Syndecan-4 inhibition attenuates cartilage degeneration in temporomandibular joint osteoarthritis.

BACKGROUND: Syndecan 4 (SDC4), a type I transmembrane proteoglycan, serves as a critical link between chondrocytes and the extracellular matrix. OBJECTIVE: This study aimed to explore the role of SDC4 in cartilage degeneration of temporomandibular joint osteoathritis (TMJOA). METHODS: Condylar chondrocytes were stimulated with varying concentrations of recombinant rat interleukin-1ß (rrIL-1ß) and SDC4 small interfering RNA (si-SDC4). Anti-SDC4 ectodomain-specific antibodies or IgG were intra-articularly administrated in a TMJOA model rats. SDC4 conditional knockout (SDC4-cKO) and Sdc4flox/flox mice were induced TMJOA. Cartilage degeneration was assessed using haematoxylin & eosin (H&E) and safranin O (SO) staining. Protein levels of SDC4, matrix metalloproteinases (MMPs), a disintegrin and metalloproteinase with a thrombospondin motifs 5 (ADAMTS5), tumour necrosis factor α (TNFα), type II collagen (Col-II), aggrecan (ACAN), cleaved caspase 3 (CASP3), Ki67 and related pathways in condylar cartilage were evaluated by immunohistochemical (IHC) staining or western blot assays. RESULTS: SDC4 expression was evidently increased in MIA-model animals compared to control groups. rrIL-1ß stimulation increased the expression of SDC4, MMP3 and ADAMTS5 expression in chondrocytes, while decreasing the expression of Col-II. These effects were reversed by si-SDC4 in vitro. In vivo, SDC4 blockade reduced the death of chondrocytes and the loss of cartilage matrix, which was evidenced by increased expression of Col-II and ACAN, and a decrease in SDC4, MMP13 and cleaved-CASP3-positive cells. Furthermore, the protein levels of ACAN and Ki67 were elevated, and the ERK1/2 and P38 signalling pathways were activated following SDC4 inhibition. CONCLUSIONS: SDC4 inhibition significantly ameliorates condylar cartilage degeneration, which was mediated, at least partly, through P38 and ERK1/2 signalling. Inhibition of SDC4 may be of great value for the treatment of TMJOA.

Syndecan-4 Promotes Epithelial Tumor Cells Spreading and Regulates the Turnover of PKCα Activity under Mechanical Stimulation on the Elastomeric Substrates.

BACKGROUND: Heparan sulfate proteoglycans (HSPGs) at the cell surface play an important role in cell adhesion, spreading, formation of focal adhesion complexes (FACs), and sensing mechanical stress. Syndecans are members of the HSPGs family and are highly expressed in various tumor cells. Syndecan-4 (SDC4) is a unique member of syndecans that activates protein kinase C alpha (PKCα). However, syndecan-4 in tumor cells development is not clear when receiving mechanical stress. Aims: Here we investigate the role of syndecan-4 in tumor cells spreading and its downstream kinases under mechanical stimulation. METHODS: Epithelial tumor cells were seeded onto elastomeric polydimethylsiloxane (PDMS) membranes coated with poly-L-lysine (Pl), fibronectin (Fn), or anti-SDC4 antibody and stretched with a modified pressure-driven cell-stretching (PreCS) device. RESULTS: When cells received mechanical stimulation, engagement of syndecan-4 promoted the phosphorylation of focal adhesion kinase (FAK) at tyrosine 397 and PKCα at serine 657. Furthermore, we analyzed the cell contractility marker-myosin light chain 2 (MLC2) in 30 min time courses. The levels of phosphorylated MLC2 at serine19 were augmented through ligations of syndecan-4 but not integrin binding motif (RGD) at 10 min mechanical stimulation and were suppressed at 30 min and this phenomenon was associated with the activity of PKCα. CONCLUSION: Our data demonstrate that syndecan-4 is essential for transmitting the mechanotransduction signals via activation of PKCα and is important for tumor cells spreading, assembly of actin cytoskeleton and cell contractility.

