Association Between Gut Microbiota and Osteoarthritis: A Review of Evidence for Potential Mechanisms and Therapeutics

Lactobacillus kefiranofaciens and its enhancement effect on the anti-inflammatory function of CII/Gln in MIA-induced osteoarthritis by protecting the intestinal barrier and gut microecology

Osteoarthritis (OA) is a globally chronic disease affecting middle-aged and elderly individuals, with growing evidences implicating gut microbiota in its pathogenesis. Lactobacillus kefiranofaciens ZW3 (ZW3) shows potential in modulating gut microbiota, protecting intestinal barrier, and regulating immunity. This study explored the therapeutic effects of ZW3, alone and combined with CII/Gln, using a monoiodoacetate (MIA)-induced OA model. Results indicated that ZW3 significantly mitigated cartilage damage and inflammation alone or combined with CII/Gln, possibly by improving intestinal integrity, reduced oxidative stress, and regulated MMPs expression. 16S rDNA sequencing showed ZW3, especially with CII/Gln, increased beneficial bacteria of Ruminococcaceae and Lachnospiraceae abundances. Furthermore, ZW3 or with CII/Gln elevated SCFAs levels in intestinal contents in OA rats. These findings propose a novel probiotic-based strategy, potentially combined with functional foods, for OA intervention and treatment.

The Role of G Protein-Coupled Receptors in the Regulation of Orthopaedic Diseases by Gut Microbiota

Exercise and diet modulate the gut microbiota, which is involved in the regulation of orthopaedic diseases and synthesises a wide range of metabolites that modulate cellular function and play an important role in bone development, remodelling and disease. G protein-coupled receptors (GPCRs), the largest family of transmembrane receptors in the human body, interact with gut microbial metabolites to regulate relevant pathological processes. This paper provides a review of different dietary and exercise effects on the pathogenic gut microbiota and their metabolites associated with GPCRs in orthopaedic diseases. RESULTS: Generally, metabolites produced by gut microbiota contribute to the maintenance of bone health by activating the corresponding GPCRs, which are involved in bone metabolism, regulation of immune response, and maintenance of gut flora homeostasis. Exercise and diet can influence gut microbiota, and an imbalance in gut microbiota homeostasis can trigger a series of adverse immune and metabolic responses by affecting GPCR function, ultimately leading to the onset and progression of various orthopaedic diseases. Understanding these relationships is crucial for elucidating the pathogenesis of orthopaedic diseases and developing personalised probiotic-based therapeutic strategies. In the future, we should further explore how to prevent and treat orthopaedic diseases through GPCR-based modulation of gut microbes and their interactions. The development of substances that precisely modulate gut microbes through different exercises and diets will provide more effective interventions to improve bone health in patients.

A new approach to osteoarthritis: gut microbiota

OBJECTIVE

Studies investigating the relationship between the gut microbiome and osteoarthritis have increased in recent years. However, data on the relationship between joints and the gut microbiome are limited. The aim of this study was to determine whether there is a relation between knee joint fluid and gut microbiota in patients with knee osteoarthritis.

METHODS

This study included 40 individuals, 20 of whom were diagnosed with knee osteoarthritis and 20 of whom were considered healthy controls. Joint-fluid and stool samples were taken from the participants. Bacteria isolated from the samples were identified using a matrix-assisted laser desorption ionization-time of flight-mass spectrometry device.

RESULTS

Twenty-nine different bacteria were isolated from the stool samples and five bacteria were isolated from the joint-fluid samples. In our study, the same types of microorganisms (Enterococcus faecium and Staphylococcus hominis) were isolated from the stool and joint-fluid samples.

CONCLUSION

The data obtained in our study shed light on the uncertainty of how microorganisms, especially those identified in the knee and hip in the literature, reach these regions. The presence of intestinal bacteria in the knee joint fluid of osteoarthritis patients indicates that intestinal bacteria, especially in individuals with a weak immune system, malnutrition, and obesity, pass through the intestinal wall and reach other parts of the body via the bloodstream, a condition also known as "leaky gut."

Butyrate (short-chain fatty acid) alleviates lipopolysaccharide-binding proteins and improves physical function in knee osteoarthritis patients

Knee-osteoarthritis (OA) is often associated with increased intestinal permeability, potentially causing sarcopenia, and mobility issues. Current treatments are ineffective. The objective of this study was to investigate if butyrate improves sarcopenia and physical function in knee-OA patients, and if improvements correlate with changes in gut health, specifically intestinal permeability, and bacterial load. In this double-blind study, 60 OA patients received placebo, 52 received 300 mg butyrate daily for 12-weeks. Gut health (zonulin), and systemic bacterial load (lipopolysaccharide-binding proteins (LBP)) were assessed. Handgrip strength (HGS), Oxford knee scores (OKS), and short physical performance battery (SPPB) were measured at the beginning and end of the study to assess physical functionality. Patients taking butyrate showed improvement in HGS, walking speed, OKS scores, and maintained a better balance, walking ability and no decline in rising from chair, according to SPPB-scores. Butyrate lowered blood levels of zonulin, LBP, and CRP as markers of intestinal permeability, bacterial load, and inflammation, respectively (all p < 0.05). Regression analysis exhibited marked correlations of zonulin with HGS, OKS, walking speed, and SPPB scores in the butyrate-treated group. These observations suggest that butyrate could serve as a therapeutic option for sarcopenia and physical decline in OA, potentially by improving intestinal barrier function.

Gut and Joint Microbiomes: Implications in Osteoarthritis

This review summarizes and discusses key recent findings suggesting that microbiomes can play a role in the development and progression of osteoarthritis. Evidence supporting a gut microbiome-joint connection derived from human and animal studies is enumerated and discussed, with particular attention on the microbial and molecular basis for the development of therapeutic interventions that involve targeting the gut. Additionally, clinical data supporting the concept of a living microbiome within a diarthrodial joint are summarized. A discussion of key limitations in the current data and important technical considerations for firmly establishing the existence of a synovial joint microbial community is included.

