Stem Cell Research
Stem cells are undifferentiated, or “blank,” cells. This means they’re capable of developing into cells that serve numerous functions in different parts of the body. Most cells in the body are differentiated cells. These cells can only serve a specific purpose in a particular organ. For example, red blood cells are specifically designed to carry oxygen through the blood.
All humans start out as only one cell. This cell is called a zygote, or a fertilized egg. The zygote divides into two cells, then four cells, and so on. Eventually, the cells begin to differentiate, taking on a certain function in a part of the body. This process is called differentiation.
Stem cells are cells that haven’t differentiated yet. They have the ability to divide and make an indefinite number of copies of themselves. Other cells in the body can only replicate a limited number of times before they begin to break down. When a stem cell divides, it can either remain a stem cell or turn into a differentiated cell, such as a muscle cell or a red blood cell.
Potential uses of stem cells Since stem cells have the ability to turn into various other types of cells, scientists believe that they can be useful for treating and understanding diseases. According to the Mayo Clinic, stem cells can be used to:
- grow new cells in a laboratory to replace damaged organs or tissues
- correct parts of organs that don’t work properly
- research causes of genetic defects in cells
- research how diseases occur or why certain cells develop into cancer cells
- test new drugs for safety and effectiveness
Types of stem cells
There are several types of stem cells that can be used for different purposes. Embryonic stem cells
Embryonic stem cells come from human embryos that are three to five days old. They are harvested during a process called in-vitro fertilization. This involves fertilizing an embryo in a laboratory instead of inside the female body. Embryonic stem cells are known as pluripotent stem cells. These cells can give rise to virtually any other type of cell in the body.
Non-embryonic (adult) stem cells
Adult stem cells have a misleading name, because they are also found in infants and children. These stem cells come from developed organs and tissues in the body. They’re used by the body to repair and replace damaged tissue in the same area in which they are found.
For example, hematopoietic stem cells are a type of adult stem cell found in bone marrow. They make new red blood cells, white blood cells, and other types of blood cells. Doctors have been performing stem cell transplants, also known as bone marrow transplants, for decades using hematopoietic stem cells in order to treat certain types of cancer.
Induced pluripotent stem cells (iPSCs)
Scientists have recently discovered how to turn adult stem cells into pluripotent stem cells. These new types of cells are called induced pluripotent stem cells (iPSCs). They can differentiate into all types of specialized cells in the body. This means they can potentially produce new cells for any organ or tissue. To create iPSCs, scientists genetically reprogram the adult stem cells so they behave like embryonic stem cells.
Cord blood stem cells and amniotic fluid stem cells
Cord blood stem cells are harvested from the umbilical cord after childbirth. They can be frozen in cell banks for use in the future. These cells have been successfully used to treat children with blood cancers, such as leukemia, and certain genetic blood disorders.
Stem cell research controversy
Adult stem cells don’t present any ethical problems. However, in recent years, there has been controversy surrounding the way human embryonic stem cells are obtained. During the process of harvesting embryotic stem cells, the embryo is destroyed. This raises ethical concerns for people who believe that the destruction of a fertilized embryo is morally wrong.
Opponents believe that an embryo is a living human being. They don’t think the fertilized eggs should be used for research. They argue that the embryo should have the same rights as every other human and that these rights should be protected.
With the breakthrough discovery of iPSCs, there may be less of a need for human embryos in research. This may help ease the concerns of those who are against using embryos for medical research. However, if iPSCs have the potential to develop into a human embryo, researchers could theoretically create a clone of the donor. This presents another ethical issue to take into consideration. Many countries already have legislation in place that effectively bans human cloning.
Applications of stem cell research
Neurodegeneration
Research has been conducted on the effects of stem cells on animal models of brain degeneration, such as in Parkinson’s, Amyotrophic lateral sclerosis, and Alzheimer’s disease. There have been preliminary studies related to multiple sclerosis. Healthy adult brains contain neural stem cells which divide to maintain general stem-cell numbers, or become progenitor cells. In healthy adult laboratory animals, progenitor cells migrate within the brain and function primarily to maintain neuron populations for olfaction (the sense of smell). Pharmacological activation of endogenous neural stem cells has been reported to induce neuroprotection and behavioral recovery in adult rat models of neurological disorder.
Brain and spinal cord injury
Stroke and traumatic brain injury lead to cell death, characterized by a loss of neurons and oligodendrocytes within the brain. Clinical and animal studies have been conducted into the use of stem cells in cases of spinal cord injury.
Heart
Stems cells are studied in people with severe heart disease. The work by Bodo-Eckehard Strauer was discredited by identifying hundreds of factual contradictions. Among several clinical trials reporting that adult stem cell therapy is safe and effective, actual evidence of benefit has been reported from only a few studies. Some preliminary clinical trials achieved only modest improvements in heart function following use of bone marrow stem cell therapy. Stem-cell therapy for treatment of myocardial infarction usually makes use of autologous bone marrow stem cells, but other types of adult stem cells may be used, such as adipose-derived stem cells.