Syndecan-4 over-expression preserves cardiac function in a rat model of myocardial infarction

Novel cardiac extracellular matrix biomarkers in STEMI: Associations with ischemic injury and long-term mortality

BACKGROUND

We aimed to determine whether serum levels of proteins related to changes in cardiac extracellular matrix (ECM) were associated with ischemic injury assessed by cardiac magnetic resonance (CMR) and mortality in patients with ST-elevation myocardial infarction (STEMI).

METHODS

The concentrations of six ECM-related proteins (periostin, osteopontin, syndecan-1, syndecan-4, bone morphogenetic protein 7, and growth differentiation factor (GDF)-15) were measured in serum samples from patients on Day 1 and Month 4 after STEMI (n = 239). Ischemic injury was assessed by myocardial salvage index, microvascular obstruction, infarct size, and left ventricular function measured by CMR conducted during the initial admission (median 2 days after admission) and after 4 months. All-cause mortality was recorded after a median follow-up time of 70 months.

RESULTS

Levels of periostin increased from Day 1 to Month 4 after hospitalization, while the levels of GDF-15, osteopontin, syndecan-1, and syndecan-4 declined. At both time points, high levels of syndecan-1 were associated with microvascular obstruction, large infarct size, and reduced left ventricular ejection fraction, whereas high levels of syndecan-4 at Month 4 were associated with a higher myocardial salvage index and less dilatation of the left ventricle. Higher mortality rates were associated with periostin levels at both time points, low syndecan-4 levels at Month 4, or high GDF-15 levels at Month 4.

CONCLUSIONS

In patients with STEMI, we found an association between serum levels of ECM biomarkers and ischemic injury and mortality. The results provide new insight into the role ECM components play in ischemic injury following STEMI and suggests a potential for these biomarkers in prognostication after STEMI.

Association between syndecan-4 and subclinical atherosclerosis in ankylosing spondylitis

BACKGROUND

Despite advances in the diagnosis and treatment of ankylosing spondylitis (AS), the risk of cardiovascular complications in AS patients is still higher than in the general population. Macrophages are at the intersection of the basic pathogenetic processes of AS and atherosclerosis. Although syndecan-4 (SDC4) mediates a variety of biological processes, the role of SDC4 in macrophage-mediated atherogenesis in AS patients remains unclear. Herein, we aimed to investigate the role of SDC4 in subclinical atherosclerosis in AS patients.

METHODS

Subjects were selected from eligible AS patients and control subjects without a prior history of AS who were referred to the rheumatology outpatient clinics. All participants' past medical records and clinical, and demographic characteristics were scanned. In addition, carotid intima-media thickness (CIMT) measurement and disease activity index measurement were applied to all patients.

RESULTS

According to our data, serum SDC4 level was significantly higher among AS patients compared with the control group (6.7 [1.5-35.0] ng/mL vs 5.1 [0.1-12.5] ng/mL, P < .001). The calculated CIMT was also significantly higher in AS patients than in the control group (0.6 [0.3-0.9] mm vs 0.4 (0.2-0.7), P < .001]. Additionally, serum C-reactive protein level and SDC4 level were independent predictors of AS and strongly associated with CIMT. Linear regression analysis showed that serum SDC4 level was the best predictor of CIMT (P = .004).

CONCLUSION

Our data indicate that serum SDC4 levels provide comprehensive information about the clinical activity of the disease and subclinical atherosclerosis in AS patients.

Keeping the Heart Healthy: The Role of Exercise in Cardiac Repair and Regeneration

Significance: Heart failure is often accompanied by a decrease in the number of cardiomyocytes. Although the adult mammalian hearts have limited regenerative capacity, the rate of regeneration is extremely low and decreases with age. Exercise is an effective means to improve cardiovascular function and prevent cardiovascular diseases. However, the molecular mechanisms of how exercise acts on cardiomyocytes are still not fully elucidated. Therefore, it is important to explore the role of exercise in cardiomyocytes and cardiac regeneration. Recent Advances: Recent advances have shown that the effects of exercise on cardiomyocytes are critical for cardiac repair and regeneration. Exercise can induce cardiomyocyte growth by increasing the size and number. It can induce physiological cardiomyocyte hypertrophy, inhibit cardiomyocyte apoptosis, and promote cardiomyocyte proliferation. In this review, we have discussed the molecular mechanisms and recent studies of exercise-induced cardiac regeneration, with a focus on its effects on cardiomyocytes. Critical Issues: There is no effective way to promote cardiac regeneration. Moderate exercise can keep the heart healthy by encouraging adult cardiomyocytes to survive and regenerate. Therefore, exercise could be a promising tool for stimulating the regenerative capability of the heart and keeping the heart healthy. Future Directions: Although exercise is an important measure to promote cardiomyocyte growth and subsequent cardiac regeneration, more studies are needed on how to do beneficial exercise and what factors are involved in cardiac repair and regeneration. Thus, it is important to clarify the mechanisms, pathways, and other critical factors involved in the exercise-mediated cardiac repair and regeneration. Antioxid. Redox Signal. 39, 1088-1107.

