High-fidelity porcine models of metabolic syndrome: a contemporary synthesis.

This review aims to describe and compare porcine models of metabolic syndrome. This syndrome and its associated secondary comorbidities are set to become the greatest challenge to healthcare providers and policy makers in the coming century. However, an incomplete understanding of the pathogenesis has left significant knowledge gaps in terms of efficacious therapeutics. To further our comprehension and, in turn, management of metabolic syndrome, appropriate high-fidelity models of the disease complex are of great importance. In this context, our review aims to assess the most promising porcine models of metabolic syndrome currently available for their similarity to the human phenotype. In addition, we aim to highlight the strengths and shortcomings of each model in an attempt to identify the most appropriate application of each. Although no porcine model perfectly recapitulates the human metabolic syndrome, several pose satisfactory approximations. The Ossabaw miniature swine in particular represents a highly translatable model that develops each of the core parameters of the syndrome with many of the associated secondary comorbidities. Future high-fidelity porcine models of metabolic syndrome need to focus on secondary sequelae replication, which may require extended induction period to reveal.

Gut microbiome of a porcine model of metabolic syndrome and HF-pEF.

Metabolic syndrome (MetS) is a composite of cardiometabolic risk factors, including obesity, dyslipidemia, hypertension, and insulin resistance, with a range of secondary sequelae such as nonalcoholic fatty liver disease and diastolic heart failure. This syndrome has been identified as one of the greatest global health challenges of the 21st century. Herein, we examine whether a porcine model of diet- and mineralocorticoid-induced MetS closely mimics the cardiovascular, metabolic, gut microbiota, and functional metataxonomic phenotype observed in human studies. Landrace pigs with deoxycorticosterone acetate-induced hypertension fed a diet high in fat, salt, and sugar over 12 wk were assessed for hyperlipidemia, hyperinsulinemia, and immunohistologic, echocardiographic, and hemodynamic parameters, as well as assessed for microbiome phenotype and function through 16S rRNA metataxonomic and metabolomic analysis, respectively. All MetS animals developed obesity, hyperlipidemia, insulin resistance, hypertension, fatty liver, structural cardiovascular changes including left ventricular hypertrophy and left atrial enlargement, and increased circulating saturated fatty acid levels, all in keeping with the human phenotype. A reduction in α-diversity and specific microbiota changes at phylum, family, and genus levels were also observed in this model. Specifically, this porcine model of MetS displayed increased abundances of proinflammatory bacteria coupled with increased circulating tumor necrosis factor-α and increased secondary bile acid-producing bacteria, which substantially impacted fibroblast growth factor-19 expression. Finally, a significant decrease in enteroprotective bacteria and a reduction in short-chain fatty acid-producing bacteria were also noted. Together, these data suggest that diet and mineralocorticoid-mediated development of biochemical and cardiovascular stigmata of metabolic syndrome in pigs leads to temporal gut microbiome changes that mimic key gut microbial population signatures in human cardiometabolic disease.NEW & NOTEWORTHY This study extends a prior porcine model of cardiometabolic syndrome to include systemic inflammation, fatty liver, and insulin sensitivity. Gut microbiome changes during evolution of porcine cardiometabolic disease recapitulate those in human subjects with alterations in gut taxa associated with proinflammatory bacteria, bile acid, and fatty acid pathways. This clinical scale model may facilitate design of future interventional trials to test causal relationships between gut dysbiosis and cardiometabolic syndrome at a systemic and organ level.

Lactobacillus mucosae DPC 6426 as a bile-modifying and immunomodulatory microbe.

