Knee Osteoarthritis Cartilage Research Articles

Increased Rab1a accelerates osteoarthritis by inhibiting autophagy via activation of the mTORC1-S6K pathway

IntroductionCartilage degradation is a critical alteration in the progression of osteoarthritis (OA) due to the disorder of chondrocyte metabolic homeostasis. Autophagy plays an important role in maintaining intracellular homeostasis. Recent investigations have increasingly underscored the importance of autophagy in modulating the pathological mechanisms underlying OA. Ras-related protein Rab-1a (Rab1a) has been illustrated to regulate autophagy in many diseases but not in OA. ObjectivesThis study aims to elucidate whether Rab1a could regulate the development of OA through modulation of chondrocyte autophagy and apoptosis. MethodsProteomic sequencing, Western blotting, and immunohistochemistry were applied to detect the expression level of Rab1a in vitro and in vivo. Gene Ontology terms and Kyoto Encyclopedia of Genes and Genomes pathways were rigorously identified. The effects of Rab1a and the interaction between Rab1a, mTORC1, autophagy and apoptosis were explored by qPCR, Western blotting, and immunofluorescence. An experimental mouse OA model was also performed to confirm the role of Rab1a in OA pathogenesis in vivo. Histological analysis was employed to demonstrate cartilage damage. ResultsRab1a expression was significantly upregulated in inflamed chondrocytes and knee OA cartilage. Inhibition of Rab1a partially attenuated the degradation of the extracellular matrix and cell apoptosis both in vitro and in vivo, whereas overexpression of Rab1a intensified cartilage matrix degradation and cellular apoptosis. Additionally, elevated Rab1a levels were observed to suppress autophagy and activate the mTORC1-S6K signaling pathway, thereby aggravating OA pathogenesis. ConclusionThe augmentation of Rab1a expression impairs autophagy and promotes apoptosis through the activation of the mTORC1-S6K signaling pathway, further exacerbating OA pathogenesis. This finding suggests that Rab1a serves as a promising and innovative therapeutic target for the prevention and treatment of OA.

Degradomics defines proteolysis information flow from human knee osteoarthritis cartilage to matched synovial fluid and the contributions of secreted proteases ADAMTS5, MMP13 and CMA1 to articular cartilage breakdown

ObjectivesProteolytic cartilage extracellular matrix breakdown is a major mechanism of articular cartilage loss in osteoarthritis (OA) pathogenesis. We sought to determine the overlap of proteolytic peptides in matched knee OA cartilage and synovial fluid on a proteome-wide scale to increase the prospective biomarker repertoire and to attribute proteolytic cleavages to specific secreted proteases. DesignMatched human knee OA cartilage and synovial fluid (n=5) were analyzed by N-terminomics using Terminal Amine Isotopic Labeling of Substrates (TAILS), comprising labeling and enrichment of protein N-termini, high-resolution mass spectrometry and positional peptide mapping. Donor non-OA articular cartilage was digested with CMA1, MMP13 or ADAMTS5, and TAILS was used to identify cleavage sites, which were matched against cartilage and synovial fluid degradomes. ResultsOf over 20,000 cleaved peptides in the combined OA cartilage and synovial fluid degradomes, 677 peptides, originating from 153 proteins, were present in all cartilage and synovial fluid samples. CMA1, MMP13 and ADAMTS5 digestion of cartilage identified numerous cleavage sites for each protease and distinct cleavage site preferences. Peptides resulting from the activities of these proteases were detected in OA cartilage and synovial fluid. ConclusionsProteolytic fragments from both cartilage and circulating proteins are detectable by synovial fluid degradomics. CMA1, MMP13 and ADAMTS5 activity profiles in cartilage are distinct from each other and the previously determined HtrA1 profile. This work expands the proteolytic biomarker space for OA investigation, suggests that multiple, diverse proteases contribute to cartilage destruction, and demonstrates that their specific contributions can each be defined by multiple biomarkers.

Effect of moxibustion on plasma amino acid metabolism in rats with knee osteoarthritis.

