Engineering cardiac muscle: new ways to refurbish old hearts?

Myocardial infarction leads to irreversible cell loss and scar forma-tion, which result in impaired cardiac function, cardiac hyper-trophy and, eventually, heart failure. As the intrinsic regenerative capacity of the human heart is very limited, organ transplantation or ventricular assist devices remain the only end-stage therapy options to date. For at least two decades, alternative therapeutic concepts of heart repair based either on direct cell injection or on the trans-plantation of in vitro engineered tissue constructs have been con-sidered potential approaches to overcome the shortage of donor organs. However, the multitude of recent experimental and clinic-al studies applying various adult stem cells have thus far not been able to fulfil the initial high hopes vested in adult stem cell-based therapies. As summarized in a recent meta study, the vast majority of these studies resulted either in no or in only minor functiona