Abstract 272: Epigenetic Regulation Involved in Diabetes-induced Impairment in Myocardial Reparative Function of Endothelial Progenitor Cell-derived Exosomes

Myocardial infarction (MI) occurs frequently in patients with diabetes resulting in higher mortality and morbidity than non-diabetic patients. We and others have shown that bone marrow-derived endothelial progenitor cells (EPCs) promote cardiac neovascularization and attenuate ischemic injury in animal models. Moreover, emerging evidence supports that exosomes (Exo) mediate stem cell therapy by carrying cell-specific biological signatures and by inducing signaling via transfer of bioactive molecules to target cells. However, autologous cell-based therapies yielded modest clinical results, suggesting that cellular/Exo reparative function may be compromised on a background of disease such as diabetes. In addition, recent studies suggest epigenetic mechanisms, such as histone methylation for gene silencing, promotes diabetes-induced vascular complication. Therefore, we hypothesized that diabetic EPCs produce exosomes of altered and dysfunctional content which compromise EPC reparative function in ischemic heart disease via epigenetic alterations. We collected EPC-Exo from non-diabetic mice (Lepr db/+ ) and diabetic mice (Lepr db/db ) and examined their effect on tube formation and cardiomyocyte/endothelial cell survival in vitro as well as their reparative effects on permanent and acute ischemia/reperfusion (I/R) myocardial ischemic injuries in vivo . Diabetic EPC-Exo promoted neonatal rat cardiomyocyte cell apoptosis under hypoxic stress and repressed endothelial tube formation and cell survival compared to cells treated with WT EPC-Exo. In vivo studies revealed diabetic EPC-Exo significantly attenuated cardiac function, reduced capillary density, increased fibrosis and infarct size in permanent LAD ligation and I/R MI models. Mechanistically,H3K9Me3 was increased in mouse cardiac endothelial cells treated with diabetic EPC-exo, suggesting inhibition of angiogenic genes. Our results provide evidence that diabetic EPC-derived exosomes lose their cardiac reparative activities. Specific angiogenic genes will be examined by CHIP analysis of H3K9Me3. Reversing EPC-Exo function by manipulating H3K9Me3 expression will augment autologous therapies in regenerative medicine.

Abstract 513: Exosomes Derived From Podoplanin Positive Cells Induce Fibrosis and Inflammation in Healthy Mouse Heart

Superseding fibrosis is the leading cause of the adverse remodeling after myocardial infarction (MI); inflammation and paracrine signals enhance the fibrosis and ventricular dysfunction and inhibit the favorable repair. It has been reported that cells expressing Podoplanin (PDPN), a platelet aggregation- inducing type I transmembrane glycoprotein, appear around 2 days after MI as a signal of activation. We hypothesized that exosomes derived from these cells may actively affect the biology of fibrosis and inflammation. PDPN+ cells were isolated from hearts of mice 2 days after MI, expanded in a selective media and treated with TNFα, Angiotensin II or the combination of both. Exosomes derived from activated PDPN+ cells were isolated from the conditioned media and used in vitro for the treatment of mouse cardiac endothelial cells (mCECs), mouse embryonal fibroblast (MEF) and monocytes and in vivo for the treatment of healthy mouse hearts. Data from q-PCR showed that stimulated PDPN+ cells derived exosomes reprogramed mCECs to the endothelial lymphatic phenotype enhancing the expression of the major lymphatic lineage markers and upregulated the expression of fibrotic markers suggesting an endothelial-mesenchymal transition. Furthermore, stimulated PDPN+ cells derived exosomes drove the fibroblast to myo-fibroblast phenotype and activated monocytes toward pro-inflammatory lineage with an increased expression of TNFα and IL- 1β. In vivo, stimulated PDPN+ cells derived exosomes were initially injected in to the left ventricle of healthy mouse hearts followed with additional boosters delivered by retro-orbital vein injection. Treated mice developed an extended epicardial fibrosis with a subsequent impairment in the contractility and increase in the end diastolic and systolic volumes. In conclusion stimulated PDPN+ cells derived exosomes may impair the biology of mCECs, fibroblast and monocytes leading to adverse remodeling after MI.

