Cartilage damage in osteoarthritis and rheumatoid arthritis—two unequal siblings

Transcriptomic analysis reveals distinct molecular signatures and regulatory networks of osteoarthritic chondrocytes versus mesenchymal stem cells during chondrogenesis

BACKGROUND

Recent regenerative studies imply conflicting results on knee osteoarthritic (OA) chondrocytes and mesenchymal stem cells (MSC)-mediated cartilage constructs in terms of compressive properties and tensile strength. This could be attributed to different gene expression patterns between MSC and OA chondrocytes during chondrogenic differentiation. Therefore, we analyzed differentially expressed genes (DEGs) between OA and MSC-derived chondrocytes using bioinformatics tools.

METHODS

We downloaded and analyzed the GSE19664 dataset from the Gene Expression Omnibus to identify DEGs. DAVID was used to perform Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses, while a protein-protein interaction network of DEGs was constructed through the Search Tool for the Retrieval of Interacting Genes (STRING) and identified hub genes by CytoHubba.

RESULTS

A total of 43 DEGs identified (15 downregulated and 28 upregulated) were found to be deregulated between OA and MSC-derived chondrocytes. KEGG analysis revealed the enrichment of complement and coagulation cascades and other pathways among the studied chondrocytes. The pathway enrichment identified top KEGG, gene ontology biological process, molecular function, and cellular component. The hub networks identified the top 5 hub genes involved in chondrogenesis, including CLU, PLAT, CP, TIMP3, and SERPINA1.

CONCLUSIONS

Our results identified significant genes involved in chondrogenesis. These findings provide new avenues for exploring the genetic mechanism underlying cartilage synthesis and novel targets for preclinical intervention and clinical treatment.

Biomechanical study of a modified application of Ilizarov external mini-fixator for metacarpal neck fractures: a comparative analysis

BACKGROUND

Metacarpal neck fractures are common and there are numerous surgical methods available, but each has certain disadvantages and limitations. We modified the conventional Ilizarov external mini-fixator and this study is designed to compare the biomechanical stability of a modified Ilizarov external mini-fixator with conventional fixation methods for metacarpal neck fractures and to provide a basis for its clinical application.

METHODS

Forty fresh porcine metacarpal specimens were used to create metacarpal neck fracture models. The specimens were randomly assigned to four fixation groups (n = 10) as follows: (1) modified Ilizarov external mini-fixator (IEF), (2) retrograde crossed Kirschner wires (KW), (3) antegrade intramedullary Kirschner wires (IK), and (4) locking plate fixation (LP). In the IEF group, the modified design involved crossing two Kirschner wires (K-wires) through the fracture line, with their tails bent twice and connected to the external fixator frame. Biomechanical testing was performed using a modified three-point bending test. Maximum fracture force and bending stiffness were calculated from the force-displacement curves. Kruskal-Wallis test was used to compare statistical differences in maximum fracture force and stiffness among the groups, followed by post hoc pairwise comparisons adjusted with Bonferroni corrections.

RESULTS

The median maximum fracture force values (± interquartile range, IQR) for each group were as follows: IEF 160.3 ± 55.6 N, LP 173.5 ± 42.6 N, KW 91.1 ± 23.1 N, and IK 79.8 ± 37.8 N. The corresponding stiffness values were as follows: IEF 29.5 ± 10.4 N/mm, LP 32.9 ± 10.4 N/mm, KW 17.2 ± 11.3 N/mm, and IK 18.2 ± 13.7 N/mm. The IEF group demonstrated significantly higher maximum fracture force and stiffness than the KW and IK groups; however, no statistically significant differences were observed in the IEF group compared with the LP group.

CONCLUSION

The modified Ilizarov external mini-fixator provided significantly greater biomechanical stability for metacarpal neck fractures than retrograde crossed K-wires and antegrade intramedullary K-wires, achieving comparable performance to the locking plate system. This modified design combines the simplicity and minimally invasive advantages of K-wire fixation with enhanced stability, potentially facilitating early joint mobilization and minimizing the risk of complication.

ER O-glycosylation in synovial fibroblasts drives cartilage degradation

How arthritic synovial fibroblasts (SFs) activate cartilage ECM degradation remains unclear. GALNT enzymes initiate O-glycosylation in the Golgi; when relocated to the ER, their activity stimulates ECM degradation. Here, we show that in human rheumatoid and osteoarthritic synovial SFs, GALNTs are relocated to the ER. In an RA mouse model, GALNTs relocation occurs shortly before arthritis symptoms and abates as the animal recovers. An ER GALNTs inhibitor prevents cartilage ECM degradation in vitro and expression of this chimeric protein in SFs results in the protection of cartilage. One of the ER targets of GALNTs is the resident protein Calnexin, which is exported to the cell surface of arthritic SFs. Calnexin participates in matrix degradation by reducing ECM disulfide bonds. Anti-Calnexin antibodies block ECM degradation and protect animals from RA. In sum, ER O-glycosylation is a key switch in arthritic SFs and glycosylated surface Calnexin could be a therapeutic target.

Exploring the antiquity of rheumatoid arthritis: A case study from medieval Transylvania

OBJECTIVE

To evaluate erosive pathological lesions on a skeleton from medieval Transylvania.

MATERIALS

A skeleton from a Székely archaeological site in Transylvania was examined and radiocarbon dated to Cal 1300 CE - 1415 CE.

METHODS

The skeletal remains were examined macroscopically and with radiographic imaging. A differential diagnosis was conducted following established protocols.

RESULTS

The individual was estimated to be a probable adult female. Periarticular erosive lesions involving multiple synovial joints, particularly on the small joints of the hands and feet, were observed.

CONCLUSIONS

A differential diagnosis identifies lesions characteristic of rheumatoid arthritis dating prior to the mid-15th century.

SIGNIFICANCE

The significance of this diagnosis is great since researchers debate the antiquity and spread of rheumatoid arthritis. Some researchers hypothesize that RA originated in the Americas and spread to Europe after the mid-15th century. However, this study asserts that RA existed in Europe prior to European colonization of the Americas.

LIMITATIONS

Only 30-40 % of the skeletal material was excavated, potentially impacting the differential diagnosis.

SUGGESTIONS FOR FURTHER RESEARCH

This case encourages researchers to explore the presence of RA in other medieval groups within and beyond Transylvania as a means to reconstruct the antiquity and geographical distribution of the condition.

Synovial macrophage diversity and activation of M-CSF signaling in post-traumatic osteoarthritis

Synovium is home to immune and stromal cell types that orchestrate inflammation following a joint injury; in particular, macrophages are central protagonists in this process. We sought to define the cellular and temporal dynamics of the synovial immune niche in a mouse model of post-traumatic osteoarthritis (PTOA), and to identify stromal-immune crosstalk mechanisms that coordinate macrophage function and phenotype. We induced PTOA in mice using a non-invasive tibial compression model of anterior cruciate ligament rupture (ACLR). Single-cell RNA-sequencing and flow cytometry were used to assess immune cell populations in healthy (Sham) and injured (7 and 28 days post-ACLR) synovium. Characterization of synovial macrophage polarization states was performed, alongside computational modeling of macrophage differentiation, as well as implicated transcriptional regulators and stromal-immune communication axes. Immune cell types are broadly represented in healthy synovium, but experience drastic expansion and speciation in PTOA, most notably in the macrophage portion. We identified several polarization states of macrophages in synovium following joint injury, underpinned by distinct transcriptomic signatures, and regulated in part by stromal-derived macrophage colony-stimulating factor signaling. The transcription factors Pu.1, Cebpα, Cebpβ, and Jun were predicted to control differentiation of systemically derived monocytes into pro-inflammatory synovial macrophages. In summary, we defined different synovial macrophage subpopulations present in healthy and injured mouse synovium. Nuanced characterization of the distinct functions, origins, and disease kinetics of macrophage subtypes in PTOA will be critical for targeting these highly versatile cells for therapeutic purposes.

Microphysiological System-Generated Physiological Shear Forces Reduce TNF-α-Mediated Cartilage Damage in a 3D Model of Arthritis

Osteoarthritis (OA) is a leading cause of disability, often resulting from overuse or injury, but inactivity can also contribute to cartilage degeneration. Conventional in vivo models struggle to isolate and study the specific effects of mechanical stress on cartilage health. To address this limitation, a microphysiological system (MPS) is established to examine how varying levels of shear stress impact cartilage homeostasis. The system allows for the cultivation of 3D chondrogenic microconstructs (CMCs) derived from human mesenchymal stromal cells, simulating both physiological and pathophysiological shear stress. Inflammation is induced via TNF-α or activated peripheral blood mononuclear cells to model cartilage damage, enabling the evaluation of therapeutic interventions. The study demonstrates the development of an arthritis-like phenotype and successful restoration of cartilage conditions through a JAK inhibitor under physiological shear stress. Physiological shear stress is identified as a critical factor in maintaining cartilage integrity. This MPS offers a standardized method to study shear stress, replicate cytokine-induced cartilage damage, and simulate key features of arthritis, providing a valuable alternative to animal models.

