Isolation, characterization, differentiative properties of human mesenchymal stem cells isolated from the sub-endocardial layer of post-infarct chronic heart failure-affected patients

Mesenchymal stem cells (MSC) are pluripotent cells which reside in several adult organs, including heart, even if heart regeneration in vivo is still a poorly comprised phenomenon. Contrasting literature reports suggest that several efforts should be made to better characterize resident or migrating MSC populations (for both markers expression and immunogenic potential) prior to their effective use for regenerative medicine applications in heart diseases. We developed a new protocol to obtain human sub-endocardial MSC (HSE-MSC) from post-infarct hearts explanted from chronic heart failure (CHF) patients undergoing heart transplantation. We characterized HSE-MSC by immunocytochemistry (ICC) and RT-PCR, to assess their adherence to the MSC phenotype. The differentiative ability towards the adicpocyte and the osteoblast lineage was assessed using standardized procedures (1). Self-renewal was evaluated by clonogenicity experiments. Karyotype analyses and telomere length assays were further performed. HSE-MSC were successfully isolated and expanded in vitro. These cells spontaneously showed the expression of several key MSC markers. ICC and RT-PCR analyses revealed the expression of c-kit (CD117), CD10, CD13, CD44, CD73, CD90, CD105, CD166, while hematopoietic/endothelial molecules (CD4, CD8, CD20, CD31, CD34, CD45) were absent. Moreover, HSE-MSC expressed key markers of the embryonic stem cell phenotype (Oct3/4 and Nanog), were further positive for the expression of transcription factors involved in heart development (GATA-4, GATA-6, Nkx2.5, Mef2C, Myocardin, ISL-1), but lacked, when kept undifferentiated, the expression of mature myocyte markers (as MYL-2). We assessed for the first time in HSE-MSC the expression of a favorable panel of markers suggesting hypoimmunogenicity of these cells, a positive feature for subsequent in vivo applications. HSE-MSC were differentiated towards the adipogenic and osteoblastic lineage, as demonstrated by histochemical stainings and RT-PCR detection of adipocyte-specific and osteoblast-specific markers. In addition, such cells were able undergoing more than 45 population doublings in culture, maintaining a normal karyotype and long telomeres. Their self-renewal was further demonstrated by clonogenicity experiments. Diseased human heart is still a source of MSC populations, even after developing chronic pathologies as CHF. HSE-MSC are capable of self-renewal, express several stem cell markers, as well as markers of the cardiac differentiation program, and have a hypoimmunogenic profile of surface markers. 1. La Rocca G et al. Histochem Cell Biol 2009 131:267-8