Association between dietary index for gut microbiota and osteoarthritis in the US population: the mediating role of systemic immune-inflammation index

Objective

Osteoarthritis (OA) is one of the most prevalent chronic conditions among the elderly. The dietary index for gut microbiota (DI-GM) is a novel proposed indicator reflecting gut microbiome diversity. However, the role of DI-GM in OA remains unclear. This study thus aims to explore the association between DI-GM and the risk of OA and analyze the mediating roles of systemic immune-inflammation index (SII).

Methods

We utilized data from the National Health and Nutrition Examination Survey (NHANES) spanning 2007-2018. OA was assessed through self-reported questionnaires, and dietary recall data were used to calculate the DI-GM. Univariate and weighted multivariate logistic regression analyses were employed to evaluate the association between DI-GM and OA, the weighted linear regression analyses were employed to investigate the association of DI-GM with SII, while restricted cubic splines (RCS) curves were used to assess the non-linear relationship between these variables. Subgroup analyses were subsequently conducted to validate the robustness of the findings. Mediation analysis evaluated the role of SII.

Results

This study included 15,875 participants, revealing a significant inverse association between the DI-GM and OA risk (p < 0.001), higher DI-GM demonstrated a substantially reduced OA risk (adjusted model OR: 0.83; 95% CI: 0.79-0.86) and were negatively associated with the SII [β (95% CI): -9.2 (-13.0, -2.0)]. The RCS curve indicated a non-linear relationship between DI-GM and OA risk. Subgroup analysis showed that various demographic and clinical factors did not significantly alter the association between DI-GM and OA risk (interaction p-value > 0.05). The mediating effect of SII accounted for 12.69% of association between DI-GM and OA.

Conclusion

This study found a significant negatively association between DI-GM and OA prevalence in the US population. Mediation analyses demonstrated a significant mediating effect of SII.

Clinical efficacy of probiotic supplementation in the treatment of knee osteoarthritis: a meta-analysis

Background

We aimed to systematically evaluate and analyze the clinical efficacy of oral probiotics in the treatment of knee osteoarthritis (KOA) based on the theory of "gut-joint axis."

Methods

We searched PubMed, The Cochrane Library, Embase, China Knowledge Network (CNKI), Wanfang Database, and Wipro Database (CQVIP) databases for clinical randomized controlled trials of oral probiotics for the treatment of KOA. The literature was organized by Note express software, and the quality of the included literature was evaluated according to the Cochrane systematic evaluation method, and meta-analysis was performed using RevMan 5.4 software.

Results

Five randomized controlled trials with 694 participants were included in this study, and the results of the meta-analysis showed that the observation group experienced significant reductions in the Western Ontario and McMaster Universities Osteoarthritis Index total score, visual analog score, and high-sensitivity C-reactive protein level compared to the control group, but did not show significant differences in improvement of stiffness and regulation of body weight.

Conclusion

Oral probiotics had an ameliorative effect on function, pain, and inflammatory response in patients with KOA, but our results need to be validated in future large-scale studies.

Systematic review registration

The website is https://www.crd.york.ac.uk/PROSPERO/.

AMP1-1 alleviates bone loss in weightless rats by reducing peripheral 5-HT content via the microbiota-gut-bone axis

BACKGROUND

Weightlessness-induced bone loss (WIBL) refers to the reduction of bone mass and the decline of bone resistance to load in a weightless environment. However, current treatment strategies aimed at increasing bone mass are associated with various limitations and side effects, highlighting the urgent need for safer and more effective therapeutic options to address WIBL.

PURPOSE

We aimed to further explore the potential mechanism of the anti-WIBL effect of Atractylodes macrocephalon polysaccharide1-1(AMP1-1). To find a better way to treat WIBL and provide new insights for the development of therapeutic drugs for this condition.

METHODS

Firstly, the anti-weightlessness bone loss of AMP1-1 was verified by micro-computed tomography (Micro-CT), three-point mechanical bending test and Western Blot (WB). Subsequently, the intestinal barrier was examined using histopathology, immunohistochemistry (IHC), and WB. Finally, validation experiments were performed using fecal microbiota transplantation (FMT). After FMT, 16S rDNA sequencing was used to analyze the gut microbiota composition in the rat feces.

RESULTS

AMP1-1 was able to inhibit WIBL by enhancing bone mass, improving toughness, and increasing osteogenic activity. Meanwhile, AMP1-1 reduced peripheral 5-HT content by restoring enterochromaffin cell function through gut microbiota regulation and tight junction repair. FMT of rat fecal microbiota after gavage of AMP1-1 into tail suspension rats still has the effects of regulating gut microbiota, repairing intestinal barrier and reducing bone loss.

CONCLUSION

Our results demonstrate that AMP1-1 exerts a protective effect against WIBL in rats, potentially by modulating 5-HT content and 5-HT-related metabolism in bone tissue through microbiota-gut-bone axis. This study is the first to elucidate the mechanism of AMP1-1 in mitigating WIBL through the perspective of the microbiota-gut-bone axis. Moreover, this research integrates plant extract research with the issue of bone loss induced by microgravity (aerospace medicine), thereby opening new avenues for natural drug research.

The gut microbiome and osteoarthritis

Osteoarthritis (OA) is one of the most common degenerative diseases, and the number of patients has been constantly increasing. Non-steroidal anti-inflammatory drugs, glucocorticosteroids, opioids, etc., and surgical procedures, e.g. arthroplasty, are among the most common methods of treatment. There are reasons to believe that the gut microbiome (GMB) may influence inflammatory processes occurring in the pathomechanism of OA. The inflammatory processes occurring in the intestines may lead to disruption of tight junctions and increased concentrations of pro-inflammatory cytokines, resulting in increased permeability of intestines, causing low-grade inflammation, including in the joints. Methods of altering the GMB composition to reduce the inflammatory and joint degenerative processes are known only to some extent, and long-term research is required. Osteoarthritis, a particularly well-known and very widespread disease due to the aging population, is characterized by moderate and local inflammation. It occurs due to the effects of biomechanical cartilage wear with damage of joint structures, primarily through degenerative processes. OA represents a therapeutic challenge, and any element that can influence its inhibition is highly sought after. Therefore, these methods seem to offer a promising additional approach to treatment.

