MARROW STROMAL CELLS

Marrow stromal cells comprise a heterogenous population of cells, including reticular endothelial cells, fibroblasts, adipocytes, and osteogenic precursor cells that provide growth factors, cell to cell interactions, and matrix proteins that play a part in the regulation of haematopoiesis.^4–6 The notion that a stromal microenvironment could support haematopoiesis followed by the development of the long term bone marrow culture by Dexter. In this system an adherent bone marrow derived stromal culture could support the production of haematopoietic progenitor cells over a period of several weeks to months. Friedenstein⁷ already described a population of adherent cells from the bone marrow that were non-phagocytic and exhibited a fibroblast-like appearance. Upon culture at low density either as whole bone marrow or after separation over a density gradient the cells formed characteristic colonies derived from a single precursor, referred to as colony forming unit fibroblastic or CFU-F. After ectopic transplantation under the kidney capsule these cells gave rise to a broad spectrum of differentiated connective tissues including bone, cartilage, adipose tissue, and myelosupportive stroma.^7,8 Based on these observations it was proposed that these tissues were derived from a common …