Probing the interaction between heparan sulfate proteoglycan with biologically relevant molecules in mimetic models for cell membranes: a Langmuir film study.

Investigating the role of proteoglycans associated to cell membranes is fundamental to comprehend biochemical process that occurs at the level of membrane surfaces. In this paper, we exploit syndecan-4, a heparan sulfate proteoglycan obtained from cell cultures, in lipid Langmuir monolayers at the air-water interface. The monolayer served as a model for half a membrane, and the molecular interactions involved could be evaluated with tensiometry and vibrational spectroscopy techniques. Polarization-modulation infrared reflection-absorption spectroscopy (PM-IRRAS) employed in a constant surface pressure regime showed that the main chemical groups for syndecan-4 were present at the air-water interface. Subsequent monolayer decompression and compression showed surface pressure-area isotherms with a large expansion for the lipid monolayers interacting with the cell culture reported to over-express syndecan-4, which was also an indication that the proteoglycan was inserted in the lipid monolayer. The introduction of biological molecules with affinity for syndecam-4, such as growth factors, which present a key role in biochemical process of cell signaling, changed the surface properties of the hybrid film, leading to a model, by which the growth factor binds to the sulfate groups present in the heparan sulfate chains. The polypeptide moiety of syndecan-4 responds to this interaction changing its conformation, which leads to lipid film relaxation and further monolayer condensation.

Syndecan 4 contributes to osteoclast differentiation induced by RANKL through enhancing autophagy.

Periodontitis is a common chronic disease. Osteoclast differentiation contributes to alveolar bone resorption which is a distinct phenomenon during periodontitis. Syndecan 4 (SDC4), a member of the syndecan family, was found to be highly expressed during periodontitis. However, little is known about its role in periodontitis. Herein, we explored the role of SDC4 in osteoclast differentiation. An experimental periodontitis rat model was established by ligating the right first molar. The SDC4 expression in periodontium was detected by western blot and immunofluorescence. Our study demonstrated that SDC4 was highly expressed in the periodontium of periodontitis rats. It was positively transcriptionally regulated by NF-κB. SDC4 silencing abrogated osteoclast differentiation induced by RANKL, while SDC4 overexpression enhanced osteoclast differentiation. Moreover, SDC4 enhanced autophagy induced by RANKL. 3-MA, an autophagy inhibitor, was employed to explore whether SDC4 impacts osteoclast differentiation through activating autophagy. Treatment with 3-MA abolished osteoclast differentiation which was enhanced by SDC4, indicating that SDC4 promotes osteoclast differentiation through activating autophagy. This study reveals that SDC4 may contribute to osteoclast differentiation during periodontitis through activating autophagy. It sheds light on the important role of SDC4 in periodontitis.

Small changes in PDMMLA structure influence the adsorption behavior of ECM proteins and syndecan-4 on PDMMLA derivative surfaces: Experimental validation by tensiometric surface force measurements.

Cardiovascular diseases are the leading cause of death around the world according to the World Health Organization. In-stent restenosis is an inflammatory response of the immune system to endovascular stent implantation in atherosclerotic patients. Biocompatible and biodegradable polymers are of great interest in this field in order to limit the side effects of stent treatments. Poly([R,S]-3,3-dimethylmalic acid) (PDMMLA) is a new biodegradable statistical polyester which presents promising properties as a stent coating. In this work, we studied by dynamic tensiometry, the adhesion of extracellular matrix proteins (bovine serum albumin, fibronectin, fibrinogen, and vitronectin) and plasma membrane proteoglycan (syndecan-4) on three PDMMLA derivatives with different hydrophilicity levels. The results show that proteins have different adhesion profiles and affinity on these surfaces. They show similar behavior on the most hydrophilic surface, making hydrophilic, ionic and hydrogen type bonds. Then we compared each protein's individual profile to that of a mixture of all studied proteins. The comparison shows that vitronectin and syndecan-4 are the quantitatively dominating proteins adsorbed by specific interactions. Based on the results from previous studies, this work allowed us to identify the most important PDMMLA surface as a promising biomaterial for bioactive stent-coating.

