Cardiac and systemic rejuvenation after cardiosphere-derived cell therapy in senescent rats.

Aim: The aim is to assess the effects of CDCs on heart structure, function, gene expression, and systemic parameters in aged rats. Diastolic dysfunction is characteristic of aged hearts. Cardiosphere-derived cell (CDC) therapy has exhibited several favourable effects on heart structure and function in humans and in preclinical models; however, the effects of CDCs on aging have not been evaluated.

Methods and Results: We compared intra-cardiac injections of neonatal rat CDCs to vehicle (phosphate-buffered saline, PBS) in 21.8 ± 1.6 month-old rats (mean ± standard deviation; n = 23 total). Ten rats 4.1 ± 1.5 months of age comprised a young reference group. Blood, echocardiographic, haemodynamic and treadmill stress tests were performed at baseline in all animals, and 1 month after treatment in old animals. Histology and the transcriptome were assessed after terminal phenotyping. For in vitro studies, human heart progenitors from older donors, or cardiomyocytes from aged rats were exposed to human CDCs or exosomes secreted by CDCs (CDC-XO) from paediatric donors. Transcriptomic analysis revealed that CDCs, but not PBS, recapitulated a youthful pattern of gene expression in the hearts of old animals (85.5% of genes differentially expressed, P < 0.05). Telomeres in heart cells were longer in CDC-transplanted animals (P < 0.0001 vs. PBS). Cardiosphere-derived cells attenuated hypertrophy by echo (P < 0.01); histology confirmed decreases in cardiomyocyte area (P < 0.0001) and myocardial fibrosis (P < 0.05) vs. PBS. Cardiosphere-derived cell injection improved diastolic dysfunction [lower E/A (P < 0.01), E/E' (P = 0.05), end-diastolic pressure-volume relationship (P < 0.05) compared with baseline), and lowered serum brain natriuretic peptide (both P < 0.05 vs. PBS). In CDC-transplanted old rats, exercise capacity increased ∼20% (P < 0.05 vs. baseline), body weight decreased ∼30% less (P = 0.05 vs. PBS) and hair regrowth after shaving was more robust (P < 0.05 vs. PBS). Serum biomarkers of inflammation (IL-10, IL-1b, and IL-6) improved in the CDC group (P < 0.05 for each, all vs. PBS). Young CDCs secrete exosomes which increase telomerase activity, elongate telomere length, and reduce the number of senescent human heart cells in culture.

Conclusion: Young CDCs rejuvenate old animals as gauged by cardiac gene expression, heart function, exercise capacity, and systemic biomarkers.