Stem cells are unspecialized cells that divide within the body and develop into different kinds of cells. These have the potential to become specialized cells with specific functions. Therefore, they are known as unspecialized cells, as they differentiate into liver cells, muscle cells, blood cells, etc. Another interesting fact is that, these cells are also known as 'undifferentiated cells'. This is because, they have not completed a specific developmental path to form a specific organ or tissue.
Category of Cells
The different types are divided or categorized according to their 'potency'. This term 'potency' is used to describe the number of types of cells a cell can develop or differentiate into.
Totipotent cells are the first type. The term 'toti' means 'whole or 'total' in Latin, and 'potent' means 'potential'. These cells are those that have not begun the process of differentiation. They have the capability to differentiate into any type of cell within the body.
Pluripotent cells are those that are almost as potent as totipotent cells. However, they have barely started the differentiation process, and are capable of developing into any other type of body cell.
Multipotent stem cells are those that have begun the process of differentiation into a general cell type. They can develop into certain type of cell in a particular group or family of cells.
There are two more stem cell types called oligopotent and unipotent, that have limited functions. The oligopotent cells can differentiate into lymphoid or myeloid cells. The unipotent produce only one cell type, that is their own. This means, a muscle stem cell will differentiate only into a muscle cell and no other cell type. However, they have the property of self-renewal, making them different from non-stem cells.
There are different sources within the body that are used in harvesting different stem cells. The three types mentioned above are located in different locations of the body. Their function differs from each other. Totipotent cells can develop into any kind of cells, and pluripotent stem cells can differentiate into over 200 different cell types of the body. Multipotent cells can form fetal tissue, cord blood, and adult stem cells.
Embryonic Stem Cells
These cells form a group of cells called an embryo. They are the first step in the development of life when a fertilized egg or zygote divides to form an embryo. These newly fertilized embryo cells after the first few cell divisions contain totipotent stem cells. They have the ability to form any kind of cell structure, and after going to gastrulation, they develop into pluripotent cells.
Fetal Stem Cells
After the 8th week of development, the embryo turns into a fetus. This fetus now develops into a kind of human form, from blastocyst embryonic stem cells. These divide and form the tissues, before it is ready for birth. These are pluripotent in nature, like the embryonic stem cells.
Umbilical Cord Stem Cells
The umbilical cord is a thread of life between the mother and the fetus. It helps in transportation of oxygen as well as nutrients from the placental to the fetus. Once the baby is born, the umbilical cord is cut off from the infant. What remains is the bellybutton on the abdomen of the baby. Umbilical cells are present in the blood of the umbilical cord. These are genetically identical to the baby, and are multipotent in nature. These cells are used in umbilical cord blood stem cell storage. These can differentiate into limited number of cell types present in the body.
Placenta Derived Stem Cells
The placenta contains 10 times as many stem cells that can be harvested through the cord blood. These are multipotent stem cells that divide into certain cell types
Adult Stem Cell
Adult stem cells are not exclusively found in the adult body. They are also present in infants and children. These are present in the developed tissues of the body. They function throughout the life of the individual, carrying out the repair and maintenance of the organs. These cells are obviously multipotent, as they can divide into the specific type of cells, based in their location.
Stem cells have a huge potential in the world of genetic engineering and embryonic stem cell research. They can be harvested and developed into different cells, helping to cure various diseases like blood cancer. They can be used to cure diseases such as Parkinson's disease, where the brain cells are destroyed, or cure multiple sclerosis, and even make a blind individual see by repairing the damage to the cornea. The possibilities are endless, and researchers are trying day and night to come up with stem cell uses to help cure different disorders.