To observe the effect of moxibustion at "Zusanli "(ST36) on the plasma amino acid metabolism in rats with knee osteoarthritis (KOA), and to explore the amino acid metabolism mechanism of moxibustion in repairing cartilage injury in KOA. A total of 30 SD rats were randomly divided into normal, model and moxibustion groups, with 10 rats in each group. Rats in the model and moxibustion groups were injected with the mixture of L-cysteine and papain into bilateral knee joint cavity to make the KOA model. The moxibustion group received moxibustion at bilateral ST36 for 30 min, once daily for 30 days. At the end of the experiment, the swelling degree of knee joint was calculated, the mechanical pain threshold was measured by the Von Frey filament, the cartilage tissue injury was observed by HE staining, the matrix metalloproteinase-13 (MMP-13) content in the synovial tissue was detected by enzyme-linked immunosorbent assay (ELISA), and the differential amino acid metabolites in plasma were detected and screened by liquid chromatography-mass spectrometry (LC-MS). Compared with the normal group, the model group showed irregular cartilage surface, decreased number of chondrocytes, uneven distribution, and local clusters of chondrocytes；the contour of the tide line was blurred. The degree of joint swelling in the model group was higher than that in the normal group (P<0.01), the mechanical pain threshold was lower (P<0.01), and the content of MMP-13 in synovial tissue was higher (P<0.01). The contents of proline and tryptophan in the model group were down-regulated (P<0.01, P<0.05). Compared with the model group, the cartilage tissue damage and knee joint swelling were decreased(P<0.05), mechanical pain threshold was increased(P<0.05), MMP-13 content in synovial tissue and levels of glutamate and histidine expression were decreased (P<0.01, P<0.05). Moxibustion at ST36 significantly alleviated arthritis-related swelling and pain in KOA model rats, attenuated cartilage damage, and regulated levels of certain plasma amino acid metabolites. Moxibustion may regulate KOA cartilage synthesis and degradation through amino acid metabolic pathways such as proline, tryptophan, glutamate and histidine, exerting anti-inflammatory, analgesic, and protection of cartilage injury effects.

Curcumenol regulates Histone H3K27me3 demethylases KDM6B affecting Succinic acid metabolism to alleviate cartilage degeneration in knee osteoarthritis

BackgroundCartilage metabolism dysregulation is a crucial driver in knee osteoarthritis (KOA). Modulating the homeostasis can mitigate the cartilage degeneration in KOA. Curcumenol, derived from traditional Chinese medicine Curcuma Longa L., has demonstrated potential in enhancing chondrocyte proliferation and reducing apoptosis. However, the specific mechanism of Curcumenol in treating KOA remains unclear. This study aimed to demonstrate the molecular mechanism of Curcumenol in treating KOA based on the transcriptomics and metabolomics, and both in vivo and in vitro experimental validations. Materials and methodsIn this study, a destabilization medial meniscus (DMM)-induced KOA mouse model was established. And the mice were intraperitoneally injected with Curcumenol at 4 and 8 mg/kg concentrations. The effects of Curcumenol on KOA cartilage and subchondral was evaluated using micro-CT, histopathology, and immunohistochemistry (IHC). In vitro, OA chondrocytes were induced with 10 μg/mL lipopolysaccharide (LPS) and treated with Curcumenol to evaluate the proliferation, apoptosis, and extracellular matrix (ECM) metabolism through CCK8 assay, flow cytometry, and chondrocyte staining. Furthermore, transcriptomics and metabolomics were utilized to identify differentially expressed genes (DEGs) and metabolites. Finally, integrating multi-omics analysis, virtual molecular docking (VMD), and molecular dynamics simulation (MDS), IHC, immunofluorescence (IF), PCR, and Western blot (WB) validation were conducted to elucidate the mechanism by which Curcumenol ameliorates KOA cartilage degeneration. ResultsCurcumenol ameliorated cartilage destruction and subchondral bone loss in KOA mice, promoted cartilage repair, upregulated the expression of COL2 while downregulated MMP3, and improved ECM synthesis metabolism. Additionally, Curcumenol also alleviated the damage of LPS on the proliferation activity and suppressed apoptosis, promoted ECM synthesis. Transcriptomic analysis combined with weighted gene co-expression network analysis (WGCNA) identified a significant downregulation of 19 key genes in KOA. Metabolomic profiling showed that Curcumenol downregulates the expression of d-Alanyl-d-alanine, 17a-Estradiol, Glutathione, and Succinic acid, while upregulating Sterculic acid and Azelaic acid. The integrated multi-omics analysis suggested that Curcumenol targeted KDM6B to regulate downstream protein H3K27me3 expression, which inhibited methylation at the histone H3K27, consequently reducing Succinic acid levels and improving KOA cartilage metabolism homeostasis. Finally, both in vivo and in vitro findings indicated that Curcumenol upregulated KDM6B, suppressed H3K27me3 expression, and stimulated collagen II expression and ECM synthesis, thus maintaining cartilage metabolism homeostasis and alleviating KOA cartilage degeneration. ConclusionCurcumenol promotes cartilage repair and ameliorates cartilage degeneration in KOA by upregulating KDM6B expression, thereby reducing H3K27 methylation and downregulating Succinic Acid, restoring metabolic stability and ECM synthesis.

