To investigate the role of age of human pediatric cardiac progenitor cells (hCPCs) on ventricular remodeling, the authors injected neonate, infant, or child hCPCs into rats with right ventricular heart failure. Mechanisms including migration and proliferation assays, as suggested by computational modeling, showed improved chemotactic and proliferative capacity of neonatal hCPCs compared with infant or child hCPCs. Thus, the reparative potential of hCPCs is age-dependent.

Rationale: Congenital heart disease can lead to life-threatening right ventricular heart failure (RVHF). Results from clinical trials support expanding cardiac progenitor cell (CPC) based therapies. However, our recent data show that CPCs lose function as they age, starting as early as 1 year. Objective: To determine whether the aggregation of child (1 to 5-year-old) CPCs into scaffoldfree spheres can improve differentiation by enhancing Notch signaling, a known regulator of CPC fate. We hypothesized that aggregated (3D) CPCs will repair RVHF better than monolayer (2D) CPCs. Methods and Results: Spheres were produced with 1500 CPCs each using a microwell array. CPC aggregation significantly increased gene expression of Notch1 compared to 2D CPCs, accompanied by significant upregulation of cardiogenic transcription factors (GATA4, HAND1, MEF2C, NKX2.5, and TBX5) and endothelial markers (CD31, FLK1, FLT1, vWF). Blocking Notch receptor activation with the γ-secretase inhibitor N-[N-(3,5-Difluorophenacetyl)-L-alanyl]-S-phenylglycine t-butyl ester (DAPT) diminished these effects. To evaluate the therapeutic improvements of CPC aggregation, RVHF was induced in athymic rats by pulmonary artery banding and cells were implanted into the RV free wall. Echocardiographic measurements 28 days post-implantation showed significantly improved RV function with 3D compared to 2D CPCs. Tracking implanted CPCs via DiR-labeling showed improved retention of 3D CPCs. Transducing 3D CPCs with Notch1-shRNA did not reduce retention, but significantly reduced RV functional

Myocardial infarction (MI) is the most common cause of heart failure. Excessive production of ROS plays a key role in the pathogenesis of cardiac remodeling after MI. NADPH with NADPH oxidase (Nox)2 as the catalytic subunit is a major source of superoxide production, and expression is significantly increased in the infarcted myocardium, especially by infiltrating macrophages. While microRNAs (miRNAs) are potent regulators of gene expression and play an important role in heart disease, there still lacks efficient ways to identify miRNAs that target important pathological genes for treating MI. Thus, the overall objective was to establish a miRNA screening and delivery system for improving heart function after MI using Nox2 as a critical target. With the use of the miRNA-target screening system composed of a self-assembled cell microarray (SAMcell), three miRNAs, miR-106b, miR-148b, and miR-204, were identified that could regulate Nox2 expression and its downstream products in both human and mouse macrophages. Each of these miRNAs were encapsulated into polyketal (PK3) nanoparticles that could effectively deliver miRNAs into macrophages. Both in vitro and in vivo studies in mice confirmed that PK3-miRNAs particles could inhibit Nox2 expression and activity and significantly improve infarct size and acute cardiac function after MI. In conclusion, our results show that miR-106b, miR-148b, and miR-204 were able to improve heart function after myocardial infarction in mice by targeting Nox2 and possibly altering inflammatory cytokine production. This screening system and delivery method could have broader implications for miRNA-mediated therapeutics for cardiovascular and other diseases. NADPH oxidase (Nox)2 is a promising target for treating cardiovascular disease, but there are no specific inhibitors. Finding endogenous signals that can target Nox2 and other inflammatory molecules is of great interest. In this study, we used high-throughput screening to identify microRNAs that target Nox2 and improve cardiac function after infarction.