Matrix-mediated activation of murine fibroblast-like synoviocytes

Fibroblast-like synoviocytes (FLS) are key cells promoting cartilage damage and bone loss in rheumatoid arthritis (RA). They are activated to assume an invasive and migratory phenotype. While mechanisms of FLS activation are unknown, evidence suggests that pre-damaged extracellular matrix (ECM) of the cartilage can trigger FLS activation. Integrin α11β1 might be involved in the activation, as it is increased in RA patients and hTNFtg mice, an RA mouse model. We treated murine chondrocytes with TNFα to produce a damaged, RA-like matrix. Comparison to healthy chondrocyte matrix revealed decreased ECM proteins, e.g. collagens and proteoglycans, increased matrix-degrading proteins and elevated levels of inflammatory cytokines. FLS responded to the damaged chondrocyte matrix with a matrix-remodeling and pro-inflammatory phenotype characterized by a gene signature involved in matrix degradation and increased production of CLL11 and CCL19. Damaged chondrocyte matrix stimulated increased Itga11 expression in FLS, correlating with the increased α11β1 amounts in RA patients. FLS deficient in integrin α11β1 released lower amounts of inflammation-associated cytokines. Our results demonstrate differences in healthy and RA-like chondrocyte ECM and distinctly different responses of wt FLS to damaged versus healthy ECM.

Identification of WDR74 and TNFRSF12A as biomarkers for early osteoarthritis using machine learning and immunohistochemistry

Background

Osteoarthritis (OA) is a chronic joint condition that causes pain, limited mobility, and reduced quality of life, posing a threat to healthy aging. Early detection is crucial for improving prognosis. Recent research has focused on the role of ubiquitination-related genes (URGs) in early OA prediction. This study aims to integrate URG expression data with machine learning (ML) to identify biomarkers that improve diagnosis and prognosis in the early stages of OA.

Methods

OA single-cell RNA sequencing datasets were collected from the GEO database. Single-cell analysis was performed to investigate the composition and relationships of chondrocytes in OA. The potential intercellular communication mechanisms were explored using the CellChat R package. URGs were retrieved from GeneCards, and ubiquitination scores were calculated using the AUCell package. Gene module analysis based on co-expression network analysis was conducted to identify core genes. Additionally, ML analysis was performed to identify core URGs and construct a diagnostic model. We employed XGBoost, a gradient-boosting ML algorithm, to identify core URGs and construct a diagnostic model. The model's performance was evaluated using the area under the curve (AUC) of the receiver operating characteristic (ROC) curve. In addition, we explored the relationship between core URGs and immune processes. The ChEA3 database was utilized to predict the transcription factors regulated by core ubiquitination-related genes. The expression of select URGs was validated using qRT-PCR and immunohistochemistry (IHC).

Results

We identified WDR74 and TNFRSF12A as pivotal ubiquitination-related genes associated with OA, exhibiting considerable differential expression. The diagnostic model constructed with URGs exhibited remarkable accuracy, with area under the curve (AUC) values consistently exceeding 0.9. The expression levels of WDR74 and TNFRSF12A were significantly higher in the IL-1β-induced group in an in vitro qPCR experiment. The IHC validation on human knee joint specimens confirmed the upregulation of WDR74 and TNFRSF12A in OA tissues, corroborating their potential as diagnostic biomarkers.

Conclusions

WDR74 and TNFRSF12A as principal biomarkers highlighted their attractiveness as therapeutic targets. The identification of core biomarkers might facilitate early intervention options, potentially modifying the illness trajectory and enhancing patient outcomes.

Chondroitin sulfate-based microneedles for transdermal delivery of stem cell-derived extracellular vesicles to treat rheumatoid arthritis

For the non-invasive treatment of rheumatoid arthritis (RA), a chondroitin sulfate C (CSC)-based dissolving microneedles (cMN) was prepared to deliver human adipose stem cell-derived extracellular vesicles (hASC-EV) into inflamed joints. Owing to their anti-inflammatory function, the hASC-EV-bearing cMN (EV@cMN) significantly suppressed activated fibroblast-like synoviocytes (aFLS) and M1 macrophages (M1), which are responsible for the progression of RA. In addition, EV@cMN facilitated the chondrogenic differentiation of bone marrow-derived stem cells. In mice with collagen-induced arthritis, EV@cMN efficiently delivered both hASC-EV and CSC to inflamed joints. Interestingly, pro-inflammatory cytokines in the inflamed joints were remarkably downregulated by the synergistic effect of CSC and hASC-EV. Consequently, as judged from the overall clinical score and joint swelling, EV@cMN showed an outstanding therapeutic effect, even comparable to the wild-type mice, without significant adverse effects. Overall, EV@cMN might have therapeutic potential for RA by efficiently delivering CSC and hASC-EV into the inflamed joints in a non-invasive manner.

Femoral and tibial phenotypes of varus alignment in a Southeast Asian arthritic population: a descriptive study

INTRODUCTION

Knowledge of femoral and tibial morphology is important for patient-specific surgery in both joint reconstruction and preservation procedures. Studies evaluating morphological variance in femoral and tibial alignments in Asian populations are scarce. This is the first descriptive study evaluating the femoral and tibial phenotypes of varus alignment in a Southeast Asian population.

METHODS

Long-leg coronal standing radiographs of 2021 limbs were obtained, and the hip-knee-ankle angle, mechanical lateral distal femoral angle, medial proximal tibial angle and joint line convergence angle were measured. Joint line obliquity was calculated, and the knees were classified according to the Coronal Plane Alignment of Knee (CPAK) classification. Descriptive analyses on alignment parameters and demographic data (age, gender, ethnicity and body mass index [BMI]) were performed and entered into a linear regression model.

RESULTS

The highest frequency of limb alignment in the population was found to be CPAK type I (52.71%, n = 1003). Tibial varus was the largest contributor of varus malignment. Of the varus knees (n = 1247), varus deformity was found solely in the tibia (68.60%), solely in the femur (2.07%) and was contributed by both the femur and the tibia (4.97%). In the linear regression model, BMI was found to be a strong determinant for femoral varus (P = 0.004) and joint line incongruence (P < 0.001).

CONCLUSION

The findings of this study will be important to surgeons during planning for joint preservation procedures (such as corrective osteotomies) and joint arthroplasties to restore alignment.

The joint protective function of live- and dead-Lactobacillus plantarum GKD7 on anterior cruciate ligament transection induces osteoarthritis

Osteoarthritis (OA) is a chronic inflammatory disease accompanied by joint pain, bone degradation, and synovial inflammation. Tumor necrosis factor (TNF)-α and interleukin (IL)-1β play key roles in chronic inflammation, and matrix metalloproteinase (MMP)3 is the first enzyme released by chondrocytes and synovial cells that promotes MMPs' degrading cartilage matrix (including collage II and aggrecan) function. Using an anterior cruciate ligament transection (ACLT) rat model, Lactobacillus plantarum GKD7 has shown anti-inflammatory and analgesic properties. The present investigation examined the chondroprotective effects of several dosages and formulas of GKD7 on rats in an ACLT-induced OA model. The findings indicate that oral treatment with both live-GKD7 (GKD7-L) and dead-GKD7 (GKD7-D), along with celecoxib (positive control), all reduce post-ACLT pain and inflammation in OA joints. Subsequently, the immunohistochemical staining results demonstrate that following GKD7-L and GKD7-D treatment, there was a reversal of the degradation of collagen II and aggrecan, as well as a decrease in the expression of IL-1β and TNF-α on the synovial tissue and MMP3 on the cartilage. Accordingly, our findings imply that the treatment of both GKD7-L and GKD7-D has chondroprotective and analgesic effects on the OA rat model, and that celecoxib and GKD7-L at dosages (100 mg/kg) have comparable therapeutic benefits. As a result, we propose that both GKD7-L and GKD7-D are helpful supplements for OA management.

Degrasyn alleviates osteoarthritis by blocking macrophagic pyroptosis via suppressing NLRP3/GSDMD signaling pathway and protecting chondrocytes

Synovitis and cartilage destruction are crucial characteristics of osteoarthritis (OA). Inflammatory cytokines, such as IL-1β, are secreted by synovial macrophages, leading to cartilage destruction. Pyroptosis is a lytic form of programmed cell death, which could be triggered by the NLRP3 inflammasome of macrophages. Pyroptosis promotes the secretion of IL-1β and is supposed as a potential biomarker for OA. However, the function of Pyroptosis and NLRP3 inflammasome and its regulatory mechanism for activation is unclear in OA. In this study, we found that Degrasyn could alleviate the GSDMD-mediated pyroptosis of macrophages and the release of IL-1β, caspase-1, and LDH. Furthermore, it selectively impedes the form of ASC oligomer and speckle to effectively suppress the NLRP3 inflammasome during its assembly phase. Notably, Degrasyn exhibited potential chondroprotective effects in a co-culture system. Additionally, these results also indicate that Degrasyn mitigates synovitis and cartilage damage in a murine model of destabilization of the medial meniscus (DMM)-induced OA. In summary, Degrasyn emerges as a promising pharmaceutical agent for synovitis, paving the way for innovative therapeutic approaches to OA. Our findings underscore the potential of Degrasyn as a viable candidate for OA therapeutics, demonstrating its ability to regulate pyroptosis and NLRP3 inflammasome activation.

