Midkine gene transfer after myocardial infarction in rats prevents remodelling and ameliorates cardiac dysfunction

Tongmai Yangxin pill alleviates myocardial no-reflow by activating GPER to regulate HIF-1α signaling and downstream potassium channels

CONTEXT

The Tongmai Yangxin pill (TMYX) has potential clinical effects on no-reflow (NR); however, the effective substances and mechanisms remain unclear.

OBJECTIVE

This study evaluates the cardioprotective effects and molecular mechanisms of TMYX against NR.

MATERIALS AND METHODS

We used a myocardial NR rat model to confirm the effect and mechanism of action of TMYX in alleviating NR. Sprague-Dawley (SD) rats were divided into Control (Con), sham, NR, TMYX (4.0 g/kg), and sodium nitroprusside (SNP, 5.0 mg/kg), and received their treatments once a day for one week. In vitro studies in isolated coronary microvasculature of NR rats and in silico network pharmacology analyses were performed to reveal the underlying mechanisms of TMYX and determine the main components, targets, and pathways of TMYX, respectively.

RESULTS

TMYX (4.0 g/kg) showed therapeutic effects on NR by improving the cardiac structure and function, reducing NR, ischemic areas, and cardiomyocyte injury, and decreasing the expression of cardiac troponin I (cTnI). Moreover, the mechanism of TMYX predicted by network pharmacology is related to the HIF-1, NF-κB, and TNF signaling pathways. In vivo, TMYX decreased the expression of MPO, NF-κB, and TNF-α and increased the expression of GPER, p-ERK, and HIF-1α. In vitro, TMYX enhanced the diastolic function of coronary microvascular cells; however, this effect was inhibited by G-15, H-89, L-NAME, ODQ and four K⁺ channel inhibitors.

CONCLUSIONS

TMYX exerts its pharmacological effects in the treatment of NR via multiple targets. However, the contribution of each pathway was not detected, and the mechanisms should be further investigated.

Novel Targets Regulating the Role of Endothelial Cells and Angiogenesis after Infarction: A RNA Sequencing Analysis

Endothelial cells (ECs) are a key target for cardioprotection due to their role in preserving cardiac microvasculature and homeostasis after myocardial infarction (MI). Our goal is to identify the genes involved in post-MI EC proliferation, EC apoptosis, and angiogenesis regulation via RNA-sequencing transcriptomic datasets. Using eight studies from the Gene Expression Omnibus, RNA-sequencing data from 92 mice submitted to different times of coronary ischemia or sham were chosen. Functional enrichment analysis was performed based on gene ontology biological processes (BPs). Apoptosis-related BPs are activated up to day 3 after ischemia onset, whereas endothelial proliferation occurs from day 3 onwards, including an overrepresentation of up to 37 genes. Endothelial apoptosis post-MI is triggered via both the extrinsic and intrinsic signaling pathways, as reflected by the overrepresentation of 13 and 2 specific genes, respectively. BPs implicated in new vessel formation are upregulated soon after ischemia onset, whilst the mechanisms aiming at angiogenesis repression can be detected at day 3. Overall, 51 pro-angiogenic and 29 anti-angiogenic factors displayed altered transcriptomic expression post-MI. This is the first study using RNA sequencing datasets to evaluate the genes participating in post-MI endothelium physiology and angiogenesis regulation. These novel data could lay the groundwork to advance understanding of the implication of ECs after MI.

Assessment of the Cardiac Noncoding Transcriptome by Single-Cell RNA Sequencing Identifies FIXER, a Conserved Profibrogenic Long Noncoding RNA

BACKGROUND

Cardiac fibroblasts have crucial roles in the heart. In particular, fibroblasts differentiate into myofibroblasts in the damaged myocardium, contributing to scar formation and interstitial fibrosis. Fibrosis is associated with heart dysfunction and failure. Myofibroblasts therefore represent attractive therapeutic targets. However, the lack of myofibroblast-specific markers has precluded the development of targeted therapies. In this context, most of the noncoding genome is transcribed into long noncoding RNAs (lncRNAs). A number of lncRNAs have pivotal functions in the cardiovascular system. lncRNAs are globally more cell-specific than protein-coding genes, supporting their importance as key determinants of cell identity.

METHODS

In this study, we evaluated the value of the lncRNA transcriptome in very deep single-cell RNA sequencing. We profiled the lncRNA transcriptome in cardiac nonmyocyte cells after infarction and probed heterogeneity in the fibroblast and myofibroblast populations. In addition, we searched for subpopulation-specific markers that can constitute novel targets in therapy for heart disease.

RESULTS

We demonstrated that cardiac cell identity can be defined by the sole expression of lncRNAs in single-cell experiments. In this analysis, we identified lncRNAs enriched in relevant myofibroblast subpopulations. Selecting 1 candidate we named FIXER (fibrogenic LOX-locus enhancer RNA), we showed that its silencing limits fibrosis and improves heart function after infarction. Mechanitically, FIXER interacts with CBX4, an E3 SUMO protein ligase and transcription factor, guiding CBX4 to the promoter of the transcription factor RUNX1 to control its expression and, consequently, the expression of a fibrogenic gene program.. FIXER is conserved in humans, supporting its translational value.

CONCLUSIONS

Our results demonstrated that lncRNA expression is sufficient to identify the various cell types composing the mammalian heart. Focusing on cardiac fibroblasts and their derivatives, we identified lncRNAs uniquely expressed in myofibroblasts. In particular, the lncRNA FIXER represents a novel therapeutic target for cardiac fibrosis.

