientists many years of trial and error to learn to derive and maintain stem cells in the laboratory without them spontaneously differentiating into specific cell types.
For example, it took two decades to learn how to grow human embryonic stem cells in the laboratory following the development of conditions for growing mouse stem cells.
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.
For example, a stem cell cannot work with its neighbors to pump blood through the body like a heart muscle celland it cannot carry oxygen molecules through the bloodstream like a red blood cell.
However, unspecialized stem cells can give rise to specialized cells, including heart muscle cells, blood cells, or nerve cells.
Stem cells can give rise to specialized cells. When unspecialized stem cells give rise to specialized cells, the process is called differentiation. While differentiating, the cell usually goes through several stages, becoming more specialized at each step.
Scientists are just beginning to understand the signals inside and outside cells that trigger each step of the differentiation process. The external signals for cell differentiation include chemicals secreted by other cells, physical contact with neighboring cells, and certain molecules in the microenvironment.
Many questions about stem cell differentiation remain. For example, are the internal and external signals for cell differentiation similar for all kinds of stem cells? Can specific sets of signals be identified that promote differentiation into specific cell types?
Addressing these questions may lead scientists to find new ways to control stem cell differentiation in the laboratory, thereby growing cells or tissues that can be used for specific purposes such as cell-based therapies or drug screening.
Adult stem cells typically generate the cell types of the tissue in which they reside. For example, a blood-forming adult stem cell in the bone marrow normally gives rise to the many types of blood cells.
It is generally accepted that a blood-forming cell in the bone marrow—which is called a hematopoietic stem cell —cannot give rise to the cells of a very different tissue, such as nerve cells in the brain. Experiments over the last several years have purported to show that stem cells from one tissue may give rise to cell types of a completely different tissue.
This remains an area of great debate within the research community. This controversy demonstrates the challenges of studying adult stem cells and suggests that additional research using adult stem cells is necessary to understand their full potential as future therapies.A Brief Comparison of Plant Cell Vs.
Animal Cell Here is a comparative study of a plant cell and an animal cell, so as to have a better understanding of the similarities as well as the differences between these two types of biological structures. The study is not the last word in determining the similarity of the two types of pluripotent stem cells, says Coon, who worked on the project with UW–Madison stem-cell pioneer James Thomson, director of regenerative biology at the Morgridge Institute for Research, part of the Wisconsin Institutes for Discovery at UW–Madison.
Biology Dictionary - H to HYSTRIX: Meanings of biology terminology and abbreviations starting with the letter H.
Embryonic stem cells and fetal stem cells are two types of pluripotent cells. Induced pluripotent stem cells (iPS cells) are genetically altered adult stem cells that are induced or prompted in a laboratory to take on the characteristics of embryonic stem cells.
Human embryonic development depends on stem cells. During the course of development, cells divide, migrate, and specialize. Early in development, a group of cells called the inner cell mass (ICM) forms. possible a more exact definition of stem cells, in which they are capable of self-renewal, can differentiate into multiple lineages, and will function in vivo .