Soluble syndecans: biomarkers for diseases and therapeutic options

Adipocyte-derived shed Syndecan-4 suppresses lipolysis contributing to impaired adipose tissue browning and adaptive thermogenesis

Lipolysis in white adipose tissue (WAT) provides fatty acids as energy substrates for thermogenesis to increase energy expenditure. Syndecan-4 (Sdc4) is a transmembrane proteoglycan bearing heparan sulfate chains. Although single nucleotide polymorphisms (SNPs) of the Sdc4 gene have been identified linking to metabolic syndromes, its specific function in adipose tissue remains obscure. Here, we show that Sdc4 serves as a regulator of lipid metabolism and adaptive thermogenesis. Sdc4 expression and shedding are elevated in the white adipose tissue (WAT) of diet-induced obese mice. Adipocyte-specific deletion of Sdc4 promotes lipolysis and WAT browning, thereby raising whole-body energy expenditure to protect against diet-induced obesity. Mechanistically, fibroblast growth factor 2 (FGF2) is a paracrine factor that maintains energy homeostasis. Elevated shed Sdc4 concentrates and delivers FGF2 to fibroblast growth factor receptor 1 (FGFR1) on adipocytes, which in turn suppresses lipolysis by reducing hormone-sensitive lipase (HSL) activity, thus exaggerating adipose tissue dysfunction upon high-fat diet induction. Sdc4-deficient adipocytes show higher lipolytic and thermogenic capacity by enhancing HSL phosphorylation and UCP1 expression. Overall, our study reveals that adipocyte-derived shed Sdc4 is a novel suppressor of lipolysis, contributing to decreased energy expenditure, thus exaggerating obesity. Targeting shed Sdc4 is a potential therapeutic strategy for obesity.

Serum levels of free light chains and syndecan-1 in patients with rheumatoid arthritis and systemic lupus erythematosus

OBJECTIVES

Systemic autoimmune rheumatic diseases (SARDs) are characterized by chronic inflammation. Reliable biomarkers are crucial for diagnosis, monitoring disease progression and therapeutic responses. This study explores serum syndecan-1 (SDC-1) as a biomarker for these conditions and its relationship with free light chain (FLC) levels.

METHODS

A retrospective analysis was performed on sera from 60 patients with rheumatoid arthritis (RA) and from 60 with systemic lupus erythematosus (SLE), alongside 50 healthy donors (HD). Κ- and λ- FLCs were determined by turbidimetric assay, while SDC-1 levels were determined by ELISA. Kruskal-Wallis test, Wilcoxon Mann-Whitney U test, multivariable linear regression and Spearman's correlation were employed to compare biomarker levels across groups and to explore correlations.

RESULTS

SDC-1, κ-FLC and λ-FLC were significantly increased in RA and SLE patients compared with HD (P < 0.001), while no significant differences in the κ/λ ratio were observed among the groups (P = 0.4). A significant difference in subject age was also identified. However, multivariate regression analysis indicated that RA and SLE are significantly associated with the levels of these markers, with minimal confounding by age. A significant correlation was observed separately in all groups between the FLC markers. Conversely, no correlation was detected between SDC-1 and FLCs, nor between these markers and age or disease activity indices.

CONCLUSION

Elevated serum levels of FLCs and SDC-1 in RA and SLE patients compared with HD underscore their potential as biomarkers for SARDs. The findings also suggest sustained plasma cell activation, supporting the multifaceted role of SDC-1 in the pathogenesis of SARDs.

Endocytic Pathways Unveil the Role of Syndecans in the Seeding and Spreading of Pathological Protein Aggregates: Insights into Neurodegenerative Disorders

Alzheimer's disease and other neurodegenerative disorders are characterized by the accumulation of misfolded proteins, such as amyloid-beta, tau, and α-synuclein, which disrupt neuronal function and contribute to cognitive decline. Heparan sulfate proteoglycans, particularly syndecans, play a pivotal role in the seeding, aggregation, and spreading of toxic protein aggregates through endocytic pathways. Among these, syndecan-3 is particularly critical in regulating the internalization of misfolded proteins, facilitating their propagation in a prion-like manner. This review examines the mechanisms by which syndecans, especially SDC3, contribute to the seeding and spreading of pathological protein aggregates in neurodegenerative diseases. Understanding these endocytic pathways provides valuable insights into the potential of syndecans as biomarkers and therapeutic targets for early intervention in Alzheimer's disease and other related neurodegenerative disorders.

Syndecan-1: a key player in health and disease

Syndecan-1 (SDC-1) is a transmembrane protein localized on the basolateral surface of epithelial cells, encompassing a core protein with heparin sulfate and chondroitin sulfate glycosaminoglycan side chains. SDC-1 is involved in a panoply of cellular mechanisms including cell-to-cell adhesion, extracellular matrix interactions, cell cycle modulation, and lipid clearance. Alterations in the expression and function of SDC-1 are implicated in numerous disease entities, making it an attractive diagnostic and therapeutic target. However, despite its broad involvement in several disease processes, the underlying mechanism contributing to its diverse functions, pathogenesis, and therapeutic uses remains underexplored. Therefore, this review examines the role of SDC-1 in health and disease, focusing on liver pathologies, inflammatory diseases, infectious diseases, and cancer, and sheds light on SDC-1-based therapeutic approaches. Moreover, it delves into the mechanisms through which SDC-1 contributes to these diseases, emphasizing cell-type specific mechanisms. By comprehensively summarizing the significance of SDC-1, its association with several diseases, and its underlying mechanisms of action, the findings of this review could inform future research directions toward the development of targeted therapies and early diagnosis for a multitude of disease entities.

Association of endotheliopathy with coagulofibrinolytic reactions and disseminated intravascular coagulation after trauma: a retrospective observational study

We carried out a retrospective observational investigation to explore the association of endotheliopathy with coagulofibrinolytic reactions and the progression of disseminated intravascular coagulation (DIC) in adult trauma patients. We measured syndecan-1 (SDC-1), an indicator of endotheliopathy, and biomarkers of coagulofibrinolysis in 100 trauma patients immediately transferred to Ehime University Hospital. We evaluated the correlations between the coagulofibrinolytic parameters and SDC-1. We also investigated the association between SDC-1 elevations and the development of DIC, and determined the discriminators of DIC development. The median SDC-1 concentration was 82.7 (43.5-178.1) ng/mL. DIC developed in 16 patients (16.0%), and SDC-1 concentrations were significantly higher in DIC patients than in non-DIC patients (218.8 [134.5-798.2] ng/mL vs. 67.2 [39.6-114.5] ng/mL, p < 0.001). Receiver operating characteristic curve analysis revealed that the circulating SDC-1 level effectively predicted the progression of DIC, with an area under the curve of 0.862 (95% confidence interval [CI], 0.789-0.936). The optimal cut-off value was determined to be 92.5 ng/mL, yielding a sensitivity of 100.0% and a specificity of 67.8% (p < 0.001). A simple logistic regression analysis showed that a circulating SDC-1 concentration of > 92.5 ng/mL was significantly correlated with DIC progression (odds ratio [OR], 31.67; 95%CI: 3.97-252.31, p = 0.001). Many coagulofibrinolytic parameters were significantly correlated with SDC-1. Estimating the discriminators of DIC development by the least absolute shrinkage and selection operator (LASSO) and elastic-net regression analysis identified markers of coagulofibrinolytic activation, such as thrombin-antithrombin complex (TAT) and tissue plasminogen activator (tPA). A multivariate logistic regression model using TAT, tPA, and SDC-1 demonstrated that TAT and tPA, but not SDC-1, were independent factors predicting the development of DIC (TAT per 10 µg/L: OR, 1.14, 95%CI: 1.05-1.24, p = 0.003; tPA per 100pg/mL: OR, 1.03, 95%CI: 1.01-1.05, p = 0.003; SDC-1 per 10ng/mL: OR, 1.00, 95%CI: 0.99-1.01, p = 0.973). Mediation analysis showed that SDC-1 elevation was predominantly associated with the development of DIC indirectly through the increase in TAT (proportion mediated = 96.1%, p < 0.001), while there was no significant indirect effect of SDC-1 elevation on the role of TAT elevation in DIC development was observed (p = 0.340). The primary pathogenesis of DIC in the acute phase of trauma is likely driven by coagulofibrinolytic activation. Endotheliopathy, as reflected by elevated circulating levels of SDC-1, is strongly associated with coagulofibrinolytic responses. Although endotheliopathy may contribute to the early development of DIC through coagulation activation, its role appears to be limited.