TBK1 pharmacological inhibition mitigates osteoarthritis through attenuating inflammation and cellular senescence in chondrocytes

ObjectivesTANK-binding kinase 1 (TBK1) is pivotal in autoimmune and inflammatory diseases, yet its role in osteoarthritis (OA) remains elusive. This study sought to elucidate the effect of the TBK1 inhibitor BX795 on OA and to delineate the underlying mechanism by which it mitigates OA. MethodsInterleukin-1 Beta (IL-1β) was utilized to simulate inflammatory responses and extracellular matrix degradation in vitro. In vivo, OA was induced in 8-week-old mice through destabilization of the medial meniscus surgery. The impact of BX795 on OA was evaluated using histological analysis, X-ray, micro-CT, and the von Frey test. Additionally, Western blot, RT-qPCR, and immunofluorescence assays were conducted to investigate the underlying mechanisms of BX795. ResultsPhosphorylated TBK1 (P-TBK1) levels were found to be elevated in OA knee cartilage of both human and mice. Furthermore, intra-articular injection of BX795 ameliorated cartilage degeneration and alleviated OA-associated pain. BX795 also counteracted the suppression of anabolic processes and the augmentation of catabolic activity, inflammation, and senescence observed in the OA mice. In vitro studies revealed that BX795 reduced P-TBK1 levels and reversed the effects of anabolism inhibition, catabolism promotion, and senescence induction triggered by IL-1β. Mechanistically, BX795 inhibited the IL-1β-induced activation of the cGAS–STING and TLR3–TRIF signaling pathways in chondrocytes. ConclusionsPharmacological inhibition of TBK1 with BX795 protects articular cartilage by inhibiting the activation of the cGAS–STING and TLR3–TRIF signaling pathways. This action attenuates inflammatory responses and cellular senescence, positioning BX795 as a promising therapeutic candidate for OA treatment. The translational potential of this articleThis study furnishes experimental evidence and offers a potential mechanistic explanation supporting the efficacy of BX795 as a promising candidate for OA treatment.

Gaining Insight into Updated MR Imaging for Quantitative Assessment of Cartilage Injury in Knee Osteoarthritis.

Knee Osteoarthritis (KOA) entails progressive cartilage degradation, reviewed via MRI for morphology, biochemical composition, and microtissue alterations, discussing clinical advantages, limitations, and research applicability. Compositional MRI, like T2/T2* mapping, T1rho mapping, gagCEST, dGEMRIC, sodium imaging, diffusion-weighted imaging, and diffusion-tensor imaging, provide insights into cartilage injury in KOA. These methods quantitatively measure collagen, glycosaminoglycans, and water content, revealing important information about biochemical compositional and microstructural alterations. Innovative techniques like hybrid multi-dimensional MRI and diffusion-relaxation correlation spectrum imaging show potential in depicting initial cartilage changes at a sub-voxel level. Integration of automated image analysis tools addressed limitations in manual cartilage segmentation, ensuring robust and reproducible assessments of KOA cartilage. Compositional MRI techniques reveal microstructural changes in cartilage. Multi-dimensional MR imaging assesses biochemical alterations in KOA-afflicted cartilage, aiding early degeneration identification. Integrating artificial intelligence enhances cartilage analysis, optimal diagnostic accuracy for early KOA detection and monitoring.

