Dermatan Sulfate Proteoglycan and Glycosaminoglycan Synthesis Is Induced in Fibroblasts by Transfer to a Three-dimensional Extracellular Environment

An Autoantigen Atlas From Human Lung HFL1 Cells Offers Clues to Neurological and Diverse Autoimmune Manifestations of COVID-19

COVID-19 is accompanied by a myriad of both transient and long-lasting autoimmune responses. Dermatan sulfate (DS), a glycosaminoglycan crucial for wound healing, has unique affinity for autoantigens (autoAgs) from apoptotic cells. DS-autoAg complexes are capable of stimulating autoreactive B cells and autoantibody production. We used DS-affinity proteomics to define the autoantigen-ome of lung fibroblasts and bioinformatics analyses to study the relationship between autoantigenic proteins and COVID-induced alterations. Using DS-affinity, we identified an autoantigen-ome of 408 proteins from human HFL1 cells, at least 231 of which are known autoAgs. Comparing with available COVID data, 352 proteins of the autoantigen-ome have thus far been found to be altered at protein or RNA levels in SARS-CoV-2 infection, 210 of which are known autoAgs. The COVID-altered proteins are significantly associated with RNA metabolism, translation, vesicles and vesicle transport, cell death, supramolecular fibrils, cytoskeleton, extracellular matrix, and interleukin signaling. They offer clues to neurological problems, fibrosis, smooth muscle dysfunction, and thrombosis. In particular, 150 altered proteins are related to the nervous system, including axon, myelin sheath, neuron projection, neuronal cell body, and olfactory bulb. An association with the melanosome is also identified. The findings from our study illustrate a connection between COVID infection and autoimmunity. The vast number of COVID-altered proteins with high intrinsic propensity to become autoAgs offers an explanation for the diverse autoimmune complications in COVID patients. The variety of autoAgs related to mRNA metabolism, translation, and vesicles suggests a need for long-term monitoring of autoimmunity in COVID. The COVID autoantigen atlas we are establishing provides a detailed molecular map for further investigation of autoimmune sequelae of the pandemic, such as “long COVID” syndrome.

The Matrisome Is Associated with Metabolic Reprograming in Stem-like Phenotypes of Gastric Cancer

Simple Summary

Our results suggested a correlation between the metabolic reprogramming associated with the high-matrisome group and stem-like phenotype in gastric cancer. Carbohydrate sulfotransferase 7 was found to be associated with the signaling transduction of overexpressed oncogenes and tumor suppressor genes in the high-matrisome group. The high expression of glycosaminoglycan biosynthesis-chondroitin sulfate metabolic pathway genes was associated with poor prognosis.

Abstract

The extracellular matrix (ECM) is an important regulator of all cellular functions, and the matrisome represents a major component of the tumor microenvironment. The matrisome is an essential component comprising genes encoding ECM glycoproteins, collagens, and proteoglycans; however, its role in cancer progression and the development of stem-like molecular subtypes in gastric cancer is unknown. We analyzed gastric cancer data from five molecular subtypes (n = 497) and found that metabolic reprograming differs based on the state of the matrisome. Approximately 95% of stem-like cancer type samples of gastric cancer were in the high-matrisome category, and energy metabolism was considerably increased in the high-matrisome group. Particularly, high glycosaminoglycan biosynthesis-chondroitin sulfate metabolic reprograming was associated with an unfavorable prognosis. Glycosaminoglycan biosynthesis-chondroitin sulfate metabolic reprograming may occur according to the matrisome status and contribute to the development of stem-like phenotypes. Our analysis suggests the possibility of precision medicine for anticancer therapies.

AMPK differentially alters sulphated glycosaminoglycans under normal and high glucose milieu in proximal tubular cells

Glycosaminoglycans (GAGs) and AMP-activated protein kinase (AMPK) are two critical molecular players involved in cellular homeostasis. Both of them are altered due to hyperglycaemia in the kidney, leading to the pathogenesis of diabetic nephropathy. Here, we have looked into the effect of AMPK modulation on sulphated GAG (sGAG) levels of tubular cells of proximal and distal origin to understand the mechanism of hyperglycaemia-mediated pathogenesis of the diabetic nephropathy. In MDCK cells (distal tubular cell) and NRK-52E (proximal tubular cell), AMPK inhibition resulted in increased sGAG levels under normal glucose conditions characteristically of heparan sulphate class, whereas AMPK activation did not have any effect. High glucose (HG) condition did not alter sGAG levels in MDCK cell despite a decrease in AMPK phosphorylation. Subjecting NRK-52E cells to HG milieu significantly decreased sGAG levels more so of chondroitin/dermatan sulphate, which is significantly prevented when HG is co-treated with AMPK activator. Interestingly, knockdown of AMPK by AMPKα1/α2 siRNA showed increased sGAG levels in NRK-52E. Our results suggest that changes in sGAG level, in particular, as a result of AMPK modulation is differentially regulated and is dependent on cell type as well as its physiological status. Furthermore, activation of AMPK is beneficial in preventing the HG-mediated decrease in sGAGs in proximal tubular cells.

