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Major strides in stem cell research are starting to open up many new possibilities for medical professionals to develop new protocols to treat serious diseases and injuries.
Stem cell research is not without its share of controversy people weigh the ethical issues with scientific advancements.
What's in this Guide?
- What are stem cells?
- Where do stem cells come from?
- Why are scientists and medical professionals so interested in stem cells?
- The promise of self-healing bodies
- Stem cells and new drug testing
- Considering the ethical issues of stem cell research
- Concerns remain about taking advantage of patients
- What are the other concerns with using embryonic stem cells?
- The value and the promise of therapeutic cloning
Disclaimer: Before You Read
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What are stem cells?
Stem cells are the body’s raw materials that have the potential to develop into many different types of cells in the body.
They act as a repair system in the body and can theoretically divide without limit to replenish other cells as long as a person or animal is alive. When a stem cell divides, it creates a “daughter” cell that can either remain a stem cell (self-renewal) or become another type of cell with a more specialized function (differentiation) 1 such as a red blood cell, a bone cell, a muscle cell or a brain cell.
No other cell in the body has the natural ability to do this.
Stem cells can create daughter cells under the right conditions in the body or a laboratory which is a big part of the reason more and more emphasis is being placed on stem cell research.
Stem cells are either classified as pluripotent or multipotent 2.
Pluripotent stem cells can give rise to any type of cell in the body except those needed to support and develop a fetus in the womb.
Multipotent stem cells can give rise only to a small number of different cell types.
Where do stem cells come from?
Stem cells can come from a variety of sources. Pluripotent stem cells can be isolated from human embryos.
Embryonic stem cells come from embryos that are three to five days old 3. At this stage, an embryo is called a blastocyst and has about 150 cells.
Cells from these embryos can be used to create pluripotent stem cell "lines" —cell cultures that can be grown indefinitely in the laboratory. Pluripotent stem cell lines have also been developed from fetal tissue (older than 8 weeks of development).
More than a decade ago, scientists identified conditions that would allow some specialized adult human cells to be reprogrammed genetically to assume a stem cell-like state. These stem cells are called induced pluripotent stem cells (iPSCs) 4.
IPSCs are adult cells that have been genetically reprogrammed to an embryonic stem cell. This means they are being forced to express genes and factors important for maintaining the defining properties of embryonic stem cells.
Although these cells meet the defining criteria for pluripotent stem cells, it is not known if iPSCs and embryonic stem cells differ in clinically significant ways.
Adult stem cells have been identified in many organs and tissues. Typically, there is a very small number of multipotent stem cells in each tissue, and these cells have a limited ability to reproduce making it difficult to generate large quantities of these cells in the laboratory.
Stem cells are thought to reside in a specific area of each tissue. This area is called the stem cell niche where they may remain in a non-dividing state for many years until they are activated by a normal need for more cells, or by disease or tissue injury 5.
These cells are also called somatic stem cells.
Scientists have successfully transformed regular adult cells into stem cells using genetic reprogramming. By altering the genes in the adult cells, researchers can reprogram the cells to act similarly to embryonic stem cells.
This technique may allow researchers to use reprogrammed cells instead of embryonic stem cells and prevent immune system rejection of the new stem cells.
Researchers have also discovered stem cells in amniotic fluid and umbilical cord blood. These stem cells also have the ability to change into specialized cells.
Researchers have identified stem cells in samples of amniotic fluid drawn from pregnant women to test for abnormalities. This is a procedure called amniocentesis 6.
Why are scientists and medical professionals so interested in stem cells?
It’s not too difficult to understand why there is continued excitement and ongoing research into the study of stem cells and how the healing and regenerative properties can be unlocked for the benefit of mankind.
By observing how stem cells mature and morph into bones, blood cells, muscles, nerves and other organs and tissues, scientists how to understand better how diseases and conditions develop, and even more important, how they can be cured.
After a stem cell line is established in the body, it becomes immortal and this means that the researcher will not need to go through the rigorous procedure involved in isolating stem cells again. Once the stem cell line is isolated, it can be grown in a laboratory indefinitely and cells may be frozen for storage or distributed to other researchers.
Once these stem cell lines are grown in the laboratory, scientists can engineer them to be transplanted or used in the treatment of diseases. When healthy cells are generated to replace diseased cells, this is known as regenerative medicine 7.
What sets regenerative medicine apart from many traditional treatments and drugs is that the latter mostly treat symptoms, but regenerative medicine aims to treat the root cause of a patient's condition by replacing lost cells or organs, or by fixing a faulty gene.
