Conrad P. Hodgkinson

Advanced Glycation End-Product of Low Density Lipoprotein Activates the Toll-Like 4 Receptor Pathway Implications for Diabetic Atherosclerosis

Objective—Diabetes is a major risk factor for coronary heart disease. Accumulation of advanced glycation end-products (AGEs) attributable to hyperglycemia in diabetics promotes the development of atherosclerosis. However, the underlying mechanisms remain unclear. Methods and Results—The advanced glycation end-product of low-density-lipoprotein (AGE-LDL) induced proinflammatory cytokine production in human coronary artery endothelial cells and human- and mouse-macrophages. AGE-LDL stimulated cytokine synthesis was markedly reduced in mouse macrophages with a TLR4 loss-of-function mutation. Coimmunoprecipitation experiments indicated AGE-LDL interacts with TLR4, RAGE, and CD36. Incubation of cultured macrophages with TLR4, RAGE, or CD36 antibodies inhibited AGE-LDL stimulation of tumor necrosis factor (TNF)&agr; production. A competitive binding inhibitor of TLR4 blocked AGE-LDL binding to the receptor. After transfection of a HEK293 cell system with wild-type TLR4, AGE-LDL activated a signaling pathway including p38&agr;, JNK, and ERK1 kinases and AP1, Elk1, and NF–&kgr;B transcription factors; the net result being increased cytokine production. These effects were absent when cells were transfected with empty plasmid. Two common polymorphisms in TLR4, D299G and T399I, reduced the response of TLR4 to lipopolysaccharide (LPS) but had no effect on AGE-LDL signaling. Conclusions—These results indicate that AGE-LDL activates a TLR4-mediated signaling pathway, thus inducing proinflammatory cytokine production. This mechanism may partly explain the increased risk of atherosclerosis observed in diabetics.

A Role of Matrix Metalloproteinase-8 in Atherosclerosis

Rationale: Atherosclerotic lesions express matrix metalloproteinase (MMP)8, which possesses proteolytic activity on matrix proteins particularly fibrillar collagens and on nonmatrix proteins such as angiotensin (Ang) I. Objective: We studied whether MMP8 plays a role in atherogenesis. Methods and Results: In atherosclerosis-prone apolipoprotein E–deficient mice, inactivating MMP8 resulted in a substantial reduction in atherosclerotic lesion formation. Immunohistochemical examinations showed that atherosclerotic lesions in MMP8-deficient mice had significantly fewer macrophages but increased collagen content. In line with results of in vitro assays showing that Ang I cleavage by MMP8 generated Ang II, MMP8 knockout mice had lower Ang II levels and lower blood pressure. In addition, we found that products of Ang I cleavage by MMP8 increased vascular cell adhesion molecule (VCAM)-1 expression and that MMP8-deficient mice had reduced VCAM-1 expression in atherosclerotic lesions. Intravital microscopy analysis showed that leukocyte rolling and adhesion on vascular endothelium was reduced in MMP8 knockout mice. Furthermore, we detected an association between MMP8 gene variation and extent of coronary atherosclerosis in patients with coronary artery disease. A relationship among MMP8 gene variation, plasma VCAM-1 level, and atherosclerosis progression was also observed in a population-based, prospective study. Conclusions: These results indicate that MMP8 is an important player in atherosclerosis.

Genetic Engineering of Mesenchymal Stem Cells and Its Application in Human Disease Therapy

The use of stem cells for tissue regeneration and repair is advancing both at the bench and bedside. Stem cells isolated from bone marrow are currently being tested for their therapeutic potential in a variety of clinical conditions including cardiovascular injury, kidney failure, cancer, and neurological and bone disorders. Despite the advantages, stem cell therapy is still limited by low survival, engraftment, and homing to damage area as well as inefficiencies in differentiating into fully functional tissues. Genetic engineering of mesenchymal stem cells is being explored as a means to circumvent some of these problems. This review presents the current understanding of the use of genetically engineered mesenchymal stem cells in human disease therapy with emphasis on genetic modifications aimed to improve survival, homing, angiogenesis, and heart function after myocardial infarction. Advancements in other disease areas are also discussed.