Abstract 288: Circular RNA CircFNDC3b Modulates Cardiac Repair After Myocardial Infarction via FUS-1/VEGF-A Axis

Circular RNA (circRNA) is a new addition to the list of growing body of non-coding RNAs.Recent studies highlighted that circRNA are dysregulated in cardiovascular disease. However,knowledge of the role of circRNAs in ischemic cardiac injury is limited. Using global circRNAexpression profiling, we identified several circRNA transcripts that were differentially regulatedpost-MI in mice, including circFNDC3b (derived from 2 and 3 exons of cognate FNDC3b gene)which is significantly down regulated. Cell fractionation experiments revealed that circFNDC3bis highly enriched in endothelial cells of post-MI mice. Notably, we found a circFNDC3b orthologin humans, which was also significantly down regulated in ischemic cardiomyopathy patients.Further, gene profile analysis of circFNDC3b overexpression in cardiac endothelial cellsdemonstrated an increase in angiogenic genes. Among them, vascular endothelial growthfactor-A (VEGF-A) was significantly elevated concomitant with reduced in vitro apoptosis ofcardiomyoblasts and endothelial cells, which also exhibited enhanced tube formation. Forcardiac overexpression of circFNDC3b, we generated AAV9 viral particles and found that in vivoover expression attenuated LV dysfunction post-MI and enhanced neovascularization.Mechanistically, circFNDC3b interacts with its potential target RNA binding protein FUS-1 (fusedin sarcoma) and regulate VEGF signaling, thereby reducing cardiomyocyte apoptosis andenhancing neovascularization and cardiac function post-MI. These results indicatethat circFNDC3b is a novel potential target to prevent cardiac remodeling and highlight theimportance of circRNAs in cardiovascular diseases.

Abstract 333: TNF Receptor Modulation of Progenitor Cells and Exosomes for Myocardial Repair

Our published studies, using TNFR1 and TNFR2 knockout (KO) mice have demonstrated that negative effects of TNF during ischemic tissue repair including enhanced apoptosis and inflammatory cytokines expression and signaling, is largely mediated by TNFR1/p55. Our hypothesis is that inhibition of TNF-TNFR1 signaling inhibits multiple negative effects of TNF after myocardial ischemia by promoting TNF signaling through protective TNFR2 receptor and thereby augmenting EPC-mediated myocardial angiogenesis and repair and this enhanced protective effect of TNFR1 KO EPCs may involve alteration in the cargo and function of TNFR1-KO EPC derived exosomes.

Protective effect of disrupted TNF-TNFR1/p55 signaling in BM-EPCs under stress conditions in WT, p55KO and p75KO EPCs were tested in tube formation assay under hypoxia conditions and H2O2 treatment. In the absence of TNFR1 (p55KO EPCs) - EC function of BM-EPCs is enhanced under normoxia/hypoxia conditions and survival of BM-EPCs is increased under oxidative stress. To test the effect of TNFR1 and TNFR2 loss in the BM-EPCs for recovery after AMI, WT mice were subjected to AMI and WT, p75KO and p55KO BM-EPCs were injected into the myocardium immediately after AMI. Compared to WT and p75KO, injection of p55KO EPCs into WT hosts led to - increased retention of p55KO EPCs in the WT mice hearts; decreased post-MI apoptosis in WT mice; increased vascular network; significantly improved cardiac function; substantially small infarct size; the last three indicating improved cardiac remodeling by day 21 post-AMI. Further, in vitro exosome studies showed that compared to WT and p75KOs, p55KO BM-EPCs-derived exosomes showed positive activities in vitro, including - enhanced angiogenic function in HUVECs and increased survival of H9C2 cells. These effects were mediated via upregulation of miRNA-191-5p as shown by increased levels of angiogenic miR-191-5p in the exosomal cargo of p55KO EPCs and near complete inhibition of HUVEC angiogenic function in vitro by miR-191-5p-antagomiR.

Our findings suggest that decrease/loss of TNFR1 modulates both the content and function of EPC exosomes and enhance reparative and angiogenic capabilities of EPCs and EPC-mediated vascular and anatomical repair in the MI model.

Abstract 216: Interleukin-10 Deficiency Impairs Reparative Properties of Bone Marrow-Derived Endothelial Progenitor Cell Exosomes

