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Myocardial infarction is remains the leading cause of death in developed countries. Recent data show that the composition of the extracellular matrix might differ despite similar heart function and infarction sizes. Because collagen is the main component of the extracellular matrix, we hypothesized that changes in inflammatory cell recruitment influence the synthesis of different collagen subtypes in myofibroblasts, thus changing the composition of the scar. We found that neutrophils sustain the proliferation of fibroblasts, remodeling, differentiation, migration and inflammation, predominantly by IL-1 and PPARγ pathways (n = 3). They also significantly inhibit the mRNA expression of fibrillar collagen, maintaining a reduced stiffness in isolated myofibroblasts (n = 4–5). Reducing the neutrophil infiltration in CCR1−/− resulted in increased mRNA expression of collagen 11, moderate expression of collagen 19 and low expression of collagen 13 and 26 in the scar 4 weeks post infarction compared with other groups (n = 3). Mononuclear cells increased the synthesis of all collagen subtypes and upregulated the NF-kB, angiotensin II and PPARδ pathways (n = 3). They increased the synthesis of collagen subtypes 1, 3, 5, 16 and 23 but reduced the expression of collagens 5 and 16 (n = 3). CCR2−/− scar tissue showed higher levels of collagen 13 (n = 3), in association with a significant reduction in stiffness (n = 4–5). Upregulation of the inflammation-related genes in myofibroblasts mostly modulated the fibrillar collagen subtypes, with less effect on the FACIT, network-forming and globular subtypes (n = 3). The upregulation of proliferation and differentiation genes in myofibroblasts seemed to be associated only with the fibrillar collagen subtype, whereas angiogenesis-related genes are associated with fibrillar, network-forming and multiplexin subtypes. In conclusion, although we intend for our findings to deepen the understanding of the mechanism of healing after myocardial infarction and scar formation, the process of collagen synthesis is highly complex, and further intensive investigation is needed to put together all the missing puzzle pieces in this still incipient knowledge process. [ABSTRACT FROM AUTHOR]

Objective Peptide YY (PYY3-36) and pancreatic polypeptide (PP) potently inhibit food intake in rodents and humans, however, it is unclear whether they have any synergistic/additive interaction in decreasing food intake. Design and Methods Fasted WT, Y2−/−, Y4−/−, or Y2Y4−/− mice were i.p. administrated with saline, PYY3-36, and/or PP. Results Combined injection of PYY3-36 and PP reduces food intake in an additive manner was demonstrated in this study. This effect is mediated via Y2 and Y4 receptors, respectively. It was demonstrated that PYY3-36 and PP activate distinct neuronal pathways in the hypothalamus, as demonstrated by immunostaining for c-fos, which shows distinct patterns in response to either hormone. After PYY3-36 injection, neurons in the dorsal aspect of the arcuate nucleus (Arc), paraventricular nucleus, and dorso-medial nucleus of the hypothalamus (DMH) are activated with minimal responses seen in the ventro-medial nucleus of the hypothalamus (VMH) and lateral hypothalamic area (LHA) of WT mice. These effects are absent in Y2−/− mice. PP activates preferably the lateral aspect of the Arc, the DMH, VMH, and LHA in a Y4 receptor-dependent manner. Importantly, the expression pattern of c-fos immunoreactive neurons induced by combined treatment appears to be the sum of the effects of single treatments rather than a result of synergistic interaction. Conclusions These findings demonstrate that PYY3-36 and PP activate distinct pathways in the hypothalamus to reduce food intake in an additive manner. [ABSTRACT FROM AUTHOR]

