Embryonic vs. Adult Stem Cells
Fundamentals of Adult Stem Cells
Within our bodies, the adult stem cells found in various tissues and organs function as part of our immune system. This means they primarily replace our body’s supply of life-giving and disease-fighting blood. Specifically, they differentiate into red and white blood cells and platelets.
- red blood cells: carry oxygen through our blood stream
- white blood cells: fight infection
- platelets: clot our blood when skin is cut in order to prevent profuse bleeding
When certain diseases, such as leukemia, damage our blood’s ability to replenish a healthy blood supply, transplants of healthy stem cells can be the answer. There are a few main sources of healthy stem cells that physicians turn to for transplants.
Bone marrow, the spongy material found in our bones, is the probably the richest source of adult (excluding cord blood) stem cells. Bone marrow transplants have been used to treat genetic disorders, immune system disorders and blood disorders such as aplastic anemia and leukemia.
Peripheral Blood Stem Cells
While peripheral blood is not as rich a source of stem cells, the donor can be given 'growth factor' drugs that increase the amount of stem cells. These stem cells are then separate from the donor's blood; this is called the apharesis phase.
pro: unlike bone marrow transplants, no anesthesia is used on the donor
con: there is an increased risk of graft vs. host disease (GVHD)
Umbilical Cord Blood
The first cord blood transplant was performed in 1988, and has spurred a flurry of activity in the area. Umbilical cord blood has many benefits that bone marrow transplants and peripheral blood stem cells lack. It's painless to extract, and once it's banked, it's readily available for transplant needs. There are a host of diseases that cord blood can treat, making it a leader in cell-based regenerative therapy. Because it's a source of more primitive stem cells, there is a lower risk of GVHD. Because of this lower risk, it is possible to treat patients with less perfect HLA (Human Leukocyte Antigens) matches.
Also, because the costs of cord blood transplants are lower, medical insurance companies prefer cord blood banking to bone marrow; there are even companies that will allow you to do cord blood banking for free if you meet their 'case of need' criteria (visit our company listings and information page). Lastly, you can choose whether you prefer banking your baby's cord blood or donating it to a community bank. Banking with a private company means the cord blood will be stored for your own personal use. Donating to a community bank is an act of good will; it will allow patients in need to use your baby's life-giving stem cells to treat their diseases. Community banks are also popping up throughout the country, which means you have more banks close to home. Some of these banks even give you priority to your baby's cord blood in case of your need.
While genetic diseases can be transmitted through cord blood, the cord blood bank you choose will alert you to the presence of any abnormalities they find in the blood. Another concern with cord blood is that the amount collected usually can treat a child or a small adult (approximately 110 lbs). While currently, cord blood can be stored and kept fresh for only 15 years, science is pushing the years your cord blood stays viable.
While cord blood is technically an 'adult' or 'somatic' stem cell source, it is often distinguished from the adult stem cell category. Because cord blood is a source of younger stem cells, it looms somewhere between adult stem cells and embryonic stem cells, offering the benefits of each category.
Embryonic Stem Cell Basics
Embryonic stem cells are cultured in a Petri dish using the spare fertilized eggs of in vitro fertilization (IVF). These eggs are donated with the informed consent of the donors. Many moral and ethical questions arise in embryonic stem cell research; this is especially true of fetal stem cell research, the use of older embryos. The issue lies in scientists making their own embryos from scratch for use in stem cell research.
Embryonic stem cells have the capacity to replicate themselves, a process called proliferation. At about six months, cultured embryonic stem cells have created millions of new stem cells. Embryonic stem cells can proliferate for a year or more in the laboratory.
With those countless stem cells, scientists have the potential ability to create various specialized cells. This is because embryonic stem cells are pluripotent, or they have the ability to transform into virtually any cell. Ideally, these specialized cells will be able to treat a number of diseases and disorders in the future including diabetes, Parkinson's disease, heart disease, spinal cord injuries and vision and hearing loss.
However, scientists haven't yet perfected the growing and differentiating process for embryonic stem cells. As a result, embryonic stem cells can sometimes differentiate spontaneously, which, currently, could cause serious repercussions if the stem cells were used to treat people. Throughout the world, though, there is continuous research being done on embryonic stem cells with new discoveries being made every day about how to best use these stem cells.