EPC based therapy in clinical trials is largely benefited from paracrine effect such as exosomes. Exosomes mirror the behavior of parental cells and their function is dependent on RNAs and proteins packed inside. Systemic inflammation in MI patients greatly compromise the reparative performance of EPCs and relative exosomes. We hypothesized that EPCs under inflammatory stress produce dysfunctional exosomes with altered content, which compromise EPCs reparative benefit in ischemic heart disease. We choose interleukin-10 knockout (IL-10KO) mice as a model mimicking systemic inflammation. After EPC isolation and expansion from IL-10KO and wild-type (WT) mice, we isolated exosomes and compared their reparative properties both in vitro and in vivo . Our in vitro studies showed WT-EPC-Exo treatment enhanced endothelial cell proliferation and tube formation, and inhibited apoptosis, whereas IL-10KO-Exo exhibited impaired or even detrimental effects. We used MI mouse model to compare the in vivo function of two groups of exosomes, we found WT-EPC-Exo treatment significantly improved left ventricle cardiac function, inhibited cell death and promoted angiogenesis; while these benefits were lost in IL-10KO-EPC-Exo treated group. Both in vitro and in vivo studies suggested impaired exosome function under IL-10 deficiency. We checked the alteration of exosomal content using NGS RNAseq and mass spectrometry and found the RNA and protein expression pattern is drastically different in two groups of exosomes. Importantly, IL-10KO-EPC-Exo were highly enriched in microRNAs and proteins that promote inflammation and apoptosis and inhibit angiogenesis. We picked two candidates for further study, mir-375 and integrin linked kinase (ilk), both are highly enriched in IL-10KO-EPC-Exo. Through modulating the expression of mir-375 and ilk in exosomes, we partially rescued IL-10KO-EPC-Exo dysfunction. Thus, our study revealed that even the same type of cells, under different conditions, secrete exosomes with different function. The differences in exosomal function is caused by alteration in exosomal content, and the function can be enhanced or rescued by modulating specific targets in exosomes.

Abstract 298: Circular Rna Mmu_circ_008396 Attenuates Cardiac Remodeling After Myocardial Infarction in Mice

Recent studies highlighted that circular RNAs (circRNA) can play an important role in cardiac hypertrophy. However, the circRNAs in cardiac diseases is still limited. Using global circRNA expression profiling, we identified several circRNA transcripts that were differentially regulated post-MI in mice, including mmu_circ_008396 that is significantly down regulated. Cell fractionation experiments indicated that mmu_circ_008396 is highly enriched in endothelial cells in post-MI mice. Interestingly, we found a mmu_circ_008396 circRNA ortholog in humans, which was also significantly down regulated in ischemic cardiomyopathy patients. Further, overexpression of mmu_circ_008396 significantly enhanced tube formation and reduced apoptosis of human umbilical vein endothelial cells. For cardiac overexpression of mmu_circ_008396 circRNA, we created AAV9 viral particles and found that in vivo over expression attenuated LV dysfunction post-MI and enhanced neovascularization. Mechanistically, mmu_circ_008396 binds to its potential target miRNAs (mmu-miR-93-3p, mmu-miR-412-3p and mmu-miR-298-5p) and regulate hemeoxygenase-1/ VEGF signaling, thereby enhancing neovascularization and cardiac repair post-MI. These results indicate that mmu_circ_008396 circRNA might be a novel potential target to prevent cardiac remodeling and also highlight the significance of circRNAs in cardiovascular diseases.

Abstract 413: Podoplanin Neutralization Improves Cardiac Remodeling and Function After Acute Myocardial Infarction

Variety of cardioprotective and reparative therapeutic approaches have emerged for the treatment of cardiac remodeling after myocardial infarction (MI). Here we propose a novel mechanism using a neutralizing antibody that target Podoplanin (PDPN), a platelet aggregation-inducing type I transmembrane glycoprotein, expressed on a cohort of myocardial cells that migrate to the infarcted area after MI and contribute significantly to scar formation. The PDPN+ cells were isolated from infarcted hearts two days after MI, using magnetic beads sorting. We tested in vitro the effect of PDPN neutralizing antibody (5μg/ml) in a transwell migration assay and the activation of monocytes co-cultured with PDPN+ cells. The neutralizing antibody decreased significantly PDPN+ cells migration. Monocytes co-cultured with PDPN+ cells produced high levels of IL1α and IL12, whereas treatment of co-cultures with podoplanin neutralizing antibody inhibited IL1α and IL12 production and increased IL9 and IL10 production, suggesting a switch form pro-inflammatory to anti-inlammatory phenotype. To tests the effect of podoplanin neutralizing antibody in vivo, C57BL/6 wild type mice were subjected to experimental MI and anti-PDPN antibody (25μg/ml) was injected i.p. on days 1, 2, 7 and 15 after MI and mice were scarified two months after. At 7 days after MI echocardiography revealed comparable ~30% of ejection fraction (EF) in control and antibody-injected mice. After one month EF% remained unchanged in control group and increased up to 45% in antibody-treated group, suggesting improvement in cardiac function. Histologically, in the control group the ischemic area was composed by fibrotic tissue highly positive for fibronectin and αSMA, whereas in the antibody-treated group revealed large number of survived, as well as proliferating myocytes expressing αSARC-actin and Phospho-H3. Further, there was a significant increase in CD31 positive cells in the infarct border-zone of antibody-treated vs. control hearts, suggesting increased angiogenesis. Our findings suggest that inhibition of PDPN during first two weeks after MI intensely enhances cardiac regeneration and angiogenesis. This may represent a new therapeutic support for the tissue renewal after MI.