Integrin signalling in joint development, homeostasis and osteoarthritis

Integrins are key regulators of cell-matrix interactions during joint development and joint tissue homeostasis, as well as in the development of osteoarthritis (OA). The signalling cascades initiated by the interactions of integrins with a complex network of extracellular matrix (ECM) components and intracellular adaptor proteins orchestrate cellular responses necessary for maintaining joint tissue integrity. Dysregulated integrin signalling, triggered by matrix degradation products such as matrikines, disrupts this delicate balance, tipping the scales towards an environment conducive to OA pathogenesis. The interplay between integrin signalling and growth factor pathways further underscores the multifaceted nature of OA. Moreover, emerging insights into the role of endocytic trafficking in regulating integrin signalling add a new layer of complexity to the understanding of OA development. To harness the therapeutic potential of targeting integrins for mitigation of OA, comprehensive understanding of their molecular mechanisms across joint tissues is imperative. Ultimately, deciphering the complexities of integrin signalling will advance the ability to treat OA and alleviate its global burden.

CircRELL1 promotes osteoarthritis progression by regulating miR-200c-3p

Background

There is a growing body of evidence indicating a potential association between circular RNA and the pathogenesis of human osteoarthritis (OA). Nevertheless, the precise extent of their involvement in OA remains largely unexplored. Hence, the objective of this investigation is to elucidate the function of Circular (Circ) RELL1 in the context of OA.

Methods

24 OA tissue samples and 11 normal tissue samples were collected. The inflammatory OA-like conditions were established by Destabilized Medial Meniscus (DMM) operation in mice and LPS-induced C28/I2 cells. OA severity and articular cartilage degradation were assessed by Safranin-O staining, hematoxylin-eosin (H&E) staining, and International Society for Osteoarthritis Research (OARSI) criteria. CircRELL1, miR-200c-3p, and TCF4 were measured by RT-qPCR and Immunoblot. The cell viability and apoptosis rate were measured by MTT and flow cytometry, respectively. The levels of cytokines interleukin (IL)-1β, IL-6, and TNF-α were determined by ELISA. Apoptosis-associated proteins (cleaved caspase-3, Bax, and Bcl-2) and extracellular matrix (ECM) degradation-associated proteins (MMP13, collagen II, and Aggrecan) were detected by Immunoblot. The interaction between miR-200c-3p and circRELL1 or TCF4 was verified by dual luciferase reporter assay and RIP assay.

Results

CircRELL1 expression was upregulated in OA patients, and the results were consistent in DMM mice and LPS-treated C28/I2 cells. Silencing circRELL1 improved cartilage injury caused by DMM and contributed to a lower OARSI score. Silencing CircRELL1 increased the activity of OA chondrocytes in vivo and in vitro and inhibited cellular inflammatory responses and ECM degradation. In terms of mechanism, circRELL1 functioned by targeting miR-200c-3p, leading to the suppression of inflammatory factor production, cell apoptosis, and ECM degradation, thus inhibiting the progression of OA.

Conclusion

CircRELL1 may promote the progression of OA by regulating the miR-200c-3p.

A comparative analysis of stem cell differentiation on 2D and 3D substrates using Raman microspectroscopy

Chondrogenesis is a complex cellular process that involves the transformation of mesenchymal stem cells (MSCs) into chondrocytes, the specialised cells that form cartilage. In recent years, three-dimensional (3D) culture systems have emerged as a promising approach to studying cell behaviour and development in a more physiologically relevant environment compared to traditional two-dimensional (2D) cell culture. The use of these systems provided insights into the molecular mechanisms that regulate chondrogenesis and has the potential to revolutionise the development of new therapies for cartilage repair and regeneration. This study demonstrates the successful application of Raman microspectroscopy (RMS) as a label-free, non-destructive, and sensitive method to monitor the chondrogenic differentiation of bone marrow-derived rat mesenchymal stem cells (rMSCs) in a collagen type I hydrogel, and explores the potential benefits of 3D hydrogels compared to conventional 2D cell culture environments. rMSCs were cultured on 3D substrates for 3 weeks and their differentiation was monitored by measuring the spectral signatures of their subcellular compartments. Additionally, the evolution of high-density micromass cultures was investigated to provide a comprehensive understanding of the process and complex interactions between cells and their surrounding extracellular matrix. For comparison, rMSCs were induced into chondrogenesis in identical medium conditions for 21 days in monolayer culture. Raman spectra showed that rMSCs cultured in a collagen type I hydrogel are able to undergo a distinct chondrogenic differentiation pathway at a significantly higher rate than the 2D culture cells. 3D cultures expressed stronger and more homogeneous chondrogenesis-associated peaks such as collagens, glycosaminoglycans (GAGs), and aggrecan while manifesting changes in proteins and lipidic content. These results suggest that 3D type I collagen hydrogel substrates are promising for in vitro chondrogenesis studies, and that RMS is a valuable tool for monitoring chondrogenesis in 3D environments.

Artemisia herba-alba: antioxidant capacity and efficacy in preventing chronic arthritis in vivo

Arthritis is a debilitating condition impacting the quality of life for millions worldwide, characterized by pain and inflammation. Understanding the mechanisms of arthritis and developing effective treatments are crucial. This study investigated the hydroethanolic extract of Artemisia herba-alba for its protective potential against arthritis hallmarks, oxidative stress, and lipid peroxidation in vitro. It also assessed its in vivo anti-arthritic activity. The phytochemical analysis identified various compounds within the extract, with high concentrations of polyphenols and flavonoids. These compounds are associated with numerous health benefits, making A. herba-alba a potential source of valuable phytochemicals. A. herba-alba demonstrated a notable effect in body weight loss, paw edema, and arthritic severity. Histopathological examination revealed structural improvements in bone and muscle tissues, emphasizing its therapeutic potential in managing chronic arthritis. Furthermore, while these findings are promising, further studies are necessary to delve deeper into the mechanisms underlying the observed hematological changes and to gain a more comprehensive understanding of the in vivo results. This research sets the stage for continued exploration, ultimately aiming to unlock the full potential of A. herba-alba in addressing chronic arthritis and enhancing the lives of those affected by this condition.

Trochleoplasty Provides Good Outcomes for Recurrent Patellofemoral Dislocations with No Clear Superiority across Different Techniques

Background: Literature is sparse on outcome comparisons between different trochleoplasty techniques in the treatment of patella instability. To date, it is unclear whether there is a technique that offers superior outcomes. This systematic review and meta-analysis aims to compare and evaluate the outcomes of trochleoplasty techniques in the treatment of patellofemoral instability in trochlea dysplasia to establish whether there is an ideal choice of trochleoplasty technique for superior outcomes. Methods: 21 studies involving 880 knees were included. The mean age of the patients was 21.7 years (range 8-49 years). Mean follow-up timeframe of 43.5 months (range 8.8-100 months). Clinical outcomes assessed included rates of recurrence of patellofemoral dislocation, patient satisfaction, Kujala score, International Knee Documentation Committee (IKDC) score, Tegner score, and Lysholm score. Egger's test showed no publication bias across all outcomes assessed. Results: Favourable results were seen across all outcomes assessed and patient satisfaction. Improvements were seen with Kujala, IKDC, and Lysholm scores. Tegner scores showed good return to function. Post-operative dislocation and complication rates were low across the different techniques. Meta-regression for Kujala and IKDC scores showed good outcomes regardless of trochleoplasty technique used (Kujala, p = 0.549, relative risk 492.06; IKDC, p = 0.193, RR 0.001). The exact risk that trochleoplasty poses to the cartilage remains uncertain, as no study had a conservatively managed arm for comparison. Conclusions: Trochleoplasty yielded good outcomes irrespective of technique used with no clear superiority demonstrated in any technique in terms of outcome scores, satisfaction, post-operative dislocation rates or complications.

Chondroitin Sulfate/Hyaluronic Acid-Blended Hydrogels Suppress Chondrocyte Inflammation under Pro-Inflammatory Conditions

Osteoarthritis is characterized by enzymatic breakdown of the articular cartilage via the disruption of chondrocyte homeostasis, ultimately resulting in the destruction of the articular surface. Decades of research have highlighted the importance of inflammation in osteoarthritis progression, with inflammatory cytokines shifting resident chondrocytes into a pro-catabolic state. Inflammation can result in poor outcomes for cells implanted for cartilage regeneration. Therefore, a method to promote the growth of new cartilage and protect the implanted cells from the pro-inflammatory cytokines found in the joint space is required. In this study, we fabricate two gel types: polymer network hydrogels composed of chondroitin sulfate and hyaluronic acid, glycosaminoglycans (GAGs) known for their anti-inflammatory and prochondrogenic activity, and interpenetrating networks of GAGs and collagen I. Compared to a collagen-only hydrogel, which does not provide an anti-inflammatory stimulus, chondrocytes in GAG hydrogels result in reduced production of pro-inflammatory cytokines and enzymes as well as preservation of collagen II and aggrecan expression. Overall, GAG-based hydrogels have the potential to promote cartilage regeneration under pro-inflammatory conditions. Further, the data have implications for the use of GAGs to generally support tissue engineering in pro-inflammatory environments.

