Amniotic mesenchymal cells autotransplanted in a porcine model of cardiac ischemia do not differentiate to cardiogenic phenotypes

Transplantation of stem cells in the acute ischemic myocardium (AMI) may play a role in the recovery of cardiac function. Here, we investigated the ability of amniotic fluid-derived mesenchymal cells (AFC) for phenotypic conversion to vascular cells and cardiomyocytes (CM) when autotransplanted in a porcine model of AMI. Single AFC preparations were taken from 12 fetuses 3 days before normal delivery. AFC were expanded in vitro and stored separately until animals of the original litter weighed 22-25 kg. A new model of AMI, i.e. 45-min circumflex coronary occlusion followed by wall dissection, was used to assess AFC differentiation potential. CMFDA-labeled AFC were autogenically transplanted in the ischemic area 1 week after AMI induction. Thirty days later, pigs were sacrificed and the phenotypic profile of transplanted AFC was assessed and compared to the corresponding pre-injection pattern. AFC showed in vitro to be of mesenchymal type also expressing markers of 'embryonic stem' cells (SSEA4 and Oct-4), as well as endothelial (von Willebrand factor, VE-cadherin) and smooth muscle (SM alpha-actin, SM22) cells. Thirty days after transplantation, in the survived AFC (5+/-1%) 'embryonic stem' cell markers disappeared and mesenchymal cell markers were down regulated with the exception of smooth muscle and endothelial antigens. No evidence for expression of cardiac troponin I was found. In the conditions used in this study, AFC were able to transdifferentiate to cells of vascular cell lineages but not to CM. Thus, porcine AFC may require further ex vivo re-programming to be suitable for therapeutic use in AMI.