Soluble Proteoglycans and Proteoglycan Fragments as Biomarkers of Pathological Extracellular Matrix Remodeling

Proteoglycans and their proteolytic fragments diffuse into biological fluids such as plasma, serum, urine, or synovial fluid, where they can be detected by antibodies or mass-spectrometry. Neopeptides generated by the proteolysis of proteoglycans are recognized by specific neoepitope antibodies and can act as a proxy for the activity of certain proteases. Proteoglycan and proteoglycan fragments can be potentially used as prognostic, diagnostic, or theragnostic biomarkers for several diseases characterized by dysregulated extracellular matrix remodeling such as osteoarthritis, rheumatoid arthritis, atherosclerosis, thoracic aortic aneurysms, central nervous system disorders, viral infections, and cancer. Here, we review the main mechanisms accounting for the presence of soluble proteoglycans and their fragments in biological fluids, their potential application as diagnostic, prognostic, or theragnostic biomarkers, and highlight challenges and opportunities ahead of their clinical translation.

Knockdown of SDC-1 Gene Alleviates the Metabolic Pathway for the Development of MODS

This study aims to reveal the metabolic differences between SDC-1 knockout mice and wild-type mice and the metabolic differences caused by shock in SDC-1 knockout mice by integrating transcriptomics and metabolomics. A total of 1009 differential metabolites were differentially expressed based on untargeted metabolomics and high-resolution mass spectrometry detection techniques. According to Kyoto Encyclopedia of Genes and Genomes enrichment, SDC-1 knockout significantly altered fat digestion and absorption, GnRH signaling pathway, fructose and mannose metabolism, and some other amino-related metabolic pathways and significantly modulated positively regulated longevity regulatory pathways, longevity regulatory pathways-worm, nicotinamide and niacinamide metabolism, and vitamin digestion and absorption pathways after its shock. Our findings indicate that SDC-1 knockout may have potential therapeutic effects in hemorrhagic shock by increasing nicotinamide metabolism.

A biological guide to glycosaminoglycans: current perspectives and pending questions

Mammalian glycosaminoglycans (GAGs), except hyaluronan (HA), are sulfated polysaccharides that are covalently attached to core proteins to form proteoglycans (PGs). This article summarizes key biological findings for the most widespread GAGs, namely HA, chondroitin sulfate/dermatan sulfate (CS/DS), keratan sulfate (KS), and heparan sulfate (HS). It focuses on the major processes that remain to be deciphered to get a comprehensive view of the mechanisms mediating GAG biological functions. They include the regulation of GAG biosynthesis and postsynthetic modifications in heparin (HP) and HS, the composition, heterogeneity, and function of the tetrasaccharide linkage region and its role in disease, the functional characterization of the new PGs recently identified by glycoproteomics, the selectivity of interactions mediated by GAG chains, the display of GAG chains and PGs at the cell surface and their impact on the availability and activity of soluble ligands, and on their move through the glycocalyx layer to reach their receptors, the human GAG profile in health and disease, the roles of GAGs and particular PGs (syndecans, decorin, and biglycan) involved in cancer, inflammation, and fibrosis, the possible use of GAGs and PGs as disease biomarkers, and the design of inhibitors targeting GAG biosynthetic enzymes and GAG-protein interactions to develop novel therapeutic approaches.

Endothelial injury and decline in lung function in persons living with HIV: a prospective Danish cohort study including 698 adults

Objectives

Endothelial injury may promote declining lung function. We aimed to investigate in well-treated persons living with HIV (PLWH) whether elevated levels of thrombomodulin (TM) and syndecan-1 (SDC1) are associated with excess lung function decline and worsening dyspnea.

Methods

A prospective cohort study comprising patients from the Copenhagen municipality. We included 698 PLWH with undetectable viral load. Biomarkers and demographics were measured at baseline, spirometry [forced expiratory volume in one second (FEV1) and forced vital capacity (FVC)] and dyspnea score both at baseline and 2-year follow-up.Both biomarkers were dichotomized at the 3rd quartile. Decline in lung function was estimated using a linear mixed model with patient-specific random effect. Increase in dyspnea score was estimated using a general mixed logistic regression model.

Results

We did not find an association between elevated SDC1 or TM and an excess decline in neither FEV1: SDC1: 4.5 mL/year (95% CI: -3.9-12.9, p = 0.30), TM: 2.2 mL/year (95% CI: -6.0-10.4, p = 0.60) nor FVC: SDC1: 4.1 mL/year (95% CI: -6.0-14.2, p = 0.42), TM: 1.4 mL/year (95% CI: -8.3-11.1, p = 0.78). A subgroup analysis of never-smokers was consistent with the main analysis.Likewise, we did not find any association between elevated SDC1 and TM and increase in dyspnea score: SDC1: OR 1.43 (95% CI: 0.89-2.30, p = 0.14), TM: OR 1.05 (95% CI: 0.65-1.71, p = 0.26).

Conclusion

We did not find a significant association between elevated biomarkers of endothelial injury and decline in lung function nor dyspnea.

Syndecan-1 as a prognostic biomarker in COVID-19 patients: a retrospective study of a Japanese cohort

BACKGROUND

The coronavirus disease 2019 (COVID-19) pandemic, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has had a profound global impact, with millions of confirmed cases and deaths worldwide. While most cases are mild, a subset progresses to severe respiratory complications and death, with factors such as thromboembolism, age, and underlying health conditions increasing the risk. Vascular endothelial damage has been implicated in severe outcomes, but specific biomarkers remain elusive. This study investigated syndecan-1 (SDC-1), a marker of endothelial damage, as a potential prognostic factor for COVID-19, focusing on the Japanese population, which is known for its aging demographics and high prevalence of comorbidities.

METHODS

A multicenter retrospective study of COVID-19 patients in Fukushima Prefecture in Japan who were admitted between February 2020 and August 2021 was conducted. SDC-1 levels were measured along with other clinical and laboratory parameters. Outcomes including thrombosis, 28-day survival, and disease severity were assessed, and disease severity was categorized according to established guidelines.

RESULTS

SDC-1 levels were correlated with disease severity. Patients who died from COVID-19 had greater SDC-1 levels than survivors, and the area under the receiver operating characteristic curve (AUC) analysis suggested the potential of the SDC-1 level as a predictor of mortality (AUC 0.714). K‒M analysis also revealed a significant difference in survival based on an SDC-1 cutoff of 10.65 ng/mL.

DISCUSSION

This study suggested that SDC-1 may serve as a valuable biomarker for assessing COVID-19 severity and predicting mortality within 28 days of hospitalization, particularly in the Japanese population. However, further investigations are required to assess longitudinal changes in SDC-1 levels, validate its predictive value for long-term survival, and consider its applicability to new viral variants.

CONCLUSIONS

SDC-1 is emerging as a potential biomarker for assessing the severity and life expectancy of COVID-19 in the Japanese population, offering promise for improved risk stratification and patient management in the ongoing fight against the virus.

Genetic predictors for bacterial vaginosis in women living with and at risk for HIV infection

PROBLEM

Bacterial vaginosis (BV) disproportionally impacts Black and Hispanic women, placing them at risk for HIV, sexually transmitted infections and preterm birth. It is unknown whether there are differences by genetic ancestry in BV risk or whether polymorphisms associated with BV risk differ by ancestry.

METHODS

Women's Interagency HIV Study (WIHS) participants with longitudinal Nugent scores were dichotomized as having (n = 319, Nugent 7-10) or not having BV (n = 367, Nugent 0-3). Genetic ancestry was defined by clustering of principal components from ancestry informative markers and further stratified by BV status. 627 single nucleotide polymorphisms (SNPs) across 41 genes important in mucosal defense were identified in the WIHS GWAS. A logistic regression analysis was adjusted for nongenetic predictors of BV and self-reported race/ethnicity to assess associations between genetic ancestry and genotype.

RESULTS

Self-reported race and genetic ancestry were associated with BV risk after adjustment for behavioral factors. Polymorphisms in mucosal defense genes including syndecans, cytokines and toll-like receptors (TLRs) were associated with BV in all ancestral groups.

CONCLUSIONS

The common association of syndecan, cytokine and TLR genes and the importance of immune function and inflammatory pathways in BV, suggests these should be targeted for further research on BV pathogenesis and therapeutics.