Relationship Between the Gut Microbiome, Tryptophan-Derived Metabolites, and Osteoarthritis-Related Pain: A Systematic Review with Meta-Analysis

INTRODUCTION

Osteoarthritis (OA) is the most prevalent form of arthritis and affects over 528 million people worldwide. Degenerative joint disease involves cartilage degradation, subchondral bone remodeling, and synovial inflammation, leading to chronic pain, stiffness, and impaired joint function. Initially regarded as a "wear and tear" condition associated with aging and mechanical stress, OA is now recognized as a multifaceted disease influenced by systemic factors such as metabolic syndrome, obesity, and chronic low-grade inflammation. Recent studies have focused on the gut-joint axis to investigate how the gut microbiome modulates inflammation and pain in OA.

MATERIALS AND METHODS

A systematic review was conducted following the PRISMA guidelines and was registered with PROSPERO (CRD42024556265). This review included studies involving adults with symptomatic OA and analyzed the relationship between the gut microbiome and OA-related pain. Randomized and non-randomized clinical trials, case reports, editorials, and pilot studies were excluded. Searches were performed in PubMed, Cochrane Library, and Web of Science without publication date restrictions, and filtered for "observational studies". The study selection and data extraction were performed by two independent researchers, and the risk of bias was assessed using appropriate tools.

RESULTS

Five observational studies were included in the systematic review, and three were included in the meta-analysis. Two studies reported an association between different tryptophan metabolites and pain levels in patients with OA. Two other studies demonstrated a correlation between lipopolysaccharide levels and pain in OA. A fifth study confirmed the relationship between Streptococcus relative abundance of Streptococcus spp. and knee pain. These results were not supported by a meta-analysis, which found no significant association between the presence of pain in OA and the presence of bacilli of the genus Streptococcus or plasma markers of the tryptophan pathway.

CONCLUSIONS

Current evidence indicates a potential link between gut microbiome dysbiosis and OA-related pain. However, methodological limitations preclude definitive conclusions. Further research using advanced techniques and larger cohorts is needed to validate and extend these findings and elucidate the underlying mechanisms. Targeted manipulation of the gut microbiome may be a valuable strategy for pain management in OA patients.

Potential role of gut-related factors in the pathology of cartilage in osteoarthritis

Osteoarthritis (OA) is a common progressive degenerative disease. Gut microbiota (GM) and their metabolites have been closely associated with the onset, progression, and pathology of OA. GM and their metabolites may influence the cartilage directly, or indirectly by affecting the gut, the immune system, and the endocrine system. They function through classical pathways in cartilage metabolism and novel pathways that have recently been discovered. Some of them have been used as targets for the prevention and treatment of OA. The current study sought to describe the major pathological signaling pathways in OA chondrocytes and the potential role of gut-related factors in these pathways.

Evaluation of the protective effects of chondroitin sulfate oligosaccharide against osteoarthritis via inactivation of NLRP3 inflammasome by in vivo and in vitro studies

Osteoarthritis (OA) is the most prevalent degenerative arthritis disease linked to aging, obesity, diet, and accumulation of octacalcium phosphate (OCP) crystals in joints. Current research has focused on inflammation and chondrocytes apoptosis as underlying OA mechanisms. Inflammatory cytokines like IL-1β activate matrix metalloproteinase-13 (MMP-13) and aggrecanase (the member of A Disintegrin and Metalloproteinase with Thrombospondin motifs family, ADAMTS), leading to cartilage matrix degradation. The NLRP3 inflammasome also contributes to OA pathogenesis by maturing IL-1β. Natural products like chondroitin sulfate oligosaccharides (oligo-CS) show promise in OA treatment by inhibiting inflammation. Our study evaluates the protective effects of oligo-CS against OA by targeting NLRP3 inflammation. Stimulating human SW1353 chondrocytes and human mononuclear macrophage THP-1 cells with OCP showed increased NLRP3 inflammation initiation, NF-κB pathway activation, and the production of inflammatory cytokines (IL-1β, IL-6) and the metabolic index (MMP-13, ADAMTS-5), leading to cartilage matrix degradation. However, oligo-CS treatment significantly reduced inflammation. In a 28-day in vivo study with C57BL/6 female mice, OCP was injected into their right knee and oligo-CS was orally administered. The OCP group exhibited significant joint space narrowing and chondrocyte loss, while the oligo-CS group maintained cartilage integrity. Oligo-CS groups also regulated gut microbiota composition to a healthier state. Taken together, our findings suggest that oligo-CS can be considered as a protective compound against OA.

Live and Dead Clostridium butyricum GKB7 Diminish Osteoarthritis Pain and Progression in Preclinical Animal Model

Osteoarthritis (OA) is a degenerative joint disease primarily affecting the elderly. It is characterized by the progressive decline of joint cartilage and alterations in the underlying bone. Several probiotic strains have exhibited immunomodulatory and anti-inflammatory properties. Here, we examined the functions of live and dead Clostridium butyricum GKB7 (GKB7-L and GKB7-D) in a preclinical anterior cruciate ligament transection (ACLT)-enhanced OA procedure. Oral administration of GKB7-L and GKB7-D ameliorated ACLT-induced bone pain as assessed by weight-bearing behavioral testing but did not affect body weight. Micro-computed tomography (CT) results showed that GKB7-L and GKB7-D diminished ACLT-induced bone destruction and loss. GKB7-L and GKB7-D-enriched therapies also reduced ACLT-induced production of the pro-inflammatory cytokines interleukin (IL)-1β and tumor necrosis factor (TNF)-α, as well as the chondrolytic factor matrix metalloproteinase (MMP)-3, leading to inhibition of aggrecan and collagen type II degradation and thereby blocking cartilage breakdown. We therefore suggest that oral supplementation with GKB7-L or GKB7-D can be beneficial in the prevention and treatment of OA.

