Continuously growing bipotential and monopotential myogenic, adipogenic, and chondrogenic subclones isolated from the...

The clonal multipotential RCJ 3.1 cell line, which gives rise to myotubes, adipocytes, chondrocytes, and osteoblasts, contains different progenitor subpopulations. By limiting dilution analysis, of 296 single colonies identified, approximately 20% contained a single recognizable cell type, approximately 10% contained two cell types, and approximately 1% contained three cell types. We recloned RCJ 3.1 and isolated continuously growing subclones, including four novel bipotential (adipocytes/chondrocytes; adipocytes/myotubes and chondrocytes/myotubes) cell populations, whose phenotypes bred true. In the bipotential subclones, single colony analyses confirmed the presence of single cells which could both self-renew the bipotential progenitors and give rise to their respective committed monopotential lineages. Eight subclones were restricted to a single cell lineage and were considered monopotential; one of these is a novel cell line differentiating into cartilage. Thus, we have isolated unique monopotential and bipotential progenitor cell lines which provide a valuable model for studying the mechanisms leading to lineage restriction in mesenchymal populations.