Endothelial heparan sulfate 6-O-sulfation levels regulate angiogenic responses of endothelial cells to fibroblast growth factor 2 and vascular endothelial growth factor

Overview of the current procedures in synthesis of heparin saccharides

Natural heparin, a glycosaminoglycan consisting of repeating hexuronic acid and glucosamine linked by 1 → 4 glycosidic bonds, is the most widely used anticoagulant. To subvert the dependence on animal sourced heparin, alternative methods to produce heparin saccharides, i.e., either heterogenous sugar chains similar to natural heparin, or structurally defined oligosaccharides, are becoming hot subjects. Although the success by chemical synthesis of the pentasaccharide, fondaparinux, encourages to proceed through a chemical approach generating homogenous product, synthesizing larger oligos is still cumbersome and beyond reach so far. Alternatively, the chemoenzymatic pathway exhibited exquisite stereoselectivity of glycosylation and regioselectivity of modification, with the advantage to skip the tedious protection steps unavoidable in chemical synthesis. However, to a scale of drug production needed today is still not in sight. In comparison, a procedure of de novo biosynthesis in an organism could be an ultimate goal. The main purpose of this review is to summarize the current available/developing strategies and techniques, which is expected to provide a comprehensive picture for production of heparin saccharides to replenish or eventually to replace the animal derived products. In chemical and chemoenzymatic approaches, the methodologies are discussed according to the synthesis procedures: building block preparation, chain elongation, and backbone modification.

Unique structural characteristics and biological activities of heparan sulfate isolated from the mantle of the scallop Chlamys farreri

Marine animals are a huge resource of various glycosaminoglycans (GAGs) with specific structures and functions. A large number of byproducts, such as low-edible mantle, are produced during the processing of Chlamys farreri, which is one of the most cultured scallops in China. In this study, a major GAG component was isolated from the mantle of C. farreri, and its structural characteristics and biological activities were determined in detail. Preliminary analysis by agarose electrophoresis combined with specific enzymatic degradation evaluations showed that this component was heparan sulfate and was named CMHS. Further analysis by HPLC and NMR revealed that CMHS has an average molecular weight of 35.9 kDa and contains a high proportion (80%) of 6-O-sulfated N-acetyl-D-glucosamine/N-sulfated-D-glucosamine (6-O-sulfated GlcNAc/GlcNS) residues and rare 3-O-sulfated β-D-glucuronic acid residues. Bioactivity analysis showed that CMHS has much lower anticoagulant activity than heparin and it can interact with various growth factors with high affinity. Moreover, CMHS binds strongly to the morphogen Wnt 3a to inhibit glypican-3-stimulated Wnt 3a signaling. Thus, the identification of CMHS with unique structural and bioactive features will provide a promising candidate for the development of GAG-type pharmaceutical products and promote the high-value utilization of C. farreri mantle.

Validation of Recombinant Heparan Sulphate Reagents for CNS Repair

Therapies that target the multicellular pathology of central nervous system (CNS) disease/injury are urgently required. Modified non-anticoagulant heparins mimic the heparan sulphate (HS) glycan family and have been proposed as therapeutics for CNS repair since they are effective regulators of numerous cellular processes. Our in vitro studies have demonstrated that low-sulphated modified heparan sulphate mimetics (LS-mHeps) drive CNS repair. However, LS-mHeps are derived from pharmaceutical heparin purified from pig intestines, in a supply chain at risk of shortages and contamination. Alternatively, cellular synthesis of heparin and HS can be achieved using mammalian cell multiplex genome engineering, providing an alternative source of recombinant HS mimetics (rHS). TEGA Therapeutics (San Diego) have manufactured rHS reagents with varying degrees of sulphation and we have validated their ability to promote repair in vitro using models that mimic CNS injury, making comparisons to LS-mHep7, a previous lead compound. We have shown that like LS-mHep7, low-sulphated rHS compounds promote remyelination and reduce features of astrocytosis, and in contrast, highly sulphated rHS drive neurite outgrowth. Cellular production of heparin mimetics may, therefore, offer potential clinical benefits for CNS repair.

Reproducing extracellular matrix adverse remodelling of non-ST myocardial infarction in a large animal model

The rising incidence of non-ST-segment elevation myocardial infarction (NSTEMI) and associated long-term high mortality constitutes an urgent clinical issue. Unfortunately, the study of possible interventions to treat this pathology lacks a reproducible pre-clinical model. Indeed, currently adopted small and large animal models of MI mimic only full-thickness, ST-segment-elevation (STEMI) infarcts, and hence cater only for an investigation into therapeutics and interventions directed at this subset of MI. Thus, we develop an ovine model of NSTEMI by ligating the myocardial muscle at precise intervals parallel to the left anterior descending coronary artery. Upon histological and functional investigation to validate the proposed model and comparison with STEMI full ligation model, RNA-seq and proteomics show the distinctive features of post-NSTEMI tissue remodelling. Transcriptome and proteome-derived pathway analyses at acute (7 days) and late (28 days) post-NSTEMI pinpoint specific alterations in cardiac post-ischaemic extracellular matrix. Together with the rise of well-known markers of inflammation and fibrosis, NSTEMI ischaemic regions show distinctive patterns of complex galactosylated and sialylated N-glycans in cellular membranes and extracellular matrix. Identifying such changes in molecular moieties accessible to infusible and intra-myocardial injectable drugs sheds light on developing targeted pharmacological solutions to contrast adverse fibrotic remodelling.

HS, an Ancient Molecular Recognition and Information Storage Glycosaminoglycan, Equips HS-Proteoglycans with Diverse Matrix and Cell-Interactive Properties Operative in Tissue Development and Tissue Function in Health and Disease

Heparan sulfate is a ubiquitous, variably sulfated interactive glycosaminoglycan that consists of repeating disaccharides of glucuronic acid and glucosamine that are subject to a number of modifications (acetylation, de-acetylation, epimerization, sulfation). Variable heparan sulfate chain lengths and sequences within the heparan sulfate chains provide structural diversity generating interactive oligosaccharide binding motifs with a diverse range of extracellular ligands and cellular receptors providing instructional cues over cellular behaviour and tissue homeostasis through the regulation of essential physiological processes in development, health, and disease. heparan sulfate and heparan sulfate-PGs are integral components of the specialized glycocalyx surrounding cells. Heparan sulfate is the most heterogeneous glycosaminoglycan, in terms of its sequence and biosynthetic modifications making it a difficult molecule to fully characterize, multiple ligands also make an elucidation of heparan sulfate functional properties complicated. Spatio-temporal presentation of heparan sulfate sulfate groups is an important functional determinant in tissue development and in cellular control of wound healing and extracellular remodelling in pathological tissues. The regulatory properties of heparan sulfate are mediated via interactions with chemokines, chemokine receptors, growth factors and morphogens in cell proliferation, differentiation, development, tissue remodelling, wound healing, immune regulation, inflammation, and tumour development. A greater understanding of these HS interactive processes will improve therapeutic procedures and prognoses. Advances in glycosaminoglycan synthesis and sequencing, computational analytical carbohydrate algorithms and advanced software for the evaluation of molecular docking of heparan sulfate with its molecular partners are now available. These advanced analytic techniques and artificial intelligence offer predictive capability in the elucidation of heparan sulfate conformational effects on heparan sulfate-ligand interactions significantly aiding heparan sulfate therapeutics development.

