Where do stem cells come from? Learn the basics of master cells to better understand their therapeutic potential.
In this article:
- An Introduction to Human Stem Cells
- Types of Stem Cells
- Where Do Stem Cells Come From?
- The Donation Process
- What Can Stem Cells Treat?
- Stem Cells for Testing New Drugs
- The Benefits of Stem Cell Transplant
- The Survival Rate of Stem Cell Therapy
Where Do Stem Cells Come From? | A Closer Look
An Introduction to Human Stem Cells
Where do stem cells come from? You have probably heard of the wonders of stem cell therapy. Not only do stem cells make research for future scientific breakthroughs possible, but they also provide the basis for many medical treatments today. So, where exactly are they from, and how are they different from regular cells? The answer depends on the types of stem cells in question.
Types of Stem Cells
There are two main types of stem cells — adult and embryonic:
- Adult stem cells – Stem cells derived from living humans.
- Embryonic stem cells – Stem cells derived from human embryos.
Beyond the two broader categories, there are sub-categories. Each has its own characteristics. For researchers, the different types of stem cells serve specific purposes.
Adult Stem Cells
Many tissues throughout the adult human body contain stem cells. Scientists previously believed adult stem cells to be inferior to human embryonic stem cells for therapeutic purposes. They did not believe adult stem cells to be as versatile as embryonic stem cells (ESCs), because they are not capable of becoming all 200 cell types within the human body.
While this theory has not been entirely disproved, encouraging evidence suggests that adult stem cells can develop into a variety of new types of cells. They can also affect repair through other mechanisms.
In August 2017, the number of stem cell publications registered in PubMed, a government database, surpassed 300,000. Stem cells are also being explored in over 4,600 cell therapy clinical trials worldwide. Some of the earliest forms of adult stem cell use include bone marrow and umbilical cord blood transplantation.
It should be noted that while the term “adult stem cell” is used for this type of cell, it is not descriptive of age, because adult stem cells can come from children. The term simply helps to differentiate stem cells derived from living humans as opposed to embryonic stem cells.
Embryonic stem cells are controversial because they are made from embryos that are created but not used by fertility clinics.
Reprogrammed Adult Stem Cells
Because adult stem cells are somewhat limited in the cell types they can become, scientists developed a way to genetically reprogram cells into what is called an induced pluripotent stem cell or iPS cell. In creating induced pluripotent stem cells, researchers hope to blend the usefulness of adult stem cells with the promise of embryonic stem cells.
Both embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs) are known as pluripotent stem cells.
Pluripotent stem cells are a type of cell that has the capacity to divide indefinitely and create any cell found within the three germ layers of an organism: ectoderm (cells forming the skin and nervous system), endoderm (cells forming pancreas, liver, endocrine gland, and gastrointestinal and respiratory tracts), and mesoderm (cells forming connective tissues, and other related tissues, muscles, bones, most of the circulatory system, and cartilage).
Embryonic stem cells can grow into a much wider range of cell types, but they also carry the risk of immune system rejection in patients. In contrast, adult stem cells are more plentiful, easier to harvest, and less controversial.
Embryonic Stem Cells
Embryonic stem cells come from embryos harvested shortly after fertilization (within 4-5 days). These cells are made when the blastocyst’s inner cell mass is transferred into a culture medium, allowing them to develop.
At 5-6 days post-fertilization, the cells within the embryo start to specialize. At this time, they no longer are able to become all of the cell types within the human body. They are no longer “pluripotent.”
Because they are pluripotent, embryonic stem cells can be used to generate healthy cells for disease patients. For example, they can be grown into heart cells known as cardiomyocytes. These cells may have the potential to be injected into an ailing patient’s heart.
Harvesting stem cells from embryos is controversial, so there are guidelines created by the National Institutes of Health (NIH) that allow the public to understand what practices are not allowed.
Perinatal Stem Cells and Umbilical Cord Stem Cells
Scientists can harvest perinatal stem cells from a variety of tissues, but the most common sources include:
- umbilical cord blood and tissue
- placental blood and tissue
- amniotic fluid and tissue
The umbilical cord attaches a mother to her fetus. It is removed after birth and is a valuable source of stem cells. The blood it contains is rich in hematopoietic stem cells (HSC). It also contains smaller quantities of another cell type known as mesenchymal stem cells (MSCs).
The placenta is a large organ that acts as a connector between the mother and the fetus. Both placental blood and tissue are also rich in stem cells.
Finally, there is amniotic fluid surrounding a baby while it is in utero. It can be harvested if a pregnant woman needs a specialized kind of test known as amniocentesis. Both amniotic fluid and tissue contain stem cells, too.
Where Do Stem Cells Come From?
Adult stem cells are usually harvested in one of three ways:
- blood draw
- tissue fat extraction (liposuction)
- bone marrow extraction
The blood draw, known as peripheral blood stem cell donation, extracts the stem cells directly from a donor’s bloodstream. The bone marrow stem cells come from deep within a bone — often a flat bone such as the hip. Tissue fat is extracted from a fatty area, such as the waist.
Embryonic donations are harvested from fertilized human eggs that are less than five days old. The embryos are not grown within a mother’s or surrogate’s womb, but instead, are multiplied in a laboratory. The embryos selected for harvesting stem cell are created within in vitro fertilization clinics but are not selected for implantation.
Amniotic stem cells can be harvested at the same time that doctors use a needle to withdraw amniotic fluid during a pregnant woman’s amniocentesis. The same fluid, after being tested to ensure the baby’s health, can also be used to extract stem cells.