Bioactive Compounds and Their Chondroprotective Effects for Osteoarthritis Amelioration: A Focus on Nanotherapeutic Strategies, Epigenetic Modifications, and Gut Microbiota

In degenerative joint disease like osteoarthritis (OA), bioactive compounds like resveratrol, epigallocatechin gallate, curcumin, and other polyphenols often target various signalling pathways, including NFκB, TGFβ, and Wnt/β-catenin by executing epigenetic-modifying activities. Epigenetic modulation can target genes of disease pathophysiology via histone modification, promoter DNA methylation, and non-coding RNA expression, some of which are directly involved in OA but have been less explored. OA patients often seek options that can improve the quality of their life in addition to existing treatment with nonsteroidal anti-inflammatory drugs (NSAIDs). Although bioactive and natural compounds exhibit therapeutic potential against OA, several disadvantages loom, like insolubility and poor bioavailability. Nanoformulated bioactive compounds promise a better way to alleviate OA since they also control systemic events, including metabolic, immunological, and inflammatory responses, by modulating host gut microbiota that can regulate OA pathogenesis. Recent data suggest gut dysbiosis in OA. However, limited evidence is available on the role of bioactive compounds as epigenetic and gut modulators in ameliorating OA. Moreover, it is not known whether the effects of polyphenolic bioactive compounds on gut microbial response are mediated by epigenetic modulatory activities in OA. This narrative review highlights the nanotherapeutic strategies utilizing bioactive compounds, reporting their effects on chondrocyte growth, metabolism, and epigenetic modifications in osteoarthritis amelioration.

Basal metabolic rate mediates the causal relationship between gut microbiota and osteoarthritis: a two-step bidirectional Mendelian randomization study

Background

The relationship between gut microbiota and osteoarthritis (OA) occurrence remains unclear. Existing research needs to clearly understand how basal metabolic rate (BMR) regulates this relationship. Therefore, using a two-step bidirectional Mendelian Randomization approach, our study aims to investigate whether BMR levels mediate the causal relationship between gut microbiota and OA.

Methods

In this study, we examined publicly available summary statistics from Genome-Wide Association Studies (GWAS) to determine the correlation between gut microbiota and OA. The analysis included one primary dataset and two secondary datasets. Initially, a two-step, two-sample, and reverse MR analysis was performed to identify the causal relationship between gut microbiota and OA. Subsequently, a two-step MR analysis revealed that the relationship between microbiota and OA is mediated by BMR. Sensitivity analyses confirmed the robustness of the study results.

Results

In our analysis of the primary dataset, we discovered a positive correlation between three taxa and the outcome of OA, and eight taxa exhibited a negative correlation with the OA outcome. Through comparisons with the secondary dataset and multiple testing corrections, we found a negative association between the class Actinobacteria (OR=0.992886277, p-value = 0.003) and the likelihood of OA occurrence. Notably, knee osteoarthritis (KOA) and hip osteoarthritis (HOA) had a strong negative correlation (OR = 0.927237553/0.892581219). Our analysis suggests that BMR significantly mediates the causal pathway from Actinobacteria to OA, with a mediated effect of 2.59%. Additionally, BMR mediates 3.98% of the impact in the path from the order Bifidobacteriales and the family Bifidobacteriaceae to OA. Besides these findings, our reverse analysis did not indicate any significant effect of OA on gut microbiota or BMR.

Conclusion

Our research results indicate that an increase in the abundance of specific gut microbial taxa is associated with a reduced incidence of OA, and BMR levels mediate this causal relationship. Further large-scale randomized controlled trials are necessary to validate the causal impact of gut microbiota on the risk of OA. This study provides new insights into the potential prevention of OA by modulating the gut microbiota.

Metformin effects on plasma zonulin levels correlate with enhanced physical performance in osteoarthritis patients with diabetes

PURPOSE

Metformin (MTF) shows promise in protecting against physical decline in osteoarthritis (OA), but how it works remains unclear. We studied MTF's effects on gut permeability and its link to physical performance in OA patients.

METHODS

We studied four groups: control (n = 72), OA non-diabetic (n = 58), OA diabetic on MTF (n = 55), and OA diabetic on other anti-diabetics (n = 57). We measured zonulin levels, as intestinal permeability marker, hand-grip strength (HGS), Oxford knee scoring (OKS) to determine OA severity, and short performance physical battery (SPPB) to determine physical functions.

RESULTS

Patients suffering from OA showed a reduction in HGS and SPPB scores with raised plasma zonulin than controls, irrespective of disease severity. MTF decreased plasma zonulin levels and improved OKS, gait speed, HGS, and SPPB scores in OA patients. However, OA patients taking other anti-diabetic medications demonstrated higher levels of plasma zonulin, reduced HGS, and SPPB scores. Furthermore, a robust correlation of plasma zonulin and HGS, OKS, gait speed, and SPPB scores in OA patients on MTF was observed. Moreover, we found reduced oxidative stress and inflammation associated with these alterations in OA patients treated with MTF.

CONCLUSION

MTF improves HGS and physical performance by lowering zonulin levels, preserving gut permeability in OA patients.

Exploring the Interconnection between Metabolic Dysfunction and Gut Microbiome Dysbiosis in Osteoarthritis: A Narrative Review

Osteoarthritis (OA) is a prevalent joint disorder and the most common form of arthritis, affecting approximately 500 million people worldwide, or about 7% of the global population. Its pathogenesis involves a complex interplay between metabolic dysfunction and gut microbiome (GM) alterations. This review explores the relationship between metabolic disorders-such as obesity, diabetes, and dyslipidemia-and OA, highlighting their shared risk factors, including aging, sedentary lifestyle, and dietary habits. We further explore the role of GM dysbiosis in OA, elucidating how systemic inflammation, oxidative stress, and immune dysregulation driven by metabolic dysfunction and altered microbial metabolites contribute to OA progression. Additionally, the concept of "leaky gut syndrome" is discussed, illustrating how compromised gut barrier function exacerbates systemic and local joint inflammation. Therapeutic strategies targeting metabolic dysfunction and GM composition, including lifestyle interventions, pharmacological and non-pharmacological factors, and microbiota-targeted therapies, are reviewed for their potential to mitigate OA progression. Future research directions emphasize the importance of identifying novel biomarkers for OA risk and treatment response, adopting personalized treatment approaches, and integrating multiomics data to enhance our understanding of the metabolic-GM-OA connection and advance precision medicine in OA management.

Microbiome and Femoral Cartilage Thickness in Knee Osteoarthritis: Is There a Link?

OBJECTIVE

To assess the relation between microbiome and lipopolysaccharide (LPS), in the blood and synovial fluid (SF) with femoral cartilage thickness (FCT) measured by ultrasound (US) in knee osteoarthritis (KOA) patients.