BACKGROUND: Lactobacillus mucosae DPC 6426 has previously demonstrated potentially cardio-protective properties, in the form of dyslipidaemia and hypercholesterolemia correction in an apolipoprotein-E deficient mouse model. This study aims to characterise the manner in which this microbe may modulate host bile pool composition and immune response, in the context of cardiovascular disease. Lactobacillus mucosae DPC 6426 was assessed for bile salt hydrolase activity and specificity. The microbe was compared against several other enteric strains of the same species, as well as a confirmed bile salt hydrolase-active strain, Lactobacillus reuteri APC 2587. RESULTS: Quantitative bile salt hydrolase assays revealed that enzymatic extracts from Lactobacillus reuteri APC 2587 and Lactobacillus mucosae DPC 6426 demonstrate the greatest activity in vitro. Bile acid profiling of porcine and murine bile following incubation with Lactobacillus mucosae DPC 6426 confirmed a preference for hydrolysis of glyco-conjugated bile acids. In addition, the purified exopolysaccharide and secretome of Lactobacillus mucosae DPC 6426 were investigated for immunomodulatory capabilities using RAW264.7 macrophages. Gene expression data revealed that both fractions stimulated increases in interleukin-6 and interleukin-10 gene transcription in the murine macrophages, while the entire secretome was necessary to increase CD206 transcription. Moreover, the exopolysaccharide elicited a dose-dependent increase in nitric oxide and interleukin-10 production from RAW264.7 macrophages, concurrent with increased tumour necrosis factor-α secretion at all doses. CONCLUSIONS: This study indicates that Lactobacillus mucosae DPC 6426 modulates both bile pool composition and immune system tone in a manner which may contribute significantly to the previously identified cardio-protective phenotype.

Randomized placebo controlled trial evaluating the safety and efficacy of single low-dose intracoronary insulin-like growth factor following percutaneous coronary intervention in acute myocardial infarction (RESUS-AMI).

BACKGROUND: Residual and significant postinfarction left ventricular (LV) dysfunction, despite technically successful percutaneous coronary intervention (PCI) for ST-elevation myocardial infarction (STEMI), remains an important clinical issue. In preclinical models, low-dose insulin-like growth factor 1 (IGF1) has potent cytoprotective and positive cardiac remodeling effects. We studied the safety and efficacy of immediate post-PCI low-dose intracoronary IGF1 infusion in STEMI patients. METHODS: Using a double-blind, placebo-controlled, multidose study design, we randomized 47 STEMI patients with significantly reduced (≤40%) LV ejection fraction (LVEF) after successful PCI to single intracoronary infusion of placebo (n = 15), 1.5 ng IGF1 (n = 16), or 15 ng IGF1 (n = 16). All received optimal medical therapy. Safety end points were freedom from hypoglycemia, hypotension, or significant arrhythmias within 1 hour of therapy. The primary efficacy end point was LVEF, and secondary end points were LV volumes, mass, stroke volume, and infarct size at 2-month follow-up, all assessed by magnetic resonance imaging. Treatment effects were estimated by analysis of covariance adjusted for baseline (24 hours) outcome. RESULTS: No significant differences in safety end points occurred between treatment groups out to 30 days (χ2 test, P value = .77). There were no statistically significant differences in baseline (24 hours post STEMI) clinical characteristics or LVEF among groups. LVEF at 2 months, compared to baseline, increased in all groups, with no statistically significant differences related to treatment assignment. However, compared with placebo or 1.5 ng IGF1, treatment with 15 ng IGF1 was associated with a significant improvement in indexed LV end-diastolic volume (P = .018), LV mass (P = .004), and stroke volume (P = .016). Late gadolinium enhancement (±SD) at 2 months was lower in 15 ng IGF1 (34.5 ± 29.6 g) compared to placebo (49.1 ± 19.3 g) or 1.5 ng IGF1 (47.4 ± 22.4 g) treated patients, although the result was not statistically significant (P = .095). CONCLUSIONS: In this pilot trial, low-dose IGF1, given after optimal mechanical reperfusion in STEMI, is safe but does not improve LVEF. However, there is a signal for a dose-dependent benefit on post-MI remodeling that may warrant further study.

A Novel Selectable Islet 1 Positive Progenitor Cell Reprogrammed to Expandable and Functional Smooth Muscle Cells.