Cardioprotective factors against myocardial infarction selected in vivo from an AAV secretome library

Therapies for patients with myocardial infarction and heart failure are urgently needed, in light of the breadth of these conditions and lack of curative treatments. To systematically identify previously unidentified cardioactive biologicals in an unbiased manner in vivo, we developed cardiac FunSel, a method for the systematic, functional selection of effective factors using a library of 1198 barcoded adeno-associated virus (AAV) vectors encoding for the mouse secretome. By pooled vector injection into the heart, this library was screened to functionally select for factors that confer cardioprotection against myocardial infarction. After two rounds of iterative selection in mice, cardiac FunSel identified three proteins [chordin-like 1 (Chrdl1), family with sequence similarity 3 member C (Fam3c), and Fam3b] that preserve cardiomyocyte viability, sustain cardiac function, and prevent pathological remodeling. In particular, Chrdl1 exerted its protective activity by binding and inhibiting extracellular bone morphogenetic protein 4 (BMP4), which resulted in protection against cardiomyocyte death and induction of autophagy in cardiomyocytes after myocardial infarction. Chrdl1 also inhibited fibrosis and maladaptive cardiac remodeling by binding transforming growth factor-β (TGF-β) and preventing cardiac fibroblast differentiation into myofibroblasts. Production of secreted and circulating Chrdl1, Fam3c, and Fam3b from the liver also protected the heart from myocardial infarction, thus supporting the use of the three proteins as recombinant factors. Together, these findings disclose a powerful method for the in vivo, unbiased selection of tissue-protective factors and describe potential cardiac therapeutics.

Effect of empagliflozin on circulating proteomics in heart failure: mechanistic insights into the EMPEROR programme

AIMS

Sodium-glucose co-transporter 2 (SGLT2) inhibitors improve cardiovascular outcomes in diverse patient populations, but their mechanism of action requires further study. The aim is to explore the effect of empagliflozin on the circulating levels of intracellular proteins in patients with heart failure, using large-scale proteomics.

METHODS AND RESULTS

Over 1250 circulating proteins were measured at baseline, Week 12, and Week 52 in 1134 patients from EMPEROR-Reduced and EMPEROR-Preserved, using the Olink® Explore 1536 platform. Statistical and bioinformatical analyses identified differentially expressed proteins (empagliflozin vs. placebo), which were then linked to demonstrated biological actions in the heart and kidneys. At Week 12, 32 of 1283 proteins fulfilled our threshold for being differentially expressed, i.e. their levels were changed by ≥10% with a false discovery rate <1% (empagliflozin vs. placebo). Among these, nine proteins demonstrated the largest treatment effect of empagliflozin: insulin-like growth factor-binding protein 1, transferrin receptor protein 1, carbonic anhydrase 2, erythropoietin, protein-glutamine gamma-glutamyltransferase 2, thymosin beta-10, U-type mitochondrial creatine kinase, insulin-like growth factor-binding protein 4, and adipocyte fatty acid-binding protein 4. The changes of the proteins from baseline to Week 52 were generally concordant with the changes from the baseline to Week 12, except empagliflozin reduced levels of kidney injury molecule-1 by ≥10% at Week 52, but not at Week 12. The most common biological action of differentially expressed proteins appeared to be the promotion of autophagic flux in the heart, kidney or endothelium, a feature of 6 proteins. Other effects of differentially expressed proteins on the heart included the reduction of oxidative stress, inhibition of inflammation and fibrosis, and the enhancement of mitochondrial health and energy, repair, and regenerative capacity. The actions of differentially expressed proteins in the kidney involved promotion of autophagy, integrity and regeneration, suppression of renal inflammation and fibrosis, and modulation of renal tubular sodium reabsorption.

CONCLUSIONS

Changes in circulating protein levels in patients with heart failure are consistent with the findings of experimental studies that have shown that the effects of SGLT2 inhibitors are likely related to actions on the heart and kidney to promote autophagic flux, nutrient deprivation signalling and transmembrane sodium transport.

Midkine release during hemodialysis is predictive of hypervolemia and associates with excess (cardiovascular) mortality in patients with end-stage renal disease: a prospective study

Background

In end-stage renal disease, a high cardiovascular risk profile and endothelial damage prevails. The heparin-binding growth factor midkine stimulates neo-angiogenesis in ischemic diseases, coordinates neutrophil influx, and raises blood pressure through stimulated angiotensin synthesis.

Methods

We determined changes of midkine serum levels during hemodialysis sessions under the assumption that endothelial cell-derived midkine is released. Periprocedural differences (∆midkine) were calculated and correlated with cardiovacular biomarkers and fluid status (clinical assessment, V. cava collapse, comet tail phenomenon), cardiovascular morbidities, mortality rates. Blood was collected before and after dialysis from hemodialysis patients (n = 171; diabetes: n = 70; hypervolemia: n = 83; both: n = 32).

Results

Baseline midkine levels were ~ fourfold elevated compared to healthy controls (n = 100). Further, on average a tenfold rise was detected during dialysis, the extent of which was partially related to non-fractionated heparin application (r² = 0.17). Inter-individual differences were highly reproducible. Hypervolemic patients responded with a less than average rise in midkine levels during dialysis (p < 0.02), this difference became more obvious with co-existing diabetes (p < 0.001 for long dialysis-free interval) and was confirmed in an independently enrolled dialysis cohort (n = 88). In Kaplan Meier survival curves, low delta midkine levels correlated with cardiovascular/overall mortality rates, similar to elevated uPAR levels, whereas other markers (NTproANP, galectin, tenascin-C) were less predictive. Following intervention with successful fluid removal in hypervolemic dialysis patients to optimize fluid homeostasis, midkine values increased (p < 0.002), which was not observed in patients that failed to decrease weight.

Conclusion

Thus, for dialysis patients inadequate periprocedural midkine upregulation is linked with hypervolemia and associates with cardiovascular events.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11255-022-03141-4.

The growth factor/cytokine midkine may participate in cytokine storm and contribute to the pathogenesis of severe acute respiratory syndrome coronavirus 2-infected patients

Background

The current coronavirus disease 2019 (COVID-19) outbreak caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has emerged in Wuhan, China, and has rapidly become a global challenge, creating major challenges to health systems in almost every country in the world it has turned into a pandemic. COVID-19 poses a risky clinical situation that can range from mild illness to severe respiratory failure, requiring admission to intensive care.

