Stem Cells

Pluripotent stem cells – These cells are like totipotent stem cells in that they can give rise to all tissue types. Unlike totipotent stem cells, however, pluripotent stem cells cannot give rise to an entire organism. On the fourth day of development, the embryo forms into two layers, an outer layer which will become the placenta, and an inner mass which will form the tissues of the developing human body. These inner cells, though they can form nearly any human tissue, cannot do so without the outer layer; so are not totipotent, but pluripotent. As these pluripotent stem cells continue to divide, they begin to specialize further.

Multipotent stem cells– As with all stem cells, these are unspecialized cells that have the ability to: Self-renew and to differentiate into specialized cells with specific functions. A multipotent stem cell can give rise to other types of cells but it is limited in its ability to differentiate. For example, multipotent blood stem cells can develop into red blood cells, white blood cells, or platelets. Bone marrow is a good example of multipotent stem cells because it contains stem cells that give rise to all blood cell types but not other cells. Adult stem cells are considered multipotent and may also be referred to as mesenchymal stem cells.

Embryonic stem cells – A human embryo is the result of a fertilized egg during the first 8 weeks of development. Embryonic stem cells are harvested from this embryo and are considered to be pluripotent stem cells.

Adipose stem cells (ASCs) – ASCs are also multipotent stem cells and can be retrieved in high number through liposuction or subcutaneous adipose tissue fragments. ASCs display properties similar to that observed in bone marrow stem cells in that they are able differentiate into bone, cartilage, other adipose tissue, and even nervous tissue.

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