Inflammation and Syndecan-4 Shedding from Cardiac Cells in Ischemic and Non-Ischemic Heart Disease

Circulating biomarkers reflecting cardiac inflammation are needed to improve the diagnostics and guide the treatment of heart failure patients. The cardiac production and shedding of the transmembrane proteoglycan syndecan-4 is upregulated by innate immunity signaling pathways. Here, we investigated the potential of syndecan-4 as a blood biomarker of cardiac inflammation. Serum syndecan-4 was measured in patients with (i) non-ischemic, non-valvular dilated cardiomyopathy (DCM), with (n = 71) or without (n = 318) chronic inflammation; (ii) acute myocarditis (n = 15), acute pericarditis (n = 3) or acute perimyocarditis (23) and (iii) acute myocardial infarction (MI) at day 0, 3 and 30 (n = 119). Syndecan-4 was investigated in cultured cardiac myocytes and fibroblasts (n = 6–12) treated with the pro-inflammatory cytokines interleukin (IL)-1β and its inhibitor IL-1 receptor antagonist (IL-1Ra), or tumor necrosis factor (TNF)α and its specific inhibitor infliximab, an antibody used in treatment of autoimmune diseases. The levels of serum syndecan-4 were comparable in all subgroups of patients with chronic or acute cardiomyopathy, independent of inflammation. Post-MI, syndecan-4 levels were increased at day 3 and 30 vs. day 0. IL-1Ra attenuated IL-1β-induced syndecan-4 production and shedding in vitro, while infliximab had no effect. In conclusion, syndecan-4 shedding from cardiac myocytes and fibroblasts was attenuated by immunomodulatory therapy. Although its circulating levels were increased post-MI, syndecan-4 did not reflect cardiac inflammatory status in patients with heart disease.

Roles of Syndecan-4 in cardiac injury and repair

The heparan sulphate proteoglycan Syndecan-4 belongs to a 4-member family of transmembrane receptors. Genetic deletion of Syndecan-4 in mice causes negligible developmental abnormalities however when challenged these animals show distinct phenotypes. Synedcan-4 is expressed in many cell types in the heart and its expression is elevated in response to cardiac injury and recent studies have suggested roles for Syndecan-4 in repair mechanisms within the damaged heart. The purpose of this review is to explore these biological insights into the role of Syndecan-4 in both the injured heart and later during cardiac repair and remodeling.

Salvianolic Acid B Suppresses ER Stress-Induced NLRP3 Inflammasome and Pyroptosis via the AMPK/FoxO4 and Syndecan-4/Rac1 Signaling Pathways in Human Endothelial Progenitor Cells

Mounting evidence demonstrates uncontrolled endoplasmic reticulum (ER) stress responses can activate the inflammasome, which generally results in endothelial dysfunction, a major pathogenetic factor of chronic inflammatory diseases such as atherosclerosis. Salvianolic acid B (SalB), produced by Radix Salviae, exerts antioxidative and anti-inflammatory activities in multiple cell types. However, SalB's effects on ER stress-related inflammasome and endothelial dysfunction remain unknown. Here, we showed SalB substantially abrogated ER stress-induced cell death and reduction in capillary tube formation, with declined intracellular reactive oxygen species (ROS) amounts and restored mitochondrial membrane potential (MMP), as well as increased expression of HO-1 and SOD2 in bone marrow-derived endothelial progenitor cells (BM-EPCs). ER stress suppression by CHOP or caspase-4 siRNA transfection attenuated the protective effect of SalB. Additionally, SalB alleviated ER stress-mediated pyroptotic cell death via the suppression of TXNIP/NLRP3 inflammasome, as evidenced by reduced cleavage of caspase-1 and interleukin- (IL-) 1β and IL-18 secretion levels. Furthermore, this study provided a mechanistic basis that AMPK/FoxO4/KLF2 and Syndecan-4/Rac1/ATF2 signaling pathway modulation by SalB substantially prevented BM-EPCs damage associated with ER stress by decreasing intracellular ROS amounts and inducing NLRP3-dependent pyroptosis. In summary, our findings identify that ER stress triggered mitochondrial ROS release and NLRP3 generation in BM-EPCs, while SalB inhibits NLRP3 inflammasome-mediated pyroptotic cell death by regulating the AMPK/FoxO4/KLF2 and Syndecan-4/Rac1/ATF2 pathways. The current findings reveal SalB as a potential new candidate for the treatment of atherosclerotic heart disease.

