Podoplanin Positive Cell-derived Extracellular Vesicles Contribute to Cardiac Amyloidosis After Myocardial Infarction.

Background: Amyloidosis is a major long-term complication of chronic disease; however, whether it represents one of the complications of post-myocardial infarction (MI) is yet to be fully understood. Methods: Using wild-type and knocked-out MI mouse models and characterizing in vitro the exosomal communication between bone marrow-derived macrophages and activated mesenchymal stromal cells (MSC) isolated after MI, we investigated the mechanism behind Serum Amyloid A 3 (SAA3) protein overproduction in injured hearts. Results: Here, we show that amyloidosis occurs after MI and that amyloid fibers are composed of macrophage-derived SAA3 monomers. SAA3 overproduction in macrophages is triggered by exosomal communication from a subset of activated MSC, which, in response to MI, acquire the expression of a platelet aggregation-inducing type I transmembrane glycoprotein named Podoplanin (PDPN). Cardiac MSC PDPN+ communicate with and activate macrophages through their extracellular vesicles or exosomes. Specifically, MSC PDPN+ derived exosomes (MSC PDPN+ Exosomes) are enriched in SAA3 and exosomal SAA3 protein engages with Toll-like receptor 2 (TRL2) on macrophages, triggering an overproduction and impaired clearance of SAA3 proteins, resulting in aggregation of SAA3 monomers as rigid amyloid deposits in the extracellular space. The onset of amyloid fibers deposition alongside extra-cellular-matrix (ECM) proteins in the ischemic heart exacerbates the rigidity and stiffness of the scar, hindering the contractility of viable myocardium and overall impairing organ function. Using SAA3 and TLR2 deficient mouse models, we show that SAA3 delivered by MSC PDPN+ exosomes promotes post-MI amyloidosis. Inhibition of SAA3 aggregation via administration of a retro-inverso D-peptide, specifically designed to bind SAA3 monomers, prevents the deposition of SAA3 amyloid fibrils, positively modulates the scar formation, and improves heart function post-MI. Conclusion: Overall, our findings provide mechanistic insights into post-MI amyloidosis and suggest that SAA3 may be an attractive target for effective scar reversal after ischemic injury and a potential target in multiple diseases characterized by a similar pattern of inflammation and amyloid deposition. NOVELTY AND SIGNIFICANCE: What is known? Accumulation of rigid amyloid structures in the left ventricular wall impairs ventricle contractility.After myocardial infarction cardiac Mesenchymal Stromal Cells (MSC) acquire Podoplanin (PDPN) to better interact with immune cells.Amyloid structures can accumulate in the heart after chronic inflammatory conditions. What information does this article contribute? Whether accumulation of cumbersome amyloid structures in the ischemic scar impairs left ventricle contractility, and scar reversal after myocardial infarction (MI) has never been investigated.The pathophysiological relevance of PDPN acquirement by MSC and the functional role of their secreted exosomes in the context of post-MI cardiac remodeling has not been investigated.Amyloid structures are present in the scar after ischemia and are composed of macrophage-derived Serum Amyloid A (SAA) 3 monomers, although mechanisms of SAA3 overproduction is not established. SUMMARY OF NOVELTY AND SIGNIFICANCE: Here, we report that amyloidosis, a secondary phenomenon of an already preexisting and prolonged chronic inflammatory condition, occurs after MI and that amyloid structures are composed of macrophage-derived SAA3 monomers. Frequently studied cardiac amyloidosis are caused by aggregation of immunoglobulin light chains, transthyretin, fibrinogen, and apolipoprotein in a healthy heart as a consequence of systemic chronic inflammation leading to congestive heart failure with various types of arrhythmias and tissue stiffness. Although chronic MI is considered a systemic inflammatory condition, studies regarding the possible accumulation of amyloidogenic proteins after MI and the mechanisms involved in that process are yet to be reported. Here, we show that SAA3 overproduction in macrophages is triggered in a Toll-like Receptor 2 (TLR2)-p38MAP Kinase-dependent manner by exosomal communication from a subset of activated MSC, which, in response to MI, express a platelet aggregation-inducing type I transmembrane glycoprotein named Podoplanin. We provide the full mechanism of this phenomenon in murine models and confirm SAA3 amyloidosis in failing human heart samples. Moreover, we developed a retro-inverso D-peptide therapeutic approach, "DRI-R5S," specifically designed to bind SAA3 monomers and prevent post-MI aggregation and deposition of SAA3 amyloid fibrils without interfering with the innate immune response.

