Poly-γ-glutamic acid suppresses osteoclastogenesis in human osteoclast precursors and prevents joint damage in a collagen-induced murine arthritis model

Role of gut microbiota in rheumatoid arthritis: Potential cellular mechanisms regulated by prebiotic, probiotic, and pharmacological interventions

Rheumatoid arthritis (RA) is a chronic autoimmune disease that primarily affects joints and multiple organs and systems, which is long-lasting and challenging to cure and significantly impacting patients' quality of life. Alterations in the composition of intestinal flora in both preclinical and confirmed RA patients indicate that intestinal bacteria play a vital role in RA immune function. However, the mechanism by which the intestinal flora is regulated to improve the condition of RA is not fully understood. This paper reviews the methods of regulating gut microbiota and its metabolites through prebiotics, probiotics, and pharmacological interventions, and discusses their effects on RA. Additionally, it explores the potential predictive role of cellular therapy mechanisms of intestinal flora in treating RA. These findings suggest that restoring the ecological balance of intestinal flora and regulating intestinal barrier function may enhance immune system function, thereby improving rheumatoid arthritis. This offers new insights into its treatment.

Immunostimulant, hepatoprotective, and nephroprotective potential of Bacillus subtilis (NMCC-path-14) in comparison to dexamethasone in alleviating CFA-induced arthritis

To investigate and compare efficacy as well as safety of Bacillus subtilis and dexamethasone (Dexa) in complete Freund's adjuvant (CFA)-induced arthritis, we used glucocorticoid monotherapy (Dexa 5 mg/kg/day) and B. subtilis (1 × 108 CFU/animal/day p.o) as pre-treatment and concurrent treatment for a duration of 35 days. Specific emphasis was on chronic aspect of this study since long-term use of Dexa is known to produce undesirable side effects. Treatment with Dexa significantly attenuated the arthritic symptoms but produced severe side effects like weight loss, increased mortality, immunosuppression, and altered histology of liver, kidney, and spleen. Oxidative stress was also elevated by Dexa in these organs which contributed to the damage. Treatment with B. subtilis improved symptoms of arthritis without producing any deleterious side effects as seen with Dexa therapy. Immunohistochemistry (IHC) profile revealed decreased expression of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), interleukin (IL)-1β, tumor necrosis factor alpha (TNF-α), and increased nuclear factor erythroid 2-related factor 2 (Nrf-2) expression by B. subtilis and Dexa treatment in ankle joint of arthritic mice. Radiological scores were also improved by both treatments. This study concludes that B. subtilis could be an effective alternative for treating arthritis than Dexa since it does not produce life-threatening side effects on prolong treatment.

Effect of phosphodiester composition in polyphosphoesters on the inhibition of osteoclastic differentiation of murine bone marrow mononuclear cells

Osteoporosis is a common bone disorder characterized by reduced bone density and increased risk of fractures. The modulation of bone cell functions, particularly the inhibition of osteoclastic differentiation, plays a crucial role in osteoporosis treatment. Polyphosphoesters (PPEs) have shown the potential in reducing the function of osteoclast cells, but the effect of their chemical structure on osteoclastic differentiation remains largely unexplored. In this study, we evaluated the effect of PPE's chemical structure on the inhibition of osteoclastic differentiation of murine bone marrow mononuclear cells (BMNCs). PPEs containing phosphotriester and phosphodiester units at varying compositions were synthesized. Cytotoxicity testing confirmed the biocompatibility of the copolymers at concentrations below 0.5 mg/mL. Isolated from long bones, BMNCs were cultured in a differentiation medium supplemented with different PPE concentrations. Osteoclast formation was assessed through tartrate-resistant acid phosphatase and phalloidin staining. A significant decrease in the size of osteoclast cells formed upon BMNC contact with PPEs was observed, with a more pronounced effect observed at higher PPE concentrations. In addition, an increased composition of phosphodiester units in the PPEs yielded a decreased density of differentiated osteoclasts. Furthermore, real-time PCR analysis of major osteoclastic markers provided gene expression data that correlated with microscopic observations, confirming the effect of phosphodiester units in suppressing osteoclast differentiation of BMNCs from the early stages. These findings highlight the potential of PPEs as polymers are capable of modulating bone cell functions through their chemical structures.

