Effects of a sulfated exopolysaccharide produced by Altermonas infernus on bone biology

Chemical modification of bacterial exopolysaccharides: Antioxidant properties and health potentials

In recent years, there has been a burgeoning interest in the utilization of microbial exopolysaccharides (EPS) because of the added advantage of their renewable, biocompatible, and biodegradable nature in addition to intended applications. The endowed properties of bacterial EPS make them valuable candidates for a wide array of industrial applications. Modification of native EPS is known to enhance various physico-chemical and functional properties. Various modifications such as physical, chemical, biological, and enzymatic modifications were practiced improving the bioactivity of EPS. This paper comprehensively aims to review the most recent chemical modification techniques employed to modify the physico-chemical and functional changes of bacterial EPS in comparison with the unmodified forms. Chemical modification entails strategic alterations to the structure and properties of EPS through various synthetic and semi-synthetic methodologies. Emphasis is given to the antioxidant potential and functional role of these EPS derivatives in human health. Antioxidant properties reveal a significant augmentation in activity compared to their native counterparts. Such enhancement holds a strong promise for potential benefits and therapeutic applications. Chemical derivatives of EPS with overwhelming functional benefits could surely encourage EPS application, particularly as potential hydrocolloids in industrial and biomedical contexts.

Effect of Bifidobacterium on osteoclasts: TNF-α/NF-κB inflammatory signal pathway-mediated mechanism

Osteoporosis is a systemic multifactorial bone disease characterized by low bone quality and density and bone microstructure damage, increasing bone fragility and fracture vulnerability. Increased osteoclast differentiation and activity are important factors contributing to bone loss, which is a common pathological manifestation of bone diseases such as osteoporosis. TNF-a/NF-κB is an inflammatory signaling pathway with a key regulatory role in regulating osteoclast formation, and the classical pathway RANKL/RANK/OPG assists osteoclast formation. Activation of this inflammatory pathway promotes the formation of osteoclasts and accelerates the process of osteoporosis. Recent studies and emerging evidence have consistently demonstrated the potential of probiotics to modulate bone health. Secretions of Bifidobacterium, a genus of probiotic bacteria in the phylum Actinobacteria, such as short-chain fatty acids, equol, and exopolysaccharides, have indicated beneficial effects on bone health. This review discusses the molecular mechanisms of the TNF-a/NF-κB inflammatory pathway in regulating osteoclast formation and describes the secretions produced by Bifidobacterium and their potential effects on bone health through this pathway, opening up new directions for future research.

Prebiotics improve osteoporosis indicators in a preclinical model: systematic review with meta-analysis

CONTEXT

Studies using experimental models have demonstrated that prebiotics are involved in antiosteoporotic mechanisms.

OBJECTIVE

This study was conducted to determine the impact of supplementation with prebiotics in the basal diet of ovariectomized rats with induced osteoporosis as a preclinical model.

METHODS

A comprehensive systematic search was carried out in the electronic databases PubMed, Science Direct, Web of Science, Scielo, and Google through March 2022 for studies that investigated the impact of prebiotics on bone mineral density (BMD), bone mineral content (BMC), and bone biomechanics.

RESULTS

The search returned 844 complete articles, abstracts, or book chapters. After detailed screening, 8 studies met the inclusion criteria. Rats (n = 206), were randomly divided between control and treatment groups. Weighted mean differences (WMDs) with the 95%CIs were used to estimate the combined effect size. Compared with the control group, dietary intake of prebiotics significantly increased bone density in the BMD subgroups, with WMDs as follows: 0.03 g/cm3, 95%CI, 0.01-0.05, P < 0.00001, n = 46; and 0.00 g/cm2, 95%CI, 0.00-0.02, P < 0.00001, n = 81; total BMD: WMD, 0.01, 95%CI, 0.01-0.02, P < 0.00001, n = 127; bone content in BMC: WMD, 0.02 g, 95%CI, 0.00-0.04, P = 0.05, n = 107; and the 3-point-bend test: WMD, 15.20 N, 95%CI, 5.92-24.47, P = 0.00001, n = 120.

CONCLUSION

Prebiotics improve indicators of osteoporosis, BMD, BMC, and bone biomechanics in ovariectomized rats. More studies are needed to increase the level of evidence.

SYSTEMIC REVIEW REGISTRATION

Systematic Review Protocol for Animal Intervention Studies.