An Autoantigen Atlas from Human Lung HFL1 Cells Offers Clues to Neurological and Diverse Autoimmune Manifestations of COVID-19

COVID-19 is accompanied by a myriad of both transient and long-lasting autoimmune responses. Dermatan sulfate (DS), a glycosaminoglycan crucial for wound healing, has unique affinity for autoantigens (autoAgs) from apoptotic cells. DS-autoAg complexes are capable of stimulating autoreactive B cells and autoantibody production. Using DS affinity, we identified an autoantigenome of 408 proteins from human fetal lung fibroblast HFL11 cells, at least 231 of which are known autoAgs. Comparing with available COVID data, 352 proteins of the autoantigenome have thus far been found to be altered at protein or RNA levels in SARS-Cov-2 infection, 210 of which are known autoAgs. The COVID-altered proteins are significantly associated with RNA metabolism, translation, vesicles and vesicle transport, cell death, supramolecular fibrils, cytoskeleton, extracellular matrix, and interleukin signaling. They offer clues to neurological problems, fibrosis, smooth muscle dysfunction, and thrombosis. In particular, 150 altered proteins are related to the nervous system, including axon, myelin sheath, neuron projection, neuronal cell body, and olfactory bulb. An association with the melanosome is also identified. The findings from our study illustrate a strong connection between viral infection and autoimmunity. The vast number of COVID-altered proteins with propensity to become autoAgs offers an explanation for the diverse autoimmune complications in COVID patients. The variety of autoAgs related to mRNA metabolism, translation, and vesicles raises concerns about potential adverse effects of mRNA vaccines. The COVID autoantigen atlas we are establishing provides a detailed molecular map for further investigation of autoimmune sequelae of the pandemic.

A Possible Role for Arylsulfatase G in Dermatan Sulfate Metabolism

Perturbations of glycosaminoglycan metabolism lead to mucopolysaccharidoses (MPS)—lysosomal storage diseases. One type of MPS (type VI) is associated with a deficiency of arylsulfatase B (ARSB), for which we previously established a cellular model using pulmonary artery endothelial cells with a silenced ARSB gene. Here, we explored the effects of silencing the ARSB gene on the growth of human pulmonary artery smooth muscle cells in the presence of different concentrations of dermatan sulfate (DS). The viability of pulmonary artery smooth muscle cells with a silenced ARSB gene was stimulated by the dermatan sulfate. In contrast, the growth of pulmonary artery endothelial cells was not affected. As shown by microarray analysis, the expression of the arylsulfatase G (ARSG) in pulmonary artery smooth muscle cells increased after silencing the arylsulfatase B gene, but the expression of genes encoding other enzymes involved in the degradation of dermatan sulfate did not. The active site of arylsulfatase G closely resembles that of arylsulfatase B, as shown by molecular modeling. Together, these results lead us to propose that arylsulfatase G can take part in DS degradation; therefore, it can affect the functioning of the cells with a silenced arylsulfatase B gene.

Pingyangmycin inhibits glycosaminoglycan sulphation in both cancer cells and tumour tissues

Pingyangmycin is a clinically used anticancer drug and induces lung fibrosis in certain cancer patients. We previously reported that the negatively charged cell surface glycosaminoglycans are involved in the cellular uptake of the positively charged pingyangmycin. However, it is unknown if pingyangmycin affects glycosaminoglycan structures. Seven cell lines and a Lewis lung carcinoma‐injected C57BL/6 mouse model were used to understand the cytotoxicity of pingyangmycin and its effect on glycosaminoglycan biosynthesis. Stable isotope labelling coupled with LC/MS method was used to quantify glycosaminoglycan disaccharide compositions from pingyangmycin‐treated and untreated cell and tumour samples. Pingyangmycin reduced both chondroitin sulphate and heparan sulphate sulphation in cancer cells and in tumours. The effect was persistent at different pingyangmycin concentrations and at different exposure times. Moreover, the cytotoxicity of pingyangmycin was decreased in the presence of soluble glycosaminoglycans, in the glycosaminoglycan‐deficient cell line CHO745, and in the presence of chlorate. A flow cytometry‐based cell surface FGF/FGFR/glycosaminoglycan binding assay also showed that pingyangmycin changed cell surface glycosaminoglycan structures. Changes in the structures of glycosaminoglycans may be related to fibrosis induced by pingyangmycin in certain cancer patients.