The promise of self-healing bodies
Regenerative medicine has a number of practical applications including patients who could benefit from stem cell therapies if they suffer from spinal cord injuries, Parkinson’s disease, type 1 diabetes, ALS, Alzheimer’s disease, heart disease, burns, cancer, and osteoarthritis, among many others.
If a person has heart disease, stem cells could be injected into the heart muscle 8. The healthy transplanted heart muscle cells could then contribute to repairing defective heart muscle.
Researchers have already shown that adult bone marrow cells guided to become heart-like cells can repair heart tissue in people. Research in this area is ongoing.
In 2016, researchers gained wide recognition for creating a synthetic biomaterial that stimulates stem cells native to a person's own teeth. The researchers believe that this material will replace fillings, as the stem cells would prompt the damaged teeth to heal themselves 9.
Scientists are also working on ways that stem cells can be used for tissue or organ transplants. Many times, the immune system of a transplant patient will attempt to reject the transplant.
In the future, scientists may be able to modify human stem cell lines in the laboratory by using gene therapy or other techniques to overcome this immune rejection.
Until recently, researchers thought adult stem cells could create only similar types of cells. For example, researchers thought stem cells residing in the bone marrow could only generate blood cells.
Adult stem cells have been considered less viable because they are more likely to contain abnormalities due to environmental hazards, such as toxins, or from errors acquired by the cells during replication.
But new evidence suggests that adult stem cells may be able to create various types of cells. For instance, bone marrow stem cells may be able to create bone or heart muscle cells.
Scientists have also successfully transformed regular adult cells into stem cells using genetic reprogramming. By altering the genes in the adult cells, researchers can reprogram the cells to act similarly to embryonic stem cells.
Doctors have already performed stem cell transplants in the form of bone marrow transplants. Stem cells replace cells damaged by chemotherapy or disease or serve as a way for the donor's immune system to fight some types of cancer and blood-related diseases, such as leukemia, lymphoma, neuroblastoma and multiple myeloma 10.
Studies are also underway for individuals with type 1 diabetes who cannot produce insulin. Currently, daily insulin injections are required to keep blood sugar levels in check.
Regenerative medicine seeks to solve this by regenerating the islets of Langerhans, which allow the individual to make insulin. This would mean no more insulin injections and a return to normal sugar metabolism.
New techniques may allow researchers to use reprogrammed cells instead of embryonic stem cells and prevent immune system rejection of the new stem cells.
This research has led to early-stage clinical trials such as adult stem cells are currently being tested in people with neurological or heart disease.
Stem cells and new drug testing
Scientists are also using stem cells to test new drugs for safety and effectiveness. This includes the effectiveness of using human stem cells that have been programmed into tissue-specific cells to test new drugs.
For the testing of new drugs to be accurate, the cells must be programmed to acquire properties of the type of cells targeted by the drug. For example, nerve cells could be generated to test a new drug for a nerve disease.
Tests could show whether the new drug had any effect on the cells and whether the cells were harmed.
Considering the ethical issues of stem cell research
All of these advancements are exciting for the medical profession, but stem cell research is also plagued by ethical and political issues and controversy as well.
When the use of stem cells for research first started taking place in the late 1990s, scientists were taking human stem cells from embryos. When the stem cells are extracted, it means that that embryo is destroyed 11.
This created sharp ethical concerns by people with varying beliefs about when the start of human life takes place. Some people believe life starts when a baby is born while others believe that human life begins at conception, meaning they believe that an embryo has the same moral and legal rights as a human child or adult.
In 2001, President George W. Bush, who holds strong pro-life views, allowed federal National Institutes of Health (NIH) funding for stem cell research using embryonic stem cell lines already in existence at the time, while prohibiting NIH funding for the derivation or use of additional embryonic stem cell lines. It was a response to a growing sense stem cell research held great promise for understanding and treating degenerative diseases, while still opposing further destruction of human embryos.
But under President Obama’s administration, there was a partial roll back of those research restrictions. Less than two months after Obama took office, he eliminated Bush's restrictions with an executive order titled "Removing Barriers to Responsible Scientific Research Involving Human Stem Cells." 12
By 2006, scientists had already started using pluripotent stem cells. Which are not derived from embryonic stem cells.
As a result, this technique does not have the same ethical concerns.
In 2009, the NIH created guidelines for human stem cell research 13. The guidelines define embryonic stem cells and how they may be used in research and include recommendations for the donation of embryonic stem cells.
The guidelines state embryonic stem cells from embryos created by in vitro fertilization can be used only when the embryo is no longer needed.
The embryos being used in embryonic stem cell research come from eggs that were fertilized at in vitro fertilization clinics but never implanted in a woman's uterus. The stem cells are donated with informed consent from donors.
