Abstract 414: Role of Red Blood Cell Derived Extracellular Vesicles in Cardiac Remodeling after Myocardial Infarction in a Transgenic Murine Model

Introduction: Extracellular vesicles (EVs) function as novel mediators of intercellular communication. Here, we describe a novel, fluorescence switch-based, experimental model to study EV-mediated communication between RBCs and the heart that permits characterization of cross-talk between RBCs and cardiomyocytes at homeostasis and after myocardial infarction. Methods: Mice with RBC-specific expression of cre (Erythropoietin Receptor (EpoR) Cre) were crossed with reporter mTmG Rosa26 mice to yield EpoRCre/mTmG off-springs with membrane GFP expression in RBCs and RBC-derived EVs. Cultured dermal fibroblasts from mTmG mice and a mT/floxed/mGFP HEK 293 reporter cell line were used to assess transfer of functional cre in RBC-derived EVs. To determine targets of RBC-EVs, organs from i)EpoRCre/mTmG (n=3), ii) mTmG (n=3) or iii) mTmG mice transfused with RBC-EVs from EpoR-cre mice and targets of RBC-EVs (determined by mGFP expression due to cre-recombination) were assessed by confocal microscopy. Finally, ischemia-reperfusion-infarction (30 min. LAD ligation) was done in EpoRCre/mGmT mice (n=3) and their blood and organs harvested after a span of 4 weeks to analyze changes in quality and quantity of RBC-EV targets following MI. Results: 1. RBC-EVs (mGFP positive) in plasma accounted for about 9% of total fluorescent EVs as detected by nano-flow cytometry and microscopy. 2. RBC-EVs contained cre protein by EM, and in vitro dermal fibroblasts from mTmG mice or mT/floxed/mGFP HEK 293 reporter cells showed mGFP expression with EpoRCre RBC-EVs, suggesting EV-mediated transfer of functional cre. 3. Cre-mediated recombination was noted in diverse organs in EpoRCre/mTmG mice and mTmTG mice transfused with EpoRCre- EVs with the bone marrow, heart, lungs, kidney and spleen showing the largest degree of recombined cells. 4. Target profile of RBC-EVs demonstrates a distinct pattern of EV-mediated communication among the organs at baseline that may be altered in different disease models. Conclusion: We show proof-of-concept for a novel model to study origin and targets of EV-mediated intercellular communication with significant EV-mediated communication between RBCs and cardiomyocytes under homeostatic conditions.