Abstract 37: Interleukin-10 Deficiency Can Alter Contents and Further Impair Functions of Exosomes Derived From Endothelial Progenitor Cells

Endothelial progenitor cell (EPC) based therapy has been shown to have an immense potential to promote cardiac neovascularization and to attenuate ischemic injury. Recent research revealed that the therapeutic performance of stem cells is largely due to paracrine effects, in which exosomes (Exo) play an essential role. However, the autologous transplantation of EPCs in patients with systemic inflammation, which is a common symptom in patients with ischemic heart diseases, yield modest results, suggesting the compromised cell function and altered Exo performance. So we hypothesized that EPCs under inflammatory stress might change Exo contents, which eventually compromises their repair ability in ischemic heart disease. Whether modulation of identified targets like specific microRNAs in Exo cargo can rescue and/or enhance their reparative properties of dysfunctional Exo is not known. We have previously shown in IL-10 KO mice (model mimicking systemic inflammation) that loss of Interleukin-10 (IL-10) impairs EPCs functions via miR-375. After cell expansion, we isolated Exo from these two groups and compared their functions in terms of cell survival, proliferation, migration and angiogenic capacity in vitro . Our studies revealed that WT-EPC-Exo treatment enhanced endothelial cells proliferation and tube formation and inhibited apoptosis; whereas IL-10 KO-Exo exhibited opposite effects, suggesting that reparative capacity of WT-EPC Exo is lost in Exo derived from IL-10-KO-EPCs. The deep sequencing and proteomic analysis between WT and IL-10KO-Exo revealed drastically altered Exosomal cargo. Importantly, IL-10KO-EPC-Exos were highly enriched in microRNAs and proteins related to pro-inflammation, cell apoptosis and anti-angiogenesis. Through modulation of specific target (here as miR-375), we partially rescued IL-10KO-EPC-Exo dysfunction. Taken together, our study revealed that Exo display impaired function under inflammatory stimulus via changing Exo contents, and the dysfunction can be rescued by modulation specific target packed in Exo.

Abstract 294: Therapeutic Silencing of miR-375 Attenuates Post-MI Inflammatory Response and Left Ventricular Dysfunction in Mice With Myocardial Infarction

MicroRNAs are known to be dysregulated in the ischemic heart disease and have emerged as potential therapeutic targets for treatment of myocardial infarction (MI). Our preliminary data indicated elevated MicroRNA-375 levels in failing human heart tissue. Therefore, we assessed whether inhibition of the miR-375 using a s.c.-delivered locked nucleic acid (LNA)-modified anti-miR (LNA-antimiR-375) can provide therapeutic benefit in mice with myocardial infarction (MI). After the induction of acute myocardial infarction, mice were treated with either control or LNA based LNA-anti-miR-375, and inflammatory response, cardiomyocyte apoptosis, capillary density and LV functional and structural remodeling changes were evaluated. LNA-anti-miR-375 therapy significantly reduced inflammatory cell infiltration, expression of pro-inflammatory cytokines and cardiomyocyte apoptosis in the myocardium. Further, our cell sorting experiments revealed that within the myocardium, LNA-anti-miR-375 was taken up by cardiomyocytes, endothelial cells and macrophages and repressed miR-375 levels, thereby activating 3-phosphoinositide-dependent protein kinase 1 (PDK-1) and downstream AKT phosphorylation on Thr-308. LNA anti-miR-375 therapy significantly improved LV functions, enhanced neovascularization and reduced infarct size. Corroborating with our in vivo findings, our in vitro studies demonstrated that knock down of miR-375 in macrophages enhanced the expression of PDK-1 and revealed reduced pro-inflammatory cytokines expression following LPS challenge. Taken together, our studies demonstrate that anti miR-375 therapy reduced inflammatory response, cardiomyocyte death, improved LV function and enhanced angiogenesis by targeting multiple cell types via activation of PDK-1/AKT signaling.