The spatiotemporal expression pattern of Syndecans in murine embryonic teeth.

The hierarchical interactions between the dental epithelium and dental mesenchyme represent a common paradigm for organogenesis. During tooth development, various morphogens interact with extracellular components in the extracellular matrix and on the cell surfaces to transmit regulatory signaling into cells. We recently found pivotal roles of FAM20B-catalyzed proteoglycans in the control of murine tooth number at embryonic stages. However, the expression pattern of proteoglycans in embryonic teeth has not been well understood. We extracted total RNA from E14.5 murine tooth germs for semi-quantitative RT-PCR analysis of 29 proteoglycans, and identified 23 of them in the embryonic teeth. As a major subfamily of FAM20B-catalyzed proteoglycans, Syndecans are important candidates being potentially involved in the tooth development of mice. We examined the expression pattern of Syndecans in embryonic teeth using in situ hybridization (ISH) and immunohistochemistry (IHC) approaches. Syndecan-1 is mainly present in the dental mesenchyme at early embryonic stages. Subsequently, its expression expands to both dental epithelium and dental mesenchyme. Syndecan-2 is strongly expressed in the dental mesenchyme at early embryonic stages, then shifts to the stratum intermedium and inner dental epithelium at cap stages. Syndecan-3 shows a gradually increased expression that initially in the dental epithelium of both incisors and molars and then in the inner dental epithelium and stratum intermedium in molars alone. Syndecan-4 is localized in the dental epithelium in incisors and the dental follicle mesenchyme in molars at early cap stage. The spatiotemporal expression pattern of Syndecans in murine embryonic teeth suggest potential roles of these proteoglycans in murine tooth morphogenesis.

Heparan sulfate expression in polarized epithelial cells: the apical sorting of glypican (GPI-anchored proteoglycan) is inversely related to its heparan sulfate content.

Several processes that occur in the luminal compartments of the tissues are modulated by heparin-like polysaccharides. To identify proteins responsible for the expression of heparan sulfate at the apex of polarized cells, we investigated the polarity of the expression of the cell surface heparan sulfate proteoglycans in CaCo-2 cells. Domain-specific biotinylation of the apical and basolateral membranes of these cells identified glypican, a GPI-linked heparan sulfate proteoglycan, as the major source of apical heparan sulfate. Yet, most of this proteoglycan was expressed at the basolateral surface, an unexpected finding for a glypiated protein. Metabolic labeling and chase experiments indicated that sorting mechanisms, rather than differential turnover, accounted for this bipolar expression of glypican. Chlorate treatment did not affect the polarity of the expression of glypican in CaCo-2 cells, and transfectant MDCK cells expressed wild-type glypican and a syndecan-4/glypican chimera also in an essentially unpolarized fashion. Yet, complete removal of the heparan sulfate glycanation sites from the glypican core protein resulted in the nearly exclusive apical targeting of glypican in the transfectants, whereas two- and one-chain mutant forms had intermediate distributions. These results indicate that glypican accounts for the expression of apical heparan sulfate, but that glycanation of the core protein antagonizes the activity of the apical sorting signal conveyed by the GPI anchor of this proteoglycan. A possible implication of these findings is that heparan sulfate glycanation may be a determinant of the subcellular expression of glypican. Alternatively, inverse glycanation-apical sorting relationships in glypican may insure near constant deliveries of HS to the apical compartment, or "active" GPI-mediated entry of heparan sulfate into apical membrane compartments may require the overriding of this antagonizing effect of the heparan sulfate chains.

Fibroblast growth factor-specific modulation of cellular response by syndecan-4.