MicroRNA Induced Cardiac Reprogramming In Vivo Evidence for Mature Cardiac Myocytes and Improved Cardiac Function

Rationale: A major goal for the treatment of heart tissue damaged by cardiac injury is to develop strategies for restoring healthy heart muscle through the regeneration and repair of damaged myocardium. We recently demonstrated that administration of a specific combination of microRNAs (miR combo) into the infarcted myocardium leads to direct in vivo reprogramming of noncardiac myocytes to cardiac myocytes. However, the biological and functional consequences of such reprogramming are not yet known. Objective: The aim of this study was to determine whether noncardiac myocytes directly reprogrammed using miRNAs in vivo develop into mature functional cardiac myocytes in situ, and whether reprogramming leads to improvement of cardiac function. Methods and Results: We subjected fibroblast-specific protein 1-Cre mice/tandem dimer Tomato (tdTomato) mice to cardiac injury by permanent ligation of the left anterior descending coronary artery and injected lentiviruses encoding miR combo or a control nontargeting miRNA. miR combo significantly increased the number of reprogramming events in vivo. Five to 6 weeks after injury, morphological and physiological properties of tdTomato− and tdTomato+ cardiac myocyte–like cells were analyzed ex vivo. tdTomato+ cells expressed cardiac myocyte markers, sarcomeric organization, excitation–contraction coupling, and action potentials characteristic of mature ventricular cardiac myocytes (tdTomato− cells). Reprogramming was associated with improvement of cardiac function, as analyzed by serial echocardiography. There was a time delayed and progressive improvement in fractional shortening and other measures of ventricular function, indicating that miR combo promotes functional recovery of damaged myocardium. Conclusions: The findings from this study further validate the potential use of miRNA-mediated reprogramming as a therapeutic approach to promote cardiac regeneration after myocardial injury.Rationale: A major goal for the treatment of heart tissue damaged by cardiac injury is to develop strategies for restoring healthy heart muscle through the regeneration and repair of damaged myocardium. We recently demonstrated that administration of a specific combination of microRNAs (miR combo) into the infarcted myocardium leads to direct in vivo reprogramming of noncardiac myocytes to cardiac myocytes. However, the biological and functional consequences of such reprogramming are not yet known. Objective: The aim of this study was to determine whether noncardiac myocytes directly reprogrammed using miRNAs in vivo develop into mature functional cardiac myocytes in situ, and whether reprogramming leads to improvement of cardiac function. Methods and Results: We subjected fibroblast-specific protein 1-Cre mice/tandem dimer Tomato (tdTomato) mice to cardiac injury by permanent ligation of the left anterior descending coronary artery and injected lentiviruses encoding miR combo or a control nontargeting miRNA. miR combo significantly increased the number of reprogramming events in vivo. Five to 6 weeks after injury, morphological and physiological properties of tdTomato− and tdTomato+ cardiac myocyte–like cells were analyzed ex vivo. tdTomato+ cells expressed cardiac myocyte markers, sarcomeric organization, excitation–contraction coupling, and action potentials characteristic of mature ventricular cardiac myocytes (tdTomato− cells). Reprogramming was associated with improvement of cardiac function, as analyzed by serial echocardiography. There was a time delayed and progressive improvement in fractional shortening and other measures of ventricular function, indicating that miR combo promotes functional recovery of damaged myocardium. Conclusions: The findings from this study further validate the potential use of miRNA-mediated reprogramming as a therapeutic approach to promote cardiac regeneration after myocardial injury. # Novelty and Significance {#article-title-18}

Association of Matrix Metalloproteinase-8 Gene Variation with Breast Cancer Prognosis