Abstract 220: Epigenetic Reprogramming Rescues Diabetic Endothelial Progenitor Cell Dysfunctions and Enhances Their Reparative Activities in Ischemic Tissue Repair

Type 2 Diabetes mellitus (DM) is the leading cause of death in the United States with concomitant complications from circulatory disorders including endothelial cell (EC)/endothelial progenitor cell (EPC) dysfunction in a variety of organs including heart. Although clinical trials of bone marrow progenitors/EPCs have shown some promise, however, diabetic dysfunction of EPC limits the functional benefits of stem/EPC-based cellular therapies. Emerging evidence suggests that epigenetic silencing of functional genes leads to dysfunctional EPCs in diabetes. In the present study, we show that epigenetic modulation of diabetic EPCs using small molecules epigenetic modifiers rescue diabetes-induced EPC dysfunction. EPCs from diabetic (db/db) mice were treated with valproic acid (VPA, histone deacetylase inhibitor) and 5’-azacytidine (5’-Aza; DNA methyltransferase, DNMT, inhibitor), and their function was determined both in vitro and in vivo. In contrast to untreated EPCs, treatment with VPA/5’-Aza, enhanced their angiogenic activities including tube formation, survival and proliferation. Expression of multiple pro-angiogenic genes including eNOS, and VEGF/VEGFR2 was upregulated in reprogrammed EPCs and chromatin immunoprecipitation experiments confirmed enhanced histone3-lysine9 acetylation (H3K9ac) of these gene promoters. Reprogrammed EPCs displayed reduced protein expression of DNMT3a and DNMT3b; whereas expression of histone H3K9ac and H3K14ac (gene activating epigenetic mark) was up-regulated. In db/db mouse hind limb ischemia model, transplantation of reprogrammed EPCs restored blood flow, enhanced capillary density and muscle architecture and resulted in significant limb salvage. In a myocardial ischemia model in db/db mice, transplantation of reprogrammed EPCs enhanced left ventricular functions, reduced infarct size and increased capillary density in the border zone. Taken together our data suggests that the reprogramming of db/db-derived EPCs might result in pattern shift of epigenetic modifications, leading to up-regulation of functional genes repressed by hyperglycemia and may rescue dysfunctional EC/EPC phenotype leading to improved functional repair capacity of diabetic stem cells/EPCs.

Abstract 99: IL10-inhibits Fibroblast Progenitor Cell-mediated Cardiac Fibrosis in Pressure-overloaded Myocardium

Background: Activated fibroblasts (myoFBs) play critical role in cardiac fibrosis, however, their origin in diseased heart remains uncertain. Recent studies suggest the contribution of bone marrow fibroblasts progenitor cells (BM-FPC) in pressure overload (PO)-induced cardiac fibrosis. Previously we have shown that interleukin-10 suppress PO-induced cardiac fibrosis, however, its role on inhibition of BM-FPC-mediated fibrosis is not known. Thus, we hypothesized that IL-10 inhibits PO-induced homing and transition of BM-FPC to myoFBs and therefore, attenuates cardiac fibrosis.

Methods and Results: Cardiac fibrosis was induced in Wild-type (WT) and IL-10-knockout (KO) mice by transverse aortic constriction (TAC). TAC-induced left ventricular (LV) dysfunction and fibrosis were further exaggerated in KO mice. Systemic recombinant IL-10 administration markedly improved LV function and inhibited PO-induced cardiac fibrosis. PO-enhanced FPC (Prominin1 + cells) mobilization and homing in IL-10 KO mice compared to WT mice. Furthermore, bone marrow transplantation (BMT) experiment was performed wherein WT marrow from GFP mice was repopulated in IL-10 KO mice. FPC mobilization was significantly reduced in BMT-IL10 KO mice compared to IL-10 KO mice after TAC. Furthermore, immunofluorescence result in BMT mice showed that subsets of myoFBs are derived from BM after TAC. To identify the molecular mechanism, wild type BM-FPC were treated with TGFβ 2 with or without IL10. IL10 treatment significantly inhibits TGFβ 2 -induced FPC to myoFBs transition. As miRNAs are key players in cardiac fibrosis, next we performed fibrosis-associated miRNA profiling using miRNA array kit. TGFβ 2 -induced miR-208, 155, 21 and 145 expression was markedly inhibited by IL-10.

Conclusion: Taken together, our findings suggest that both reduced homing to heart and transition of FPC to myofibroblasts mediate anti-fibrotic effect of IL10 during PO-induced heart failure. Ongoing investigations using molecular approaches will provide a better understanding on the mechanistic and therapeutic aspects of IL10 on PO-induced cardiac fibrosis and heart failure.