Disorders affecting smooth muscle structure/function may require technologies that can generate large scale, differentiated and contractile smooth muscle cells (SMC) suitable for cell therapy. To date no clonal precursor population that provides large numbers of differentiated SMC in culture has been identified in a rodent. Identification of such cells may also enhance insight into progenitor cell fate decisions and the relationship between smooth muscle precursors and disease states that implicate differentiated SMC. In this study, we used classic clonal expansion techniques to identify novel self-renewing Islet 1 (Isl-1) positive primitive progenitor cells (PPC) within rat bone marrow that exhibited canonical stem cell markers and preferential differentiation towards a smooth muscle-like fate. We subsequently used molecular tagging to select Isl-1 positive clonal populations from expanded and de novo marrow cell populations. We refer to these previously undescribed cells as the PPC given its stem cell marker profile, and robust self-renewal capacity. PPC could be directly converted into induced smooth muscle cells (iSMC) using single transcription factor (Kruppel-like factor 4) knockdown or transactivator (myocardin) overexpression in contrast to three control cells (HEK 293, endothelial cells and mesenchymal stem cells) where such induction was not possible. iSMC exhibited immuno- and cytoskeletal-phenotype, calcium signaling profile and contractile responses similar to bona fide SMC. Passaged iSMC could be expanded to a scale sufficient for large scale tissue replacement. PPC and reprogramed iSMC so derived may offer future opportunities to investigate molecular, structure/function and cell-based replacement therapy approaches to diverse cardiovascular, respiratory, gastrointestinal, and genitourinary diseases that have as their basis smooth muscle cell functional aberrancy or numerical loss. Stem Cells 2016;34:1354-1368.

Selective M2 Macrophage Depletion Leads to Prolonged Inflammation in Surgical Wounds.

BACKGROUND: A prolonged inflammatory phase is seen in aberrant wound healing and in chronic wounds. Macrophages are central to wound healing. Distinct macrophage subtypes have differing roles both in initial inflammation and in later tissue repair. Broadly, these cells can be divided into M1 and M2 macrophages. M2 macrophage proliferation and differentiation is regulated by colony-stimulating factor 1 (CSF-1) signalling and can be blocked by GW2580, a competitive cFMS kinase inhibitor, thereby allowing for analysis of the effect of M2 blockade on progression of surgical wounds. MATERIALS AND METHODS: Macrophage Fas-induced apoptosis (MaFIA) transgenic mice with a macrophage-specific promoter used to express green fluorescent protein (GFP) were used to allow for cell tracking. The animals were treated by oral gavage with GW2580. Surgical wounds were created and harvested after 2 weeks for analysis. RESULTS: GW2580-treated mice had significantly more GFP+ cells in the surgical scar than vehicle-treated animals (GW2580, 68.0 ± 3.1%; vehicle, 42.8 ± 1.7%; p < 0.001), and GW2580 treatment depleted CD206+ M2 macrophages in the scar (GW2580, 1.4%; vehicle, 19.3%; p < 0.001). Treated animals showed significantly higher numbers of neutrophils (vehicle, 18.0%; GW2580, 51.3%; p < 0.01) and M1 macrophages (vehicle, 3.8%; GW2580, 12.8%; p < 0.01) in the scar compared to vehicle-treated animals. The total collagen content in the area of the scar was decreased in animals treated with GW2580 as compared to those treated with vehicle alone (GW2580, 67.1%; vehicle, 79.9%; p < 0.005). CONCLUSIONS: Depletion of M2 macrophages in surgical wounds via CSF-1 signalling blockade leads to persistent inflammation, with an increase in neutrophils and M1 macrophages and attenuated collagen deposition.

Bone Marrow-Derived Mesenchymal Stem Cells Have Innate Procoagulant Activity and Cause Microvascular Obstruction Following Intracoronary Delivery: Amelioration by Antithrombin Therapy.