Alterations in heparan sulfate proteoglycan synthesis and sulfation and the impact on vascular endothelial function

The glycocalyx attached to the apical surface of vascular endothelial cells is a rich network of proteoglycans, glycosaminoglycans, and glycoproteins with instrumental roles in vascular homeostasis. Given their molecular complexity and ability to interact with the intra- and extracellular environment, heparan sulfate proteoglycans uniquely contribute to the glycocalyx's role in regulating endothelial permeability, mechanosignaling, and ligand recognition by cognate cell surface receptors. Much attention has recently been devoted to the enzymatic shedding of heparan sulfate proteoglycans from the endothelial glycocalyx and its impact on vascular function. However, other molecular modifications to heparan sulfate proteoglycans are possible and may have equal or complementary clinical significance. In this narrative review, we focus on putative mechanisms driving non-proteolytic changes in heparan sulfate proteoglycan expression and alterations in the sulfation of heparan sulfate side chains within the endothelial glycocalyx. We then discuss how these specific changes to the endothelial glycocalyx impact endothelial cell function and highlight therapeutic strategies to target or potentially reverse these pathologic changes.

Heparan Sulfate Biosynthesis and Sulfation Profiles as Modulators of Cancer Signalling and Progression

Heparan Sulfate Proteoglycans (HSPGs) are important cell surface and Extracellular Matrix (ECM) maestros involved in the orchestration of multiple cellular events in physiology and pathology. These glycoconjugates bind to various bioactive proteins via their Heparan Sulfate (HS) chains, but also through the protein backbone, and function as scaffolds for protein-protein interactions, modulating extracellular ligand gradients, cell signalling networks and cell-cell/cell-ECM interactions. The structural features of HS chains, including length and sulfation patterns, are crucial for the biological roles displayed by HSPGs, as these features determine HS chains binding affinities and selectivity. The large HS structural diversity results from a tightly controlled biosynthetic pathway that is differently regulated in different organs, stages of development and pathologies, including cancer. This review addresses the regulatory mechanisms underlying HS biosynthesis, with a particular focus on the catalytic activity of the enzymes responsible for HS glycan sequences and sulfation motifs, namely D-Glucuronyl C5-Epimerase, N- and O-Sulfotransferases. Moreover, we provide insights on the impact of different HS structural epitopes over HSPG-protein interactions and cell signalling, as well as on the effects of deregulated expression of HS modifying enzymes in the development and progression of cancer. Finally, we discuss the clinical potential of HS biosynthetic enzymes as novel targets for therapy, and highlight the importance of developing new HS-based tools for better patients' stratification and cancer treatment.

Endothelial cell-specific reduction of heparan sulfate suppresses glioma growth in mice

PURPOSE

Heparan sulfate (HS) is one of the factors that has been suggested to be associated with angiogenesis and invasion of glioblastoma (GBM), an aggressive and fast-growing brain tumor. However, it remains unclear how HS of endothelial cells is involved in angiogenesis in glioblastoma and its prognosis. Thus, we investigated the effect of endothelial cell HS on GBM development.

METHODS

We generated endothelial cell-specific knockout of Ext1, a gene encoding a glycosyltransferase and essential for HS synthesis, and murine GL261 glioblastoma cells were orthotopically transplanted. Two weeks after transplantation, we examined the tumor progression and underlying mechanisms.

RESULTS

The endothelial cell-specific Ext1 knockout (Ext1 CKO ) mice exhibited reduced HS expression specifically in the vascular endothelium of the brain capillaries compared with the control wild-type (WT) mice. GBM growth was significantly suppressed in Ext1 CKO mice compared with that in WT mice. After GBM transplantation, the survival rate was significantly higher in Ext1 CKO mice than in WT mice. We investigated how the effect of fibroblast growth factor 2 (FGF2), which is known as an angiogenesis-promoting factor, differs between Ext1 CKO and WT mice by using an in vivo Matrigel assay and demonstrated that endothelial cell-specific HS reduction attenuated the effect of FGF2 on angiogenesis.

CONCLUSIONS

HS reduction in the vascular endothelium of the brain suppressed GBM growth and neovascularization in mice.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s12672-021-00444-3.

Flow shear stress controls the initiation of neovascularization via heparan sulfate proteoglycans within a biomimetic microfluidic model

Endothelial cells (ECs) in vivo are subjected to three forms of shear stress induced by luminal blood flow, transendothelial flow and interstitial flow simultaneously. It is controversial that shear stress, especially the component induced by luminal flow, was thought to inhibit the initialization of angiogenesis and trigger arteriogenesis. Here, we combined microfabrication techniques and delicate numerical simulations to reconstruct the initial physiological microenvironment of neovascularization in vitro, where ECs experience high luminal shear stress, physiological transendothelial flow and various vascular endothelial growth factor (VEGF) distributions simultaneously. With the biomimetic microfluidic model, cell alignment and endothelial sprouting assays were carried out. We found that luminal shear stress inhibits endothelial sprouting and tubule formation in a dose-dependent manner. Although a high concentration of VEGF increases EC sprouting, neither a positive nor a negative VEGF gradient additionally affects the degree of sprouting, and luminal shear stress significantly attenuates neovascularization even in the presence of VEGF. Heparinase was used to selectively degrade the heparan sulfate proteoglycan (HSPG) coating on ECs and messenger RNA profiles in ECs were analyzed. It turned out that HSPGs could act as a mechanosensor to sense the change of fluid shear stress, modulate multiple EC gene expressions, and hence affect neovascularization. In summary, distraction from the stabilized state, such as decreased luminal shear stress, increased VEGF and the destructed mechanotransduction of HSPGs would induce the initiation of neovascularization. Our study highlights the key role of the magnitude and forms of shear stress in neovascularization.

Heparan sulfate functions are altered in the osteoarthritic cartilage

BACKGROUND

Heparan sulfate (HS) proteoglycans (PG) may be found at the chondrocyte surface and in the pericellular cartilage matrix, and are involved in cell-cell and cell-matrix interactions. An important function of HS chains is to regulate cell fate through specific interactions with heparin-binding proteins (HBP) modulated by their complex sulfation pattern. Osteoarthritis (OA) is a joint disorder characterized by the degradation of articular cartilaginous extracellular matrix. The aim of this study was to investigate HS structure and functions in osteoarthritic cartilages compared to normal cartilages (controls).

METHODS

Glycosaminoglycans (GAG) were extracted from human macroscopically normal cartilages (controls, n = 7) and (OA cartilages n = 11). HS were isolated and quantified using the DMMB quantification method. Their structure and functions were then compared using respectively a HPLC analysis and HBP binding tests and their phenotypic effects on murine chondrocytes were studied by RQ-PCR. Statistical analyzes were performed using a one-way ANOVA followed by a Dunnett's test or a t test for pairwise comparisons.

RESULTS

In OA, HS were characterized by increased sulfation levels compared to controls. Moreover, the capacity of these HS to bind HBP involved in the OA pathophysiological process such as FGF2 and VEGF was reduced. Chondroitin sulfates and keratan sulfates regulated these binding properties. Finally, HS from OA cartilages induced the mRNA levels of catabolic markers such as MMP3, MMP13, and TS4 and inhibited the mRNA levels of anabolic markers such as COL2, ACAN, SOX9, and VEGF in murine articular chondrocytes.

CONCLUSION

The sulfation of HS chains was increased in OA cartilages with changes in HBP binding properties and biological effects on chondrocyte phenotypes. Thus, modified HS present in altered cartilages could be a novel therapeutic target in OA.