Abstract 40: Interleukin-10 Deficiency Impairs Reparative Properties of Bone Marrow-derived Endothelial Progenitor Cell Exosomes Function in Ischemic Myocardium

Endothelial progenitor cell (EPC) based therapy promotes neovascularization in ischemic myocardium. Studies suggest that therapeutic effect of stem cells is largely due to paracrine mechanisms including stem cell-derived exosomes that are emerging as key paracrine mediators of stem cell functions. However, the autologous transplantation of EPCs in patients with systemic inflammation, which is a common symptom in patients with ischemic heart diseases, yield modest results suggesting the compromised cell function and altered exosome performance. We hypothesized that EPCs under inflammatory stress secrete dysfunctional exosomes with altered contents including packaged microRNAs, which eventually compromises exosomes repair ability in ischemic myocardium. Whether modulation of identified targets like specific microRNAs in the cargo of exosomes can rescue and/or enhance their reparative properties of dysfunctional exosomes is not known. We have previously shown in Interleukin-10 (IL-10) KO mice (model mimicking systemic inflammation) that loss of IL-10 impairs EPCs functions via miR-375. After cell expansion, we isolated exosomes from these two groups and compared their functions in terms of cell survival, proliferation, migration and angiogenic capacity in vitro and in vivo . We report that WT-EPC-exosomes (Exo) transplantation in the ischemic myocardium after MI significantly improved post-infarct repair, neovascularization and left ventricle functions. Our in vitro studies revealed that WT-EPC-Exo treatment enhanced endothelial cells proliferation and tube formation and inhibited apoptosis; whereas IL-10 KO-EPC-Exo exhibited opposite effects, suggesting that reparative capacity of WT-EPC-Exo is lost in exosomes derived from IL-10 KO-EPCs. Exosome miRNA profiling revealed a drastically different expression patterns with enrichment of inflammation induced microRNAs including significantly higher expression of miR-375. Interestingly, Knockdown of miR-375 in IL-10-EPCs decreased the expression level of miR-375 in their exosomes and partly rescued their angiogenic dysfunctions. Taken together, our studies suggest that modulation of miR-375 in IL-10 KO-EPC-Exo can rescue its phenotype and promote cardiac repair.

Abstract 255: Hur/ppar-gamma Mediates Posttranscriptional Regulation of Hyperglycemia-induced Pro-inflammatory Response

Metabolic disorders including diabetes and obesity are associated with persistent activation of the innate immune response, which leads to low-grade inflammation and increased cardiovascular risk. The RNA-binding protein HuR binds to and post-transcriptionally regulates inflammatory cytokines, mRNA stability and gene expression, although it’s exact role in the diabetic condition remains unclear. Bone marrow-derived macrophages (BMM) exposed to high glucose (HG, 25mM D-glucose) displayed elevated expression of HuR and reduced expression of nuclear receptor peroxisome proliferator-activated receptor-gamma (PPAR-gamma) as compared to low glucose (LG, 5mM D-glucose)-treated cells. The increase in HuR expression was associated with an increase in the gene expression of various inflammatory cytokines including TNF-alpha, MCP-1, IL-1beta and IL-6. At the molecular level, macrophages activated with LPS showed enhancements in expression of inflammatory mRNAs and also promoted their stability. Conversely, knockdown of HuR induced post-transcriptional silencing, reduced the mRNA stability and expression of inflammatory cytokines. Macrophages treated with selective antagonists of the nuclear receptor peroxisome proliferator-activated receptor-gamma (PPAR-gamma), GW9662 displayed increases in HuR expression and of various inflammatory cytokines. In an in vivo model of myocardial infarction, mice receiving intramyocardial injection of HuR-specific shRNA displayed a reduced inflammatory cytokine profile in the myocardium as compared to control shRNA treated mice. Taken together, these data highlight the role of HuR as a homeostatic coordinator of cytokine mRNA that regulates innate inflammatory effects and demonstrates the potential of modulating the effects of HuR for clinical benefit against pathologic inflammation in diabetes/obesity.