Interactions of cumulative load with biomarkers of cartilage turnover predict knee cartilage change over 2 years: data from the osteoarthritis initiative.

The purpose was to investigate relationships of cumulative load and cartilage turnover biomarkers with 2-year changes in cartilage in knee osteoarthritis. From participants with Kellgren-Lawrence (KL) grades of 1 to 3, cartilage thickness and transverse relaxation time (T2) were computed from 24-month (baseline) and 48-month magnetic resonance images. Cumulative load was the interaction term of the Physical Activity Scale for the Elderly (PASE) and body mass index (BMI). Serum cartilage oligomeric matrix protein (COMP) and the nitrated form of type II collagen (Coll2-1 NO2) were collected at baseline. Multiple regressions (adjusted for baseline age, KL grade, cartilage measures, pain, comorbidity) evaluated the relationships of cumulative load and biomarkers with 2-year changes. In 406 participants (63.7 (8.7) years), interactions of biomarkers with cumulative load weakly predicted 2-year cartilage changes: (i) COMP × cumulative load explained medial tibia thickness change (R2 increased 0.062 to 0.087, p < 0.001); (ii) Coll2-1 NO2 × cumulative load explained central medial femoral T2 change (R2 increased 0.177 to 0.210, p < 0.001); and (iii) Coll2-1 NO2 × cumulative load explained lateral tibia T2 change (R2 increased 0.166 to 0.188, p < 0.001). Moderate COMP or Coll2-1 NO2 at baseline appeared protective. High COMP or Coll2-1 NO2, particularly with high BMI and low PASE, associated with worsening cartilage. Moderate serum concentrations of cartilage turnover biomarkers, at high and low physical activity, associated with maintained cartilage outcomes over 2 years. In conclusion, high concentrations of cartilage turnover biomarkers, particularly with high BMI and low physical activity, associated with knee cartilage thinning and increasing T2 over 2 years. Key Points • Higher quality cartilage may be better able to tolerate a larger cumulative load than poor quality cartilage. • Among participants enrolled in the Osteoarthritis Initiative Biomarkers Consortium Project, a representation of cumulative load exposure and its interaction with cartilage turnover biomarkers were weakly related with 2-year change in knee cartilage. • These findings suggest that cartilage turnover is a factor that modifies the relationship between loading exposure and cartilage loss in knee OA.

Hsa_circ_0007482 Promotes Proliferation and Differentiation of Chondrocytes in Knee Osteoarthritis.

Knee osteoarthritis (KOA) is a complex degenerative joint disease and a major cause of joint dysfunction. This study aimed to explore the function of hsa_circ_0007482 on inflammation, proliferation, differentiation, and apoptosis in KOA. Real-time quantitative polymerase chain reaction (PCR) was performed to detect the expression of circ_0007482, inflammatory factors, and differentiation-related molecules in KOA chondrocytes and interleukin (IL)-1β-stimulated chondrocytes. The correlation between the circ_0007482 expression and inflammatory factors was analyzed by the Pearson method. KOA cell model was established using IL-1β for 24 hours. The proliferation activity of chondrocytes was evaluated by CCK-8 assay, and cell apoptosis rate was assessed by flow cytometry. The downstream miRNA of circ_0007482 was validated using dual-luciferase reporter assay. The circ_0007482 expression was elevated in both KOA cartilage tissues and IL-1β-treated chondrocytes and positively correlated with inflammatory factors expression. In comparison to the control group, IL-1β treatment diminished chondrocyte proliferation abilities and increased cell apoptosis and inflammatory factors IL-6, IL-8, and tumor necrosis factor (TNF)-α mRNA expression. Inhibition of circ_0007482 partially improved IL-1β-induced inflammatory reaction. Circ_0007482 could negatively regulate the expression of miR-558. Interfering of circ_0007482 might partially promote cell proliferation and differentiation, while inhibit cell apoptosis to improve joint injury by regulating miR-558 in IL-1β-treated chondrocyte cell model.