Impact of humid climate on rheumatoid arthritis faecal microbiome and metabolites

Studies have shown that high humidity is a condition that aggravates the pain of rheumatoid arthritis (RA), but the relevant mechanism is controversial. Currently, there is a lack of experimental animal studies on high humidity as an adverse factor related to the pathogenesis of RA. We used healthy SD rats and collagen-induced arthritis (CIA) rats to investigate the effects of high humidity on arthritis. Integrated metabolomics analyses of faeces and 16S rRNA sequencing of the faecal microbiota were performed to comprehensively assess the diversity of the faecal microbiota and metabolites in healthy and CIA rats. In this study, high humidity aggravated arthritis in CIA rats, which manifested as articular cartilage lesions, increased arthritis scores, and an increase in proinflammatory cytokines. High humidity had a certain effect on the articular cartilage extent, arthritis score and proinflammatory cytokines of healthy rats as well. Furthermore, high humidity caused significant changes in faecal microbes and metabolites in both healthy and CIA rats. 16S rRNA sequencing of faecal samples showed that high humidity increased the amount of inflammation-related bacteria in healthy and CIA rats. Faecal metabolomics results showed that high humidity significantly altered the level of faecal metabolites in healthy rats and CIA rats, and the changes in biological functions were mainly related to the inflammatory response and oxidative stress. Combined analysis showed that there was a strong correlation between the faecal microbiota and faecal metabolites. High humidity is an adverse factor for the onset and development of RA, and its mechanism is related to the inflammatory response and oxidative stress. However, the question of how high humidity impacts RA pathogenesis needs to be further investigated.

Poly-gamma-glutamic acid biopolymer: a sleeping giant with diverse applications and unique opportunities for commercialization

Poly-gamma-glutamic acid (γ-PGA) is a biodegradable, non-toxic, ecofriendly, and non-immunogenic biopolymer. Its phenomenal properties have gained immense attention in the field of regenerative medicine, the food industry, wastewater treatment, and even in 3D printing bio-ink. The γ-PGA has the potential to replace synthetic non-degradable counterparts, but the main obstacle is the high production cost and lower productivity. Extensive research has been carried out to reduce the production cost by using different waste; however, it is unable to match the commercialization needs. This review focuses on the biosynthetic mechanism of γ-PGA, its production using the synthetic medium as well as different wastes by L-glutamic acid-dependent and independent microbial strains. Furthermore, various metabolic engineering strategies and the recovery processes for γ-PGA and their possible applications are discussed. Finally, highlights on the challenges and unique approaches to reduce the production cost and to increase the productivity for commercialization of γ-PGA are also summarized.

Comparative evaluation of two collagen-based biomaterials with different compositions used for bone graft: An experimental animal study

A large number of materials with different compositions and shapes have been proposed and studied for the purpose of bone tissue regeneration. Collagen-based materials have shown promising results for this application, with improved physicochemical properties. The aim of the present in vivo animal study was to evaluate and compare two commercially available collagen-based biomaterials for bone regeneration, with these being implanted in circumferential bone defects created in the calvarium of rabbits. Twenty rabbits received bilateral parietal osteotomies, performed with the aid of a 6.5 mm diameter trephine. Two groups were created: the BC group, where the defect was filled with a scaffold composed of 90% bovine bone particles and 10% porcine collagen, and the EG group, where the defect was filled with a scaffold composed of 75% hydroxyapatite particles of bovine origin and 25% bovine collagen. Ten animals were sacrificed at 30 days and another 10 at 45 days after implantation, and the samples were processed and histologically analyzed. In the evaluations of the samples at 30 days, no important differences were found in the results. However, in the samples at 45 days after surgery, the EG group showed better results than the BC group samples, mainly in terms of the amount of bone matrix formation (P < 0.0001) and the volume in area measured in each sample, where the EG group had a value 65% higher than that in the BC group samples. Based on the results obtained, we conclude that the amount of collagen and the particle characteristics present in the composition of the scaffolds can directly influence the amount of neoformation and/or bone regeneration.

Glutamine metabolite α-ketoglutarate acts as an epigenetic co-factor to interfere with osteoclast differentiation

Osteoclasts (OCs) have been well-known involved in the exacerbation of bone-related diseases. However, the role of metabolites on osteoclastogenesis has not been well characterized. Herein, we found osteoclastogenesis was negatively regulated by α-ketoglutarate (αKG) in vitro and in vivo (C57BL/6 mouse). Kinetic transcriptome analysis revealed the upregulation of solute carrier family 7 member 11 (Slc7a11), a subunit of the cysteine/glutamate antiporter, as well as the downregulation of typical OC maker genes through αKG treatment. Given that Slc7a11 could control ROS level through glutathione import, we measured intracellular ROS, then RANKL-induced ROS production was inhibited by αKG. Notably, we highlight that αKG plays an epigenetic co-factor at the Slc7a11 promoter by demethylating repressive histone H3K9 methylation and simultaneously increasing the nuclear factor erythroid 2-related factor (Nrf2) binding, a critical transcription factor through chromatin immunoprecipitation (ChIP) analysis. Together, we suggested that αKG could be a therapeutic strategy for OC activated diseases.

