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.

Low expression of ZFP36L1 in osteosarcoma promotes lung metastasis by inhibiting the SDC4-TGF-ß signaling feedback loop.

ZFP36L1, which is a negative regulator of gene transcripts, has been proven to regulate the progression of several carcinomas. However, its role in sarcoma remains unknown. Here, by using data analyses and in vivo experiments, we found that ZFP36L1 inhibited the lung metastasis of osteosarcoma (OS). Knockdown of ZFP36L1 promoted OS cell migration by activating TGF-ß signaling and increasing SDC4 expression. Intriguingly, we observed a positive feedback loop between SDC4 and TGF-ß signaling. SDC4 protected TGFBR3 from matrix metalloproteinase (MMP)-mediated cleavage and therefore relieved the inhibition of TGF-ß signaling by soluble TGFBR3, while TGF-ß signaling positively regulated SDC4 transcription. We also proved that ZFP36L1 regulated SDC4 mRNA decay through adenylate-uridylate (AU)-rich elements (AREs) in its 3'UTR. Furthermore, treatment with SB431542 (a TGF-ß receptor kinase inhibitor) and MK2 inhibitor III (a MAPKAPK2 inhibitor that increases the ability of ZFP36L1 to degrade mRNA) dramatically inhibited OS lung metastasis, suggesting a promising therapeutic approach for the treatment of OS lung metastasis.

Soluble vascular endothelial glycocalyx proteoglycans as potential therapeutic targets in inflammatory diseases.

Reducing the activity of cytokines and leukocyte extravasation is an emerging therapeutic strategy to limit tissue-damaging inflammatory responses and restore immune homeostasis in inflammatory diseases. Proteoglycans embedded in the vascular endothelial glycocalyx, which regulate the activity of cytokines to restrict the inflammatory response in physiological conditions, are proteolytically cleaved in inflammatory diseases. Here we critically review the potential of proteolytically shed, soluble vascular endothelial glycocalyx proteoglycans to modulate pathological inflammatory responses. Soluble forms of the proteoglycans syndecan-1, syndecan-3 and biglycan exert beneficial anti-inflammatory effects by the removal of chemokines, suppression of proinflammatory cytokine expression and leukocyte migration, and induction of autophagy of proinflammatory M1 macrophages. By contrast, soluble versikine and decorin enhance proinflammatory responses by increasing inflammatory cytokine synthesis and leukocyte migration. Endogenous syndecan-2 and mimecan exert proinflammatory effects, syndecan-4 and perlecan mediate beneficial anti-inflammatory effects and glypican regulates Hh and Wnt signaling pathways involved in systemic inflammatory responses. Taken together, targeting the vascular endothelial glycocalyx-derived, soluble syndecan-1, syndecan-2, syndecan-3, syndecan-4, biglycan, versikine, mimecan, perlecan, glypican and decorin might be a potential therapeutic strategy to suppress overstimulated cytokine and leukocyte responses in inflammatory diseases.

Different effects of crizotinib treatment in two non-small cell lung cancer patients with SDC4::ROS1 fusion variants.

The possibility of stratifying patients according to differences in ROS proto-oncogene 1 (ROS1) fusion partners has been discussed. This study aimed to clarify the clinicopathological differences between two SDC4::ROS1 positive NSCLC cases who had different responses to crizotinib. Cytology and pathology samples from two NSCLC cases with SDC4::ROS1 who were diagnosed and treated with crizotinib at Nihon University Itabashi Hospital were obtained. Case 1 has been well-controlled with crizotinib for over 5 years, but case 2 was worse and overall survival was 19 months. Sequencing analysis of ROS1 fusion genes was performed by reverse-transcription-PCR and Sanger's sequencing methods. In addition, thyroid transcription factor (TTF)-1, ROS-1, Ki67, and phosphorylated extracellular signal-regulated kinase (pERK)1/2 expression were investigated using immunohistochemistry. Sequencing analysis showed SDC4 exon2::ROS1 exon 32 (exon33 deleted) in case 1, and coexistence of SDC4 exon2::ROS1 exon 34 and SDC4 exon2::ROS1 exon35 in case 2. The Ki67 index was not different, but ROS1 and pERK1/2 expression levels tended to be higher in the tumor cells of case 2 than in case 1. Therapeutic response to crizotinib and patients' prognosis in ROS1 rearranged NSCLC may be related to the activation of ROS1 signaling, depending on ROS1 and pERK1/2 overexpression status, even if the ROS1 fusion partner is the same.

