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.

Background Human stem cells (CSCs) promote myocardial regeneration in adult ischemic myocardium. The regenerative capacity of CSCs in the very young patients with non-ischemic congenital heart defects has not been explored. We hypothesized that isolated neonatal-derived CSCs may have a higher regenerative ability than adult-derived CSCs and might address the structural deficiencies of congenital heart disease. Methods and Results Human specimens were obtained during routine cardiac surgical procedures from right atrial appendage tissue discarded from two age groups: neonates and adults patients. We developed a reproducible isolation method that generated cardiosphere derived cells (CDCs), regardless of starting tissue weight or age. Neonatal-derived CDCs demonstrated increased number of cardiac progenitor cells expressing c-kit+, flk-1 and Islet-1 by flow cytometry and immunofluorescence. When transplanted into infarcted myocardium, neonatal-derived CDCs had a significantly higher ability to preserve myocardial function, prevent adverse remodeling and enhance blood vessel preservation and/or formation when compared to adult CDCs. Lastly, neonatal-derived CDCs were more cardiomyogenic than adult CDCs when co-cultured with neonatal cardiomyocytes and displayed enhanced angiogenic function compared to adult CDCs. Conclusions Neonatal-derived CDCs have a strong regenerative ability when compared to adult-derived CDCs that may depend on angiogenic cytokines and an increase prevalence of stem cells. This has important implications in the potential use of CDCs in future clinical trials.

The stem cell field is hindered by its inability to noninvasively monitor transplanted cells within the target organ in a repeatable, time-sensitive, and condition-specific manner. We hypothesized that quantifying and characterizing transplanted cell–derived exosomes in the recipient plasma would enable reliable, noninvasive surveillance of the conditional activity of the transplanted cells. To test this hypothesis, we used a human-into-rat xenogeneic myocardial infarction model comparing two well-studied progenitor cell types: cardiosphere-derived cells (CDCs) and c-kit+ cardiac progenitor cells (CPCs), both derived from the right atrial appendage of adults undergoing cardiopulmonary bypass. CPCs outperformed the CDCs in cell-based and in vivo regenerative assays. To noninvasively monitor the activity of transplanted CDCs or CPCs in vivo, we purified progenitor cell–specific exosomes from recipient total plasma exosomes. Seven days after transplantation, the concentration of plasma CPC-specific exosomes increased about twofold compared to CDC-specific exosomes. Computational pathway analysis failed to link CPC or CDC cellular messenger RNA (mRNA) with observed myocardial recovery, although recovery was linked to the microRNA (miRNA) cargo of CPC exosomes purified from recipient plasma. We further identified mechanistic pathways governing specific outcomes related to myocardial recovery associated with transplanted CPCs. Collectively, these findings demonstrate the potential of circulating progenitor cell–specific exosomes as a liquid biopsy that provides a noninvasive window into the conditional state of the transplanted cells. These data implicate the surveillance potential of cell-specific exosomes for allogeneic cell therapies.

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An elevation of cardiac injury markers including creatinine kinase (CK), myoglobin (Myo) and cardiac troponin T (cTnT) has been observed in elite athletes following strenuous exercise. The mechanism and significance of this observation however have not been fully elucidated. The goals of this study were: 1) to determine whether these changes in biomarkers also occur in a large, heterogeneous group of non-elite athletes; and 2) to identify possible clinical or biochemical associations. We recruited 129 non-elite runners in 2006, 61 individuals who were taking part in the half (13.1 miles) marathon and 68 individuals participating in the full (26.2 miles) marathon. Demographic data and blood samples were collected for analysis of CK, Myo, cTnT, and Creatinine (Cr) levels within two hours of race start, at race completion, and 1-h post-race for both patient cohorts. In the 61 individuals (40 males, 40+/-12 yrs) completing the half marathon in a mean time of 150+/-20 min, 90.3%, 65.2%, and 30.6% of the subjects exhibited significant elevations in Myo, CK, and cTnT, respectively immediately post race and 100%, 74.9% and 45.9% in the same biomarkers one hour-post race. In the 68 individuals (44 males, 42+/-14 yrs) completing the full marathon in a mean time of 310+/-30 min, 95.3%, 70.2% and 35.7% exhibited significant elevations in Myo, CK and cTnT respectively immediately post race and 100%, 78.5% and 52.8% in the same biomarkers one hour-post race. The elevation in cTnT levels post-race were modestly associated with the time required to complete the race for the entire cohort of marathon runners. The serum levels of Cr, CK, and Myo post-race did not correlate however with age, sex, BMI, level of training, or prior marathon experience. Elevations of cardiac injury markers in non-elite athletes are extremely common following the completion of endurance events and correlate to the increased endurance time. Whether the increase in the levels of these enzymes represents true myocardial injury or a result of the release of cTnT from the myocytes requires further investigation.