Cell & Developmental Biology
Open Access

Stem Cell

These daughter cells either become new stem cells (self-renewal) or become specialized cells (differentiation) with a more specific function, such as blood cells.

Stem cells are special human cells that are able to develop into many different cell types. This can range from muscle cells to brain cells. In some cases, they can also fix damaged tissues. Researchers believe that stem cell-based therapies may one day be used to treat serious illnesses such as paralysis and Alzheimer disease.

Types of stem cells

Stem cells are divided into 2 main forms. They are embryonic stem cells and adult stem cells.

Embryonic stem cells. The embryonic stem cells used in research today come from unused embryos. These result from an in vitro fertilization procedure. They are donated to science. These embryonic stem cells are pluripotent. This means that they can turn into more than one type of cell.

Adult stem cells. There are 2 types of adult stem cells. One type comes from fully developed tissues such as the brain, skin, and bone marrow. There are only small numbers of stem cells in these tissues. They are more likely to generate only certain types of cells. For example, a stem cell that comes from the liver will only make more liver cells.

The second type is induced pluripotent stem cells. These are adult stem cells that have been changed in a lab to be more like embryonic stem cells. Scientists first reported that human stem cells could be changed in this way in 2006. Induced pluripotent stem cells don't seem to be different from embryonic stem cells, but scientists have not yet found one that can develop every kind of cell and tissue.

Stem cells in medicine

The only stem cells now used to treat disease are hematopoietic stem cells. These are the blood cell-forming adult stem cells found in bone marrow. Every type of blood cell in the bone marrow starts as a stem cell. Stem cells are immature cells that are able to make other blood cells that mature and function as needed.