Sulfated carboxymethyl cellulose and carboxymethyl κ-carrageenan immobilization on 3D-printed poly-ε-caprolactone scaffolds differentially promote pre-osteoblast proliferation and osteogenic activity

The lack of bioactivity in three-dimensional (3D)-printing of poly-є-caprolactone (PCL) scaffolds limits cell-material interactions in bone tissue engineering. This constraint can be overcome by surface-functionalization using glycosaminoglycan-like anionic polysaccharides, e.g., carboxymethyl cellulose (CMC), a plant-based carboxymethylated, unsulfated polysaccharide, and κ-carrageenan, a seaweed-derived sulfated, non-carboxymethylated polysaccharide. The sulfation of CMC and carboxymethylation of κ-carrageenan critically improve their bioactivity. However, whether sulfated carboxymethyl cellulose (SCMC) and carboxymethyl κ-carrageenan (CM-κ-Car) affect the osteogenic differentiation potential of pre-osteoblasts on 3D-scaffolds is still unknown. Here, we aimed to assess the effects of surface-functionalization by SCMC or CM-κ-Car on the physicochemical and mechanical properties of 3D-printed PCL scaffolds, as well as the osteogenic response of pre-osteoblasts. MC3T3-E1 pre-osteoblasts were seeded on 3D-printed PCL scaffolds that were functionalized by CM-κ-Car (PCL/CM-κ-Car) or SCMC (PCL/SCMC), cultured up to 28 days. The scaffolds’ physicochemical and mechanical properties and pre-osteoblast function were assessed experimentally and by finite element (FE) modeling. We found that the surface-functionalization by SCMC and CM-κ-Car did not change the scaffold geometry and structure but decreased the elastic modulus. Furthermore, the scaffold surface roughness and hardness increased and the scaffold became more hydrophilic. The FE modeling results implied resilience up to 2% compression strain, which was below the yield stress for all scaffolds. Surface-functionalization by SCMC decreased Runx2 and Dmp1 expression, while surface-functionalization by CM-κ-Car increased Cox2 expression at day 1. Surface-functionalization by SCMC most strongly enhanced pre-osteoblast proliferation and collagen production, while CM-κ-Car most significantly increased alkaline phosphatase activity and mineralization after 28 days. In conclusion, surface-functionalization by SCMC or CM-κ-Car of 3D-printed PCL-scaffolds enhanced pre-osteoblast proliferation and osteogenic activity, likely due to increased surface roughness and hydrophilicity. Surface-functionalization by SCMC most strongly enhanced cell proliferation, while CM-κ-Car most significantly promoted osteogenic activity, suggesting that surface-functionalization by CM-κ-Car may be more promising, especially in the short-term, for in vivo bone formation.

Complexation of europium(III) with exopolysaccharides from a marine bacterium envisaged as luminescent probe in a theranostic approach

Exopolysaccharide (EPS) derivatives, produced by Alteromonas infernus bacterium, showed anti-metastatic properties in osteosarcoma (bone tumor). These EPSs could be employed as new drug delivery systems for therapeutic uses. They may represent a new class of ligands to be combined in a theranostic approach with fluorescent metals, such as Eu(III), to serve as imaging probe. The goal of this work was to investigate the feasibility of such coupling by time-resolved laser-induced fluorescence spectroscopy (TRLFS). Since these EPSs are polyelectrolytes their conformation could affect the complexation properties. Thus, viscosimetric measurements were performed as a function of their concentration as well as the background electrolyte concentration. Polysaccharides conformation exhibited a lower hydrodynamic volume for the highest ionic strengths. The resulting random-coiled conformation could affect the complexation with metal for high concentration but no change was evidenced when increasing europium concentration. Two sites of complexation of Eu(III) were evidenced by TRLFS in heparin, whereas only one site was evidenced in two modified EPSs produced from Alteromonas infernus.

Bioactive Carbohydrate Polymers-Between Myth and Reality

Polysaccharides are complex macromolecules long regarded as energetic storage resources or as components of plant and fungal cell walls. They have also been described as plant mucilages or microbial exopolysaccharides. The development of glycosciences has led to a partial and difficult deciphering of their other biological functions in living organisms. The objectives of glycobiochemistry and glycobiology are currently to correlate some structural features of polysaccharides with some biological responses in the producing organisms or in another one. In this context, the literature focusing on bioactive polysaccharides has increased exponentially during the last two decades, being sometimes very optimistic for some new applications of bioactive polysaccharides, notably in the medical field. Therefore, this review aims to examine bioactive polysaccharide, taking a critical look of the different biological activities reported by authors and the reality of the market. It focuses also on the chemical, biochemical, enzymatic, and physical modifications of these biopolymers to optimize their potential as bioactive agents.