METHODS

This cross-sectional study included 40 primary KOA patients recruited between September 2022 and June 2023. Age, gender, and body mass index (BMI) were recorded. Patients underwent full clinical examination, standing plain x-ray of the knee joint and knee US examination to measure medial, intercondylar, and lateral FCT. Microbiomes (specific bacterial phyla) were detected by real-time polymerase chain reaction and LPS levels were measured by enzyme-linked immunosorbent assay kit in the patients' serum and SF.

RESULTS

The patient's age ranged from 43 to 72 years. Most patients were females (72.5%), with a mean BMI of 35.8 ± 6.21 kg/m2. The mean medial, intercondylar, and lateral FCT were less than cut-off values. All 40 (100%) patients showed positive bacterial deoxyribonucleic acid (16S ribosomal RNA) in both blood and SF samples. Firmicutes was the most abundant in patients' blood (48.49%) and SF (63.59%). The mean serum LPS level was significantly higher compared to mean SF LPS (t =4.702, P < 0.001). There was a statistically significant negative correlation between lateral FCT and Firmicutes relative abundance in both patients' blood and SF.

CONCLUSION

Microbiome and LPS are present in the blood and SF of primary KOA patients. Microbiome (Firmicutes) was associated with decreased lateral FCT. This might provide a potential link between both systemic and local microbiomes and cartilage affection in KOA patients.

Intermittent Fasting Targets Osteocyte Neuropeptide Y to Relieve Osteoarthritis

Osteoarthritis is a highly prevalent progressive joint disease that still requires an optimal therapeutic approach. Intermittent fasting is an attractive dieting strategy for improving health. Here this study shows that intermittent fasting potently relieves medial meniscus (DMM)- or natural aging-induced osteoarthritic phenotypes. Osteocytes, the most abundant bone cells, secrete excess neuropeptide Y (NPY) during osteoarthritis, and this alteration can be altered by intermittent fasting. Both NPY and the NPY-abundant culture medium of osteocytes (OCY-CM) from osteoarthritic mice possess pro-inflammatory, pro-osteoclastic, and pro-neurite outgrowth effects, while OCY-CM from the intermittent fasting-treated osteoarthritic mice fails to induce significant stimulatory effects on inflammation, osteoclast formation, and neurite outgrowth. Depletion of osteocyte NPY significantly attenuates DMM-induced osteoarthritis and abolishes the benefits of intermittent fasting on osteoarthritis. This study suggests that osteocyte NPY is a key contributing factor in the pathogenesis of osteoarthritis and intermittent fasting represents a promising nonpharmacological antiosteoarthritis method by targeting osteocyte NPY.

Anti-Inflammatory Effects of Boric Acid in Treating Knee Osteoarthritis: Biochemical and Histopathological Evaluation in Rat Model

This study aimed to examine the anti-inflammatory properties of boric acid (BA) in treating knee osteoarthritis (KOA) in rats, evaluating its biochemical and histopathological therapeutic effects. A KOA rat model was induced by injecting monosodium iodoacetate into the knee joint. Random assignment was performed for the experimental groups as follows: group-1(control), group-2(KOA control), group-3 (BA:4 mg/kg, orally), group-4(BA:10 mg/kg, orally), group-5(BA:4 mg/kg, intra-articularly), and group-6(BA:10 mg/kg, intra-articularly). The rats received 100 µL of BA intra-articularly on days 1, 7, 14, and 21 or 1 mL orally once a day (5 days/week) for 4 weeks. Serum levels of interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), and activity of matrix metalloproteinase-13 (MMP-13) were measured. Histopathological and immunohistochemical analyses were performed on knee joint samples using specific antibodies for IL-1β, TNF-α, MMP-13, and nitric oxide synthase-2 (NOS-2). Group-2 exhibited higher serum IL-1β and TNF-α levels and MMP-13 activity than group-1 (P < 0.05). However, IL-1β and TNF-α levels and MMP-13 activity were lower in all treatment groups than in group-2, with statistically significant reductions observed in groups-4, 5, and 6. Histopathologically, group-2 displayed joint space narrowing, cartilage degeneration, and deep fissures. Groups-5 and 6 demonstrated significant joint space enlargement, articular cartilage tissue regeneration, and immunostaining patterns similar to those in group-1. Immunohistochemically, group-2 showed significant increases in IL-1β, TNF-α, MMP-13, and NOS-2 expression. However, all treatment groups exhibited reductions in these expression levels compared to group-2, with statistically significant decreases observed in groups-5 and 6 (P < 0.01). BA shows potential efficacy in reducing inflammation in experimental KOA model in rats. It may be a promising therapeutic agent for KOA, warranting further clinical studies for validation.

The influence of gut microbiome on periprosthetic joint infections: State-of-the art

Early periprosthetic joint infection constitutes one of the most frightening complications of joint replacement. Recently, some evidence has highlighted the potential link between dysregulation of the gut microbiota and degenerative diseases of joints. It has been hypothesized that microbiome dysbiosis may increase the risk of periprosthetic joint infection by facilitating bacterial translocation from these sites to the bloodstream or by impairing local or systemic immune responses. Although the processes tying the gut microbiome to infection susceptibility are still unknown, new research suggests that the presurgical gut microbiota-a previously unconsidered component-may influence the patient's ability to resist infection. Exploring the potential impact of the microbiome on periprosthetic joint infections may therefore bring new insights into the pathogenesis and therapy of these disorders. For a successful therapy, a proper surgical procedure in conjunction with an antibacterial concept is essential. As per the surgical approach, different treatment strategies include surgical irrigation, debridement, antibiotic therapy, and implant retention with or without polyethylene exchange. Other alternatives could be one-stage or two-stage revisions surgery. Interventions that either directly target gut microbes as well as interventions that modify the composition and/or function of the commensal microbes represent an innovative and potentially successful field to be explored. In recent times, innovative therapeutic methods have arisen in the realm of microbiome restoration and the management of gut-related ailments. These progressive approaches offer fresh perspectives on tackling intricate microbial imbalances in the gastrointestinal tract. These emerging therapies signify a shift towards more precise and individualized approaches to microbiome restoration and the management of gut-related disorders. Once a more advanced knowledge of the pathways linking the gut microbiota to musculoskeletal tissues is gained, relevant microbiome-based therapies can be developed. If dysbiosis is proven to be a significant contributor, developing treatments for dysbiosis may represent a new frontier in the prevention of periprosthetic joint infections.

