Osteopontin stimulates cell cycle activity in cardiac cells and improves infarct repair
Presented by: Itai Rotem
Presentation time:
Background: Understanding the mechanism by which macrophages control myocardial regeneration can facilitate the efforts to develop new therapies for infarct repair. We aimed to determine what underlies the regenerative properties of macrophages in the injured heart.
Methods: To determine the mechanism by which macrophages promote myocardial regeneration, we subjected neonatal mice to apical resection (AR), myocardial infarction (MI), or sham operation. To define and characterize putative mediators of myocardial regeneration, we used gene expression analysis, flow cytometry, histology, analysis of macrophage secretome, myocardial organ and cardiomyocyte (CM) cell culture, immunoblot, CM viability assays, and functional in vitro assays. To determine the relevance of our findings to the adult heart, we subjected adult mice to MI and assess temporal changes in left ventricular (LV) remodelling and function by echocardiography, strain imaging, and post-mortem morphometry.
Results: Myocardial injury in the neonatal heart resulted in a massive accumulation of monocytes and macrophages within a day after injury. Gene expression profiling and macrophage secretome from the injured hearts identified high levels of osteopontin (OPN). Subsequently, we observed impaired myocardial regeneration in OPN knockout mouse after AR. Moreover, OPN treatment stimulated cardiac cell outgrowth, proliferation, and migration. In CMs, OPN acted via the receptor CD44 and downstream phosphorylation of the Hippo-Yes-associated protein (YAP) and the extracellular signal-regulated kinase (ERK). OPN treatment translocated YAP into the nucleus, where it stimulated cell cycle through interaction with transcriptional factors and upregulation of cell cycle genes. Finally, single injection of OPN to adult mice significantly improved cardiac remodeling and function after MI.
Conclusions: We have shown, for the first time, that macrophage OPN activate CM cell cycle activity and play a role in myocardial regeneration. Our results suggest a new macrophage-inspired cell-free therapy to optimize infarct repair.
Methods: To determine the mechanism by which macrophages promote myocardial regeneration, we subjected neonatal mice to apical resection (AR), myocardial infarction (MI), or sham operation. To define and characterize putative mediators of myocardial regeneration, we used gene expression analysis, flow cytometry, histology, analysis of macrophage secretome, myocardial organ and cardiomyocyte (CM) cell culture, immunoblot, CM viability assays, and functional in vitro assays. To determine the relevance of our findings to the adult heart, we subjected adult mice to MI and assess temporal changes in left ventricular (LV) remodelling and function by echocardiography, strain imaging, and post-mortem morphometry.
Results: Myocardial injury in the neonatal heart resulted in a massive accumulation of monocytes and macrophages within a day after injury. Gene expression profiling and macrophage secretome from the injured hearts identified high levels of osteopontin (OPN). Subsequently, we observed impaired myocardial regeneration in OPN knockout mouse after AR. Moreover, OPN treatment stimulated cardiac cell outgrowth, proliferation, and migration. In CMs, OPN acted via the receptor CD44 and downstream phosphorylation of the Hippo-Yes-associated protein (YAP) and the extracellular signal-regulated kinase (ERK). OPN treatment translocated YAP into the nucleus, where it stimulated cell cycle through interaction with transcriptional factors and upregulation of cell cycle genes. Finally, single injection of OPN to adult mice significantly improved cardiac remodeling and function after MI.
Conclusions: We have shown, for the first time, that macrophage OPN activate CM cell cycle activity and play a role in myocardial regeneration. Our results suggest a new macrophage-inspired cell-free therapy to optimize infarct repair.