Main body

It is known that SARS-CoV-2 infection causes a cytokine storm in some critically ill patients. However, more and more evidence showed that there is a dramatic increase in cytokine levels in patients diagnosed with COVID-19. Midkine (MK) is involved in various physiological and pathological processes, which some of them are desired and beneficial such as controlling tissue repair and antimicrobial effects, but some others are harmful such as promoting inflammation, carcinogenesis, and chemoresistance. Also, MK is expressed in inflammatory cells and released by endothelial cells under hypoxic conditions.

Conclusions

Considering all this information, there are strong data that midkine, an important cytokine known to increase in inflammatory diseases, may be overexpressed in patients who are positive for COVID-19. The overexpression of MK reveals a picture leading to fibrosis and damage in the lung. Therefore, questions arise about how the expression  of  MK  changes in COVID-19 patients and can we use it as an inflammation biomarker or in the treatment protocol in the future.

Midkine-a Regulates the Formation of a Fibrotic Scar During Zebrafish Heart Regeneration

Unlike the hearts of mammals, the adult zebrafish heart regenerates after injury. Heart cryoinjury in zebrafish triggers the formation of a fibrotic scar that gradually degrades, leading to regeneration. Midkine-a (Mdka) is a multifunctional cytokine that is activated after cardiac injury. Here, we investigated the role of mdka in zebrafish heart regeneration. We show that mdka expression was induced at 1-day post-cryoinjury (dpci) throughout the epicardial layer, whereas by 7 dpci expression had become restricted to the epicardial cells covering the injured area. To study the role of mdka in heart regeneration, we generated mdka-knock out (KO) zebrafish strains. Analysis of injured hearts showed that loss of mdka decreased endothelial cell proliferation and resulted in an arrest in heart regeneration characterized by retention of a collagenous scar. Transcriptional analysis revealed increases in collagen transcription and intense TGFβ signaling activity. These results reveal a critical role for mdka in fibrosis regulation during heart regeneration.

Trauma, a Matter of the Heart-Molecular Mechanism of Post-Traumatic Cardiac Dysfunction

Trauma remains a leading global cause of mortality, particularly in the young population. In the United States, approximately 30,000 patients with blunt cardiac trauma were recorded annually. Cardiac damage is a predictor for poor outcome after multiple trauma, with a poor prognosis and prolonged in-hospitalization. Systemic elevation of cardiac troponins was correlated with survival, injury severity score, and catecholamine consumption of patients after multiple trauma. The clinical features of the so-called "commotio cordis" are dysrhythmias, including ventricular fibrillation and sudden cardiac arrest as well as wall motion disorders. In trauma patients with inappropriate hypotension and inadequate response to fluid resuscitation, cardiac injury should be considered. Therefore, a combination of echocardiography (ECG) measurements, echocardiography, and systemic appearance of cardiomyocyte damage markers such as troponin appears to be an appropriate diagnostic approach to detect cardiac dysfunction after trauma. However, the mechanisms of post-traumatic cardiac dysfunction are still actively being investigated. This review aims to discuss cardiac damage following trauma, focusing on mechanisms of post-traumatic cardiac dysfunction associated with inflammation and complement activation. Herein, a causal relationship of cardiac dysfunction to traumatic brain injury, blunt chest trauma, multiple trauma, burn injury, psychosocial stress, fracture, and hemorrhagic shock are illustrated and therapeutic options are discussed.

Midkine Is Elevated After Multiple Trauma and Acts Directly on Human Cardiomyocytes by Altering Their Functionality and Metabolism

Background and Purpose: Post-traumatic cardiac dysfunction often occurs in multiply injured patients (ISS ≥ 16). Next to direct cardiac injury, post-traumatic cardiac dysfunction is mostly induced by the release of inflammatory biomarkers. One of these is the heparin-binding factor Midkine, which is elevated in humans after fracture, burn injury and traumatic spinal cord injury. Midkine is associated with cardiac pathologies but the exact role of Midkine in the development of those diseases is ambiguous. The systemic profile of Midkine after multiple trauma, its effects on cardiomyocytes and the association with post-traumatic cardiac dysfunction, remain unknown.

Experimental Approach: Midkine levels were investigated in blood plasma of multiply injured humans and pigs. Furthermore, human cardiomyocytes (iPS) were cultured in presence/absence of Midkine and analyzed regarding viability, apoptosis, calcium handling, metabolic alterations, and oxidative stress. Finally, the Midkine filtration capacity of the therapeutic blood absorption column CytoSorb ®300 was tested with recombinant Midkine or plasma from multiply injured patients.

Key Results: Midkine levels were significantly increased in blood plasma of multiply injured humans and pigs. Midkine acts on human cardiomyocytes, altering their mitochondrial respiration and calcium handling in vitro. CytoSorb®300 filtration reduced Midkine concentration ex vivo and in vitro depending on the dosage.

Conclusion and Implications: Midkine is elevated in human and porcine plasma after multiple trauma, affecting the functionality and metabolism of human cardiomyocytes in vitro. Further examinations are required to determine whether the application of CytoSorb®300 filtration in patients after multiple trauma is a promising therapeutic approach to prevent post-traumatic cardiac disfunction.

Midkine drives cardiac inflammation by promoting neutrophil trafficking and NETosis in myocarditis

Heart failure due to dilated cardiomyopathy is frequently caused by myocarditis. However, the pathogenesis of myocarditis remains incompletely understood. Here, we report the presence of neutrophil extracellular traps (NETs) in cardiac tissue of patients and mice with myocarditis. Inhibition of NET formation in experimental autoimmune myocarditis (EAM) of mice substantially reduces inflammation in the acute phase of the disease. Targeting the cytokine midkine (MK), which mediates NET formation in vitro, not only attenuates NET formation in vivo and the infiltration of polymorphonuclear neutrophils (PMNs) but also reduces fibrosis and preserves systolic function during EAM. Low-density lipoprotein receptor-related protein 1 (LRP1) acts as the functionally relevant receptor for MK-induced PMN recruitment as well as NET formation. In summary, NETosis substantially contributes to the pathogenesis of myocarditis and drives cardiac inflammation, probably via MK, which promotes PMN trafficking and NETosis. Thus, MK as well as NETs may represent novel therapeutic targets for the treatment of cardiac inflammation.