Gut-lung axis and asthma: A historical review on mechanism and future perspective

BACKGROUND

Gut microbiota are closely related to the development and regulation of the host immune system by regulating the maturation of immune cells and the resistance to pathogens, which affects the host immunity. Early use of antibiotics disrupts the homeostasis of gut microbiota and increases the risk of asthma. Gut microbiota actively interact with the host immune system via the gut-lung axis, a bidirectional communication pathway between the gut and lung. The manipulation of gut microbiota through probiotics, helminth therapy, and fecal microbiota transplantation (FMT) to combat asthma has become a hot research topic. BODY: This review mainly describes the current immune pathogenesis of asthma, gut microbiota and the role of the gut-lung axis in asthma. Moreover, the potential of manipulating the gut microbiota and its metabolites as a treatment strategy for asthma has been discussed.

CONCLUSION

The gut-lung axis has a bidirectional effect on asthma. Gut microecology imbalance contributes to asthma through bacterial structural components and metabolites. Asthma, in turn, can also cause intestinal damage through inflammation throughout the body. The manipulation of gut microbiota through probiotics, helminth therapy, and FMT can inform the treatment strategies for asthma by regulating the maturation of immune cells and the resistance to pathogens.

Current knowledge of bone-derived factor osteocalcin: its role in the management and treatment of diabetes mellitus, osteoporosis, osteopetrosis and inflammatory joint diseases

Osteocalcin (OC) is the most abundant non-collagenous and osteoblast-secreted protein in bone. It consists of two forms such as carboxylated OC (cOC) and undercarboxylated OC (ucOC). While cOC promotes bone mineralization and increases bone strength, ucOC is regarded an endocrinologically active form that may have several functions in multiple end organs and tissues. Total OC (tOC) includes both of these forms (cOC and ucOC) and is considered a marker of bone turnover in clinical settings. Most of the data on OC is limited to preclinical studies and therefore may not accurately reflect the situation in clinical conditions. For the stated reason, the aim of this review was not only to summarize current knowledge of all forms of OC and characterize its role in diabetes mellitus, osteoporosis, osteopetrosis, inflammatory joint diseases, but also to provide new interpretations of its involvement in the management and treatment of aforementioned diseases. In this context, special emphasis was placed on available clinical trials. Significantly lower levels of tOC and ucOC could be associated with the risk of type 2 diabetes mellitus. On the contrary, tOC level does not seem to be a good indicator of high bone turnover status in postmenopausal osteoporosis, osteoarthritis and rheumatoid arthritis. The associations between several pharmacological drugs used to treat all disorders mentioned above and OC levels have also been provided. From this perspective, OC may serve as a medium through which certain medications can influence glucose metabolism, body weight, adiponectin secretion, and synovial inflammation.

Role of the Gut Microbiota in Osteoarthritis, Rheumatoid Arthritis, and Spondylarthritis: An Update on the Gut-Joint Axis

Dysregulation of the gut microbiota and their metabolites is involved in the pathogenic process of intestinal diseases, and several pieces of evidence within the current literature have also highlighted a possible connection between the gut microbiota and the unfolding of inflammatory pathologies of the joints. This dysregulation is defined as the "gut-joint axis" and is based on the joint-gut interaction. It is widely recognized that the microbiota of the gut produce a variety of compounds, including enzymes, short-chain fatty acids, and metabolites. As a consequence, these proinflammatory compounds that bacteria produce, such as that of lipopolysaccharide, move from the "leaky gut" to the bloodstream, thereby leading to systemic inflammation which then reaches the joints, with consequences such as osteoarthritis, rheumatoid arthritis, and spondylarthritis. In this state-of-the-art research, the authors describe the connections between gut dysbiosis and osteoarthritis, rheumatoid arthritis, and spondylarthritis. Moreover, the diagnostic tools, outcome measures, and treatment options are elucidated. There is accumulating proof suggesting that the microbiota of the gut play an important part not only in immune-mediated, metabolic, and neurological illnesses but also in inflammatory joints. According to the authors, future studies should concentrate on developing innovative microbiota-targeted treatments and their effects on joint pathology as well as on organizing screening protocols to predict the onset of inflammatory joint disease based on gut dysbiosis.

Bacteroides salyersiae is a potent chondroitin sulfate-degrading species in the human gut microbiota

Chondroitin sulfate (CS) has widely been used as a symptomatic slow-acting drug or a dietary supplement for the treatment and prevention of osteoarthritis. However, CS could not be absorbed after oral intake due to its polyanionic nature and large molecular weight. Gut microbiota has recently been proposed to play a pivotal role in the metabolism of drugs and nutrients. Nonetheless, how CS is degraded by the human gut microbiota has not been fully characterized. In the present study, we demonstrated that each human gut microbiota was characterized with a unique capability for CS degradation. Degradation and fermentation of CS by the human gut microbiota produced significant amounts of unsaturated CS oligosaccharides (CSOSs) and short-chain fatty acids. To uncover which microbes were responsible for CS degradation, we isolated a total of 586 bacterial strains with a potential CS-degrading capability from 23 human fecal samples. Bacteroides salyersiae was a potent species for CS degradation in the human gut microbiota and produced the highest amount of CSOSs as compared to other well-recognized CS-degraders, including Bacteroides finegoldii, Bacteroides thetaiotaomicron, Bacteroides xylanisolvens, and Bacteroides ovatus. Genomic analysis suggested that B. salyersiae was armed with multiple carbohydrate-active enzymes that could potentially degrade CS into CSOSs. By using a spent medium assay, we further demonstrated that the unsaturated tetrasaccharide (udp4) produced by the primary degrader B. salyersiae could serve as a "public goods" molecule for the growth of Bacteroides stercoris, a secondary CS-degrader that was proficient at fermenting CSOSs but not CS. Taken together, our study provides insights into the metabolism of CS by the human gut microbiota, which has promising implications for the development of medical and nutritional therapies for osteoarthritis. Video Abstract.

