stem cells differentiate into other cell types A stem cell has the potential to become one of many different types of cells.
Stem cells are unique cells: They have the ability to become many different types of cells, and they can replicate rapidly. Stem cells play a huge part in the body’s healing process, and the introduction of new stem cells has always showed great promise in the treatment of many conditions. It wasn’t until we found out where and how to isolate these cells that we started using them for transplants. Although a person’s own stem cells are always 100 percent compatible, there are risks in using someone else’s stem cells, especially if the donor and recipient are not immediately related. The discovery of certain markers allows us to see how compatible a donor’s and host’s cells will be. The relatively recent discovery of stem cells in the umbilical cord's blood has proven advantageous over acquiring stem cells from other sources. Researches are currently conducting clinical trials with stem cells, adding to the growing list of 80 diseases which they can treat.
Your body has many different types of cells (more than 200 to be more exact) each geared towards specific functions. You have skin cells and blood cells, and you have bone cells and brain cells. All your organs comprise specific cells, too, from kidney cells to heart cells.

Stem cells have potential

Your cells didn’t start out knowing how to come together to form your bones, heart or blood; they begun with more of a blank slate. These completely undifferentiated cells can be found during gestation, or the time the baby is in the womb, and are called embryonic stem cells. These early stage stem cells are master cells that have the potential to become any type of cell in the body.

First isolated in 1998, there is a lot of controversy around acquiring embryonic stem cells. Thankfully, we can also acquire the stem cells that form just a little bit later down the road, like in the umbillical cord tissue. These stem cells, known as adult stem cells, stay with us for life. (Later, we will learn why not all adult stem cells are equal.) Adult stem cells are more limited in the types of cells they can become, something known as being tissue-specific, but share many of the same qualities. Hematopoietic stem cells (Greek “to make blood” and pronounced he-mah-toe-po-ee-tic) found in the umbilical cord's blood, for instance, can become any of the different types of blood cells found in the body and are the foundation of our immune system. Another example is mesenchymal (meh-sen-ki-mal) stem cells, which can be found in the umbilical cord tissue and can become a host of cells including those found in your nervous system, sensory organs, circulatory tissues, skin, bone, cartilage, and more.

Stem cells proliferate

To recap, we have certain types of stem cells that can become a variety of different cells—they are like the renaissance men of cells—but there is one more thing that makes stem cells special. This has to do with how they replicate themselves.

The body has two ways to create more cells. The first is usually taught in middle school science. Known as cell division, it’s where a cell replicates within its membrane before dividing into two identical cells. Cells do this as needed for regeneration, which we will touch on in a second.

The other way the body creates more cells is through its stem cells, and stem cells do things a little differently. They undergo what is called asymmetric division, forming not one but two daughter cells: one cell often an exact replica of itself, a new stem cell with a relatively clean slate, and another stem cell that is ready to turn into a specific type of cell. This trait is known as self-renewal and allows stem cells to proliferate, or reproduce rapidly.

Through these two means, we are always producing more cells. In fact, much of your body is in a state of constant renewal because many cells can live for only certain periods of time. The lifespan for a cell in the stomach lining is about two days. Red blood cells, about four months. Nerve and brain cells are supposed to live forever. This is why these cells rarely regenerate and take a long time if they do.

Stem cells are regenerative

cord blood stem cells technician Stem cells are often extracted from cord blood and bone marrow.
Different cells have different life cycles, and many are constantly regenerating, but when damage occurs and the body needs to come up with a new supply of cells to heal itself, it relies on the stem cell’s ability to quickly create more cells to repair the wound. Herein lays the potential for the introduction of new stem cells to enhance or be the driving factor in the healing process.

Scientists first found ways to use stem cells in bone marrow, and following this discovery, the first stem cell transplant was performed in 1956 via bone marrow between identical twins. It resulted in the complete remission of the one twin’s leukemia.

This and all other stem cell therapies since involve introducing new stem cells into the area to encourage the healing process. Often, the stem cell will create a particular type of cell simply because it is in proximity to other cells of that type. Unfortunately, researchers still had a ways to go before they could use stem cells from unrelated persons.

Read more about stem cell therapies..

Stem cells need to match

The immune system has a way to identify foreign cells; it’s what allows the body to defend itself. So although transplants were proving successful after the first in 1956, they were limited to twins because their shared genetic makeup made them 100 percent compatible. This took a turn in 1958, when scientists discovered a protein present on the surface of almost all cells that lets the body know if the cell is one of its own cells or a foreign cell. In 1973, we finally learned enough about these compatibility markers (called human leukocyte antigens or HLAs) to perform the first unrelated bone marrow transplant.

The proteins stem from three HLA genes, and you inherit one HLA from each parent, or half your HLA markers from your mother and half from your father. This gives siblings a 25 percent chance of being a perfect match, a 50 percent chance of being a partial match and another one-in-four chance of not being a match at all. Unfortunately, about seven out 10 patients who need a transplant don’t have a suitable donor in their family. They can either rely on their own stem cells, isolated before treatment or previously preserved, or try to find a match through a public donor.

An HLA match helps ensure the body accepts the new cell and the transplant is successful. It also reduces the risk of graft-versus-host disease (GVHD), which is when the transplanted cells attack the recipient’s body. GVHD occurs in 30%–40% of recipients when they aren’t a perfect match but the donor is still related. If the donor and recipient are not related, it increases to a 60%–80% risk. The better the match, the more likely any GVHD symptoms will be mild, if they suffer from GVHD at all. Unfortunately, GVHD can also be deadly.

Not all adult stem cells are equal

Further advancements were made in 1978, when stem cells were discovered in cord blood and in 1988, when cord blood stem cells were first used in a transplant. Stem cells extracted from the umbilical cord blood or tissue have since been shown to be more advantageous than those extracted from other sources such as bone marrow. In many ways, this is because stem cells from the umbilical cord can be considered naïve and immature compared to stem cells from other sources. Cord stem cells haven’t been exposed to disease or environmental pollutants, and they are more accepting of foreign cells. In this case, inexperience makes them stronger.
Here are some of the ways cord blood stem cells are better than other stem cells:
  • Preserved cord stem cells are promptly available when needed.
  • Bone marrow stem cells require an invasive, surgical procedure.
  • Preserved cord stem cells are more tolerant of tissue mismatches and show a reduced incidence of graft-versus-host disease (GVHD).
  • Preserved cord stem cells have a decreased risk of transmissible viral infections.
  • Preserved cord stem cells have the ability to cross the blood–brain barrier and differentiate into neurons and other brain cells, which may be instrumental in treating some brain disorders.

Stem cells hold untapped potential

The use of hematopoietic stem cells, which can be found in the blood that remains in the vein of the umbilical cord and placenta after birth, is a proven treatment of more than 80 diseases. Mesenchymal stem cells, which can be found in the umbilical cord tissue and can become a host of cells including those found in your nervous system, sensory organs, circulatory tissues, skin, bone, cartilage, and more, are making progress in clinical trials. Some such trials show promise in treating strokes, heart disease, diabetes, autism, cerebral palsy and Alzheimer’s disease.

Read more the latest stem cell developments.