Mesenchymal stem cells (MSCs) are currently under investigation as tools to preserve cardiac structure and function following acute myocardial infarction (AMI). However, concerns have emerged regarding safety of acute intracoronary (IC) MSC delivery. This study aimed to characterize innate prothrombotic activity of MSC and identify means of its mitigation toward safe and efficacious therapeutic IC MSC delivery post-AMI. Expression of the initiator of the coagulation cascade tissue factor (TF) on MSC was detected and quantified by immunofluorescence, FACS, and immunoblotting. MSC-derived TF antigen was catalytically active and capable of supporting thrombin generation in vitro. Addition of MSCs to whole citrated blood enhanced platelet thrombus deposition on collagen at arterial shear, an effect abolished by heparin coadministration. In a porcine AMI model, IC infusion of 25 × 10(6) MSC during reperfusion was associated with a decrease in coronary flow reserve but not when coadministered with an antithrombin agent (heparin). Heparin reduced MSC-associated thrombosis incorporating platelets and VWF within the microvasculature. Heparin-assisted therapeutic MSC delivery also reduced apoptosis in the infarct border zone at 24 hours, significantly improved infarct size, left ventricular (LV) ejection fraction, LV volumes, wall motion, and attenuated histologic evidence of scar formation at 6 weeks post-AMI. Heparin alone or heparin-assisted fibroblast control cell delivery had no such effect. Procoagulant TF activity of therapeutic MSCs is associated with reductions in myocardial perfusion when delivered IC may be successfully managed by heparin coadministration. This study highlights an important mechanistic insight into safety concerns associated with therapeutic IC MSC delivery for AMI.

Functional food addressing heart health: do we have to target the gut microbiota?

PURPOSE OF REVIEW: Health promoting functional food ingredients for cardiovascular health are generally aimed at modulating lipid metabolism in consumers. However, significant advances have furthered our understanding of the mechanisms involved in development, progression, and treatment of cardiovascular disease. In parallel, a central role of the gut microbiota, both in accelerating and attenuating cardiovascular disease, has emerged. RECENT FINDINGS: Modulation of the gut microbiota, by use of prebiotics and probiotics, has recently shown promise in cardiovascular disease prevention. Certain prebiotics can promote a short chain fatty acid profile that alters hormone secretion and attenuates cholesterol synthesis, whereas bile salt hydrolase and exopolysaccharide-producing probiotics have been shown to actively correct hypercholesterolemia. Furthermore, specific microbial genera have been identified as potential cardiovascular disease risk factors. This effect is attributed to the ability of certain members of the gut microbiota to convert dietary quaternary amines to trimethylamine, the primary substrate of the putatively atherosclerosis-promoting compound trimethylamine-N-oxide. In this respect, current research is indicating trimethylamine-depleting Achaea - termed Archeabiotics as a potential novel dietary strategy for promoting heart health. SUMMARY: The microbiota offers a modifiable target, which has the potential to progress or prevent cardiovascular disease development. Whereas host-targeted interventions remain the standard, current research implicates microbiota-mediated therapies as an effective means of modulating cardiovascular health.

Synthetic chemically modified mrna-based delivery of cytoprotective factor promotes early cardiomyocyte survival post-acute myocardial infarction.

To extend the temporal window for cytoprotection in cardiomyocytes undergoing apoptosis after hypoxia and myocardial infarction (MI), a synthetic chemically modified mRNA (modRNA) was used to drive delivery of insulin-like growth factor-1 (IGF1) within the area at risk in an in vivo murine model of MI. Delivery of IGF1 modRNA, with a polyethylenimine-based nanoparticle, augmented secreted and cell-associated IGF1, promoting cardiomyocyte survival and abrogating cell apoptosis under hypoxia-induced apoptosis conditions. Translation of modRNA-IGF1 was sufficient to induce downstream increases in the levels of Akt and Erk phosphorylation. Downregulation of IGF1 specific miRNA-1 and -133 but not miR-145 expression was also confirmed. As a proof of concept, intramyocardial delivery of modRNA-IGF1 but not control modRNA-GFP significantly decreased the level of TUNEL positive cells, augmented Akt phosphorylation, and decreased caspase-9 activity within the infarct border zone 24 h post-MI. These findings demonstrate the potential for an extended cytoprotective effect of transient IGF1 driven by synthetic modRNA delivery.

