Abstract 13086: Defects in EphA2 Signaling Impair the Migration of Old Human Cardiac Stem Cells
Effective myocardial repair requires that cardiac stem cells (CSCs) translocate from the niches to the sites of injury. The decreased regenerative potential of the aging heart may be dictated by a decline in the migratory capacity of old human CSCs (hCSCs), possibly interfering with the efficacy of stem cell therapy in the elderly. hCSCs express the cell-guidance regulator EphA2, which is selectively activated by the ephrin A1 ligand. EphA2 stimulation with ephrin A1 promoted motility in young hCSCs, both in vitro and in vivo. However, ephrin A1-induced behavior was impaired in old hCSCs, in which spontaneous migration and chemotaxis towards HGF were significantly inhibited. Following delivery to the myocardium, young hCSCs displayed an average 2.4-fold higher translocation velocity than aged hCSCs. Old hCSCs were characterized by elevated levels of ROS, which caused post-translational modifications of EphA2, interfering with its autophosphorylation. This alteration in EphA2 function hindered the formation of signaling endosomes carrying EphA2, phospho-Src, and phospho-caveolin 1, ultimately affecting cell movement. Overexpression of exogenous EphA2 receptor with intact kinase activity restored signalosome formation and motility in old hCSCs, further strengthening the importance of EphA2-mediated responses for hCSC migration. Based on these findings, we developed a novel approach for the prospective isolation of hCSCs with younger phenotype and preserved regenerative reserve. Young hCSCs efficiently adhered to surfaces coated with immobilized ephrin A1 ligand, a process that is abrogated following siRNA-mediated EphA2 knockdown. The inefficient EphA2 receptor signaling in old hCSCs substantially reduced their ability to adhere to ephrin A1. The subset of hCSCs adhering to ephrin A1 displayed a 2-fold lower expression of the senescence-associated proteins p16INK4a and γH2AX. Collectively, our data demonstrate that the ephrin A1/EphA2 pathway may serve as a target to facilitate trafficking of hCSCs in the senescent myocardium. Importantly, EphA2 receptor function can be implemented for the selection of hCSCs with high therapeutic potential, a clinically relevant strategy that does not require genetic manipulation of stem cells.
- © 2013 by American Heart Association, Inc.