The potential involvement of glycocalyx disruption in abdominal aortic aneurysm pathogenesis

BACKGROUND

Abdominal aortic aneurysm is a weakening and expansion of the abdominal aorta. Currently, there is no drug treatment to limit abdominal aortic aneurysm growth. The glycocalyx is the outermost layer of the cell surface, mainly composed of glycosaminoglycans and proteoglycans.

OBJECTIVE

The aim of this review was to identify a potential relationship between glycocalyx disruption and abdominal aortic aneurysm pathogenesis.

METHODS

A narrative review of relevant published research was conducted.

RESULTS

Glycocalyx disruption has been reported to enhance vascular permeability, impair immune responses, dysregulate endothelial function, promote extracellular matrix remodeling and modulate mechanotransduction. All these effects are implicated in abdominal aortic aneurysm pathogenesis. Glycocalyx disruption promotes inflammation through exposure of adhesion molecules and release of proinflammatory mediators. Glycocalyx disruption affects how the endothelium responds to shear stress by reducing nitric oxide availabilty and adversely affecting the storage and release of several antioxidants, growth factors, and antithromotic proteins. These changes exacerbate oxidative stress, stimulate vascular smooth muscle cell dysfunction, and promote thrombosis, all effects implicated in abdominal aortic aneurysm pathogenesis. Deficiency of key component of the glycocalyx, such as syndecan-4, were reported to promote aneurysm formation and rupture in the angiotensin-II and calcium chloride induced mouse models of abdominal aortic aneurysm.

CONCLUSION

This review provides a summary of past research which suggests that glycocalyx disruption may play a role in abdominal aortic aneurysm pathogenesis. Further research is needed to establish a causal link between glycocalyx disruption and abdominal aortic aneurysm development.

Syndecans, Exostosins and Sulfotransferases as Potential Synovial Inflammation Moderators in Patients with Hip Osteoarthritis

The gradual deterioration of articular cartilage was thought to be the central event in osteoarthritis (OA), but recent studies demonstrated the importance of low-grade synovitis in the progression of OA. The Syndecan (SDC) family of membrane proteoglycans is known to be involved in the regulation of inflammation, but there is limited evidence considering the role of syndecans in OA synovitis. Our study aimed to investigate the hip OA synovial membrane expression patterns of SDC1, SDC2 and SDC4, as well as exostosins and sulfotransferases (enzymes involved in the polymerisation and modification of syndecans' heparan sulphate chains). Synovial membrane samples of patients with OA (24) were divided into two groups according to their Krenn synovitis score severity. The immunohistochemical expressions of SDC1, SDC2, SDC4, EXT1, EXT2, NDST1 and NDST2 in synovial intima and subintima were then analysed and compared with the control group (patients with femoral neck fracture). According to our study, the immunoexpression of SDC1, NDST1 and EXT2 is significantly increased in the intimal cells of OA synovial membrane in patients with lower histological synovitis scores and SDC4 in patients with higher synovitis scores, in comparison with non-OA controls. The difference in the expression of SDC2 among the OA and non-OA groups was insignificant. SDC1, SDC4, NDST1 and EXT2 seem to be involved as inflammation moderators in low-grade OA synovitis and, therefore, should be further investigated as potential markers of disease progression and therapeutic goals.

Targeted therapy for multiple myeloma: an overview on CD138-based strategies

Multiple myeloma (MM) is an incurable hematological disease characterized by the uncontrolled growth of plasma cells primarily in the bone marrow. Although its treatment consists of the administration of combined therapy regimens mainly based on immunomodulators and proteosome inhibitors, MM remains incurable, and most patients suffer from relapsed/refractory disease with poor prognosis and survival. The robust results achieved by immunotherapy targeting MM-associated antigens CD38 and CD319 (also known as SLAMF7) have drawn attention to the development of new immune-based strategies and different innovative compounds in the treatment of MM, including new monoclonal antibodies, antibody-drug conjugates, recombinant proteins, synthetic peptides, and adaptive cellular therapies. In this context, Syndecan1 (CD138 or SDC1), a transmembrane heparan sulfate proteoglycan that is upregulated in malignant plasma cells, has gained increasing attention in the panorama of MM target antigens, since its key role in MM tumorigenesis, progression and aggressiveness has been largely reported. Here, our aim is to provide an overview of the most important aspects of MM disease and to investigate the molecular functions of CD138 in physiologic and malignant cell states. In addition, we will shed light on the CD138-based therapeutic approaches currently being tested in preclinical and/or clinical phases in MM and discuss their properties, mechanisms of action and clinical applications.

Deciphering a Prognostic Signature Based on Soluble Mediators Defines the Immune Landscape and Predicts Prognosis in HNSCC

BACKGROUND

The study on Head and Neck Squamous Cell Carcinoma (HNSCC), a prevalent and aggressive form of head and neck cancer, focuses on the often-overlooked role of soluble mediators. The objective is to leverage a transcriptome-based risk analysis utilizing soluble mediator-related genes (SMRGs) to provide novel insights into prognosis and immunotherapy efficacy in HNSCC patients.

METHODS

We analyzed the expression and prognostic significance of 10,859 SMRGs using 502 HNSCC and 44 normal samples from the TCGA-HNSC cohort in The Cancer Genome Atlas (TCGA). The samples were divided into training and test sets in a 7:3 ratio, with an additional external validation using 40 tumor samples from the International Cancer Genome Consortium (ICGC). Key differentially expressed genes (DEGs) with prognostic significance were identified through univariate and Lasso-Cox regression analyses. A prognostic model based on 20 SMRGs was developed using Lasso and multivariate Cox regression. We assessed the clinical outcomes and immune status in high-risk (HR) and low-risk (LR) HNSCC patients utilizing the BEST databases and single-sample Gene Set Enrichment Analysis (ssGSEA).

RESULTS

The 20 SMRGs were crucial in predicting the prognosis of HNSCC, with the SMRG signature emerging as an independent prognostic indicator. Patients classified in the HR group exhibited poorer outcomes compared to those in the LR group. A nomogram, integrating clinical characteristics and risk scores, demonstrated substantial prognostic value. Immunotherapy appeared to be more effective in the LR group, possibly attributed to enhanced immune infiltration and expression of immune checkpoints.

CONCLUSIONS

The model based on soluble mediator-associated genes offers a fresh perspective for assessing the pre-immune efficacy and showcases robust predictive capabilities. This innovative approach holds significant promise in advancing the field of precision immuno-oncology research, providing valuable insights for personalized treatment strategies in HNSCC.

Mass intraoperative endothelial glycocalyx shedding affects postoperative systemic inflammation response

BACGROUND

Off-pump coronary artery bypass graft (OPCABG) has a high incidence of postoperative systemic inflammation response syndrome (SIRS), and perioperative endothelial glycocalyx layer (EGL) disruption can be one of the predisposing factors. We hypothesized that EGL shedding happened earlier in OPCABG which can influence on postoperative SIRS, and sevoflurane might preserve EGL better than propofol.

METHODS

We randomly allocated 50 patients undergoing OPCABG to receive either sevoflurane-sufentanil or propofol-sufentanil anesthesia. Plasma syndecan-1, heparan sulfate (HS), atrial natriuretic peptide (ANP), IL-6, and cardiac troponin I (cTnI) were measured. Blood samples were collected at 6 timepoints: induction (T1), before grafting (T2), after grafting(T3), surgery done (T4), postoperative day1 (POD1,T5) and POD2 (T6). SIRS criteria and sequential organ failure assessment (SOFA) score were examined.

RESULTS

There were neither differences of syndecan-1, HS, IL-6 nor of SIRS criteria or SOFA score between the sevoflurane and propofol groups. All patients were pooled as a single group for further statistical analyses, plasma syndecan-1 (P < 0.001) and IL-6 (P < 0.001) increased significantly as a function of time; syndecan-1 increasing correlated significantly with the duration of coronary graft anastomosis (r = 0.329, P = 0.026). Syndecan-1(T3) correlated significantly with ANP(T3) (r = 0.0.354, P = 0.016) and IL-6 (T5) (r = 0.570, P < 0.001). The maximum value of IL-6 correlated significantly with SIRS (r = 0.378, P = 0.010), the maximum value of SOFA score (r = 0.399, P = 0.006) and ICU days (r = 0.306, P = 0.039). The maximum value of SOFA score correlated significantly with the occurrence of SIRS (r = 0.568, P < 0.001) and ICU days (r = 0.338, P = 0.022).