Systemically administered wound-homing peptide accelerates wound healing by modulating syndecan-4 function.

CAR (CARSKNKDC) is a wound-homing peptide that recognises angiogenic neovessels. Here we discover that systemically administered CAR peptide has inherent ability to promote wound healing: wounds close and re-epithelialise faster in CAR-treated male mice. CAR promotes keratinocyte migration in vitro. The heparan sulfate proteoglycan syndecan-4 regulates cell migration and is crucial for wound healing. We report that syndecan-4 expression is restricted to epidermis and blood vessels in mice skin wounds. Syndecan-4 regulates binding and internalisation of CAR peptide and CAR-mediated cytoskeletal remodelling. CAR induces syndecan-4-dependent activation of the small GTPase ARF6, via the guanine nucleotide exchange factor cytohesin-2, and promotes syndecan-4-, ARF6- and Cytohesin-2-mediated keratinocyte migration. Finally, we show that genetic ablation of syndecan-4 in male mice eliminates CAR-induced wound re-epithelialisation following systemic administration. We propose that CAR peptide activates syndecan-4 functions to selectively promote re-epithelialisation. Thus, CAR peptide provides a therapeutic approach to enhance wound healing in mice; systemic, yet target organ- and cell-specific.

NMR Structural Study of Syndecan-4 Transmembrane Domain with Cytoplasmic Region.

Syndecan-4 (SDC4) consists of transmembrane heparan sulfate proteoglycan (HSPG) belonging to the syndecan family. It is present in most cell types of Mammalia. Its structure contains a heparan-sulfate-modified extracellular domain, a single transmembrane domain, and a short C-terminal cytoplasmic domain. Regarding the overall cellular function of SDC4, other cells or ligands can bind to its ecto-domain. In addition, 4,5-bisphosphate phosphatidylinositol (PIP2) or protein kinase Cα can bind to its cyto-domain to activate downstream signaling pathways. To understand the signal transduction mechanism of syndecan, it is important to know the interactions between their actual structure and function in vivo. Therefore, it is important to identify the structure of SDC4 to understand the ligand binding behavior of SDC4. In this study, expression and purification were performed to reveal structures of the short ecto-domain, the transmembrane domain, and the cytoplasmic domain of Syd4-eTC (SDC4). Solution-state NMR spectroscopy and solid-state NMR spectroscopy were used to study the structure of Syd4-eTC in membrane environments and to demonstrate the interaction between Syd4-eTC and PIP2.

Syndecan-4 proteoliposomes enhance revascularization in a rabbit hind limb ischemia model of peripheral ischemia.

Regenerative therapeutics for treating peripheral arterial disease are an appealing strategy for creating more durable solutions for limb ischemia. In this work, we performed preclinical testing of an injectable formulation of syndecan-4 proteoliposomes combined with growth factors as treatment for peripheral ischemia delivered in an alginate hydrogel. We tested this therapy in an advanced model of hindlimb ischemia in rabbits with diabetes and hyperlipidemia. Our studies demonstrate enhancement in vascularity and new blood vessel growth with treatment with syndecan-4 proteoliposomes in combination with FGF-2 or FGF-2/PDGF-BB. The effects of the treatments were particularly effective in enhancing vascularity in the lower limb with a 2-4 increase in blood vessels in the treatment group in comparison to the control group. In addition, we demonstrate that the syndecan-4 proteoliposomes have stability for at least 28 days when stored at 4°C to allow transport and use in the hospital environment. In addition, we performed toxicity studies in the mice and found no toxic effects even when injected at high concentration. Overall, our studies support that syndecan-4 proteoliposomes markedly enhance the therapeutic potential of growth factors in the context of disease and may be promising therapeutics for inducing vascular regeneration in peripheral ischemia. STATEMENT OF SIGNIFICANCE: Peripheral ischemia is a common condition in which there is a lack of blood flow to the lower limbs. This condition can lead to pain while walking and, in severe cases, critical limb ischemia and limb loss. In this study, we demonstrate the safety and efficacy of a novel injectable therapy for enhancing revascularization in peripheral ischemia using an advanced large animal model of peripheral vascular disease using rabbits with hyperlipidemia and diabetes.