Enhancement of cell proliferation and motility of mammalian cells grown in co-culture with Pichia pastoris expressing recombinant human FGF-2

Many studies examining the biological function of recombinant proteins and their effects on the physiology of mammalian cells stipulate that the proteins be purified before being used as therapeutic agents. In this study, we explored the possibility of using unpurified recombinant proteins to treat mammalian cells. The recombinant protein was used directly from the expression source and the biological function was compared to purified commercially available, equivalent protein. The model for this purpose was recombinant FGF-2, expressed by Pichia pastoris, which was used to treat the murine fibroblast cell line, NIH/3T3. We generated a P. pastoris strain (yHL11) that constitutively secreted a biologically active recombinant FGF-2 protein containing an N-terminal c-myc epitope (Myc-FGF-2). Myc-FGF-2 was then used without purification either a) in the form of conditioned mammalian cell culture medium or b) during co-cultures of yHL11 with NIH/3T3 to induce higher proliferation and motility of NIH/3T3 cells. The effects of Myc-FGF-2 on cell physiology were comparable to commercially available FGF-2. To our knowledge, this is the first time the physiology of cultured mammalian cells had been successfully altered with a recombinant protein secreted by P. pastoris while the two species shared the same medium and culture conditions. Our data demonstrated the biological activity of unpurified recombinant FGF-2 on NIH/3T3 cells and provided a foundation for directly using unpurified recombinant proteins expressed by P. pastoris with mammalian cells, potentially as wound-healing therapeutics.

Melatonin regulates tumor angiogenesis via miR-424-5p/VEGFA signaling pathway in osteosarcoma

Melatonin is recognized as an anti-angiogenic agent, but its function in the tumor microenvironment especially in osteosarcoma remains uncertain. Among the selected miRNAs, miR-205, miR-424, miR-140, miR-106, and miR-519 were upregulated by melatonin in osteosarcoma cells. The functional role of miR-424-5p in osteosarcoma was further analyzed using miR-424-5p mimic/inhibitor. VEGFA mRNA and protein expression were altered by miR-424-5p mimic/inhibitor transfection with and without melatonin treatment and it was further identified that the VEGFA 3'UTR is directly targeted by miR-424-5p using the luciferase reporter gene system. The conditioned medium from SaOS2 and MG63 cells treated with melatonin and/or transfected with miR-424-5p mimic/inhibitor was exposed to endothelial cells, and cell proliferation and migration was analyzed. MG-63 and SaOS2 cells are also transfected with miR-424-5p inhibitors and positioned on CAM vascular bed to study the angiogenic activity at both morphological and molecular level under melatonin treatment. Our observations demonstrate for the first time that, melatonin upregulated the expression of miR-424-5p in osteosarcoma inhibiting VEGFA. Furthermore, it suppresses tumor angiogenesis, modulating surrounding endothelial cell proliferation and migration as well as the morphology of blood vessels, and angiogenic growth factors. These findings suggest that melatonin could play a pivotal role in tumor suppression via miR-424-5p/VEGFA axis.

Sulfated syndecan 1 is critical to preventing cellular senescence by modulating fibroblast growth factor receptor endocytosis

Cellular senescence can be triggered by various intrinsic and extrinsic stimuli. We previously reported that silencing of 3'-phosphoadenosine 5'-phosphosulfate synthetase 2 (PAPSS2) induces cellular senescence through augmented fibroblast growth factor receptor 1 (FGFR1) signaling. However, the exact molecular mechanism connecting heparan sulfation and cellular senescence remains unclear. Here, we investigated the potential involvement of heparan sulfate proteoglycans (HSPGs) in augmented FGFR1 signaling and cellular senescence. Depletion of several types of HSPGs revealed that cells depleted of syndecan 1 (SDC1) exhibited typical senescence phenotypes, and those depleted of PAPSS2-, SDC1-, or heparan sulfate 2-O sulfotransferase 1 (HS2ST1) showed decreased FGFR1 internalization along with hyperresponsiveness to and prolonged activation of fibroblast growth factor 2 (FGF2)-stimulated FGFR1- v-akt murine thymoma viral oncogene homolog (AKT) signaling. Clathrin- and caveolin-mediated FGFR1 endocytosis contributed to cellular senescence through the FGFR1-AKT-p53-p21 signaling pathway. Dynasore treatment triggered senescence phenotypes, augmented FGFR1-AKT-p53-p21 signaling, and decreased SDC1 expression. Finally, the replicatively and prematurely senescent cells were characterized by decreases of SDC1 expression and FGFR1 internalization, and an increase in FGFR1-AKT-p53-p21 signaling. Together, our results demonstrate that properly sulfated SDC1 plays a critical role in preventing cellular senescence through the regulation of FGFR1 endocytosis.

Function of fibroblast growth factor 2 in gastric cancer occurrence and prognosis

The present study aimed to explore the role of fibroblast growth factor 2 (FGF2) in the development and prognosis of gastric cancer (GC). The relationship between FGF2 mRNA expression levels and the clinical characteristics of GC was investigated using microarray data from four GC cohorts involving 726 patients obtained from the Gene Expression Omnibus. The results of the present study indicated that FGF2 expression levels were an independent factor affecting the prognosis of GC. The primary functions of FGF2 were related to cell adhesion and angiogenesis, and patients with high levels of FGF2 expression had poorer TNM staging and prognosis; these differences were statistically significant. In terms of immune infiltration, a higher extent of M2 macrophage intrusion was observed in patients with higher levels of FGF2. However, the degree of infiltration by dendritic and CD4⁺ T cells was lower, and this difference was statistically significant. Multivariate Cox proportional hazards model analysis revealed that age, TNM staging and FGF2 expression levels were independent prognostic factors for GC. In summary, FGF2 expression was demonstrated to be an independent prognostic factor in GC, and higher levels of FGF2 may promote the progression of this malignancy.

Loss of endothelial sulfatase-1 after experimental sepsis attenuates subsequent pulmonary inflammatory responses

Sepsis patients are at increased risk for hospital-acquired pulmonary infections, potentially due to postseptic immunosuppression known as the compensatory anti-inflammatory response syndrome (CARS). CARS has been attributed to leukocyte dysfunction, with an unclear role for endothelial cells. The pulmonary circulation is lined by an endothelial glycocalyx, a heparan sulfate-rich layer essential to pulmonary homeostasis. Heparan sulfate degradation occurs early in sepsis, leading to lung injury. Endothelial synthesis of new heparan sulfates subsequently allows for glycocalyx reconstitution and endothelial recovery. We hypothesized that remodeling of the reconstituted endothelial glycocalyx, mediated by alterations in the endothelial machinery responsible for heparan sulfate synthesis, contributes to CARS. Seventy-two hours after experimental sepsis, coincident with glycocalyx reconstitution, mice demonstrated impaired neutrophil and protein influx in response to intratracheal lipopolysaccharide (LPS). The postseptic reconstituted glycocalyx was structurally remodeled, with enrichment of heparan sulfate disaccharides sulfated at the 6-O position of glucosamine. Increased 6-O-sulfation coincided with loss of endothelial sulfatase-1 (Sulf-1), an enzyme that specifically removes 6-O-sulfates from heparan sulfate. Intravenous administration of Sulf-1 to postseptic mice restored the pulmonary response to LPS, suggesting that loss of Sulf-1 was necessary for postseptic suppression of pulmonary inflammation. Endothelial-specific knockout mice demonstrated that loss of Sulf-1 was not sufficient to induce immunosuppression in non-septic mice. Knockdown of Sulf-1 in human pulmonary microvascular endothelial cells resulted in downregulation of the adhesion molecule ICAM-1. Taken together, our study indicates that loss of endothelial Sulf-1 is necessary for postseptic suppression of pulmonary inflammation, representing a novel endothelial contributor to CARS.

Heparan Sulfate-Editing Extracellular Sulfatases Enhance VEGF Bioavailability for Ischemic Heart Repair

RATIONALE

Mechanistic insight into the inflammatory response after acute myocardial infarction may inform new molecularly targeted treatment strategies to prevent chronic heart failure.

