[Differences between adipose-derived stem cells and mesenchymal stem cells in differentiation into cardiomyocytes].

Adipose-derived stem cells (ASCs) are similar to bone marrow mesenchymal stem cells (MSCs) in growth kinetics, antigen expression and multi-lineage differentiation capacity. The present study was designed to investigate the differences between ASCs and MSCs in in vitro culture and differentiation into cardiomyocytes. ASCs were isolated from the fat tissue of New Zealand white rabbits while MSCs were obtained from rat bone marrow. Both ASCs and MSCs were cultured in Iscove's modified Dulbecco's medium supplemented with 15% fetal bovine serum in the same incubator and treated with various concentrations of 5-azacytidine. A clonogenic assay was used to quantify ASCs in fat tissue and MSCs in bone marrow. The number of ASCs in the fat tissue was much higher than that of MSCs in the bone marrow quantified by clonogenic assay, and MSCs showed a remarkably slower proliferative rate compared with ASCs, especially at primary passage. ASCs began to attach to the bottom of the culture flask 12 h after seeding. The cells in culture assumed a short spindle shape under a phase-contrast microscope and did not form clusters. The phenotype was maintained through repeated subcultures under nonstimulating conditions. No other cell phenotype was observed. MSCs attached to the culture flask at 24-48 h after seeding and grew in clusters. The cells were fibroblast-like and prone to senescence or differentiation into adipose cells. Both ASCs and MSCs before treatment with 5-azacytidine were stained positively for CD29, CD44 and CD105 but negatively for CD34 and CD45, α-sarcromeric actin, cardiac troponin T and von Willebrand factor. ASCs differentiated into cardiomyocytes only after treatment with 6-9 µmol/L of 5-azacytidine, while MSCs differentiated into cardiomyocytes with 3-15 µmol/L of 5-azacytidine. After treatment with ideal dose of 5-azacytidine, ASCs began to change their morphology and showed multinucleation within the first week and formed a ball-like appearance thereafter, while MSCs showed multinucleation at the second week and formed a stick-like appearance at 3-4 weeks. The percentage of ASCs differentiated into cardiomyocytes after treatment with 5-azacytidine was significantly higher than that of MSCs. The age of animal had no significant influence on the tissue content, proliferation and differentiation rate of ASCs. However, the tissue content of MSCs in bone marrow decreased with increased age of animal and MSCs from old donor rats exhibited less myogenic cells than those from the young rats after exposure to 5-azacytidine. These results indicate that ASCs have advantages over MSCs in tissue content, homology, growth and differentiation rate, suggesting that ASCs are more suitable for cellular cardiomyoplasty than MSCs.