Transcriptional profile of c-kit positive cardiac stem-progenitor cells (c-kitpos eCSCs) isolated from the four chambers of the adult human heart

Abstract

Introduction: Our findings and those of others show that the adult myocardium, including human, harbours a population of resident (endogenous) cardiac stem cells (eCSCs). They express the stem cell factor receptor c-kit, are distributed throughout the myocardium, are clonogenic, self-renewing and multi-potent, in that they differentiate into the 3 main cardiac lineages; cardiomyocytes, smooth muscle and endothelial cells in vitro and in vivo. The objective of this study is to determine whether c-kitpos eCSCs isolated from the different cardiac chambers have a distinct transcriptional profile depending on the chamber of origin. Methods: Pieces of myocardium have been obtained from all the 4 chambers of the adult human heart. All patients were fully consented before undergone open heart surgery. They were suffered of various cardiac pathologies such as ischemic heart disease, aortic, mitral and tricuspid valve insufficiency or stenosis, and various aortic pathologies. Ethical approval for these procedures has been given by NREC (08/H1306/91).c-kitpos eCSCs were isolated by enzymatic digestion and purified by Magnetic Activated Cell Sorting (MACS) from samples taken from the right and left atria (RA, LA), right and left ventricle (RV, LV) of the adult human heart. mRNA was isolated using Qiagen® mRNA kit, and reverse transcribed using first strand cDNA synthesis with random hexamers. qRT-PCR was performed using SYBR Green on a MyIQ thermocycler Bio-Rad® of specific genes representative of the primary and secondary heart field, and the developmental program of their chamber of origin. Results: c-kitpos eCSCs isolated from 15 human samples (5LA, 1RV, 4LV, 5RA) were processed. c-kitpos eCSCs are distributed throughout the human myocardium and in all 4 chambers of the heart. Transmitted light microscopic observations of c-kitpos eCSCs revealed that the c-kitpos cells from the human biopsies were generally small and rounded, consistent with a stable c-kitpos eCSCs phenotype, regardless of the chamber of origin. The eCSCs c-kitpos cells could be cultured under hypoxic conditions between 7 and 12 days to attain full confluency. Expression of transcripts for c-kit, Foxh1, Hand1, Hand2, Pitx2, Tbx5, Tbx20, Hrt1, Hrt2, Fgf8, Fgf10, and Isl1 were found at differential levels in c-kitpos CSCs isolated from the four cardiac chambers. Conclusion: This study is the first to show that c-kitpos eCSCs derived from human adult cardiac samples, do not appear to have a ‘chamber-specific’ transcript footprint, and are therefore potentially interchangeable between cardiac chambers, raising the potential of their therapeutic application.