Macrophages promote the transition from myocardial ischemia reperfusion injury to cardiac fibrosis in mice through GMCSF/CCL2/CCR2 and phenotype switching.

Following acute myocardial ischemia reperfusion (MIR), macrophages infiltrate damaged cardiac tissue and alter their polarization phenotype to respond to acute inflammation and chronic fibrotic remodeling. In this study we investigated the role of macrophages in post-ischemic myocardial fibrosis and explored therapeutic targets for myocardial fibrosis. Male mice were subjected to ligation of the left coronary artery for 30 min. We first detected the levels of chemokines in heart tissue that recruited immune cells infiltrating into the heart, and found that granulocyte-macrophage colony-stimulating factor (GMCSF) released by mouse cardiac microvascular endothelial cells (MCMECs) peaked at 6 h after reperfusion, and c-c motif chemokine ligand 2 (CCL2) released by GMCSF-induced macrophages peaked at 24 h after reperfusion. In co-culture of BMDMs with MCMECs, we demonstrated that GMCSF derived from MCMECs stimulated the release of CCL2 by BMDMs and effectively promoted the migration of BMDMs. We also confirmed that GMCSF promoted M1 polarization of macrophages in vitro, while GMCSF neutralizing antibodies (NTABs) blocked CCL2/CCR2 signaling. In MIR mouse heart, we showed that GMCSF activated CCL2/CCR2 signaling to promote NLRP3/caspase-1/IL-1ß-mediated and amplified inflammatory damage. Knockdown of CC chemokine receptor 2 gene (CCR2-/-), or administration of specific CCR2 inhibitor RS102895 (5 mg/kg per 12 h, i.p., one day before MIR and continuously until the end of the experiment) effectively reduced the area of myocardial infarction, and down-regulated inflammatory mediators and NLRP3/Caspase-1/IL-1ß signaling. Mass cytometry confirmed that M2 macrophages played an important role during fibrosis, while macrophage-depleted mice exhibited significantly reduced transforming growth factor-ß (Tgf-ß) levels in heart tissue after MIR. In co-culture of macrophages with fibroblasts, treatment with recombinant mouse CCL2 stimulated macrophages to release a large amount of Tgf-ß, and promoted the release of Col1α1 by fibroblasts. This effect was diminished in BMDMs from CCR2-/- mice. After knocking out or inhibiting CCR2-gene, the levels of Tgf-ß were significantly reduced, as was the level of myocardial fibrosis, and cardiac function was protected. This study confirms that the acute injury to chronic fibrosis transition after MIR in mice is mediated by GMCSF/CCL2/CCR2 signaling in macrophages through NLRP3 inflammatory cascade and the phenotype switching.

Effect of targeted argon-helium cryoablation on the portal region in canine livers / 南方医科大学学报

<p><b>OBJECTIVE</b>To observe the effect of targeted argon-helium cryoablation on portal region of the liver in dogs by observing the pathological changes in the first-order branches of the Glisson ductal system.</p><p><b>METHODS</b>Twelve healthy dogs underwent percutaneous targeted argon-helium cryoablation of the liver and sacrificed at 3 and 28 days after the cryoablation to observe the pathological changes in target area for cryoablation and the first-order branches of the Glisson ductal system.</p><p><b>RESULTS</b>No obvious damage was not found in the vascular wall of the portal vein by gross or microscopic observation, but the liver tissue in the vicinity of the blood vessels showed total necrosis. In spite of the injuries of different degrees in the first-order bile duct system after argon-helium cryoablation, no severe damages such as perforation or full-thickness necrosis occurred in bile duct wall, and most of the injuries were temporary and reversible. The size of the ablated area on day 28 was significantly reduced as compared with that on day 3 following the cryoablation (P<0.05). In the acute stage after the cryoablation (1-3 days), ALT and AST levels increased significantly in (P<0.05) but recovered 1-4 weeks later (P>0.05). The cryoablated area was basically consistent with the pathological area that underwent necrosis (P>0.05).</p><p><b>CONCLUSION</b>Targeted argon-helium cryoablation can cause total destruction of the liver tissue around the blood vessel without damaging the vascular walls of the portal vein. Argon-helium cryoablation induces relatively minor injuries to the bile duct of hepatic portal section and does not obviously damage the liver function, and the scope of tissue necrosis can be estimated according to the size of frozen area observed. Argon-helium cryoablation is a safe and minimally invasive operation with reliable therapeutic effect.</p>