Animal and cell studies indicate an inhibitory effect of matrix metalloproteinase-8 (MMP8) on tumorigenesis and metastasis. We investigated whether MMP8 gene variation was associated with breast cancer metastasis and prognosis in humans. We first studied nine tagging single nucleotide polymorphisms (SNP) in the MMP8 gene in 140 clinically and pathologically well-characterized breast cancer patients. Four of the SNPs were found to be associated with lymph node metastasis, the most pronounced being a promoter SNP (rs11225395) with its minor allele (T) associating with reduced susceptibility to lymph node metastasis (P = 0.02). This SNP was further evaluated for association with cancer relapse and survival among a cohort of approximately 1,100 breast cancer patients who had been followed for cancer recurrence and mortality for a median of 7.1 years. The T allele was associated with reduced cancer relapse and greater survival, particularly among patients with earlier stage cancer. Among patients of tumor-node-metastasis stage 0 to II, the adjusted hazard ratio of disease-free survival was 0.7 [95% confidence interval (95% CI), 0.5-0.9] for patients carrying T allele compared with those homozygous for the C allele (P = 0.02). In vitro experiments showed that the T allele had higher promoter activity than the C allele in breast cancer cells. Electrophoretic mobility shift assays showed binding of nuclear proteins to the DNA sequence at the SNP site of the T allele but not that of the C allele. The data suggest that MMP8 gene variation may influence breast cancer prognosis and support the notion that MMP8 has an inhibitory effect on cancer metastasis.

MicroRNA Induced Cardiac Reprogramming In Vivo

Rationale: A major goal for the treatment of heart tissue damaged by cardiac injury is to develop strategies for restoring healthy heart muscle through the regeneration and repair of damaged myocardium. We recently demonstrated that administration of a specific combination of microRNAs (miR combo) into the infarcted myocardium leads to direct in vivo reprogramming of noncardiac myocytes to cardiac myocytes. However, the biological and functional consequences of such reprogramming are not yet known. Objective: The aim of this study was to determine whether noncardiac myocytes directly reprogrammed using miRNAs in vivo develop into mature functional cardiac myocytes in situ, and whether reprogramming leads to improvement of cardiac function. Methods and Results: We subjected fibroblast-specific protein 1-Cre mice/tandem dimer Tomato (tdTomato) mice to cardiac injury by permanent ligation of the left anterior descending coronary artery and injected lentiviruses encoding miR combo or a control nontargeting miRNA. miR combo significantly increased the number of reprogramming events in vivo. Five to 6 weeks after injury, morphological and physiological properties of tdTomato− and tdTomato+ cardiac myocyte–like cells were analyzed ex vivo. tdTomato+ cells expressed cardiac myocyte markers, sarcomeric organization, excitation–contraction coupling, and action potentials characteristic of mature ventricular cardiac myocytes (tdTomato− cells). Reprogramming was associated with improvement of cardiac function, as analyzed by serial echocardiography. There was a time delayed and progressive improvement in fractional shortening and other measures of ventricular function, indicating that miR combo promotes functional recovery of damaged myocardium. Conclusions: The findings from this study further validate the potential use of miRNA-mediated reprogramming as a therapeutic approach to promote cardiac regeneration after myocardial injury.Rationale: A major goal for the treatment of heart tissue damaged by cardiac injury is to develop strategies for restoring healthy heart muscle through the regeneration and repair of damaged myocardium. We recently demonstrated that administration of a specific combination of microRNAs (miR combo) into the infarcted myocardium leads to direct in vivo reprogramming of noncardiac myocytes to cardiac myocytes. However, the biological and functional consequences of such reprogramming are not yet known. Objective: The aim of this study was to determine whether noncardiac myocytes directly reprogrammed using miRNAs in vivo develop into mature functional cardiac myocytes in situ, and whether reprogramming leads to improvement of cardiac function. Methods and Results: We subjected fibroblast-specific protein 1-Cre mice/tandem dimer Tomato (tdTomato) mice to cardiac injury by permanent ligation of the left anterior descending coronary artery and injected lentiviruses encoding miR combo or a control nontargeting miRNA. miR combo significantly increased the number of reprogramming events in vivo. Five to 6 weeks after injury, morphological and physiological properties of tdTomato− and tdTomato+ cardiac myocyte–like cells were analyzed ex vivo. tdTomato+ cells expressed cardiac myocyte markers, sarcomeric organization, excitation–contraction coupling, and action potentials characteristic of mature ventricular cardiac myocytes (tdTomato− cells). Reprogramming was associated with improvement of cardiac function, as analyzed by serial echocardiography. There was a time delayed and progressive improvement in fractional shortening and other measures of ventricular function, indicating that miR combo promotes functional recovery of damaged myocardium. Conclusions: The findings from this study further validate the potential use of miRNA-mediated reprogramming as a therapeutic approach to promote cardiac regeneration after myocardial injury. # Novelty and Significance {#article-title-18}