Iduronate-2-Sulfatase-Regulated Dermatan Sulfate Levels Potentiate the Invasion of Breast Cancer Epithelia through Collagen Matrix

Cancer epithelia show elevation in levels of sulfated proteoglycans including dermatan sulfates (DS). The effect of increased DS on cancer cell behavior is still unclear. We hypothesized that decreased expression of the enzyme Iduronate-2-sulfatase (IDS) can lead to increased DS levels, which would enhance the invasion of cancer cells. Breast cancer sections shows depleted IDS levels in tumor epithelia, when compared with adjacent untransformed breast tissues. IDS signals showed a progressive decrease in the non-transformed HMLE, transformed but non-invasive MCF-7 and transformed and invasive MDA-MB-231 cells, respectively, when cultured on Type 1 collagen scaffolds. DS levels measured by ELISA increased in an inverse-association with IDS levels. Knockdown of IDS in MCF-7 epithelia also increased the levels of DS. MCF-7 cells with depleted IDS expression, when imaged using two photon-excited fluorescence and second harmonic generation microscopy, exhibited a mesenchymal morphology with multiple cytoplasmic projections compared with epithelioid control cells, interacted with their surrounding matrix, and showed increased invasion through Type 1 collagen matrices. Both these traits were phenocopied when control MCF-7 cells were cultivated on Type 1 collagen gels polymerized in the presence of DS. In monolayer cultures, DS had no effect on MCF-7 migration. In the context of our demonstration that DS enhances the elastic modulus of Type 1 collagen gels, we propose that a decrease of IDS expression leads to accumulation within cancer epithelia of DS: the latter remodels the collagen around cancer cells leading to changes in cell shape and invasiveness through fibrillar matrix milieu.

Radioprotective Effects of Dermatan Sulfate in a Preclinical Model of Oral Mucositis-Targeting Inflammation, Hypoxia and Junction Proteins without Stimulating Proliferation

Oral mucositis is the most frequently occurring early side effect of head-and-neck cancer radiotherapy. Systemic dermatan sulfate (DS) treatment revealed a significant radioprotective potential in a preclinical model of oral mucositis. This study was initiated to elucidate the mechanistic effects of DS in the same model. Irradiation comprised daily fractionated irradiation (5 × 3 Gy/week) over two weeks, either alone (IR) or in combination with daily dermatan sulfate treatment of 4 mg/kg (IR + DS). Groups of mice (n = 5) were sacrificed every second day over the course of 14 days in both experimental arms, their tongues excised and evaluated. The response to irradiation with and without DS was analyzed on a morphological (cell numbers, epithelial thickness) as well as on a functional (proliferation and expression of inflammation, hypoxia and epithelial junction markers) level. The mucoprotective activity of DS can be attributed to a combination of various effects, comprising increased expression of epithelial junctions, reduced inflammation and reduced hypoxia. No DS-mediated effect on proliferation was observed. DS demonstrated a significant mucositis-ameliorating activity and could provide a promising strategy for mucositis treatment, based on targeting specific, radiation-induced, mucositis-associated signaling without stimulating proliferation.

One-pot analysis of sulfated glycosaminoglycans

Routine isolation, estimation, and characterization of glycosaminoglycans (GAGs) is quite challenging. This is compounded by the fact that the analysis is technique-intensive and more often there will be a limitation on the quantity of GAGs available for various structural, functional and biological studies. In such a scenario, the sample which can be made available for estimation and elucidation of disaccharide composition and species composition as well remains a challenge. In the present study, we have determined the feasibility where isolated sulfated GAGs (sGAG) that is estimated by metachromasia is recovered for further analysis. sGAG-DMMB complex formed after estimation of sGAG by DMMB dye-binding assay was decomplexed and sGAGs were recovered. Recovered sGAGs were analysed by cellulose acetate membrane electrophoresis and taken up for disaccharide composition analysis by HPLC after fluorescent labelling. Good recovery of sGAGs after metachromasia was observed in all samples of varying levels of purity by this protocol. Further analysis using cellulose acetate membrane electrophoresis showed good separation between species of sGAGs namely chondroitin/dermatan sulfate and heparan sulfate, with comparatively lesser interference from hyaluronic acid, a non-sulfated GAG. Analysis of recovered sGAGs, specifically heparan sulfate by HPLC showed characteristic disaccharide composition akin to that of GAG obtained by the conventional protocol. Thus, in the present paper, we show that sGAG can be recovered in comparatively purer form after routine estimation and can be used for further analysis thus saving up on the precious sample.

Activation of Parathyroid Hormone 2 Receptor Induces Decorin Expression and Promotes Wound Repair

In this study, we report that TIP39, a parathyroid hormone ligand family member that was recently identified to be expressed in the skin, can induce decorin expression and enhance wound repair. Topical treatment of mice with TIP39 accelerated wound repair, whereas TIP39-deficient mice had delayed repair that was associated with formation of abnormal collagen bundles. To study the potential mechanism responsible for the action of TIP39 in the dermis, fibroblasts were cultured in three-dimensional collagen gels, a process that results in enhanced decorin expression unless activated to differentiate to adipocytes, whereupon these cells reduce expression of several proteoglycans, including decorin. Small interfering RNA-mediated silencing of parathyroid hormone 2 receptor (PTH2R), the receptor for TIP39, suppressed the expression of extracellular matrix-related genes, including decorin, collagens, fibronectin, and matrix metalloproteases. Skin wounds in TIP39^-/- mice had decreased decorin expression, and addition of TIP39 to cultured fibroblasts induced decorin and increased phosphorylation and nuclear translocation of CREB. Fibroblasts differentiated to adipocytes and treated with TIP39 also showed increased decorin and production of chondroitin sulfate. Furthermore, the skin of PTH2R^-/- mice showed abnormal extracellular matrix structure, decreased decorin expression, and skin hardness. Thus, the TIP39-PTH2R system appears to be a previously unrecognized mechanism for regulation of extracellular matrix formation and wound repair.