The Role of Matrix Proteins in Cardiac Pathology

The extracellular matrix (ECM) and ECM-regulatory proteins mediate structural and cell-cell interactions that are crucial for embryonic cardiac development and postnatal homeostasis, as well as organ remodeling and repair in response to injury. These proteins possess a broad functionality that is regulated by multiple structural domains and dependent on their ability to interact with extracellular substrates and/or cell surface receptors. Several different cell types (cardiomyocytes, fibroblasts, endothelial and inflammatory cells) within the myocardium elaborate ECM proteins, and their role in cardiovascular (patho)physiology has been increasingly recognized. This has stimulated robust research dissecting the ECM protein function in human health and disease and replicating the genetic proof-of-principle. This review summarizes recent developments regarding the contribution of ECM to cardiovascular disease. The clear importance of this heterogeneous group of proteins in attenuating maladaptive repair responses provides an impetus for further investigation into these proteins as potential pharmacological targets in cardiac diseases and beyond.

Pathological Angiogenesis Requires Syndecan-4 for Efficient VEGFA-Induced VE-Cadherin Internalization

[Figure: see text].

Regulation of Myocardial Extracellular Matrix Dynamic Changes in Myocardial Infarction and Postinfarct Remodeling

The article represents literature review dedicated to molecular and cellular mechanisms underlying clinical manifestations and outcomes of acute myocardial infarction. Extracellular matrix adaptive changes are described in detail as one of the most important factors contributing to healing of damaged myocardium and post-infarction cardiac remodeling. Extracellular matrix is reviewed as dynamic constantly remodeling structure that plays a pivotal role in myocardial repair. The role of matrix metalloproteinases and their tissue inhibitors in fragmentation and degradation of extracellular matrix as well as in myocardium healing is discussed. This review provides current information about fibroblasts activity, the role of growth factors, particularly transforming growth factor β and cardiotrophin-1, colony-stimulating factors, adipokines and gastrointestinal hormones, various matricellular proteins. In conclusion considering the fact that dynamic transformation of extracellular matrix after myocardial ischemic damage plays a pivotal role in myocardial infarction outcomes and prognosis, we suggest a high importance of further investigation of mechanisms underlying extracellular matrix remodeling and cell-matrix interactions in cardiovascular diseases.

Syndecan-4 Inhibits the Development of Pulmonary Fibrosis by Attenuating TGF-β Signaling

Syndecan-4 is a transmembrane heparan sulfate proteoglycan expressed in a variety of cells, and its heparan sulfate glycosaminoglycan side chains bind to several proteins exhibiting various biological roles. The authors have previously demonstrated syndecan-4′s critical roles in pulmonary inflammation. In the current study, however, its role in pulmonary fibrosis was evaluated. Wild-type and syndecan-4-deficient mice were injected with bleomycin, and several parameters of inflammation and fibrosis were analyzed. The mRNA expression of collagen and α-smooth muscle action (α-SMA) in lung tissues, as well as the histopathological lung fibrosis score and collagen content in lung tissues, were significantly higher in the syndecan-4-deficient mice. However, the total cell count and cell differentiation in bronchoalveolar lavage fluid were equivalent between the wild-type and syndecan-4-deficient mice. Although there was no difference in the TGF-β expression in lung tissues between the wild-type and syndecan-4-deficient mice, significantly more activation of Smad3 in lung tissues was observed in the syndecan-4-deficient mice compared to the wild-type mice. Furthermore, in the in vitro experiments using lung fibroblasts, the co-incubation of syndecan-4 significantly inhibited TGF-β-induced Smad3 activation, collagen and α-SMA upregulation. Moreover, syndecan-4 knock-down by siRNA increased TGF-β-induced Smad3 activation and upregulated collagen and α-SMA expression. These findings showed that syndecan-4 inhibits the development of pulmonary fibrosis, at least in part, through attenuating TGF-β signaling.

Spotlight on the Transglutaminase 2-Heparan Sulfate Interaction

Heparan sulfate proteoglycans (HSPGs), syndecan-4 (Sdc4) especially, have been suggested as potential partners of transglutaminase-2 (TG2) in kidney and cardiac fibrosis, metastatic cancer, neurodegeneration and coeliac disease. The proposed role for HSPGs in the trafficking of TG2 at the cell surface and in the extracellular matrix (ECM) has been linked to the fibrogenic action of TG2 in experimental models of kidney fibrosis. As the TG2-HSPG interaction is largely mediated by the heparan sulfate (HS) chains of proteoglycans, in the past few years a number of studies have investigated the affinity of TG2 for HS, and the TG2 heparin binding site has been mapped with alternative outlooks. In this review, we aim to provide a compendium of the main literature available on the interaction of TG2 with HS, with reference to the pathological processes in which extracellular TG2 plays a role.

Assessment of syndecan-4 expression in the hearts of Trypanosoma cruzi-infected mice and human subjects with chronic Chagas disease cardiomyopathy

Background

Chronic Chagas cardiomyopathy (CCC) is characterized by the presence of a multifocal inflammatory response and myocardial damage, leading to fibrosis, arrhythmias and ventricular dysfunction. The expression of syndecan-4, a transmembrane proteoglycan, was previously found to be increased in the hearts of mice chronically infected with Trypanosoma cruzi. The possible involvement of syndecan-4 in the disease pathogenesis, however, remains unknown. Here we evaluated the pattern of expression of syndecan-4 in the heart tissue of T. cruzi infected mice and subjects with Chagas cardiomyopathy, correlating with the degree of inflammation and fibrosis.

