Expansion in Fgf2 Promotes Matrix Synthesis during Chondrogenic Differentiationof Human Bone Marrow Mesenchymal Cells without Upregulating Sox9

INTRODUCTION: Bone marrow mesenchymal cells can be manipulated in vitro to differentiate towards a number of different cellular fates and offer a potential source of cells in a variety of tissue engineering applications. Differentiation of chondrocytes in vivo is mediated through interactions with growth factors, neighbouring cells and the extracellular matrix, though the detailed mechanisms are unclear. In order to generate robust chondrogenesis from marrow mesenchymal cells in a pelleted cell system (1), we and others have found it necessary to supplement the previously published chondrogenic medium (1,2) with various members of the BMP family (3). Alternatively, cells can be expanded in monolayer under different growth factor regimes that will conserve their ability to differentiate into multiple lineages (4). Here we have expanded human bone marrow mesenchymal cells in the presence of FGF2 and provide quantitative evidence of a promotion of chondrogenic differentiation.