The 3T3-L1 Fibroblast to Adipocyte Conversion is Accompanied by Increased Expression of Angiopoietin-1, a Ligand for Tie2

The tie2 receptor tyrosine kinase plays a key role in angiogenesis, and the remodeling and maturation of blood vessels. In this study we have used a factor-dependent cell line (Ba/F3) expressing a chimeric receptor containing the extracellular domain of mouse tie2 and the transmembrane and cytoplasmic domain of the erythropoietin receptor to identify specific binding activity associated with an adipogenic sub-line of 3T3 fibroblasts (3T3-L1). 3T3-L1 fibroblasts are capable of undergoing differentiation to adipocytes under specific culture conditions. When compared to 3T3-L1 cells, the adipocyte differentiated cultures, which contain both pre-adipocytes and adipocytes, exhibited a significantly increased ability to support the growth of Ba/F3 cells expressing the chimeric receptor. Using probes specific for two recently described ligands for tie2, Ang-1 and Ang-2, we have shown that mRNA encoding Ang-1 is upregulated when 3T3-L1 fibroblasts are differentiated to adipocytes. These results suggest that the levels of Ang-1 protein and mRNA in 3T3-L1 cells can be regulated by cellular differentiation in adipose development.