Electro-acupuncture modulated miR-214 expression to prevent chondrocyte apoptosis and reduce pain by targeting BAX and TRPV4 in osteoarthritis rats.

Osteoarthritis (OA) is a highly prevalent joint disorder characterized by progressive degeneration of articular cartilage, subchondral bone remodeling, osteophyte formation, synovial inflammation, and meniscal damage. Although the etiology of OA is multifactorial, pro-inflammatory processes appear to play a key role in disease pathogenesis. Previous studies indicate that electroacupuncture (EA) exerts chondroprotective, anti-inflammatory, and analgesic effects in preclinical models of OA, but the mechanisms underlying these potential therapeutic benefits remain incompletely defined. This study aimed to investigate the effects of EA on OA development in a rat model, as well as to explore associated molecular mechanisms modulated by EA treatment. Forty rats were divided into OA, EA, antagomiR-214, and control groups. Following intra-articular injection of monosodium iodoacetate to induce OA, EA and antagomiR-214 groups received daily EA stimulation at acupoints around the knee joint for 21 days. Functional pain behaviors and chondrocyte apoptosis were assessed as outcome measures. The expression of microRNA-214 (miR-214) and its downstream targets involved in apoptosis and nociception, BAX and TRPV4, were examined. Results demonstrated that EA treatment upregulated miR-214 expression in OA knee cartilage. By suppressing pro-apoptotic BAX and pro-nociceptive TRPV4, this EA-induced miR-214 upregulation ameliorated articular pain and prevented chondrocyte apoptosis. These findings suggested that miR-214 plays a key role mediating EA's therapeutic effects in OA pathophysiology, and represents a promising OA treatment target for modulation by acupuncture.

Analysis of Molecular Changes and Features in Rat Knee Osteoarthritis Cartilage: Progress From Cellular Changes to Structural Damage

Objective Although knee osteoarthritis (KOA) is a common disease, there is a lack of specific prevention and early treatment methods. Hence, this study aimed to examine the molecular changes occurring at different stages of KOA to elucidate the dynamic nature of the disease. Design Using a low-force compression model and analyzing RNA sequencing data, we identified molecular changes in the transcriptome of knee joint cartilage, including gene expression and molecular pathways, between the cellular changes and structural damage stages of KOA progression. In addition, we validated hub genes using an external dataset. Results Gene set enrichment analysis (GSEA) identified the following pathways to be associated with KOA: “B-cell receptor signaling pathway,” “cytokine-cytokine receptor interaction,” and “hematopoietic cell lineage.” Expression analysis revealed 585 differentially expressed genes, with 579 downregulated and 6 upregulated genes. Enrichment and clustering analyses revealed that the main molecular clusters were involved in cell cycle regulation and immune responses. Furthermore, the hub genes Csf1r, Cxcr4, Cxcl12, and Ptprc were related to immune responses. Conclusions Our study provides insights into the dynamic nature of early-stage KOA and offers valuable information to support the development of effective intervention strategies to prevent the irreversible damage associated with KOA, thereby addressing a major clinical challenge.

Chonggu Granules Improve Cartilage Matrix Metabolism in Knee Osteoarthritis via the miR-148a-3p/Wnt/β-Catenin Pathway.