Proteoglycans participate in growth factor interaction with the cell surface through their heparan sulfate chains (HS), but it is not known if they are otherwise involved in growth factor signaling. It appears now that the syndecan-4 core protein, a transmembrane proteoglycan shown previously to bind phosphatidylinositol 4,5-bisphosphate (PIP(2)) and activate PKC alpha, participates in mediating the effects of fibroblast growth factor (FGF)2 on cell function. Mutations in the cytoplasmic tail of syndecan-4 that either reduced its affinity to PIP(2) (PIP(2)(-)) or disrupted its postsynaptic density 95, disk large, zona occludens-1 (PDZ)-dependent binding (PDZ(-)) produced a FGF2-specific dominant negative phenotype in endothelial cells as evidenced by the marked decline of their migration and proliferation rates and the impairment of their capacity to form tubes. In both cases, the molecular mechanism was determined to consist of a decrease in the syndecan-4-dependent activation of PKC alpha. This decrease was caused either by inhibition of FGF2-induced syndecan-4 dephosphorylation in the case of the PDZ(-) mutation or by disruption of basolateral targeting of syndecan-4 and its associated PDZ-dependent complex in the case of the PIP(2)(-) mutation. These results suggest that PKCalpha activation and PDZ-mediated formation of a serine/threonine phosphatase-containing complex by syndecan-4 are downstream events of FGF2 signaling.

Beyond RGD; nanoclusters of syndecan- and integrin-binding ligands synergistically enhance cell/material interactions.

Biomaterials are a powerful platform for directing cellular behaviour. Herein, we employed a biomimetic strategy to synthesize a low-fouling polymer functionalized with nano-scale clusters of ligands that bind both integrin and syndecan-4 receptors, as both receptor types are critical in focal adhesion signalling and mechanotransduction. Our results demonstrate that the presence of both ligand types synergistically increases the adhesion of human umbilical vein endothelial cells (more than a two fold increase after 4 h) and increases the rate of surface endothelialization compared to surfaces functionalized with only one ligand type. Additionally, we observe that the mixed population of ligands regulates endothelial cell migration, likely due to improved focal adhesion formation as observed through confocal microscopy. Furthermore, we illustrate that only endothelial cells cultured on these mixed ligand surfaces exhibit the appropriate morphological changes - elongation and alignment in the direction of flow - when exposed to laminar shear flow, and neither of the individual ligands alone is sufficient. These results illustrate that both receptor types must be engaged for optimum cell-material interactions and are mandatory for appropriate mechanotransduction. The results presented in this manuscript will be critical for the development of next generation biomedical devices and tissue engineering scaffolds.

Syndecan-4 Enhances Therapeutic Angiogenesis after Hind Limb Ischemia in Mice with Type 2 Diabetes.

Delivering syndecan-4 with FGF-2 improves the effectiveness of FGF-2 therapy for ischemia in the diabetic disease state. The syndecan-4 proteoliposomes significantly enhance in vitro tubule formation as well as blood perfusion and vessel density in the ischemic hind limbs of diseased ob/ob mice. Syndecan-4 therapy also induces a marked immunomodulation in the tissues, increasing the polarization of macrophages toward the M2 phenotype.

Roles of syndecan-4 and relative kinases in dorsal root ganglion neuron adhesion and mechanotransduction.

Mechanical stimuli elicit a biological response and initiate complex physiological processes, including neural feedback schemes associated with senses such as pain, vibration, touch, and hearing. The syndecans (SDCs), a group of adhesion receptors, can modulate adhesion and organize the extracellular matrix (ECM). In this study, we cultured dorsal root ganglia (DRG) on controlled polydimethylsiloxane (PDMS) substrates coated with poly-l-lysine (poly) or fibronectin (FN) to investigate cell adhesion and mechanotransduction mechanisms by mechanical stretching on PDMS using DRG neurons. Our results demonstrated that neuronal density, neurite length, and neurite branching were lower in the PDMS group and could be further reversed through activating SDC-4 by FN. The expression of the SDC-4 pathway decreased but with increased pPKCα in the PDMS-poly group. After mechanical stretching, pPKCα-FAKpTyr397-pERK1/2 expression was increased in both poly- and FN-coated PDMS. These results indicate that SDC4-pPKCα-FAKpTyr397-pERK1/2 may play a crucial role in DRG adhesion and mechanotransduction.