CONCLUSIONS

OPCABG intraoperative early EGL shedding caused of grafts anastomosis greatly affected postoperative SIRS and SOFA score, sevoflurane did not clinically preserve EGL better.

TRIAL REGISTRATION

ChiCTR-IOR-17012535. Registered on 01/09/2017.

Novel Perspectives in Chronic Kidney Disease-Specific Cardiovascular Disease

Chronic kidney disease (CKD) affects > 10% of the global adult population and significantly increases the risk of cardiovascular disease (CVD), which remains the leading cause of death in this population. The development and progression of CVD-compared to the general population-is premature and accelerated, manifesting as coronary artery disease, heart failure, arrhythmias, and sudden cardiac death. CKD and CV disease combine to cause multimorbid cardiorenal syndrome (CRS) due to contributions from shared risk factors, including systolic hypertension, diabetes mellitus, obesity, and dyslipidemia. Additional neurohormonal activation, innate immunity, and inflammation contribute to progressive cardiac and renal deterioration, reflecting the strong bidirectional interaction between these organ systems. A shared molecular pathophysiology-including inflammation, oxidative stress, senescence, and hemodynamic fluctuations characterise all types of CRS. This review highlights the evolving paradigm and recent advances in our understanding of the molecular biology of CRS, outlining the potential for disease-specific therapies and biomarker disease detection.

Redefining metalloproteases specificity through network proteolysis

Proteolytic processes on cell surfaces and extracellular matrix (ECM) sustain cell behavior and tissue integrity in health and disease. Matrix metalloproteases (MMPs) and a disintegrin and metalloproteases (ADAMs) remodel cell microenvironments through irreversible proteolysis of ECM proteins and cell surface bioactive molecules. Pan-MMP inhibitors in inflammation and cancer clinical trials have encountered challenges due to promiscuous activities of MMPs. Systems biology advances revealed that MMPs initiate multifactorial proteolytic cascades, creating new substrates, activating or suppressing other MMPs, and generating signaling molecules. This review highlights the intricate network that underscores the role of MMPs beyond individual substrate-enzyme activities. Gaining insight into MMP function and tissue specificity is crucial for developing effective drug discovery strategies and novel therapeutics. This requires considering the dynamic cellular processes and consequences of network proteolysis.

CircKIF4A combines EIF4A3 to stabilize SDC1 expression to activate c-src/FAK and promotes TNBC progression

Triple-negative breast cancer (TNBC) is recognized for its poor prognosis and limited options for treatment. Circular RNA KIF4A (circKIF4A) was documented to be abnormally overexpressed in TNBC and was correlated with a poor survival rate. The objective of this study is to further examine the functional role of circKIF4A and its underlying mechanism. CircKIF4A was significantly upregulated in TNBC and the knockdown of circKIF4A suppressed TNBC cell proliferation, migration, and invasion. CircKIF4A was directly bound to EIF4A3, which interacted with SDC1. Knockdown of circKIF4A reduced interaction between EIF4A3 and SDC1 as well as SDC1 mRNA stability. SDC1 activated the c-src/FAK signaling pathways and finally promoted TNBC progression. circKIF4A induced TNBC progress in the in vivo mouse model via SDC1. CircKIF4A interacts with EIF4A3 to stabilize SDC1 mRNA, which activates the c-src/FAK signaling pathways and promotes TNBC progression. This may provide a potential therapy for TNBC treatment.

Positional proteomics: is the technology ready to study clinical cohorts?

INTRODUCTION

Positional proteomics provides proteome-wide information on protein termini and their modifications, uniquely enabling unambiguous identification of site-specific, limited proteolysis. Such proteolytic cleavage irreversibly modifies protein sequences resulting in new proteoforms with distinct protease-generated neo-N and C-termini and altered localization and activity. Misregulated proteolysis is implicated in a wide variety of human diseases. Protein termini, therefore, constitute a huge, largely unexplored source of specific analytes that provides a deep view into the functional proteome and a treasure trove for biomarkers.

AREAS COVERED

We briefly review principal approaches to define protein termini and discuss recent advances in method development. We further highlight the potential of positional proteomics to identify and trace specific proteoforms, with a focus on proteolytic processes altered in disease. Lastly, we discuss current challenges and potential for applying positional proteomics in biomarker and pre-clinical research.

EXPERT OPINION

Recent developments in positional proteomics have provided significant advances in sensitivity and throughput. In-depth analysis of proteolytic processes in clinical cohorts thus appears feasible in the near future. We argue that this will provide insights into the functional state of the proteome and offer new opportunities to utilize proteolytic processes altered or targeted in disease as specific diagnostic, prognostic and companion biomarkers.

Circulating Syndecan-1 Levels Are Associated with Chronological Coagulofibrinolytic Responses and the Development of Disseminated Intravascular Coagulation (DIC) after Trauma: A Retrospective Observational Study

BACKGROUND

The purpose of this study was to evaluate the association between endotheliopathy represented by high levels of circulating syndecan-1 (SDC-1) and coagulofibrinolytic responses due to trauma, which can lead to disseminated intravascular coagulation (DIC).

METHODS

We retrospectively evaluated 48 eligible trauma patients immediately admitted to our hospital and assessed SDC-1 and coagulofibrinolytic parameters for 7 days after admission. We compared the longitudinal changes of coagulofibrinolytic parameters and SDC-1 levels between two groups (high and low SDC-1) according to median SDC-1 value on admission.

RESULTS

The median circulating SDC-1 level was 99.6 (61.1-214.3) ng/mL on admission, and levels remained high until 7 days after admission. Coagulofibrinolytic responses assessed by biomarkers immediately after trauma were correlated with SDC-1 elevation (thrombin-antithrombin complex, TAT: r = 0.352, p = 0.001; antithrombin, AT: r = -0.301, p < 0.001; plasmin-α₂-plasmin inhibitor complex, PIC: r = 0.503, p = 0.035; tissue plasminogen activator, tPA: r = 0.630, p < 0.001). Sustained SDC-1 elevation was associated with intense and prolonged coagulation activation, impairment of anticoagulation, and fibrinolytic activation followed by inhibition of fibrinolysis, which are the primary responses associated with development of DIC in the acute phase of trauma. Elevation of circulating SDC-1 level was also associated with consumption coagulopathy and the need for transfusion, which revealed a significant association between high SDC-1 levels and the development of DIC after trauma (area under the curve, AUC = 0.845, cut-off value = 130.38 ng/mL, p = 0.001).

CONCLUSIONS

High circulating levels of syndecan-1 were associated with intense and prolonged coagulation activation, impairment of anticoagulation, fibrinolytic activation, and consumption coagulopathy after trauma. Endotheliopathy represented by SDC-1 elevation was associated with trauma induced coagulopathy, which can lead to the development of DIC.

Glycocalyx-Sodium Interaction in Vascular Endothelium

The glycocalyx generally covers almost all cellular surfaces, where it participates in mediating cell-surface interactions with the extracellular matrix as well as with intracellular signaling molecules. The endothelial glycocalyx that covers the luminal surface mediates the interactions of endothelial cells with materials flowing in the circulating blood, including blood cells. Cardiovascular diseases (CVD) remain a major cause of morbidity and mortality around the world. The cardiovascular risk factors start by causing endothelial cell dysfunction associated with destruction or irregular maintenance of the glycocalyx, which may culminate into a full-blown cardiovascular disease. The endothelial glycocalyx plays a crucial role in shielding the cell from excessive exposure and absorption of excessive salt, which can potentially cause damage to the endothelial cells and underlying tissues of the blood vessels. So, in this mini review/commentary, we delineate and provide a concise summary of the various components of the glycocalyx, their interaction with salt, and subsequent involvement in the cardiovascular disease process. We also highlight the major components of the glycocalyx that could be used as disease biomarkers or as drug targets in the management of cardiovascular diseases.