Methods

The expression of syndecan-4 was evaluated by immunofluorescence and RT-qPCR in the hearts of C57Bl/6 mice at different time points after infection with the Colombian strain of T. cruzi. Immunostainings for syndecan-4 were performed in heart samples obtained from CCC patients and other etiologies of heart failure. The number of infiltrating inflammatory cells and area of fibrosis were also evaluated and quantified.

Results

In the experimental model, the number of infiltrating inflammatory cells and fibrosis area in the hearts progressively increased after the acute phase of infection, while syndecan-4 expression remained elevated in similar levels in both the acute and chronic phases. Confocal microscopy analysis demonstrated the localization of syndecan-4 expression in blood vessels, co-localized with α-SMA, a marker for vascular smooth muscle cells (VSMCs). Confocal microscopy analysis of human hearts samples showed a similar pattern of syndecan-4 expression in blood vessels. No correlation between syndecan-4 expression and inflammation or fibrosis was found in the hearts from subjects with CCC. We also compared the expression of syndecan-4 evaluated in subjects with CCC, idiopathic dilated cardiomyopathy and ischemic cardiomyopathy. No differences in the number of syndecan-4 positive vessels/mm2 were found comparing the three groups (P = 0.466), whereas CCC patients presented a higher number of infiltrating inflammatory cells, compared to the other etiologies of heart failure. Additionally, no correlation between syndecan-4 and fibrosis or numbers of inflammatory cells was found.

Conclusions

Syndecan-4 is expressed in the heart during the acute and chronic phases of Chagas disease, in association with VSMCs, independently of the degree of myocardial fibrosis or the number of infiltrating inflammatory cells.

Emerging roles of proteoglycans in cardiac remodeling

Cardiac remodeling is the response of the heart to a range of pathological stimuli. Cardiac remodeling is initially adaptive; however, if sustained, it ultimately causes adverse clinical outcomes. Cardiomyocyte loss or hypertrophy, inflammation and fibrosis are hallmarks of cardiac remodeling. Proteoglycans, which are composed of glycosaminoglycans and a core protein, are a non-structural component of the extracellular matrix. The lack of proteoglycans results in cardiovascular defects during development. Moreover, emerging evidence has indicated that proteoglycans act as significant modifiers in ischemia and pressure overload-related cardiac remodeling. Proteoglycans may also provide novel therapeutic strategies for further improvement in the prognosis of cardiovascular diseases.

Resveratrol Improves Tube Formation in AGE-Induced Late Endothelial Progenitor Cells by Suppressing Syndecan-4 Shedding

Dysfunction of endothelial progenitor cells (EPCs) contributes to cardiovascular complications in diabetes, and resveratrol has been shown to improve EPC functions. Syndecan-4 (Synd4), a cell surface heparin sulfate proteoglycan, has been shown to promote neovascularization. Thus, the present study was performed to determine whether resveratrol promoted angiogenesis of EPCs by regulating Synd4. Late EPCs were isolated from human peripheral blood and stimulated with AGEs. Western blot showed that AGEs induced Synd4 shedding in a dose- and time-dependent manner. AGE-induced Synd4 shedding was partly reversed by NAC or resveratrol, along with normalized ROS production. Overexpression of Synd4 or pretreatment of resveratrol reversed AGE-impaired tube formation of EPCs and regulated the Akt/eNOS pathway. Furthermore, resveratrol suppressed Synd4 shedding via the inhibition of oxidative stress and improved tube formation of late EPCs via the regulation of the Synd4/Akt/eNOS pathway.

Cartilage intermediate layer protein-1 alleviates pressure overload-induced cardiac fibrosis via interfering TGF-β1 signaling

Cardiac fibrosis is characterized by excessive deposition of extracellular matrix (ECM) proteins in the myocardium and results in decreased ventricular compliance and diastolic dysfunction. Cartilage intermediate layer protein-1 (CILP-1), a novel identified cardiac matricellular protein, is upregulated in most conditions associated with cardiac remodeling, however, whether CILP-1 is involved in pressure overload-induced fibrotic response is unknown. Here, we investigated whether CILP-1 was critically involved in the fibrotic remodeling induced by pressure overload. Western blot analysis and immunofluorescence staining showed that CILP-1 was predominantly detected in cardiac myocytes and to a less extent in the interstitium. In isolated adult mouse ventricular myocytes and nonmyocytes, CILP-1 was found to be mainly synthesized by myocytes. CILP-1 expression in left ventricles was upregulated in C57BL/6 mice undergoing transverse aortic constriction (TAC). Myocardial CILP-1 knockdown aggravated whereas CILP-1 overexpression attenuated TAC-induced ventricular remodeling and dysfunction, as measured by echocardiography test, morphological examination, and gene expressions of fibrotic molecules. Incubation of cardiac fibroblasts with the conditioned medium containing full-length, N-terminal, or C-terminal CILP-1 inhibited transforming growth factor (TGF)-β1-induced Smad3 phosphorylation and the subsequent profibrotic events. We first demonstrated that C-terminal CILP-1 increased Akt phosphorylation, promoted the interaction between Akt and Smad3, and suppressed Smad3 phosphorylation. Blockade of PI3K-Akt pathway attenuated the inhibitory effect of C-CILP-1 on TGF-β1-induced Smad3 activation. We conclude that CILP-1 is a novel ECM protein possessing anti-fibrotic ability in pressure overload-induced fibrotic remodeling. This anti-fibrotic effect of CILP-1 attributes to interfering TGF-β1 signaling through its N- and C- terminal fragments.

