Mesenchymal stem cells: promising for myocardial regeneration?

The pandemic of cardiovascular disease is continuously expanding as the result of changing life styles and diets throughout the Old and New World. Immediate intervention therapy saves the lives of many patients after acute myocardial infarction (MI). However, for many this comes at the price of adverse cardiac remodeling and heart failure. Currently, no conventional therapy can prevent the negative aftermath of MI and alternative treatments are warranted. Therefore, cardiac stem cell therapy has been put forward over the past decade, albeit with modest successes. Mesenchymal Stem Cells (MSC) are promising because these are genuine cellular factories of a host of secreted therapeutic factors. MSC are obtained from bone marrow or adipose tissue (ADSC). However, the heart itself also contains mesenchymal- like stem cells, though more difficult to acquire than ADSC. Interestingly, mesenchymal cells such as fibroblasts can be directly or indirectly reprogrammed to all myocardial cell types that require replacement after MI. To date, the paracrine and juxtacrine mechanisms of ADSC and other MSC on vessel formation are best understood. The preconditioning of, otherwise naive, stem cells is gaining more interest: previously presumed deleterious stimuli such as hypoxia and inflammation, i.e. causes of myocardial damage, have the opposite effect on mesenchymal stem cells. MSC gain a higher therapeutic capacity under hypoxia and inflammatory conditions. In this review, mesenchymal stem cells and their working mechanisms are put into the perspective of clinical cardiac stem cell therapy.