Engineered Biomimetic Fibrillar Fibronectin Matrices Regulate Cell Adhesion Initiation, Migration, and Proliferation via α5ß1 Integrin and Syndecan-4 Crosstalk.

Cells regulate adhesion to the fibrillar extracellular matrix (ECM) of which fibronectin is an essential component. However, most studies characterize cell adhesion to globular fibronectin substrates at time scales long after cells polarize and migrate. To overcome this limitation, a simple and scalable method to engineer biomimetic 3D fibrillar fibronectin matrices is introduced and how they are sensed by fibroblasts from the onset of attachment is characterized. Compared to globular fibronectin substrates, fibroblasts accelerate adhesion initiation and strengthening within seconds to fibrillar fibronectin matrices via α5ß1 integrin and syndecan-4. This regulation, which additionally accelerates on stiffened fibrillar matrices, involves actin polymerization, actomyosin contraction, and the cytoplasmic proteins paxillin, focal adhesion kinase, and phosphoinositide 3-kinase. Furthermore, this immediate sensing and adhesion of fibroblast to fibrillar fibronectin guides migration speed, persistency, and proliferation range from hours to weeks. The findings highlight that fibrillar fibronectin matrices, compared to widely-used globular fibronectin, trigger short- and long-term cell decisions very differently and urge the use of such matrices to better understand in vivo interactions of cells and ECMs. The engineered fibronectin matrices, which can be printed onto non-biological surfaces without loss of function, open avenues for various cell biological, tissue engineering and medical applications.

Syndecan-4 is a maestro of gastric cancer cell invasion and communication that underscores poor survival.

Gastric cancer is a dominating cause of cancer-associated mortality with limited therapeutic options. Here, we show that syndecan-4 (SDC4), a transmembrane proteoglycan, is highly expressed in intestinal subtype gastric tumors and that this signature associates with patient poor survival. Further, we mechanistically demonstrate that SDC4 is a master regulator of gastric cancer cell motility and invasion. We also find that SDC4 decorated with heparan sulfate is efficiently sorted in extracellular vesicles (EVs). Interestingly, SDC4 in EVs regulates gastric cancer cell-derived EV organ distribution, uptake, and functional effects in recipient cells. Specifically, we show that SDC4 knockout disrupts the tropism of EVs for the common gastric cancer metastatic sites. Our findings set the basis for the molecular implications of SDC4 expression in gastric cancer cells and provide broader perspectives on the development of therapeutic strategies targeting the glycan-EV axis to limit tumor progression.

Secreted phospholipase A2 XIIA triggers a mitochondrial damage-induced senescence in chronic obstructive pulmonary disease fibroblasts.

RATIONALE: Lung fibroblast senescence is involved in the pathophysiology of chronic obstructive pulmonary disease (COPD). However, the mechanisms underlining this phenomenon are still poorly understood. Secreted phospholipases (sPLA2, a subclass of phospholipases) are secreted by senescent cells and can in turn induce senescence. However, their role in fibroblasts senescence in COPD is unknown. OBJECTIVES: The aim of this study was to analyze the role of sPLA2 in pulmonary fibroblast senescence. METHODS: Fibroblasts were isolated from patients with COPD and control subjects, and senescence markers and inflammatory profile was analyzed. sPLA2 levels were quantified in serum of COPD and controls. MAIN RESULTS: In comparison with non-smokers and smoker controls, senescent lung COPD fibroblasts exhibited a higher mRNA and protein expression of the sPLA2 isoform XIIA and of syndecan 4 (one of its receptors). sPLA2 XIIA induced in turn senescence of non-senescent pulmonary fibroblasts via a pathway involving consecutively syndecan 4, activation of MAPK and p-serine 727 STAT-3, increased mitochondrial ROS production, and activation of AMPK/p53. This pathway was associated with a specific inflammatory secretome (IL-10, IL-12 and TNFα), globally suggesting occurrence of a mitochondrial damage-induced senescence. COPD fibroblasts were more susceptible to this sPLA2 XIIA effect than cells from controls subjects. sPLA2 XIIA levels were significantly higher in serum from COPD patients as compared to controls. CONCLUSION: sPLA2 XIIA is involved in senescence in COPD and could be a potential target to dampen this process.