In situ cell condensation-based cartilage tissue engineering via immediately implantable high-density stem cell core and rapidly degradable shell microgels

Formation of chondromimetic human mesenchymal stem cells (hMSCs) condensations typically required in vitro culture in defined environments. In addition, extended in vitro culture in differentiation media over several weeks is usually necessary prior to implantation, which is costly, time consuming and delays clinical treatment. Here, this study reports on immediately implantable core/shell microgels with a high-density hMSC-laden core and rapidly degradable hydrogel shell. The hMSCs in the core formed cell condensates within 12 hours and the oxidized and methacrylated alginate (OMA) hydrogel shells were completely degraded within 3 days, enabling spontaneous and precipitous fusion of adjacent condensed aggregates. By delivering transforming growth factor-β1 (TGF-β1) within the core, the fused condensates were chondrogenically differentiated and formed cartilage microtissues. Importantly, these hMSC-laden core/shell microgels, fabricated without any in vitro culture, were subcutaneously implanted into mice and shown to form cartilage tissue via cellular condensations in the core after 3 weeks. This innovative approach to form cell condensations in situ without in vitro culture that can fuse together with each other and with host tissue and be matured into new tissue with incorporated bioactive signals, allows for immediate implantation and may be a platform strategy for cartilage regeneration and other tissue engineering applications.

Pterostilbene Protects against Osteoarthritis through NLRP3 Inflammasome Inactivation and Improves Gut Microbiota as Evidenced by In Vivo and In Vitro Studies

Osteoarthritis (OA) is a persistent inflammatory disease, and long-term clinical treatment often leads to side effects. In this study, we evaluated pterostilbene (PT), a natural anti-inflammatory substance, for its protective effects and safety during prolonged use on OA. Results showed that PT alleviated the loss of chondrocytes and widened the narrow joint space in an octacalcium phosphate (OCP)-induced OA mouse model (n = 3). In vitro experiments demonstrate that PT reduced NLRP3 inflammation activation (relative protein expression: C: 1 ± 0.09, lipopolysaccharide (LPS): 1.14 ± 0.07, PT: 0.91 ± 0.07, LPS + PT: 0.68 ± 0.04) and the release of inflammatory cytokines through NF-κB signaling inactivation (relative protein expression: C: 1 ± 0.03, LPS: 3.49 ± 0.02, PT: 0.66 ± 0.08, LPS + PT: 2.78 ± 0.05), ultimately preventing cartilage catabolism. Interestingly, PT also altered gut microbiota by reducing inflammation-associated flora and increasing the abundance of healthy bacteria in OA groups. Collectively, these results suggest that the PT can be considered as a protective strategy for OA.

Nerve growth factor receptor limits inflammation to promote remodeling and repair of osteoarthritic joints

Osteoarthritis (OA) is a painful, incurable disease affecting over 500 million people. Recent clinical trials of the nerve growth factor (NGF) inhibitors in OA patients have suggested adverse effects of NGF inhibition on joint structure. Here we report that nerve growth factor receptor (NGFR) is upregulated in skeletal cells during OA and plays an essential role in the remodeling and repair of osteoarthritic joints. Specifically, NGFR is expressed in osteochondral cells but not in skeletal progenitor cells and induced by TNFα to attenuate NF-κB activation, maintaining proper BMP-SMAD1 signaling and suppressing RANKL expression in mice. NGFR deficiency hyper-activates NF-κB in murine osteoarthritic joints, which impairs bone formation and enhances bone resorption as exemplified by a reduction in subchondral bone and osteophytes. In human OA cartilage, NGFR is also negatively associated with NF-κB activation. Together, this study suggests a role of NGFR in limiting inflammation for repair of diseased skeletal tissues.

A review of advanced hydrogels for cartilage tissue engineering

With the increase in weight and age of the population, the consumption of tobacco, inappropriate foods, and the reduction of sports activities in recent years, bone and joint diseases such as osteoarthritis (OA) have become more common in the world. From the past until now, various treatment strategies (e.g., microfracture treatment, Autologous Chondrocyte Implantation (ACI), and Mosaicplasty) have been investigated and studied for the prevention and treatment of this disease. However, these methods face problems such as being invasive, not fully repairing the tissue, and damaging the surrounding tissues. Tissue engineering, including cartilage tissue engineering, is one of the minimally invasive, innovative, and effective methods for the treatment and regeneration of damaged cartilage, which has attracted the attention of scientists in the fields of medicine and biomaterials engineering in the past several years. Hydrogels of different types with diverse properties have become desirable candidates for engineering and treating cartilage tissue. They can cover most of the shortcomings of other treatment methods and cause the least secondary damage to the patient. Besides using hydrogels as an ideal strategy, new drug delivery and treatment methods, such as targeted drug delivery and treatment through mechanical signaling, have been studied as interesting strategies. In this study, we review and discuss various types of hydrogels, biomaterials used for hydrogel manufacturing, cartilage-targeting drug delivery, and mechanosignaling as modern strategies for cartilage treatment.

Exploring the mechanism of Celastrol in the treatment of rheumatoid arthritis based on systems pharmacology and multi-omics

To explore the molecular network mechanism of Celastrol in the treatment of rheumatoid arthritis (RA) based on a novel strategy (integrated systems pharmacology, proteomics, transcriptomics and single-cell transcriptomics). Firstly, the potential targets of Celastrol and RA genes were predicted through the database, and the Celastrol-RA targets were obtained by taking the intersection. Then, transcriptomic data and proteomic data of Celastrol treatment of RA were collected. Subsequently, Celastrol-RA targets, differentially expressed genes, and differentially expressed proteins were imported into Metascape for enrichment analysis, and related networks were constructed. Finally, the core targets of Celastrol-RA targets, differentially expressed genes, and differentially expressed proteins were mapped to synoviocytes of RA mice to find potential cell populations for Celastrol therapy. A total of 195 Celastrol-RA targets, 2068 differential genes, 294 differential proteins were obtained. The results of enrichment analysis showed that these targets, genes and proteins were mainly related to extracellular matrix organization, TGF-β signaling pathway, etc. The results of single cell sequencing showed that the main clusters of these targets, genes, and proteins could be mapped to RA synovial cells. For example, Mmp9 was mainly distributed in Hematopoietic cells, especially in Ptprn+fibroblast. The results of molecular docking also suggested that Celastrol could stably combine with molecules predicted by network pharmacology. In conclusion, this study used systems pharmacology, transcriptomics, proteomics, single-cell transcriptomics to reveal that Celastrol may regulate the PI3K/AKT signaling pathway by regulating key targets such as TNF and IL6, and then play an immune regulatory role.

Mechanism of lysine oxidase-like 1 promoting synovial inflammation mediating rheumatoid arthritis development

Rheumatoid arthritis (RA) is a chronic inflammatory joint disease that causes great distress to patients and society. Early diagnosis is the key to the successful treatment of RA. The basement membrane, one of the oldest tissue structures, is localized under the epithelium. Its complex composition and rich biological functions have made it a focus of research in recent years, while basement membrane-associated genetic variants are involved in most human disease processes. The aim of this study is to find new diagnostic biomarkers for RA and explore their role and possible mechanism in rheumatoid arthritis. The GSE12021, GSE55235 and GSE55457 datasets were downloaded from the GEO database. Their fraction associated with basement membrane genes was analyzed and differentially expressed genes between the disease and normal groups were explored. We identified two basement membrane-associated genes, lysine oxidase-like 1 (LOXL1) and discoid peptide receptor 2 (DDR2). Focusing on the more interesting LOXL1, we found that LOXL1 expression was significantly elevated in the synovium of patients with rheumatoid arthritis, and LOXL1 mRNA and protein levels were elevated in tumor necrosis factor α-stimulated human synovial sarcoma cells (SW982). And LOXL1 knockdown inhibited tumor necrosis factor α-induced inhibition in SW982 cells expression of inducible nitric oxide synthase (INOS), cyclooxygenase-2 (COX2), and interleukin-6 (IL-6). Interestingly, knockdown of LOXL1 inhibited the phosphorylation of PI3K and AKT. In summary, LOXL1 may become a novel diagnostic gene for RA, and knockdown of LoxL1 may inhibit synovial inflammation by affecting PI3K/AKT pathway.

Biomimetic Injectable Hydrogel Based on Methacrylate-Modified Silk Fibroin Embedded with Kartogenin for Superficial Cartilage Regeneration

The weak regeneration ability of chondrocytes is one of the main reasons that limit the therapeutic effect of clinical cartilage injury. Injectable hydrogels are potential scaffolds for cartilage tissue engineering with advantages such as minimally invasive surgery, porous structure, and drug sustained-release ability. At present, many biomaterials have been developed for the repair of deep cartilage defects. However, cartilage injury often begins on the surface, which requires us to propose a treatment strategy suitable for superficial cartilage injury repair. In this study, we fabricated a biomimetic injectable hydrogel based on methacrylate-modified silk fibroin (SilMA) embedded with kartogenin (KGN). The SilMA/KGN hydrogels have good biohistocompatibility and the ability to promote cartilage differentiation. In addition, SEM results show that it has a porous structure conducive to cell adhesion and proliferation. Most importantly, it has demonstrated remarkable superficial cartilage repair ability in vivo, showing potential in cartilage tissue engineering.