Tipifarnib Reduces Extracellular Vesicles and Protects From Heart Failure.

BACKGROUND: Heart failure (HF) is one of the leading causes of mortality worldwide. Extracellular vesicles, including small extracellular vesicles or exosomes, and their molecular cargo are known to modulate cell-to-cell communication during multiple cardiac diseases. However, the role of systemic extracellular vesicle biogenesis inhibition in HF models is not well documented and remains unclear. METHODS: We investigated the role of circulating exosomes during cardiac dysfunction and remodeling in a mouse transverse aortic constriction (TAC) model of HF. Importantly, we investigate the efficacy of tipifarnib, a recently identified exosome biogenesis inhibitor that targets the critical proteins (Rab27a [Ras associated binding protein 27a], nSMase2 [neutral sphingomyelinase 2], and Alix [ALG-2-interacting protein X]) involved in exosome biogenesis for this mouse model of HF. In this study, 10-week-old male mice underwent TAC surgery were randomly assigned to groups with and without tipifarnib treatment (10 mg/kg 3 times/wk) and monitored for 8 weeks, and a comprehensive assessment was conducted through performed echocardiographic, histological, and biochemical studies. RESULTS: TAC significantly elevated circulating plasma exosomes and markedly increased cardiac left ventricular dysfunction, cardiac hypertrophy, and fibrosis. Furthermore, injection of plasma exosomes from TAC mice induced left ventricular dysfunction and cardiomyocyte hypertrophy in uninjured mice without TAC. On the contrary, treatment of tipifarnib in TAC mice reduced circulating exosomes to baseline and remarkably improved left ventricular functions, hypertrophy, and fibrosis. Tipifarnib treatment also drastically altered the miRNA profile of circulating post-TAC exosomes, including miR 331-5p, which was highly downregulated both in TAC circulating exosomes and in TAC cardiac tissue. Mechanistically, miR 331-5p is crucial for inhibiting the fibroblast-to-myofibroblast transition by targeting HOXC8, a critical regulator of fibrosis. Tipifarnib treatment in TAC mice upregulated the expression of miR 331-5p that acts as a potent repressor for one of the fibrotic mechanisms mediated by HOXC8. CONCLUSIONS: Our study underscores the pathological role of exosomes in HF and fibrosis in response to pressure overload. Tipifarnib-mediated inhibition of exosome biogenesis and cargo sorting may serve as a viable strategy to prevent progressive cardiac remodeling in HF.

Epigenetic mechanisms regulate sex differences in cardiac reparative functions of bone marrow progenitor cells.

Historically, a lower incidence of cardiovascular diseases (CVD) and related deaths in women as compared with men of the same age has been attributed to female sex hormones, particularly estrogen and its receptors. Autologous bone marrow stem cell (BMSC) clinical trials for cardiac cell therapy overwhelmingly included male patients. However, meta-analysis data from these trials suggest a better functional outcome in postmenopausal women as compared with aged-matched men. Mechanisms governing sex-specific cardiac reparative activity in BMSCs, with and without the influence of sex hormones, remain unexplored. To discover these mechanisms, Male (M), female (F), and ovariectomized female (OVX) mice-derived EPCs were subjected to a series of molecular and epigenetic analyses followed by in vivo functional assessments of cardiac repair. F-EPCs and OVX EPCs show a lower inflammatory profile and promote enhanced cardiac reparative activity after intra-cardiac injections in a male mouse model of myocardial infarction (MI). Epigenetic sequencing revealed a marked difference in the occupancy of the gene repressive H3K9me3 mark, particularly at transcription start sites of key angiogenic and proinflammatory genes in M-EPCs compared with F-EPCs and OVX-EPCs. Our study unveiled that functional sex differences in EPCs are, in part, mediated by differential epigenetic regulation of the proinflammatory and anti-angiogenic gene CCL3, orchestrated by the control of H3K9me3 by histone methyltransferase, G9a/Ehmt2. Our research highlights the importance of considering the sex of donor cells for progenitor-based tissue repair.

