Defined-size embryoid bodies formed in the presence of serum replacement increases the efficiency of the cardiac differentiation of mouse embryonic stem cells.

The pluripotent nature of embryonic stem (ES) cells makes them powerful tools in cell replacement therapy for severe degenerative diseases, such as heart failure. However, the development of strategies to increase the efficiency of cardiomyocyte (CMC) differentiation is still needed to produce a sufficient amount of cells for clinical applications. This paper evaluates the impact of the size and the aggregation of embryoid bodies (EBs) on the efficiency of ES cell differentiation into CMCs. ES cells were generated from RAP inbred mice. These cells expressed pluripotency markers and induced teratomas when injected into syngeneic mice, which made them suitable for differentiation into CMCs. We found that the EBs that were formed as a result of in vitro ES cell aggregation generated contractile tissue in direct correlation with the initial number of ES cells. Furthermore, the presence of knock-out serum replacement (KO-SR) during ES cell aggregation resulted in less compacted EBs and increased cell differentiation into CMCs compared to the presence of foetal bovine serum. In conclusion, cardiac differentiation of ES cells is dependent on the size and the degree of compaction of EBs, and the presence of KO-SR during initiation of EBs may lead to improved cardiogenic differentiation of ES cells.