In practice, MSCs can be defined by the criteria shown in the Table, as proposed by the ISCT Mesenchymal and Tissue Stem Cell Committee. It is therefore quite reasonable for investigators to demonstrate such trilineage differentiation in vitro to prove their cells under study are MSCs. The single most characteristic feature of MSCs is the capacity to differentiate to osteoblasts, adipocytes, and chondroblasts in vitro. Stable, pancellular expression of surface markers that are unique to MSCs within the bone marrow, the most common source of MSCs, would greatly facilitate the identification of these cells. While unequivocally identifying MSCs, this surface marker profile is cumbersome. Additionally, MSCs express MHC Class I molecules in vitro, but not Class II molecules unless stimulated, e.g. These cells do not express hematopoietic antigens, e.g. Furthermore, CD90 is expressed on all cells that we accept as MSCs. Subsequently, SH2 and SH3 were shown to recognize epitopes on CD105 and CD73, respectively. The first important studies of surface antigen markers led to the development of SH2 and SH3, antibodies which seemed to identify MSCs.

However, all proposed MSC populations are plastic adherent in vitro hence, this is one defining characteristic. The defining characteristics of MSCs are inconsistent among investigators due, in part, to the lack of a universally accepted surface marker phenotype. This discussion will focus on the properties of MSCs that engender their utility as therapeutic cells and specifically on MSCs as treatment for GVHD and as targeting vehicles for anti-tumor therapies. MSCs are also thought to be of great value for cell based therapies. Following intramedullary transplantation of eGFP-marked human MSCs into a NOD SCID mouse, the MSCs incorporated into the murine marrow microenvironment and improved the human hematopoietic stem cell activity in the host mouse. MSCs undoubtedly play a critical role in the marrow microenvironment.

However, convincing data to support the “stemness” of these cells were not forthcoming, and now most investigators recognize that in vitro isolated MSCs are not a homogenous population of stem cells, although a bona fide mesenchymal stem cell may reside within the adherent cell compartment of marrow. The notion of a mesenchymal stem cell was popularized by Arnold Caplan proposing that MSCs gave rise to bone, cartilage, tendon, ligament, marrow stroma, adipocytes, dermis, muscle and connective tissue.

Based largely on Friendenstein’s work, Maureen Owen proposed the existence of a stromal stem cell to maintain the marrow microenvironment as the hematopoietic stem cell maintains hematopoiesis. He showed that MSCs could differentiate to bone in vitro and a subset of the cells had a high proliferative potential (CFU-F) when plated at low density in tissue culture. MSCs were first described by Friendenstein as hematopoietic supportive cells of bone marrow. However, whether MSCs truly qualify as stem cells is an area of some debate. Mesenchymal stromal cells (MSCs) are the spindle shaped plastic-adherent cells isolated from bone marrow, adipose, and other tissue sources, with multipotent differentiation capacity in vitro.

Gta 2 game