Hidrogeles de colágeno acoplados con hidroxiapatita para aplicaciones en ingeniería tisular

Los hidrogeles basados en colágeno son redes tridimensionales (3D) con la capacidad de absorber agua y una alta biocompatibilidad para utilizarlos en la reparación de tejidos dañados. Estos materiales presentan pobres propiedades mecánicas y velocidades de degradación rápidas, limitando su aplicación a estrategias de ingeniería tisular y biomedicina; por ésto, la incorporación de fases inorgánicas en la matriz 3D del colágeno como la hidroxiapatita ha contribuido en la mejora de sus propiedades, incrementado la eficiencia de los hidrogeles híbridos obtenidos. Este trabajo, presenta las contribuciones más relevantes relacionadas con los sistemas de hidrogeles basados en colágeno y partículas de hidroxiapatita dispersas dentro de la matriz colagénica, lo que evidencia que la combinación de los materiales no altera la biocompatibilidad y biodegradabilidad típicas del colágeno, permitiendo la adhesión, proliferación, crecimiento celular y control del metabolismo de las células implicadas en los procesos de una reparación ósea, presentando a los hidrogeles como una estrategia para su uso potencial en la ingeniería tisular.

Osteogenic, Angiogenic, and Antibacterial Bioactive Nano-Hydroxyapatite Co-Synthesized Using γ-Polyglutamic Acid and Copper

Nano-antibacterial calcium phosphate (CaP) has attracted intense attention with regard to its wide variety of medical and biological applications. The γ-polyglutamic acid and copper cosynthesized hydroxyapatite (γ-PGA/Cu_xHAp) was synthesized using the wet method. Structural and chemical characterizations demonstrate that copper was quantitatively incorporated into the hydroxyapatite structure, and the degree of Cu substitution was up to 20 mol % in the synthesized nanocrystals. Morphology characterization showed that the size of the γ-PGA/Cu_xHAp nanoparticles decreases with the increased copper content. γ-PGA/Cu_xHAp exhibited a steady release of Cu ions. Two experimental protocols were applied to compare the antibacterial activity of the γ-PGA/Cu_xHAp samples. A positive correlation was observed between Cu content and the inhibition of bacterial growth. The study also showed that nanoparticles with smaller particle sizes exhibited higher antibacterial activities than the larger particles. Endothelial and osteoblast cells rapidly proliferated on γ-PGA/Cu_xHAp, whereas high concentrations (20 mol %) of Cu ions reduced cell proliferation. In the rat calvarial defect model, some γ-PGA/Cu_xHAp samples such as γ-PGA/Cu_xHAp (x = 8, 16) showed efficient bone regeneration capacities at 12 weeks post implantation. Thus, the multibiofunctional γ-PGA/Cu_xHAp nanocomposite exhibited degradative, angiogenic, bactericidal and bone regenerative properties, providing a potential means to address some of the critical challenges in the field of bone tissue engineering.

The bio-processing of soybean dregs by solid state fermentation using a poly γ-glutamic acid producing strain and its effect as feed additive

Soybean dregs are restricted as feed additives because they contain anti-nutrient factors. Herein, soybean dreg was bio-transformed by solid-state fermentation (SSF) using a poly γ-glutamic acid (γ-PGA) producing stain Bacillus amyloliquefaciens NX-2S. The maximum γ-PGA production of 65.79 g/kg was reached in a 5 L fermentation system while the conditions are 70% initial moisture of soybean dregs with addition of molasses meal, 12% inoculum size, 30 °C fermentation temperature, initial pH of 8, and 60 h fermentation time. Meanwhile, continuous batch fermentation was proved feasible. After SSF, the anti-nutritional factors such as trypsin inhibitor, phytic acid and tannin were reduced by 98.7%, 97.8%, and 63.2%, respectively. Compared with unfermented soybean dregs, adding fermented soybean dregs to feed increased the average weight gain of rats by 15.6% and reduced the ratio of feed to meat by 11.3%. Therefore, this study provided a feasible strategy for processing soybean dregs as feed additive.