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

Dissolving microneedles: A transdermal drug delivery system for the treatment of rheumatoid arthritis

Rheumatoid arthritis (RA) is an autoimmune disorder that impacts around 1% of the global population. Up to 20% of people become disabled within a year, which has a severely negative impact on their health and quality of life. RA has a complicated pathogenic mechanism, which initially affects small joints and progresses to larger ones over time. It can damage the skin, eyes, heart, kidney, and lung. Oral medications, intra-articular injections, and other treatments are being used; nevertheless, they have drawbacks, including low bioavailability, numerous adverse effects, and poor patient compliance. Dissolving microneedles (DMNs) are a safe and painless method for transdermal drug delivery, achieved through their ability to physically penetrate the epidermal barrier. They enable targeted drug delivery, significantly enhancing the bioavailability of medications and improving patient compliance. DMNs are particularly effective in delivering both lipophilic and high molecular weight biomolecules. The superior bioavailability of DMNs is demonstrated by the fact that low-dose DMN administration can achieve up to 25.8 times higher bioavailability compared to oral administration. This paper provides a comprehensive review of recent advancements in the use of DMNs for RA treatment, encompassing various materials (such as hyaluronic acid, chitosan, etc.), fabrication techniques (such as the two-step casting method, photopolymerization), and performance evaluations (including morphology, mechanical properties, skin penetration capability, solubility, and pharmacodynamics). Additionally, a thorough safety assessment has been conducted, revealing that DMNs cause minimal skin irritation and exhibit low cytotoxicity, ensuring their safety for clinical application. DMNs provide a highly effective and promising alternative to oral and injectable drug delivery systems, offering a novel therapeutic approach for RA patients that significantly improves treatment outcomes and enhances their quality of life.

The causal relationship between the human gut microbiota and pyogenic arthritis: a Mendelian randomization study

Background

Recent studies have indicated the role of the gut microbiota in the progression of osteoarticular diseases, however, the causal relationship between the gut microbiota and pyogenic arthritis remains unclear. There is also a lack of theoretical basis for the application of the gut microbiota in the treatment of pyogenic arthritis.

Methods

In our study, we utilized the largest genome-wide association study (GWAS) data from the MiBioGen Consortium involving 13,400 participants and extracted summary statistical data of the microbiota metabolic pathways of 7,738 participants of European descent from the Dutch Microbiome Project (DMP) The data of pyogenic arthritis were derived from the FinnGen R10 database, including 1,086 patients and 147,221 controls. We employed the two-sample Mendelian randomization approach to investigate the causal association between the gut microbiota and pyogenic arthritis. Our methods comprised inverse variance weighting, Mendelian Randomization Egger regression, weighted median, and weighted modal methods. Subsequently, polygenic and heterogeneity analyses were conducted.

Results

At the class level, β-proteobacteria is positively correlated with the risk of pyogenic arthritis. At the order level, Burkholderia is positively associated with the disease. At the genus level, the unclassified genus of Sutterellaceae is positively correlated with the disease, while the unnamed genus of Lachnospiraceae, Rothia, and the unnamed genus of Erysipelotrichaceae are negatively correlated with the disease. In addition, Faecalibacterium and Finegoldia are also negatively correlated with the disease. Sensitivity analysis did not show any abnormal evidence.

Conclusion

This study indicates that β-proteobacteria, Burkholderiales, and the unclassified genus of Sutterellaceae are associated with an increased risk of the disease, while the unnamed genus of Lachnospiraceae, Rothia, the unnamed genus of Erysipelotrichaceae, Faecalibacterium, and Finegoldia are related to a reduced risk. Future studies are needed to elucidate the specific mechanisms by which these specific bacterial groups affect pyogenic arthritis.

Intermittent fasting reduces inflammation and joint damage in a murine model of rheumatoid arthritis: insights from transcriptomic and metagenomic analyses

BACKGROUND

Intermittent fasting (IF) has shown benefits in various pathological conditions. Although its anti-inflammatory potential has been recognized, its effects on the mechanism underlying rheumatoid arthritis (RA) remain insufficiently characterized. This study aimed to investigate the effects of IF in a murine model of RA.

METHODS

Collagen-induced arthritis (CIA) was developed in sixteen male DBA/1 mice, randomly assigned to two groups, with one undergoing IF every other day for four weeks. The effects of IF on joint inflammation and remodeling were evaluated clinically, histologically, and through tomography. Transcriptomic changes were characterized using expression microarrays, validated by RT-qPCR, and confirmed by immunohistochemistry. Additionally, modifications in gut microbiota were assessed through 16 S sequencing.

