Stem cells are capable of dividing and renewing itself for long periods. Unlike muscle cells, blood cells, or nerve cells that are not normally replicate themselves-stem cells may replicate many times, or proliferate. From a population of stem cells that proliferates for many months in the laboratory can produce millions of cells. If the resulting cells remain unspecialized stem cells and stem 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 your long-term self renewal:
1. Why embryonic stem cells proliferate for a year or more in the laboratory without differentiating, but most embryonic stem cells can not, and
2. What are the factors in living organisms that normally regulate stem cell proliferation and self-renewal?
Discover the answers to these questions can help understand how it regulates cell proliferation during normal embryonic development or during the abnormal cell division leading to cancer.Such information will also allow scientists to grow embryonic and 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 how to obtain and maintain stem cells in the laboratory spontaneously, without differentiating into specific cell types. For example, it took two decades to learn how to grow human embryonic stem cells in the laboratory after the creation of conditions for growing mouse stem cells. Therefore, understanding the signals in a mature organism that cause a stem cell population to proliferate and remain unspecialized until the cells are needed. Such information is critical for scientists to be able to grow large numbers of unspecialized stem cells in laboratory experiments.
Stem cells are unspecialized. One of the fundamental properties of a stem cell is that they have no tissue-specific structures that allow you to perform specialized functions. For example, a stem cell can not work with its neighbors to pump blood throughout the body (like a heart muscle cell), and can not carry molecules of oxygen 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. Although differentiation, the cell normally passes through several stages, more and more specialized in each step. Scientists are beginning to understand the signals inside and outside of each stem cells that cause the differentiation process. The internal signals are controlled by genes of a cell, that are interwoven through long chains of DNA, and carry with instructions for all cellular structures and functions.The external signals for cell differentiation include chemicals secreted by other cells, physical contact with neighboring cells, and certain molecules in the microenvironment. The interaction of the signals during the differentiation of DNA causes the cell to acquire epigenetic marks that constrain the expression of DNA in the cell and can be transmitted through cell division.
Many of the questions on the differentiation of stem cells remain. For example, are internal and external signals for cell differentiation similar for all types of stem cells? Can a specific set of identification signals that promote differentiation into specific cell types? Answering 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 detection drug.
Adult stem cells typically generate the cell types of the tissue in which they reside. For example, a blood-forming adult stem cells in bone marrow normally gives rise to many types of blood cells. It is generally accepted that a blood-forming cells in bone marrow, called hematopoietic stem cells, can not give rise to cells of a very different tissue, like nerve cells in the brain. The experiments in recent years have tried to show that stem cells from one tissue can lead to cell types of a completely different tissue. This remains an area of great debate in the research community. This controversy demonstrates the challenges of studying adult stem cells and suggests that additional research with adult stem cells is necessary to fully understand their potential as future therapies.
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