This study aims to explore the effect and underlying mechanism of Chonggu Granules (CGG) in knee osteoarthritis (KOA) in rats. A papain-induced KOA model was established in rats. The pathological alterations of extracellular matrix in rat cartilage tissues were observed through hematoxylin and eosin (H&E) staining, followed by Mankin score for quantitative scoring. The ultrastructure of cartilage extracellular matrix was examined under a transmission electron microscopy (TEM). ELISA was used to measure the levels of IL-6, TNF-α, and IL-1β in rat serum. Immunofluorescence was performed for assessing the levels of MMP-3, MMP-13, and Col2al in rat cartilage. Western blot was used to identify the protein expressions of wnt1, GSK-3β, β-catenin, and Aggrecan in rat cartilage. The mRNA relative expressions of miR-148a-3p, wnt1, β-catenin, and GSK-3β in rat cartilage were detected by RT-PCR. Luciferase reporter gene was used to detect the target genes of miR-148a-3p. CGG significantly improved articular cartilage tissue and extracellular matrix metabolism compared to the model group as indicated by H&E, Mankin score, and TEM data. Moreover, low, medium, and high doses of CGG reduced the levels of IL-6, TNF-α, IL-1β, MMP-3, and MMP-13 in serum to varying degrees but increased the levels of Col2al and Aggrecan. Mechanistically, CGG targeted wnt1 by increasing the expression of miR-148a-3p in a dose-dependent manner, thereby downregulating the mRNA and protein expressions of β-catenin in cartilage tissue and upregulating the mRNA and protein expressions of GSK-3β. CGG may control the miR-148a-3p/wnt/β-catenin signaling pathway to decrease the levels of its downstream target genes MMP-13 and MMP-3, increase the expressions of Col2al and Aggrecan, and downregulate the contents of inflammatory cytokines IL-6, TNF-α, and IL-1β, thereby improving the metabolism of cartilage extracellular matrix and alleviating the degeneration of articular cartilage in KOA.

Comparison of a Routine Magnetic Resonance Imaging &amp; T2* Mapping of Articular Cartilage in Knee Osteoarthritis

Purpose To detect the knee articular cartilage lesions in T2* mapping as compared to a routine standard magnetic resonance imaging (MRI) at 3T. Material and Methods Twenty-five patients, complaining of knee pain and trauma, underwent knee MRI and were imaged with a standard knee MRI protocol (proton-density-weighted Fat Sat sagittal and axial series, T2weighted sagittal and axial series, and T1-weighted coronal series) and Proton density 3D sagittal and axial sequences are added, then images of T2* relaxation time is generated with color-coded mapping representing the relaxation time. The detected lesions were evaluated for lesion width (mm), lesion depth (1/3, 2/3, or 3/3 of cartilage thickness), and T2 values (20–40 ms, 40–60 ms, or 60– 80 ms). Results The study was conducted on 25 patients (13 female &amp; 12 male with a mean of 44.92 ± 11.74 years). 87 lesions were detected both on MRI and T2 maps, while 41 lesions were visible only on T2* maps. The cartilage lesions’ width and depth measurements showed no statistically significant difference on T2 maps as compared to standard knee MRI. Many lesions (45) had moderately (T2 40–60 ms) increased T2 values, while 29 lesions had slightly (T2 20–40 ms) and 13 lesions with remarkably (T2 60– 80 ms) increased T2 relaxation times. Conclusion T2 mapping of articular cartilage is efficient in cartilage evaluation and may reveal early cartilage lesions not visible on standard clinical MRI.

Electroacupuncture Exerts Chondroprotective Effect in Knee Osteoarthritis of Rabbits Through the Mitophagy Pathway.

Mitochondrial dysfunction of chondrocytes has become an area of focus in Knee Osteoarthritis (KOA) in recent years. Activation of mitophagy could promote the survival of chondrocytes and alleviate cartilage degeneration. The aim of this study was to explore whether mitophagy was involved in the cartilage protection of KOA rabbits after electroacupuncture (EA) intervention. The rabbits were divided into 3 groups, Control group, KOA group, EA group, with 6 rabbits in each group. KOA model rabbits were established by modified Videman's extended immobilization method for 6 weeks and randomly divided into KOA group and EA group. The rabbits in EA group were treated every other day for 3 weeks. The degree of cartilage degeneration was detected by Safranine O-Fast Green staining and immunofluorescence. The morphological changes of chondrocytes mitochondria were detected by transmission electron microscope. ATP concentration in cartilage was measured by ATP Assay Kit. The changes of Pink1-Parkin signal pathway were detected by immunofluorescence, Western blot, and Real-time PCR. The morphology showed that EA could reduce the degeneration of KOA cartilage and increase the distribution of collagen II. We also found that EA could activate mitophagy in KOA rabbit chondrocytes to remove damaged mitochondria and restore mitochondrial homeostasis, which was manifested as increasing the expression of LC3 II/I, promoting the colocalization of TOM20 and LC3B, reducing the accumulation of mitochondrial markers outer mitochondrial membrane 20 (TOM20) and inner mitochondrial membrane 23 (TIM23), and increasing ATP production in chondrocytes. This regulation might be achieved by upregulating the Pink1-Parkin signal pathway. EA may play a role in protecting KOA cartilage by activating mitophagy mediated through Pink1-Parkin pathway.

