What are stem cells?
Stem cells are small and round cells capable of renewing themselves via cell division and differentiating into a variety of specialized cell types. The two main types of mammalian stem cells are embryonic stem cells that are isolated from the inner cell mass of blastocyst, and adult stem cells that are found in adult tissues or organs. Adult stem cells function as an internal repair system for the body, replenish specialized cells, but also maintain the normal turnover of regenerative organs, such as blood, skin or intestinal tissues. The origins of adult stem cells mainly include umbilical cord blood, bone marrow, peripheral blood and adipose tissue.
1. Umbilical cord blood stem cells
Umbilical cord blood is super rich in hematopoietic stem cells that have the capability to differentiate into diverse blood cells and immune cells. Cord blood hematopoietic stem cell transplants are routinely used to treat leukemia and other disorders of the blood and immune systems. To date six thousand patients worldwide have been treated with cord blood stem cell transplants. Recently, researchers have found that stem cells from cord blood appear to be able to grow into other kinds of cells, such as muscle, blood vessels, and bone. Potentially cord blood stem cells may replace a wider range of cells and tissues than ever.
2. Bone marrow stem cells
Bone marrow contains at least two types of stem cells, hematopoietic stem cells that are capable of developing into many different blood cells in the body, and bone marrow stromal cells, also called mesenchymal stem cells, that can generate bone, cartilage, fat, and cells that support the formation of blood, and fibrous connective tissue. Bone marrow hematopoietic stem cells have been used for transplant in the clinic for decades.
3. Peripheral blood stem cells
Under normal conditions, hematopoietic stem cells are rarely seen in the blood stream.Upon administration of recombinant colony-forming factors such as granulocyte colony forming factor (G-CSF), hematopoietic stem cells can be mobilized into the peripheral blood and collected for transplantation.
4. Adipose-derived stem cells
Adipose-derived stem cells are mesenchymal stem cells contained in fat tissue and harvested from liposuction material. Similar to other origins of mesenchymal stem cells, adipose-derived stem cells possess the capability to differentiate into different cell types. Recent studies demonstrate that adipose-derived stem cells are immuno-priviledged cells that may be utilized for cell therapies in HLA-incompatible hosts. Therefore adipose-derived stem cells represent an excellent source for autologous and potentially allogeneic cell therapies.