Mesenchymal stem cells: immunobiology and role in immunomodulation and tissue regeneration

Mesenchymal stem cells ( MSC) are multipotent cells that differentiate into osteoblasts, myocytes, chondrocytes and adipocytes as well as insulin-producing cells. The mechanism underlying their in vivo differentiation is not clear and is thought to be caused by spontaneous cell fusion or factors present in the microenvironment. However, their ease of isolation, high 'ex-vivo' expansion potential and ability to differentiate into multiple lineages make them attractive tools for potential use in cell therapy. MSC have been isolated from several tissues, including bone/bone marrow, fat, Wharton's jelly, umbilical cord blood, placenta and pancreas. The 'immunosuppressive' property of human MSC makes them an important candidate for cellular therapy in allogeneic settings. Use of allogeneic MSC for repair of large defects may be an alternative to autologous and allogeneic tissue-grafting procedures. An allogeneic approach would enable MSC to be isolated from any donor, expanded and cryopreserved, providing a readily available source of progenitors for cell replacement therapy.