Identification of a Klf4-dependent upstream repressor region mediating transcriptional regulation of the myocardin gene in human smooth muscle cells.

Phenotypic switching of smooth muscle cells (SMCs) plays a central role in the development of vascular diseases such as atherosclerosis and restenosis. However, the factors regulating expression of the human myocardin (Myocd) gene, the master gene regulator of SMC differentiation, have yet to be identified. In this study, we sought to identify the critical factors regulating Myocd expression in human SMCs. Using deletion/genetic reporter analyses, an upstream repressor region (URR) was localised within the Myocd promoter, herein termed PrmM. Bioinformatic analysis revealed three evolutionary conserved Klf4 sites within the URR and disruption of those elements led to substantial increases in PrmM-directed gene expression. Furthermore, ectopic expression established that Klf4 significantly decreased Myocd mRNA levels and PrmM-directed gene expression while electrophoretic mobility shift assays and chromatin immunoprecipitation (ChIP) assays confirmed specific binding of endogenous Klf4, and not Klf5 or Klf2, to the URR of PrmM. Platelet-derived growth factor BB (PDGF-BB), a potent inhibitor of SMC differentiation, reduced Myocd mRNA levels and PrmM-directed gene expression in SMCs. A PDGF-BB-responsive region (PRR) was also identified within PrmM, overlapping with the previously identified URR, where either siRNA knockdown of Klf4 or the combined disruption of the Klf4 elements completely abolished PDGF-BB-mediated repression of PrmM-directed gene expression in SMCs. Moreover, ChIP analysis established that PDGF-BB-induced repression of Myocd gene expression is most likely regulated by enhanced binding of Klf4 and Klf5 to a lesser extent, to the PRR of PrmM. Taken together, these data provide critical insights into the transcriptional regulation of the Myocd gene in vascular SMCs, including during SMC differentiation.

Exopolysaccharide-producing probiotic Lactobacilli reduce serum cholesterol and modify enteric microbiota in ApoE-deficient mice.

BACKGROUND: Probiotic bacteria have been associated with a reduction in cardiovascular disease risk, a leading cause of death and disability. OBJECTIVES: The aim of this study was to assess the impact of dietary administration of exopolysaccharide-producing probiotic Lactobacillus cultures on lipid metabolism and gut microbiota in apolipoprotein E (apoE)-deficient mice. METHODS: First, we examined lipid metabolism in response to dietary supplementation with recombinant ß-glucan-producing Lactobacillus paracasei National Food Biotechnology Centre (NFBC) 338 expressing the glycosyltransferase (Gtf) gene from Pediococcus parvulus 2.6 (GTF), and naturally exopolysaccharide-producing Lactobacillus mucosae Dairy Product Culture Collection (DPC) 6426 (DPC 6426) compared with the non-ß-glucan-producing isogenic control strain Lactobacillus paracasei NFBC 338 (PNZ) and placebo (15% wt:vol trehalose). Second, we examined the effects on the gut microbiota of dietary administration of DPC 6426 compared with placebo. Probiotic Lactobacillus strains at 1 × 10(9) colony-forming units/d per animal were administered to apoE(-/-) mice fed a high-fat (60% fat)/high-cholesterol (2% wt:wt) diet for 12 wk. At the end of the study, aortic plaque development and serum, liver, and fecal variables involved in lipid metabolism were analyzed, and culture-independent microbial analyses of cecal content were performed. RESULTS: Total cholesterol was reduced in serum (P < 0.001; ∼33-50%) and liver (P < 0.05; ∼30%) and serum triglyceride concentrations were reduced (P < 0.05; ∼15-25%) in mice supplemented with GTF or DPC 6426 compared with the PNZ or placebo group, respectively. In addition, dietary intervention with GTF led to increased amounts of fecal cholesterol excretion (P < 0.05) compared with all other groups. Compositional sequencing of the gut microbiota revealed a greater prevalence of Porphyromonadaceae (P = 0.001) and Prevotellaceae (P = 0.001) in the DPC 6426 group and lower proportions of Clostridiaceae (P < 0.05), Peptococcaceae (P < 0.001), and Staphylococcaceae (P < 0.01) compared with the placebo group. CONCLUSION: Ingestion of exopolysaccharide-producing lactobacilli resulted in seemingly favorable improvements in lipid metabolism, which were associated with changes in the gut microbiota of mice.