The parathyroid hormone family member TIP39 interacts with sarco/endoplasmic reticulum Ca2+ - ATPase activity by influencing calcium homoeostasis

Darier disease (DD) is a genetic skin disease that is associated with mutations in the ATP2A2 gene encoding the type 2 sarco/endoplasmic reticulum (ER) Ca²⁺ - ATPase (SERCA2). Mutations of this gene result in alterations of calcium homoeostasis, abnormal epidermal adhesion and dyskeratosis. Silencing of ATP2A2 in monolayer cell culture of keratinocytes reduces desmoplakin expression at the borders of cells and impacts cell adhesion. Here, we report establishment of a three-dimensional (3D) epidermal model of DD and use this model to evaluate peptide therapy with tuberoinfundibular peptide of 39 residues (TIP39) to normalize calcium transport. Gene silencing of ATP2A2 in keratinocytes grown in a 3D model resulted in dyskeratosis, partial parakeratosis and suprabasal clefts that resembled the histological changes seen in skin biopsies from patients with DD. TIP39, a peptide recently identified as a regulator of keratinocyte calcium transport, was then applied to this ATP2A2-silenced 3D epidermal model. In normal keratinocytes, TIP39 increased [Ca²⁺ ]_i through the inositol trisphosphate (IP3) receptor pathway and stimulated differentiation. In monolayer ATP2A2-silenced keratinocytes, although TIP39 increased cytosolic calcium from the ER, the response was incomplete compared with its control. TIP39 was observed to reduce intercellular clefts of the gene-silenced epidermal model but did not significantly upregulate keratinocyte differentiation genes such as keratin 10 and filaggrin. These findings indicate that TIP39 is a modulator of ER calcium signalling and may be used as a potential strategy for improving aspects of DD.

Upregulations of metallothionein gene expressions and tolerance to heavy metal toxicity by three dimensional cultivation of HepG2 cells on VECELL 3-D inserts

The VECELL 3-D insert is a new culture scaffold consisting of collagen-coated ePTFE (expanded polytetrafluoroethylene) mesh. We analyzed the effects of VECELL 3-D inserts on the functionality of HepG2, a human hepatocellular carcinoma cell line. HepG2 cells cultured on VECELL 3-D inserts maintained a round shape, while those cultured on a standard culture plate or collagen-coated cell culture plate showed a flattened and cubic epithelial-like shape. HepG2 cells cultured on VECELL 3-D inserts had showed upregulated expression of metallothionein genes and in turn a higher tolerance to toxicity induced by heavy metals. These results suggest that HepG2 cell functions were changed by the cell morphology that is induced by culturing on a VECELL 3-D insert.

Biological functions of iduronic acid in chondroitin/dermatan sulfate

The presence of iduronic acid in chondroitin/dermatan sulfate changes the properties of the polysaccharides because it generates a more flexible chain with increased binding potentials. Iduronic acid in chondroitin/dermatan sulfate influences multiple cellular properties, such as migration, proliferation, differentiation, angiogenesis and the regulation of cytokine/growth factor activities. Under pathological conditions such as wound healing, inflammation and cancer, iduronic acid has diverse regulatory functions. Iduronic acid is formed by two epimerases (i.e. dermatan sulfate epimerase 1 and 2) that have different tissue distribution and properties. The role of iduronic acid in chondroitin/dermatan sulfate is highlighted by the vast changes in connective tissue features in patients with a new type of Ehler–Danlos syndrome: adducted thumb-clubfoot syndrome. Future research aims to understand the roles of the two epimerases and their interplay with the sulfotransferases involved in chondroitin sulfate/dermatan sulfate biosynthesis. Furthermore, a better definition of chondroitin/dermatan sulfate functions using different knockout models is needed. In this review, we focus on the two enzymes responsible for iduronic acid formation, as well as the role of iduronic acid in health and disease.

Iduronic acid in chondroitin/dermatan sulfate: biosynthesis and biological function

The ability of chondroitin/dermatan sulfate (CS/DS) to convey biological information is enriched by the presence of iduronic acid. DS-epimerases 1 and 2 (DS-epi1 and 2), in conjunction with DS-4-O-sulfotransferase 1, are the enzymes responsible for iduronic acid biosynthesis and will be the major focus of this review. CS/DS proteoglycans (CS/DS-PGs) are ubiquitously found in connective tissues, basement membranes, and cell surfaces or are stored intracellularly. Such wide distribution reflects the variety of biological roles in which they are involved, from extracellular matrix organization to regulation of processes such as proliferation, migration, adhesion, and differentiation. They play roles in inflammation, angiogenesis, coagulation, immunity, and wound healing. Such versatility is achieved thanks to their variable composition, both in terms of protein core and the fine structure of the CS/DS chains. Excellent reviews have been published on the collective and individual functions of each CS/DS-PG. This short review presents the biosynthesis and functions of iduronic acid-containing structures, also as revealed by the analysis of the DS-epi1- and 2-deficient mouse models.