OBJECTIVE

We identified the sulfatase SULF2 in an in silico secretome analysis in bone marrow cells from patients with acute myocardial infarction and detected increased sulfatase activity in myocardial autopsy samples. SULF2 (Sulf2 in mice) and its isoform SULF1 (Sulf1) act as endosulfatases removing 6-O-sulfate groups from heparan sulfate (HS) in the extracellular space, thus eliminating docking sites for HS-binding proteins. We hypothesized that the Sulfs have a role in tissue repair after myocardial infarction.

METHODS AND RESULTS

Both Sulfs were dynamically upregulated after coronary artery ligation in mice, attaining peak expression and activity levels during the first week after injury. Sulf2 was expressed by monocytes and macrophages, Sulf1 by endothelial cells and fibroblasts. Infarct border zone capillarization was impaired, scar size increased, and cardiac dysfunction more pronounced in mice with a genetic deletion of either Sulf1 or Sulf2. Studies in bone marrow-chimeric Sulf-deficient mice and Sulf-deficient cardiac endothelial cells established that inflammatory cell-derived Sulf2 and endothelial cell-autonomous Sulf1 promote angiogenesis. Mechanistically, both Sulfs reduced HS sulfation in the infarcted myocardium, thereby diminishing Vegfa (vascular endothelial growth factor A) interaction with HS. Along this line, both Sulfs rendered infarcted mouse heart explants responsive to the angiogenic effects of HS-binding Vegfa₁₆₄ but did not modulate the angiogenic effects of non-HS-binding Vegfa₁₂₀. Treating wild-type mice systemically with the small molecule HS-antagonist surfen (bis-2-methyl-4-amino-quinolyl-6-carbamide, 1 mg/kg/day) for 7 days after myocardial infarction released Vegfa from HS, enhanced infarct border-zone capillarization, and exerted sustained beneficial effects on cardiac function and survival.

CONCLUSIONS

These findings establish HS-editing Sulfs as critical inducers of postinfarction angiogenesis and identify HS sulfation as a therapeutic target for ischemic tissue repair.

Sulfotransferase and Heparanase: Remodeling Engines in Promoting Virus Infection and Disease Development

An extraordinary binding site generated in heparan sulfate (HS) structures, during its biosynthesis, provides a unique opportunity to interact with multiple protein ligands including viral proteins, and therefore adds tremendous value to this master molecule. An example of such a moiety is the sulfation at the C3 position of glucosamine residues in HS chain via 3-O sulfotransferase (3-OST) enzymes, which generates a unique virus-cell fusion receptor during herpes simplex virus (HSV) entry and spread. Emerging evidence now suggests that the unique patterns in HS sulfation assist multiple viruses in invading host cells at various steps of their life cycles. In addition, sulfated-HS structures are known to assist in invading host defense mechanisms and initiating multiple inflammatory processes; a critical event in the disease development. All these processes are detrimental for the host and therefore raise the question of how HS-sulfation is regulated. Epigenetic modulations have been shown to be implicated in these reactions during HSV infection as well as in HS modifying enzyme sulfotransferases, and therefore pose a critical component in answering it. Interestingly, heparanase (HPSE) activity is shown to be upregulated during virus infection and multiple other diseases assisting in virus replication to promote cell and tissue damage. These phenomena suggest that sulfotransferases and HPSE serve as key players in extracellular matrix remodeling and possibly generating unique signatures in a given disease. Therefore, identifying the epigenetic regulation of OST genes, and HPSE resulting in altered yet specific sulfation patterns in HS chain during virus infection, will be a significant a step toward developing potential diagnostic markers and designing novel therapies.

Downstream Products are Potent Inhibitors of the Heparan Sulfate 2-O-Sulfotransferase

Heparan Sulfate (HS) is a cell signaling molecule linked to pathological processes ranging from cancer to viral entry, yet fundamental aspects of its biosynthesis remain incompletely understood. Here, the binding preferences of the uronyl 2-O-sulfotransferase (HS2ST) are examined with variably-sulfated hexasaccharides. Surprisingly, heavily sulfated oligosaccharides formed by later-acting sulfotransferases bind more tightly to HS2ST than those corresponding to its natural substrate or product. Inhibition assays also indicate that the IC50 values correlate simply with degree of oligosaccharide sulfation. Structural analysis predicts a mode of inhibition in which 6-O-sulfate groups located on glucosamine residues present in highly-sulfated oligosaccharides occupy the canonical binding site of the nucleotide cofactor. The unexpected finding that oligosaccharides associated with later stages in HS biosynthesis inhibit HS2ST indicates that the enzyme must be separated temporally and/or spatially from downstream products during biosynthesis in vivo, and highlights a challenge for the enzymatic synthesis of lengthy HS chains in vitro.

Downregulation of HS6ST2 by miR-23b-3p enhances matrix degradation through p38 MAPK pathway in osteoarthritis

Osteoarthritis (OA) is the most common form of arthritis involving major structural changes of peripheral joints and local or systemic inflammation and in lack of therapeutic approaches because of complexity of underlying molecular basis. Our previous work showed that HS6ST2, an enzyme involved in the transfer of sulfate, is downregulated in cartilage tissues of OA patients compared with normal donors, but little is known about its regulatory mechanism. In this study, we demonstrated that the expression of HS6ST2 was lower in OA-damaged cartilage than smooth cartilage from the same patient. In chondrocytes, HS6ST2 could be targeted by miR-23b-3p, which was higher expressed in OA-damaged cartilage. Under TNF-α stimulation, the expression of HS6ST2 was found inversely correlated with the expression of miR-23b-3p. Downregulation of HS6ST2 regulated by overexpression of miR-23b-3p and siRNAs against HS6ST2 could enhance the protein level of MMP13 and aggravate the matrix degradation in chondrocytes. Increased expression of MMP13 depended on activity of p38 MAPK rather than total p38 MAPK level and was abrogated by HS6ST2 overexpression. Together, the results indicated that downregulated HS6ST2 targeted by miR-23b-3p promotes matrix degradation by activating p38 MAPK in chondrocytes and OA cartilage.

Rhamnazin attenuates inflammation and inhibits alkali burn-induced corneal neovascularization in rats

The purpose of our study was to determine whether rhamnazin inhibits corneal neovascularization in the rat alkali burn model, and alleviates the inflammatory response of the cornea. Rhamnazin inhibited the proliferation of HUVEC cells in a dose-dependent manner, and it also inhibited the migration and luminal formation of HUVEC cells. 20 μM rhamnazin eye drops were applied to an animal model of corneal alkali burn neovascularization 4 times a day for 14 days. The corneal neovascularization in the rhamnazin group was obviously less than that in the PBS control group. In the rhamnazin group, the inflammatory index of the cornea decreased gradually over time, whereas the inflammatory index of the PBS group decreased only slightly with time. The corneal CNV area in the PBS group was significantly larger than that in the rhamnazin group. The expression level of VEGF protein of the rhamnazin group was lower than that in the PBS group, and the expression level of PEDF was significantly higher than that of the PBS group. Rhamnazin downregulated the expression of VEGFR2 protein and decreased the expression levels of p-STAT3, p-MAPK and p-Akt proteins. This study provides a new idea for the study of the molecular mechanism of corneal neovascularization.

The purpose of our study was to determine whether rhamnazin inhibits corneal neovascularization in the rat alkali burn model, and alleviates the inflammatory response of the cornea.