Unravelling the Effects of Syndecan-4 Knockdown on Skeletal Muscle Functions.

The remodelling of the extracellular matrix plays an important role in skeletal muscle development and regeneration. Syndecan-4 is a cell surface proteoglycan crucial for muscle differentiation. Syndecan-4-/- mice have been reported to be unable to regenerate following muscle damage. To investigate the consequences of the decreased expression of Syndecan-4, we have studied the in vivo and in vitro muscle performance and the excitation-contraction coupling machinery in young and aged Syndecan-4+/- (SDC4) mice. In vivo grip force was decreased significantly as well as the average and maximal speed of voluntary running in SDC4 mice, regardless of their age. The maximal in vitro twitch force was reduced in both EDL and soleus muscles from young and aged SDC4 mice. Ca2+ release from the sarcoplasmic reticulum decreased significantly in the FDB fibres of young SDC4 mice, while its voltage dependence was unchanged regardless of age. These findings were present in muscles from young and aged mice as well. On C2C12 murine skeletal muscle cells, we have also found altered calcium homeostasis upon Syndecan-4 silencing. The decreased expression of Syndecan-4 leads to reduced skeletal muscle performance in mice and altered motility in C2C12 myoblasts via altered calcium homeostasis. The altered muscle force performance develops at an early age and is maintained throughout the life course of the animal until old age.

Syndecan-4 Mediates the Cellular Entry of Adeno-Associated Virus 9.

Due to their low pathogenicity, immunogenicity, and long-term gene expression, adeno-associated virus (AAV) vectors emerged as safe and efficient gene delivery tools, over-coming setbacks experienced with other viral gene delivery systems in early gene therapy trials. Among AAVs, AAV9 can translocate through the blood-brain barrier (BBB), making it a promising gene delivery tool for transducing the central nervous system (CNS) via systemic administration. Recent reports on the shortcomings of AAV9-mediated gene delivery into the CNS require reviewing the molecular base of AAV9 cellular biology. A more detailed understanding of AAV9's cellular entry would eradicate current hurdles and enable more efficient AAV9-based gene therapy approaches. Syndecans, the transmembrane family of heparan-sulfate proteoglycans, facilitate the cellular uptake of various viruses and drug delivery systems. Utilizing human cell lines and syndecan-specific cellular assays, we assessed the involvement of syndecans in AAV9's cellular entry. The ubiquitously expressed isoform, syndecan-4 proved its superiority in facilitating AAV9 internalization among syndecans. Introducing syndecan-4 into poorly transducible cell lines enabled robust AAV9-dependent gene transduction, while its knockdown reduced AAV9's cellular entry. Attachment of AAV9 to syndecan-4 is mediated not just by the polyanionic heparan-sulfate chains but also by the cell-binding domain of the extracellular syndecan-4 core protein. Co-immunoprecipitation assays and affinity proteomics also confirmed the role of syndecan-4 in the cellular entry of AAV9. Overall, our findings highlight the universally expressed syndecan-4 as a significant contributor to the cellular internalization of AAV9 and provide a molecular-based, rational explanation for the low gene delivery potential of AAV9 into the CNS.

Differential effects of temperature and mTOR and Wnt-planar cell polarity pathways on syndecan-4 and CD44 expression in growth-selected turkey satellite cell populations.