Regulation of Bone Cell Differentiation and Activation by Microbe-Associated Molecular Patterns

Gut microbiota has emerged as an important regulator of bone homeostasis. In particular, the modulation of innate immunity and bone homeostasis is mediated through the interaction between microbe-associated molecular patterns (MAMPs) and the host pattern recognition receptors including Toll-like receptors and nucleotide-binding oligomerization domains. Pathogenic bacteria such as Porphyromonas gingivalis and Staphylococcus aureus tend to induce bone destruction and cause various inflammatory bone diseases including periodontal diseases, osteomyelitis, and septic arthritis. On the other hand, probiotic bacteria such as Lactobacillus and Bifidobacterium species can prevent bone loss. In addition, bacterial metabolites and various secretory molecules such as short chain fatty acids and cyclic nucleotides can also affect bone homeostasis. This review focuses on the regulation of osteoclast and osteoblast by MAMPs including cell wall components and secretory microbial molecules under in vitro and in vivo conditions. MAMPs could be used as potential molecular targets for treating bone-related diseases such as osteoporosis and periodontal diseases.

Antiproliferative Properties of Scandium Exopolysaccharide Complexes on Several Cancer Cell Lines

Antimetastatic properties on both murine and human osteosarcoma cell lines (POS-1 and KHOS) have been evidenced using exopolysaccharide (EPS) derivatives, produced by Alteromonas infernus bacterium. These derivatives had no significant effect on the cell cycle neither a pro-apoptotic effect on osteosarcoma cells. Based on this observation, these EPSs could be employed as new drug delivery systems for therapeutic uses. A theranostic approach, i.e., combination of a predictive biomarker with a therapeutic agent, has been developed notably by combining with true pair of theranostic radionuclides, such as scandium ⁴⁷Sc/⁴⁴Sc. However, it is crucial to ensure that, once complexation is done, the biological properties of the vector remain intact, allowing the molecular tropism of the ligand to recognize its molecular target. It is important to assess if the biological properties of EPS evidenced on osteosarcoma cell lines remain when scandium is complexed to the polymers and can be extended to other cancer cell types. Scandium-EPS complexes were thus tested in vitro on human cell lines: MNNG/HOS osteosarcoma, A375 melanoma, A549 lung adenocarcinoma, U251 glioma, MDA231 breast cancer, and Caco2 colon cancer cells. An xCELLigence Real Cell Time Analysis (RTCA) technology assay was used to monitor for 160 h, the proliferation kinetics of the different cell lines. The tested complexes exhibited an anti-proliferative effect, this effect was more effective compared to EPS alone. This increase of the antiproliferative properties was explained by a change in conformation of EPS complexes due to their polyelectrolyte nature that was induced by complexation. Alterations of both growth factor-receptor signaling, and transmembrane protein interactions could be the principal cause of the antiproliferative effect. These results are very promising and reveal that EPS can be coupled to scandium for improving its biological effects and also suggesting that no major structural modification occurs on the ligand.

Marine Exopolysaccharide Complexed With Scandium Aimed as Theranostic Agents

(1) Background: Exopolysaccharide (EPS) derivatives, produced by Alteromonas infernus bacterium, showed anti-metastatic properties. They may represent a new class of ligands to be combined with theranostic radionuclides, such as ⁴⁷Sc/⁴⁴Sc. The goal of this work was to investigate the feasibility of such coupling. (2) Methods: EPSs, as well as heparin used as a drug reference, were characterized in terms of molar mass and dispersity using Asymmetrical Flow Field-Flow Fractionation coupled to Multi-Angle Light Scattering (AF4-MALS). The intrinsic viscosity of EPSs at different ionic strengths were measured in order to establish the conformation. To determine the stability constants of Sc with EPS and heparin, a Free-ion selective radiotracer extraction (FISRE) method has been used. (3) Results: AF4-MALS showed that radical depolymerization produces monodisperse EPSs, suitable for therapeutic use. EPS conformation exhibited a lower hydrodynamic volume for the highest ionic strengths. The resulting random-coiled conformation could affect the complexation with metal for high concentration. The LogK of Sc-EPS complexes have been determined and showing that they are comparable to the Sc-Hep. (4) Conclusions: EPSs are very promising to be coupled with the theranostic pair of scandium for Nuclear Medicine.