Inhibitory effects of Acanthopanax sessiliflorus Harms extract on the etiology of rheumatoid arthritis in a collagen-induced arthritis mouse model

BACKGROUND

The biological function of Acanthopanax sessiliflorus Harm (ASH) has been investigated on various diseases; however, the effects of ASH on arthritis have not been investigated so far. This study investigates the effects of ASH on rheumatoid arthritis (RA).

METHODS

Supercritical carbon dioxide (CO2) was used for ASH extract preparation, and its primary components, pimaric and kaurenoic acids, were identified using gas chromatography-mass spectrometer (GC-MS). Collagenase-induced arthritis (CIA) was used as the RA model, and primary cultures of articular chondrocytes were used to examine the inhibitory effects of ASH extract on arthritis in three synovial joints: ankle, sole, and knee.

RESULTS

Pimaric and kaurenoic acids attenuated pro-inflammatory cytokine-mediated increase in the catabolic factors and retrieved pro-inflammatory cytokine-mediated decrease in related anabolic factors in vitro; however, they did not affect pro-inflammatory cytokine (IL-1β, TNF-α, and IL-6)-mediated cytotoxicity. ASH effectively inhibited cartilage degradation in the knee, ankle, and toe in the CIA model and decreased pannus development in the knee. Immunohistochemistry demonstrated that ASH mostly inhibited the IL-6-mediated matrix metalloproteinase. Gene Ontology and pathway studies bridge major gaps in the literature and provide insights into the pathophysiology and in-depth mechanisms of RA-like joint degeneration.

CONCLUSIONS

To the best of our knowledge, this is the first study to conduct extensive research on the efficacy of ASH extract in inhibiting the pathogenesis of RA. However, additional animal models and clinical studies are required to validate this hypothesis.

Nerve Growth Factor Receptor Limits Inflammation to Promote Remodeling and Repair of Osteoarthritic Joints

Osteoarthritis (OA) is a painful, incurable disease affecting over 500 million people. The need for relieving OA pain is paramount but inadequately addressed, partly due to limited understandings of how pain signaling regulates non-neural tissues. Here we report that nerve growth factor receptor (NGFR) is upregulated in skeletal cells during OA and plays an essential role in the remodeling and repair of osteoarthritic joints. Specifically, NGFR is expressed in osteochondral cells but not in skeletal progenitor cells and induced by TNFα to attenuate NF-κB activation, maintaining proper BMP-SMAD1 signaling and suppressing RANKL expression. NGFR deficiency hyper-activates NF-κB in murine osteoarthritic joints, which impairs bone formation and enhances bone resorption as exemplified by a reduction in subchondral bone and osteophytes. In human OA cartilage, NGFR is also negatively associated with NF-κB activation. Together, this study uncovers a role of NGFR in limiting inflammation for repair of diseased skeletal tissues.

The effects of physiological and injurious hydrostatic pressure on murine ex vivo articular and growth plate cartilage explants: an RNAseq study

Introduction

Chondrocytes are continuously exposed to loads placed upon them. Physiological loads are pivotal to the maintenance of articular cartilage health, while abnormal loads contribute to pathological joint degradation. Similarly, the growth plate cartilage is subject to various loads during growth and development. Due to the high-water content of cartilage, hydrostatic pressure is considered one of the main biomechanical influencers on chondrocytes and has been shown to play an important role in the mechano-regulation of cartilage.

Methods

Herein, we conducted RNAseq analysis of ex vivo hip cap (articular), and metatarsal (growth plate) cartilage cultures subjected to physiological (5 MPa) and injurious (50 MPa) hydrostatic pressure, using the Illumina platform (n = 4 replicates).

Results

Several hundreds of genes were shown to be differentially modulated by hydrostatic pressure, with the majority of these changes evidenced in hip cap cartilage cultures (375 significantly upregulated and 322 downregulated in 5 MPa versus control; 1022 upregulated and 724 downregulated in 50 MPa versus control). Conversely, fewer genes were differentially affected by hydrostatic pressure in the metatarsal cultures (5 significantly upregulated and 23 downregulated in 5 MPa versus control; 7 significantly upregulated and 19 downregulated in 50 MPa versus control). Using Gene Ontology annotations for Biological Processes, in the hip cap data we identified a number of pathways that were modulated by both physiological and injurious hydrostatic pressure. Pathways upregulated in response to 50 MPa versus control, included those involved in the generation of precursor metabolites and cellular respiration. Biological processes that were downregulated in this tissue included ossification, connective tissue development, and chondrocyte differentiation.

Discussion

Collectively our data highlights the divergent chondrocyte phenotypes in articular and growth plate cartilage. Further, we show that the magnitude of hydrostatic pressure application has distinct effects on gene expression and biological processes in hip cap cartilage explants. Finally, we identified differential expression of a number of genes that have previously been identified as osteoarthritis risk genes, including Ctsk, and Chadl. Together these data may provide potential genetic targets for future investigations in osteoarthritis research and novel therapeutics.

Cationic mesoporous silica nanoparticles alleviate osteoarthritis by targeting multiple inflammatory mediators

Osteoarthritis (OA) is a common and complex inflammatory disorder that is frequently compounded by cartilage degradation, synovial inflammation, and osteophyte formation. Damaged chondrocytes release multiple danger mediators that exacerbate synovial inflammation and accelerate the progression to OA. Conventional treatments targeting only a single mediator of OA have failed to achieve a strong therapeutic effect. Addressing the crucial role of multiple danger mediators in OA progression, we prepared polyethylenimine (PEI)-functionalized diselenide-bridged mesoporous silica nanoparticles (MSN-PEI) with cell-free DNA (cfDNA)-binding and anti-oxidative properties. In models of surgery-induced and collagenase-induced arthritis, we showed that these cationic nanoparticles attenuated cartilage degradation and provided strong chondroprotection against joint damage. Mechanistically, multiple target blockades alleviated oxidative stress and dampened cfDNA-induced inflammation by suppressing the M1 polarization of macrophages. This study suggests a beneficial direction for targeting multiple danger mediators in the treatment of intractable arthritis.

Combining single-cell RNA sequencing and population-based studies reveals hand osteoarthritis-associated chondrocyte subpopulations and pathways

Hand osteoarthritis is a common heterogeneous joint disorder with unclear molecular mechanisms and no disease-modifying drugs. In this study, we performed single-cell RNA sequencing analysis to compare the cellular composition and subpopulation-specific gene expression between cartilage with macroscopically confirmed osteoarthritis (n = 5) and cartilage without osteoarthritis (n = 5) from the interphalangeal joints of five donors. Of 105 142 cells, we identified 13 subpopulations, including a novel subpopulation with inflammation-modulating potential annotated as inflammatory chondrocytes. Fibrocartilage chondrocytes exhibited extensive alteration of gene expression patterns in osteoarthritic cartilage compared with nonosteoarthritic cartilage. Both inflammatory chondrocytes and fibrocartilage chondrocytes showed a trend toward increased numbers in osteoarthritic cartilage. In these two subpopulations from osteoarthritic cartilage, the ferroptosis pathway was enriched, and expression of iron overload-related genes, e.g., FTH1, was elevated. To verify these findings, we conducted a Mendelian randomization study using UK Biobank and a population-based cross-sectional study using data collected from Xiangya Osteoarthritis Study. Genetic predisposition toward higher expression of FTH1 mRNA significantly increased the risk of hand osteoarthritis (odds ratio = 1.07, 95% confidence interval: 1.02-1.11) among participants (n = 332 668) in UK Biobank. High levels of serum ferritin (encoded by FTH1), a biomarker of body iron overload, were significantly associated with a high prevalence of hand osteoarthritis among participants (n = 1 241) of Xiangya Osteoarthritis Study (P-for-trend = 0.037). In conclusion, our findings indicate that inflammatory and fibrocartilage chondrocytes are key subpopulations and that ferroptosis may be a key pathway in hand osteoarthritis, providing new insights into the pathophysiology and potential therapeutic targets of hand osteoarthritis.

Redox-active endosomes mediate α5β1 integrin signaling and promote chondrocyte matrix metalloproteinase production in osteoarthritis

Mechanical cues sensed by integrins induce cells to produce proteases to remodel the extracellular matrix. Excessive protease production occurs in many degenerative diseases, including osteoarthritis, in which articular cartilage degradation is associated with the genesis of matrix protein fragments that can activate integrins. We investigated the mechanisms by which integrin signals may promote protease production in response to matrix changes in osteoarthritis. Using a fragment of the matrix protein fibronectin (FN) to activate the α5β1 integrin in primary human chondrocytes, we found that endocytosis of the integrin and FN fragment complex drove the production of the matrix metalloproteinase MMP-13. Activation of α5β1 by the FN fragment, but not by intact FN, was accompanied by reactive oxygen species (ROS) production initially at the cell surface, then in early endosomes. These ROS-producing endosomes (called redoxosomes) contained the integrin-FN fragment complex, the ROS-producing enzyme NADPH oxidase 2 (NOX2), and SRC, a redox-regulated kinase that promotes MMP-13 production. In contrast, intact FN was endocytosed and trafficked to recycling endosomes without inducing ROS production. Articular cartilage from patients with osteoarthritis showed increased amounts of SRC and the NOX2 complex component p67phox. Furthermore, we observed enhanced localization of SRC and p67phox at early endosomes, suggesting that redoxosomes could transmit and sustain integrin signaling in response to matrix damage. This signaling mechanism not only amplifies the production of matrix-degrading proteases but also establishes a self-perpetuating cycle that contributes to the ongoing degradation of cartilage matrix in osteoarthritis.