PI3K/Akt and HIF‑1 signaling pathway in hypoxia‑ischemia (Review)

Hypoxia-ischemia (H-I) is frequently observed in perinatal asphyxia and other diseases. It can lead to serious cardiac injury, cerebral damage, neurological disability and mortality. Previous studies have demonstrated that the phosphatidylinositol-3 kinase (PI3K)/protein kinase B (Akt) signaling pathway, which regulates a wide range of cellular functions, is involved in the resistance response to H-I through the activation of proteins associated with survival and inactivation of apoptosis-associated proteins. It can also regulate the expression of hypoxia-induced factor-1α (HIF-1α). HIF-1α can further regulate the expression of downstream proteins involved in glucose metabolism and angiogenesis, such as vascular endothelial growth factor and erythropoietin, to facilitate ischemic adaptation. Notably, HIF-1α may also induce detrimental effects. The effects of HIF-1 on ischemic outcomes may be dependent on the H-I duration, animal age and species. Thus, further investigation of the PI3K/Akt signaling pathway may provide further insights of the potential targets for treating diseases accompanied by H-I.

Midkine's Role in Cardiac Pathology

Midkine (MDK) is a heparin-binding growth factor that is normally expressed in mid-gestational development mediating mesenchymal and epithelial interactions. As organisms age, expression of MDK diminishes; however, in adults, MDK expression is associated with acute and chronic pathologic conditions such as myocardial infarction and heart failure (HF). The role of MDK is not clear in cardiovascular disease and currently there is no consensus if it plays a beneficial or detrimental role in HF. The lack of clarity in the literature is exacerbated by differing roles that circulating and myocardial MDK play in signaling pathways in cardiomyocytes (some of which have yet to be elucidated). Of particular interest, serum MDK is elevated in adults with chronic heart failure and higher circulating MDK is associated with worse cardiac function. In addition, pediatric HF patients have higher levels of myocardial MDK. This review focuses on what is known about the effect of exogenous versus myocardial MDK in various cardiac disease models in an effort to better clarify the role of midkine in HF.

Embryological Origin of Human Smooth Muscle Cells Influences Their Ability to Support Endothelial Network Formation

Vascular smooth muscle cells (SMCs) from distinct anatomic locations derive from different embryonic origins. Here we investigated the respective potential of different embryonic origin-specific SMCs derived from human embryonic stem cells (hESCs) to support endothelial network formation in vitro. SMCs of three distinct embryological origins were derived from an mStrawberry-expressing hESC line and were cocultured with green fluorescent protein-expressing human umbilical vein endothelial cells (HUVECs) to investigate the effects of distinct SMC subtypes on endothelial network formation. Quantitative analysis demonstrated that lateral mesoderm (LM)-derived SMCs best supported HUVEC network complexity and survival in three-dimensional coculture in Matrigel. The effects of the LM-derived SMCs on HUVECs were at least in part paracrine in nature. A TaqMan array was performed to identify the possible mediators responsible for the differential effects of the SMC lineages, and a microarray was used to determine lineage-specific angiogenesis gene signatures. Midkine (MDK) was identified as one important mediator for the enhanced vasculogenic potency of LM-derived SMCs. The functional effects of MDK on endothelial network formation were then determined by small interfering RNA-mediated knockdown in SMCs, which resulted in impaired network complexity and survival of LM-derived SMC cocultures. The present study is the first to show that SMCs from distinct embryonic origins differ in their ability to support HUVEC network formation. LM-derived SMCs best supported endothelial cell network complexity and survival in vitro, in part through increased expression of MDK. A lineage-specific approach might be beneficial for vascular tissue engineering and therapeutic revascularization.

SIGNIFICANCE

Mural cells are essential for the stabilization and maturation of new endothelial cell networks. However, relatively little is known of the effect of the developmental origins of mural cells on their signaling to endothelial cells and how this affects vessel development. The present study demonstrated that human smooth muscle cells (SMCs) from distinct embryonic origins differ in their ability to support endothelial network formation. Lateral mesoderm-derived SMCs best support endothelial cell network complexity and survival in vitro, in part through increased expression of midkine. A lineage-specific approach might be beneficial for vascular tissue engineering and therapeutic revascularization.

Midkine Deteriorates Cardiac Remodeling via Epidermal Growth Factor Receptor Signaling in Chronic Kidney Disease

In chronic kidney disease, activation of the epidermal growth factor receptor (EGFR) leads to cardiac hypertrophy, which affects morbidity and mortality. In patients with renal insufficiency and heart failure, the expression of midkine, a heparin-binding growth factor, is increased. Therefore, we investigated the association between midkine and EGFR in the induction of cardiac hypertrophy and dysfunction in chronic kidney disease. We performed subtotal nephrectomies in midkine-knockout mice and wild-type mice. We found that subtotal nephrectomy-induced cardiac hypertrophy and phosphorylation of extracellular signal-regulated kinase 1/2 and AKT were attenuated in midkine-knockout mice compared with wild-type mice. An antiphosphotyrosine receptor antibody array was used to demonstrate that EGFR phosphorylation in the heart was also lower in midkine-knockout mice than in wild-type mice. Midkine induced EGFR, extracellular signal-regulated kinase 1/2, and AKT phosphorylation and led to hypertrophy in neonatal rat cardiomyocytes. Pretreatment with EGFR inhibitors or EGFR silencing suppressed midkine-stimulated phosphorylation of extracellular signal-regulated kinase 1/2 and AKT, induction of fetal cardiac gene expression, and hypertrophy in cardiomyocytes. To confirm the association between midkine and EGFR in vivo, mice subjected to subtotal nephrectomy were treated with the EGFR inhibitor gefitinib. Gefitinib treatment attenuated subtotal nephrectomy-induced cardiac hypertrophy. These results indicate that midkine might be a key mediator of cardiorenal interactions through EGFR activation, which plays a crucial role in cardiac hypertrophy in chronic kidney disease.