Conformations, interactions and functions of intrinsically disordered syndecans

Syndecans are transmembrane heparan sulfate proteoglycans present on most mammalian cell surfaces. They have a long evolutionary history, a single syndecan gene being expressed in bilaterian invertebrates. Syndecans have attracted interest because of their potential roles in development and disease, including vascular diseases, inflammation and various cancers. Recent structural data is providing important insights into their functions, which are complex, involving both intrinsic signaling through cytoplasmic binding partners and co-operative mechanisms where syndecans form a signaling nexus with other receptors such as integrins and tyrosine kinase growth factor receptors. While the cytoplasmic domain of syndecan-4 has a well-defined dimeric structure, the syndecan ectodomains are intrinsically disordered, which is linked to a capacity to interact with multiple partners. However, it remains to fully establish the impact of glycanation and partner proteins on syndecan core protein conformations. Genetic models indicate that a conserved property of syndecans links the cytoskeleton to calcium channels of the transient receptor potential class, compatible with roles as mechanosensors. In turn, syndecans influence actin cytoskeleton organization to impact motility, adhesion and the extracellular matrix environment. Syndecan clustering with other cell surface receptors into signaling microdomains has relevance to tissue differentiation in development, for example in stem cells, but also in disease where syndecan expression can be markedly up-regulated. Since syndecans have potential as diagnostic and prognostic markers as well as possible targets in some forms of cancer, it remains important to unravel structure/function relationships in the four mammalian syndecans.

Multi-Omics Endotypes in ICU Sepsis-Induced Immunosuppression

It is evident that the admission of some patients with sepsis and septic shock to hospitals is occurring late in their illness, which has contributed to the increase in poor outcomes and high fatalities worldwide across age groups. The current diagnostic and monitoring procedure relies on an inaccurate and often delayed identification by the clinician, who then decides the treatment upon interaction with the patient. Initiation of sepsis is accompanied by immune system paralysis following "cytokine storm". The unique immunological response of each patient is important to define in terms of subtyping for therapy. The immune system becomes activated in sepsis to produce interleukins, and endothelial cells express higher levels of adhesion molecules. The proportions of circulating immune cells change, reducing regulatory cells and increasing memory cells and killer cells, having long-term effects on the phenotype of CD8 T cells, HLA-DR, and dysregulation of microRNA. The current narrative review seeks to highlight the potential application of multi-omics data integration and immunological profiling at the single-cell level to define endotypes in sepsis and septic shock. The review will consider the parallels and immunoregulatory axis between cancer and immunosuppression, sepsis-induced cardiomyopathy, and endothelial damage. Second, the added value of transcriptomic-driven endotypes will be assessed through inferring regulatory interactions in recent clinical trials and studies reporting gene modular features that inform continuous metrics measuring clinical response in ICU, which can support the use of immunomodulating agents.

Acute and Chronic Systemic Inflammation: Features and Differences in the Pathogenesis, and Integral Criteria for Verification and Differentiation

Currently, there is rationale for separating the systemic manifestations of classical inflammation from systemic inflammation (SI) itself as an independent form of the general pathological process underlying the pathogenesis of the most severe acute and chronic diseases. With this aim in view, we used integral scales of acute and chronic SI (ChSI), including the following blood plasma parameters: interleukins 6, 8, 10; tumor necrosis factor alpha; C-reactive protein; D-dimer; cortisol; troponin I; myoglobin. The presence of multiple organ dysfunction according to the SOFA score was also taken into account. The effectiveness of the scales was tested in groups of intensive care patients during different periods of acute trauma, sepsis, and septic shock. The ChSI scale was applicable under systemic autoimmune diseases, chronic purulent infections, chronic limb threatening ischemia, and end-stage renal disease of various genesis. The number of examined patients was 764 in total. The scales allowed us to verify specific phases of acute SI and identify pathogenetic risk factors of lethal outcomes, as well as the most severe variants of the chronic pathologies course. These scales are open adaptable systems (in terms of the nomenclature and choice of indicators). They are primarily intended for scientific research. However, the SI verification methodology presented in this paper may be useful for developing advanced criteria for assessing both the typical links in the pathogenesis of many diseases and the severity of the overall condition of patients for clinical practice.

Trends in extracellular matrix biology

Extracellular matrixes (ECMs) are intricate 3-dimensional macromolecular networks of unique architectures with regulatory roles in cell morphology and functionality. As a dynamic native biomaterial, ECM undergoes constant but tightly controlled remodeling that is crucial for the maintenance of normal cellular behavior. Under pathological conditions like cancer, ECM remodeling ceases to be subjected to control resulting in disease initiation and progression. ECM is comprised of a staggering number of molecules that interact not only with one another, but also with neighboring cells via cell surface receptors. Such interactions, too many to tally, are of paramount importance for the identification of novel disease biomarkers and more personalized therapeutic intervention. Recent advances in big data analytics have allowed the development of online databases where researchers can take advantage of a stochastic evaluation of all the possible interactions and narrow them down to only those of interest for their study, respectively. This novel approach addresses the limitations that currently exist in studies, expands our understanding on ECM interactions, and has the potential to advance the development of targeted therapies. In this article we present the current trends in ECM biology research and highlight its importance in tissue integrity, the main interaction networks, ECM-mediated cell functional properties and issues related to pharmacological targeting.

Endothelial Damage and the Microcirculation in Critical Illness

Endothelial integrity maintains microcirculatory flow and tissue oxygen delivery. The endothelial glycocalyx is involved in cell signalling, coagulation and inflammation. Our ability to treat critically ill and septic patients effectively is determined by understanding the underpinning biological mechanisms. Many mechanisms govern the development of sepsis and many large trials for new treatments have failed to show a benefit. Endothelial dysfunction is possibly one of these biological mechanisms. Glycocalyx damage is measured biochemically. Novel microscopy techniques now mean the glycocalyx can be indirectly visualised, using sidestream dark field imaging. How the clinical visualisation of microcirculation changes relate to biochemical laboratory measurements of glycocalyx damage is not clear. This article reviews the evidence for a relationship between clinically evaluable microcirculation and biological signal of glycocalyx disruption in various diseases in ICU. Microcirculation changes relate to biochemical evidence of glycocalyx damage in some disease states, but results are highly variable. Better understanding and larger studies of this relationship could improve phenotyping and personalised medicine in the future. Damage to the glycocalyx could underpin many critical illness pathologies and having real-time information on the glycocalyx and microcirculation in the future could improve patient stratification, diagnosis and treatment.

Integrated Analysis of the microRNA–mRNA Network Predicts Potential Regulators of Atrial Fibrillation in Humans

Atrial fibrillation (AF) is a form of sustained cardiac arrhythmia and microRNAs (miRs) play crucial roles in the pathophysiology of AF. To identify novel miR–mRNA pairs, we performed RNA-seq from atrial biopsies of persistent AF patients and non-AF patients with normal sinus rhythm (SR). Differentially expressed miRs (11 down and 9 up) and mRNAs (95 up and 82 down) were identified and hierarchically clustered in a heat map. Subsequently, GO, KEGG, and GSEA analyses were run to identify deregulated pathways. Then, miR targets were predicted in the miRDB database, and a regulatory network of negatively correlated miR–mRNA pairs was constructed using Cytoscape. To select potential candidate genes from GSEA analysis, the top-50 enriched genes in GSEA were overlaid with predicted targets of differentially deregulated miRs. Further, the protein–protein interaction (PPI) network of enriched genes in GSEA was constructed, and subsequently, GO and canonical pathway analyses were run for genes in the PPI network. Our analyses showed that TNF-α, p53, EMT, and SYDECAN1 signaling were among the highly affected pathways in AF samples. SDC-1 (SYNDECAN-1) was the top-enriched gene in p53, EMT, and SYDECAN1 signaling. Consistently, SDC-1 mRNA and protein levels were significantly higher in atrial samples of AF patients. Among negatively correlated miRs, miR-302b-3p was experimentally validated to suppress SDC-1 transcript levels. Overall, our results suggested that the miR-302b-3p/SDC-1 axis may be involved in the pathogenesis of AF.

Targeting syndecan-1: new opportunities in cancer therapy

Syndecan-1 (SDC1, CD138) is one of the heparan sulfate proteoglycans and is essential for maintaining normal cell morphology, interacting with the extracellular and intracellular protein repertoire, as well as mediating signaling transduction upon environmental stimuli. The critical role of SDC1 in promoting tumorigenesis and metastasis has been increasingly recognized in various cancer types, implying a promising potential of utilizing SDC1 as a novel target for cancer therapy. This review summarizes the current knowledge on SDC1 structure and functions, including its role in tumor biology. We also discuss the highlights and limitations of current SDC1-targeted therapies as well as the obstacles in developing new therapeutic methods, offering our perspective on the future directions to target SDC1 for cancer treatment.

