ANALYSIS OF THE DEVELOPMENTAL POTENTIAL OF CONDITIONALLY IMMORTAL MARROW-DERIVED MESENCHYMAL PROGENITOR CELLS ISOLATED FROM THE H-2K(B)-TSA58 TRANSGENIC MOUSE

All nucleated cells from the adult transgenic mouse H-2K(b)-tsA58 harb or the temperature-sensitive mutant gene for SV40 large T-antigen. Bon e marrow cells from this transgenic mouse were isolated, expanded and cloned in vitro under conditions permissive to the expression of stabl e T-antigen. Clones of marrow-derived mesenchymal progenitor cells wer e tested in vitro and in vivo for their capacity to differentiate into mature mesenchymal phenotypes of bone, cartilage, muscle, adipose, an d hematopoietic support cells (termed ''stromacytes''). Mono-, bi-, an d tri-potential clones were identified that were able to differentiate into bone, adipose and stromacyte phenotypes. A mixed population of c ells showed some chondrocytic potential in vivo, however, no evidence of cartilage matrix production was detected in vitro for any of the im mortomouse clones. These results support the hypothesis that marrow co ntains multiple progenitor cells that are part of a mesenchymal lineag e.