Differential expression of fibroblast growth factor receptor-1, -2, and -3 and syndecan-1, -2, and -4 in neonatal rat mandibular condyle and calvaria during osteogenic differentiation in vitro.

Fibroblast growth factors (FGFs) play important roles in the control of skeletal cell growth and differentiation. To identify the mechanisms of regulation of FGF actions during chondrogenesis and osteogenesis, we investigated, by immunohistochemistry, the spatiotemporal expression of the high-affinity FGF receptors (FGFR-1, -2, and -3) and coreceptors (syndecans-1, -2, and -4) in newborn rat condyle and calvaria during chondrogenesis and osteogenesis in vitro. During chondrogenesis at 4 days of culture, condyle chondrocytes showed weak FGFR-1, FGFR-2, and syndecan-1 immunoreactivity; stronger syndecan-2 expression; and marked FGFR-3 and syndecan-4 immunolabeling. At a later stage (i.e., 9 days of culture), FGFR-1, -2, and -3 were coexpressed with syndecan-4 in chondrocytes. Condyle progenitor cells located in the condyle perichondrium initially expressed strong syndecan-2 and -4 and weak syndecan-1 labeling, whereas no FGFR was detectable. When these cells differentiated into osteoblasts, they expressed syndecan-2 and -4 coincidently with FGFR-1, -2, and -3 at 9 days of culture. In newborn rat calvaria, syndecan-1, -2, and -4 were coexpressed mainly with FGFR-1 and -2 in osteoblasts. In the two models, treatment with FGF-2 (100 ng/mL) at 4-9 days of culture increased cell growth and decreased glycosaminoglycan or collagen synthesis, respectively, suggesting interactions of FGF-2 with distinct FGFRs and syndecans during chondrogenesis and osteogenesis. The coincident or distinct spatiotemporal expression pattern of FGFRs and syndecans in chondrocytes, progenitor cells, and osteoblasts represents a dynamic mechanism by which FGF effects on skeletal cells may be controlled in a coordinate manner during cartilage and bone formation in vitro.

Cell-surface proteoglycan expression by lymphocytes from peripheral blood and gingiva in health and periodontal disease.

Cell-surface proteoglycans are involved in lymphocyte migration and activation. This study investigated the expression of syndecan-1, syndecan-4, and glypican in peripheral blood lymphocytes and by lymphocytes in variously inflamed periodontal tissues. Gingival specimens from healthy, gingivitis, or chronic periodontitis sites were stained by means of antibodies against B- and T-lymphocytes and also syndecan-1, syndecan-4, and glypican. Syndecan-1 expression by peripheral blood mononuclear cells (PBMC) from healthy, gingivitis, and chronic periodontitis subjects was assessed by flow cytometry. Syndecan-1 was expressed by B-cells/plasma cells but not T-cells in both gingivitis and chronic periodontitis lesions. Both B-cells/plasma cells and T-cells in gingivitis and chronic periodontitis expressed syndecan-4. Glypican was expressed only by macrophages. Stimulation of PBMC with mitogens and growth factors modulated syndecan-1 expression in both the T- and B-cells. Thus, cell-surface proteoglycan expression by lymphocytes in periodontal inflammation is cell-type-specific and may be modulated by inflammation.

Expression and roles of syndecan-4 in dental epithelial cell differentiation.

