Abstract 513: Exosomes Derived From Podoplanin Positive Cells Induce Fibrosis and Inflammation in Healthy Mouse Heart

Superseding fibrosis is the leading cause of the adverse remodeling after myocardial infarction (MI); inflammation and paracrine signals enhance the fibrosis and ventricular dysfunction and inhibit the favorable repair. It has been reported that cells expressing Podoplanin (PDPN), a platelet aggregation- inducing type I transmembrane glycoprotein, appear around 2 days after MI as a signal of activation. We hypothesized that exosomes derived from these cells may actively affect the biology of fibrosis and inflammation. PDPN+ cells were isolated from hearts of mice 2 days after MI, expanded in a selective media and treated with TNFα, Angiotensin II or the combination of both. Exosomes derived from activated PDPN+ cells were isolated from the conditioned media and used in vitro for the treatment of mouse cardiac endothelial cells (mCECs), mouse embryonal fibroblast (MEF) and monocytes and in vivo for the treatment of healthy mouse hearts. Data from q-PCR showed that stimulated PDPN+ cells derived exosomes reprogramed mCECs to the endothelial lymphatic phenotype enhancing the expression of the major lymphatic lineage markers and upregulated the expression of fibrotic markers suggesting an endothelial-mesenchymal transition. Furthermore, stimulated PDPN+ cells derived exosomes drove the fibroblast to myo-fibroblast phenotype and activated monocytes toward pro-inflammatory lineage with an increased expression of TNFα and IL- 1β. In vivo, stimulated PDPN+ cells derived exosomes were initially injected in to the left ventricle of healthy mouse hearts followed with additional boosters delivered by retro-orbital vein injection. Treated mice developed an extended epicardial fibrosis with a subsequent impairment in the contractility and increase in the end diastolic and systolic volumes. In conclusion stimulated PDPN+ cells derived exosomes may impair the biology of mCECs, fibroblast and monocytes leading to adverse remodeling after MI.