Abstract: Background: Chemokines and neutrophils, known as important players in the inflammatory cascade, also contribute to heart tissue recovery and scar formation after myocardial infarction (MI). The objective of this study was to determine the importance of ELR-containing CXC chemokine KC in neutrophil infiltration and neoangiogenesis, in a mouse model of chronic MI. Methods and results: MI was induced in mice divided in four groups: control (untreated), anti-KC “later” (anti-KC antibody injections started 4days after MI and then delivered every 72hours for 3weeks, to inhibit angiogenesis), anti-KC “earlier” (anti-KC antibody injections 1day before and 1day after MI, to block neutrophil infiltration), anti-KC (anti-KC antibody injections 1day before and 1day after MI, and then every 72hours for 3weeks). The efficiency of the anti-KC treatment was determined by the measurement of KC serum concentration and immunofluorescence staining, in each of the four groups. Surprisingly, we did not find any difference in neutrophil infiltration in the infarcted area between untreated and treated animals. Moreover, the heart function, infarct size, and neoangiogenesis were not different between the four groups. As expected, a comparable anti-CXCR2 treatment of mice before and after MI was able to significantly reduce neutrophil infiltration into the infarcted area and angiogenesis, but also to reduce the infarction size after long or “later” treatment. Conclusions: The major finding of our study is that KC, a potent neutrophil chemoattractant and an established angiogenic factor, failed to interfere in the post-infarction inflammatory response, in wound healing and scar formation after MI. Therefore, these aspects need to be carefully taken into account when devising therapeutic strategies for myocardial infarction and ischemic cardiomyopathy. [Copyright &y& Elsevier]

Suitable and reproducible experimental models of translational research in reconstructive surgery that allow in-vivo investigation of diverse molecular and cellular mechanisms are still limited. To this end we created a novel murine model of acute hindlimb ischemia-reperfusion to mimic a microsurgical free flap procedure. Thirty-six C57BL6 mice (n = 6/group) were assigned to one control and five experimental groups (subject to 6, 12, 96, 120 hours and 14 days of reperfusion, respectively) following 4 hours of complete hindlimb ischemia. Ischemia and reperfusion were monitored using Laser-Doppler Flowmetry. Hindlimb tissue components (skin and muscle) were investigated using histopathology, quantitative immunohistochemistry and immunofluorescence. Despite massive initial tissue damage induced by ischemia-reperfusion injury, the structure of the skin component was restored after 96 hours. During the same time, muscle cells were replaced by young myotubes. In addition, initial neuromuscular dysfunction, edema and swelling resolved by day 4. After two weeks, no functional or neuromuscular deficits were detectable. Furthermore, upregulation of VEGF and tissue infiltration with CD34-positive stem cells led to new capillary formation, which peaked with significantly higher values after two weeks. These data indicate that our model is suitable to investigate cellular and molecular tissue alterations from ischemia-reperfusion such as occur during free flap procedures. [ABSTRACT FROM AUTHOR]

Objectives: Here we assess the intrinsic functions of the chemokine receptor CXCR4 in remodeling after myocardial infarction (MI) using Cxcr4 heterozygous (Cxcr4 +/−) mice. Background: Myocardial necrosis triggers complex remodeling and inflammatory changes. The chemokine CXCL12 has been implicated in protection and therapeutic regeneration after MI through recruiting angiogenic outgrowth cells, improving neovascularization and cardiac function, but the endogenous role of its receptor CXCR4 is unknown. Methods: MI was induced by ligation of the left descending artery. Langendoff perfusion, echocardiography, quantitative immunohistochemistry, flow cytometry, angiogenesis assays, and cardiomyocyte analysis were performed. Results: After 4 weeks, infarct size was reduced in Cxcr4 +/− mice compared with wild-type mice and in respective bone marrow chimeras compared with controls. This was associated with altered inflammatory cell recruitment, decreased neutrophil content, delayed monocyte infiltration, and a predominance of Gr1low over classic Gr1high monocytes. Basal coronary flow and its recovery after MI were impaired in Cxcr4 +/−mice, paralleled by reduced angiogenesis, myocardial vessel density, and endothelial cell count. Notably, no differences in cardiac function were seen in Cxcr4 +/−mice compared with wild-type mice. Despite defective angiogenesis, Cxcr4 +/− mouse hearts showed no difference in CXCL12, vascular endothelial growth factor or apoptosis-related gene expression. Electron microscopy revealed lipofuscin-like lipid accumulation in Cxcr4 +/− mouse hearts and analysis of lipid extracts detected high levels of phosphatidylserine, which protect cardiomyocytes from hypoxic stress in vitro. Conclusions: CXCR4 plays a crucial role in endogenous remodeling processes after MI, contributing to inflammatory/progenitor cell recruitment and neovascularization, whereas its deficiency limits infarct size and causes adaptation to hypoxic stress. This should be carefully scrutinized when devising therapeutic strategies involving the CXCL12/CXCR4 axis. [Copyright &y& Elsevier]