Abstract 408: Myocardial Knockdown of Mir-375 Attenuates Post-mi Inflammatory Response and Left Ventricular Dysfunction via Pdk-1-akt Signaling Axis

MicroRNAs are known to be dysregulated in the ischemic heart disease and have emerged as potential therapeutic targets for treatment of myocardial infarction (MI). Recently MicroRNA-375 has been shown to be up-regulated in humans with MI. In this study, we assessed whether inhibition of the miR-375 using an i.v.-delivered locked nucleic acid (LNA)-modified anti-miR (LNA-antimiR-375) can provide therapeutic benefit in mice with pre-existing pathological cardiac remodeling and dysfunction due to myocardial infarction (MI).After the induction of acute myocardial infarction, mice were treated with either control or LNA based miR-375 inhibitor, and inflammatory response, cardiomyocyte apoptosis and LV functional and structural remodeling changes were evaluated. Anti-miR-375 therapy significantly suppressed infiltration of inflammatory cells, expression of proinflammatory cytokines in the myocardium and cardiomyocyte apoptosis. These changes were associated with miR-375 mediated activation of 3-phosphoinositide-dependent protein kinase 1 (PDK-1) and downstream AKT phosphorylation on Thr-308. LNA anti-miR-375 therapy significantly improved LV functions, reduced infarct size, and attenuated infarct wall thinning. Moreover, LNA based miR-375 therapy significantly increased capillary density in the infarcted myocardium. Further, our in vitro studies demonstrated that miR-375 negatively regulates the expression of PDK-1 by directly targeting the 3’UTR of the PDK-1 transcript. Taken together, our studies demonstrate that anti miR-375 therapy suppresses inflammatory response, cardiomyocyte death and contributes to improved LV function and enhanced angiogenesis via activation of PDK-1/AKT signaling.

Abstract 106: Pluripotent Stem Cell Microrna-294 Induces Cardiomyocyte Proliferation and Augments Cardiac Function After Myocardial Infarction

Rationale: Embryonic heart is characteristic of rapidly dividing cardiomyocytes that give rise to sufficient numbers required to build a working myocardium. In contrast, cardiomyocytes retain some proliferative capacity in the neonates but lose most of it in adulthood. Embryonic stem cell cycle (ESCC) miRs are a class of microRNAs regulating the unique cell cycle of ESCs and their characteristic pluripotency. Nevertheless, expression of miR-294, a member of the ESCC miRs is lost during developmental transitions from the ESCs to mature cells. Effect of miR-294 to induce cardiac proliferation and heart function has not been previously studied.

Objective: To determine whether miR-294 drives cardiomyocyte cell cycle reentry leading to augmentation of cardiac function after myocardial infarction.

Methods and Results: miR expression analysis in the heart during development revealed elevated levels of miR-294 in the prenatal stages while the expression was lost in the neonates and adults as confirmed by qRT-PCR. Neonatal ventricular cardiomyocytes (NRVMs) were treated with miR-294 mimic to determine the effect on proliferation and cell cycle. Elevated mRNA levels of cyclins A2, E1, CDK2 together with c-myc, E2F1 and E2F3 was observed in NRVMs treated with 25nM mimic for miR-294. Additionally, miR-294 treated NRVMs showed in AKT phosphorylation along with enhanced protein levels of cyclin D1 and E2F1. Increased expression of p-histone 3, Ki67 and Aurora B kinase (G2/M) was confirmed by immunocytochemistry in NRVMs after miR-294 treatment compared to control cells. Administration of miR-294 in mice subjected to myocardial infarction demonstrated augmentation of cardiac function in mice receiving miR-294 8 weeks after injury. Increase myocyte proliferation was observed in the heart after miR-294 treatment as analyzed by BrdU uptake, p-Histone 3 and Aurora B expression by immunostaining. Concurrently, a decrease in infarct size along with decreased apoptosis was observed in the miR-294 hearts compared to the control.

Conclusion: Ectopic expression of miR-294 recapitulates embryonic signaling and enhances cardiomyocyte ability to proliferate and reenter the cell cycle leading to augmented cardiac function in mice after myocardial infarction.

Abstract 321: Macrophage Elavl1 Regulates Fibrogenesis Through Post-transcriptional Mechanism Under Diabetic Conditions

