Cardiac Fibroblasts Secrete Galectin‐1 After Myocardial Infarction to Communicate With Macrophages

Abstract

The cardiac fibroblast is the key cell type regulating scar formation after myocardial infarction (MI). Whether the fibroblast also serves a role in the early pro‐inflammatory phase has not been evaluated. For this study we evaluated secretome from no MI day (D) 0 and MI D1 cardiac fibroblast to understand the roles of D1 fibroblast in cellular communication during the pro‐inflammatory phase of MI wound healing. Cardiac fibroblasts were isolated from day (D) 0 (n=3) left ventricle and MI D1 (n=3) infarct region, and the 24 h secretome was collected from passage 2 cells. We used mass spectrometry to catalogue and quantify the secretome. We identified galectin‐1 as a highly upregulated D1 MI secreted factor. Because galectin‐1 is known in other systems to be anti‐inflammatory, we stimulated bone marrow derived macrophages (1.5x106 cells/ well; n=8 4M/4F paired sets) with galectin‐1 (500 ng/ml) in the presence of interleukin (IL)‐1b (200 ng/ml) or IL‐10 (50 ng/ml). The conditioned media was assayed using proteome profiler mouse XL cytokine array (RnD) and immunoblotting validation. We also used a human glycosylation array 1000 (RayBio) to evaluate plasma from healthy controls (n=18) and patients 48h after MI (n=41). Galectin‐1 was 3‐fold elevated in the MI D1 secretome (p=0.007). Galectin‐1 increased IL‐10 release (p=0.02) in the macrophages treated wtih IL‐10, a finding validated by two methods. In humans, Galectin‐1 was 2.2‐fold increased at 48h after MI compared to healthy controls (p=0.013). In conclusion, the fibroblast secretes galectin‐1 to modulate the macrophage response after MI by stimulating anti‐inflammatory macrophage polarization and potentially improve MI wound healing.