CTRP3 attenuates post-infarct cardiac fibrosis by targeting Smad3 activation and inhibiting myofibroblast differentiation

C1q/tumor necrosis factor-related protein-3 (CTRP3) is a novel adipokine with modulation effects on metabolism, inflammation, and cardiovascular system. This study aimed to investigate the effect of CTRP3 on cardiac fibrosis and its underlying mechanism. The myocardial expression of CTRP3 was significantly decreased after myocardial infarction (MI). Adenovirus-delivered CTRP3 supplement attenuated myocardial hypertrophy, improved cardiac function, inhibited interstitial fibrosis, and decreased the number of myofibroblasts post-MI. In cultured adult rat cardiac fibroblasts (CFs), CTRP3 attenuated cell proliferation; migration; and the expression of connective tissue growth factor, collagen I, and collagen III induced by transforming growth factor (TGF)-β1. Moreover, CTRP3 inhibited whereas CTRP3 small interfering RNA (siRNA) facilitated the expression of α-SMA and profibrotic molecules induced by TGF-β1. CTRP3 also attenuated TGF-β1-induced Smad3 phosphorylation, nuclear translocation, and interaction with p300. CTRP3 increased the phosphorylation of AMP-activated protein kinase (AMPK) and Akt in both rat hearts and CFs. Adenine 9-β-D-arabinofuranoside (AraA), an AMPK inhibitor, abolished the protective effect of CTRP3 against TGF-β1-induced profibrotic response and Smad3 activation. Taken together, CTRP3 attenuates cardiac fibrosis by inhibiting myofibroblast differentiation and the subsequent extracellular matrix production. AMPK is required for the anti-fibrotic effect of CTRP3 through targeting Smad3 activation and inhibiting myofibroblast differentiation.

KEY MESSAGE

CTRP3 alleviates cardiac fibrosis in a rat post-MI model and in cardiac fibroblasts. CTRP3 inhibits fibroblast-to-myofibroblast differentiation. CTRP3 exerts anti-fibrotic effect through targeting Smad3 activation. AMPK mediates the anti-fibrotic effect of CTRP3 by inhibition of Smad3 activation.

The therapeutic effect of rhMK on osteoarthritis in mice, induced by destabilization of the medial meniscus

Osteoarthritis (OA) is a worldwide disease in aged people, causing not only physical suffering to the patients themselves, but also a great burden on their families and on society. Here we used a mouse OA model induced by destabilization of the medial meniscus (DMM), and studied the therapeutic effect of recombinant human midkine (rhMK) on this OA model. Our results indicated that the DMM surgery induced mechanical allodynia and locomotor activity obstacles, together with cartilage injury in the C57BL/6 mice. The rhMK treatment mitigated the OA related mechanical allodynia, improved locomotor activity capacity, and prevented degradation of the cartilage. Considering the safety issue of rhMK used as a biologic, we also inspected the main organs in the rhMK treated mice throughout the process and found no pathological change. These results suggest that rhMK could be used as a biologic to treat OA or OA related pain.

C1q/tumor necrosis factor-related protein-6 attenuates post-infarct cardiac fibrosis by targeting RhoA/MRTF-A pathway and inhibiting myofibroblast differentiation

C1q/tumor necrosis factor-related protein-6 (CTRP6) is a newly identified adiponectin paralog with modulation effects on metabolism and inflammation. However, the cardiovascular function of CTRP6 remains unknown. This study aimed to determine its role in cardiac fibrosis and explore the possible mechanism. Myocardial infarction (MI) was induced by left anterior descending coronary artery ligation in rats. CTRP6 was mainly expressed in the cytoplasm of adult rat cardiomyocytes and significantly decreased in the border and infarct zones post-MI. Adenovirus-mediated CTRP6 delivery improved cardiac function, attenuated cardiac hypertrophy, alleviated cardiac fibrosis, and inhibited myofibroblast differentiation as well as the expression of collagen I, collagen III, and connective tissue growth factor post-MI. In cultured adult rat cardiac fibroblasts (CFs), exogenous or cardiomyocyte-secreted CTRP6 inhibited, whereas knockdown of CTRP6 facilitated transforming growth factor-β1 (TGF-β1)-induced expression of α-smooth muscle actin, smooth muscle 22α, and profibrotic molecules. CTRP6 had no effect on CFs proliferation but attenuated CFs migration induced by TGF-β1. CTRP6 increased the phosphorylation of AMP-activated protein kinase (AMPK) and Akt in CFs and post-MI hearts. Pretreatment with adenine 9-β-D-arabinofuranoside (AraA), an AMPK inhibitor, or LY294002, a phosphatidylinositol-3-kinase (PI3 K) inhibitor, abolished the protective effect of CTRP6 on TGF-β1-induced profibrotic response. Furthermore, CTRP6 had no effect on TGF-β1-induced Smad3 phosphorylation and nuclear translocation, whereas significantly decreased TGF-β1-induced RhoA activation and myocardin-related transcription factor-A (MRTF-A) nuclear translocation, and these effects were blocked by AMPK or Akt inhibition. In conclusion, CTRP6 attenuates cardiac fibrosis via inhibiting myofibroblast differentiation. AMPK and Akt activation are responsible for the CTRP6-mediated anti-fibrotic effect by targeting RhoA/MRTF-A pathway.