Bile acid metabolism regulatory network orchestrates bone homeostasis

Bile acids (BAs), synthesized in the liver and modified by the gut microbiota, have been widely appreciated not only as simple lipid emulsifiers, but also as complex metabolic regulators and momentous signaling molecules, which play prominent roles in the complex interaction among several metabolic systems. Recent studies have drawn us eyes on the diverse physiological functions of BAs, to enlarge the knowledge about the "gut-bone" axis due to the participation about the gut microbiota-derived BAs to modulate bone homeostasis at physiological and pathological stations. In this review, we have summarized the metabolic processes of BAs and highlighted the crucial roles of BAs targeting bile acid-activated receptors, promoting the proliferation and differentiation of osteoblasts (OBs), inhibiting the activity of osteoclasts (OCs), as well as reducing articular cartilage degradation, thus facilitating bone repair. In addition, we have also focused on the bidirectional effects of BA signaling networks in coordinating the dynamic balance of bone matrix and demonstrated the promising effects of BAs on the development or treatment for pathological bone diseases. In a word, further clinical applications targeting BA metabolism or modulating gut metabolome and related derivatives may be developed as effective therapeutic strategies for bone destruction diseases.

[Developments in Research on the Relationship Between Matrix Metalloproteinases and Osteoarthritis]

Matrix metalloproteinases (MMPs) acquired their names because they depend on metal ions such as Ca 2+ and Zn 2+ as their cofactors. Members of this family of proteins share a similar structure consisting of five functionally distinct structural domains. MMPs, including MMP-1, MMP-3, MMP-9, and MMP-13, are key substances that promote cartilage matrix degradation and play an important role in the occurrence and progression of osteoarthritis (OA). MMPs boost the development of OA through the degradation of extracellular matrix proteins of chondrocytes, the promotion of inflammation, and other mechanisms, and are hence attracting extensive and increasing attention from the medical community. OA is a common degenerative disease that occurs in the joints and is associated with aging, metabolism, infections, genetics, exercise, and other predisposing factors. The pathological changes it causes can lead to a series of clinical symptoms such as joint pain, morning stiffness, and restricted joint movement, severely affecting patients' quality of life. The pathogenic mechanism of this highly prevalent disease is still unclear. At present, there is no effective treatment available for disease improvement. In the future, selective inhibition of MMPs, the key enzymes, may become an effective therapeutic approach. Focusing on the pathogenic effects of MMPs in OA, we herein reviewed the latest findings on the role of MMPs in the occurrence and progression of OA.

Perinatal Tissue-Derived Allografts and Stromal Cells for the Treatment of Knee Osteoarthritis: A Review of Preclinical and Clinical Evidence

OBJECTIVE

The use of perinatal-derived tissues and mesenchymal stromal cells (MSCs) as alternative treatment options to corticosteroid and hyaluronic acid injections has been gaining popularity. However, their ability to attenuate osteoarthritic (OA) symptoms while also slowing the progression of the disease remains controversial. Thus, the objective of this article is to summarize the results from both preclinical and clinical studies evaluating the efficacy of perinatal-derived tissue allografts and MSCs for the treatment of OA.

DESIGN

A comprehensive literature search was conducted on databases including Pubmed, ScienceDirect, and Google Scholar beginning in March 2020 for both preclinical and clinical studies evaluating perinatal-derived tissues and MSCs in OA. Eighteen studies met the inclusion criteria and were used for this review.

RESULTS

Both animal models and early human clinical trials demonstrated that perinatal tissues could reduce joint inflammation and pain as well as improve range of motion and function in OA. Perinatal tissue-derived MSCs in animal studies have shown the potential to support chondrocyte proliferation while also decreasing inflammatory gene and protein expression. Limited clinical results suggest perinatal tissue-derived MSC sources may also be a viable alternative or adjunct to hyaluronic acid in reducing pain and symptoms in an arthritic joint.

CONCLUSIONS

Perinatal tissue-derived allografts and MSCs have promise as potential therapeutics for mitigating OA progression. However, further research is warranted to fully define the therapeutic mechanism(s) of action and safety of these biological therapies.

The Role of AIM2 Inflammasome in Knee Osteoarthritis

Knee osteoarthritis (KOA), whose prevalence keeps rising, is still unsolved pathobiological/therapeutical problem. Historically, knee osteoarthritis was thought to be a "wear and tear" disease, while recent etiology hypotheses stressed it as a chronic, low-grade inflammatory disease. Inflammasomes mediated by the innate immunity systems have an important role in inflammatory diseases including KOA. A deluge of recent studies focused on the NLRP3 inflammasome with suggestions that its pharmacologic block would hinder degeneration. However, known inflammasomes are numerous and can also trigger IL-1β/IL-18 production and cells' pyroptotic death. Among them, AIM2 inflammasome is involved in key aspects of various acute and chronic inflammatory diseases. Therefore, while presently leaving out little-studied inflammasomes in KOA, this review focuses on the AIM2 inflammasomes that participate in KOA's complex mechanisms in conjunction with the activation of AIM2 inflammasomes in other diseases combined with the current studies on KOA mechanisms. Although human-specific data about it are relatively scant, we stress that only a holistic view including several inflammasomes including AIM2 inflammasome and other potential pathogenetic drivers will lead to successful therapy for knee osteoarthritis.

Roles of Gut Microbiome in Bone Homeostasis and Its Relationship with Bone-Related Diseases

The extended microbial genome-the gut microbiome (GM)-plays a significant role in host health and disease. It is able to influence a number of physiological functions. During dysbiosis, GM is associated with the development of various chronic diseases with impaired bone quality. In general, GM is important for bone homeostasis and can affect it via several mechanisms. This review describes the roles of GM in bone homeostasis through influencing the immune and endocrine functions, short-chain fatty acids production, calcium absorption and the gut-brain axis. The relationship between GM composition and several bone-related diseases, specifically osteoporosis, osteoarthritis, rheumatoid arthritis, diabetes mellitus, obesity and bone cancer, is also highlighted and summarized. GM manipulation may become a future adjuvant therapy in the prevention of many chronic diseases. Therefore, the beneficial effects of probiotic therapy to improve the health status of individuals with aforementioned diseases are provided, but further studies are needed to clearly confirm its effectiveness. Recent evidence suggests that GM is responsible for direct and indirect effects on drug efficacy. Accordingly, various GM alterations and interactions related to the treatment of bone-related diseases are mentioned as well.