Heparanase: roles in cell survival, extracellular matrix remodelling and the development of kidney disease

Heparanase has regulatory roles in various processes, including cell communication, gene transcription and autophagy. In addition, it is the only known mammalian endoglycosidase that is capable of degrading heparan sulfate (HS). HS chains are important constituents and organizers of the extracellular matrix (ECM), and have a key role in maintaining the integrity and function of the glomerular filtration barrier. In addition, HS chains regulate the activity of numerous bioactive molecules, such as cytokines and growth factors, at the cell surface and in the ECM. Given the functional diversity of HS, its degradation by heparanase profoundly affects important pathophysiological processes, including tumour development, neovascularization and inflammation, as well as progression of kidney disease. Heparanase-mediated degradation and subsequent remodelling of HS in the ECM of the glomerulus is a key mechanism in the development of glomerular disease, as exemplified by the complete resistance of heparanase-deficient animals to diabetes and immune-mediated kidney disease. This Review summarizes the role of heparanase in the development of kidney disease, and its potential as a therapeutic target.

Structure Based Substrate Specificity Analysis of Heparan Sulfate 6-O-Sulfotransferases

Heparan sulfate (HS) is a sulfated polysaccharide exhibiting essential physiological functions. HS 6-O-sulfotransferase (6-OST) transfers a sulfo group to the 6-OH position of glucosamine units to confer a variety of HS biological activities. There are three different isoforms of 6-OST in the human genome. Here, we report crystal structures of the ternary complex of 6-OST with the sulfo donor analog 3'-phosphoadenosine 5'-phosphate and three different oligosaccharide substrates at 1.95 to 2.1 Å resolutions. Structural and mutational analyses reveal amino acid residues that contribute to catalysis and substrate recognition of 6-OST. Unexpectedly, the structures reveal 6-OST engages HS in a completely different orientation than other HS sulfotransferases and sheds light on the basic HS requirements for specificity. These findings also contribute structural information to understand mutations in human 6-OST isoform 1 associated with the human genetic disease idiopathic hypogonadotropic hypogonadism characterized by incomplete or lack of puberty.

The "in and out" of glucosamine 6-O-sulfation: the 6th sense of heparan sulfate

The biological properties of Heparan sulfate (HS) polysaccharides essentially rely on their ability to bind and modulate a multitude of protein ligands. These interactions involve internal oligosaccharide sequences defined by their sulfation patterns. Amongst these, the 6-O-sulfation of HS contributes significantly to the polysaccharide structural diversity and is critically involved in the binding of many proteins. HS 6-O-sulfation is catalyzed by 6-O-sulfotransferases (6OSTs) during biosynthesis, and it is further modified by the post-synthetic action of 6-O-endosulfatases (Sulfs), two enzyme families that remain poorly characterized. The aim of the present review is to summarize the contribution of 6-O-sulfates in HS structure/function relationships and to discuss the present knowledge on the complex mechanisms regulating HS 6-O-sulfation.

Formononetin, a novel FGFR2 inhibitor, potently inhibits angiogenesis and tumor growth in preclinical models

Most anti-angiogenic therapies currently being evaluated in clinical trials target vascular endothelial growth factor (VEGF) pathway, however, the tumor vasculature can acquire resistance to VEGF-targeted therapy by shifting to other angiogenesis mechanisms. Therefore, other potential therapeutic agents that block non-VEGF angiogenic pathways need to be evaluated. Here we identified formononetin as a novel agent with potential anti-angiogenic and anti-cancer activities. Formononetin demonstrated inhibition of endothelial cell proliferation, migration, and tube formation in response to basic fibroblast growth factor 2 (FGF2). In ex vivo and in vivo angiogenesis assays, formononetin suppressed FGF2-induced microvessel sprouting of rat aortic rings and angiogenesis. To understand the underlying molecular basis, we examined the effects of formononetin on different molecular components in treated endothelial cell, and found that formononetin suppressed FGF2-triggered activation of FGFR2 and protein kinase B (Akt) signaling. Moreover, formononetin directly inhibited proliferation and blocked the oncogenic signaling pathways in breast cancer cell. In vivo, using xenograft models of breast cancer, formononetin showed growth-inhibitory activity associated with inhibition of tumor angiogenesis. Moreover, formononetin enhanced the effect of VEGFR2 inhibitor sunitinib on tumor growth inhibition. Taken together, our results indicate that formononetin targets the FGFR2-mediated Akt signaling pathway, leading to the suppression of tumor growth and angiogenesis.

Integrated Approach to Identify Heparan Sulfate Ligand Requirements of Robo1

An integrated methodology is described to establish ligand requirements for heparan sulfate (HS) binding proteins based on a workflow in which HS octasaccharides are produced by partial enzymatic degradation of natural HS followed by size exclusion purification, affinity enrichment using an immobilized HS-binding protein of interest, putative structure determination of isolated compounds by a hydrophilic interaction chromatography-high-resolution mass spectrometry platform, and chemical synthesis of well-defined HS oligosaccharides for structure-activity relationship studies. The methodology was used to establish the ligand requirements of human Roundabout receptor 1 (Robo1), which is involved in a number of developmental processes. Mass spectrometric analysis of the starting octasaccharide mixture and the Robo1-bound fraction indicated that Robo1 has a preference for a specific set of structures. Further analysis was performed by sequential permethylation, desulfation, and pertrideuteroacetylation followed by online separation and structural analysis by MS/MS. Sequences of tetrasaccharides could be deduced from the data, and by combining the compositional and sequence data, a putative octasaccharide ligand could be proposed (GlA-GlcNS6S-IdoA-GlcNS-IdoA2S-GlcNS6S-IdoA-GlcNAc6S). A modular synthetic approach was employed to prepare the target compound, and binding studies by surface plasmon resonance (SPR) confirmed it to be a high affinity ligand for Robo1. Further studies with a number of tetrasaccharides confirmed that sulfate esters at C-6 are critical for binding, whereas such functionalities at C-2 substantially reduce binding. High affinity ligands were able to reverse a reduction in endothelial cell migration induced by Slit2-Robo1 signaling.

Tumour-necrosis factor-α induces heparan sulfate 6-O-endosulfatase 1 (Sulf-1) expression in fibroblasts

Heparan sulfate (HS) 6-O-endosulfatases (Sulfs) have emerged recently as critical regulators of many physiological and pathological processes. By removing 6-O-sulfates from specific HS sequences, they modulate the activities of a variety of growth factors and morphogens, including fibroblast growth factor (FGF)-1. However, little is known about the functions of Sulfs in inflammation. Tumour-necrosis factor (TNF)-α plays an important role in regulating the behaviour of fibroblasts. In this study, we examined the effect of this inflammatory cytokine on the expression of Sulfs in human MRC-5 fibroblasts. Compositional analysis of HS from TNF-α-treated cells showed a strong reduction in the amount of the trisulfated UA2S-GlcNS6S disaccharide, which suggested a selective reaction of 6-O-desulfation. Real-time PCR analysis revealed that TNF-α increased Sulf-1 expression in a dose- and time-dependent manner, via a mechanism involving NF-ĸB, ERK1/2 and p38 MAPK. In addition, we confirmed that cell stimulation with TNF-α was accompanied by the secretion of an active form of Sulf-1. To study the function of Sulf- 1, we examined the responses induced by FGF-1. We showed that ERK1/2 activation and cell proliferation were markedly reduced in TNF-α-treated MRC-5 cells compared with untreated cells. Silencing the expression of Sulf-1 by RNA interference restored the responses induced by FGF-1, which indicated that TNF-α-mediated induction of the sulfatase indeed resulted in alterations of HS biological properties. Taken together, our results indicate that Sulf-1 is responsive to TNF-α stimulation and may function as an autocrine regulator of fibroblast expansion in the course of an inflammatory response.

