A summary of cell lines, which express CTRP3, in vitro, are listed in Table 3. CTRP3 is not detectable in undifferentiated adipocytes, but can be detected at 4 days of differentiation (55, 56). These data match in vivo data which shows that CTPR3 is highly expressed in adipose tissue. In addition, CTRP3 is also detected during development, starting at mouse embryonic day 15 (43,75,76), in developing chondrocytes (43) and cartilage (44). These data have led to speculation that CTRP3 is essential for appropriate bone growth and development. This is supported by experimental evidence that demonstrates that CTRP3 stimulates the proliferation and differentiation of chondrogenic and osteogenic precursors, inhibits osteoclast activity, and is essential for appropriate bone formation in vitro (1, 27, 44, 82). However, a clinical association between abnormal development and deregulation of CTRP3 protein has yet to be documented. On the other hand, CTRP3 is highly expressed in both osteoscarcoma and chandroblastoma cell lines but not in the MC3T3-E1 mouse osteoblast-like non-cancer cell line (3). These data have led to speculation that elevated CTRP3 level in adults may be