Therapeutic Effects of Live Lactobacillus plantarum GKD7 in a Rat Model of Knee Osteoarthritis

Osteoarthritis (OA) is a painful, progressive chronic inflammatory disease marked by cartilage destruction. Certain synovial inflammatory cytokines, such as IL-1β and TNF-α, promote OA inflammation and pain. Lactobacillus spp. is a well-known probiotic with anti-inflammatory, analgesic, antioxidant, and antiosteoporotic properties. This study evaluated the therapeutic effects of a live L. plantarum strain (GKD7) in the anterior cruciate ligament transection (ACLT)-induced OA rat model. The results show that oral administration of live L. plantarum GKD7 improved weight-bearing asymmetry after ACLT surgery. Moreover, micro-computed tomography images and histopathological analysis show that oral live L. plantarum GKD7 improved subchondral bone architecture, protected articular cartilage against ACLT-induced damage, and reduced synovial inflammation. L. plantarum GKD7 also reduced IL-1β and TNF-α production in OA cartilage and synovium. Thus, orally administered live L. plantarum GKD7 appears to effectively slow the progression of OA.

Oral Administration of Clostridium butyricum GKB7 Ameliorates Signs of Osteoarthritis in Rats

Osteoarthritis (OA) is a degenerative and painful inflammatory joint disease affecting the cartilage, bone, and synovial membranes, without any effective treatment that targets the underlying mechanisms of OA. Our study evaluated the therapeutic effects of a live probiotic strain, Clostridium butyricum GKB7, administered for 6 weeks to rats with knee OA (KOA) induced by anterior cruciate ligament transection (ACLT) of the right knee. All rats underwent weekly weight-bearing behavioral testing and body weight measurements. At 6 weeks, all rats were sacrificed, and the right hind knees were collected for micro-computed tomography imaging and histopathological and immunohistochemical analyses. Compared with rats in the ACLT-only group, ACLT rats administered the probiotic exhibited dramatic improvements in pain-related behavior from postoperative week 2, had significantly less osseous and cartilaginous damage at week 6, and significantly lower levels of the inflammatory markers interleukin 1 beta (IL-1β) and tumor necrosis factor alpha (TNF-α) in cartilage and synovium sections. C. butyricum GKB7 appeared to slow or even reverse OA progression and is worth investigating as a novel therapeutic for OA.

Osteoarthritis and intestinal microbiota: pathogenetic significance of the joint — gut — microbiome axis

Introduction. Osteoarthritis (ОА) is a disease leading to joint degeneration, accompanied by constant pain, inflammation, and functional failure of the joints. Although many factors contribute to the development of ОА, the gut microbiome has recently emerged as an important pathogenic factor in ОА initiation and progression. The purpose of the study was to analyze modern literature data regarding the link between the gut microbiome and ОА. Materials and methods. The available data of clinical studies and scientific reviews were analyzed, and modern meta-analyses on the influence of gut microbiota on the development and progression of ОА were evaluated. Results. Gut microbiota is responsible for a number of metabolic, immunological, and structural and neurological functions, potentially elucidating the heterogeneity of OA phenotypes and formation of individual features of the course of the disease. Numerous studies support the hypothesis of the existence of a gut – joint axis and the interaction between gut microbiota and OA-relevant risk factors. The proposed concept begins with intestinal disruption and dysbacteriosis, disruption of microbiota homeostasis, continuous changes in microbial composition and genomic plasticity for optimal adaptation of bacteria to the host environment, accompanied by both adaptive and innate immune responses due to translocation of bacteria and bacterial products into the bloodstream to the joint. This cascade ultimately leads to inflammation in the joint and contributes to the development and progression of OA. Interpretion of the potential mechanisms of OA pathogenesis is essential for the development of new preventive and disease-modifying therapeutic interventions. In addition, gut microbiota is also a potential biomarker related to inflammation and gut dysbiosis to predict the progression of ОА and monitor the effectiveness of therapeutic interventions. Conclusions. In this review, we summarized research data that are supporting the hypothesis of a “joint – gut – microbiota axis” and the interaction between gut microbiota and the OA-relevant factors, including age, gender, metabolism, obesity.

Low-Grade Inflammation in the Pathogenesis of Osteoarthritis: Cellular and Molecular Mechanisms and Strategies for Future Therapeutic Intervention

Osteoarthritis (OA) is a musculoskeletal disease characterized by cartilage degeneration and stiffness, with chronic pain in the affected joint. It has been proposed that OA progression is associated with the development of low-grade inflammation (LGI) in the joint. In support of this principle, LGI is now recognized as the major contributor to the pathogenesis of obesity, aging, and metabolic syndromes, which have been documented as among the most significant risk factors for developing OA. These discoveries have led to a new definition of the disease, and OA has recently been recognized as a low-grade inflammatory disease of the joint. Damage-associated molecular patterns (DAMPs)/alarmin molecules, the major cellular components that facilitate the interplay between cells in the cartilage and synovium, activate various molecular pathways involved in the initiation and maintenance of LGI in the joint, which, in turn, drives OA progression. A better understanding of the pathological mechanisms initiated by LGI in the joint represents a decisive step toward discovering therapeutic strategies for the treatment of OA. Recent findings and discoveries regarding the involvement of LGI mediated by DAMPs in OA pathogenesis are discussed. Modulating communication between cells in the joint to decrease inflammation represents an attractive approach for the treatment of OA.

Boron-containing compounds in Dentistry: a narrative review

Research on the use of boron (B) in the field of oral health has gained momentum in recent years, with various studies on the possibilities of using various B-containing compounds (BCCs). A multitude of applications have been discovered, from cariostatic activity to anti-inflammatory and antifungal activity, paving the way for other new research directions. B is a microelement that is commonly found in the human diet, and present throughout the body, with the highest concentration in the structure of bones, teeth, and gastrointestinal mucus gel layer. Multiple studies have demonstrated that B plays some important roles, especially in bone development and recently has been proposed to have an essential role in the healthy symbiosis. In addition, B has also attracted the interest of researchers, as various studies used BCCs in conventional or modern biomaterials. In this review, we have brought together the information we have found about B updates in the dental field and analyzing its future perspectives and potential for further studies.