RESULTS

Mice subjected to IF significantly reduced the incidence and severity of clinical arthritis. Histological and radiographic assessments confirmed a decrease in inflammation and joint damage. Transcriptomic analysis revealed that IF led to the upregulation of 364 genes and the downregulation of 543 genes, with notable reductions in inflammatory signaling pathways associated with RA-related genes, including Cd72, Cd79a, Ifna, Il33, and Bglap 2. Notably, IL33 emerged as a pivotal mediator in the inflammatory processes mitigated by fasting. Key regulators associated with IF effects, such as CEBPA, FOXO1, HIF1A, PPARG, and PPARA, were identified, indicating a complex interplay between metabolic and inflammatory pathways. Furthermore, differential expression of microRNAs and lncRNAs, including miR-15b, miR-103-2, miR-302a, miR-6985, and miR- 5624, was observed. Metagenomic analysis indicated that IF enhanced the abundance and diversity of the gut microbiome, explicitly promoting anti-inflammatory bacterial populations, notably within the genus Ruminococcaceae.

CONCLUSION

Our findings suggest that IF exerts significant anti-inflammatory and immunoregulatory effects in the context of CIA. Given its non-risky nature, further investigation into the potential benefits of IF in patients with RA is warranted.

CLINICAL TRIAL NUMBER

Not applicable.

The interplay between osteoarthritis and osteoporosis: Mechanisms, implications, and treatment considerations - A narrative review

This comprehensive review examines the relationship between osteoarthritis (OA) and osteoporosis (OP), two common disorders in the elderly. OA involves joint cartilage degeneration and pain, while OP leads to fractures due to reduced bone mass. Despite different pathologies, both conditions share risk factors such as age and genetics. Studies reveal mixed results: some show higher bone mineral density (BMD) in OA patients, suggesting an inverse relationship, while others find no significant link. Proposed mechanisms include mechanical loading, bone remodeling, and inflammation. Clinical strategies focus on maintaining bone health in OA and monitoring joint health in OP, with treatments like bisphosphonates and exercise. Understanding these interactions is crucial for developing integrated treatments to improve patient outcomes and quality of life. Further research is needed to clarify these complex mechanisms.

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.

The signature of the gut microbiota associated with psoriatic arthritis revealed by metagenomics

Background

Gut microbiota is involved in the development of psoriatic arthritis (PsA), but until now, there has been a lack of understanding of the PsA host-bacteria interaction.

Objectives

To reveal the labels of gut microbiota in PsA patients and the species and functions related to disease activity.

Design

Observational research (cross-sectional) with an exploratory nature.

Methods

Metagenomics sequencing was used to analyze stool samples from 20 treatment-naïve PsA patients and 10 age-matched healthy individuals. All samples were qualified for subsequent analysis.

Results

Compared with the healthy group, α-diversity was reduced in the PsA group, and β-diversity could distinguish the two groups. Two bacteria with high abundance and correlation with PsA disease activity were identified, Bacteroides sp. 3_1_19 and Blautia AF 14-40. In different functions, K07114 (calcium-activated chloride channel (CaCC) homolog) showed a positive correlation with PsA disease activity (disease activity in psoriatic arthritis, DAPSA) and Tet32 (an antibiotic-resistant gene), and carbohydrate-binding module family 50 was negatively correlated with erythrocyte sedimentation rate. A bacterial co-expression network associated with DAPSA was constructed. The network was centered on the bacteria in the Bacteroides genus, which formed a closely related network and were positively correlated with DAPSA. As another core of the network, K07114 was closely related to multiple bacteria in the Bacteroides genus and is also positively correlated with disease activity.

Conclusion

The network composed of Bacteroides is associated with PsA disease activity, and its therapeutic value needs to be further explored. CaCCs may be a key channel for the interaction between Bacteroides and PsA-host.

Exploring the Role of the Microbiome in Rheumatoid Arthritis-A Critical Review

Rheumatoid arthritis (RA) is a chronic, autoimmune rheumatic disease characterized by synovial joint inflammation with subsequent destruction as well as systemic manifestation, leading to impaired mobility and impaired quality of life. The etiopathogenesis of RA is still unknown, with genetic, epigenetic and environmental factors (incl. tobacco smoking) contributing to disease susceptibility. The link between genetic factors like "shared epitope alleles" and the development of RA is well known. However, why only some carriers have a break in self-tolerance and develop autoimmunity still needs to be clarified. The presence of autoantibodies in patients' serum months to years prior to the onset of clinical manifestations of RA has moved the focus to possible epigenetic factors, including environmental triggers that could contribute to the initiation and perpetuation of the inflammatory reaction in RA. Over the past several years, the role of microorganisms at mucosal sites (i.e., microbiome) has emerged as an essential mediator of inflammation in RA. An increasing number of studies have revealed the microbial role in the immunopathogenesis of autoimmune rheumatic diseases. Interaction between the host immune system and microbiota initiates loss of immunological tolerance and autoimmunity. The alteration in microbiome composition, the so-called dysbiosis, is associated with an increasing number of diseases. Immune dysfunction caused by dysbiosis triggers and sustains chronic inflammation. This review aims to provide a critical summary of the literature findings related to the hypothesis of a reciprocal relation between the microbiome and the immune system. Available data from studies reveal the pivotal role of the microbiome in RA pathogenesis.