Background: Recent reports refute the classic paradigm by which human heart is unable to repair itself following disease or injury. Cardiac and noncardiac stem cells with cardiac regeneration potential have been documented. We studied whether untreated mesenchymal stem cells express markers of cardiomyogenic lineage in vitro.
Methods: Mesenchymal stem cells were obtained from human iliac crest marrow aspirates. Cells were isolated and characterized using flow cytometry by surface expression of CD105, CD166, CD29, CD44, CD14, and CD34. To evaluate their cardiomyogenic potential, presence of cardiac proteins (cardiac troponin I, sarcomeric alpha-actinin, beta myosin heavy chain (beta-MyHC), connexin-43, and SERCA-2), and transcription factors (GATA-4) were assessed.
Results: Mesenchymal stem cells expressed CD105 (4.25 +/- 0.35), CD166 (27.83 +/- 1.89), and CD29 (9.4 +/- 0.57) and were negative for CD34, CD14, and CD45. In absence of additional stimuli in the culture media, these cells expressed connexin-43, alpha-actinin, and GATA-4, and were negative for SERCA-2, cardiac troponin I, and beta-MyHC.
Conclusions: Human adult mesenchymal stem cells spontaneously exhibit markers of cardiac phenotype in vitro. In the appropiate myocardial environment, these cells may transdifferentiate into mature cardiomyocytes.