Altered Distribution and Expression of Syndecan-1 and -4 as an Additional Hallmark in Psoriasis

Syndecans act as independent co-receptors to exert biological activities and their altered function is associated with many pathophysiological conditions. Here, syndecan-1 and -4 were examined in lesional skin of patients with psoriasis. Immunohistochemical staining confirmed altered syndecan-1 distribution and revealed absence of syndecan-4 expression in the epidermis. Fibronectin (FN)—known to influence inflammation and keratinocyte hyperproliferation via α5β1 integrin in psoriasis—was also decreased. Syndecan-1 and -4 expression was analyzed in freshly isolated lesional psoriatic human keratinocytes (PHK) characterized based on their proliferation and differentiation properties. mRNA levels of syndecan-1 were similar between healthy and PHK, while syndecan-4 was significantly decreased. Cell growth and release of the pro-inflammatory Tumor Necrosis Factor-alpha (TNFα) were selectively and significantly induced in PHKs plated on FN. Results from co-culture of healthy keratinocytes and psoriatic fibroblasts led to the speculation that at least one factor released by fibroblasts down-regulate syndecan-1 expression in PHK plated on FN. To assay if biological treatments for psoriasis target keratinocyte proliferation, gelatin-based patches enriched with inteleukin (IL)-17α or TNFα blockers were prepared and tested using a full-thickness healthy epidermal model (Phenion^®). Immunohistochemistry analysis showed that both blockers impacted the localisation of syndecan-1 within the refined epidermis. These results provide evidence that syndecans expression are modified in psoriasis, suggesting that they may represent markers of interest in this pathology.

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.

Serum Syndecan-1: A Novel Biomarker for Pancreatic Ductal Adenocarcinoma

INTRODUCTION

Syndecan-1 (SDC1) has multiple functions in tumorigenesis in general and specifically in pancreatic cancer. We aimed to evaluate SDC1 as a diagnostic and prognostic biomarker in patients with pancreatic ductal adenocarcinoma (PDAC).

METHODS

In this case-control study, patients newly diagnosed with a biopsy-proven PDAC were enrolled alongside healthy individuals in a derivation-validation cohort design. Serum SDC1 was measured by enzyme-linked immunoassay. The diagnostic accuracy of SDC1 levels for diagnosing PDAC was computed. A unified cohort enriched with additional early-stage patients with PDAC was used to evaluate the association of SDC1 with survival outcomes and patient characteristics.

RESULTS

In the derivation cohort, serum SDC1 levels were significantly higher in patients with PDAC (n = 39) compared with healthy controls (n = 20) (40.1 ng/mL, interquartile range 29.8-95.3 vs 25.6 ng/mL, interquartile range 17.1-29.8, respectively; P < 0.001). The receiver operating characteristic analysis area under the curve was 0.847 (95% confidence interval 0.747-0.947, P < 0.001). These results were replicated in a separate age-matched validation cohort (n = 38 PDAC, n = 38 controls; area under the curve 0.844, 95% confidence interval 0.757-0.932, P < 0.001). In the combined-enriched PDAC cohort (n = 110), using a cutoff of 35 ng/mL, the median overall 5-year survival between patients below and above this cutoff was not significantly different, although a trend for better survival after 1 year was found in the lower level group (P = 0.06). There were 12 of the 110 patients with PDAC (11%) who had normal CA 19-9 in the presence of elevated SDC1.

DISCUSSION

These findings suggest serum SDC1 as a promising novel biomarker for early blood-based diagnosis of pancreatic cancer.

Thy-1 (CD90), Integrins and Syndecan 4 are Key Regulators of Skin Wound Healing

Acute skin wound healing is a multistage process consisting of a plethora of tightly regulated signaling events in specialized cells. The Thy-1 (CD90) glycoprotein interacts with integrins and the heparan sulfate proteoglycan syndecan 4, generating a trimolecular complex that triggers bi-directional signaling to regulate diverse aspects of the wound healing process. These proteins can act either as ligands or receptors, and they are critical for the successful progression of wound healing. The expression of Thy-1, integrins, and syndecan 4 is controlled during the healing process, and the lack of expression of any of these proteins results in delayed wound healing. Here, we review and discuss the roles and regulatory events along the stages of wound healing that support the relevance of Thy-1, integrins, and syndecan 4 as crucial regulators of skin wound healing.

The Role and Therapeutic Value of Syndecan-1 in Cancer Metastasis and Drug Resistance

Metastasis and relapse are major causes of cancer-related fatalities. The elucidation of relevant pathomechanisms and adoption of appropriate countermeasures are thus crucial for the development of clinical strategies that inhibit malignancy progression as well as metastasis. An integral component of the extracellular matrix, the type 1 transmembrane glycoprotein syndecan-1 (SDC-1) binds cytokines and growth factors involved in tumor microenvironment modulation. Alterations in its localization have been implicated in both cancer metastasis and drug resistance. In this review, available data regarding the structural characteristics, shedding process, and nuclear translocation of SDC-1 are detailed with the aim of highlighting strategies directly targeting SDC-1 as well as SDC-1-mediated carcinogenesis.

Circulating Syndecan-1 as a Predictor of Persistent Thrombocytopenia and Lethal Outcome: A Population Study of Patients With Suspected Sepsis Requiring Intensive Care

Background: Sepsis is defined as life-threatening organ dysfunction caused by dysregulated host responses to infection. Recent studies have suggested that endotheliopathy may be the common basis for multiple organ failure in sepsis. Under septic conditions, accumulation of proteases accelerates shedding of proteoglycans, such as syndecan-1, from the endothelial surface, resulting in augmented leukocyte adhesion to the vascular wall, enhanced vascular permeability, and intravascular coagulation. The purpose of this study was to determine the potential utility of syndecan-1 as a biomarker linking endotheliopathy to organ failure. Methods: One hundred patients with suspected infections who were admitted to the intensive care unit (ICU) at Kagoshima University Hospital were consecutively enrolled in the study. Serum syndecan-1 levels were measured using an in-house enzyme-linked immunosorbent assay. The difference between serum syndecan-1 levels in 28-day survivors and non-survivors was analyzed by the Mann-Whitney U-test. Receiver-operating characteristics curve analysis with area under the curve calculation was used to quantify the predictive performance of serum syndecan-1 for 28-day mortality. The correlations between serum syndecan-1 and coagulation markers were analyzed by Spearman's rank correlation test. Results: Serum syndecan-1 levels in non-survivors were significantly higher than those in survivors on Day 1 and Day 3 (P < 0.01). Among multiple organ failures, coagulation failure and renal failure were significantly correlated with serum syndecan-1. Spearman's rank correlation test indicated that serum syndecan-1 was weakly but significantly correlated with disseminated intravascular coagulation score (rho = 0.33, P < 0.01). Patients with serum syndecan-1 ≥21.4 ng/mL showed delayed recovery from thrombocytopenia relative to patients with serum syndecan-1 <21.4 ng/mL. Conclusions: Elevated circulating syndecan-1 on the first day of ICU admission was associated with persistent thrombocytopenia and lethal outcome in patients with suspected sepsis.

Extended disorder at the cell surface: The conformational landscape of the ectodomains of syndecans

Syndecans are membrane proteoglycans regulating extracellular matrix assembly, cell adhesion and signaling. Their ectodomains can be shed from the cell surface, and act as paracrine and autocrine effectors or as competitors of full-length syndecans. We report the first biophysical characterization of the recombinant ectodomains of the four human syndecans using biophysical techniques, and show that they behave like flexible random-coil intrinsically disordered proteins, and adopt several conformation ensembles in solution. We have characterized their conformational landscapes using native mass spectrometry (MS) and ion-mobility MS, and demonstrated that the syndecan ectodomains explore the majority of their conformational landscape, from minor compact, globular-like, conformations to extended ones. We also report that the ectodomain of syndecan-4, corresponding to a natural isoform, is able to dimerize via a disulfide bond. We have generated a three-dimensional model of the C-terminus of this dimer, which supports the dimerization via a disulfide bond. Furthermore, we have mapped the NXIP adhesion motif of syndecans and their sequences involved in the formation of ternary complexes with integrins and growth factor receptors on the major conformations of their ectodomains, and shown that these sequences are not accessible in all the conformations, suggesting that only some of them are biologically active. Lastly, although the syndecan ectodomains have a far lower number of amino acid residues than their membrane partners, their intrinsic disorder and flexibility allow them to adopt extended conformations, which have roughly the same size as the cell surface receptors (e.g., integrins and growth factor receptors) they bind to.

