Superior exosome-mediated paracrine effects of cardiac progenitor cells compared to bone marrow mesenchymal stem cells derived from the same patient for cardiac repair

Background: Both bone marrow-derived mesenchymal stem cells (BM-MSCs) and cardiac progenitor cells (CPCs) have shown promising results in clinical trials in patients after acute myocardial infarction (MI). Available evidence supports paracrine effects as the mechanism of benefit of both cell types. Recently, we have shown that exosomes (Exo), secreted extracellular nanovesicles, is the critical component of the paracrine activity of CPCs. However, exosomes derived from BM-MSC (Exo-MSC) and those derived from CPCs (Exo-CPC) have not been compared thus far. Methods and results: Both a sternal BM aspirate and a right atrial appendage explant were obtained from patients who underwent heart surgery for valve disease to derive BM-MSCs and CPCs, respectively. Exo was purified by ultracentrifugation from the respective conditioned media (CM). Exo-CPC inhibited staurosporin-induced in vitro apoptosis in mouse HL-1 cardiomyocytes more effectively than Exo-MSC. Exo-depleted CM from either cell type was inactive. Both Exo-CPC and Exo-MSC promoted angiogenesis in vitro. Infarcted rat hearts injected with Exo-CPC showed significantly less cardiomyocyte apoptosis and scar, more angiogenesis, higher end-diastolic thickness, and a significant improvement in LV ejection fraction (LVEF) at 4 weeks post-MI compared with those injected with Exo-MSC, exosomes derived from human dermal fibroblasts (Exo-F) as an inert cell control, or saline. Exo-MSC showed intermediate efficacy between Exo-CPC and Exo-F. Both Exo-CPC and Exo-MSC were enriched for cardioprotective and/or proangiogenic miRNAs such as miR-146a-3p, miR-210 and miR-132 compared to Exo-F. Proteomics analyses identified a number of proteins overexpressed in Exo-CPC relative to Exo-MSC, including potentially beneficial proteins such as pregnancy-associated plasma protein-A (PAPP-A, or pappalysin), which releases active interleukin-like growth factor-1 (IGF-1) from IGF binding proteins, and superoxide dismutase-2 (SOD2). Using PAPP-A-specific silencing RNAs, we showed that Exo from PAPP-A knockdown CPCs were significantly less efficient than Exo from naïve CPCs using the in vivo infarct model. Conclusion: Exo fully accounts for paracrine cardioprotective effects by CPCs and BM-MSCs. On a same patient-basis, Exo-CPC was more cardioprotective than Exo-MSC both in vitro and in vivo. Enrichment of Exo-CPCs with PAPP-A significantly contributes to its beneficial effects