Role of circular RNA cdr1as in modulation of macrophage phenotype.

AIMS: Macrophages are crucial for the initiation and resolution of an inflammatory response. Non-coding circular RNAs are ubiquitously expressed in mammalian tissue, highly conserved among species, and recently implicated in the regulation of macrophage activation. We sought to determine whether circRNAs modulate monocyte/macrophage biology and function. MATERIALS AND METHODS: We performed circRNA microarray analyses to assess transcriptome changes using RNA isolated from bone marrow derived macrophages polarized to a pro-inflammatory phenotype (INFγ + TNFα) or an anti-inflammatory phenotype (IL-10, IL-4, and TGF-ß). Among differentially expressed circRNAs, circ-Cdr1as was chosen for further investigation. Additionally, we performed loss or gain of function studies to investigate if circ-Cdr1as is involved in phenotypic switching. For gain of function, we overexpressed circ-Cdr1as using pc3.1 plasmid with laccase2 flanking regions to promote circularization. For loss of function, we used a lentiviral short hairpin RNA targeting the circ-Cdr1as splicing junction. KEY FINDINGS: Among circRNAs that are highly conserved and differentially expressed in pro- and anti-inflammatory lineages, circ-Cdr1as was one of the most downregulated in pro-inflammatory macrophages and significantly upregulated in anti-inflammatory macrophages in vitro. Overexpression of circ-Cdr1as increased transcription of anti-inflammatory markers and percentage of CD206+ cells in naïve and pro-inflammatory macrophages in vitro. Meanwhile, knockdown decreased transcription of anti-inflammatory markers and increased the percentage of CD86+ cells in naïve and anti-inflammatory macrophages in vitro. SIGNIFICANCE: This study suggests that circ-Cdr1as plays a key role in regulating anti-inflammatory phenotype of macrophages and may potentially be developed as an anti-inflammatory regulator in tissue inflammation.

Diabetes impairs cardioprotective function of endothelial progenitor cell-derived extracellular vesicles via H3K9Ac inhibition.