Endothelial dysfunction and thromboembolism in children, adolescents, and young adults with acute lymphoblastic leukemia

Endothelial dysfunction has not previously been investigated as a thrombogenic risk factor among patients with acute lymphoblastic leukemia (ALL), known to be at high risk of thromboembolism. We retrospectively explored the association between three circulating biomarkers of endothelial dysfunction (thrombomodulin, syndecan-1, VEGFR-1) measured in prospectively collected blood samples and risk of thromboembolism in 55 cases and 165 time-matched controls, treated according to the NOPHO ALL2008 protocol. In age-, sex-, and risk group-adjusted analysis, increasing levels of thrombomodulin and VEGFR-1 were independently associated with increased odds of developing thromboembolism (OR 1.37 per 1 ng/mL [95% CI 1.20‒1.56, P < 0.0001] and OR 1.21 per 100 pg/mL [95% CI 1.02‒1.21, P = 0.005], respectively). These associations remained significant when including only samples drawn >30 days before thromboembolic diagnosis. Thrombomodulin levels were on average 3.2 ng/mL (95% CI 2.6-8.2 ng/mL) higher in samples with measurable asparaginase activity (P < 0.0001). Among single nucleotide variants located in or neighboring coding genes for the three biomarkers, none were significantly associated with odds of thromboembolism. If results are validated in another cohort, thrombomodulin and VEGFR-1 could serve as predictive biomarkers, identifying patients in need of preemptive antithrombotic prophylaxis.

Expression and Role of Heparan Sulfated Proteoglycans in Pancreatic Cancer

Pancreatic cancer is a lethal condition with poor outcomes and an increasing incidence. The unfavourable prognosis is due to the lack of early symptoms and consequent late diagnosis. An effective method for the early diagnosis of pancreatic cancer is therefore sought by many researchers in the field. Heparan sulfated proteoglycan-related genes are often expressed differently in tumors than in normal tissues. Alteration of the tumor microenvironment is correlated with the ability of heparan sulfated proteoglycans to bind cytokines and growth factors and eventually to influence tumor progression. Here we discuss the importance of glypicans, syndecans, perlecan and extracellular matrix modifying enzymes, such as heparanases and sulfatases, as potential diagnostics in pancreatic cancer. We also ran an analysis on a multidimensional cancer genomics database for heparan sulfated proteoglycan-related genes, and report altered expression of some of them.

The Role of Extracellular Matrix Components in Inflammatory Bowel Diseases

The remodeling of extracellular matrix (ECM) within the intestine tissues, which simultaneously involves an increased degradation of ECM components and excessive intestinal fibrosis, is a defining trait of the progression of inflammatory bowel diseases (IBDs), which include ulcerative colitis (UC) and Crohn's disease (CD). The increased activity of proteases, especially matrix metalloproteinases (MMPs), leads to excessive degradation of the extracellular matrix and the release of protein and glycoprotein fragments, previously joined with the extracellular matrix, into the circulation. MMPs participate in regulating the functions of the epithelial barrier, the immunological response, and the process of wound healing or intestinal fibrosis. At a later stage of fibrosis during IBD, excessive formation and deposition of the matrix is observed. To assess changes in the extracellular matrix, quantitative measurement of the concentration in the blood of markers dependent on the activity of proteases, involved in the breakdown of extracellular matrix proteins as well as markers indicating the formation of a new ECM, has recently been proposed. This paper describes attempts to use the quantification of ECM components as markers to predict intestinal fibrosis and evaluate the healing process of the gut. The markers which reflect increased ECM degradation, together with the ones which show the process of creating a new matrix during IBD, allow the attainment of important information regarding the changes in the intestinal tissue, epithelial integrity and extracellular matrix remodeling. This paper contains evidence confirming that ECM remodeling is an integral part of directional cell signaling in the progression of IBD, and not only a basis for the ongoing processes.

Syndecans and Pancreatic Ductal Adenocarcinoma

Pancreatic Ductal Adenocarcinoma (PDAC) is a fatal disease with poor prognosis because patients rarely express symptoms in initial stages, which prevents early detection and diagnosis. Syndecans, a subfamily of proteoglycans, are involved in many physiological processes including cell proliferation, adhesion, and migration. Syndecans are physiologically found in many cell types and their interactions with other macromolecules enhance many pathways. In particular, extracellular matrix components, growth factors, and integrins collect the majority of syndecans associations acting as biochemical, physical, and mechanical transducers. Syndecans are transmembrane glycoproteins, but occasionally their extracellular domain can be released from the cell surface by the action of matrix metalloproteinases, converting them into soluble molecules that are capable of binding distant molecules such as extracellular matrix (ECM) components, growth factor receptors, and integrins from other cells. In this review, we explore the role of syndecans in tumorigenesis as well as their potential as therapeutic targets. Finally, this work reviews the contribution of syndecan-1 and syndecan-2 in PDAC progression and illustrates its potential to be targeted in future treatments for this devastating disease.

Circulating Levels of the Heparan Sulfate Proteoglycan Syndecan-4 Positively Associate with Blood Pressure in Healthy Premenopausal Women

Syndecans (SDCs) are transmembrane proteins that are present on most cell types where they play a role in multiple physiological processes, including cell-matrix adhesion and inflammation. Growing evidence suggests that elevated levels of both shed SDC1 and SDC4 are associated with hypertension and cardiovascular diseases, but their relationships with cardiovascular risk factors in healthy individuals are unknown. The primary objective of this study was to investigate whether serum levels of SDC4 and SDC1 were associated with body composition, hemodynamic parameters, pro-inflammatory cytokine concentrations, and urinary noradrenaline and dopamine levels in healthy women (17 African American and 20 European American) between the ages of 20 and 40 years old. Univariate analyses revealed only a significant (p < 0.05) inverse correlation between serum SDC1 and body fat percentage. On the other hand, serum SDC4 was positively correlated with systolic blood pressure, diastolic blood pressure, and urinary levels of noradrenaline and dopamine. Serum SDC4 was also a significant predictor of systolic blood pressure in a multivariate regression model that included fat-free mass and urinary dopamine levels as significant independent variables. The result did not change even adjusting for race. Our findings indicate that SDC4 has an important role in the physiological regulation of blood pressure.

MMP-9 mediated Syndecan-4 shedding correlates with osteoarthritis severity

OBJECTIVE

Osteoarthritis (OA) is a degenerative joint disease inducing the degradation of the articular cartilage. Syndecan-4 (Sdc4) is a heparan sulfate proteoglycan, expressed under inflammatory conditions and by chondrocytes during OA. Little is known about Sdc4 shedding and its regulation in OA. Therefore, we investigated the regulation of Sdc4 shedding and underlying shedding mechanisms under OA conditions.

DESIGN

Articular cartilage, serum, synovial fluid and synovial membrane from OA patients with different radiological severity were analyzed. ELISA, RT-qPCR and IHC for Sdc4, MMP-2 and -9 were performed. MMP inhibitors and siRNA were evaluated for their effect on Sdc4 shedding by ELISA and on IL-1 signaling by western blot (pERK/ERK).

RESULTS

Shed Sdc4 was increased in synovial fluid of OA patients, but not in the serum and is a good predictor (AUC = 0.72) for OA severity with a sensitivity of 67.5% and specificity 65.2%. MMP-9, but not MMP-2, was increased in cartilage and synovial membrane at mRNA levels and in the synovial fluid at protein levels. Shed Sdc4 correlated with the amount of MMP-9 in synovial fluid. Further, the inhibition and knock-down of MMP-9 decreased the amount of shed Sdc4 in vitro. Increased Sdc4 shedding resulted in less phosphorylation of ERK upon IL-1β stimulation.

CONCLUSION

Shed Sdc4 might be a good prognostic biomarker for OA mediated cartilage degradation. MMP-9 seems to be the relevant sheddase for Sdc4 under OA conditions, desensitizing chondrocytes towards IL-1 signaling.

Syndecan receptors: pericellular regulators in development and inflammatory disease

The syndecans are the major family of transmembrane proteoglycans, usually bearing multiple heparan sulfate chains. They are present on virtually all nucleated cells of vertebrates and are also present in invertebrates, indicative of a long evolutionary history. Genetic models in both vertebrates and invertebrates have shown that syndecans link to the actin cytoskeleton and can fine-tune cell adhesion, migration, junction formation, polarity and differentiation. Although often associated as co-receptors with other classes of receptors (e.g. integrins, growth factor and morphogen receptors), syndecans can nonetheless signal to the cytoplasm in discrete ways. Syndecan expression levels are upregulated in development, tissue repair and an array of human diseases, which has led to the increased appreciation that they may be important in pathogenesis not only as diagnostic or prognostic agents, but also as potential targets. Here, their functions in development and inflammatory diseases are summarized, including their potential roles as conduits for viral pathogen entry into cells.

