Rationale Cardiac progenitor cells are an attractive cell type for tissue regeneration but their mechanism for myocardial remodeling is still unclear. Objective This investigation determines how chronological age influences the phenotypic characteristics and the secretome of human cardiac progenitor cells (CPCs), as well as their potential to recover injured myocardium. Methods and Results Adult (aCPCs) and neonatal (nCPCs) cells were derived from patients more than 40 years or less than one month of age, respectively, and their functional potential was determined in a rodent myocardial infarction (MI) model. A more robust in vitro proliferative capacity of nCPCs, compared to aCPCs, correlated with significantly greater myocardial recovery mediated by nCPCs in vivo. Strikingly, a single injection of nCPC-derived total conditioned media (nTCM) was significantly more effective than nCPCs, aCPC-derived TCM (aTCM), or nCPC-derived exosomes in recovering cardiac function, stimulating neovascularization, and promoting myocardial remodeling. High resolution accurate mass spectrometry (HRAMS) with reverse phase liquid chromatography fractionation and mass spectrometry (LC-MS/MS) was employed to identify proteins in the secretome of aCPCs and nCPCs, and literature-based networking software identified specific pathways affected by the secretome of CPCs in the setting of MI. Examining the TCM, we quantified changes in the expression pattern of 804 proteins in nTCM and 513 proteins in aTCM. Literature-based proteomic network analysis identified that 46 and 6 canonical signaling pathways were significantly targeted by nTCM and aTCM, respectively. One leading candidate pathway is heat shock factor-1 (HSF-1), potentially affecting 8 identified pathways for nTCM but none for aTCM. To validate this prediction, we demonstrated that modulation of HSF-1 by knockdown in nCPCs or overexpression in aCPCs significantly altered the quality of their secretome. Conclusions In conclusion, a deep proteomic analysis revealed both detailed and global mechanisms underlying the chronological age-based differences in the ability of CPCs to promote myocardial recovery via the components of their secretome.

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(MSCs) have not been evaluated in a preclinical model of pressure overload, which simulates the pathophysiology relevant to many forms of CHD. A neonatal swine model of RV pressure overload was utilized to test the hypothesis that MSCs preserve RV function and attenuate ventricular remodeling. Immunosuppressed Yorkshire swine underwent pulmonary artery banding to induce RV dysfunction. After 30 min, human MSCs (1 million cells, n ϭ 5) or placebo (n ϭ 5) were injected intramyocardially into the RV free wall. Serial transthoracic echocardiography monitored RV functional indices including 2D myocardial strain analysis. Four weeks postinjection, the MSC-treated myocardium had a smaller increase in RV end-diastolic area, end-systolic area, and tricuspid vena contracta width (P Ͻ 0.01), increased RV fractional area of change, and improved myocardial strain mechanics relative to placebo (P Ͻ 0.01). The MSC-treated myocardium demonstrated enhanced neovessel formation (P Ͻ 0.0001), superior recruitment of endogenous c-kitϩ cardiac stem cells to the RV (P Ͻ 0.0001) and increased proliferation of cardiomyocytes (P ϭ 0.0009) and endothelial cells (P Ͻ 0.0001). Hypertrophic changes in the RV were more pronounced in the placebo group, as evidenced by greater wall thickness by echocardiography (P ϭ 0.008), increased cardiomyocyte cross-sectional area (P ϭ 0.001), and increased expression of hypertrophy-related genes, including brain natriuretic peptide, ␤-myosin heavy chain and myosin light chain. Additionally, MSC-treated myocardium demonstrated increased expression of the antihypertrophy secreted factor, growth differentiation factor 15 (GDF15), and its downstream effector, SMAD 2/3, in cultured neonatal rat cardiomyocytes and in the porcine RV myocardium. This is the first report of the use of MSCs as a therapeutic strategy to preserve RV function and attenuate remodeling in the setting of pressure overload. Mechanistically, transplanted MSCs possibly stimulated GDF15 and its downstream SMAD proteins to antagonize the hypertrophy response of pressure overload. These encouraging results have implications in congenital cardiac pressure overload lesions. stem cell therapy; congenital heart disease; right ventricle; pressure overload CONGENITAL HEART DISEASE (CHD) is the leading cause of morbidity and mortality in children with birth defects. While surgical interventions have dramatically improved outcomes and longevity in patients with CHD, many patients still progress to heart failure, a population that has grown significantly over the last decade (30). In contrast to adult patients, in whom ischemic heart disease is the predominant etiology of heart failure, children with CHD are frequently exposed to acute or chronic ventricular pressure and volume overload, which if untreated can progress to ventricular dysfunction and ultimately to heart failure. Further, patients with CHD who develop right ventricular (RV) dysfunction have the poorest outcomes (23, 26), particularly in those patients with univentricular heart disease i...