Patients with diabetes are predisposed to increased risk of cardiovascular diseases. Persistent interaction of infiltrating macrophages and resident fibroblasts play a critical role in cardiac fibrosis. However, the signaling mechanism is not clear. We hypothesized that macrophage ELAV1 (mRNA stabilizing protein) modulates profibrotic mediators and extracellular matrix turnover by binding to 3′UTR and regulating the mRNA stability of TGF-beta and MMP-9 in hyperglycemic conditions. Mice receiving intramyocardial injection of HuR-specific shRNA showed significant reduction in infarct size and fibrosis area. Reduced fibrosis was associated with decrease in TGF-beta and MMP-9 expression in the myocardium. Conditioned media (CM) from high glucose (HG) treated macrophages significantly increased profibrogenic response (increased mRNA expression of Col1a1, Col3a1 and fibronectin) in fibroblast cell line as compared to fibroblasts incubated with CM from low glucose (LG)-treated macrophages. Knockdown of ELAV1 in HG-treated macrophages abrogated the profibrotic effects in fibroblasts. Indirect immunofluroscence of bone marrow-derived macrophages (BMM) demonstrated that HG increases nuclear ELAV1 export to the cytoplasm. Pharmacological inhibition of Protein kinase C-delta (PKCd) blocked HG-induced ELAV1 nuclear to cytoplasmic translocation. In vitro, stable knockdown of ELAV1 in mouse macrophage cell line RAW 264.7 reduced mRNA expression of TGF-beta and MMP-9 following LPS challenge, accompanied by a marked reduction in the mRNA stability of these genes. Our study here establishes an ELAV1/TGF-beta/MMP-9/PKC-delta signaling axis in the macrophages controlling the profibrogenic responses in fibroblasts, the major contributor in the pathogenesis of fibrosis. Therefore, targeting this signaling pathway might be of therapy value for cardiac fibrosis in diabetic patients.

Abstract 269: Sirt-6 Deficiency Impairs Wound Healing in Diabetic (db/db) Mice Through Enhancement of Nf-kb Dependent Transcriptional Activity

Delayed wound healing is one of the major complications in diabetes and is characterized by chronic proinflammatory response, and abnormalities in angiogenesis and collagen deposition. Sirtuin family proteins regulate numerous physiological processes, including those involved in promotion of longevity, DNA repair, glycolysis and inflammation. However the role of sirtuin 6 (SIRT6), a NAD+-dependent nuclear deacetylase, in wound healing specifically under diabetic condition remains unclear. To analyze the role of SIRT6 in cutaneous wound healing, paired 6 mm stented wound were created in diabetic db/db mice and injected siRNA against SIRT6 in the wound margins (transfection agent alone and non-sensed siRNA served as controls). Wound time to closure was assessed by digital planimetry, and wounds were harvested for histology, immunohistochemistry and western blotting. SIRT6-siRNA treated diabetic wound showed impaired healing, which was associated with reduced capillary density when compared to control treatment. Interestingly, SIRT6 deficiency decreased VEGF expression in the wounds. Furthermore, SIRT6 ablation in diabetic wound promotes NF-kB activation resulting in increased expression of proinflammatory marker and oxidative stress. Collectively, our findings demonstrate that loss of SIRT6 in cutaneous wounds promotes proinflammatory response by increasing NF-kB activation, oxidative stress and decrease in angiogenesis in the diabetic mice. Based on these findings, we speculate that activation of SIRT6 signaling might be a potential approach for promoting wound healing in diabetics.

Abstract 3: Il-10 Regulated Mir-375 Enhances Endothelial Progenitor Cell Mediated Myocardial Repair And Survival After Myocardial Infarction

We hypothesized that IL-10 regulates miR-375 signaling in EPCs to enhance their survival and function in ischemic myocardium after MI. miR-375 knock down EPC were transplanted intramyocardially after induction of MI. Mice receiving EPC treated with miR-375 inhibitor showed increased number of GFP+EPCs retention that was associated with reduced EPC apoptosis in the myocardium. The engraftment of EPC into the vascular structures and the associated capillary density was significantly higher in miR-375-treated mice. The above findings further correlated with reduced infarct size, fibrosis and enhanced LV function (echocardiography) in miR-375 knock down EPC group as compared to scrambled EPC. Our in vitro studies revealed that the knockdown of miR-375 enhanced EPC proliferation, migration; tube formation ability and inhibited cell apoptosis, while the up-regulation of miR-375 with the mimic had the opposite effects. In addition, we found that miR-375 negatively regulates the expression of 3-phosphoinositide-dependent protein kinase 1 (PDK1) by directly targeting the 3'UTR of the PDK1 transcript. Interestingly, EPC isolated from IL-10-deficient mice has elevated basal levels of miR-375 and exhibited poor proliferation and tube formation ability where as miR-375 knock down in EPC isolated from IL-10 deficient mice attenuated these effects. Furthermore, transplantation of miR-375 knock down IL-10 deficient EPC after MI resulted in attenuated cardiac functions compared to scramble IL-10 deficient EPCs. Taken together, our studies suggest that IL-10 regulated miR-375 enhances EPC survival and function, associated with efficient myocardial repair via activation of PDK-1/AKT signaling cascades.