With all of the controversy about stem cell research that has erupted in recent years, it’s natural to have a million questions about the topic.
Where do stem cells come from? What can they be used for? Why is there such controversy?
If you’re looking for answers to these and other questions about stem cells, keep reading!
Where Do Stem Cells Come From?
Although this is a primary question that many people ask, the answer is a little complicated. First, there are two different variations of stem cells. Each variation has its own origin, uses in research and surrounding issues.
Before we dive into the two types of stem cells, you need to understand a little bit about stem cells in general.
In short, stem cells are cells from which all other specialized cells are generated. This means that stem cells are blank canvases that can be turned into any other type of cell in the body.
When stem cells divide into new cells, the resulting cells are called daughter cells. These daughter cells can either become more stem cells, in a process called self-renewal, or specialized cells such as blood cells, bone cells, liver cells, etc., in a process called differentiation.
Stem cells are the only cells in the body that have the ability to create new types of cells. Stem cells fall into two categories: adult stem cells and embryonic stem cells.
Adult Stem Cells
Adult stem cells are stem cells found in adult tissue or organs. They are found among differentiated cells. This means that if you were to take a biopsy of adult heart tissue, you may find both heart muscle cells and adult stem cells.
The main role of adult stem cells is to repair the tissue in which they are found. However, adult stem cells are found in relatively small numbers in adult tissue and, as such, have limited ability to repair tissue damage.
The term “somatic stem cells” is used interchangeably with “adult stem cells”.
Research originally led scientists to believe that adult stem cells could only give rise to similar types of cells. For example, scientists believed that stem cells found in the heart could only differentiate into more heart muscle cells. New evidence suggests that adult stem cells may be able to differentiate into any kind of cell.
Embryonic Stem Cells
Embryonic stem cells come from preimplantation-stage embryos. These embryos are between 3 and 5 days old. At that point, the embryo is called a blastocyst and contains approximately 150 cells in total.
Embryonic stem cells are pluripotent, which means that they can divide into any type of cell the body will need in the future.
Embryonic stem cells are considered more versatile than somatic stem cells in that there is less question about the cell’s ability to differentiate into a myriad of cell types. Embryonic stem cells can be used to regenerate and repair all types of tissues and organs.
Ongoing research is trying to manipulate embryonic stem cells into differentiating into specific types of tissue or adult stem cells. If this research is successful, it will avoid the complications that arise from tissue rejection during organ transplants.
What Function Do Stems Cells Play?
As touched on above, the role of stem cells is to repair and regenerate diseased or damaged cells in the body.
Stem cells are thought to reside in a “stem cell niche” or a specific area of the tissue. Stem cells remain inactive, or quiescent until they are activated. Activation is thought to be caused by injury or damage to the tissue.
In other words, stem cells are not constantly dividing into other cells. They remain on the sidelines until called up to replace an injured player.
History of Stem Cell Research
Stem cell research is not new. In the 1950s, researchers discovered that bone marrow contained two separate types of stem cells.
One type of stem cell in the bone marrow, called hematopoietic stem cells, differentiate into blood cells. The other type of stem cell, called mesenchymal stem cells, can differentiate into bone, cartilage or other types of cell that support the formation of blood and connective tissues.
In the 1960s, scientists discovered stem cells in rat brains. Ongoing research in the 1990s convinced the scientific community that the human brain does, in fact, contain stem cells that can differentiate into any of the brain’s three cell types.
The Stem Cell Controversy
Whenever there is controversy about stem cell research, the controversy typically surrounds embryonic stem cell research in particular.
Embryonic stem cells are viewed as having greater value to future research because they are more readily accepted as being able to differentiate into all types of cells. New research into somatic stem cells may be changing this idea if it can be proven that somatic stem cells also maintain the ability to differentiate into all types of cells.
However, adult stem cells may contain abnormalities due to environmental conditions or replication errors that embryonic stem cells do not contain. Only more research can prove if adult stem cells can be used in place of embryonic stem cells.
The controversy with embryonic stem cell research comes from the fact that the cells have to be extracted from human embryos. This raises concerns and questions about the ethics of embryonic stem cell research.
In 2009, the National Institute of Health issued guidelines for human stem cell research. These guidelines sought to assuage fears that embryos were being unnecessarily destroyed or used without proper permission.
The Future of Stem Cell Research
Stem cell research has mainly focused on organ transplants. In fact, for the past 40 years, adult hematopoietic stem cells have been transplanted successfully. This is commonly known as bone marrow transplants.
Other areas of transplant research have focused on adult stem cells found in the brain and heart. If researchers can control the differentiation of these cells, it could lead to massive breakthroughs in transplantation therapies. Scientists are working on means to “grow” stem cells outside of the body in order to rapidly increase the number of stem cells.
Some other areas of study that stem cell research could inform include:
Understanding Diseases
By watching stem cells form other types of cells and mature into organs, researchers can better understand how genetic conditions and diseases develop and progress.
Regenerative Medicine
If stem cells can be manipulated into differentiating into specific cells, doctors could guide the regeneration and repair of diseased or damaged tissues.
This could benefit patients that have spinal injuries, burns, cancers, Type 1 diabetes, Parkinson’s disease, and many other types of diseases.
Regenerative medicine, which offers these services, could also benefit from the transplantation of organs or tissues grown from a patient’s own stem cells. This will alleviate the risk of rejection.
Testing Drugs
Stem cells theoretically can be used to test new drugs for safety and efficacy. Specifically, stem cells could be used in cardiac toxicity testing.
We Need More Research!
So where do stem cells come from? The answer is complicated, but also fraught with exciting new implications for medicine.
With more research comes better answers!
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