See an image of totipotent stem cell-containing human embryos above. Finally, these cells can also make the placenta and umbilical cord that are so important for development. What are pluripotent stem cells? These are the next most powerful stem cells and are sometimes called PSCs.
They can form the entire embryo of a developing organism. However, unlike totipotent cells, PSCs cannot form placenta and umbilical cord. They also cannot make totipotent stem cells. The two most well-known types of PSCs are embryonic stem cells see a primer on them here and induced pluripotent stem cells or iPS cells. You can learn more about iPS cells here. You might enjoy my video on embryonic stem cells below too.
PSCs are involved in a number of clinical trials. I expect many more trials in coming years. Multipotent stem cells make up just about all other kinds of stem cells beyond the first two types.
It is thought that most if not all of the different organs and tissue types in the human body have some population of multipotent stem cells. These are present to help maintain the tissues and in some cases respond to injury by making more cells.
There is still some debate about whether the heart has true stem cells in it or not. Where they do exist, pure adult stem cells are hard to isolate. See an image of MSCs above. There are hundreds of clinical trials ongoing with multipotent stem cells so there is real promise here.
A few have even been approved in different countries. A cautionary note. Other offerings have no living cells of any kind in them. There are risks to consider. Check out what the FDA has to say about this. For some types of therapies, for instance, adult stem cells are going to be ideally suited and they have a low risk of causing cancer as a side effect.
Instead, they will be made into more specialized cells like beta cells of the pancreas, retinal cells of the eye, or nervous system cells. Then those differentiated cells will be transplanted.
Difference between pluripotent and multipotent is confusing at present. Pluripotent stem cells imply differentiation into 3 lineages ecto-, endo- and mesoderm Multipotent stem cells has nothing to do with distinct lineages … MSCs differentiate into osteoblasts, chondrocytes and adipocytes all mesoderm lineages Similarly, HSCs differentiate into lymphocytes, neutrophils, basophils, eosinophils, platelets, RBCs Both MSCs and HSCs are lineage restricted but are termed multipotent nothing to do with pluripotent.
Come on, Admin…say it all. And how will those transplanted differentiated cells renew themselves in the many, many cases for which it will be required for a durable treatment e.
I am constantly asked to explain stem cells to people trying to understand the science of regenerative medicine ……it is not about believing or not , they exist …. What are stem cells, and what do they do? Sources Types Uses Donating and harvesting Cells in the body have specific purposes, but stem cells are cells that do not yet have a specific role and can become almost any cell that is required.
Stem cells are undifferentiated cells that can turn into specific cells, as the body needs them. Scientists and doctors are interested in stem cells as they help to explain how some functions of the body work, and how they sometimes go wrong.
In humans, the zygote is formed after the fertilization of the ovum by the sperm. Zygote is divided by mitosis , generating identical cells which later become totipotent. Zygote forms the morula, which is further divided to form the blastocyte. After the implantation of blastocyte in the endometrium, the differentiation process begins.
This stage is referred to as the embryonic stage, and it has separated two cell masses called outer trophoblast and inner cell mass. Hence, the trophoblast and the inner cell mass are differentiated from the totipotent cells in the morula. Then, inner cell mass becomes pluripotent by differentiating into three germ layers: endoderm, mesoderm, or ectoderm. These three germ layers give rise to different types of specialized cells in the body by becoming multipotent.
Therefore, the totipotent stem cells in humans are capable of differentiating into any type of a body cell; there are more than distinct types of human body cells. Figure 1: Differentiation of totipotent embryonic stem cells. A stem cell that is capable of differentiating into any of the three germ layers is considered as pluripotent.
The three germ layers are endoderm, ectoderm, and mesoderm. Each of these three germ layers is then differentiated into different organs and tissues by becoming multipotent. Multipotent cells are capable of differentiating into several types of cells which are functionally related to each other.
Endoderm gives rise to the interior stomach lining, gastrointestinal tract, and lungs. Ectoderm gives rise to epidermal tissues and the nervous system. Mesoderm gives rise to bones, muscles, and blood. However, some cells like embryonic cells and induced pluripotent stem cells iPS are completely pluripotent. The iPS are reprogrammed from adult stem cells by genetically modifying the cell in order to behave like embryonic stem cells.
They can be used to regenerate organs in vitro. Some are partially pluripotent, though they are capable of forming three germ layers. Regeneration of organs using iPS is shown in figure 2.
For example, when a nerve or heart-muscle cell dies, the body often has no way to replace these highly specialized cells.
These cells do not divide in the same way as skin cells and other highly replaceable cells. There is also no supply of pluripotent cells ready to take on this role. Therfore, injuries to some organs or tissues are permanent.
Even in tissues that can heal, the healing process often creates scar tissue that impedes long-term function.
Similarly, some diseases such as type 2 diabetes and AIDS, target specific cells types, limiting their ability to replenish themselves by cell division. Stem cells provide the possibility of replenishing cells that have been damaged or lost, thereby restoring functions that the body cannot restore on its own.
This is in part how some vertebrates manage limb regeneration. Bone marrow is home to multipotent stem cells which produce blood cells, and a bone marrow transplant gives the recipient an entirely new selection of blood cells over time.
This is lifesaving for patients whose original blood cells were destroyed, such as in the aftermath of leukemia treatment. Future stem cell therapies make similar promises for other tissues. This concept hinges on the fact that stem and most other cells have the same genetic code. The code is utilized differently in different cell types.
Epigenetic modifications are used to dictate which genes are active in each unique cell type. Returning those epigenetic markers from those of a final, differentiated cell type to those of a pluripotent or even totipotent cell is known as dedifferentiation.
If successful, this would cause the cell to behave as a stem cell thereafter. The cells offer hope for a new frontier in regenerative medicine. For more information about stem cells, visit our learning center here.
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