Bone morphogenetic proteins (BMPs) play a dual role as a factor in both bone and cartilage development and correspondingly have the therapeutic potential to regenerate both tissues. Given this dual nature, previous in vitro research using BMPs has relied on distinct media formulations and culture conditions to drive undifferentiated cells to the osteogenic or chondrogenic lineage. To isolate the impact of culture conditions and to explore the effect of BMP-6 on murine adipose-derived mesenchymal cells (ASCs), ASCs were seeded in either monolayer or pellets in an identical medium containing BMP-6. Results indicate that BMP-6 differentially promotes osteogenesis and chondrogenesis in ASCs depending on culture conditions. BMP-6 potently induced alkaline phosphatase activity and mineralization in ASCs cultured in monolayer conditions. In contrast, BMP-6 enhanced proteoglycan accumulation in ASCs seeded in chondrogenic pellet culture. A comparison of gene expression suggests that the differentiating effect of BMP-6 is specific to the particular culture condition. This study highlights the importance of the interactions between chemical signaling and microenvironmental cues in directing cell fate. (C) 2010 Elsevier Inc. All rights reserved.