Mechanical Regulation of Stem Cells

Introduction Stem cells, which can self-renew and differentiate into cells with specialized functions, are usually classified as embryonic stem cells (ESCs) and adult stem cells. ESCs are derived from the inner cell mass of a blastocyst, can self-renew indefinitely, and can give rise to cell types of all somatic lineages from the three embryonic germ layers. Adult stem cells have been found in many types of tissues and organs such as bone marrow, blood, muscle, skin, intestine, fat, and brain. Bone marrow is one of the most abundant sources of adult stem cells and progenitor cells. Mesenchymal stem cells (MSCs), hematopoietic stem cells (HSCs), and endothelial progenitor cells (EPCs) can be isolated from bone marrow. These bone marrow MSCs are pluripotent stromal cells. MSCs can be expanded into billions of folds in culture, and can be stimulated to differentiate into a variety of cell types. HSCs give rise to blood cells. These cells, along with EPCs, are mobilized in response to growth factors and cytokines released upon injury in tissues and organs, and therefore can be isolated from peripheral blood in addition to the bone marrow. Both embryonic stem cells and adult stem cells have tremendous potential for cell therapy and tissue repair.