Background and Purpose: Myocardial infarction (MI) in diabetic patients results in higher mortality and morbidity. We and others have previously shown that bone marrow-endothelial progenitor cells (EPCs) promote cardiac neovascularization and attenuate ischemic injury. Lately, small extracellular vesicles (EVs) have emerged as major paracrine effectors mediating the benefits of stem cell therapy. Modest clinical outcomes of autologous cell-based therapies suggest diabetes-induced EPC dysfunction and may also reflect their EV derivatives. Moreover, studies suggest that post-translational histone modifications promote diabetes-induced vascular dysfunctions. Therefore, we tested the hypothesis that diabetic EPC-EVs may lose their post-injury cardiac reparative function by modulating histone modification in endothelial cells (ECs). Methods: We collected EVs from the culture medium of EPCs isolated from non-diabetic (db/+) and diabetic (db/db) mice and examined their effects on recipient ECs and cardiomyocytes in vitro, and their reparative function in permanent ligation of left anterior descending (LAD) coronary artery and ischemia/reperfusion (I/R) myocardial ischemic injuries in vivo. Results: Compared to db/+ EPC-EVs, db/db EPC-EVs promoted EC and cardiomyocyte apoptosis and repressed tube-forming capacity of ECs. In vivo, db/db EPC-EVs depressed cardiac function, reduced capillary density, and increased fibrosis compared to db/+ EPC-EV treatments after MI. Moreover, in the I/R MI model, db/+ EPC-EV-mediated acute cardio-protection was lost with db/db EPC-EVs, and db/db EPC-EVs increased immune cell infiltration, infarct area, and plasma cardiac troponin-I. Mechanistically, histone 3 lysine 9 acetylation (H3K9Ac) was significantly decreased in cardiac ECs treated with db/db EPC-EVs compared to db/+ EPC-EVs. The H3K9Ac chromatin immunoprecipitation sequencing (ChIP-Seq) results further revealed that db/db EPC-EVs reduced H3K9Ac level on angiogenic, cell survival, and proliferative genes in cardiac ECs. We found that the histone deacetylase (HDAC) inhibitor, valproic acid (VPA), partly restored diabetic EPC-EV-impaired H3K9Ac levels, tube formation and viability of ECs, and enhanced cell survival and proliferative genes, Pdgfd and Sox12, expression. Moreover, we observed that VPA treatment improved db/db EPC-mediated post-MI cardiac repair and functions. Conclusions: Our findings unravel that diabetes impairs EPC-EV reparative function in the ischemic heart, at least partially, through HDACs-mediated H3K9Ac downregulation leading to transcriptional suppression of angiogenic, proliferative and cell survival genes in recipient cardiac ECs. Thus, HDAC inhibitors may potentially be used to restore the function of diabetic EPC and other stem cells for autologous cell therapy applications.

Serum-Derived Small Extracellular Vesicles From Diabetic Mice Impair Angiogenic Property of Microvascular Endothelial Cells: Role of EZH2.

Background Impaired angiogenic abilities of the microvascular endothelial cell (MVEC) play a crucial role in diabetes mellitus-impaired ischemic tissue repair. However, the underlying mechanisms of diabetes mellitus-impaired MVEC function remain unclear. We studied the role of serum-derived small extracellular vesicles (ssEVs) in diabetes mellitus-impaired MVEC function. Methods and Results ssEVs were isolated from 8-week-old male db/db and db/+ mice by ultracentrifugation and size/number were determined by the Nano-sight tracking system. Diabetic ssEVs significantly impaired tube formation and migration abilities of human MVECs. Furthermore, local transplantation of diabetic ssEVs strikingly reduced blood perfusion and capillary/arteriole density in ischemic hind limb of wildtype C57BL/6J mice. Diabetic ssEVs decreased secretion/expression of several pro-angiogenic factors in human MVECs. Mechanistically, expression of enhancer of zest homolog 2 (EZH2), the major methyltransferase responsible for catalyzing H3K27me3 (a transcription repressive maker), and H3K27me3 was increased in MVECs from db/db mice. Diabetic ssEVs increased EZH2 and H3K27me3 expression/activity in human MVECs. Expression of EZH2 mRNA was increased in diabetic ssEVs. EZH2-specific inhibitor significantly reversed diabetic ssEVs-enhanced expression of EZH2 and H3K27me3, impaired expression of angiogenic factors, and improved blood perfusion and vessel density in ischemic hind limb of C57BL/6J mice. Finally, EZH2 inactivation repressed diabetic ssEVs-induced H3K27me3 expression at promoter of pro-angiogenic genes. Conclusions Diabetic ssEVs impair the angiogenic property of MVECs via, at least partially, transferring EZH2 mRNA to MVECs, thus inducing the epigenetic mechanism involving EZH2-enhanced expression of H3K27me3 and consequent silencing of pro-angiogenic genes. Our findings unravel the cellular mechanism and expand the scope of bloodborne substances that impair MVEC function in diabetes mellitus.

Author Correction: Circular RNA CircFndc3b modulates cardiac repair after myocardial infarction via FUS/VEGF-A axis.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Circular RNA CircFndc3b modulates cardiac repair after myocardial infarction via FUS/VEGF-A axis.