Endothelial dysfunction is a superinducer of syndecan-4: fibrogenic role of its ectodomain

Syndecan-4 (Synd4) is a member of the membrane-spanning, glycocalyx-forming proteoglycan family. It has been suggested that Synd4 participates in renal fibrosis. We compared wild-type and fibrosis-prone endothelial sirtuin 1-deficient (Sirt1^endo-/-) mice, the latter being a model of global endothelial dysfunction. We performed mass spectrometry analysis, which revealed that Synd4 was highly enriched in the secretome of renal microvascular endothelial cells obtained from Sirt1^endo-/- mice upon stimulation with transforming growth factor-β₁; notably, all detectable peptides were confined to the ectodomain of Synd4. Elevated Synd4 was due to enhanced NF-κB signaling in Sirt1^endo-/- mice, while its shedding occurred as a result of oxidative stress in Sirt1 deficiency. Synd4 expression was significantly enhanced after unilateral ureteral obstruction compared with contralateral kidneys. Furthermore, hyperplasia of renal myofibroblasts accompanied by microvascular rarefaction and overexpression of Synd4 were detected in Sirt1^endo-/- mice. The ectodomain of Synd4 acted as a chemoattractant for monocytes with higher levels of macrophages and higher expression levels of Synd4 in the extracellular matrix of Sirt1^endo-/- mice. In vitro, ectodomain application resulted in generation of myofibroblasts from cultured renal fibroblasts, while in vivo, subcapsular injection of ectodomain increased interstitial fibrosis. Moreover, the endothelial glycocalyx was reduced in Sirt1^endo-/- mice, highlighting the induction of Synd4 occurring in parallel with the depletion of its intact form and accumulation of its ectodomain in Sirt1^endo-/- mice. On the basis of our experimental results, we propose that it is the Synd4 ectodomain per se that is partially responsible for fibrosis in unilateral ureteral obstruction, especially when it is combined with endothelial dysfunction. NEW & NOTEWORTHY Our findings suggest that endothelial dysfunction induces the expression of syndecan-4 via activation of the NF-κB pathway. Furthermore, we show that syndecan-4 is shed to a greater amount because of increased oxidative stress in dysfunctional endothelial cells and that the release of the syndecan-4 ectodomain leads to tubulointerstitial fibrosis.

Syndecan-4 deficiency accelerates the transition from compensated hypertrophy to heart failure following pressure overload

Increasing evidence suggests that a mismatch between angiogenesis and myocardial growth contributes to the transition from adaptive cardiac hypertrophy to heart failure following pressure overload. Syndecan-4 is a transmembrane proteoglycan that binds to growth factors and extracellular matrix proteins and is critical in focal adhesion formation. However, its effects on coronary angiogenesis during pressure overload-induced heart failure have not been studied. Here, we hypothesize that syndecan-4 modulates cardiac remodeling in response to pressure overload through its ability to regulate adaptive angiogenesis. Syndecan-4 knockout (syndecan-4 KO) and wild-type (WT) mice were subjected to pressure overload induced by transverse aortic constriction (TAC). Syndecan-4 KO mice exhibited reduced capillary density, attenuated cardiomyocyte size, and worsened left ventricular cardiac function after TAC surgery compared with WT mice. Moreover, syndecan-4 KO mice showed a significant decrease in protein kinase C alpha expression. Our data suggest that syndecan-4 is essential for the compensated hypertrophy and the maintenance of cardiac function during the process of heart failure following pressure overload.

Syndecan-4 Is an Independent Predictor of All-Cause as Well as Cardiovascular Mortality in Hemodialysis Patients

Background

Left ventricular hypertrophy is associated withincreased mortality in hemodialysis (HD) patients.Syndecan-4 plays a role in many processes that are involved in the heart fibrosis and hypertrophy.We designed this study to prospectively determine whether syndecan-4 was predictive of mortality in a group of HD patients.

Methods

In total, 191 HD patients were included. Clinical, biochemical and echocardiographic parameters were recorded. HD patients were followed-up for 23.18 ± 4.02 months.