Sugar-coating wound repair: a review of FGF-10 and dermatan sulfate in wound healing and their potential application in burn wounds

Thousands of patients suffer from burn injuries each year, yet few therapies have been developed to accelerate the wound healing process. Most fibroblast growth factors (FGFs) have been extensively evaluated but only a few have been found to participate in the wound healing process. In particular, FGF-10 is robustly increased in the wound microenvironment after injury and has demonstrated some ability to promote wound healing in vitro and in vivo. Glycosaminoglycans are linear carbohydrates that participate in wound repair by influencing cytokine/growth factor localization and interaction with cognate receptors. Dermatan sulfate (DS) is the most abundant glycosaminoglycan in human wound fluid and has been postulated to be directly involved in the healing process. Recently, the combination of FGF-10 and DS demonstrated the potential to accelerate wound healing via increased keratinocyte proliferation and migration. Based on these preliminary studies, DS may serve as a cofactor for FGF-10, and together they are likely to expedite the healing process by stimulating keratinocyte activity. As a specific subtype of wounds, the overall healing process of burn injuries does not significantly differ from other types of wounds, where optimal repair results in matrix regeneration and complete reepithelialization. At present, standard burn treatment primarily involves topical application of antimicrobial agents, while no routine therapies target acceleration of reepithelialization, the key to wound closure. Thus, this novel therapeutic combination could be used in conjunction with some of the current therapies, but it would have the unique ability to initiate wound healing by stimulating keratinocyte epithelialization.

Exogenous addition of a C-xylopyranoside derivative stimulates keratinocyte dermatan sulfate synthesis and promotes migration

As C-Xyloside has been suggested to be an initiator of glycosaminoglycan (GAG) synthesis, and GAGs such as Dermatan sulfate (DS) are potent enhancers of fibroblast growth factor (FGF)--10 action, we investigated if a C-Xylopyranoside derivative, (C-β-D-xylopyranoside-2-hydroxy-propane, C-Xyloside), could promote DS production by cultured normal human keratinocytes, how this occurs and if C-Xyloside could also stimulate FGF-dependent cell migration and proliferation. C-Xyloside-treated keratinocytes greatly increased secretion of total sulfated GAGs. Majority of the induced GAG was chondroitin sulfate/dermatan sulfate (CS/DS) of which the major secreted GAG was DS. Cells lacking xylosyltransferase enzymatic activity demonstrated that C-Xyloside was able to stimulate GAG synthesis without addition to core proteins. Consistent with the observed increase in DS, keratinocytes treated with C-Xyloside showed enhanced migration in response to FGF-10 and secreted into their culture media GAGs that promoted FGF-10-dependent cellular proliferation. These results indicate that C-Xyloside may enhance epithelial repair by serving as an initiator of DS synthesis.

Global gene expression changes including drug metabolism and disposition induced by three-dimensional culture of HepG2 cells-Involvement of microtubules

Constitutive upregulation and a higher degree of induction of drug metabolism and disposition-related genes were found in a three-dimensional HepG2 culture. The upregulated genes are believed to be regulated by different regulatory factors. Global gene expression analysis using the Affymetrix GeneChip indicated that altered expression of microtubule-related genes may change the expressed levels of drug metabolizing and disposition genes. Stabilization of microtubule molecules with docetaxel, a tubulin-stabilizing agent, in the two-dimensional culture showed gene expression patterns similar to those found in the three-dimensional culture, indicating that the culture environment affects drug metabolism functions in HepG2 cells.

The modulation of collagen fibril assembly and its structure by decorin: an electron microscopic study

The present study was carried out to determine the effect of decorin in the process of collagen assembly. Collagen fibrils were obtained in vitro by aggregation from commercialized acid-soluble type I collagen with the addition of different concentrations of decorin (0-25 microg/ml). All specimens were observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The distribution of collagen fibril diameters was also analyzed by TEM. In samples without or with low concentrations of decorin, highly porous collagen fiber networks were formed. On the other hand, dense networks were observed in samples treated with high concentrations of decorin. The influence of decorin secreted by cells on collagen fibrils was observed by SEM, and the fiber network elasticity was measured using a rheometer. SEM images showed that collagen fiber networks without fibroblasts were much looser than those cultured with normal fibroblasts. The networks cultured with the fibroblasts were composed of straight fibers with large diameters. On the other hand, collagen fiber networks cultured with siRNA-decorin-transfected (siDT) fibroblasts had loose, meandering fibers with small diameters. The elasticity of collagen fiber networks cultured with untransfected fibroblasts showed no significant difference over the 7-day incubation period. However, significantly lower elastic values were obtained for collagen fiber networks treated with siDT cells on days 3 and 7. In addition, after treatment with 5.0 or 25 microg/ml decorin, the l collagen fiber networks cultured with siDT cells exhibited an altered structure that showed a dense structure similar to that of the fiber networks cultured with untransfected fibroblasts. In conclusion, this in vitro study showed that decorin is a regulatory and architecturally small leucine-rich repeat proteoglycan in the process of collagen fibril assembly.