Marine Polysaccharide-Collagen Coatings on Ti6Al4V Alloy Formed by Self-Assembly

Polysaccharides of marine origin are gaining interest as biomaterial components. Bacteria derived from deep-sea hydrothermal vents can produce sulfated exopolysaccharides (EPS), which can influence cell behavior. The use of such polysaccharides as components of organic, collagen fibril-based coatings on biomaterial surfaces remains unexplored. In this study, collagen fibril coatings enriched with HE800 and GY785 EPS derivatives were deposited on titanium alloy (Ti6Al4V) scaffolds produced by rapid prototyping and subjected to physicochemical and cell biological characterization. Coatings were formed by a self-assembly process whereby polysaccharides were added to acidic collagen molecule solution, followed by neutralization to induced self-assembly of collagen fibrils. Fibril formation resulted in collagen hydrogel formation. Hydrogels formed directly on Ti6Al4V surfaces, and fibrils adsorbed onto the surface. Scanning electron microscopy (SEM) analysis of collagen fibril coatings revealed association of polysaccharides with fibrils. Cell biological characterization revealed good cell adhesion and growth on bare Ti6Al4V surfaces, as well as coatings of collagen fibrils only and collagen fibrils enhanced with HE800 and GY785 EPS derivatives. Hence, the use of both EPS derivatives as coating components is feasible. Further work should focus on cell differentiation.

Bioprospecting for Exopolysaccharides from Deep-Sea Hydrothermal Vent Bacteria: Relationship between Bacterial Diversity and Chemical Diversity

Many bacteria biosynthesize structurally diverse exopolysaccharides (EPS) and excrete them into their surrounding environment. The EPS functional features have found many applications in industries such as cosmetics and pharmaceutics. In particular, some EPS produced by marine bacteria are composed of uronic acids, neutral sugars, and N-acetylhexosamines, and may also bear some functional sulfate groups. This suggests that they can share common structural features with glycosaminoglycans (GAG) like the two EPS (HE800 and GY785) originating from the deep sea. In an attempt to discover new EPS that may be promising candidates as GAG-mimetics, fifty-one marine bacterial strains originating from deep-sea hydrothermal vents were screened. The analysis of the EPS chemical structure in relation to bacterial species showed that Vibrio, Alteromonas, and Pseudoalteromonas strains were the main producers. Moreover, they produced EPS with distinct structural features, which might be useful for targeting marine bacteria that could possibly produce structurally GAG-mimetic EPS.

Anti-Metastatic Properties of a Marine Bacterial Exopolysaccharide-Based Derivative Designed to Mimic Glycosaminoglycans

Osteosarcoma is the most frequent malignant primary bone tumor characterized by a high potency to form lung metastases. In this study, the effect of three oversulfated low molecular weight marine bacterial exopolysaccharides (OS-EPS) with different molecular weights (4, 8 and 15 kDa) were first evaluated in vitro on human and murine osteosarcoma cell lines. Different biological activities were studied: cell proliferation, cell adhesion and migration, matrix metalloproteinase expression. This in vitro study showed that only the OS-EPS 15 kDa derivative could inhibit the invasiveness of osteosarcoma cells with an inhibition rate close to 90%. Moreover, this derivative was potent to inhibit both migration and invasiveness of osteosarcoma cell lines; had no significant effect on their cell cycle; and increased slightly the expression of MMP-9, and more highly the expression of its physiological specific tissue inhibitor TIMP-1. Then, the in vivo experiments showed that the OS-EPS 15 kDa derivative had no effect on the primary osteosarcoma tumor induced by osteosarcoma cell lines but was very efficient to inhibit the establishment of lung metastases in vivo. These results can help to better understand the mechanisms of GAGs and GAG-like derivatives in the biology of the tumor cells and their interactions with the bone environment to develop new therapeutic strategies.

CCN2 enhances RANKL-induced osteoclast differentiation via direct binding to RANK and OPG

CCN family protein 2/connective tissue growth factor (CCN2/CTGF) is a multi-potent factor for mesenchymal cells such as chondrocytes, osteoblasts, osteoclasts, and endothelial cells. CCN2 is also known as a modulator of other cytokines and receptors via direct molecular interactions with them. We screened additional factors binding to CCN2 and found receptor activator of NF-kappa B (RANK) as one of them. RANK is also known as TNF-related activation-induced cytokine (TRANCE) receptor, and its signaling plays a critical role in osteoclastogenesis. Notable affinity between CCN2 and RANK was confirmed by using surface plasmon resonance (SPR) analysis. In fact, CCN2 enhanced the RANK-mediated signaling, such as occurs in NF-kappa B, p38 and JNK pathways, in pre-osteoclastic RAW264.7 cells; whereas CCN2 had no influence on RANK-RANK ligand (RANKL) binding. Moreover, CCN2 also significantly bound to osteoprotegerin (OPG), which is a decoy receptor of RANKL. Of note, OPG markedly inhibited the binding between CCN2 and RANK; and CCN2 canceled the inhibitory effect of OPG on osteoclast differentiation. These findings suggest CCN2 as a candidate of the fourth factor in the RANK/RANKL/OPG system for osteoclastogenesis, which regulates OPG and RANK via direct interaction.