Results

Syndecan-4 levels correlated strongly with geometrical echocardiographic parameters and ejection fraction. Relations with pressure-related parameters were weak and only marginally significant. Using the receiver operating characteristics the optimal cut-off points in predicting all-cause as well as cardiovascular (CV) mortality were evaluated and patients were divided into low and high syndecan-4 groups. A Kaplan–Meier analysis showed that the cumulative incidences of all-cause as well as CV mortality were higher in high serum syndecan-4 group compared with those with low serum syndecan-4 (p<0.001 in both cases).A multivariate Cox proportional hazards regression analysis revealed syndecan-4 concentration to be an independent and significant predictor of all-cause (hazard ratio, 2.99; confidence interval, 2.34 to 3.113; p<0.001)as well as CV mortality (hazard ratio, 2.81;confidence interval, 2.28to3.02; p<0.001).

Conclusions

Serum syndecan-4 concentration reflects predominantly geometrical echocardiographic parameters. In HD patients serum syndecan-4 concentration is independently associated with all-cause as well as CV mortality.

Syndecan-4 regulates the bFGF-induced chemotactic migration of endothelial cells

Chemotactic migration of endothelial cells (ECs) guided by extracellular attractants is essential for blood vessel formation. Synd4 is a ubiquitous heparin sulfate proteoglycan receptor on the cell surface that has been identified to promote angiogenesis during tissue repair. Here, the role synd4 played in chemotactic migration of ECs was investigated in vitro and in vivo. Human umbilical vein endothelial cells (HUVECs) were transfected with Lenti-synd4-RNAi or Lenti-null. Cell migration was observed in a 2D-chemotaxis slide with a stable gradient of basic fibroblast growth factor (bFGF) for 18 h using time-lapse microscopy. Synd4 knockdown HUVECs showed reduced mobility compared with the control. In animal studies, Matrigel premixed with bFGF was used to induce the migration of ECs. The cells migrated less distance from the skin in the Matrigel plugs of synd4 null mice compared with the control mice. Then recombinant adenoviruses containing the synd4 gene (Ad-synd4) or null (Ad-null) were constructed to enhance the synd4 expression of migratory cells in Matrigel plugs of wild-type mice. Migratory cells with synd4 overexpression did not invade further in the Matrigel plugs of wild-type mice, but showed a high ability to proliferate.

Syndecan-4 shedding impairs macrovascular angiogenesis in diabetes mellitus

PURPOSE

Syndecan-4 (synd4) is a ubiquitous heparan sulfate proteoglycan cell surface receptor that modulates cell proliferation, migration, mechanotransduction, and endocytosis. The extracellular domain of synd4 sheds heavily in acute inflammation, but the shedding of synd4 in chronic inflammation, such as diabetes mellitus (DM), is still undefined. We investigated the alterations of synd4 endothelial expression in DM and the influence of impaired synd4 signaling on angiogenesis in human umbilical vein endothelial cells (HUVECs), diabetic rats, synd4 null mice, and db/db mice.

MATERIAL AND METHODS

HUVECs were incubated with advanced glycation end products (AGEs). Western blot analysis was used to determine synd4 protein expression and ELISA was used to detect soluble synd4 fragments. The concentration of synd4 in the aortic endothelia of diabetic rats was detected by immunohistochemical staining. Aortic ring assays were performed to study the process of angiogenesis in the diabetic rats and in synd4 null and db/db mice. Recombinant adenoviruses containing the synd4 gene or null were constructed to enhance synd4 aortic expression in db/db mice.

RESULTS

Western blot analysis showed decreased expression of the synd4 extracellular domain in HUVECs, and ELISA detected increased soluble fragments of synd4 in the media. Synd4 endothelial expression in the aortas of diabetic rats was decreased. Aortic ring assay indicated impaired angiogenesis in synd4 null and db/db mice, which was partially reversed by synd4 overexpression in db/db mice.

CONCLUSION

Synd4 shedding from vascular endothelial cells played an important role in the diabetes-related impairment of angiogenesis.

Syndecan-4 Signaling Is Required for Exercise-Induced Cardiac Hypertrophy

Cardiac hypertrophy can be broadly classified as either physiological or pathological. Physiological stimuli such as exercise cause adaptive cardiac hypertrophy and normal heart function. Pathological stimuli including hypertension and aortic valvular stenosis cause maladaptive cardiac remodeling and ultimately heart failure. Syndecan-4 (synd4) is a transmembrane proteoglycan identified as being involved in cardiac adaptation after injury, but whether it takes part in physiological cardiac hypertrophy is unclear. We observed upregulation of synd4 in exercise-induced hypertrophic myocardium. To evaluate the role of synd4 in the physiological form of cardiac hypertrophy, mice lacking synd4 (synd4^-/-) were exercised by swimming for 4 wks. Ultrasonic cardiogram (UCG) and histological analysis revealed that swimming induced the hypertrophic phenotype but was blunted in synd4^-/- compared with wild-type (WT) mice. The swimming-induced activation of Akt, a key molecule in physiological hypertrophy was also more decreased than in WT controls. In cultured cardiomyocytes, synd4 overexpression could induce cell enlargement, protein synthesis and distinct physiological molecular alternation. Akt activation also was observed in synd4-overexpressed cardiomyocytes. Furthermore, inhibition of protein kinase C (PKC) prevented the synd4-induced hypertrophic phenotype and Akt phosphorylation. This study identified an essential role of synd4 in mediation of physiological cardiac hypertrophy.