Glycosylation analysis of glycoproteins and proteoglycans using capillary electrophoresis-mass spectrometry strategies

This review highlights recent developments in glycosylation analysis by modern MS in combination with CE based preseparation. Focused on CE-MS strategies aimed for glycotyping, the review addresses the detailed glycoform analysis of glycoproteins, glycopeptides, and proteoglycans. Glycoform analysis in the context of modern glycoproteomics is briefly addressed, as well. CZE, CIEF, and frontal analysis CE approaches hyphenated to high-resolution multistage MS for the detailed analysis of protein-linked glycan structures are overviewed in a comprehensive way. Advantages and limitations of various methodological approaches and techniques as well as mass spectrometric instrumentation are discussed in the particular context of glycoanalysis.

Thermodynamic studies and binding mechanisms of cell-penetrating peptides with lipids and glycosaminoglycans

Cell-penetrating peptides (CPPs) traverse the membrane of biological cells at low micromolar concentrations and are able to take various cargo molecules along with. Despite large differences in their chemical structure, CPPs share the structural similarity of a high cationic charge density. This property confers to them the ability to bind electrostatically membrane constituents such as anionic lipids and glycosaminoglycans (GAGs). Controversies exist, however, about the biological response after the interaction of CPPs with such membrane constituents. Present review compares thermodynamic binding studies with conditions of the biological CPP uptake. It becomes evident that CPPs enter biological cells by different and probably competing mechanisms. For example, some amphipathic CPPs traverse pure lipid model membranes at low micromolar concentrations--at least in the absence of cargos. In contrast, no direct translocation at these conditions is observed for non-amphipathic CPPs. Finally, CPPs bind GAGs at low micromolar concentrations with potential consequences for endocytotic pathways.

A unique thymic fibroblast population revealed by the monoclonal antibody MTS-15

T cell differentiation in the thymus is dependent upon signals from thymic stromal cells. Most studies into the nature of these signals have focused only on the support provided by the thymic epithelium, but there is an emerging view that other stromal cells such as mesenchymal fibroblasts may also be involved. Study of the latter has been hindered by a lack of appropriate markers, particularly those allowing their isolation. In this study, we describe a new surface marker of thymic stroma, MTS-15, and demonstrate its specificity for fibroblasts and a subset of endothelial cells. Coculture experiments showed that the determinant could be transferred between cells. Extensive biochemical analysis demonstrated that the Ag bound by MTS-15 was the glycosphingolipid Forssman determinant, consistent with the distribution observed. Transcriptional analysis of purified MTS-15(+) thymic fibroblasts revealed a unique expression profile for a number of chemokines and growth factors important to thymocyte and epithelial cell development. In a model of cyclophosphamide-induced thymic involution and regeneration, fibroblasts were found to expand extensively and express growth factors important to epithelial proliferation and increased T cell production just before thymic regeneration. Overall, this study identifies a useful marker of thymic fibroblasts and highlights this subpopulation as a key player in thymic function by virtue of their support of both thymocytes and epithelial cells.

Shedding of Syndecan-1 by Stromal Fibroblasts Stimulates Human Breast Cancer Cell Proliferation via FGF2 Activation

The cell surface heparan sulfate proteoglycan syndecan-1 is induced in stromal fibroblasts of breast carcinomas and participates in a reciprocal feedback loop, which stimulates carcinoma cell growth in vitro and in vivo. To define the molecular mechanism of carcinoma growth stimulation, a three-dimensional co-culture model was developed that combines T47D breast carcinoma cells with immortalized human mammary fibroblasts in collagen gels. By silencing endogenous syndecan-1 induction with short interfering RNA and expressing mutant murine syndecan-1 constructs, it was determined that carcinoma cell mitogenesis required proteolytic shedding of syndecan-1 from the fibroblast surface. The paracrine growth signal was mediated by the syndecan-1 heparan lfate chains rather than the ectodomain of the core protein and required fibroblast growth factor 2 and stroma-derived factor 1. This paracrine pathway may provide an opportunity for the therapeutic disruption of stromaepithelial signaling.

A new microrheometric approach reveals individual and cooperative roles for TGF-beta1 and IL-1beta in fibroblast-mediated stiffening of collagen gels

The stiffness of the extracellular matrix can profoundly influence cell and tissue behaviors. Thus there is an emerging emphasis on understanding how matrix mechanical environments are established, regulated, and modified. Here we develop a microrheometric assay to measure the mechanical properties of a model extracellular matrix (type I collagen gel) and use it to explore cytokine-induced, cell-mediated changes in matrix mechanical properties. The microrheometric assay uses micron-scale ferrimagnetic beads embedded within collagen gels during fibrillogenesis. The beads are magnetized, then subjected to a twisting field, with the aggregate rotation of the beads measured by a magnetometer. The degree of bead rotation reflects the stiffness of the surrounding matrix. We show that the microscale assay provides stiffness measures for collagen gels comparable to those obtained with standard macroscale rheometry. To demonstrate the utility of the assay for biological discovery, we measure stiffness changes in fibroblast-populated collagen gels exposed to three concentrations of six cytokines over 2 to 14 days. Among the cytokines tested, transforming growth factor-beta1 and interleukin-1beta enhanced matrix stiffness, and together exerted cooperative effects on cellular modulation of matrix mechanics. The microrheometry approach developed here should accelerate the discovery of biological pathways orchestrating cellular modulation of matrix mechanics.