Syndecan-4 (SDC4), a transmembrane heparan sulfate proteoglycan, acts as a signal transducer. It affects the growth and differentiation of a number of tissues and organs. However, the specific mechanisms through which SDC4 regulates the differentiation of dental epithelial cells (amelogenesis) and tooth development remains largely unknown. In the present study, to identify the SDC4-regulated processes in dental epithelial cells, the SDC4 expression pattern was examined in mouse molar and postnatal incisor tooth germs during the late bell stage of development. Small interfering RNA (siRNA) was designed for this study and used to downregulate SDC4 expression in the rat dental epithelial cell line, HAT-7. The results revealed that SDC4 was mainly present in the oral epithelium, the dental epithelial cells of enamel organs in the molars and the cervical loops in the incisors. When the inner enamel epithelial cells gave rise to ameloblasts, however, the loss of SDC4 expression was evident. SDC4 was also expressed in stratum intermedium (SI) cells in the incisors and in dental mesenchymal cells adjacent to the cervical loops in molars (E18) and postnatal incisors. Fibroblast growth factor 10 (FGF10) promoted proliferation and slightly decreased cell differentiation. The knockdown of SDC4 using specific siRNA led to a decrease in cell proliferation and a highly significant increase in amelogenin, ameloblastin, kallikrein 4 and matrix metalloproteinase 20 expression, molecules that are known to participate in the formation of enamel. These effects were attenuated by FGF10, which upregulated SDC4 expression. Taken together, these results suggest that SDC4 participates in amelogenesis, and FGF10 may modulate dental epithelial cell behaviors through the regulation of SDC4 expression.

The role of caveolin-1 and syndecan-4 in the internalization of PEGylated PAMAM dendrimer polyplexes into myoblast and hepatic cells.

To improve gene delivery efficiency of PEGylated poly(amidoamine) dendrimers in livers and muscles, the roles of syndecan-4 receptor and caveolin-1 protein in the endocytosis of PEGylated generation 5 (G5-PEG) or 7 (G7-PEG) dendrimers and plasmid DNA polyplexes were explored in C2C12 and HepG2 cells. Expression levels of syndecan-4 for both cell lines were downregulated by transfection of the cells with syndecan-4 specific siRNA. Caveolin-1 was upregulated by infecting the cells with adenovirus vector expressed caveolin-1 (Ad-CAV-1). The impact of syndecan-4 and caveolin-1 on endocytosis of G5-PEG/DNA or G7-PEG/DNA polyplexes was then measured by flow cytometry. Our results demonstrate that downregulation of syndecan-4 and upregulation of caveolin-1 significantly improved internalization of PEG-PAMAM dendrimer polyplexes in HepG2 cells; however, in C2C12 cells, downregulation of syndecan-4 decreased the internalization of the polyplexes while upregulation of caveolin-1 had no effect on internalization. Gene expression results for G5-PEG/pGFP on the two cell lines exhibited the same trends for syndecan-4 and caveolin-1 as was observed for endocytosis of the polyplexes. This study gives a clue how to take strategies by up- or down-regulation of the expressions of syndecan-4 and caveolin-1 to improve in vivo gene delivery efficiency of the PEG-PAMAM dendrimers in clinical transgenic therapy.

[The effect of basic fibroblast growth factor on the gene expression of syndecan-4 by human periodontal ligament cell in culture].

OBJECTIVE: To study the effect of basic fibroblast growth factor (bFGF) on the gene expression of syndecan-4 by human periodontal ligament cell (PDLC) in culture, and discuss the effect of bFGF on human PDLC proliferation and migration. METHODS: 68 adolescent (12-18 years old) health premolar were collected, which were extracted for orthodontic reason. Human PDLC were cultured and stimulated by exogenous bFGF. After cultured 24, 48, 72h, gene expression of syndecan-4 was detected by SYBR green quantitative real time polymerase chain reaction. RESULTS: The mRNA expression of syndecan-4 in 24 h group increased markedly than that in control group (P < 0.01), expecially in 1.0 ng x mL(-1) group. 1.0 ng x mL(-1) group in 48 h higher than that control group (P < 0.05). 1.0 ng x mL(-1) group in 72h compared with control group was lower (P < 0.05). CONCLUSION: The mRNA expression of syndecan-4 was increased by bFGF at the beginning, but the expression was decreased with the time. The expression of such changes may be one of the important factors which participate in the migration process of PDLC.