Temporal cardiac remodeling post-myocardial infarction: dynamics and prognostic implications in personalized medicine

Despite dramatic improvements in short-term mortality rates following myocardial infarction (MI), long-term survival for MI patients who progress to heart failure remains poor. MI occurs when the left ventricle (LV) is deprived of oxygen for a sufficient period of time to induce irreversible necrosis of the myocardium. The LV response to MI involves significant tissue, cellular, and molecular level modifications, as well as substantial hemodynamic changes that feedback negatively to amplify the response. Inflammation to remove necrotic myocytes and fibroblast activation to form a scar are key wound healing responses that are highly variable across individuals. Few biomarkers of early remodeling stages are currently clinically adopted. The discovery of underlying pathophysiological mechanisms and associated novel biomarkers has the potential of improving prognostic capability and therapeutic monitoring. Combining these biomarkers with other prominent ones could constitute a powerful diagnostic and prognostic tool that directly reflects the pathophysiological remodeling of the LV. Understanding temporal remodeling at the tissue, cellular, and molecular level and its link to a well-defined set of biomarkers at early stages post-MI is a prerequisite for improving personalized care and devising more successful therapeutic interventions. Here we summarize the integral mechanisms that occur during early cardiac remodeling in the post-MI setting and highlight the most prominent biomarkers for assessing disease progression.

Role of the endothelial surface layer in neutrophil recruitment

Neutrophil recruitment in most tissues is limited to postcapillary venules, where E- and P-selectins are inducibly expressed by venular endothelial cells. These molecules support neutrophil rolling via binding of PSGL-1 and other ligands on neutrophils. Selectins extend ≤ 38 nm above the endothelial plasma membrane, and PSGL-1 extends to 50 nm above the neutrophil plasma membrane. However, endothelial cells are covered with an ESL composed of glycosaminoglycans that is ≥ 500 nm thick and has measurable resistance against compression. The neutrophil surface is also covered with a surface layer. These surface layers would be expected to completely shield adhesion molecules; thus, neutrophils should not be able to roll and adhere. However, in the cremaster muscle and in many other models investigated using intravital microscopy, neutrophils clearly roll, and their rolling is easily and quickly induced. This conundrum was thought to be resolved by the observation that the induction of selectins is accompanied by ESL shedding; however, ESL shedding only partially reduces the ESL thickness (to 200 nm) and thus is insufficient to expose adhesion molecules. In addition to its antiadhesive functions, the ESL also presents neutrophil arrest-inducing chemokines. ESL heparan sulfate can also bind L-selectin expressed by the neutrophils, which contributes to rolling and arrest. We conclude that ESL has both proadhesive and antiadhesive functions. However, most previous studies considered either only the proadhesive or only the antiadhesive effects of the ESL. An integrated model for the role of the ESL in neutrophil rolling, arrest, and transmigration is needed.

Serum Syndecan-4 as a Possible Biomarker in Patients With Acute Pneumonia

BACKGROUND

Syndecan-4 is a transmembrane heparan sulfate proteoglycan expressed in a variety of cells, and glycosaminoglycan side chains of syndecan-4 bind to several proteins, suggesting several biological functions. However, the role of syndecan-4 in acute bacterial pneumonia has not yet been elucidated.

METHODS

Serum syndecan-4 levels were measured in patients with acute pneumonia, and the relationships between serum syndecan-4 levels and clinical parameters were analyzed. Next, we treated wild-type and syndecan-4-deficient mice with Streptococcus pneumoniae intranasally and analyzed the phenotype of syndecan-4-deficient mice.

RESULTS

In the patients with acute pneumonia, serum syndecan-4 levels were significantly higher than in the healthy volunteers and correlated negatively with the pneumonia severity score. In addition, in patients who improved with short-term antibiotic therapy, serum syndecan-4 levels were higher on admission and gradually increased during antibiotic therapy. Furthermore, in syndecan-4-deficient mice, the survival rate was significantly worse, and total neutrophil counts in bronchoalveolar lavage fluid, bacterial counts in blood, and plasma levels of inflammatory cytokines were significantly higher than in wild-type mice.

CONCLUSIONS

These results suggest that syndecan-4 has an anti-inflammatory function in acute pneumonia and could serve as a useful biomarker in these patients.