Synthetic Site-Selectively Mono-6-O-Sulfated Heparan Sulfate Dodecasaccharide Shows Anti-Angiogenic Properties In Vitro and Sensitizes Tumors to Cisplatin In Vivo

Heparan sulphate (HS), a ubiquitously expressed glycosaminoglycan (GAG), regulates multiple cellular functions by mediating interactions between numerous growth factors and their cell surface cognate receptors. However, the structural specificity of HS in these interactions remains largely undefined. Here, we used completely synthetic, structurally defined, alternating N-sulfated glucosamine (NS) and 2-O-sulfated iduronate (IS) residues to generate dodecasaccharides ([NSIS]₆) that contained no, one or six glucosamine 6-O-sulfates (6S). The aim was to address how 6S contributes to the potential of defined HS dodecasaccharides to inhibit the angiogenic growth factors FGF2 and VEGF₁₆₅, in vitro and in vivo. We show that the addition of a single 6S at the non-reducing end of [NSIS]₆, i.e. [NSIS6S]-[NSIS]₅, significantly augments the inhibition of FGF2-dependent endothelial cell proliferation, migration and sprouting in vitro when compared to the non-6S variant. In contrast, the fully 6-O-sulfated dodecasaccharide, [NSIS6S]₆, is not a potent inhibitor of FGF2. Addition of a single 6S did not significantly improve inhibitory properties of [NSIS]₆ when tested against VEGF₁₆₅-dependent endothelial cell functions.In vivo, [NSIS6S]-[NSIS]₅ blocked FGF2-dependent blood vessel formation without affecting tumor growth. Reduction of non-FGF2-dependent ovarian tumor growth occurred when [NSIS6S]-[NSIS]₅ was combined with cisplatin. The degree of inhibition by [NSIS6S]-[NSIS]₅ in combination with cisplatin in vivo equated with that induced by bevacizumab and sunitinib when administered with cisplatin. Evaluation of post-treatment vasculature revealed that [NSIS6S]-[NSIS]₅ treatment had the greatest impact on tumor blood vessel size and lumen formation. Our data for the first time demonstrate that synthetic, structurally defined oligosaccharides have potential to be developed as active anti-angiogenic agents that sensitize tumors to chemotherapeutic agents.

A Naturally Derived, Growth Factor-Binding Polysaccharide for Therapeutic Angiogenesis

We herein report the discovery of a naturally derived carbohydrate with binding affinities for two pro-angiogenic growth factors-fibroblast growth factor-2 (FGF-2) and platelet-derived growth factor-BB (PDGF-BB). This galacturonic acid-containing polysaccharide (EUP3) sequestered endogenous FGF-2 and PDGF-BB in vivo and promoted in situ formation and maturation of new blood vessels. Our findings suggest EUP3 as the first nonglycosaminoglycan, nonanimal-originated carbohydrate molecule that binds two pro-angiogenic growth factors to stimulate angiogenesis. Further investigations into this carbohydrate may lead to the development of new tools for therapeutic angiogenesis.

2- and 6-O-sulfated proteoglycans have distinct and complementary roles in cranial axon guidance and motor neuron migration

The correct migration and axon extension of neurons in the developing nervous system is essential for the appropriate wiring and function of neural networks. Here, we report that O-sulfotransferases, a class of enzymes that modify heparan sulfate proteoglycans (HSPGs), are essential to regulate neuronal migration and axon development. We show that the 6-O-sulfotransferases HS6ST1 and HS6ST2 are essential for cranial axon patterning, whilst the 2-O-sulfotransferase HS2ST (also known as HS2ST1) is important to regulate the migration of facial branchiomotor (FBM) neurons in the hindbrain. We have also investigated how HS2ST interacts with other signals in the hindbrain and show that fibroblast growth factor (FGF) signalling regulates FBM neuron migration in an HS2ST-dependent manner.

Summary: 2-O-sulfated proteoglycans are essential for cranial motor neuron migration, whereas 6-O-sulfated proteoglycans regulate cranial axon guidance.

Heparan sulfate D-glucosaminyl 3-O-sulfotransferase-3B1 (HS3ST3B1) promotes angiogenesis and proliferation by induction of VEGF in acute myeloid leukemia cells

Heparan sulfate (HS) are complex polysaccharides that reside on the plasma membrane of almost all mammalian cells, and play an important role in physiological and pathological conditions. Heparan sulfate D-glucosamine 3-O-sulfotransferase 3B1 (HS3ST3B1) participates in the last biosynthetic steps of HS and transfers sulfate to the 3-O-position of glucosamine residues to yield mature sugar chains. To date very few biological processes or proteins have been described that are modulated by HS3ST3B1. In this study, we observed that HS3ST3B1 positively contributed to acute myeloid leukemia (AML) progression in vitro and in vivo, and these activities were associated with an induction of the proangiogenic factor VEGF expression and shedding. Moreover, the effects of HS3ST3B1 on VEGF release can be attenuated after treatment of heparanase inhibitor suramin, which prevented VEGF secretion and subsequently blocked VEGF-induced activation of ERK and AKT, suggesting that 3-O-sulfation of HS by HS3ST3B1 facilitated VEGF shedding; the effects of HS3ST3B1 on activation of ERK and AKT can also be blocked by VEGFR inhibitor axitinib, suggestive of a relationship between 3-O-sulfation of HS and VEGF-activated signaling pathways. Taken together, our findings support that VEGF is an important functional target of HS3ST3B1 and provide a new mechanism of HS3ST3B1 in AML.

Heparanase and Syndecan-4 Are Involved in Low Molecular Weight Fucoidan-Induced Angiogenesis

Induction of angiogenesis is a potential treatment for chronic ischemia. Low molecular weight fucoidan (LMWF), the sulfated polysaccharide from brown seaweeds, has been shown to promote revascularization in a rat limb ischemia, increasing angiogenesis in vivo. We investigated the potential role of two heparan sulfate (HS) metabolism enzymes, exostosin-2 (EXT2) and heparanase (HPSE), and of two HS-membrane proteoglycans, syndecan-1 and -4 (SDC-1 and SDC-4), in LMWF induced angiogenesis. Our results showed that LMWF increases human vascular endothelial cell (HUVEC) migration and angiogenesis in vitro. We report that the expression and activity of the HS-degrading HPSE was increased after LMWF treatment. The phenotypic tests of LMWF-treated and EXT2- or HPSE-siRNA-transfected cells indicated that EXT2 or HPSE expression significantly affect the proangiogenic potential of LMWF. In addition, LMWF increased SDC-1, but decreased SDC-4 expressions. The effect of LMWF depends on SDC-4 expression. Silencing EXT2 or HPSE leads to an increased expression of SDC-4, providing the evidence that EXT2 and HPSE regulate the SDC-4 expression. Altogether, these data indicate that EXT2, HPSE, and SDC-4 are involved in the proangiogenic effects of LMWF, suggesting that the HS metabolism changes linked to LMWF-induced angiogenesis offer the opportunity for new therapeutic strategies of ischemic diseases.

The great escape; the hallmarks of resistance to antiangiogenic therapy

The concept of antiangiogenic therapy in cancer treatment has led to the approval of different agents, most of them targeting the well known vascular endothelial growth factor pathway. Despite promising results in preclinical studies, the efficacy of antiangiogenic therapy in the clinical setting remains limited. Recently, awareness has emerged on resistance to antiangiogenic therapies. It has become apparent that the intricate complex interplay between tumors and stromal cells, including endothelial cells and associated mural cells, allows for escape mechanisms to arise that counteract the effects of these targeted therapeutics. Here, we review and discuss known and novel mechanisms that contribute to resistance against antiangiogenic therapy and provide an outlook to possible improvements in therapeutic approaches.

