Program Director/Principal Investigator (Last, First, Middle): GUAN, JIANJUN Project Summary Following myocardial infarction (MI, or heart attack), the prolonged inflammation due to delayed transition of proinflammatory phase to anti-inflammatory phase, and uncontrolled cardiac fibrosis following myofibroblast differentiation, deteriorate cardiac function. As such, timely transitioning the proinflammatory phase to the anti- inflammatory phase, and inhibiting myofibroblast formation will improve cardiac function. However, the effective therapies to simultaneously achieve both goals remain to be established. Currently, systemic delivery of anti- inflammatory agents did not show consistent outcomes in clinical trials, mainly because the drugs either inhibit cardiac repair or are not delivered in a spatiotemporal manner to effectively target specific inflammatory signals. To attenuate cardiac fibrosis, systemic delivery of TGFβ inhibitors and antibodies represents a major strategy. Yet, the efficacy is not satisfactory because these therapies cannot essentially inhibit TGFβ pathway, and also cannot simultaneously prevent other major pathways-induced myofibroblast formation, e.g., IL-1 pathway. In this project, we propose a new approach to address the above limitations. We will directly deliver, at acute MI stage, secretome of M2 macrophages (M2Mφs), a dominated cell type in the anti-inflammatory phase, to timely decrease inflammation in the infarcted hearts. Besides anti-inflammation function, we found that M2Mφ-secretome increases cardiac cell survival and promotes angiogenesis in the infarcted hearts. Thus, it is multifunctional. Yet, M2Mφ-secretome has not been explored for cardiac therapy before. To prevent cardiac fibrosis, we propose to deliver a newly synthesized, peptide-based inhibitor RPE that simultaneously inhibits TGFβ and IL-1 pathways-induced myofibroblast differentiation. Our preliminary studies demonstrate that RPE significantly reduced myofibroblast density in the infarcted hearts. To the best of our knowledge, there is no known inhibitors that simultaneously inhibit these 2 pathways. To deliver the M2Mφ-secretome and RPE into infarcted hearts at the critical time window to attenuate inflammation and myofibroblast formation - acute MI stage, while considering that direct myocardial injection has safety concerns at this stage, we will deliver them by IV injection, after encapsulating them into infarcted heart-targeting nanoparticles. These nanoparticles will specifically accumulate in infarcted hearts following IV injection. They will then spatiotemporally release M2Mφ-secretome and RPE. We hypothesize that IV delivery of infarcted heart-targeting nanoparticles capable of releasing M2Mφ-secretome, and RPE at the acute MI stage will efficiently decrease tissue inflammation, increase cardiac cell survival, promote angiogenesis, and attenuate cardiac fibrosis, leading to a significant increase of cardiac function. AIM 1 will test...