Potent endothelial progenitor cell-conditioned media-related anti-apoptotic, cardiotrophic, and pro-angiogenic effects post-myocardial infarction are mediated by insulin-like growth factor-1.

AIMS: We have previously reported the cardioprotective effects of endothelial progenitor cell (EPC)-conditioned media (CM) therapy post-myocardial infarction (MI). In the present study, we have determined the insulin-like growth factor-1 (IGF-1) contribution to EPC CM effects on cardiomyocyte survival, contractility, and angiogenesis in vivo. METHODS AND RESULTS: Conditioned media from porcine EPC were administered intracoronary in the presence and absence of specific neutralizing antibodies to IGF-1 or control IgG in a porcine model of MI. X-vivo (non-conditioned) medium was used as a control. Functional, histological, and biochemical parameters were evaluated at 24 h and 8-week post-therapy. Conditioned media therapy significantly abrogated infarct zone (IZ) apoptosis, hypocontractility, and impaired left ventricular (LV) relaxation observed in control infarcts acutely (24 h post-MI). At 8 weeks following treatment, CM therapy augmented LV contractility and relaxation, IZ angiogenesis and inhibited infarct size expansion, wall expansion, and wall thinning. All of these acute and chronic beneficial effects of CM therapy were vitiated by neutralizing antibodies to IGF-1 but not by control IgG. Moreover, the addition of neutralizing IGF-1 antibody to control medium had no effect on these structural or functional changes in the heart post-treatment. CONCLUSION: Insulin-like growth factor-1 within the EPC CM mediates potent acute myocardial repair and chronic remodelling effects post-MI. These findings may provide a rationale for comparative trials of specific growth factors vs. current progenitor cell strategies.

Differential endothelial coverage, response to injury and neointimal integration of CX3CR1/smooth muscle-like cells after carotid or femoral arterial injury.

BACKGROUND: Previously, we established the importance of the CX3CL1/CX3CR1 axis in the promotion of myeloid cell differentiation into neointimal smooth muscle-like cells (SMLC). METHODS: In this study, acute (24 h) endothelial coverage and CX3CL1 expression as well as chronic (2 weeks) vascular remodeling was examined with respect to whether myeloid CX3CR1(+) SMLC number in the neointima differed between carotid and femoral artery wire injury. RESULTS AND CONCLUSION: Twenty-four hours after injury, CX3CL1 expression was significantly elevated in injured carotid compared to femoral arteries. In mice with CX3CR1 promoter-driven expression of green fluorescent protein, neointima formation was significantly greater (p < 0.05) 2 weeks after injury in femoral versus carotid arteries as determined by the intima/media ratio. Although the percentage of F4/80/CX3CR1(+) cell integration was similar in both models, the carotid lesion had greater proportions of cells coexpressing CX3CR1 and both α-smooth muscle actin and calponin (p < 0.05). Wire injury of carotid arteries was associated with greater CX3CL1 expression in the acute phase followed by greater CX3CR1 coexpressing SMLC content in later lesions as well as less neointima formation than in femoral arteries. This may, in part, explain the variability in lesion composition after carotid versus femoral wire injury.

Calcium signalling in adult endothelial outgrowth cells.