Satellite cells (SCs) comprise a heterogeneous population of muscle stem cells. Thermal stress during the first week after hatch alters proliferation, myogenesis, and adipogenesis of SCs of turkey pectoralis major (p. major) muscle via mechanistic target of rapamycin (mTOR) and wingless-type mouse mammary tumor virus integration site family/planar cell polarity (Wnt/PCP) pathways. Pivotal genes in mTOR and Wnt/PCP pathways are mTOR and frizzled-7 (Fzd7), respectively. The objective of this study was to determine the differential effects of thermal stress on SDC4 and CD44 expression in turkey p. major muscle SCs and how the expression of SDC4 and CD44 is modulated by the mTOR and Wnt/PCP pathways. Satellite cells were isolated from the p. major muscle of 1-week-old faster-growing modern-commercial (NC) turkeys and slower-growing historic Randombred Control Line 2 (RBC2) turkeys, and were challenged with hot (43°C) and cold (33°C) thermal stress for 72 h of proliferation followed by 48 h of differentiation. The NC line SCs were found to contain a lower proportion of SDC4 positive and CD44 negative (SDC4+CD44-) cells and a greater proportion of SDC4 negative and CD44 positive (SDC4-CD44+) cells compared to the RBC2 line at the control temperature (38°C) at both 72 h of proliferation and 48 h of differentiation. In general, at 72 h of proliferation, the proportion of SDC4+CD44- cells decreased with heat stress (43°C) and increased with cold stress (33°C) relative to the control temperature (38°C) in both lines, whereas the proportion of SDC4-CD44+ cells increased with heat stress and decreased with cold stress. In general, the expression of SDC4 and CD44 in the NC SCs showed greater response to both hot and cold thermal stress compared to the RBC2 cells. Knockdown of mTOR or Fzd7 expression increased the proportion of SDC4+CD44- cells while the proportion of SDC4-CD44+ cells decreased during differentiation with line differences being specific to treatment temperatures. Thus, differential composition of p. major muscle SCs in growth-selected commercial turkey may be resulted, in part, from the alteration in SDC4 and CD44 expression. Results indicate differential temperature sensitivity and mTOR and Wnt/PCP pathway responses of growth-selected SC populations and this may have long-lasting effect on muscle development and growth.

SDC4-rs1981429 and ATM-rs228590 may provide early biomarkers of breast cancer risk.

In Australia, 13% of women are diagnosed with breast cancer (BC) in their lifetime with approximately 20,000 women diagnosed with the disease in 2021. BC is characterised by complex histological and genomic influences with recent advances in cancer biology improving early diagnosis and personalised treatment interventions. The Phosphatidyl-inositol-3-kinase/Protein kinase B (PI3K/AKT) pathway is essential in apoptosis resistance, cell survival, activation of cellular responses to DNA damage and DNA repair. Heparan sulfate proteoglycans (HSPGs) are ubiquitous molecules found on the cell surface and in the extracellular matrix with essential functions in regulating cell survival, growth, adhesion and as mediators of cell differentiation and migration. HSPGs, particularly the syndecans (SDCs), have been linked to cancers, making them an exciting target for anticancer treatments. In the PI3K/AKT pathway, syndecan-4 (SDC4) has been shown to downregulate AKT Serine/Threonine Kinase (AKT1) gene expression, while the ATM Serine/Threonine Kinase (ATM) gene has been found to inhibit this pathway upstream of AKT. We investigated single-nucleotide polymorphisms (SNPs) in HSPG and related genes SDC4, AKT1 and ATM and their influence on the prevalence of BC. SNPs were genotyped in the Australian Caucasian Genomics Research Centre Breast Cancer (GRC-BC) population and in the Griffith University-Cancer Council Queensland Breast Cancer Biobank (GU-CCQ BB) population. We identified that SDC4-rs1981429 and ATM-rs228590 may influence the development and progression of BC, having the potential to become biomarkers in early BC diagnosis and personalised treatment.

Syndecan-4 and stromal cell-derived factor-1 alpha functionalized endovascular scaffold facilitates adhesion, spreading and differentiation of endothelial colony forming cells and functions under flow and shear stress conditions.