Circular RNAs are generated from many protein-coding genes, but their role in cardiovascular health and disease states remains unknown. Here we report identification of circRNA transcripts that are differentially expressed in post myocardial infarction (MI) mouse hearts including circFndc3b which is significantly down-regulated in the post-MI hearts. Notably, the human circFndc3b ortholog is also significantly down-regulated in cardiac tissues of ischemic cardiomyopathy patients. Overexpression of circFndc3b in cardiac endothelial cells increases vascular endothelial growth factor-A expression and enhances their angiogenic activity and reduces cardiomyocytes and endothelial cell apoptosis. Adeno-associated virus 9 -mediated cardiac overexpression of circFndc3b in post-MI hearts reduces cardiomyocyte apoptosis, enhances neovascularization and improves left ventricular functions. Mechanistically, circFndc3b interacts with the RNA binding protein Fused in Sarcoma to regulate VEGF expression and signaling. These findings highlight a physiological role for circRNAs in cardiac repair and indicate that modulation of circFndc3b expression may represent a potential strategy to promote cardiac function and remodeling after MI.

Elucidating the role of Agl in bladder carcinogenesis by generation and characterization of genetically engineered mice.

Amylo-α-1,6-glucosidase,4-α-glucanotransferase (AGL) is an enzyme primarily responsible for glycogen debranching. Germline mutations lead to glycogen storage disease type III (GSDIII). We recently found AGL to be a tumor suppressor in xenograft models of human bladder cancer (BC) and low levels of AGL expression in BC are associated with poor patient prognosis. However, the impact of low AGL expression on the susceptibility of normal bladder to carcinogenesis is unknown. We address this gap by developing a germline Agl knockout (Agl-/-) mouse that recapitulates biochemical and histological features of GSDIII. Agl-/- mice exposed to N-butyl-N-(4-hydroxybutyl) nitrosamine (BBN) had a higher BC incidence compared with wild-type mice (Agl+/+). To determine if the increased BC incidence observed was due to decreased Agl expression in the urothelium specifically, we developed a urothelium-specific conditional Agl knockout (Aglcko) mouse using a Uroplakin II-Cre allele. BBN-induced carcinogenesis experiments repeated in Aglcko mice revealed that Aglcko mice had a higher BC incidence than control (Aglfl/fl) mice. RNA sequencing revealed that tumors from Agl-/- mice had 19 differentially expressed genes compared with control mice. An 'Agl Loss' gene signature was developed and found to successfully stratify normal and tumor samples in two BC patient datasets. These results support the role of AGL loss in promoting carcinogenesis and provide a rationale for evaluating Agl expression levels, or Agl Loss gene signature scores, in normal urothelium of populations at risk of BC development such as older male smokers.

PEGylation of an osteoclast inhibitory peptide: suitable candidate for the treatment of osteoporosis.

Osteoporosis is a condition of bone loss due to excessive osteoclastic activity. Several protein factors, such as receptor activator of nuclear factor kappa-B (RANK), receptor activator of nuclear factor kappa-B ligand (RANKL), osteoprotegerin (OPG), have been identified that are important in the pathogenesis of osteoporosis. RANKL binds to RANK and activates the NF-κB pathway by interaction of its cytoplasmic domain with an intracellular adapter protein, TNF receptor associated factors 6 (TRAF 6). This interaction can be inhibited by cell-permeable peptides that prevent RANK-TRAF 6 interaction. However, similar to the peptides/proteins used in clinical setting, the effective application of this TRAF 6 Inhibitory peptide as a therapeutic agent is marred by several limitations for instance short half-life, rapid renal clearance and immunogenicity. In the present study, we have developed PEGylated TRAF 6 Inhibitory peptide by conjugating TRAF 6 Inhibitory peptide to linear PEG backbone that exhibits longer bioavailability in plasma in the animal model. Besides, it has an enhanced uptake at its site of action, i.e., bone marrow.