Abstract P126: Pro-Inflammatory Macrophage Secretome Promotes Cardiac Fibroblast Activation

Introduction: Following myocardial infarction, an acute immune response occurs, and infiltrating monocytes and monocyte-derived macrophages migrate into the infarct. Under the influence of intricate pro- and anti-inflammatory stimuli, macrophages drive cardiac fibroblast (CF) activation. The interaction between macrophages and CFs regulates fibrosis-driven wound healing. Hypothesis: We hypothesised that pro- and anti-inflammatory macrophages divergently effect CF activation. We aimed to identify macrophage proteins that regulate CFs as potential intervention targets. Methods: Monocytes from healthy volunteers were differentiated towards pro- or anti-inflammatory macrophages using GM-CSF (20 ng/mL) and M-CSF (20 ng/mL) or M-CSF (40 ng/mL) alone, respectively. CF activation was characterised by α-SMA expression, contraction, and migration. Proteomics were performed on macrophage secretome and subjected to bioinformatics (IPA, Qiagen). CFs were cultured with macrophage-conditioned medium (CM) in the presence of recombinant proteins or neutralising antibodies, as indicated. Results: Pro-inflammatory macrophage CM enhanced CF activation, as evidenced by elevated α-SMA expression (1.6-fold change, pin vitro (33% reduction in 2 hours, 37 o C), which, subsequently, abrogated the suppression of α-SMA expression by CXCL10 in CFs. Conclusions: Our findings indicate that macrophage phenotype exerts divergent effects on CF behaviour, with pro-inflammatory macrophages promoting CF activation, through enhanced CTSZ secretion and associated CXCL10 cleavage, revealing both proteins as potential targets for modulating fibrosis-driven wound healing.