This post “What are stem cells?” is part of our SCOPE stem cells not lost in translation project. You can learn more about the project and read the other 34 languages on that page.
Stem cell definition
The human body contains hundreds of different types of cells that are important for our daily health. These cells are responsible for keeping our bodies running each day such as making our hearts beat, brains think, kidneys clean our blood, replace our skin cells as they shed off, and so on. The unique job of stem cells is to make all these other types of cells. They are the suppliers of new cells. When stem cells divide they can make more of themselves or more of other types of cells. For example, stem cells in skin can make more of themselves or they can make differentiated cells of the skin that have specific jobs of their own such as making the melanin pigment.
Why are they important for your health?
When we get injured or sick, our cells also are injured or killed. When this happens, stem cells become active. Stem cells have the job of fixing our injured tissues and of replacing other cells when they routinely die. In this way our stem cells keep us healthy and prevent us from prematurely aging. Stem cells are like our own army of microscopic doctors.
Stem cells come in many different forms. Scientists think that every organ of our body has its own specific type of stem cells. For example, our blood is made from blood (also known as hematopoietic) stem cells. However, stem cells are also present from the earliest stages of human development, and when scientists grow these, they are called “embryonic stem cells”.
What are the different kinds of stem cells?
The reason scientists are excited about embryonic stem cells is that the natural job of embryonic stem cells is to build every organ and tissue in our bodies during human development.
What this means is that embryonic stem cells, unlike adult stem cells, can be coaxed into potentially forming almost any other of the hundreds of types of human cells.
For example, while a blood stem cell can only make blood, an embryonic stem cell can make blood, bone, skin, brain, and so on.
In addition, embryonic stem cells are programmed by nature to build tissues and even organs, while adult stem cells are not.
What this means is that embryonic stem cells have a greater natural capacity to fix diseased organs.
Embryonic stem cells are made from leftover embryos from fertility treatments that are only a few days old, that were made in a dish in a laboratory, and that would otherwise be thrown away.
These embryos have 100 or less cells in the case of human ES cells.
In rarer instances ES cells can be made by somatic cell nuclear transfer.
This “cloning” process involves moving nuclei from one cell to another.
What are iPS or induced pluripotent stem cells?
Scientists and doctors are excited about this new type of stem cell called “iPS” cells. The reason we are excited is because iPS cells have almost all the same properties as embryonic stem cells, but are not made from an embryo. Thus, there are no ethical concerns with iPS cells. In addition, iPS cells are made from a patient’s own non-stem cells, meaning that iPS cells could be given back to a patient without risk of immune rejection, an important issue with any stem cell transplant.
What does the future hold for stem cell therapies?
Because by nature stem cells have the job of replacing sick or old cells, scientists have conceived the idea of using stem cells as therapies for patients with a wide variety of medical conditions. The idea here is that by giving a sick patient stem cells or differentiated cells made from stem cells, we can make use of the stem cells’ natural ability to heal to make the patient healthy again. For example, if a patient has a heart attack, by giving that patient a transplant of stem cells as a therapy our goal is to have the transplanted stem cells repair the damage to the heart. The natural populations of stem cells that we all possess have only a limited capacity to fix injuries to our bodies. Going back to the example of the heart, the heart’s own stem cells are just not up to the task of fixing the damage from a heart attack, but a transplant of millions of stem cells would be far more powerful. Therefore by giving patients transplants of stem cells we boost the body’s ability to heal beyond the capabilities of the limited number of naturally occurring stem cells. Some challenges remain to be addressed before stem cell therapies become more common including safety, as stem cells can potentially form tumors, and immune rejection. Even so, stem cells are likely to transform medicine and in perhaps just one or two decades most of us will know someone, perhaps even ourselves, who has had a stem cell transplant. Stem cells hold promise to treat most of the major diseases that people face including cancer, heart disease, Parkinson’s Disease, Multiple Sclerosis, Stroke, Huntington’s Disease, spinal cord injury, and many more.
Currently, there are few stem cell transplants available that are proven by scientists to be both safe and effective. The best example is bone marrow transplantation. However, many unproven stem cell treatments are being advertised and offered around the world. Often these treatments get a lot of attention in the media, frequently when celebrities such as sports stars get these treatments. Generally, scientists and doctors in the stem cell field caution patients against such treatments because it is unclear whether these treatments actually work and whether they are safe. Patients have died from such treatments. While it is reasonable to consider all options when facing a potentially incurable condition or disease, we recommend that you only consider such treatments as a last resort and only after talking with your personal physician.
By Paul Knoepfler
Note that you may also find this Closer Look at Stem Cells resource page very helpful.