As mentioned, there is another source for stem cells — the umbilical cord. Blood cells from the umbilical cord can be harvested after a baby’s birth. Cells can also be extracted from the postpartum human placenta, which is typically discarded as medical waste following childbirth.
The umbilical cord and the placenta are non-invasive sources of perinatal stem cells.
The Donation Process
People who donate stem cells through the peripheral blood stem cell donor procedure report it to be a relatively painless procedure. Similar to giving blood, the procedure takes about four hours. At a clinic or hospital, an able medical practitioner draws the blood from the donor’s vein in one of his arms using a needle injection. The technician sends the drawn blood into a machine, which extracts the stem cells. The blood is then returned to the donor’s body via a needle injected into the other arm. Some patients experience cramping or dizziness, but overall, it’s considered a painless procedure.
If a blood stem cell donor has a problem with his or her veins, a catheter may be injected in the neck or chest. The donor receives local anesthesia when a catheter-involved donation occurs.
During a bone marrow stem cell donor procedure, the donor is put under heavy sedation in an operating room. The hip is often the site chosen to harvest the bone marrow. More of the desired red marrow is found in flat bones, such as those in the pelvic region. The procedure takes up to two hours, with several extractions made while the patient is sedated. Although the procedure is painless due to sedation, recovery can take a couple of weeks.
Bone marrow stem cell donation takes a toll on the donor because it involves the extraction of up to 10 percent of the donor’s marrow. During the recovery period, the donor’s body gradually replenishes the marrow. Until that happens, the donor may feel fatigued and sore.
Some clinics offer regenerative and cosmetic therapies using the patient’s own stem cells derived from the fat tissue located on the sides of the waistline. Considered a simple procedure, clinics do this for therapeutic reasons or as a donation for research.
What Can Stem Cells Treat?
Stem cells differ from the trillions of other cells in your body. In fact, stem cells make up only a small fraction of the total cells in your body. Some people have a higher percentage of stem cells than others. But, stem cells are special because they are the “mothers” from which specialized cells grew and developed within us. When these cells divide, they become “daughters.” Some daughter cells simply self-replicate, while others form new kinds of cells altogether. This is the main way stem cells differ from other body cells — they are the only ones capable of generating new cells.
The ways in which stem cells can directly treat patients grow each year. Regenerative medicine now relies heavily on stem cell applications. This type of treatment replaces diseased cells with new, healthy ones generated through donor stem cells. The donor can be another person or the patient themselves.
Sometimes, stem cells also exert therapeutic effects by traveling through the bloodstream to sites that need repair or by impacting their micro-environment through signaling mechanisms.
Some types of adult stem cells, like mesenchymal stem cells (MSCs), are well-known for exerting anti-inflammatory and anti-scarring effects. MSCs can also positively impact the immune system.
Conditions and diseases which stem cell regeneration therapy may help include Alzheimer’s disease, Parkinson’s disease, and multiple sclerosis (MS). Heart disease, certain types of cancer, and stroke victims may also benefit in the future. Stem cell transplant promises advances in treatment for diabetes, spinal cord injury, severe burns, and osteoarthritis.
Stem Cells for Testing New Drugs
Researchers also utilize stem cells to test new drugs. In this case, an unhealthy tissue replicates into a larger sample. This method enables researchers to test various therapies on a diseased sample, rather than on an ailing patient.
Stem cell research also allows scientists to study how both healthy and diseased tissue grows and mutates under various conditions. They do this by harvesting stem cells from the heart, bones, and other body areas and studying them under intensive laboratory conditions. In this way, they get a better understanding of the human body, whether healthy or sick.
The Benefits of Stem Cell Transplant
With the following stem cell transplant benefits, it’s not surprising people would like to try the therapy as another treatment option.
- No Communicable Disease Transmission
Physicians harvest stem cell from either the patient or a donor. For an autologous transplant, there is no risk of transferring any disease from another person. For an allogeneic transplant, the donor is meticulously screened before the therapy to make sure they are compatible with the patient and have healthy sources of stem cells.
- No Risk of Rejection for Autologous Transplant
One common and serious problem of transplants is the risk of rejecting the transplanted organs, tissues, stem cells, and others. With autologous stem cell therapy, the risk is avoided primarily because it comes from the same person.
- Avoidance of Surgery
Because stem cell transplants are typically done through infusion or injection, the complex and complicated surgical procedure is avoided. There’s no risk of accidental cuts and scarring post-surgery.
- Minimal Recovery Time
Recovery time from surgeries and other types of treatments is usually time-consuming. With stem cell therapy, it could only take about 3 months or less to get the patient back to their normal state.
The Survival Rate of Stem Cell Therapy
As the number of stem cell treatments dramatically grew over the years, its survival rate also increased. A study published in the Journal of Clinical Oncology showed there was a significant increase in survival rate over 12 years among participants of the study. The study analyzed results from over 38,000 stem cell transplants on patients with blood cancers and other health conditions.
One hundred days following transplant, the researchers observed an improvement in the survival rate of patients with myeloid leukemia. “The significant improvements we saw across all patient and disease populations should offer patients hope and, among physicians, reinforce the role of blood stem cell transplants as a curative option for life-threatening blood cancers and other diseases.”
With the information above, people now have a better understanding of the answer to the question “Where do stem cells come from?” Stem cells are a broad topic to comprehend, and it’s better to go back to its basics to learn its mechanisms. This way, a person can have a piece of detailed knowledge about these master cells from a scientific perspective.
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