Acellular vascular scaffolds with capture molecules have shown great promise in recruiting circulating endothelial colony forming cells (ECFCs) to promote in vivo endothelialization. A microenvironment conducive to cell spreading and differentiation following initial cell capture are key to the eventual formation of a functional endothelium. In this study, syndecan-4 and stromal cell-derived factor-1 alpha were used to functionalize an elastomeric biomaterial composed of poly(glycerol sebacate), Silk Fibroin and Type I Collagen, termed PFC, to enhance ECFC-material interaction. Functionalized PFC (fPFC) showed significantly greater ECFCs capture capability under physiological flow. Individual cell spreading area on fPFC (1474 ± 63 µm2 ) was significantly greater than on PFC (1187 ± 54 µm2 ) as early as 2 h, indicating enhanced cell-material interaction. Moreover, fPFC significantly upregulated the expression of endothelial cell specific markers such as platelet endothelial cell adhesion molecule (24-fold) and Von Willebrand Factor (11-fold) compared with tissue culture plastic after 7 days, demonstrating differentiation of ECFCs into endothelial cells. fPFC fabricated as small diameter conduits and tested using a pulsatile blood flow bioreactor were stable and maintained function. The findings suggest that the new surface functionalization strategy proposed here results in an endovascular material with enhanced endothelialization.

Syndecan-4 regulates the HER2-positive breast cancer cell proliferation cells via CK19/AKT signalling.

Despite the use of the highly specific anti-HER2 receptor (trastuzumab) therapy, HER2-positive breast cancers account for 20-30% of all breast cancer carcinomas, with HER2 status a challenge to treatment interventions. The heparan sulfate proteoglycans (HSPGs) are prominently expressed in the extracellular matrix (ECM), mediate breast cancer proliferation, development, and metastasis with most studies to date conducted in animal models. This study examined HSPGs in HER2-positive human breast cancer cell lines and their contribution to cancer cell proliferation. The study examined the cells following enhancement (via the addition of heparin) and knockdown (KD; using short interfering RNA, siRNA) of HSPG core proteins. The interaction of HSPG core proteins and AKT signalling molecules was examined to identify any influence of this signalling pathway on cancer cell proliferation. Our findings illustrated the HSPG syndecan-4 (SDC4) core protein significantly regulates cell proliferation with increased BC cell proliferation following heparin addition to cultures and decreased cell number following SDC4 KD. In addition, along with SDC4, significant changes in CK19/AKT signalling were identified as mediators of BC HER2-positive BC cell proliferation. This study provides evidence for a cell growth regulatory axis involving HSPGs/CK19 and AKT that represents a potential molecular target to prevent proliferation of HER2-positive breast cancer cells.

SDC4-rs1981429, ATM-rs228590 and biomarkers of breast cancer risk.

This is a correspondence on published article on SDC4-rs1981429, ATM-rs228590 and biomarkers of breast cancer risk. Confounding factors are discussed.

Cholesterol-induced LRP3 downregulation promotes cartilage degeneration in osteoarthritis by targeting Syndecan-4.

Emerging evidence suggests that osteoarthritis is associated with high cholesterol levels in some osteoarthritis patients. However, the specific mechanism under this metabolic osteoarthritis phenotype remains unclear. We find that cholesterol metabolism-related gene, LRP3 (low-density lipoprotein receptor-related protein 3) is significantly reduced in high-cholesterol diet mouse's cartilage. By using Lrp3-/- mice in vivo and LRP3 lentiviral-transduced chondrocytes in vitro, we identify that LRP3 positively regulate chondrocyte extracellular matrix metabolism, and its deficiency aggravate the degeneration of cartilage. Regardless of diet, LRP3 overexpression in cartilage attenuate anterior cruciate ligament transection induced osteoarthritis progression in rats and Lrp3 knockout-induced osteoarthritis progression in mice. LRP3 knockdown upregulate syndecan-4 by activating the Ras signaling pathway. We identify syndecan-4 as a downstream molecular target of LRP3 in osteoarthritis pathogenesis. These findings suggest that cholesterol-LRP3- syndecan-4 axis plays critical roles in osteoarthritis development, and LRP3 gene therapy may provide a therapeutic regimen for osteoarthritis treatment.

High expression of syndecan-4 is related to clinicopathological features and poor prognosis of pancreatic adenocarcinoma.