Ultrasonographic echo intensity in the medial femoral cartilage is enhanced prior to cartilage thinning in women with early mild knee osteoarthritis.

We aimed to determine whether altered cartilage echo intensity is associated with knee osteoarthritis (OA) severity and whether the alteration occurs before thinning of the femoral cartilage in knee OA. The medial femoral cartilage thickness and echo intensity of 118 women aged ≥ 50years were assessed using an ultrasound imaging device. Based on the Kellgren-Lawrence (KL) grade and knee symptoms, participants were classified into five groups: control (asymptomatic grades 0-1), early OA (symptomatic grade 1), grade 2, grade 3, and grade 4. Analysis of covariance, with adjusted age and height, and the Sidak post hoc test were used to assess the differences in cartilage thickness and echo intensity in knees with varying OA severity. The echo intensity on longitudinal images, equivalent to the tibiofemoral weight-bearing surface, was significantly higher in the grade 2 group than that in the control group (p = 0.049). However, no significant difference was noted in cartilage thickness (n.s.). In the grades 3 and 4 groups, cartilage thickness became thinner as OA progressed (p < 0.001 and p < 0.001, respectively). However, the cartilage echo intensity was not significantly enhanced compared with that of the grade 2 group (n.s.). There were no significant differences in the cartilage thickness and echo intensity between the early OA and control groups on the longitudinal images (n.s.). The echo intensity of the medial femoral cartilage was high in patients with KL grade 2, without decreased thickness. Our findings suggested that higher echo intensity is a feature of early cartilage degeneration in mild knee OA. Further studies are needed to establish this feature as a useful screening parameter of early cartilage degeneration in knee OA. Level III.

HUCMSCS-DERIVED EXOSOMES SUPPRESS OSTEOARTHRITIS IN RABBITS THROUGH INHIBITING CCL2

Osteoarthritis (OA), the most prevalent chronic joint disease, represents a relevant social and economic burden worldwide. Human umbilical cord mesenchymal stem cells (HUCMSCs) have been used for injection into the joint cavity to treat OA. The aim of this article is to clarify whether Huc-MSCs derived exosomes could inhibit the progression of OA and the mechanism in this process.A rabbit OA model was established by the transection of the anterior cruciate ligament. The effects of HUCMSCs or exosomes derived from HUCMSCs on repairing articular cartilage of knee osteoarthritis was examined by micro-CT. Immunohistochemical experiments were used to confirm the expression of relevant inflammatory molecules in OA. In vitro experiments, Transwell assay was used to assess the migration of macrophages induced by TNF-a.Results showed that a large number of macrophages migrated in arthcular cavity in OA model in vivo, while local injection of HUCMSCs and exosomes did repair the articular cartilage. Immunohistochemical results suggested that the expression of CCL2 and CD68 in the OA rabbit model increased significantly, but was significantly reduced by HUCMSCs or exosomes. Transwell assay showed that both HUCMSCs and exosomes can effectively inhibit the migration of macrophage.In conclusion, the exosomes derived by HUCMSCs might might rescue cartilage defects in rabbit through its anti-inflammatory effects through inhibiting CCL2.

Allogeneic Umbilical Cord-Blood-Derived Mesenchymal Stem Cells and Hyaluronate Composite Combined with High Tibial Osteotomy for Medial Knee Osteoarthritis with Full-Thickness Cartilage Defects.

