A POPULATION OF CELLS ISOLATED FROM RAT-HEART CAPABLE OF DIFFERENTIATING INTO SEVERAL MESODERMAL PHENOTYPES

A population of stem cells has been isolated from embryonic avian and neonatal rat skeletal muscle, These cells differentiate into several m esodermal phenotypes in culture upon treatment with dexamethasone, Thi s study reports the isolation of a similar population of stem cells fr om another mesodermal tissue, the heart, Hearts were excised from 3- t o 5-day-old rats, minced, and treated with a collagenase-dispase solut ion, Single cells were collected by centrifugation, washed, and plated in dishes, The cells were grown to confluence, trypsinized, and froze n at -80 degrees C in 7.5% dimethylsulfoxide. After at least 24 hr, th e cells were thawed and plated in 24-well plates and treated with medi a containing dexamethasone at concentrations of 10(-6)-10(-10) M for 4 weeks, Control cultures contained mononucleated cells with a stellate morphology, Treatment with dexamethasone resulted in the appearance o f several mesodermal phenotypes. Bone and cartilage nodules were ident ified with von Kossa and Alcian blue staining respectively, Adipocytes were identified using Sudan black B stain, Smooth muscle cells were i dentified by an anti-smooth muscle alpha-actin antibody, and skeletal myotubes were stained with anti-myosin antibody, Large binuclear cells with obvious fibers were noted and stained with anti-desmin. These bi nuclear cells appeared in both the control and the dexamethasone-treat ed cultures and were tentatively identified as cardiomyocytes. These d ata strongly suggest the existence of a population of mesenchymal stem cells in neonatal rat heart. (C) 1996 Academic Press, Inc.