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.
This study aimed to analyze the role of endothelial progenitor cell (EPC)-derived angiogenic factors and chemokines in the multistep process driving angiogenesis with a focus on the recently discovered macrophage migration inhibitory factor (MIF)/chemokine receptor axis. Primary murine and murine embryonic EPCs (eEPCs) were analyzed for the expression of angiogenic/chemokines and components of the MIF/CXC chemokine receptor axis, focusing on the influence of hypoxic versus normoxic stimulation. Hypoxia induced an upregulation of CXCR2 and CXCR4 but not CD74 on EPCs and triggered the secretion of CXCL12, CXCL1, MIF, and vascular endothelial growth factor (VEGF). These factors stimulated the transmigration activity and adhesive capacity of EPCs, with MIF and VEGF exhibiting the strongest effects under hypoxia. MIF-, VEGF-, CXCL12-, and CXCL1-stimulated EPCs enhanced tube formation, with MIF and VEGF exhibiting again the strongest effect following hypoxia. Tube formation following in vivo implantation utilizing angiogenic factor-loaded Matrigel plugs was only promoted by VEGF. Coloading of plugs with eEPCs led to enhanced tube formation only by CXCL12, whereas MIF was the only factor which induced differentiation towards an endothelial and smooth muscle cell (SMC) phenotype, indicating an angiogenic and differentiation capacity in vivo. Surprisingly, CXCL12, a chemoattractant for smooth muscle progenitor cells, inhibited SMC differentiation. We have identified a role for EPC-derived proangiogenic MIF, VEGF and MIF receptors in EPC recruitment following hypoxia, EPC differentiation and subsequent tube and vessel formation, whereas CXCL12, a mediator of early EPC recruitment, does not contribute to the remodeling process. By discerning the contributions of key angiogenic chemokines and EPCs, these findings offer valuable mechanistic insight into mouse models of angiogenesis and help to define the intricate interplay between EPC-derived angiogenic cargo factors, EPCs, and the angiogenic target tissue.
Objectives Here we aimed to clarify the role of CXCR2 in the macrophage migration inhibitory factor (MIF)-mediated effects after myocardial ischemia and reperfusion (I/R). As a pleiotropic chemokine-like cytokine, MIF has been identified to activate multiple receptors including CD74 and CXCR2. In models of myocardial infarction (MI), MIF exerts both pro-inflammatory effects and protective effects in cardiomyocytes. Likewise, CXCR2 displays opposing effects in resident versus circulating cells. Approach and results Using bone marrow (BM) transplantation, we generated chimeric mice with CXCR2−/− BM-derived inflammatory cells and wild-type resident cells (wt/CXCR2−/−), with CXCR2−/− cardiomyocytes and wild-type BM-derived cells (CXCR2−/−/wt) and wild-type controls reconstituted with wild-type BM (wt/wt). All groups were treated with anti-MIF or isotype control antibody before they underwent myocardial I/R. Blocking MIF increased infarction size and impaired cardiac function in wt/wt and wt/CXCR2−/− mice but ameliorated functional parameters in CXCR2−/−/wt mice, as analyzed by echocardiography and Langendorff perfusion. Neutrophil infiltration and angiogenesis were unaltered by MIF blockade or CXCR2 deficiency. Monocyte infiltration was blunted in wt/CXCR2−/− mice and reduced by MIF blockade in wt/wt and CXCR2−/−/wt mice. Moreover, MIF blockade attenuated collagen content in all groups in a CXCR2-independent manner. Conclusions The compartmentalized and opposing effects of MIF after myocardial I/R are largely mediated by CXCR2. Whereas MIF confers protective effects improving myocardial healing and function through CXCR2 in resident cells, complementing paracrine effects through CD74/AMPK, it exerts detrimental effects on CXCR2-bearing inflammatory cells, increasing monocyte infiltration and impairing heart function. These dichotomous findings should be considered, when developing novel therapeutic strategies to treat MI.
Cardiovascular diseases, including atherosclerosis and the dreaded complication myocardial infarction, represent the major cause of death in western countries. It is now generally accepted that chemokines tightly control and modulate all the events which lead to initiation and progression of cardiovascular diseases, making them very attractive therapeutic targets for the pharmaceutical industry. Various studies showed until now the effects of antagonizing/ neutralizing chemokines or blocking chemokine receptors on cardiovascular pathology. The modulation of the CCL2/CCR2, CCL5/CCR1-CCR5, CXCL12/CXCR4 pathways by preventing receptor--ligand interaction, chemokine-glycosaminoglycan interaction, heteromerization, or interfering with the signaling pathways has proven to have high potential in future drug development. However, while trying to understand the effects of individual chemokines, the biologic consequences of multiple and concomitant chemokine expression on leukocyte migration and function should be taken into account as well. Therefore, many aspects should be considered and carefully scrutinized, when devising therapeutic strategies.
Myocardial infarction (MI) induces a complex inflammatory immune response, followed by the remodelling of the heart muscle and scar formation. The rapid regeneration of the blood vessel network system by the attraction of hematopoietic stem cells is beneficial for heart function. Despite the important role of chemokines in these processes, their use in clinical practice has so far been limited by their limited availability over a long time-span in vivo. Here, a method is presented to increase physiological availability of chemokines at the site of injury over a defined time-span and simultaneously control their release using biodegradable hydrogels. Two different biodegradable hydrogels were implemented, a fast degradable hydrogel (FDH) for delivering Met-CCL5 over 24 hrs and a slow degradable hydrogel (SDH) for a gradual release of protease-resistant CXCL12 (S4V) over 4 weeks. We demonstrate that the time-controlled release using Met-CCL5-FDH and CXCL12 (S4V)-SDH suppressed initial neutrophil infiltration, promoted neovascularization and reduced apoptosis in the infarcted myocardium. Thus, we were able to significantly preserve the cardiac function after MI. This study demonstrates that time-controlled, biopolymer-mediated delivery of chemokines represents a novel and feasible strategy to support the endogenous reparatory mechanisms after MI and may compliment cell-based therapies.
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:, or Y2Y4 2/2 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 dorsomedial nucleus of the hypothalamus (DMH) are activated with minimal responses seen in the ventromedial nucleus of the hypothalamus (VMH) and lateral hypothalamic area (LHA) of WT mice. These effects are absent in Y2 2/2 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.
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.
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