Long-term benefit of intracardiac delivery of autologous granulocyte-colony-stimulating factor-mobilized blood CD34+ cells containing cardiac progenitors on regional heart structure and function after myocardial infarct

Background aims Starting from experimental data proposing hematopoietic stem cells as candidates for cardiac repair; we postulated that human peripheral blood (PB) CD34(+) cell mobilized by hematopoietic growth-factor (G-CSF) would contain cell subpopulations capable of regenerating post-ischemic myocardial damages. Methods In a phase I clinical assay enrolling seven patients with acute myocardial infarct, we directly delivered to the injured myocardium autologous PB CD34(+) cells previously mobilized by G-CSF collected by leukapheresis and purified by immunoselection. In parallel, we looked for the eventual presence of cardiomyocytic and endothelial progenitor cells in leukapheresis products of these patients and controls, using flow cytometry, reverse transcription-quantitative (RTQ)-polymerase chain reaction (PCR), cell cultures and immunofluorescence analyzes. Results The whole clinical process was feasible and safe. All patients were alive at an average follow-up of 49 months (range 24-76 months). Improvement of heart function parameters became obvious from the third month following cell reinjection. Left ventricular ejection fraction values progressively and dramatically increased with time, associated with PetScan demonstration of myocardial structure regeneration and revascularization and New York Heart Association (ATHA) grade improvement. Furthermore, we identified PB CD34(+) cell subpopulations expressing characteristics of both immature and mature endothelial and cardiomyocyte progenitor cells. In vitro CD34(+) cell cultures on a specific medium induced development of adherent cells featuring morphologies, gene expression and immuno-cytochemistry characteristics of endothelial and cardiac muscle cells. Conclusions Mobilized CD34(+) cells contain stem cells committed along endothelial and cardiac differentiation pathways, which could play a key role in a proposed two-phase mechanism of myocardial regeneration after direct intracardiac delivery, probably being responsible fir the long-term clinical benefit observed.