Stem cells are the root generators of all other cells. Stem cells divide and form other cells, called daughter cells. The daughter cells can either generate new stem cells (a process called self-renewal) or can be manipulated into specialized cells (a process called differentiation) that have a specific function in certain body parts.
It is this regeneration process that makes them so promising to researchers. No other cell in the human body has the ability to generate new cells. If the secret to stimulating them in specific ways can be unlocked, a whole new toolbox of treatments to grow limbs, organs and cure diseases caused by genetic problems potentially could be developed.
The possibilities are almost like a fictional novel. Imagine a way to help those with spinal cord injuries, Parkinson’s disease, diabetes, Alzheimer’s disease, stroke, cancer, heart disease and osteoarthritis. The stem cells might also be used for burns and other skin or limb regeneration inside or outside the body.
It sounds fantastic. But there is controversy surrounding the use of certain kinds of stem cells, specifically embryonic stem cells.
Embryonic Stem Cell Controversy
As the name suggests, embryonic stem cells are obtained from embryos, the cells that form when a woman’s egg is fertilized with a man’s sperm in an in-vitro fertilization clinic. The cells that are created from that procedure but are not implanted are harvested for use in research. Because those cells are human, some question whether they should be used for experimentation.
In 2009, the National Institutes of Health issued guidelines for stem cell research in an attempt to calm objections. The directions include how stem cells can be used and how and when they are harvested. Consent from the parents is required.
While adult stem cells can be used in research, embryonic stem cells are capable of withstanding much more testing and are more flexible. Adult stem cells may not be able to produce the range of cells that embryonic stem cells can, which limits their use for research.
Ultimately, current research hopes to unlock our understanding of how diseases occur by watching how they mature and how stem cells generate healthy cells to replace those that are diseased or need to be regenerated. Stem cells are also useful to test promising new drugs for their effects, which will lead to new drugs.
New Research on the Horizon
Promising new research in adult stem cell research has shown they may have the ability to generate different types of cells. Previously, it was believed that adult stem cells could produce only similar cells. But now it is believed that unreleased cells can, in fact, create other types of cells. In one example, bone marrow cells may be able to create heart muscle cells. The research is in early clinical trials.
Regular adult cells have also been used in genetic reprogramming tests. By altering the genes, it is hoped they will take on the properties of embryonic cells. This allows their use instead of embryonic cells and may help with immune system rejection issues because the mutated cells still would belong to the original source.
So far, researchers have been able to transform connective tissue cells into functional heart cells in animals. However, it is as yet unknown whether there are long-term adverse effects from altering the adult cells. Determining that will take time and observation.
One other promising area involves perinatal stem cells. These are stem cells that have recently been discovered to reside in amniotic fluid, joining those previously discovered in umbilical cord blood cells. The amniotic fluid, which protects the fetus while it develops in the uterus, may be as effective as embryonic cells in its adaptive abilities.
Another area of intense interest is therapeutic cloning, sometimes referred to as somatic cell nuclear transfer. The process has long been talked about in science fiction as “cloning” but is close to becoming reality. This occurs when a nucleus is removed from an unfertilized egg and combined with a nucleus removed from a somatic cell of a donor. The donor nucleus is injected into the unfertilized egg, replacing the removed nucleus. The egg is then allowed to divide, forming what’s known as a blastocyst. This process is hoped to create a line of stem cells genetically identical to the donor.
Researchers believe that the stem cells derived from this therapeutic cloning process may be superior to those harvested from fertilized eggs. The therapeutic cloning cells are less likely to be rejected and may allow researchers a closer look at how diseases develop.
Unfortunately, therapeutic cloning in humans has not been successful to date, although animal clones have been created.
To date, stem cell therapy has been most successful in bone marrow transplants, in which the marrow cells have been damaged by disease or chemotherapy. Bone marrow transplants allow the immune system to fight off some forms of cancer, such as leukemia. There have also been successful tests in animals to regenerate heart cells, with hopes of human trials soon.
Future Outlook for Stem Cells
Researchers are hoping for a breakthrough way to determine that stem cells used in humans will differentiate into the specific cell types that are needed -- in other words, making sure that the embryonic cells used in the heart actually become heart cells and do not become different types of cells or grow irregularly.
There is still research to be done to solve the problems posed by the immune system’s reaction to stem cells. The new cells might be rejected, simply fail to activate or not function normally.
The good news is that billions of dollars in research funding and armies of scientists are working to solve these issues. It may only be a matter of time before a breakthrough in the lab unlocks the mysteries of stem cell function, opening a new era of treatments and cures.