Increased deposition of sulfated glycosaminoglycans in human patellar tendinopathy

OBJECTIVE

To investigate if the increased proteoglycans in patellar tendinopathy involves a qualitative change in the types of proteoglycans.

DESIGN

This is an observational study based on the biochemical analysis of proteoglycans.

SETTING

: University Teaching Hospital.

PATIENTS

Patellar tendon samples from 12 patients with patellar tendinopathy and 12 healthy controls were collected and proteoglycans were extracted for biochemical analyses. All patients fulfilled the diagnostic criteria of having patellar tendinopathy with well-defined clinical features, more than 6 months of insufficient nonoperative treatment including physiotherapeutic modalities, and verification by ultrasound or magnetic resonance imaging. Twelve control subjects, 10 men and 2 women with an average age of 31 years (range 16 to 38 years), represented patients with anterior cruciate ligament deficiency who were operated on using the healthy patellar tendon as an autograft. The control subjects had no previous history or clinical signs of patellar tendon injury.

INTERVENTIONS

The independent variable is the presence of pathological conditions of patellar tendinopathy.

MAIN OUTCOME MEASUREMENTS

The dependent variables include the electromobility of proteoglycans, staining intensity of proteoglycan core proteins, and the tissue content of glycosaminoglycan disaccharides.

RESULTS

The results indicated that the increased proteoglycans in pathological tissues also exhibited qualitative changes as compared to those in healthy patellar tendons. Dermatan monosulfates were significantly increased in the proteoglycans extracted from the pathological tissues of patellar tendinopathy.

CONCLUSIONS

Our results indicate that proteoglycans deposited in the pathological tissues of patellar tendinopathy were oversulfated as compared to healthy tendons, which may represent a new pathological attribute for the understanding of chronic pain in patellar tendinopathy.

Glypican-1 is frequently overexpressed in human gliomas and enhances FGF-2 signaling in glioma cells

Signaling by fibroblast growth factor 2 (FGF-2), an autocrine stimulator of glioma growth, is regulated by heparan sulfate proteoglycans (HSPGs) via a ternary complex with FGF-2 and the FGF receptor (FGFR). To characterize glioma growth signaling, we examined whether altered HSPGs contribute to loss of growth control in gliomas. In a screen of five human glioma cell lines, U118 and U251 cell HSPGs activated FGF-2 signaling via FGFR1c. The direct comparison of U251 glioma cells with normal astrocyte HSPGs demonstrated that the glioma HSPGs had a significantly elevated ability to promote FGF-2-dependent mitogenic signaling via FGFR1c. This enhanced activity correlated with a higher level of overall sulfation, specifically the abundance of 2S- and 6S-containing disaccharides. Glioma cell expression of the cell-surface HSPG glypican-1 closely mirrored the FGF-2 coactivator activity. Furthermore, forced expression of glypican-1 in (glypican-1-deficient) U87 glioma cells enhanced their FGF-2 response. Immunohistochemical analysis revealed a highly significant overexpression of glypican-1 in human astrocytoma and oligodendroglioma samples compared with nonneoplastic gliosis. In summary, these observations suggest that altered HSPGs contribute to enhanced signaling of FGF-2 via FGFR1c in gliomas with glypican-1 playing a significant role in this mitogenic pathway.

Defective glycosylation of decorin and biglycan, altered collagen structure, and abnormal phenotype of the skin fibroblasts of an Ehlers–Danlos syndrome patient carrying the novel Arg270Cys substitution in galactosyltransferase I (β4GalT-7)