OBJECTIVE: Pancreatic adenocarcinoma (PAAD) is a leading cause of cancer-related mortality in adults. Syndecan-4 (SDC4) is involved in cancer pathogenesis. Therefore, this study aimed to explore the expression and clinical significance of SDC4 in PAAD. METHODS: Differentially expressed genes (DEGs) between PAAD and normal pancreas were screened from the GTEx and TCGA databases, and the correlationship between the DEGs and prognosis were analyzed. The prognostic value of the screened SDC4, SERPINE1, and SLC2A1 was evaluated using the Kaplan-Meier curve and SDC4 was subsequently selected as the better candidate. Also, SDC4 expression was analyzed in PAAD tissues, the other risk factors affecting postoperative survival were analyzed using Cox regression analysis, and SDC4-mediated pathways enrichment was identified by GSVA and GSEA. SDC4 expression in PAAD tissues and adjacent normal tissues of selected PAAD patients was detected by RT-qPCR and immunohistochemistry. The correlation between SDC4 and clinical features was evaluated by the χ2 test. RESULTS: SDC4 was highly expressed in PAAD tissues. Elevated SDC4 was correlated with reduced overall survival. SDC4 enrichment pathways included spliceosome function, proteasome activity, pentose phosphate pathway, base excision repair, mismatch repair, DNA replication, oxidative phosphorylation, mitotic spindle formation, epithelial-mesenchymal transition, and G2M checkpoints. SDC4 was elevated in PAAD tissues of PAAD patients compared with adjacent normal tissues. High SDC4 expression was related to metastatic differentiation, TNM stage, lymphatic metastasis, and lower 3-year survival rate. SDC4 was an independent risk factor affecting postoperative survival. CONCLUSION: SDC4 was highly expressed in PAAD and was related to clinicopathological features and poor prognosis, which might be an important index for PAAD early diagnosis and prognosis.

Cardiomyocyte-specific overexpression of syndecan-4 in mice results in activation of calcineurin-NFAT signalling and exacerbated cardiac hypertrophy.

BACKGROUND: Cardiomyocyte hypertrophy is a hallmark of cardiac dysfunction in patients with aortic stenosis (AS), and can be triggered by left ventricular (LV) pressure overload in mice by aortic banding (AB). Syndecan-4 is a transmembrane heparan sulphate proteoglycan which is found increased in the myocardium of AS patients and AB mice. The role of syndecan-4 in cardiomyocyte hypertrophy is not well understood. PURPOSE OF THE STUDY: We developed mice with cardiomyocyte-specific overexpression of syndecan-4 (Sdc4-Tg) and subjected these to AB to examine the role of syndecan-4 in hypertrophy and activation of the pro-hypertrophic calcineurin-NFAT signalling pathway. METHODS AND RESULTS: Sdc4-Tg mice showed exacerbated cardiac remodelling upon AB compared to wild type (WT). At 2-6 weeks post-AB, Sdc4-Tg and WT mice showed similar hypertrophic growth, while at 20 weeks post-AB, exacerbated hypertrophy and dysfunction were evident in Sdc4-Tg mice. After cross-breeding of Sdc4-Tg mice with NFAT-luciferase reporter mice, we found increased NFAT activation in Sdc4-Tg hearts after AB. Immunoprecipitation showed that calcineurin bound to syndecan-4 in Sdc4-Tg hearts. Isolated cardiomyocytes from Sdc4-Tg mice showed alterations in Ca2+ fluxes, suggesting that syndecan-4 regulated Ca2+ levels, and thereby, activating the syndecan-4-calcineurin complex resulting in NFAT activation and hypertrophic growth. Similarly, primary cardiomyocyte cultures from neonatal rats showed increased calcineurin-NFAT-dependent hypertrophic growth upon viral Sdc4 overexpression. CONCLUSION: Our study of mice with cardiomyocyte-specific overexpression of Sdc4 have revealed that syndecan-4 is important for activation of the Ca2+-dependent calcineurin-NFAT signalling pathway, hypertrophic remodelling and dysfunction in cardiomyocytes in response to pressure overload.