Stem cells are the origin from which differentiated cells are created. They come from embryos, umbilical cord blood, and most surprising of all, in EACH TISSUE OF THE BODY. Called a “stem cell niche”, or somatic stem cells, these cells aren’t used until the need for extra cells, or when a disease or injury strikes. They can either divide to form new daughter cells, or become a specific type of cell for an explicit function, such as muscle or skin cells. (Citation 1) (Citation 2) (FIG. 210)
According to the National Institutes of Health resource for stem cell research, stem cells serve as a sort of repair system, being able to divide without limit to replendish other cells for as long as the person or animal is still alive. (Citation 2) This has obvious uses in the field of research and medicine, which can be revolutionized by the usage of stem cells.
Stem cells are the origin from which differentiated cells are created. They come from embryos, umbilical cord blood, and most surprising of all, in EACH TISSUE OF THE BODY. Called a “stem cell niche”, or somatic stem cells, these cells aren’t used until the need for extra cells, or when a disease or injury strikes. They can either divide to form new daughter cells, or become a specific type of cell for an explicit function, such as muscle or skin cells. (Citation 1) (Citation 2) (FIG. 210)
BASICS OF STEM CELLS
FIGURE 86: Totipotent stem cells can differentiate into any type of cell, as shown in this picture.
FIGURE 86: Totipotent stem cells can differentiate into any type of cell, as shown in this picture.
Stem cells are categorized by three different characteristics: totipotent, pluripotent, and multipotent, described by the sections below.
FIGURE 2: Multipotent stem cells can be used to grow and replace different kinds of tissue and cells, including: neural cells, cardiac muscle, and even blood cells!
FIGURE 3: Neuron cells, like these ones, can be grown from unspecialized stem cells.
FIGURE 5: This neuron cell was derived from multipotent stem cells.
FIGURE 2: Multipotent stem cells can be used to grow and replace different kinds of tissue and cells, including: neural cells, cardiac muscle, and even blood cells!
Categories of Stem Cells
The most flexible of all stem cells, totipotent stem cells are derived from the zygote of the combined sperm and egg cell. These cells can differentiate into any cell, even the tissues from the placenta; an upgraded version of a pluripotent stem cell. Totipotent cells can even form an entire organism! (Citation 3) (Citation 5)
Found in the tissue of adult organs, these stem cells are more limited in their ability to differentiate into specific functioning cells. According to Everyday Mysteries, "There are multipotent stem cells for all of the different types of tissue in the body." Pluripotent cells develop into the more specialized multipotent cells, which can only differentiate into a few different cell lines.
Extracted from the embryo, these types of stem cells can become any cell in the body. However, they can’t make “extra embryonic tissues” found in parts of the placenta, so they aren’t capable of reproducing a full organism. Due to these cells being derived from embryos, much controversy has been generated.
Commonly known as somatic stem cells, these stem cells are found as undifferentiated cells inside tissues and organs. Their role inside the tissue is to replace and renew dead cells in the tissue. There are three types of adult stem cells currently known today: hematopoietic stem cells, bone marrow stromal stem cells, and a relatively new type of brain stem cell. Hematopoietic stem cells have the
ADULT STEM CELLS
TYPES OF STEM CELLS
HISTORY OF STEM CELLS
iPSC STEM CELLS
EMBRYONIC STEM CELLS
ability to differentiate into any type of blood cell. Bone marrow stromal stem cells, also known as mesenchymal stem cells, are found in the bone marrow, repairing and replacing bone, cartilage, and more. Lastly, the brain stem cells differentiate into and replace astrocytes, oligodendrocytes, and neurons.
Induced pluripotent stem cells, or iPSCs for short, are basically adult stem cells that were reverted to embryonic-like pluripotent stem cells. In 2006 the first mouse iPSCs were created, and one year after that human ones were also engineered. They both had many characteristics of pluripotent cells, such as stem cell markers and forming cells from all three germ layers. These may be the most important of all three types of stem cells, because they aren’t taken from the embryo and can be made using the patient themselves.
Embryonic stem cells are taken from an embryo through in vitro fertilization, a process in which a sperm and egg join together in a lab without the use of a placenta. One way they are grown is through the use of a culture medium, such as a petri dish, in which they split and divide on the top of the petri dish. The petri dish
is then covered with mouse embryonic stem cells, called a feeder layer, so the human embryonic stem cells (hESCs) can be attached to the dish.
Embryonic stem cells can either be pluripotent or totipotent. Due to these characteristics, hESCs can give us complete knowledge of the development of the embryo into a body, new insights on the cause of disease, and new drugs and stem-cell affiliated therapy. (Citation 8)
Multipotent
Pluripotent
Totipotent
John Gurdon and Shinya Yamanaka, the scientists who discovered iPSCs, were granted the Nobel Prize In 2012. The Nobel Foundation states this is “for the discovery that mature cells can be reprogrammed to become pluripotent.” (Citation 3)(Citation 10)
Stem Cell Research has changed over the decades. See the full history of Stem Cell Research uncovered in the time line! ! Click Here
IS ALL GOOD AND WELL? CHECK THE ISSUES OF STEM CELL RESEARCH HERE!
FIGURE 1: Pluripotent Stem Cells can form most kinds of tissue, and are formed as part of the blastocyst. (Citation 23).
FIGURE 4: Pluripotent stem cells are the inner cell mass of the blastocyst.
FIGURE 1: Pluripotent Stem Cells can form most kinds of tissue, and are formed as part of the blastocyst. (Citation 23).
Just like there are three categories stem cells fall into, there are also three types of stem cells: adult, embryonic, and induced pluripotent stem cells.