Synovial macrophage diversity and activation of M-CSF signaling in post-traumatic osteoarthritis

Objective

Synovium is home to immune and stromal cell types that orchestrate inflammation following a joint injury; in particular, macrophages are central protagonists in this process. We sought to define the cellular and temporal dynamics of the synovial immune niche in a mouse model of post-traumatic osteoarthritis (PTOA), and to identify stromal-immune crosstalk mechanisms that coordinate macrophage function and phenotype.

Design

We induced PTOA in mice using a non-invasive tibial compression model of anterior cruciate ligament rupture (ACLR). Single cell RNA-seq and flow cytometry were used to assess immune cell populations in healthy (Sham) and injured (7d and 28d post-ACLR) synovium. Characterization of synovial macrophage polarization states was performed, alongside computational modeling of macrophage differentiation, as well as implicated transcriptional regulators and stromal-immune communication axes.

Results

Immune cell types are broadly represented in healthy synovium, but experience drastic expansion and speciation in PTOA, most notably in the macrophage portion. We identified several polarization states of macrophages in synovium following joint injury, underpinned by distinct transcriptomic signatures, and regulated in part by stromal-derived macrophage colony-stimulating factor signaling. The transcription factors Pu.1, Cebpα, Cebpβ, and Jun were predicted to control differentiation of systemically derived monocytes into pro-inflammatory synovial macrophages.

Conclusions

We defined different synovial macrophage subpopulations present in healthy and injured mouse synovium. Nuanced characterization of the distinct functions, origins, and disease kinetics of macrophage subtypes in PTOA will be critical for targeting these highly versatile cells for therapeutic purposes.

Augmenting mesenchymal stem cell therapy for osteoarthritis via inflammatory priming: a comparative study on mesenchymal stem cells derived from various perinatal tissue sources

Background: Osteoarthritis (OA), a degenerative disease prevalent among the elderly, poses significant challenges due to its high incidence and disability rates. Regrettably, there exists a lack of effective regenerative therapies for the irreversible degradation of cartilage in OA. Mesenchymal stem cells (MSCs), known for their robust differentiation and immune regulatory capabilities, have emerged as promising candidates for OA treatment. MSCs sourced from perinatal tissues offer the dual advantage of convenience in extraction and ethical non-controversy. However, the heterogeneous nature of MSCs derived from different perinatal tissue sources gives rise to varying therapeutic indications. Moreover, the immune response of MSCs may be modulated under the influence of inflammatory factors. Methods: In this study, we isolated mesenchymal stem cells from distinct parts of human perinatal tissue: umbilical cord-derived MSCs (UC-MSCs), fetal placenta-derived MSCs (FP-MSCs), and umbilical cord placental junction-derived MSCs (CPJ-MSCs). These cells were cultured in vitro and subjected to a 24-hour treatment with the inflammatory mediator Interleukin-1β (IL-1β). Subsequently, the MSCs were evaluated for changes in proliferation, migration, and regulatory capabilities. To assess the comparative anti-injury potential of MSCs from different sources, primary articular chondrocytes (ACs) were exposed to H2O2-induced injury and co-cultured with IL-1β-primed MSCs. Changes in the proliferation, migration, and regulatory abilities of ACs resembling those observed in OA were examined. Results: Following IL-1β treatment, all three types of MSCs displayed decreased rates of proliferation and migration. Notably, their chondrogenic differentiation capacities exhibited an enhancement. Additionally, diverse MSCs exhibited a degree of efficacy in restoring damaged ACs in vitro. Among these, CPJ-MSCs demonstrated superior potential in promoting cartilage cell proliferation, while FP-MSCs displayed notable anti-inflammatory effects. Conclusion: Our findings underscore the substantial capacity of primed FP-MSCs and CPJ-MSCs to alleviate the injury in OA-like ACs. Consequently, this study advocates for the prospective use of preconditioning strategies involving FP-MSCs and CPJ-MSCs in forthcoming OA therapies.

Imaging in inflammatory arthritis: progress towards precision medicine

Imaging techniques such as ultrasonography and MRI have gained ground in the diagnosis and management of inflammatory arthritis, as these imaging modalities allow a sensitive assessment of musculoskeletal inflammation and damage. However, these techniques cannot discriminate between disease subsets and are currently unable to deliver an accurate prediction of disease progression and therapeutic response in individual patients. This major shortcoming of today's technology hinders a targeted and personalized patient management approach. Technological advances in the areas of high-resolution imaging (for example, high-resolution peripheral quantitative computed tomography and ultra-high field MRI), functional and molecular-based imaging (such as chemical exchange saturation transfer MRI, positron emission tomography, fluorescence optical imaging, optoacoustic imaging and contrast-enhanced ultrasonography) and artificial intelligence-based data analysis could help to tackle these challenges. These new imaging approaches offer detailed anatomical delineation and an in vivo and non-invasive evaluation of the immunometabolic status of inflammatory reactions, thereby facilitating an in-depth characterization of inflammation. By means of these developments, the aim of earlier diagnosis, enhanced monitoring and, ultimately, a personalized treatment strategy looms closer.

High-Sucrose Diet Accelerates Arthritis Progression in a Collagen-Induced Rheumatoid Arthritis Model

SCOPE

High dietary sugar and sweeteners are suspected to cause the development of rheumatoid arthritis (RA) symptoms through the induction of proinflammatory cytokine release. However, the mechanisms by which increased dietary sugar affects RA etiology are not yet fully understood. The study uses a mouse model of collagen-induced RA (CIA) to investigate the relationship between excessive sugar consumption and RA risk.

METHODS AND RESULTS

RA-associated pathological features are assessed in the nonimmunized (NI) control group, the CIA-positive control group, and the CIA + high-sucrose diet (CIA+HS, 63% calories from sucrose) group. Compared with the CIA group, the CIA+HS group shows a greater increase in paw thickness and clinical scores, as well as, a higher degree of pannus formation and inflammation in the knee, ankle, and sole tissues. Moreover, the infiltration of immune cells is increased in the CIA+HS group. Although the expression of hepatic lipogenic genes, is not altered, that of toll-like receptor (TLR4) and IL-1β is considerably elevated in the CIA+HS group.

CONCLUSIONS

These findings suggest that excessive sucrose consumption causes hepatic fibrosis and inflammation, contributing to the pathophysiology of RA.

The Mechanisms and Efficacy of Photobiomodulation Therapy for Arthritis: A Comprehensive Review

Rheumatoid arthritis (RA) and osteoarthritis (OA) have a significant impact on the quality of life of patients around the world, causing significant pain and disability. Furthermore, the drugs used to treat these conditions frequently have side effects that add to the patient's burden. Photobiomodulation (PBM) has emerged as a promising treatment approach in recent years. PBM effectively reduces inflammation by utilizing near-infrared light emitted by lasers or LEDs. In contrast to photothermal effects, PBM causes a photobiological response in cells, which regulates their functional response to light and reduces inflammation. PBM's anti-inflammatory properties and beneficial effects in arthritis treatment have been reported in numerous studies, including animal experiments and clinical trials. PBM's effectiveness in arthritis treatment has been extensively researched in arthritis-specific cells. Despite the positive results of PBM treatment, questions about specific parameters such as wavelength, dose, power density, irradiation time, and treatment site remain. The goal of this comprehensive review is to systematically summarize the mechanisms of PBM in arthritis treatment, the development of animal arthritis models, and the anti-inflammatory and joint function recovery effects seen in these models. The review also goes over the evaluation methods used in clinical trials. Overall, this review provides valuable insights for researchers investigating PBM treatment for arthritis, providing important references for parameters, model techniques, and evaluation methods in future studies.

Development of Therapeutic Agent for Osteoarthritis via Inhibition of KIAA1199 Activity: Effect of Ipriflavone In Vivo

This study aimed to clarify the effects of ipriflavone, which effectively reduces KIAA1199 activity, on osteoarthritis (OA) development and progression in an in vivo OA mouse model. The OA model mice were divided into the ipriflavone (200 mg/kg/day) group and the control group. OA onset and progression were evaluated with the Mankin score, and KIAA1199 expression and hyaluronan (HA) accumulation were analyzed by immunostaining. The molecular weight of HA in the cartilage tissue and serum HA concentration were analyzed by chromatography and competitive HA enzyme-linked immunoassay. The effects of ipriflavone on the bovine cartilage explant culture under the influence of IL-1β were also investigated. In the ipriflavone group, Safranin-O stainability was well-preserved, resulting in significant reduction of the Mankin score (p = 0.027). KIAA1199 staining positivity decreased and HA stainability was preserved in the ipriflavone group. The serum HA concentration decreased, and the molecular weight of HA in the cartilage tissue increased in the ipriflavone group. The results of the cartilage explant culture indicated that ipriflavone could reduce GAG losses and increase the molecular weight of HA. Thus, ipriflavone may have an inhibitory effect on OA development/progression. Ipriflavone could be a therapeutic drug for OA by targeting KIAA1199 activity.