Microarray analysis of peroxisome proliferator-activated receptor γ-induced changes in gene expression in macrophages

We used a combination of expression microarray and Northern blot analyses to identify target genes for peroxisome proliferator-activated receptor (PPAR) gamma in RAW264.7 macrophages. PPARgamma natural ligand 15-deoxy-Delta(12,14) prostaglandin and synthetic ligands ciglitazone and rosiglitazone increased the expression of scavenger receptor CD36 and ATP-binding cassette transporter A1, as well as adipophilin (a lipid droplet coating protein involved in intracellular lipid storage and transport), calpain (a protease implicated in ABCA1 protein degradation), and ADAM8 (a disintegrin and metalloprotease protein involved in cell adhesion). These findings are relevant to understanding the effect of PPARgamma activation on gene expression and cognate pathways in macrophages.

Emerging Concepts in Paracrine Mechanisms in Regenerative Cardiovascular Medicine and Biology

In the past decade, substantial evidence supports the paradigm that stem cells exert their reparative and regenerative effects, in large part, through the release of biologically active molecules acting in a paracrine fashion on resident cells. The data suggest the existence of a tissue microenvironment where stem cell factors influence cell survival, inflammation, angiogenesis, repair, and regeneration in a temporal and spatial manner.

Functional Toll-like receptor 4 mutations modulate the response to fibrinogen

Fibrinogen has been implicated in atherosclerosis; in part by activating the lipopolysaccharide (LPS) receptor Toll-like receptor 4 (TLR4). The fibrinogen-TLR4 signalling pathway remains uncharacterised. In human macrophages fibrinogen stimulated interleukin (IL)6 expression and ERK (extracellular signal-related kinase) phosphorylation. In HEK293-CD14-MD2 cells expressing TLR4, fibrinogen induced robust phosphorylation of ERK1, p38alpha and JNK and activated transcription factors NFkappaB, Elk-1 and AP-1 (activator protein-1). The net effect of this signalling pathway was a pro-inflammatory response characterised by IL6 and TNFalpha synthesis and increased IL8, matrix metalloproteinase (MMP)1, MMP9, and MCP-1 promoter activity. Two common TLR4 mutations, D299G and T399I, render the receptor LPS hyporesponsive. The effect of fibrinogen on polymorphic variant TLR4s was markedly different; enhancing activation of kinases, transcription factors, cytokine synthesis and promoter activity. This study indicates that fibrinogen activates TLR4, explaining how fibrinogen promotes inflammatory protein expression.

Protein kinase-ζ interacts with munc18c: role in GLUT4 trafficking

Aims/hypothesisInsulin-stimulated glucose transport requires a signalling cascade through kinases protein kinase (PK) Cζ/λ and PKB that leads to movement of GLUT4 vesicles to the plasma membrane. The aim of this study was to identify missing links between the upstream insulin-regulated kinases and the GLUT4 vesicle trafficking system.Materials and methodsA yeast two-hybrid screen was conducted, using as bait full-length mouse munc18c, a protein known to be part of the GLUT4 vesicle trafficking machinery.ResultsThe yeast two-hybrid screen identified PKCζ as a novel interactor with munc18c. Glutathione S transferase (GST) pull-downs with GST-tagged munc18c constructs confirmed the interaction, mapped a key region of munc18c that binds PKCζ to residues 295–338 and showed that the N-terminal region of PKCζ was required for the interaction. Endogenous munc18c was shown to associate with endogenous PKCζ in vivo in various cell types. Importantly, insulin stimulation increased the association by approximately three-fold. Moreover, disruption of PKCζ binding to munc18c by deletion of residues 295–338 of munc18c or deletion of the N-terminal region of PKCζ markedly inhibited the ability of insulin to stimulate glucose uptake or GLUT4 translocation.Conclusions/interpretationWe have identified a physiological interaction between munc18c and PKCζ that is insulin-regulated. This establishes a link between a kinase (PKCζ) involved in the insulin signalling cascade and a known component of the GLUT4 vesicle trafficking pathway (munc18c). The results indicate that PKCζ regulates munc18c and suggest a model whereby insulin triggers the docking of PKCζ to munc18c, resulting in enhanced GLUT4 translocation to the plasma membrane.