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BRIEF OVERVIEW ABOUT STEM CELLS
Stem Cells have the remarkable potential to develop into many different cell types in the body during early life and growth. In addition, in many tissues they serve as a sort of internal repair system, dividing essentially without limit to replenish other cells as long as the person or animal is still alive. When a stem cell divides, each new cell has the potential either to remain a stem cell or become another type of cell with a more specialized function, such as a muscle cell, a red blood cell, or a brain cell.
Difference between embryonic stem cells and adult stem cells
Two basic factors in Stem Cell research are the difference between embryonic Stem Cells that proliferate for a year or more in the laboratory without specializing or differentiating into different types of cells and adult stem cells that cannot proliferate without differentiating.
Another baffling factor is the presence of certain triggers and regulators that control stem cell proliferation and self-renewal.
Proliferation and specialization
The property of being unspecialized also accompanies the fact that these cells can divide and renew themselves for long periods.
Normally muscles cells, nerve cells, blood cells and other specialized cells do not normally replicate themselves but Stem Cells have the capability to do so. This replication is called proliferation. Proliferation over months can give rise to millions of cells. If the resulting cells are unspecialized, self-renewal continues for long periods of time.The factors that prevent a stem cell from becoming specialized can help in increasing the effectiveness of the stem cells in proliferation.
Differentiation
When unspecialized stem cells give rise to specialized cells, the process is called differentiation. Some signals both from within and from outside the cell can trigger stem cell differentiation.
While signals within the cell are controlled by a cell's genes which are present over strands of DNA, the external signals for cell differentiation include chemicals from other cells, contact with neighboring cells and presence of certain molecules in the environment.
Other Background
Until recently, scientists primarily worked with two kinds of stem cells from animals and humans: embryonic stem cells and non-embryonic “somatic” or “adult” stem cells”. Scientists discovered ways to derive embryonic stem cells from early mouse embryos nearly 30 years ago, in 1981. The detailed study of the biology of mouse stem cells led to the discovery, in 1998, of a method to derive stem cells from human embryos and grow the cells in the laboratory. These cells are called human embryonic stem cells. The embryos used in these studies were created for reproductive purposes through in vitro fertilization procedures. When they were no longer needed for that purpose, they were donated for research with the informed consent of the donor. In 2006, researchers made another breakthrough by identifying conditions that would allow some specialized adult cells to be "reprogrammed" genetically to assume a stem cell-like state. This new type of stem cell, called induced pluripotent stem cells (iPSCs), will be discussed in a later section of this document.
Stem cells are important for living organisms for many reasons. In the 3- to 5-day-old embryo, called a blastocyst, the inner cells give rise to the entire body of the organism, including all of the many specialized cell types and organs such as the heart, lung, skin, sperm, eggs and other tissues. In some adult tissues, such as bone marrow, muscle, and brain, discrete populations of adult stem cells generate replacements for cells that are lost through normal wear and tear, injury, or disease.
Given their unique regenerative abilities, stem cells offer new potentials for treating diseases such as diabetes, and heart disease. However, much work remains to be done in the laboratory and the clinic to understand how to use these cells for cell-based therapies to treat disease, which is also referred to as regenerative or reparative medicine.
Laboratory studies of stem cells enable scientists to learn about the cells’ essential properties and what makes them different from specialized cell types. Scientists are already using stem cells in the laboratory to screen new drugs and to develop model systems to study normal growth and identify the causes of birth defects.
Research on stem cells continues to advance knowledge about how an organism develops from a single cell and how healthy cells replace damaged cells in adult organisms. Stem cell research is one of the most fascinating areas of contemporary biology, but, as with many expanding fields of scientific inquiry, research on stem cells raises scientific questions as rapidly as it generates new discoveries.