Conditioned medium from human amniotic mesenchymal stromal cells limits infarct size and enhances angiogenesis

The paracrine properties of human amniotic membrane-derived mesenchymal stromal cells (hAMCs) have not been fully elucidated. The goal of the present study was to elucidate whether hAMCs can exert beneficial paracrine effects on infarcted rat hearts, in particular through cardioprotection and angiogenesis. Moreover, we aimed to identify the putative active paracrine mediators. hAMCs were isolated, expanded, and characterized. In vitro, conditioned medium from hAMC (hAMC-CM) exhibited cytoprotective and proangiogenic properties. In vivo, injection of hAMC-CM into infarcted rat hearts limited the infarct size, reduced cardiomyocyte apoptosis and ventricular remodeling, and strongly promoted capillary formation at the infarct border zone. Gene array analysis led to the identification of 32 genes encoding for the secreted factors overexpressed by hAMCs. Among these, midkine and secreted protein acidic and rich in cysteine were also upregulated at the protein level. Furthermore, high amounts of several proangiogenic factors were detected in hAMC-CM by cytokine array. Our results strongly support the concept that the administration of hAMC-CM favors the repair process after acute myocardial infarction.

Angiogenesis and cardiac hypertrophy: maintenance of cardiac function and causative roles in heart failure

Cardiac hypertrophy is an adaptive response to physiological and pathological overload. In response to the overload, individual cardiac myocytes become mechanically stretched and activate intracellular hypertrophic signaling pathways to re-use embryonic transcription factors and to increase the synthesis of various proteins, such as structural and contractile proteins. These hypertrophic responses increase oxygen demand and promote myocardial angiogenesis to dissolve the hypoxic situation and to maintain cardiac contractile function; thus, these responses suggest crosstalk between cardiac myocytes and microvasculature. However, sustained pathological overload induces maladaptation and cardiac remodeling, resulting in heart failure. In recent years, specific understanding has increased with regard to the molecular processes and cell-cell interactions that coordinate myocardial growth and angiogenesis. In this review, we summarize recent advances in understanding the regulatory mechanisms of coordinated myocardial growth and angiogenesis in the pathophysiology of cardiac hypertrophy and heart failure.

Period 2 is essential to maintain early endothelial progenitor cell function in vitro and angiogenesis after myocardial infarction in mice

Cellular therapeutic neovascularization has been successfully performed in clinical trials for patients with ischaemia diseases. Despite the vast knowledge of cardiovascular disease and circadian biology, the role of the circadian clock in regulating angiogenesis in myocardial infarction (MI) remains poorly understood. In this study, we aimed to investigate the role and underlying mechanisms of Period 2 (Per2) in endothelial progenitor cell (EPC) function. Flow cytometry revealed lower circulating EPC proportion in per2^−/− than in wild-type (WT) mice. PER2 was abundantly expressed in early EPCs in mice. In vitro, EPCs from per2^−/− mice showed impaired proliferation, migration, tube formation and adhesion. Western blot analysis demonstrated inhibited PI3k/Akt/FoxO signalling and reduced C-X-C chemokine receptor type 4 (CXCR4) protein level in EPCs of per2^−/− mice. The impaired proliferation was blocked by activated PI3K/Akt/FoxO signalling. Direct interaction of CXCR4 and PER2 was detected in WT EPCs. To further study the effect of per2 on in vivo EPC survival and angiogenesis, we injected saline or DiI-labelled WT or per2^−/− EPC intramyocardially into mice with induced MI. Per2^−/− reduced the retention of transplanted EPCs in the myocardium, which was associated with significantly reduced DiI expression in the myocardium of MI mice. Decreased angiogenesis in the myocardium of per2^−/− EPC-treated mice coincided with decreased LV function and increased infarct size in the myocardium. Per2 may be a key factor in maintaining EPC function in vitro and in therapeutic angiogenesis in vivo.

Midkine exacerbates pressure overload-induced cardiac remodeling

Midkine is a multifunctional growth factor, and its serum levels are increased with the functional severity of heart failure. This study aimed to examine the role of midkine in heart failure pathogenesis. Midkine expression levels were increased in the kidney and lung after transverse aortic constriction (TAC) surgery, but not sufficiently increased in the heart. After TAC, phosphorylation of extracellular signal-regulated kinase1/2 and AKT, and the expression levels of foetal genes in the heart were considerably increased in transgenic mice with cardiac-specific overexpression of midkine (MK-Tg) compared with wild-type (WT) mice. MK-Tg mice showed more severe cardiac hypertrophy and dysfunction, and showed lower survival rate after TAC than WT mice. We conclude that midkine plays a critical role in cardiac hypertrophy and remodelling.

Tongxinluo Improves Cardiac Function and Ameliorates Ventricular Remodeling in Mice Model of Myocardial Infarction through Enhancing Angiogenesis

Background. Myocardial infarction (MI) is a major cause of morbidity and mortality in the world. Tongxinluo (TXL) is a traditional Chinese compound prescription which has cardioprotective functions. The present study was aimed to determine the effect of TXL on postischemic cardiac dysfunction and cardiac remodeling and to elucidate the underlying mechanisms. Methods and Results. MI was performed by ligation of left anterior descending coronary artery (LAD) in male adult mice. Mice were randomly divided into four groups: (1) sham group (Sham); (2) MI-control group (Control); (3) MI-low dose TXL group (TXL-L); and (4) MI-high dose TXL (TXL-H) group. Compared with the control group, TXL treatment restored cardiac function, increased revascularization, attenuated cardiomyocyte apoptosis, and reduced interstitial fibrosis. TXL treatment increased the phosphorylation of Akt, extracellular signal regulated kinase (ERK), and endothelial nitric oxide synthase (eNOS); the expression of phosphatidylinositol3-kinase (PI3K), hypoxia-inducible factors 1α (HIF-1α), and vascular endothelial growth factor (VEGF); and the DNA binding activity of HIF-1α after MI. Conclusion. TXL may improve cardiac function and ameliorate cardiac remodeling by increasing neovascularization through enhancing the phosphorylation of Akt and ERK, the expression and activity of HIF-1α, and the protein level of VEGF and p-eNOS.

