TYPES OF STEM CELLS

Hematopoietic stem cells (HSCs)
HSCs are marked by presence of CD34+ on the surface indicating pluripotency. They constitute the major fraction of the bone marrow derived stem cells. Experiments have shown that HSCs can control or even cure refractory cases of chronic inflammatory and neurodegenerative diseases by temporarily eradicating the auto-reactive cells and by resetting the aberrant immune response to self-antigens. The objective of hematopoietic stem cell therapy is to destroy the mature, long-lived, and auto-reactive immune cells and to generate a new properly functioning immune system. Studies with autoimmune diseases have indicated that these cells have an ability to permanently correct the dysfunctional immune system. These cells also have potential to form endothelial cells which are important cells in blood capillary formation, therefore also has ability to form new blood collaterals and nutrition to the damaged organ. HSC also enhance the function of resident and dysfunctional mesenchymal cells. These cells are commonly isolated from the Bone marrow and Umbilical cord blood.

Mesenchymal stem cell (MSC)
On the other hand, MSCs are multipotent stromal cells of mesodermal origin and express surface markers such as CD90, CD105, and CD73, that can differentiate into a variety of cell types, including: osteoblasts (bone cells) chondrocytes (cartilage cells), myocytes (muscle cells) and adipocytes (fat cells) and possess immune-modulatory and regenerative properties. They also synthesize and secrete multiple growth factors/cytokines (trophic factors), which can alleviate inflammatory disease process. The mesenchymal stem cells are commonly isolated from bone marrow (BM), adipose tissue, umbilical cord blood, placenta, embryo, and thymus. MSCs act as repair cells of the body is now an experimental truth. MSCs do not only constitutively secrete regenerative factors, but also produce some factors in response to stimuli.