The Ehlers-Danlos syndrome (EDS) is a heterogeneous group of connective tissue disorders affecting skin and joint function. Molecular defects in extracellular matrix proteins, including collagen (type I, III, and V) and tenascin X are associated with different forms of EDS. Compound heterozygous mutations in the B4GALT7 gene, resulting in aberrant glycosylation of the dermatan sulfate proteoglycan decorin, had been described in a single patient affected with the progeroid form of EDS. We have studied the molecular phenotype of decorin, biglycan, and collagen type I containing fibrils in skin fibroblasts of a patient carrying the novel homozygous C808T point mutation in the B4GALT7 gene, which causes an Arg270Cys substitution in beta4GalT-7. Compared to control fibroblasts, galactosyltransferase activity in beta4GalT-7(Arg270Cys) cells was approximately three times reduced over a temperature range of 25-41 degrees C. Pulse-chase experiments and confocal microscopy demonstrated that synthesis and secretion of decorin were normal in beta4GalT-7(Arg270Cys) cells. However, about 50% of decorin were synthesized as a protein core in addition to its proteoglycan form. Biglycan was found in a monoglycanated form in addition to its mature form. Glycosaminoglycan chains were of the dermatan/chondroitin sulfate type both in beta4GalT-7(Arg270Cys) and control cells, and epimerization was reduced for decorin and biglycan. Compared to control cells, beta4GalT-7(Arg270Cys) cells showed altered, highly spread or stretched phenotypes and decreased proliferation rates. At the ultrastructural level, an intracellular accumulation of multiple secondary lysosomes and degenerative vacuoles was seen in beta4GalT-7(Arg270Cys) cells. Furthermore, the collagen suprastructures were altered in the beta4GalT-7(Arg270Cys) cells. The reduced beta4GalT-7 activity resulting in defective glycosylation of decorin and biglycan may be responsible for the complex molecular pathology in beta4GalT-7 deficient EDS patients, given the role of these proteoglycans in bone formation, collagen fibrillogenesis, and skeletal muscle development.

Mechanobiology in the third dimension

Cells are mechanically coupled to their extracellular environments, which play critical roles in both communicating the state of the mechanical environment to the cell as well as in mediating cellular response to a variety of stimuli. Along with the molecular composition and mechanical properties of the extracellular matrix (ECM), recent work has demonstrated the importance of dimensionality in cell-ECM associations for controlling the sensitive communication between cells and the ECM. Matrix forces are generally transmitted to cells differently when the cells are on two-dimensional (2D) vs. within three-dimensional (3D) matrices, and cells in 3D environments may experience mechanical signaling that is unique vis-à-vis cells in 2D environments, such as the recently described 3D-matrix adhesion assemblies. This review examines how the dimensionality of the extracellular environment can affect in vitro cell mechanobiology, focusing on collagen and fibrin systems.

Extracellular matrix modulates expression of cell-surface proteoglycan genes in fibroblasts

Cell-surface proteoglycans are involved in many functions, including interactions with components of the extracellular microenvironment. They also act as coreceptors that bind and modify the actions of various growth factors, cytokines, and the extracellular matrix (ECM). This study investigated the regulation by the ECM of the expression of cell-surface proteoglycans (CD44, syndecan-1-4, betaglycan, glypican-1). We examined the changes in the expression levels of cell-surface proteoglycan genes in intact tendon, monolayer culture, and under various culture conditions. There was a significant increase in the expression of CD44 and syndecan-4 mRNAs during cell isolation from the tendon. With the switch to a 3D culture environment, there was a significant increase in the expression of CD44 at each passage point relative to its expression in 2D at those passage points. Syndecan-4 mRNA also increased steadily at each passage point in 3D culture environment. This influence on cell surface proteoglycans gene expression may indicate that collagen gel culture mimics in vivo tendon environment. This study provides further insight into the regulation of cell-surface proteoglycans in ligament and tendon fibroblasts by the ECM and 3D culture conditions.

Serine proteinases of the human body louse (Pediculus humanus): sequence characterization and expression patterns

After the previous characterization of one trypsin gene (Try1) of the human body louse Pediculus humanus, genes encoding a second trypsin (Try2) and a chymotrypsin (Chy1) have been cloned using degenerate serine proteinase primers and 5'- and 3'-RACE, and sequenced. The deduced 259 and 267 amino acid sequences of Try2 and Chy1 show an identity of 33%-40% to trypsinogens and chymotrypsinogens of other insects. Considering previously published partial sequences, P. humanus possesses at least one Try1 gene, five variants/isoforms of Try2 and six variants/isoforms of Chy1. The genomic DNA of Try2 contains three introns and Chy1 contains five introns. Using whole mount in situ hybridization, gene expression of Try1, Try2 and Chy1 has been localized not only in the distensible anterior region of the midgut of lice but sometimes also in the area following the distensible region. The Try2 gene was always expressed at much lower levels than Try1 or Chy1. This lower expression, the constitutive expression of Try1 and Chy1 at 1, 2, 6, 12 and 24 h after feeding of adults and the regional differences have been verified in quantitative real-time PCR.

A physiologic three-dimensional cell culture system to investigate the role of decorin in matrix organisation and cell survival

In vivo cells exist in a three-dimensional environment generated and maintained by multiple cell-cell and cell-matrix interactions. Proteoglycans, like decorin, affect these complex interactions. Thus, we sought to investigate the role of decorin in a three-dimensional environment where the matrix was generated over time by decorin-deficient fibroblasts in the presence of L-ascorbic acid 2-phosphate. The cells were viable and proliferated in response to FGF2. Decorin was incorporated in the matrix and caused a approximately 2 nm shift in the average diameter of the collagen fibrils, and the range and distribution of the fibrils became narrower and more uniform. Although there were no appreciable changes in collagen composition, we found that exogenous decorin induced the de novo synthesis of collagen I and V and cross-linked beta(I). In the early phases of the three-dimensional culture, decorin reduced apoptosis. However, following the establishment of a three-dimensional matrix, the cells did not require decorin for their survival.