Endothelial outgrowth cells (EOCs) derived from blood mononuclear cells can differentiate to an endothelial-like phenotype. There are deficits in understanding of the biology of these cells, particularly detailed characterisation of their Ca(2+) signalling mechanisms. In the current study, it was found that human EOCs express two forms of ryanodine receptor (RyR1 and RyR2) Ca(2+) release channel in their endoplasmic reticulum. Individual EOCs display heterogeneous Ca(2+) responses to physiologically relevant regulators fibrinogen and collagen. Some EOCs showed distinctive, multiphasic Ca(2+) responses to fibrinogen consisting of rapid decreases, transient increases then a gradual return to the resting levels. Transient elevations in Ca(2+) required both L-type voltage gated calcium channels and RyRs. Decreases in Ca(2+) stimulated by fibrinogen depended on plasma membrane Ca(2+) ATPase pumps, but did not require thapsigargin-sensitive Ca(2+) ATPases. These results indicate that EOCs possess sophisticated Ca(2+) signalling mechanisms, capable of generating distinct Ca(2+) waveforms in response to different physiologically relevant cues.

Microbial bile salt hydrolase activity influences gene expression profiles and gastrointestinal maturation in infant mice.

The mechanisms by which early microbial colonizers of the neonate influence gut development are poorly understood. Bacterial bile salt hydrolase (BSH) acts as a putative colonization factor that influences bile acid signatures and microbe-host signaling pathways and we considered whether this activity can influence infant gut development. In silico analysis of the human neonatal gut metagenome confirmed that BSH enzyme sequences are present as early as one day postpartum. Gastrointestinal delivery of cloned BSH to immature gnotobiotic mice accelerated shortening of the colon and regularized gene expression profiles, with monocolonised mice more closely resembling conventionally raised animals. In situ expression of BSH decreased markers of cell proliferation (Ki67, Hes2 and Ascl2) and strongly increased expression of ALPI, a marker of cell differentiation and barrier function. These data suggest an evolutionary paradigm whereby microbial BSH activity potentially influences bacterial colonization and in-turn benefits host gastrointestinal maturation.

New therapeutic potential of microRNA treatment to target vulnerable atherosclerotic lesions and plaque rupture.

PURPOSE OF REVIEW: Atherosclerotic lesion vulnerability leading to plaque rupture is a major cause of morbidity in western society. Although several recent major trials have identified statins and angiotensin-converting enzyme inhibitors as having a pleiotropic benefit, no current therapeutic regime directly targets atherosclerosis. The emerging functions of microRNAs (miRs) in regulating gene expression have opened diverse possibilities in understanding plaque biology and in offering new therapeutic strategies. In this review, we consider vascular endothelial cells, smooth muscle cells and monocytes as the main cellular participants in vessel homeostasis during atherosclerosis evolution and discuss how they are functionally modified by miRs and how these modifications may allow therapeutic targeting. RECENT FINDINGS: Emerging roles for miRs in the pro-inflammatory functions of monocytes and macrophages, and proangiogenic functions of endothelial cells, suggest that miRs regulating these processes are potential targets. Conversely, the contribution of smooth muscle cells to plaque integrity may be augmented by miR-based agents. Recent investigations have uncovered key roles for miRs in each of these areas, which may be targeted through either silencing of proatherogenic or augmentation of antiatherogenic pathways. SUMMARY: With emerging miR-based therapeutics, a new paradigm for therapeutic intervention with the ultimate goal of plaque stabilization may exist.

Bone marrow-derived CX3CR1 progenitors contribute to neointimal smooth muscle cells via fractalkine CX3CR1 interaction.

