Syndecans and Enzymes for Heparan Sulfate Biosynthesis and Modification Differentially Correlate With Presence of Inflammatory Infiltrate in Periodontitis

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

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

Control of tissue homeostasis by the extracellular matrix: Synthetic heparan sulfate as a promising therapeutic for periodontal health and bone regeneration

Proteoglycans are core proteins associated with carbohydrate/sugar moieties that are highly variable in disaccharide composition, which dictates their function. These carbohydrates are named glycosaminoglycans, and they can be attached to proteoglycans or found free in tissues or on cell surfaces. Glycosaminoglycans such as hyaluronan, chondroitin sulfate, dermatan sulfate, keratan sulfate, and heparin/heparan sulfate have multiple functions including involvement in inflammation, immunity and connective tissue structure, and integrity. Heparan sulfate is a highly sulfated polysaccharide that is abundant in the periodontium including alveolar bone. Recent evidence supports the contention that heparan sulfate is an important player in modulating interactions between damage associated molecular patterns and inflammatory receptors expressed by various cell types. The structure of heparan sulfate is reported to dictate its function, thus, the utilization of a homogenous and structurally defined heparan sulfate polysaccharide for modulation of cell function offers therapeutic potential. Recently, a chemoenzymatic approach was developed to allow production of many structurally defined heparan sulfate carbohydrates. These oligosaccharides have been studied in various pathological inflammatory conditions to better understand their function and their potential application in promoting tissue homeostasis. We have observed that specific size and sulfation patterns can modulate inflammation and promote tissue maintenance including an anabolic effect in alveolar bone. Thus, new evidence provides a strong impetus to explore heparan sulfate as a potential novel therapeutic agent to treat periodontitis, support alveolar bone maintenance, and promote bone formation.

Heparan Sulfate Glycosaminoglycan Is Predicted to Stabilize Inflammatory Infiltrate Formation and RANKL/OPG Ratio in Severe Periodontitis in Humans

Since chronically inflamed periodontal tissue exhibits extracellular matrix (ECM) degradation, the possible alternative to standard periodontitis treatment is to restore ECM by supplementing its components, including heparan sulfate glycosaminoglycan (HS GAG). Supplementation of the degraded ECM with synthetic derivatives of HS GAGs has been shown to be effective for periodontal tissue regeneration in experimental animal models of periodontitis. However, the potential of HS GAG supplementation for the treatment of periodontal disease in humans is still unknown. Here, we used a statistical model to investigate the role of HS GAG on inflammatory infiltrate formation and alveolar bone resorption in humans with severe periodontitis. The model was based on data from immunofluorescence staining (IF) of human gingiva samples, and reconstruction of a subset of HS GAG -related proteins from STRING reactome database. According to predictions, increased expression of native HS GAG might stabilize the accumulation of gingival inflammatory infiltrate (represented by the general inflammatory cell marker CD45) and alveolar bone resorption (represented by Receptor Activator of Nuclear ΚΒ ligand (RANKL) and osteoprotegerin (OPG) ratio) but could not restore them to healthy tissue levels. Therefore, supplementation of native HS GAG may be of limited benefits for the treatment of sever periodontitis in humans.

Modification of gingival proteoglycans by reactive oxygen species: potential mechanism of proteoglycan degradation during periodontal diseases

Reactive oxygen species (ROS) overproduction and oxidative stress are increasingly being implicated in the extracellular matrix (ECM) degradation associated with chronic inflammatory conditions, such as periodontal diseases. The present study investigated the effects of ROS exposure on the proteoglycans of gingival tissues, utilizing an in vitro model system comprised of supra-physiological oxidant concentrations, to ascertain whether gingival proteoglycan modification and degradation by ROS contributed to the underlying mechanisms of ECM destruction during active gingivitis. Proteoglycans were purified from ovine gingival tissues and exposed to increasing H₂O₂ concentrations or a hydroxyl radical (·OH) flux for 1 h or 24 h, and ROS effects on proteoglycan core proteins and sulfated glycosaminoglycan (GAG) chains were assessed. ROS were capable of degrading gingival proteoglycans, with ·OH species inducing greater degradative effects than H₂O₂ alone. Degradative effects were particularly manifested as amino acid modification, core protein cleavage, and GAG chain depolymerization. Proteoglycan core proteins were more susceptible to degradation than GAG chains with H₂O₂ alone, although core proteins and GAG chains were both extensively degraded by ·OH species. Proteoglycan exposure to ·OH species for 24 h induced significant core protein amino acid modification, with decreases in glutamate, proline, isoleucine, and leucine; and concomitant increases in serine, glycine, and alanine residues. As clinical reports have previously highlighted proteoglycan core protein degradation during chronic gingivitis, whereas their sulfated GAG chains remain relatively intact, these findings potentially provide further evidence to implicate ROS in the pathogenesis of active gingivitis, complementing the enzymic mechanisms of periodontal tissue destruction already established.

Novel approach for quantification of multiple immunofluorescent signals using histograms and 2D plot profiling of whole-section panoramic images

We describe a novel approach for quantification and colocalization of immunofluorescence (IF) signals of multiple markers on high-resolution panoramic images of serial histological sections utilizing standard staining techniques and readily available software for image processing and analysis. Human gingiva samples stained with primary antibodies against the common leukocyte antigen CD45 and factors related to heparan sulfate glycosaminoglycans (HS GAG) were used. Expression domains and spatial gradients of IF signals were quantified by histograms and 2D plot profiles, respectively. The importance of histomorphometric profiling of tissue samples and IF signal thresholding is elaborated. This approach to quantification of IF staining utilizes pixel (px) counts and comparison of px grey value (GV) or luminance. No cell counting is applied either to determine the cellular content of a given histological section nor the number of cells positive to the primary antibody of interest. There is no selection of multiple Regions-Of-Interest (ROIs) since the entire histological section is quantified. Although the standard IF staining protocol is applied, the data output enables colocalization of multiple markers (up to 30) from a given histological sample. This can serve as an alternative for colocalization of IF staining of multiple primary antibodies based on repeating cycles of staining of the same histological section since those techniques require non standard staining protocols and sophisticated equipment that can be out of reach for small laboratories in academic settings. Combined with the data from ontological bases, this approach to quantification of IF enables creation of in silico virtual disease models.

Proteoglycans in the periodontium: A review with emphasis on specific distributions, functions, and potential applications

Proteoglycans (PGs) are largely glycosylated proteins, consisting of a linkage sugar, core proteins, and glycosaminoglycans (GAGs). To date, more than 40 kinds of PGs have been identified, and they can be classified as intracellular, cell surface, pericellular, and extracellular PGs according to cellular locations. To illustrate, extracellular PGs are known for regulating the homeostasis of the extracellular matrix; cell-surface PGs play a role in mediating cell adhesion and binding various growth factors. In the field of periodontology, PGs are implicated in cellular proliferation, migration, adhesion, contractility, and anoikis, thereby exerting a profound influence on periodontal tissue development, wound repair, the immune response, biomechanics, and pathological process. Additionally, the expression patterns of some PGs are dynamic and cell-specific. Therefore, determining the roles and spatial-temporal expression patterns of PGs in the periodontium could shed light on treatments for wound healing, tissue regeneration, periodontitis, and gingival overgrowth. In this review, close attention is paid to the distributions, functions, and potential applications of periodontal PGs. Related genetically modified animal experiments and involved signal transduction cascades are summarized for improved understanding of periodontal PGs. To date, however, there is a large amount of speculation on this topic that requires rigorous experiments for validation.