Role of MMP3 in cardiac microvascular barrier dysfunction and heart failure during sepsis - Project Summary Sepsis is a life-threatening multiorgan dysfunction syndrome caused by a dysregulated response to infection, responsible for over half of hospital deaths and the leading cause of readmissions and hospitalization costs in the US. Heart failure in critically ill sepsis patients has a mortality rate of up to 70%. Despite 40 years of research, there is no effective clinical treatment for sepsis-induced cardiac dysfunction (SICD). Vascular hyperpermeability, a hallmark of sepsis, leads to lung edema and breathing problems, but its role in SICD remains underexplored. Our recent study suggests that protecting microvascular integrity and reducing cardiac edema (fluid accumulation in the myocardium) may improve survival in sepsis. Using genetic analysis (gene sequencing), we found that MMP3 is one of the top regulated genes in septic mouse hearts, with its serum levels significantly increased in septic animal models, consistent with clinical reports. Our data also indicate that serum MMP3 has strong diagnostic value for sepsis, surpassing other common biomarkers tested. However, MMP3’s role in sepsis is not yet fully understood. In our pilot studies, MMP3 knockout (KO) mice showed 1) reduced microvascular leakage, improved cardiac function, and maintained normal blood pressure, 2) increased survival rates above 90%, and 3) reduced levels of pro-inflammatory cytokines (i.e. iNOS, IL-6)). Moreover, MMP3 is predominantly expressed in cardiac endothelial cells, and CRISPR/Cas9-mediated MMP3 deletion in endothelial cells further increased survival following sepsis challenge. Additionally, B1R inhibitor treatment in WT mice reduced MMP3 levels and cardiac microvascular leakage during sepsis. We hypothesize that the endothelial B1R/MMP3 pathway, following sepsis challenge, plays a critical role in inducing cardiac microvascular barrier dysfunction, leading to the development of sepsis-induced heart failure. Overall, our proposed studies aim to identify the critical mechanisms behind sepsis-induced microvascular leakage and demonstrate that MMP3 is a novel therapeutic target for sepsis-induced heart failure. Aim 1 will investigate the role of endothelial MMP3 in regulating cardiac microvascular permeability and function in sepsis, contributing to the development of SICD, using an inducible adult EC-specific MMP3 knockout mouse model and EC-MMP3 overexpression via a novel nanoparticle delivery system developed by Dr. YouYang (Co-I). Aim 2 will define the molecular mechanism by which B1R regulates MMP3, focusing on several pathways, using advanced molecular techniques to establish a direct link between B1R and MMP3. Aim 3 will explore the therapeutic effects of MMP3 inhibition through pharmacological intervention using an MMP3 inhibitor and CRISPR/Cas9-mediated endothelial-specific gene editing. Together, these studies aim to provide a comprehensive understanding of the mechanisms underlying septic heart failure and develop novel therapeutic strategies to reduce cardiac edema, prevent heart failure progression, with the hope of improving the survival of patients with sepsis.
