The aim of this study was to investigate the effects of different growth factors on the chondrogenic potential of human bone marrow stromal cells (BMSC).
Different growth factors which have been shown to sustain the osteogenic potential of BMSC during their 'in vitro' expansion were assayed for the maintenance of the chondrogenic potential. We compared the ability of BMSC to reconstitute cartilage in vitro with their ability to form bone on hydroxyapatite microporous particles in an ectopic bone formation assay.
Among the factors assayed, fibroblast growth factor 2 (FGF2) was the most effective in promoting growth of BMSC 'in vitro'. For all growth factors tested, we have found a complete overlap of the enhancement of chondrogenic and osteogenic potential. Any factor, either promoting or depressing bone formation, exerted the same effect on the chondrogenic potential of human BMSC. In particular, FGF2, either alone or in combination with other factors, strongly supported the formation of bone as well as of cartilage.
We conclude that FGF2 maintains human BMSC in an immature state allowing their 'in vitro' expansion. Expanded cells retain the chondro- osteogenic potential. Interestingly, the chondrogenic potential of BMSC 'in vitro' is directly related to their ability to form bone 'in vivo'. BMSC expanded 'ex vivo' are presently being proposed for cell therapy of bone defects. 'In vitro' chondrogenesis may be regarded as a rapid prediction assay to assess cell ability to form bone after 'in vivo' transplant.