Xanthatin, a novel potent inhibitor of VEGFR2 signaling, inhibits angiogenesis and tumor growth in breast cancer cells

Anti-angiogenesis targeting vascular endothelial growth factor receptor 2 (VEGFR2) has emerged as an important tool for cancer treatment. In this study, we described a novel VEGFR2 inhibitor, xanthatin, which inhibits tumor angiogenesis and growth. The biochemical profiles of xanthatin were investigated using kinase assay, migration assay, tube formation, Matrigel plug assay, western blot, immunofluorescence and human tumor xenograft model. Xanthatin significantly inhibited growth, migration and tube formation of human umbilical vascular endothelial cell as well as inhibited vascular endothelial growth factor (VEGF)-stimulated angiogenesis. In addition, it inhibited VEGF-induced phosphorylation of VEGFR2 and its downstream signaling regulator. Moreover, xanthatin directly inhibit proliferation of breast cancer cells MDA-MB-231. Oral administration of xanthatin could markedly inhibit human tumor xenograft growth and decreased microvessel densities (MVD) in tumor sections. Taken together, these preclinical evaluations suggest that xanthatin inhibits angiogenesis and may be a promising anticancer drug candidate.

Synthetic heparan sulfate dodecasaccharides reveal single sulfation site interconverts CXCL8 and CXCL12 chemokine biology

The multigram-scale synthesis of a sulfation-site programmed heparin-like dodecasaccharide is described. Evaluation alongside dodecasaccharides lacking this single glucosamine O6-sulfation, or having per-O6-sulfation, shows that site-specific modification of the terminal glucosamine dramatically interconverts regulation of in vitro and in vivo biology mediated by the two important chemokines, CXCL12 (SDF1α) or CXCL8 (IL-8).

Fell-Muir Lecture: Heparan sulphate and the art of cell regulation: a polymer chain conducts the protein orchestra

Heparan sulphate (HS) sits at the interface of the cell and the extracellular matrix. It is a member of the glycosaminoglycan family of anionic polysaccharides with unique structural features designed for protein interaction and regulation. Its client proteins include soluble effectors (e.g. growth factors, morphogens, chemokines), membrane receptors and cell adhesion proteins such as fibronectin, fibrillin and various types of collagen. The protein-binding properties of HS, together with its strategic positioning in the pericellular domain, are indicative of key roles in mediating the flow of regulatory signals between cells and their microenvironment. The control of transmembrane signalling is a fundamental element in the complex biology of HS. It seems likely that, in some way, HS orchestrates diverse signalling pathways to facilitate information processing inside the cell. A dictionary definition of an orchestra is 'a large group of musicians who play together on various instruments …' to paraphrase, the HS orchestra is 'a large group of proteins that play together on various receptors'. HS conducts this orchestra to ensure that proteins hit the right notes on their receptors but, in the manner of a true conductor, does it also set 'the musical pulse' and create rhythm and harmony attractive to the cell? This is too big a question to answer but fun to think about as you read this review.

Making the longest sugars: a chemical synthesis of heparin-related [4] n oligosaccharides from 16-mer to 40-mer

The chemical synthesis of long oligosaccharides remains a major challenge. In particular, the synthesis of glycosaminoglycan (GAG) oligosaccharides belonging to the heparin and heparan sulfate (H/HS) family has been a high profile target, particularly with respect to the longer heparanome. Herein we describe a synthesis of the longest heparin-related oligosaccharide to date and concurrently provide an entry to the longest synthetic oligosaccharides of any type yet reported. Specifically, the iterative construction of a series of [4] _n -mer heparin-backbone oligosaccharides ranging from 16-mer through to the 40-mer in length is described. This demonstrates for the first time the viability of generating long sequence heparanoids by chemical synthesis, via practical solution-phase synthesis. Pure-Shift HSQC NMR provides a dramatic improvement in anomeric signal resolution, allowing full resolution of all 12 anomeric protons and extrapolation to support anomeric integrity of the longer species. A chemically pure 6-O-desfulfated GlcNS-IdoAS icosasaccharide (20-mer) represents the longest pure synthetic heparin-like oligosaccharide.

Overexpression of heparan sulfate 6-O-sulfotransferase-2 enhances fibroblast growth factor-mediated chondrocyte growth and differentiation

In our previous study, we reported that heparan sulfate 6-O-sulfotransferase‑2 (HS6ST2) plays an important role in the cartilage of patients with osteoarthritis and Kashin-Beck disease and that it regulates aggrecan (Acan) metabolism and the viability of chondrocytes. However, its role in chondrocyte differentiation remains poorly understood. In the present study, we aimed to investigate the role of HS6ST2 in chondrocyte differentiation in vitro using mouse prechondrocytic cells. We found that the overexpression or silencing of HS6ST2 significantly enhanced or abrogated the effects of fibroblast growth factor (FGF)‑2 on chondrocyte growth, respectively. We found that the overexpression of HS6ST2 significantly induced the expression of Acan as well as the amount of total proteoglycans in the prechondrocytic cells in the presence of FGF‑2, whereas the silencing of HS6ST2 caused the opposite effect. Furthermore, the expresssion of FGF‑2‑induced sex‑determining region Y‑type high mobility group box protein 9 (SOX9), a major transcription factor for chondrocyte proliferation and differentiation, was also enhanced or blocked by HS6ST2 overexpression or HS6ST2 knockdown, respectively. Additionally, Wnt/β‑catenin signaling, which inhibited chondrocyte proliferation and differentiation, was suppressed by HS6ST2. Taken together, these data suggest that HS6ST2 plays an important role in regulating chondrocyte growth and differentiation by modulating FGF‑2 signaling, thus indicating that it may be a potential and valuable molecular target for the treatment of skeletal dysplasias, such as dwarfism.

The potential of fibroblast growth factor/fibroblast growth factor receptor signaling as a therapeutic target in tumor angiogenesis

INTRODUCTION

Fibroblast growth factors (FGFs) are endowed with a potent pro-angiogenic activity. Activation of the FGF/FGF receptor (FGFR) system occurs in a variety of human tumors. This may lead to neovascularization, supporting tumor progression and metastatic dissemination. Thus, a compelling biologic rationale exists for the development of anti-FGF/FGFR agents for the inhibition of tumor angiogenesis in cancer therapy.

AREAS COVERED

A comprehensive search on PubMed was performed to identify studies on the role of the FGF/FGFR system in angiogenesis. Endothelial FGFR signaling, the pro-angiogenic function of canonical FGFs, and their role in human tumors are described. In addition, experimental approaches aimed at the identification and characterization of nonselective and selective FGF/FGFR inhibitors and their evaluation in clinical trials are summarized.

EXPERT OPINION

Different approaches can be envisaged to inhibit the FGF/FGFR system, a target for the development of 'two-compartment' anti-angiogenic/anti-tumor agents, including FGFR selective and nonselective small-molecule tyrosine kinase inhibitors, anti-FGFR antibodies, and FGF ligand traps. Further studies are required to define the correlation between tumor vascularization and activation of the FGF/FGFR system and for the identification of cancer patients more likely to benefit from anti-FGF/FGFR treatments. In addition, advantages and disadvantages about the use of selective versus non-selective FGF inhibitors remain to be elucidated.

