In response to myocardial infarction (MI), cardiac macrophages regulate inflammation and scar formation. We hypothesized that macrophages undergo polarization state changes over the MI time course and assessed macrophage polarization transcriptomic signatures over the first week of MI. C57BL/6 J male mice (3–6 months old) were subjected to permanent coronary artery ligation to induce MI, and macrophages were isolated from the infarct region at days 1, 3, and 7 post-MI. Day 0, no MI resident cardiac macrophages served as the negative MI control. Whole transcriptome analysis was performed using RNA-sequencing on n = 4 pooled sets for each time. Day 1 macrophages displayed a unique pro-inflammatory, extracellular matrix (ECM)-degrading signature. By flow cytometry, day 0 macrophages were largely F4/80highLy6Clow resident macrophages, whereas day 1 macrophages were largely F4/80lowLy6Chigh infiltrating monocytes. Day 3 macrophages exhibited increased proliferation and phagocytosis, and expression of genes related to mitochondrial function and oxidative phosphorylation, indicative of metabolic reprogramming. Day 7 macrophages displayed a pro-reparative signature enriched for genes involved in ECM remodeling and scar formation. By triple in situ hybridization, day 7 infarct macrophages in vivo expressed collagen I and periostin mRNA. Our results indicate macrophages show distinct gene expression profiles over the first week of MI, with metabolic reprogramming important for polarization. In addition to serving as indirect mediators of ECM remodeling, macrophages are a direct source of ECM components. Our study is the first to report the detailed changes in the macrophage transcriptome over the first week of MI. Electronic supplementary materialThe online version of this article (10.1007/s00395-018-0686-x) contains supplementary material, which is available to authorized users.

Cardiac fibroblasts are the major producers of extracellular matrix (ECM) to form infarct scar. We hypothesized that fibroblasts undergo a spectrum of phenotype states over the course of myocardial infarction (MI) from early onset to scar formation. Fibroblasts were isolated from the infarct region of C57BL/6J male mice (3–6 months old, n = 60) at days 0 (no MI control) and 1, 3, or 7 after MI. Whole transcriptome analysis was performed by RNA-sequencing. Of the genes sequenced, 3371 were differentially expressed after MI. Enrichment analysis revealed that MI day 1 fibroblasts displayed pro-inflammatory, leukocyte-recruiting, pro-survival, and anti-migratory phenotype through Tnfrsf9 and CD137 signaling. MI day 3 fibroblasts had a proliferative, pro-fibrotic, and pro-angiogenic profile with elevated Il4ra signaling. MI day 7 fibroblasts showed an anti-angiogenic homeostatic-like myofibroblast profile and with a step-wise increase in Acta2 expression. MI day 7 fibroblasts relied on Pik3r3 signaling to mediate Tgfb1 effects and Fgfr2 to regulate PI3K signaling. In vitro, the day 3 MI fibroblast secretome stimulated angiogenesis, while day 7 MI fibroblast secretome repressed angiogenesis through Thbs1 signaling. Our results reveal novel mechanisms for fibroblasts in expressing pro-inflammatory molecules and regulating angiogenesis following MI.Electronic supplementary materialThe online version of this article (10.1007/s00395-019-0715-4) contains supplementary material, which is available to authorized users.

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Following myocardial infarction (MI), timely resolution of inflammation promotes wound healing and scar formation while limiting excessive tissue damage. Resolution promoting factors (RPFs) are agents that blunt leukocyte trafficking and inflammation, promote necrotic and apoptotic cell clearance, and stimulate scar formation. Previously identified RPFs include mediators derived from lipids (resolvins, lipoxins, protectins, and maresins), proteins (glucocorticoids, annexin A1, galectin 1, and melanocortins), or gases (CO, H2S, and NO). Matrix metalloproteinase-12 (MMP-12; macrophage elastase) has shown promising RPF qualities in a variety of disease states. We review here the evidence that MMP-12 may serve as a novel RPF with potential therapeutic efficacy in the setting of MI.

This study evaluated the effect of feeding a palmitic acid-enriched supplement on production responses and nitrogen metabolism of mid-lactating Holstein and Jersey cows. Eighty mid-lactating dairy cows, 40 Holstein and 40 Jersey, were used in a randomized complete block design with a split-plot arrangement; the main plot was breed and the subplot was fatty acid treatment. Cows within each breed were assigned to 1 of 2 treatments:(1) control diet with no fat supplement or (2) control diet plus a palmitic acid-enriched supplement dosed at 1.5% of diet dry matter (PA treatment). The treatment period was 6 wk with the final 3 wk used for data and sample collection. There were no treatment × breed interactions for the variables analyzed. Compared with control, PA treatment increased milk fat yield (1.36 vs. 1.26 kg/d) and tended to increase 3.5% fat-corrected milk (35.6 vs. 34.0 kg/d) and energy-corrected milk (35.7 vs. 34.1 kg/d). There was no effect of PA treatment on dry matter intake, milk yield, milk protein yield, milk lactose yield, body condition score, body weight (BW) change, nitrogen intake, and variables related to nitrogen metabolism and excretion. Compared with Holstein cows, Jersey cows had greater dry matter intake as a percent of BW (4.90 vs. 3.37% of BW) and lower milk production (29.6 vs. 32.7 kg/d) and milk lactose yield (1.58 vs. 1.42 kg/d), but tended to have greater milk fat yield (1.36 vs. 1.26 kg/d). There was a breed effect on BW change; Holstein cows gained 0.385 kg/d during the experiment, and Jersey cows gained 0.145 kg/d. Jersey cows had lower nitrogen intake (636 vs. 694 g/d), blood urea nitrogen (12.6 vs. 13.8 mg/ dL), urine total nitrogen (125 vs. 145 g/d), and urine total nitrogen as a percent of nitrogen intake (19.5 vs. 21.1%). Overall, feeding a palmitic acid-enriched supplement increased milk fat yield as well as dry matter and fiber digestibility in both Holstein and Jersey cows. The PA treatment did not have any major effects on nitrogen metabolism in both Holstein and Jersey cows. In addition, our results indicated that Jersey cows had lower urinary nitrogen excretion (g/d) than Holstein cows.

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