Smooth muscle cells play a major role in numerous vascular diseases that contribute to remodeling, repair after injury, and arteriogenesis, and the source of these cells is thought to lie within the vessel wall and the circulating blood. Currently, the precise origin and mechanism of differentiation of extravascular smooth muscle progenitor cells (SPCs) is unclear. We show here that the CX(3)CR1 mononuclear cell population of murine bone marrow provides a source of SPCs that contributes to smooth muscle cells within the neointimal plaque after vascular injury. Moreover, CX(3)CR1-fractalkine (FKN) interaction in vivo is essential for smooth muscle cell differentiation of bone marrow-derived progenitor cells at the vessel wall level. Functional competence of bone marrow-derived CX(3)CR1 positive cells to interact with FKN is also crucial in part for neointima formation following vascular injury. Finally, in a pure preparation of bone marrow-derived CX(3)CR1 positive cells, we show that in vitro smooth muscle cell differentiation increases markedly in the presence of FKN. Our data highlight a novel functional relationship between the myeloid and vascular systems and in the context of vascular injury and repair underscores a key chemokine-receptor pathway that may regulate cell fate when smooth muscle cell differentiation is required.

Clinical potential of adult vascular progenitor cells.

Cell therapy to treat vascular and cardiovascular diseases has evolved over the past decade with improved understanding of progenitor cell mobilization, recruitment, and differentiation. The beneficial effects seen in several preclinical studies have prompted translation of adult vascular progenitor therapy to clinical trials. To date, progenitor cells isolated from bone marrow and peripheral blood have been tested in the context of acute myocardial infarction and chronic ischemic cardiomyopathy, with moderate benefit. This therapeutic effect occurs despite a relatively small number of injected progenitor cells and short-term residence in the target zone. Thus, indirect benefits, such as paracrine factors released from these cells, have been suggested as significant contributors to therapeutic efficacy. Several additional vascular progenitors of endothelial, smooth muscle, mesenchymal, and cardiac origin have been identified that may contribute to vasculogenesis. Indeed, a unifying paradigm for the most effective cell therapy strategies to date appears to be robust support of angiogenesis. Here we discuss a number of progenitor cells that currently show potential as cardiovascular therapeutics, either singly or in combination. We look at emerging cell types and disease targets that may be exploited for therapeutic benefit and future strategies that may maximize clinical efficacy.

A specific subset of mouse bone marrow cells has smooth muscle cell differentiation capacity-brief report.

OBJECTIVE: To determine whether CX(3)CR1(+) bone marrow cells have the capacity for smooth muscle cell (SMC) differentiation. METHODS AND RESULTS: CX(3)CR1(+) and CX(3)CR1(-) cells were isolated from marrow of CX(3)CR1 transgenic mice and cultured in SMC differentiation media. Phenotypic and functional analyses showed only CX(3)CR1(+) bone marrow cells exhibit colony cell outgrowth with SMC-specific protein expression, calcium signaling, and contraction responses similar to mature SMC. CONCLUSIONS: CX(3)CR1 marks a bone marrow cells population that enriches for progenitors with capacity to differentiate in vitro into SMC-like cells.

A state-of-the-art review of the current role of cardioprotective techniques in cardiac transplantation.

OBJECTIVES: The use of 'extended criteria' donor hearts and reconditioned hearts from donation after circulatory death has corresponded with an increase in primary graft dysfunction, with ischaemia-reperfusion injury being a major contributing factor in its pathogenesis. Limiting ischaemia-reperfusion injury through optimising donor heart preservation may significantly improve outcomes. We sought to review the literature to evaluate the evidence for this. METHODS: A review of the published literature was performed to assess the potential impact of organ preservation optimisation on cardiac transplantation outcomes. RESULTS: Ischaemia-reperfusion injury is a major factor in myocardial injury during transplantation with multiple potential therapeutic targets. Innate survival pathways have been identified, which can be mimicked with pharmacological conditioning. Although incompletely understood, discoveries in this domain have yielded extremely encouraging results with one of the most exciting prospects being the synergistic effect of selected agents. Ex situ heart perfusion is an additional promising adjunct. CONCLUSIONS: Cardiac transplantation presents a unique opportunity to perfuse the whole heart before, or immediately after, the onset of ischaemia, thus maximising the potential for global cardioprotection while limiting possible systemic side effects. While clinical translation in the setting of myocardial infarction has often been disappointing, cardiac transplantation may afford the opportunity for cardioprotection to finally deliver on its preclinical promise.