Stem cells are unique, unspecialized cells that have the remarkable ability to develop into various different cell types such as a blood cell, a liver cell, or a muscle cell. They are also unique in the fact that prior to development in a specialized cell they can replicate themselves many times over a long period of time. This second quality is called proliferation. Another unique factor is that once a stem cell has developed into a specialized cell for some organs or tissues, the cell can regenerate itself as that specialized organ or tissue cell.
Stem cells are found in various places or sources in the human body. The two main sources are embryos and adult tissue, which can be further subdivided as below.
Embryonic – These stem cells are from human embryos that are in their earliest stages of development. These stem cells have the advantage of being able to specialize into almost any type of human cell.
Fetal – These stem cells are from a fetus that is about nine weeks of age or older. These stem cells also have the advantage of specializing into almost any type of human cell.
Umbilical Cord Blood – These stem cells are similar to adult stem cells and have a more narrow range of specializing into other cells.
Placental – These stem cells are similar to umbilical cord blood stem cells but they are found in greater numbers.
Adult – These stem cells are found in mature body tissues from infants to adults. These cells have less versatility in that they are specific to a particular organ or body tissue. That is, a “muscle” stem cell can only develop into muscle cells. In this way, various stem cells will continue to maintain and repair human tissues and organs for a lifetime.
Stem cells offer great promise to heal human beings. Unspecialized stem cells can be induced or directed by researchers to develop into a specific type of tissue or organ cell. The specialized stem cells can then regenerate and replace damaged tissues and organs given the proper conditions.
Perhaps the most important application of stem cells today is the potential for the regeneration of organs – kidneys, hearts, skin, etc. The goal is to direct stem cells to develop and replicate to create new organs and tissues for a specific person. Currently, researchers and doctors have extracted stem cells below the skin and created new skin tissue that is used to treat burn victims. Development of new organs is still some years into the future but it is a very exciting research area.
Researchers have successfully used stem cells to “grow” new blood vessels in laboratory mice. This is large step toward the goal of “growing” new blood vessels for people with vascular or cardiovascular diseases.
There is also a great deal of research being conducted to understand how stem cells might be able to treat patients with brain diseases such as Alzheimer’s and Parkinson’s. The goal is to direct stem cells to become new and healthy brain cells, replicate, and replace damaged brain cells.
Since heart disease is such a large problem in today’s world, researchers are also hoping to use stem cells to treat heart patients. The goal is similar – direct stem cells to become new and healthy heart cells, replicate, and replace damaged heart cells.
A type of stem cell called hematopoietic is found in blood, bone marrow, umbilical cord blood, and placentas. These stem cells have been used for years to treat certain diseases such as leukemia and sickle cell anemia. Research will continue to use these stem cells for various types of immunodeficiencies.