Fell-Muir Lecture: Syndecans: from peripheral coreceptors to mainstream regulators of cell behaviour

In the 25 years, as the first of the syndecan family was cloned, interest in these transmembrane proteoglycans has steadily increased. While four distinct members are present in mammals, one is present in invertebrates, including C. elegans that is such a powerful genetic model. The syndecans, therefore, have a long evolutionary history, indicative of important roles. However, these roles have been elusive. The knockout in the worm has a developmental neuronal phenotype, while knockouts of the syndecans in the mouse are mild and mostly limited to post-natal rather than developmental effects. Moreover, their association with high-affinity receptors, such as integrins, growth factor receptors, frizzled and slit/robo, have led to the notion that syndecans are coreceptors, with minor roles. Given that their heparan sulphate chains can gather many different protein ligands, this gave credence to views that the importance of syndecans lay with their ability to concentrate ligands and that only the extracellular polysaccharide was of significance. Syndecans are increasingly identified with roles in the pathogenesis of many diseases, including tumour progression, vascular disease, arthritis and inflammation. This has provided impetus to understanding syndecan roles in more detail. It emerges that while the cytoplasmic domains of syndecans are small, they have clear interactive capabilities, most notably with the actin cytoskeleton. Moreover, through the binding and activation of signalling molecules, it is likely that syndecans are important receptors in their own right. Here, an overview of syndecan structure and function is provided, with some prospects for the future.

Myocardial extracellular matrix: an ever-changing and diverse entity

The cardiac extracellular matrix (ECM) is a complex architectural network consisting of structural and nonstructural proteins, creating strength and plasticity. The nonstructural compartment of the ECM houses a variety of proteins, which are vital for ECM plasticity, and can be divided into 3 major groups: glycoproteins, proteoglycans, and glycosaminoglycans. The common denominator for these groups is glycosylation, which refers to the decoration of proteins or lipids with sugars. This review will discuss the fundamental role of the matrix in cardiac development, homeostasis, and remodeling, from a glycobiology point of view. Glycoproteins (eg, thrombospondins, secreted protein acidic and rich in cysteine, tenascins), proteoglycans (eg, versican, syndecans, biglycan), and glycosaminoglycans (eg, hyaluronan, heparan sulfate) are upregulated on cardiac injury and regulate key processes in the remodeling myocardium such as inflammation, fibrosis, and angiogenesis. Albeit some parallels can be made regarding the processes these proteins are involved in, their specific functions are extremely diverse. In fact, under varying conditions, individual proteins can even have opposing functions, making spatiotemporal contribution of these proteins in the rearrangement of multifaceted ECM very hard to grasp. Alterations of protein characteristics by the addition of sugars may explain the immense, yet tightly regulated, variability of the remodeling cardiac matrix. Understanding the role of glycosylation in altering the ultimate function of glycoproteins, proteoglycans, and glycosaminoglycans in the myocardium may lead to the development of new biochemical structures or compounds with great therapeutic potential for patients with heart disease.

Syndecan-2 exerts antifibrotic effects by promoting caveolin-1-mediated transforming growth factor-β receptor I internalization and inhibiting transforming growth factor-β1 signaling

RATIONALE

Alveolar transforming growth factor (TGF)-β1 signaling and expression of TGF-β1 target genes are increased in patients with idiopathic pulmonary fibrosis (IPF) and in animal models of pulmonary fibrosis. Internalization and degradation of TGF-β receptor TβRI inhibits TGF-β signaling and could attenuate development of experimental lung fibrosis.

OBJECTIVES

To demonstrate that after experimental lung injury, human syndecan-2 confers antifibrotic effects by inhibiting TGF-β1 signaling in alveolar epithelial cells.

METHODS

Microarray assays were performed to identify genes differentially expressed in alveolar macrophages of patients with IPF versus control subjects. Transgenic mice that constitutively overexpress human syndecan-2 in macrophages were developed to test the antifibrotic properties of syndecan-2. In vitro assays were performed to determine syndecan-2-dependent changes in epithelial cell TGF-β1 signaling, TGF-β1, and TβRI internalization and apoptosis. Wild-type mice were treated with recombinant human syndecan-2 during the fibrotic phase of bleomycin-induced lung injury.

MEASUREMENTS AND MAIN RESULTS

We observed significant increases in alveolar macrophage syndecan-2 levels in patients with IPF. Macrophage-specific overexpression of human syndecan-2 in transgenic mice conferred antifibrotic effects after lung injury by inhibiting TGF-β1 signaling and downstream expression of TGF-β1 target genes, reducing extracellular matrix production and alveolar epithelial cell apoptosis. In vitro, syndecan-2 promoted caveolin-1-dependent internalization of TGF-β1 and TβRI in alveolar epithelial cells, which inhibited TGF-β1 signaling and epithelial cell apoptosis. Therapeutic administration of human syndecan-2 abrogated lung fibrosis in mice.

CONCLUSIONS

Alveolar macrophage syndecan-2 exerts antifibrotic effects by promoting caveolin-1-dependent TGF-β1 and TβRI internalization and inhibiting TGF-β1 signaling in alveolar epithelial cells. Hence, molecules that facilitate TβRI degradation via endocytosis represent potential therapies for pulmonary fibrosis.