Accelerometer-derived physical activity analysis of elderly osteoarthritis patients

BACKGROUND

Because disability in Osteoarthritis (OA) may change physical activity (PA), which might affect the disease progression, it is important to measure a patient's daily PA to study the relationship between a patient's PA and disease progression.

OBJECTIVE

The objective of the present study was to investigate the relationship between PA and patients with OA and people without OA using data from the Korea National Health and Nutrition Examination Survey (KNHANES).

METHODS

Demographic study was conducted to obtain data of comorbidities of participants. PA was compared between the group with OA (OA group) and the group without OA (non-OA group). In addition, PAs of OA patients with comorbidities and those without comorbidities were compared. The cut-off of moderate to vigorous physical activity (MVPA) was obtained through a receiver operating characteristic (ROC) curve.

RESULTS

In the demographic study, there were significantly more educated participants in the OA group (p < .001). Actigraph data showed a significant decrease in MVPA (p < .001) but a significant increase in light activity (p = .002) in the OA group. In addition, the OA group showed significantly lower light PA but significantly higher MVPA in ≥10 min bout length. OA patients with comorbidities showed higher MVPA than OA patients without comorbidities (p = .044). The cut-off point of MVPA was 7.071 min/day when ROC curve was conducted.

CONCLUSIONS

The present study suggests that patients with OA and low activity need a certain level of physical activity and a cut-off point for MVPA is presented which accounts for comorbidities in OA patients.

The Dual-Responsive Interaction of Particulated Hyaline Cartilage and Plasma Rich in Growth Factors (PRGF) in the Repair of Cartilage Defects: An In Vitro Study

The treatment of chondral and osteochondral defects is challenging. These types of lesions are painful and progress to osteoarthritis over time. Tissue engineering offers tools to address this unmet medical need. The use of an autologous cartilage construct consisting of hyaline cartilage chips embedded in plasma rich in growth factors (PRGF) has been proposed as a therapeutic alternative. The purpose of this study was to dig into the potential mechanisms behind the in vitro remodelling process that might explain the clinical success of this technique and facilitate its optimisation. Chondrocyte viability and cellular behaviour over eight weeks of in vitro culture, type II collagen synthesis, the dual delivery of growth factors by hyaline cartilage and PRGF matrix, and the ultrastructure of the construct and its remodelling were characterised. The main finding of this research is that the cartilage fragments embedded in the three-dimensional PRGF scaffold contain viable chondrocytes that are able to migrate into the fibrin network, proliferate and synthesise extracellular matrix after the second week of in vitro culture. The characterization of this three-dimensional matrix is key to unravelling the molecular kinetics responsible for its efficacy.

Targeting macrophagic PIM-1 alleviates osteoarthritis by inhibiting NLRP3 inflammasome activation via suppressing mitochondrial ROS/Cl- efflux signaling pathway

BACKGROUND

Osteoarthritis (OA), in which macrophage-driven synovitis is considered closely related to cartilage destruction and could occur at any stage, is an inflammatory arthritis. However, there are no effective targets to cure the progression of OA. The NOD-, LRR-,and pyrin domain-containing protein 3 (NLRP3) inflammasome in synovial macrophages participates in the pathological inflammatory process and treatment strategies targeting it are considered to be an effective approach for OA. PIM-1 kinase, as a downstream effector of many cytokine signaling pathways, plays a pro-inflammatory role in inflammatory disease.

METHODS

In this study, we evaluated the expression of the PIM-1 and the infiltration of synovial macrophages in the human OA synovium. The effects and mechanism of PIM-1 were investigated in mice and human macrophages stimulated by lipopolysaccharide (LPS) and different agonists such as nigericin, ATP, Monosodium urate (MSU), and Aluminum salt (Alum). The protective effects on chondrocytes were assessed by a modified co-culture system induced by macrophage condition medium (CM). The therapeutic effect in vivo was confirmed by the medial meniscus (DMM)-induced OA in mice.

RESULTS

The expression of PIM-1 was increased in the human OA synovium which was accompanied by the infiltration of synovial macrophages. In vitro experiments, suppression of PIM-1 by SMI-4a, a specific inhibitor, rapidly inhibited the NLRP3 inflammasome activation in mice and human macrophages and gasdermin-D (GSDME)-mediated pyroptosis. Furthermore, PIM-1 inhibition specifically blocked the apoptosis-associated speck-like protein containing a CARD (ASC) oligomerization in the assembly stage. Mechanistically, PIM-1 inhibition alleviated the mitochondrial reactive oxygen species (ROS)/chloride intracellular channel proteins (CLICs)-dependent Cl- efflux signaling pathway, which eventually resulted in the blockade of the ASC oligomerization and NLRP3 inflammasome activation. Furthermore, PIM-1 suppression showed chondroprotective effects in the modified co-culture system. Finally, SMI-4a significantly suppressed the expression of PIM-1 in the synovium and reduced the synovitis scores and the Osteoarthritis Research Society International (OARSI) score in the DMM-induced OA model.

CONCLUSIONS

Therefore, PIM-1 represented a new class of promising targets as a treatment of OA to target these mechanisms in macrophages and widened the road to therapeutic strategies for OA.

Regenerative Effect of Mesenchymal Stem Cell on Cartilage Damage in a Porcine Model

Osteoarthritis (OA) is a major public and animal health challenge with significant economic consequences. Cartilage degradation plays a critical role in the initiation and progression of degenerative joint diseases, such as OA. Mesenchymal stem cells (MSCs) have become increasingly popular in the field of cartilage regeneration due to their promising results. The objective of this preclinical study was to evaluate the regenerative effects of mesenchymal stem cells (MSCs) in the repair of knee cartilage defects using a porcine model. Seven healthy LYD breed white pigs, aged 9-10 weeks and weighing approximately 20 ± 3 kg, were used in the experimental protocol. Full-thickness defects measuring 8 mm in diameter and 5 mm in depth were induced in the lateral femoral condyle of the posterior limbs in both knee joints using a sterile puncture technique while the knee was maximally flexed. Following a 1-week induction phase, the pig treatment groups received a 0.3 million/kg MSC transplant into the damaged knee region, while the placebo group received a control solution as a treatment. Magnetic resonance imaging (MRI), computerized tomography (CT), visual macroscopic examination, histological analysis, and cytokine concentration analysis were used to assess cartilage regeneration. The findings revealed that human adipose-derived mesenchymal stem cells (hADSCs) were more effective in repairing cartilage than pig umbilical cord-derived mesenchymal stem cells (pUCMSCs). These results suggest that MSC-based treatments hold promise as a treatment option for cartilage repair, which aid in the treatment of OA. However, further studies with larger sample sizes and longer follow-up periods are required to fully demonstrate the safety and efficacy of these therapies in both animals and humans.

Cartilage-Related Collagens in Osteoarthritis and Rheumatoid Arthritis: From Pathogenesis to Therapeutics

Collagens serve essential mechanical functions throughout the body, particularly in the connective tissues. In articular cartilage, collagens provide most of the biomechanical properties of the extracellular matrix essential for its function. Collagen plays a very important role in maintaining the mechanical properties of articular cartilage and the stability of the ECM. Noteworthily, many pathogenic factors in the course of osteoarthritis and rheumatoid arthritis, such as mechanical injury, inflammation, and senescence, are involved in the irreversible degradation of collagen, leading to the progressive destruction of cartilage. The degradation of collagen can generate new biochemical markers with the ability to monitor disease progression and facilitate drug development. In addition, collagen can also be used as a biomaterial with excellent properties such as low immunogenicity, biodegradability, biocompatibility, and hydrophilicity. This review not only provides a systematic description of collagen and analyzes the structural characteristics of articular cartilage and the mechanisms of cartilage damage in disease states but also provides a detailed characterization of the biomarkers of collagen production and the role of collagen in cartilage repair, providing ideas and techniques for clinical diagnosis and treatment.

Integrin αVβ3 Signaling in the Progression of Osteoarthritis Induced by Excessive Mechanical Stress

Osteoarthritis (OA) is believed to be linked with cartilage degeneration, subchondral bone sclerosis, and synovial inflammation that lead to joint failure, and yet treatment that can effectively reverse the pathological process of the disease still not exists. Recent evidence suggests excessive mechanical stress (eMS) as an essential role in the pathogenesis of OA. Increased levels of integrin αVβ3 have been detected in osteoarthritic cartilage and were previously implicated in OA pathogenesis. However, the role of integrin αVβ3 in the process of eMS-induced OA remains unclear. Here, histologic and proteomic analyses of osteoarthritic cartilage in a rat destabilization of the medial meniscus model demonstrated elevated expression of integrin αVβ3 as well as more serious cartilage degeneration in the medial weight-bearing area. Furthermore, results of in vitro study demonstrated that eMS led to a significant increase of integrin αVβ3 expression and phosphorylation of downstream signaling molecules such as FAK and ERK, as well as upregulated expressions of inflammatory and degradative mediators. In addition, we found that inhibition of integrin αVβ3 could alleviate chondrocyte inflammation triggered by eMS both in vivo and in vitro. Our findings suggest a central role for upregulation of integrin αVβ3 signaling in OA pathogenesis and demonstrate that activation of integrin αVβ3 signaling in cartilage contributes to inflammation and joint destruction in eMS-induced OA. Taken together, our data presented here provide a possibility for targeting integrin αVβ3 signaling pathway as a disease-modifying therapy.

