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 Stem Cells 101

What is a Stem Cell (SC)?

A stem cell is a cell that can renew itself and become other types of cells in the body.  This ability to change into other types of tissue is known as “plasticity”.

A stem cell is a primitive type of cell that can be coaxed into developing into most of the 220 types of cells found in the human body (e.g. blood cells, heart cells, brain cells, etc).  

Stem cells are unspecialized cells that have two important characteristics that distinguish them from other cells in the body. First, they can replenish their numbers for long periods through cell division. Second, after receiving certain chemical signals, they can differentiate, or transform into specialized cells with specific functions, such as a heart cell or nerve cell.


Stem Cell Classification

Stem cells are classified by the extent to which they can differentiate into different cell types.

Totipotent stem cells: Produced from the fusion of an egg and sperm cell. Cells produced by the first few divisions of the fertilised egg cell are also totipotent. These cells can grow into any type of cell without exception.   

Pluripotent stem cells: Descendants of totipotent cells and can grow into any cell type except for totipotent stem cells.   

Multipotent stem cells: Produce only cells of a closely related family of cells (e.g. blood cells such as red blood cells, white blood cells and platelets).  

Unipotent cells: Produce only one cell type, but have the property of self-renewal, which distinguishes them from non-stem cells.  

At the end of the long chain of cell divisions are "terminally differentiated" cells, such as a liver cell or lung cell, which are permanently committed to specific functions. These cells stay committed to their functions for the life of the organism or until a tumor develops. In the case of a tumor, the cells dedifferentiate, or return to a less mature state.


Types of Stem Cells

Embryonic stem cells are derived from four- to five-day-old embryos. At this stage, the embryos are spherical and are known as blastocysts.  

Adult stem cells are undifferentiated cells found in small numbers in most adult tissues. They are also found in children and can be extracted from umbilical cord blood.   Thought of as multipotent cells, the primary roles of adult stem cells are to maintain and repair the tissues in which they are found.   

Stem Cells; Embryonic and Fetal vs. Umbilical

Any references made to such things as "DNA" and/or "fingerprints" really does not apply to either type in their true and pure forms. It isn't DNA variations per se, but surface antigens, often referred to as "markers", that signal "self" from "other".  "Self" being the bodies own matter and "other" being a foreign substance.  The consensus of studies published in scientific literature is that human umbilical cord stem cells (hUCSCs) provoke little in the way of adverse reactions due to antigenic recognition by the recipient. Meaning that because they lack markers the body sees them as "self". This is why antirejection medication is not needed when doing a SCT with hUCSCs in the manner that is done by Beike.


What are the Sources of Stem Cells?

There are three sources of stem cells:

  1. Embryonic stem cells (ESCs) are derived from 4- to 5-day-old embryos. At this stage,   the embryos are spherical and are known as blastocysts. Each blastocyst consists of 50 to 150 cells and includes three structures: an outer layer of cells, a fluid-filled cavity, and a group of about 30 pluripotent cells at one end of the cavity. This latter group of cells, called the inner cell mass, form all the cells of the body.

    ESC cultures are created in the laboratory by transferring the inner cell mass from a blastocyst into a specially treated plastic culture dish. The cells divide and, after several days, begin to crowd the culture dish. When this happens, the cells are removed and   plated into several fresh culture dishes. This process is repeated many times, eventually yielding millions of ESCs.  If, after six months, the cells keep dividing without differentiating, are still pluripotent, and are genetically normal, they are referred to as an ESC line.

    The blastocysts used for creating ESC lines are derived from eggs that were fertilized in in vitro fertilization clinics but never implanted in a woman’s uterus. The resulting embryos were frozen and later donated for research purposes with the informed consent of the donors. Currently, there are over 400,000 unused frozen embryos in U.S. fertility clinics.

    Because ESCs are pluripotent and relatively easy to grow in cell culture, they are attractive candidates for use in stem cell therapies. However, just injecting ESCs into a site of injury would probably result in a tumor growing in that spot. ESCs must first be directed to differentiate into the desired cells, such as heart muscle cells, blood cells, or nerve cells. To control ESC differentiation in cell cultures, scientists try different techniques, such as changing the chemical composition of the culture medium, altering the surface of the culture dish, or inserting specific genes into the cells.

    One possible drawback to using differentiated ESC lines in stem cell therapies is that ESCs from one person might illicit an immune response when placed into another   person, because the proteins on the ESC surfaces might be viewed as foreign by the     recipient’s immune system. However, this is far from certain. ESC derivatives have been transplanted between species (for example, pigs to rats) without being rejected, so the possibility exists that ESC derivatives from one person might be safely transplanted into another person. Studies investigating this have yet to be done.  

  2. Adult stem cells are undifferentiated cells that are found in small numbers in most adult tissues. However, they are also found in children and can be extracted from umbilical cord blood. A more accurate phrase is “somatic stem cells,” although this phrase has yet  to be generally adopted.

    The primary roles of adult stem cells in the body are to maintain and repair the tissues in which they are found. They are usually thought of as multipotent cells, giving rise to a closely related family of cells within the tissue. An example is hematopoietic stem cells, which form all the various cells in the blood.  

    Recent evidence, however, indicates that some adult stem cell types may be pluripotent, or at least able to differentiate into multiple cell types. For example, hematopoietic stem cells can differentiate into neurons, glia, skeletal muscle cells, heart muscle cells, and liver cells. Whether they actually do this ordinarily within the body is unknown.

    Blood from the placenta and umbilical cord that are left over after birth is a rich source of hematopoietic stem cells. These so-called umbilical cord stem cells have been shown to be able to differentiate into bone cells and neurons, as well as the cells lining the inside of blood vessels.

    A potential advantage of using adult stem cells from a patient is that the patient’s own cells could be expanded in culture, treated to differentiate into the desired cells, and then reintroduced into the patient. The use of the patient’s own cells would eliminate any possibility that they might be rejected by the immune system. Disadvantages of using adult stem cells are that they are rare in mature tissues and it is more difficult to expand their numbers in cell culture, compared with ESCs.  

  3. Embryonic (or fetal) germ cells are pluripotent stem cells derived from so-called primordial germ cells, which are the cells that give rise to the gametes (sperm and eggs) in adults. Scientists obtain primordial germ cells from the area in a 5- to 9-week-old   embryo/fetus destined to become either the testicles or the ovaries (the dividing line between embryo and fetus is the end of the 8th week).  Like ESCs, the primordial germ cells are transferred into a specially treated plastic culture dish, where they form germ cell colonies.

    Less research has been performed using embryonic germ (EG) cells than ESCs, mostly because the embryos used for deriving EG cells are deliberately aborted, while the blastocysts used for deriving ESCs are produced through in vitro fertilization in a fertility clinic. EG cells are also difficult to maintain in cell culture because they have a tendency to differentiate spontaneously.

 
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Our mission is to educate the general public on stem cell therapies now available to treat common neurological diseases and injuries.

   
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