Syndecans in cancer: A review of function, expression, prognostic value, and therapeutic significance

While our understanding of tumors and how to treat them has advanced significantly since the days of Aminopterin and the radical mastectomy, cancer remains among the leading causes of death worldwide. Despite innumerable advancements in medical technology the non-static and highly heterogeneous nature of a tumor can make characterization and treatment exceedingly difficult. Because of this complexity, the identification of new cellular constituents that can be used for diagnostic, prognostic, and therapeutic purposes is crucial in improving patient outcomes worldwide. Growing evidence has demonstrated that among the myriad of changes seen in cancer cells, the Syndecan family of proteins has been observed to undergo drastic alterations in expression. Syndecans are transmembrane heparan sulfate proteoglycans that are responsible for cell signaling, proliferation, and adhesion, and many studies have shed light on their unique involvement in both tumor progression and suppression. This review seeks to discuss Syndecan expression levels in various cancers, whether they make reliable biomarkers for detection and prognosis, and whether they may be viable targets for future cancer therapies. The conclusions drawn from the literature reviewed in this article indicate that changes in expression of Syndecan protein can have profound effects on tumor size, metastatic capability, and overall patient survival rate. Further, while data regarding the therapeutic targeting of Syndecan proteins is sparse, the available literature does demonstrate promise for their use in cancer treatment going forward.

Hypoxia Promotes Syndecan-3 Expression in the Tumor Microenvironment

The syndecan (Sdc) family is comprised of four members of cell surface molecules (Sdc-1 to 4) with different biological functions. Syndecan-3 (Sdc-3) is known to be mainly expressed in the brain and nervous tissue and plays a key role in development, cell adhesion, and migration. Recent studies point to important roles for Sdc-3 in inflammatory disease, but the patterns of expression and significance of Sdc-3 in cancer remains unexplored. Here we show that Sdc-3 expression is upregulated on several cancer types, especially in solid tumors that are known to be hypoxic. The Cancer Genome Atlas program (TCGA) data demonstrated that Sdc-3 expression in the tumor microenvironment positively correlates with a hypoxia gene signature. To confirm a potential cause-effect, we performed experiments with tumor cell lines showing increased expression upon in vitro exposure to 1% oxygen or dimethyloxalylglycine, an inhibitor of prolyl hydroxylases, indicating that Sdc-3 expression is promoted by hypoxia inducible factors (HIFs). HIF-1α was responsible for this upregulation as confirmed by CRISPR-engineered tumor cells. Using single-cell RNA sequencing data of melanoma patients, we show that Sdc-3 is expressed on tumor associated macrophages, cancer cells, and endothelial cells. Syndecan-3 expression positively correlated with a macrophage gene signature across several TCGA cancer types. In vitro experiments demonstrated that hypoxia (1% oxygen) or treatment with IFN-γ stimulate Sdc-3 expression on RAW-264.7 derived macrophages, linking Sdc-3 expression to a proinflammatory response. Syndecan-3 expression correlates with a better patient overall survival in hypoxic melanoma tumors.

Heparan Sulfate Proteoglycan Signaling in Tumor Microenvironment

In the last few decades, heparan sulfate (HS) proteoglycans (HSPGs) have been an intriguing subject of study for their complex structural characteristics, their finely regulated biosynthetic machinery, and the wide range of functions they perform in living organisms from development to adulthood. From these studies, key roles of HSPGs in tumor initiation and progression have emerged, so that they are currently being explored as potential biomarkers and therapeutic targets for cancers. The multifaceted nature of HSPG structure/activity translates in their capacity to act either as inhibitors or promoters of tumor growth and invasion depending on the tumor type. Deregulation of HSPGs resulting in malignancy may be due to either their abnormal expression levels or changes in their structure and functions as a result of the altered activity of their biosynthetic or remodeling enzymes. Indeed, in the tumor microenvironment, HSPGs undergo structural alterations, through the shedding of proteoglycan ectodomain from the cell surface or the fragmentation and/or desulfation of HS chains, affecting HSPG function with significant impact on the molecular interactions between cancer cells and their microenvironment, and tumor cell behavior. Here, we overview the structural and functional features of HSPGs and their signaling in the tumor environment which contributes to tumorigenesis and cancer progression.

Antibody-mediated inhibition of syndecan-4 dimerisation reduces interleukin (IL)-1 receptor trafficking and signalling

OBJECTIVE

Syndecan-4 (sdc4) is a cell-anchored proteoglycan that consists of a transmembrane core protein and glucosaminoglycan (GAG) side chains. Binding of soluble factors to the GAG chains of sdc4 may result in the dimerisation of sdc4 and the initiation of downstream signalling cascades. However, the question of how sdc4 dimerisation and signalling affects the response of cells to inflammatory stimuli is unknown.

METHODS

Sdc4 immunostaining was performed on rheumatoid arthritis (RA) tissue sections. Interleukin (IL)-1 induced extracellular signal-regulated kinases (ERK) phosphorylation and matrix metalloproteinase-3 production was investigated. Il-1 binding to sdc4 was investigated using immunoprecipitation. IL-1 receptor (IL1R1) staining on wild-type, sdc4 and IL1R1 knockout fibroblasts was performed in fluorescence-activated cell sorting analyses. A blocking sdc4 antibody was used to investigate sdc4 dimerisation, IL1R1 expression and the histological paw destruction in the human tumour necrosis factor-alpha transgenic mouse.

RESULTS

We show that in fibroblasts, the loss of sdc4 or the antibody-mediated inhibition of sdc4 dimerisation reduces the cell surface expression of the IL-1R and regulates the sensitivity of fibroblasts to IL-1. We demonstrate that IL-1 directly binds to sdc4 and in an IL-1R-independent manner leads to its dimerisation. IL-1-induced dimerisation of sdc4 regulates caveolin vesicle-mediated trafficking of the IL1R1, which in turn determines the responsiveness to IL-1. Administration of antibodies (Ab) against the dimerisation domain of sdc4, thus, strongly reduces the expression IL1R1 on arthritic fibroblasts both in vitro and an animal model of human RA.

CONCLUSION

Collectively, our data suggest that Ab that specifically inhibit sdc4 dimerisation may support anti-IL-1 strategies in diseases such as inflammatory arthritis.

The Emerging Role of Vitamin C as a Treatment for Sepsis

Sepsis, a life-threatening organ dysfunction due to a dysregulated host response to infection, is a leading cause of morbidity and mortality worldwide. Decades of research have failed to identify any specific therapeutic targets outside of antibiotics, infectious source elimination, and supportive care. More recently, vitamin C has emerged as a potential therapeutic agent to treat sepsis. Vitamin C has been shown to be deficient in septic patients and the administration of high dose intravenous as opposed to oral vitamin C leads to markedly improved and elevated serum levels. Its physiologic role in sepsis includes attenuating oxidative stress and inflammation, improving vasopressor synthesis, enhancing immune cell function, improving endovascular function, and epigenetic immunologic modifications. Multiple clinical trials have demonstrated the safety of vitamin C and two recent studies have shown promising data on mortality improvement. Currently, larger randomized controlled studies are underway to validate these findings. With further study, vitamin C may become standard of care for the treatment of sepsis, but given its safety profile, current treatment can be justified with compassionate use.

Syndecan-3 in Inflammation and Angiogenesis

Syndecans are a four member multifunctional family of cell surface molecules with diverse biological roles. Syndecan-3 (SDC3) is the largest of these, but in comparison to the other family members relatively little is known about this molecule. SDC3 null mice grow and develop normally, all be it with subtle anatomical phenotypes in the brain. Roles for this molecule in both neuronal and brain tissue have been identified, and is associated with altered satiety responses. Recent studies suggest that SDC3 expression is not restricted to neuronal tissues and has important roles in inflammatory disorders such as rheumatoid arthritis, disease associated processes such as angiogenesis and in the facilitation of infection of dendritic cells by HIV. The purpose of this review article is to explore these new biological insights into SDC3 functions in inflammatory disease.