HB-GAM PLEIOTROPHIN BUT NOT RIHB/MIDKINE ENHANCES CHONDROGENESIS IN MICROMASS CULTURE/

The heparin-binding growth-associated molecule HB-GAM (also named plei otrophin) and the retinoic acid-induced heparin-binding protein RIHB ( chicken midkine) are developmentally regulated proteins forming a new family of heparin-binding molecules with putative functions during cel l growth and differentiation. A direct involvement of these molecules during chondrogenesis in vivo was suggested by their patterns of expre ssion. The putative chondrogenic activity of these molecules was inves tigated in vitro using micromass cultures from chicken limb bud mesenc hymal cells. Exogenous HB-GAM, not RIHB, was found to enhance chondrog enesis in this system. These results provide a strong incentive for co nsidering and further investigating the role of this protein in the co ntrol of limb cartilage differentiation. (C) 1998 Academic Press.