The stem cells can live and grow in special solutions in test tubes or petri dishes in laboratories.
While the moral conflict over embryonic stem cells probably won’t be resolved any time soon, recent technological progress may soon render the controversy largely moot. Advancements mean that attitudes toward stem cell research are slowly beginning to change.
For example, researchers have been able to take regular connective tissue cells and reprogram them to become functional heart cells. In studies, animals with heart failure that were injected with new heart cells experienced improved heart function and survival time.
Concerns remain about taking advantage of patients
Controversy has also taken the form of unscrupulous actors exploiting the sincere reports of the significant clinical potential of properly developed products as a way of deceiving patients and preying on the optimism of patients facing bad illnesses," according to a 2017 statement issued by FDA commissioner Dr. Scott Gottlieb.
As part of the crackdown "to prevent unscrupulous actors from being able to deceive patients and potentially harm their health," the FDA issued a warning to a stem cell clinic in Florida for "marketing stem cell products without FDA approval."
In this particular case, stem cells from fat were isolated and given to patients intravenously or injected directly into the spinal cord for a variety of conditions, despite a complete absence of scientific or medical evidence to support this type of treatment.
The clinic was also found to have failed to adhere to guidelines that intend to prevent microbial contamination when processing the stem cells, leaving patients at risk of being treated with contaminated cells.
Until such therapies are available in the United States, it is likely that many patients will continue to travel to countries like Mexico in the hope of receiving stem cell therapy that could potentially change their lives. Unfortunately, there are unscrupulous stem cell clinics world wide that offer treatments that are unsuitable for a patient’s condition.
In the end, these treatments could end up doing more harm than good, leaving patients highly vulnerable.
What are the other concerns with using embryonic stem cells?
While the use of embryonic stem cells holds great promise, there are other concerns that remain aside from social or ethical considerations.
For embryonic stem cells to be viable, researchers must be certain that the stem cells will differentiate into the specific cell types desired.
Embryonic stem cells may also grow irregularly or begin to specialize in different cell types without rhyme or reason. This spontaneous derivation is cause for concern and separate research is continuing on how to control growth and differentiation.
Another primary limitation to the possible use of embryonic stem cells in therapy is that they will likely be rejected by the recipient. There is also a concern that the stem cells might simply fail to function normally for unknown reasons, producing unknown consequences.
In an attempt to overcome this researchers are attempting to produce cloned human embryos to derive genetically near-identical stem cells for possible treatment.
The value and the promise of therapeutic cloning
Therapeutic cloning is also called somatic cell nuclear transfer. It creates versatile stem cells independent of fertilized eggs.
In this technique, the nucleus, which contains the genetic material, is removed from an unfertilized egg. The nucleus is also removed from the cell of a donor.
This donor nucleus is then injected into the egg, replacing the nucleus that was removed. This is called nuclear transfer. The egg is allowed to divide and soon forms a blastocyst.
This process creates a line of stem cells that is genetically identical to the donor's cells thus creating a clone.
There is some confusion about cloning. Reproductive cloning is the process of using cloning to create a new human being. It is opposed in many quarters as being unethical and unsafe.
Therapeutic cloning is different in that it seeks to clone only specific human cells, genes and other tissues that do not lead to the creation of another human being. Therapeutic cloning is rapidly becoming a vital part of the medical landscape with regards to breakthrough medicines, vaccines, and diagnostic testing to treat many diseases.
Therapeutic cloning could also produce replacement skin, cartilage and bone tissue for burn and accident victims, and result in ways to regenerate retinal and spinal cord tissue.
If a patient's own cells were the source of stem cells that were used to create therapeutic cells or tissues, scientists believe rejection could be avoided since the cells and tissues would genetically match their own. It could allow an individual's own cells to be used to treat or cure that person's disease, without risk of introducing foreign cells that may be rejected.
A recent example from the Biotechnology Innovation Organization offered a clear example of how this might happen.
“Suppose a middle-aged man suffers a serious heart attack while hiking in a remote part of a National Park. By the time he reaches the hospital, only a third of his heart is still working, and it is unlikely he will be able to return to his formally active life.
He provides scientists a small sample of skin cells. Technicians remove the genetic material from the cells and inject it into donated human eggs from which the chromosomes have been removed.
“These altered eggs will yield stem cells that are able to form heart muscle cells. Since they are a perfect genetic match for the patient, these cells can be transplanted into his heart without causing his immune system to reject them. They grow and replace the cells lost during the heart attack, returning him to health and strength.”
To date, therapeutic cloning in people has not been successful, although it has been in other species.
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