Inhibition of the growth factor MDK/midkine by a novel small molecule compound to treat non-small cell lung cancer

Midkine (MDK) is a heparin-binding growth factor that is highly expressed in many malignant tumors, including lung cancers. MDK activates the PI3K pathway and induces anti-apoptotic activity, in turn enhancing the survival of tumors. Therefore, the inhibition of MDK is considered a potential strategy for cancer therapy. In the present study, we demonstrate a novel small molecule compound (iMDK) that targets MDK. iMDK inhibited the cell growth of MDK-positive H441 lung adenocarcinoma cells that harbor an oncogenic KRAS mutation and H520 squamous cell lung cancer cells, both of which are types of untreatable lung cancer. However, iMDK did not reduce the cell viability of MDK-negative A549 lung adenocarcinoma cells or normal human lung fibroblast (NHLF) cells indicating its specificity. iMDK suppressed the endogenous expression of MDK but not that of other growth factors such as PTN or VEGF. iMDK suppressed the growth of H441 cells by inhibiting the PI3K pathway and inducing apoptosis. Systemic administration of iMDK significantly inhibited tumor growth in a xenograft mouse model in vivo. Inhibition of MDK with iMDK provides a potential therapeutic approach for the treatment of lung cancers that are driven by MDK.

The heparin-binding growth factor midkine: the biological activities and candidate receptors

The heparin-binding growth factor midkine (MK) comprises a family with pleiotrophin/heparin-binding growth-associated molecule. The biological phenomena in which MK is involved can be categorized into five areas: (i) cancer, (ii) inflammation/immunity, (iii) blood pressure, (iv) development and (v) tissue protection. The phenotypes are clear in vivo, but the mechanisms by which MK exerts these actions are not fully understood. Candidate receptors for MK include anaplastic lymphoma kinase, protein tyrosine phosphatase ζ, Notch2, LDL receptor-related protein 1, integrins and proteoglycans. Some physical associations between these candidate receptors are also known. Because of the striking in vivo phenotypes after manipulation of MK, MK could be an important molecular target for the treatment of various diseases. To this end, it will be important to pursue studies to fully understand the mechanisms of MK action.

Loss of heparin-binding protein prevents necrotizing glomerulonephritis: first clues hint at plasminogen activator inhibitor-1

The orchestration of acute inflammatory kidney injury is subject to widespread influences and involves cytokines as well as chemokines released by resident as well as infiltrating cells. Although intense research efforts have been made in the field, it still unravels yet novel key molecules involved in the pathogenesis of this kidney disease. A heparin-binding growth factor denoted midkine is expressed by various cell types following stress of tissue damage. Specific functions relate to orchestration of reparative and inflammatory processes by promoting migration of leucocytes and release of chemokines with ensuing angiogenesis. Midkine appears as a double-edged sword with beneficial or harmful effects in injured tissues. Here, we discuss a recent publication that provides evidence for the beneficial role of midkine in progressive glomerulonephritis, most likely due to blockade of plasminogen activator inhibitor-1 release.

Lessons from the heart and ischemic limbs: midkine as anti-inflammatory mediator for kidney diseases?

Inflammatory responses ensuing ischemia involve the release of numerous mediators. Among these the heparin-binding growth factor midkine has been recognized as a potent inducer of neoangiogenesis. In a recent publication, the release of midkine has been studied in different in vitro models, and effects of abrogated midkine expression by means of genetic knockout has been analyzed in ischemia models of the limbs. The observed effects indicate a profound effect exerted by midkine under ischemia in the coordination of the inflammatory response and neoangiogenesis.

The angiogenic factor secretoneurin induces coronary angiogenesis in a model of myocardial infarction by stimulation of vascular endothelial growth factor signaling in endothelial cells

BACKGROUND

Secretoneurin is a neuropeptide located in nerve fibers along blood vessels, is upregulated by hypoxia, and induces angiogenesis. We tested the hypothesis that secretoneurin gene therapy exerts beneficial effects in a rat model of myocardial infarction and evaluated the mechanism of action on coronary endothelial cells.

METHODS AND RESULTS

In vivo secretoneurin improved left ventricular function, inhibited remodeling, and reduced scar formation. In the infarct border zone, secretoneurin induced coronary angiogenesis, as shown by increased density of capillaries and arteries. In vitro secretoneurin induced capillary tubes, stimulated proliferation, inhibited apoptosis, and activated Akt and extracellular signal-regulated kinase in coronary endothelial cells. Effects were abrogated by a vascular endothelial growth factor (VEGF) antibody, and secretoneurin stimulated VEGF receptors in these cells. Secretoneurin furthermore increased binding of VEGF to endothelial cells, and binding was blocked by heparinase, indicating that secretoneurin stimulates binding of VEGF to heparan sulfate proteoglycan binding sites. Additionally, secretoneurin increased binding of VEGF to its coreceptor neuropilin-1. In endothelial cells, secretoneurin also stimulated fibroblast growth factor receptor-3 and insulin-like growth factor-1 receptor, and in coronary vascular smooth muscle cells, we observed stimulation of VEGF receptor-1 and fibroblast growth factor receptor-3. Exposure of cardiac myocytes to hypoxia and ischemic heart after myocardial infarction revealed increased secretoneurin messenger RNA and protein.

CONCLUSIONS

Our data show that secretoneurin acts as an endogenous stimulator of VEGF signaling in coronary endothelial cells by enhancing binding of VEGF to low-affinity binding sites and neuropilin-1 and stimulates further growth factor receptors like fibroblast growth factor receptor-3. Our in vivo findings indicate that secretoneurin may be a promising therapeutic tool in ischemic heart disease.