Exopolysaccharides produced by marine bacteria and their applications as glycosaminoglycan-like molecules

Although polysaccharides are ubiquitous and the most abundant renewable bio-components, their studies, covered by the glycochemistry and glycobiology fields, remain a challenge due to their high molecular diversity and complexity. Polysaccharides are industrially used in food products; human therapeutics fall into a more recent research field and pharmaceutical industry is looking for more and more molecules with enhanced activities. Glycosaminoglycans (GAGs) found in animal tissues play a critical role in cellular physiological and pathological processes as they bind many cellular components. Therefore, they present a great potential for the design and preparation of therapeutic drugs. On the other hand, microorganisms producing exopolysaccharides (EPS) are renewable resources meeting well the actual industrial demand. In particular, the diversity of marine microorganisms is still largely unexplored offering great opportunities to discover high value products such as new molecules and biocatalysts. EPS-producing bacteria from the marine environment will be reviewed with a focus on marine-derived EPS from bacteria isolated from deep-sea hydrothermal vents. Information on chemical and structural features, putative pathways of biosynthesis, novel strategies for chemical and enzymatic modifications and potentialities in the biomedical field will be provided. An integrated approach should be used to increase the basic knowledge on these compounds and their applications; new clean environmentally friendly processes for the production of carbohydrate bioactive compounds should also be proposed for a sustainable industry.

Osteoprotegerin: multiple partners for multiple functions

Osteoprotegerin (OPG) is an essential secreted protein in bone turnover due to its role as a decoy receptor for the Receptor Activator of Nuclear Factor-kB ligand (RANKL) in the osteoclasts, thus inhibiting their differentiation. However, there are additional ligands of OPG that confer various biological functions. OPG can promote cell survival, cell proliferation and facilitates migration by binding TNF-related apoptosis inducing ligand (TRAIL), glycosaminoglycans or proteoglycans. A large number of in vitro, pre-clinical and clinical studies provide evidences of OPG involvement in vascular, bone, immune and tumor biology. This review describes an overview of the different OPG ligands regulating its biological functions.

Proteoglycans and osteolysis

Osteolysis is a complex mechanism resulting from an exacerbated activity of osteoclasts associated or not with a dysregulation of osteoblast metabolism leading to bone loss. This bone defect is not compensated by bone apposition or by apposition of bone matrix with poor mechanical quality. Osteolytic process is regulated by mechanical constraints, by polypeptides including cytokines and hormones, and by extracellular matrix components such as proteoglycans (PGs) and glycosaminoglycans (GAGs). Several studies revealed that GAGs may influence osteoclastogenesis, but data are very controversial: some studies showed a repressive effect of GAGs on osteoclastic differentiation, whereas others described a stimulatory effect. The controversy also affects osteoblasts which appear sometimes inhibited by polysaccharides and sometimes stimulated by these compounds. Furthermore, long-term treatment with heparin leads to the development of osteoporosis fueling the controversy. After a brief description of the principal osteoclastogenesis assays, the present chapter summarizes the main data published on the effect of PGs/GAGs on bone cells and their functional incidence on osteolysis.

Marine polysaccharides: a source of bioactive molecules for cell therapy and tissue engineering

The therapeutic potential of natural bioactive compounds such as polysaccharides, especially glycosaminoglycans, is now well documented, and this activity combined with natural biodiversity will allow the development of a new generation of therapeutics. Advances in our understanding of the biosynthesis, structure and function of complex glycans from mammalian origin have shown the crucial role of this class of molecules to modulate disease processes and the importance of a deeper knowledge of structure-activity relationships. Marine environment offers a tremendous biodiversity and original polysaccharides have been discovered presenting a great chemical diversity that is largely species specific. The study of the biological properties of the polysaccharides from marine eukaryotes and marine prokaryotes revealed that the polysaccharides from the marine environment could provide a valid alternative to traditional polysaccharides such as glycosaminoglycans. Marine polysaccharides present a real potential for natural product drug discovery and for the delivery of new marine derived products for therapeutic applications.