Expression of cell-surface heparan sulfate proteoglycans in human cyclosporin-induced gingival overgrowth.

BACKGROUND AND OBJECTIVE: Cyclosporin A-induced gingival overgrowth comprises a variety of signaling pathways (including growth factors and proteoglycans) that are still not completely understood. In the present study, gingival overgrowth was investigated in transplant patients receiving cyclosporin A (cyclosporin A group) and compared with gingival tissues never exposed to the drug (control group) by analyzing the gene expression of the cell-surface heparan sulfate proteoglycans syndecan-2, syndecan-4 and betaglycan. MATERIAL AND METHODS: mRNA analysis was carried out by reverse transcription-polymerase chain reaction amplification of pooled samples from nine patients of the cyclosporin A group and six control subjects. The groups were compared by the Student's t-test. RESULTS: The expression of heparan sulfate proteoglycans was increased in the cyclosporin A group (165% for syndecan-2, 308% for syndecan-4, and 42% for betaglycan) compared with the control group. CONCLUSION: Our findings agree with the current concept of cyclosporin A-induced gingival overgrowth and provide new evidence that its noncollagenous extracellular matrix is overexpressed.

Cell surface proteoglycan expression by human periodontal cells.

Cell surface proteoglycans are known to be involved in many functions including interactions with components of the extracellular microenvironment and serve to influence cell shape, adhesion, proliferation, and differentiation. They also can act as co-receptors, to help bind and modify the action of various growth factors and cytokines. Despite their strategic location and relevance to cell function, few studies have considered the nature of the cell surface proteoglycans associated with cells of the periodontium. Due to the structural complexity and multiplicity of cell types in the periodontium, we have selected three different cell lines (gingival connective tissue fibroblast, periodontal ligament fibroblast, and osteoblast) which each represent the unique functions within the periodontium to study the expression of cell surface proteoglycans. We hypothesized that a number of cell surface proteoglycans will be expressed by human periodontal cells and these may be related to the source and function of the cell. Western blotting and RT-PCR methods were used to study the expression of five cell surface proteoglycans (syndecan-1, -2, -4, glypican and betaglycan) in three cell lines of human periodontal cells in vitro. Our results demonstrated the expression of protein cores for syndecan-1 (43 kDa), syndecan-2 (48 kDa), syndecan-4 (35 kDa), glypican (64 kDa), and betaglycan (100-110 kDa). RT-PCR results confirmed that all of these cells produced mRNA for the cell surface proteoglycans under study, of which syndecan-2 showed a significant difference in expression between the periodontal ligament fibroblasts, gingival fibroblasts and osteoblasts. We conclude that the presence of specific cell surface proteoglycans on periodontal cells implies a likely role for these molecules in cell-cell, cell-matrix interactions involved in periodontal disease and/or regeneration of the periodontium, of which they may have distinctive functions related to the source and function of these cells.

Syndecan-4 associates with alpha-actinin.

Cell adhesion to the extracellular matrix influences many cellular functions. The integrin family of matrix receptors plays major roles in the formation of adhesions, but other proteins modulate integrin signaling. Syndecan-4, a transmembrane proteoglycan, cooperatively signals with integrins during the formation of focal adhesions. To date, a direct link between syndecan-4 and the cytoskeleton has remained elusive. We now demonstrate by Triton X-100 extraction immunoprecipitation and in vitro binding assays that the focal adhesion component alpha-actinin interacts with syndecan-4 in a beta-integrin-independent manner.