Midkine acts as proangiogenic cytokine in hypoxia-induced angiogenesis

The cytokine midkine (MK) promotes tumor growth mainly by inducing angiogenesis. Here, we identified the source of MK in the vascular system under hypoxic conditions and demonstrated the relevance of MK during ischemia of normal tissue. Hypoxia increased MK protein expression in human polymorphonuclear neutrophils (PMN), monocytes, and human umbilical vein endothelial cells (HUVEC) compared with normoxia. Immunoelectron microscopy showed elevated cell surface expression of MK in PMN and monocytes during hypoxia. However, only HUVEC released significant amounts of soluble MK during hypoxia compared with normoxia (301 ± 81 pg/ml vs. 158 ± 45 pg/ml; P < 0.05). Exogenous MK induced neovascularization in a chorioallantoic membrane (CAM) assay compared with negative control as measured by counting the number of branching points per visual field (1,074 ± 54 vs. 211 ± 70; P < 0.05). In a hind limb ischemia model, the angiogenic response was almost completely absent in MK-deficient mice, whereas control animals showed a profound angiogenic response measured as proliferating endothelial cells per visual field (45 ± 30 vs. 169 ± 34; P < 0.01). These unanticipated results identified endothelial cells as the source of soluble MK in the vascular system during hypoxia and defined MK as a pivotal player of angiogenesis during ischemia in nonmalignant tissue.

Midkine in the pathology of cancer, neural disease, and inflammation

Midkine (MK) is a heparin-binding growth factor involved in various cellular processes such as cellular proliferation, survival, and migration. In addition to these typical growth factor activities, MK exhibits several other activities related to fibrinolysis, blood pressure, host defense and other processes. Many cell-surface receptors have been identified to account for the multiple biological activities of MK. The expression of MK is frequently upregulated in many types of human carcinoma. Moreover, blood MK levels are closely correlated with patient outcome. Knockdown and blockade of MK suppress tumorigenesis and tumor development. Thus, MK serves as a tumor marker and a molecular target for cancer therapy. Furthermore, there is growing evidence that MK plays pivotal roles in neural and inflammatory diseases. Understanding of the mechanisms of action of MK is expected to create new therapeutic options for several human diseases.

Regulatory systems for hypoxia-inducible gene expression in ischemic heart disease gene therapy

Ischemic heart diseases are caused by narrowed coronary arteries that decrease the blood supply to the myocardium. In the ischemic myocardium, hypoxia-responsive genes are up-regulated by hypoxia-inducible factor-1 (HIF-1). Gene therapy for ischemic heart diseases uses genes encoding angiogenic growth factors and anti-apoptotic proteins as therapeutic genes. These genes increase blood supply into the myocardium by angiogenesis and protect cardiomyocytes from cell death. However, non-specific expression of these genes in normal tissues may be harmful, since growth factors and anti-apoptotic proteins may induce tumor growth. Therefore, tight gene regulation is required to limit gene expression to ischemic tissues, to avoid unwanted side effects. For this purpose, various gene expression strategies have been developed for ischemic-specific gene expression. Transcriptional, post-transcriptional, and post-translational regulatory strategies have been developed and evaluated in ischemic heart disease animal models. The regulatory systems can limit therapeutic gene expression to ischemic tissues and increase the efficiency of gene therapy. In this review, recent progresses in ischemic-specific gene expression systems are presented, and their applications to ischemic heart diseases are discussed.

Gene therapy for ischemic heart disease

INTRODUCTION

Coronary artery disease (CAD) is still the leading cause of death in industrialized nations. Even though revascularization strategies such as percutaneous coronary intervention (PCI) and coronary artery bypass graft surgery (CABG) as well as drug therapy have significantly reduced mortality, about 30% of patients will develop chronic heart failure over time. Ischemic heart disease and heart failure are characterized by an adverse remodeling of the heart, featuring cardiomyocyte hypertrophy, increased fibrosis and capillary rarification.

AREAS COVERED

Beside an assessment of current vector systems, this review focuses on potential target genes affecting angiogenesis/arteriogenesis and contractility. The potential of micro RNA (miRNA) modulation for the de-repression of survival and pro-angiogenic genes is discussed. Since gene therapy of the target region is preferable to avoid systemic contamination, application routes are discussed.

EXPERT OPINION

miRNAs are a promising new development for successful gene therapy, especially for acute myocardial infarction since their miRNA antagonists are easy to apply and appear to be selectively absorbed by the ischemic myocardial tissue. Rapid uptake and prolonged presence of known antimirs and antagomirs support this notion. For ischemic heart disease the most promising gene therapeutic approach seems to be the regional intravenous application of suitable AAV vectors and vascular growth factors, providing the full scope of angiogenesis, vessel maturation and collateral growth optionally combined with genes enhancing contractility.

Serum midkine is related to NYHA class and cystatin C in heart transplant recipients

Heart transplantation is now the established method of therapy for end-stage heart failure, with significantly improved outcomes over recent years. However, an increasingly prevalent complication in this population is that chronic kidney disease appears to be generally associated with subclinical inflammation. Midkine is a heparin-binding growth factor with various functions ranging from cell growth and survival to angiogenesis, repair, and inflammation. Recently, serum midkine has been reported to be a novel marker of cardiac events in heart failure patients. The aim of this study was to assess midkine concentration in 134 heart transplant recipients in relation to kidney function and New York Heart Association (NYHA) class. Heart transplant recipients had significantly higher serum creatinine, urea, cholesterol, triglycerides, fasting glucose, white blood cell count, and serum midkine, and lower estimated glomerular filtration rate than the control group. Serum midkine levels rose together with advancing NYHA class. Serum midkine was related to kidney function, NT-proBNP, transferrin, and prednisone dose. Cystatin C and NT-proBNP class turn out to be predictors of midkine in heart transplant recipients. Midkine levels are dependent on heart and kidney function, and might also represent a surrogate marker of subclinical inflammation.