Bone marrow stromal cells: Characterization and clinical application

The bone marrow stroma consists of a heterogeneous population of cells that provide the structural and physiological support for hematopoietic cells. Additionally, the bone marrow stroma contains cells with a stem-cell-like c haracter that allows them to differentiate into bone, cartilage, adipocytes , and hematopoietic supporting tissues. Several experimental approaches hav e been used to characterize the development and Functional nature of these cells in vivo and their differentiating potential in vitro. In vivo, presum ptive osteogenic precursors have been identified by morphologic and immunoh istochemical methods. In culture, the stromal cells can be separated from h ematopoietic cells by their differential adhesion to tissue culture plastic and their prolonged proliferative potential. In cultures generated from si ngle-cell suspensions of marrow, bone marrow stromal cells grow in colonies , each derived From a single precursor cell termed the colony-forming unit- fibroblast. Culture methods have been developed to expand marrow stromal ce lls derived From human, mouse, and other species. Under appropriate conditi ons, these cells are capable of Forming new bone after in vivo transplantat ion. Various methods of cultivation and transplantation conditions have bee n studied and found to have substantial influence on the transplantation ou tcome. The finding that bone marrow stromal cells can be manipulated in vit ro and subsequently form bone in vivo provides a powerful new model system for studying the basic biology of bone and for generating models for therap eutic strategies aimed at regenerating skeletal elements.