Abstract 413: Podoplanin Neutralization Improves Cardiac Remodeling and Function After Acute Myocardial Infarction

Abstract

Variety of cardioprotective and reparative therapeutic approaches have emerged for the treatment of cardiac remodeling after myocardial infarction (MI). Here we propose a novel mechanism using a neutralizing antibody that target Podoplanin (PDPN), a platelet aggregation-inducing type I transmembrane glycoprotein, expressed on a cohort of myocardial cells that migrate to the infarcted area after MI and contribute significantly to scar formation. The PDPN+ cells were isolated from infarcted hearts two days after MI, using magnetic beads sorting. We tested in vitro the effect of PDPN neutralizing antibody (5μg/ml) in a transwell migration assay and the activation of monocytes co-cultured with PDPN+ cells. The neutralizing antibody decreased significantly PDPN+ cells migration. Monocytes co-cultured with PDPN+ cells produced high levels of IL1α and IL12, whereas treatment of co-cultures with podoplanin neutralizing antibody inhibited IL1α and IL12 production and increased IL9 and IL10 production, suggesting a switch form pro-inflammatory to anti-inlammatory phenotype. To tests the effect of podoplanin neutralizing antibody in vivo, C57BL/6 wild type mice were subjected to experimental MI and anti-PDPN antibody (25μg/ml) was injected i.p. on days 1, 2, 7 and 15 after MI and mice were scarified two months after. At 7 days after MI echocardiography revealed comparable ~30% of ejection fraction (EF) in control and antibody-injected mice. After one month EF% remained unchanged in control group and increased up to 45% in antibody-treated group, suggesting improvement in cardiac function. Histologically, in the control group the ischemic area was composed by fibrotic tissue highly positive for fibronectin and αSMA, whereas in the antibody-treated group revealed large number of survived, as well as proliferating myocytes expressing αSARC-actin and Phospho-H3. Further, there was a significant increase in CD31 positive cells in the infarct border-zone of antibody-treated vs. control hearts, suggesting increased angiogenesis. Our findings suggest that inhibition of PDPN during first two weeks after MI intensely enhances cardiac regeneration and angiogenesis. This may represent a new therapeutic support for the tissue renewal after MI.