Injured cardiomyocytes promote dental pulp mesenchymal stem cell homing.

BACKGROUND: The heart is unable to regenerate its tissues after severe injuries. Stem cell therapy appears to be one of the most promising approaches, though preclinical results are hitherto contradictory and clinical trials scanty and/or limited to phase-I. The limited knowledge about stem cell early homing in infarcted cardiac tissues can concur to this scenario. METHODS: The stem cell migration was assessed in in-vitro and ex-vivo models of heart ischemia, employing a rat dental pulp stem cell line (MUR-1) that shares the same ontogenic progenitors with portions of the heart, expresses markers typical of cardiac/vascular-like progenitors and is able to differentiate into cardiomyocytes in-vitro. RESULTS: Here, we demonstrated that the MUR-1 can reach the injured cells/tissue and make contacts with the damaged cardiomyocytes, likely through Connexin 43, N-cadherin and von Willebrand Factor mediated cell-cell interactions, both in in-vitro and ex-vivo models. Furthermore, we found that SDF-1, FGF-2 and HGF, but not VEGF are involved as chemotactic factors in MUR-1 migration, notifying a similarity with neural crest cell behavior during the organogenesis of both the splanchnocranium and the heart. CONCLUSIONS: Herein we found a similarity between what happens during the heart organogenesis and the early migration and homing of MUR-1 cells in ischemic models. GENERAL SIGNIFICANCE: The comprehension of molecular aspects underlying the early phases of stem cell migration and interaction with damaged organ contributes to the future achievement of the coveted stem cell-mediated organ regeneration and function preservation in-vivo.

Alpha-linolenic acid protects against cardiac injury and remodelling induced by beta-adrenergic overstimulation.

We investigated the effect of α-linolenic acid (ALA) in protecting the heart from injury caused by ß-adrenergic overstimulation. ALA's role either in isoproterenol (ISO)-treated isolated rat cardiomyocytes (H9c2 cells) or in in vivo rat hearts was studied. In isolated cardiomyocytes in vitro, the involvement of kinases (Src and PI3K) in protection was tested using the specific inhibitors (PP2 or LY294002 respectively), while the role of caveolae was assessed by their disruption with methyl-ß-cyclodextrin. The rats underwent either a normal chow diet or, alternatively, an ALA-enriched diet before, during and throughout the 60 days after 5 days of isoproterenol administration. Before sacrifice, the hemodynamic changes were measured using echocardiography. In the explanted hearts, histological changes together with molecular markers of cardiac fibrosis and hypertrophy were evaluated. In H9c2 cells, ALA abolished the ISO-induced reduction of viability. This effect was suppressed by both the inhibitor PP2 or LY294002 and the caveolae disrupter methyl-ß-cyclodextrin. In the rats, ALA prevented ISO-induced myocardial fibrosis and hypertrophy and kept the cardiac mechanical function as in the control. It also counteracted the increased expressions of transforming growth factor-ß (TGF-ß) and ß-myosin (ß-MHC), the decreased expression of tissue inhibitor metalloproteinase-1 (TIMP-1) and the enhanced activity of matrix metalloproteinase-2 (MMP-2). In conclusion, ALA-induced protection requires the integrity of caveolae where ß2-adrenergic receptors (ß2ARs) are restricted and mediate the activation of the Src-PI3K protective pathway. By preserving this ß2AR pro-survival pathway, an ALA-enriched diet protects the heart against ISO-induced fibrosis and hypertrophy.