New Insights into the Role of Synovial Fibroblasts Leading to Joint Destruction in Rheumatoid Arthritis

Rheumatoid arthritis (RA), one of the most common autoimmune diseases, is characterized by multiple-joint synovitis with subsequent destruction of bone and cartilage. The excessive autoimmune responses cause an imbalance in bone metabolism, promoting bone resorption and inhibiting bone formation. Preliminary studies have revealed that receptor activator of NF-κB ligand (RANKL)-mediated osteoclast induction is an important component of bone destruction in RA. Synovial fibroblasts are the crucial producers of RANKL in the RA synovium; novel analytical techniques, primarily, single-cell RNA sequencing, have confirmed that synovial fibroblasts include heterogeneous subsets of both pro-inflammatory and tissue-destructive cell types. The heterogeneity of immune cells in the RA synovium and the interaction of synovial fibroblasts with immune cells have recently received considerable attention. The current review focused on the latest findings regarding the crosstalk between synovial fibroblasts and immune cells, and the pivotal role played by synovial fibroblasts in joint destruction in RA.

SOXC Transcription Factors as Diagnostic Biomarkers and Therapeutic Targets for Arthritis

Osteoarthritis (OA) and rheumatoid arthritis (RA) are two common disorders that disrupt the quality of life of millions of people. These two chronic diseases cause damage to the joint cartilage and surrounding tissues of more than 220 million people worldwide. Sex-determining region Y-related (SRY) high-mobility group (HMG) box C, SOXC, is a superfamily of transcription factors that have been recently shown to be involved in various physiological and pathological processes. These include embryonic development, cell differentiation, fate determination, and autoimmune diseases, as well as carcinogenesis and tumor progression. The SOXC superfamily includes SOX4, SOX11, and SOX12, all have a similar DNA-binding domain, i.e., HMG. Herein, we summarize the current knowledge about the role of SOXC transcription factors during arthritis progression and their potential utilization as diagnostic biomarkers and therapeutic targets. The involved mechanistic processes and signaling molecules are discussed. SOX12 appears to have no role in arthritis, however SOX11 is dysregulated and promotes arthritic progression according to some studies but supports joint maintenance and protects cartilage and bone cells according to others. On the other hand, SOX4 upregulation during OA and RA was documented in almost all studies including preclinical and clinical models. Molecular details have indicated that SOX4 can autoregulate its own expression besides regulating the expression of SOX11, a characteristic associated with the transcription factors that protects their abundance and activity. From analyzing the currently available data, SOX4 seems to be a potential diagnostic biomarker and therapeutic target of arthritis.

Inhibition of fibroblast activation protein ameliorates cartilage matrix degradation and osteoarthritis progression

Fibroblast activation protein (Fap) is a serine protease that degrades denatured type I collagen, α2-antiplasmin and FGF21. Fap is highly expressed in bone marrow stromal cells and functions as an osteogenic suppressor and can be inhibited by the bone growth factor Osteolectin (Oln). Fap is also expressed in synovial fibroblasts and positively correlated with the severity of rheumatoid arthritis (RA). However, whether Fap plays a critical role in osteoarthritis (OA) remains poorly understood. Here, we found that Fap is significantly elevated in osteoarthritic synovium, while the genetic deletion or pharmacological inhibition of Fap significantly ameliorated posttraumatic OA in mice. Mechanistically, we found that Fap degrades denatured type II collagen (Col II) and Mmp13-cleaved native Col II. Intra-articular injection of rFap significantly accelerated Col II degradation and OA progression. In contrast, Oln is expressed in the superficial layer of articular cartilage and is significantly downregulated in OA. Genetic deletion of Oln significantly exacerbated OA progression, which was partially rescued by Fap deletion or inhibition. Intra-articular injection of rOln significantly ameliorated OA progression. Taken together, these findings identify Fap as a critical pathogenic factor in OA that could be targeted by both synthetic and endogenous inhibitors to ameliorate articular cartilage degradation.

Arthritis and Duchenne muscular dystrophy: the role of chondroitin sulfate and its associated proteoglycans in disease pathology and as a diagnostic marker

Chondroitin sulfate (CS) is a ubiquitous glycosaminoglycan covalently attached to the core proteins of cell surface, extracellular, and intracellular proteoglycans. The multistep and highly regulated biosynthesis of chondroitin sulfate and its degradation products give rise to a diverse species of molecules with functional regulatory properties in biological systems. This review will elucidate and expand on the most recent advances in understanding the role of chondroitin sulfate and its associate proteoglycans, in arthritis and Duchenne muscular dystrophy (DMD), two different and discrete pathologies. Highlighting not only the biodiverse nature of this family of molecules but also the utilization of CS proteoglycans, CS, and its catabolic fragments as biomarkers and potential therapeutic targets for disease pathologies.

The forgotten key players in rheumatoid arthritis: IL-8 and IL-17 - Unmet needs and therapeutic perspectives

Despite the relevant advances in our understanding of the pathogenetic mechanisms regulating inflammation in rheumatoid arthritis (RA) and the development of effective therapeutics, to date, there is still a proportion of patients with RA who do not respond to treatment and end up progressing toward the development of joint damage, extra-articular complications, and disability. This is mainly due to the inter-individual heterogeneity of the molecular and cellular taxonomy of the synovial membrane, which represents the target tissue of RA inflammation. Tumor necrosis factor alpha (TNFα) and interleukin-6 (IL-6) are crucial key players in RA pathogenesis fueling the inflammatory cascade, as supported by experimental evidence derived from in vivo animal models and the effectiveness of biologic-Disease Modifying Anti-Rheumatic Drugs (b-DMARDs) in patients with RA. However, additional inflammatory soluble mediators such as IL-8 and IL-17 exert their pathogenetic actions promoting the detrimental activation of immune and stromal cells in RA synovial membrane, tendons, and extra-articular sites, as well as blood vessels and lungs, causing extra-articular complications, which might be excluded by the action of anti-TNFα and anti-IL6R targeted therapies. In this narrative review, we will discuss the role of IL-8 and IL-17 in promoting inflammation in multiple biological compartments (i.e., synovial membrane, blood vessels, and lung, respectively) in animal models of arthritis and patients with RA and how their selective targeting could improve the management of treatment resistance in patients.

The Diagnostic and Prognostic Value of Synovial Fluid Analysis in Joint Diseases

Liquid biopsy is an emergent test method for the diagnosis and prognosis in the clinic. Joint fluid, also known as synovial fluid, contains a variety of bioactive constituents that can be selectively detected and further evaluated in a convenient fashion. Therefore, synovial fluid analysis functions as a specific form of liquid biopsy and plays a vital role in numerous joint diseases. In spite of the component analysis of aspirated synovial fluid beingconsidered as the gold standard for diagnosis of joint infections, biopsy of joint fluid benefits the initial diagnosis and long-term prognosis of degenerative, inflammatory, autoimmune, traumatic, congenital, and even neoplastic joint diseases. The convenience and accuracy for disease evaluation are significantly elevated as a result of the combination of synovial fluid analysis and other novel clinical technologies. In this review, we shed light on the latent role of synovial fluid in the diagnosis and prognosis of articular diseases and proposed future prospects for relevant research in this field.

Interactions between NSAIDs, opioids and the gut microbiota - Future perspectives in the management of inflammation and pain

The composition of intestinal microbiota is influenced by a number of factors, including medications, which may have a substantial impact on host physiology. Nonsteroidal anti-inflammatory drugs (NSAIDs) and opioid analgesics are among those widely used medications that have been shown to alter microbiota composition in both animals and humans. Although much effort has been devoted to identify microbiota signatures associated with these medications, much less is known about the underlying mechanisms. Mucosal inflammation, changes in intestinal motility, luminal pH and bile acid metabolism, or direct drug-induced inhibitory effect on bacterial growth are all potential contributors to NSAID- and opioid-induced dysbiosis, however, only a few studies have addressed directly these issues. In addition, there is a notable overlap between the microbiota signatures of these drugs and certain diseases in which they are used, such as spondyloarthritis (SpA), rheumatoid arthritis (RA) and neuropathic pain associated with type 2 diabetes (T2D). The aims of the present review are threefold. First, we aim to provide a comprehensive up-to-date summary on the bacterial alterations caused by NSAIDs and opioids. Second, we critically review the available data on the possible underlying mechanisms of dysbiosis. Third, we review the current knowledge on gut dysbiosis associated with SpA, RA and neuropathic pain in T2D, and highlight the similarities between them and those caused by NSAIDs and opioids. We posit that drug-induced dysbiosis may contribute to the persistence of these diseases, and may potentially limit the therapeutic effect of these medications by long-term use. In this context, we will review the available literature data on the effect of probiotic supplementation and fecal microbiota transplantation on the therapeutic efficacy of NSAIDs and opioids in these diseases.