A common sugar-nucleotide-mediated mechanism of inhibition of (glycosamino)glycan biosynthesis, as evidenced by 6F-GalNAc (Ac3)

Glycosaminoglycan (GAG) polysaccharides have been implicated in a variety of cellular processes, and alterations in their amount and structure have been associated with diseases such as cancer. In this study, we probed 11 sugar analogs for their capacity to interfere with GAG biosynthesis. One analog, with a modification not directly involved in the glycosidic bond formation, 6F-N-acetyl-d-galactosamine (GalNAc) (Ac3), was selected for further study on its metabolic and biologic effect. Treatment of human ovarian carcinoma cells with 50 μM 6F-GalNAc (Ac3) inhibited biosynthesis of GAGs (chondroitin/dermatan sulfate by ∼50-60%, heparan sulfate by ∼35%), N-acetyl-d-glucosamine (GlcNAc)/GalNAc containing glycans recognized by the lectins Datura stramonium and peanut agglutinin (by ∼74 and ∼43%, respectively), and O-GlcNAc protein modification. With respect to function, 6F-GalNAc (Ac3) treatment inhibited growth factor signaling and reduced in vivo angiogenesis by ∼33%. Although the analog was readily transformed in cells into the uridine 5'-diphosphate (UDP)-activated form, it was not incorporated into GAGs. Rather, it strongly reduced cellular UDP-GalNAc and UDP-GlcNAc pools. Together with data from the literature, these findings indicate that nucleotide sugar depletion without incorporation is a common mechanism of sugar analogs for inhibiting GAG/glycan biosynthesis.

Modular synthesis of heparin-related tetra-, hexa- and octasaccharides with differential o-6 protections: programming for regiodefined 6-o-modifications

Heparin and heparan sulphate (H/HS) are important members of the glycosaminoglycan family of sugars that regulate a substantial number of biological processes. Such biological promiscuity is underpinned by hetereogeneity in their molecular structure. The degree of O-sulfation, particularly at the 6-position of constituent D-GlcN units, is believed to play a role in modulating the effects of such sequences. Synthetic chemistry is essential to be able to extend the diversity of HS-like fragments with defined molecular structure, and particularly to deconvolute the biological significance of modifications at O6. Here we report a synthetic approach to a small matrix of protected heparin-type oligosaccharides, containing orthogonal D-GlcN O-6 protecting groups at programmed positions along the chain, facilitating access towards programmed modifications at specific sites, relevant to sulfation or future mimetics.

Growth factor and small molecule influence on urological tissue regeneration utilizing cell seeded scaffolds

Regenerative medicine strategies combine various attributes from multiple disciplines including stem cell biology, chemistry, materials science and medicine. The junction at which these disciplines intersect provides a means to address unmet medical needs in an assortment of pathologies with the goal of creating sustainable, functional replacement tissues. Tissue damage caused by trauma for example, requires rapid responses in order to mitigate further tissue deterioration. Cell/scaffold composites have been utilized to initiate and stabilize regenerative responses in vivo with the hope that functional tissue can be attained. Along with the gross reconfiguration of regenerating tissues, small molecules and growth factors also play a pivotal role in tissue regeneration. Several regenerative studies targeting a variety of urological tissues demonstrate the utility of these small molecules or growth factors in an in vivo setting.

Glycosaminoglycans in cancer treatment

Studies aimed at the identification of biomarkers and treatment targets of cancer have focused on mRNAs, miRNAs, and proteins expressed by malignant cells, while glycoproteins mainly produced by stromal cells remain relatively unexplored. Glycans lack a given template for their biosynthesis that involves the concerted action of several, sometimes >15 different enzymes. This fact complicates the analysis at the genomic level of the role of glycoproteins in clinical oncology. The glycosaminoglycans (GAGs) stand out as highly polyanionic components at the surface of malignant and stromal tumor cells as well as their surrounding matrix. Published data thus describe a multifaceted regulatory role of GAGs and GAG-conjugated proteins, proteoglycans, in e.g. tumor associated angiogenesis, coagulation, invasion, and metastasis. Relatively small, randomized clinical trials suggest that heparin, an over-sulfated variant of the GAG heparan sulfate, may have direct, anti-tumor effects. Several ongoing trials aim at establishing whether heparin and its derivatives should be added to standard treatment of cancer patients or not, based on progression free- and overall survival end-point data. Given the potential bleeding complications with this treatment, other strategies to block GAG function should provide interesting alternatives. In the emerging era of personalized medicine, one can foresee the development of predictive biomarkers to select patients that may benefit from GAG-targeted treatments, aiming at individualized prevention of thromboembolic complications as well as inhibition of tumor development and progression. Here, the role of GAGs as targets and vehicles of cancer treatment is discussed with special emphasis on angiogenesis and coagulation associated mechanisms.

Segregation of late outgrowth endothelial cells into functional endothelial CD34- and progenitor-like CD34+ cell populations

Late outgrowth endothelial cells (OECs) that originate from peripheral blood mononuclear cells ex vivo have phenotypic and functional properties of mature endothelial cells. Given the potential therapeutic applications of OECs, understanding their biology is crucial. We have identified two distinct OEC populations based on differential expression of the cell surface marker CD34. OEC colonies lacked CD34 expression (CD34-), expressed CD34 in the majority of cells (CD34+), or showed a mixed expression pattern within a colony (CD34+/-). CD34+ and CD34- OECs were negative for hematopoietic cell marker CD45 and expressed the endothelial cell surface markers CD31, CD146, CD105, and VEGFR-2. Functionally CD34- and CD34+ OECs exhibited strikingly distinct behaviors. CD34- OECs, unlike CD34+ OECs, were capable of sprouting, formed tubes, and responded to angiogenic growth factors in vitro. In vivo, CD34- OECs formed endothelial tubes, while CD34+ OECs, despite being unable to form tubes, promoted infiltration of murine vasculature. Global gene expression profiling in CD34- and CD34+ OECs identified functional importance of the MMP-1/PAR-1 pathway in CD34- OECs. MMP-1 stimulated the expression of VEGFR-2, neuropilin-1, neuropilin-2, and CXCR4 and activated ERK1/2, whereas down-regulation of PAR-1 in CD34- OECs resulted in impaired angiogenic responses in vitro and reduced VEGFR-2 levels. In contrast, the CD34+ OEC colonies expressed high levels of the progenitor cell marker ALDH, which was absent in CD34- OECs. In summary, we show that OECs can be classified into functionally mature endothelial cells (CD34- OECs) that depend on the MMP-1/PAR-1 pathway and progenitor-like angiogenesis-promoting cells (CD34+ OECs).

The development of anti-angiogenic heparan sulfate oligosaccharides

Angiogenesis has emerged as a novel target for anti-cancer therapies through randomized clinical trials that tested the benefit of adding vascular endothelial growth factor (VEGF) inhibitors to conventional cytotoxic therapies. However, despite improvements in the progression-free survival, the benefit in overall survival is modest. Tumour angiogenesis is regulated by a number of angiogenic cytokines. Thus innate or acquired resistance to VEGF inhibitors can be caused, at least in part, through expression of other angiogenic cytokines, including fibroblast growth factor 2 (FGF2), interleukin 8 (IL-8) and stromal-cell-derived factor 1α (SDF-1α), which make tumours insensitive to VEGF signalling pathway inhibition. The majority of angiogenic cytokines, including VEGF-A, FGF2, IL-8 and SDF-1α, manifest an obligate dependence on heparan sulfate (HS) for their biological activity. This mandatory requirement of angiogenic cytokines for HS identifies HS as a potential target for novel anti-angiogenic therapy. Targeting multiple angiogenic cytokines with HS mimetics may represent an opportunity to inhibit tumour angiogenesis more efficiently. Our published studies and unpublished work have demonstrated the feasibility of generating synthetic HS fragments of defined structure with biological activity against a number of angiogenic cytokines.