Did you know that in bone marrow alone, humans can have between 50,000 and 200,000 stem cells?
The use and understanding of stem cells is one of the most promising medical advancements of our time because they might be able to help treat life-threatening or chronic diseases.
But where are stem cells found? Let’s find out.
What Are Stem Cells?
Before we dive in and learn about what parts of the human body contain stem cells, let’s explore why they’re important.
Stem cells have the unique ability to create “daughter cells.” These cells either become more stem cells or turn into blood cells, brain cells, heart, or bone cells.
There are four broad types of stem cells.
- Embryonic Stem Cells (ESCs): Embryonic stem cells are collected during in-vitro fertilization procedures and can become any of the 200 cell types that form a human being. They are extremely versatile stem cells that have not been exposed to environmental factors like toxins.
- Perinatal Stem Cells: Perinatal stem cells are stem cells present during the perinatal period of human development. Common types include the stem cells present within the umbilical cord blood and tissue, the placenta, and the amniotic fluid.
- Adult Stem Cells: Adult stem cells are undifferentiated cells that are present in the body after development. Among the adult stem cell types, mesenchymal stem cells and hematopoietic stem cells are the most commonly sourced and utilized.
- Induced Pluripotent Stem Cells (iPS cells): To create iPS cells, scientists use mature cells (commonly, skin or blood cells) and reverse engineer them in a lab to mimic how embryonic stem cells behave. Like embryonic stem cells, iPS cells can become any of the cells that form a complete human being.
Where Are Stem Cells Found?
While stem cells are distributed throughout the human body, they are most prevalent within specific tissues, which we’ll discuss below.
First, let’s differentiate between two leading types of adult stem cells.
- Mesenchymal Stem Cells (MSCs) have a powerful ability to exert positive effects on other nearby cells. This phenomenon is known as “paracrine signaling.” When they differentiate into other cells, they prefer to become cells of the human structural system, such as muscles, tendons, ligaments, and fat.
- Hematopoietic Stem Cells (HSCs) prefer to differentiate into cells of the blood and immune system. These cells are commonly used in bone marrow transplants to help cancer patients regenerate their immune system after chemotherapy.
Both hematopoietic stem cells (HSC) and mesenchymal stem cells (MSCs) are present in human bone marrow. This springy tissue is important for immunity, disease prevention, and stem cell development.
Since both HSCs and MSCs are located in bone marrow, multiple types of cells can be created.
New blood cells are produced within the bone marrow and contain many types of cells that support immunity. More research is needed in this area so that we can fully utilize this stem cell resource for disease prevention and treatment.
You might be wondering, where are stem cells located in my teeth? This inner part of the tooth contains mesenchymal stem cells. Teeth have three layers and the innermost layer that contains blood vessels and nerves is also home to stem cells.
It is possible to harvest these cells, which shows great promise for human health.
Umbilical Cord Blood and Tissue
MSCs and cells similar to MSCs are also present in umbilical cord tissue. Retrieving these cells is non-invasive because it can happen during the delivery of a baby. Unlike bone marrow harvesting, it doesn’t cause any pain to the patient.
HSCs are specifically located in the blood of a newborn’s umbilical cord. These cells get collected and used in the treatment of blood-related cancers. If you’re giving birth, you can choose to collect cord blood and have it frozen for your own personal use or donate it.
The stem cells found in cord blood and tissues are a direct match to the baby and often a match for other family members as well.
Stem cells have even been found in the amniotic fluid that surrounds the baby while in the womb. With so many easily assessable ways to gather stem cells during and after pregnancy, perinatal tissues represent a promising source of stem cells for use in regenerative medicine.
Adipose (Fat) Tissue
MSCs are also located in adipose, or fatty tissues. These specific cells offer new insights into how stem cells can be used for regenerative therapies.
For simplicity, the mesenchymal cells present within adipose tissue are sometimes termed adipose-derived stem cells.
However, especially with adipose stem cells, the claims about their benefits often exceed what is verified. If you’re interested in stem cell therapies be sure you have vetted the medical facility and read current science.
The placenta is what keeps babies healthy during pregnancy. It brings all the nutrients, blood and oxygen from the mother to the baby. We already know that there are stem cells in the umbilical cord, but did you also know they’re in the placentas themselves?
Placentas are delivered during labor and therefore require little additional effort to harvest stem cells. The MSCs of the placenta are a perfect match for the mother.
What Are Stem Cells Used For?
New studies emerge all the time to find unique uses for stem cells. To use them, stem cells have to be administered to a patient.
In cancer treatment, for example, chemotherapy kills even healthy cells. For this reason, chemo patients receive bone marrow transplants, which contain valuable MSCs and HSCs. These stem cells help to revitalize a patient’s immune system and revive essential functions for the body.
Since stem cells have the unique ability to repair, restore, and regenerate cells, there is so much promise as to what they can accomplish for people who suffer from disease and injury. However, the function of stem cells in the human body can affect how they should get used in medicine.
The Food and Drug Administration (FDA) is very clear on its website that there can be severe consequences to seeking stem cell treatments that are not FDA approved. Even if the cells come from your own body, that doesn’t necessarily mean they will be an effective treatment.
The Future of Stem Cells
Stem cell research is one of the most highly funded categories for new projects. Between 2009 and 2018, the National Institutes of Health have overseen over $6 billion in funding for new projects and we can only expect that number to grow.
It is possible that in our lifetime, we’ll see stem cells used in routine treatments for disease. As evidence, there have already been dozens of clinical trials approved for the use of stem cells in the treatment of COVID-19.