Background and Objectives: Although the effects of cartilage repair in patients who are undergoing high tibial osteotomy (HTO) remains controversial, cartilage repair may be required for the full-thickness cartilage defect because of a concern of lower clinical outcome. The purpose of this study was to investigate clinical outcome and cartilage repair following implantation of allogeneic umbilical cord-blood-derived MSCs (UCB-MSCs)-hyaluronate composite in patients who received HTO for medial knee osteoarthritis (OA) with full-thickness cartilage defect. Materials and Methods: Inclusion criteria were patients with a medial knee OA, a full-thickness cartilage defect (International Cartilage Repair Society (ICRS) grade IV) ≥ 3 cm2 of the medial femoral condyle, and a varus deformity ≥ 5°. The full-thickness cartilage defect was treated with implantation of an allogeneic UCB-MSCs-hyaluronate composite following medial open-wedge HTO. Visual analogue scale for pain and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score were assessed at each follow-up. Cartilage repair was assessed by the ICRS cartilage repair assessment system at second-look arthroscopy when the plate was removed. Results: Twelve patients (mean age 56.1 years; mean defect size: 4.5 cm2) were included, and 10 patients underwent second-look arthroscopy during plate removal after a minimum of 1 year after the HTO. At the final follow-up of mean 2.9 years (range; 1-6 years), all clinical outcomes had improved. At second-look arthroscopy, repaired tissue was observed in all cases. One case (10%) showed grade I, seven (70%) cases showed grade II, and two (20%) cases showed grade III according to ICRS cartilage repair assessment system, which meant that 80% showed an overall repair assessment of "normal" or "nearly normal". Conclusion: Allogeneic UCB-MSCs-HA composite implantation combined with HTO resulted in favorable clinical outcome and cartilage repair in all cases. These findings suggest that UCB-MSCs-HA composite implantation combined with HTO would be a good therapeutic option for patients with knee OA and full-thickness cartilage defects.

Targeting CD38 to Suppress Osteoarthritis Development and Associated Pain After Joint Injury in Mice.

This study was undertaken to determine the role of CD38, which can function as an enzyme to degrade NAD+ , in osteoarthritis (OA) development. Human knee cartilage from normal donors and OA donors were examined for CD38 expression. "Gain-of-function," through overexpression of CD38 via transient transfection, and "loss-of-function," through pharmacologic inhibition of CD38, approaches were used to assess the effects of CD38 on intracellular NAD+ :NADH ratio and catabolic activity in chondrocytes. We also initiated joint injury-induced OA by surgical destabilization of the medial meniscus (DMM) in CD38 knockout mice and wild-type (WT; C57BL/6) mice and in WT male mice in the presence or absence of apigenin treatment. Cartilage degradation, synovial inflammation, subchondral bone changes, and pain behavior were evaluated after DMM surgery. We also examined expression of CD38 and the neuropeptide calcitonin gene-related peptide (CGRP) in knee sections from these mice. CD38 expression was up-regulated in human knee OA cartilage and in chondrocytes stimulated with the proinflammatory cytokine interleukin-1β (IL-1β). Overexpression of CD38 in chondrocytes resulted in reduced cellular NAD+ :NADH ratio and augmented catabolic responses to IL-1β. These effects were reversed by pharmacologic inhibition of CD38. Cartilage degradation and synovial inflammation, associated with increased CD38 expression in cartilage and synovium, osteophyte formation and subchondral bone sclerosis, and pain-like behavior linked to increased CGRP expression in the synovium were observed in WT mice after joint injury. Such effects were significantly reduced in mice deficient in CD38 through either genetic knockout or pharmacologic inhibition. CD38 deficiency exerts OA disease-modifying effects. Inhibition of CD38 has the potential to be a novel therapeutic approach for OA treatment.

Differential gene co-expression network analyses reveal novel molecules associated with transcriptional dysregulation of key biological processes in osteoarthritis knee cartilage

ObjectivesTo compare co-expression networks of normal and osteoarthritis knee cartilage to uncover molecules associated with the transcriptional misregulation compromising biological processes (BPs) critical for cartilage homeostasis. DesignNormal and osteoarthritis human knee cartilage RNA-seq GSE114007 dataset was obtained from the Gene Expression Omnibus database. Partial Correlation and Information Theory (PCIT) algorithm was used to build co-expression networks containing all nodes connecting to at least one differentially expressed gene (DEG) in normal and osteoarthritis networks. Hub and hub centrality genes were used to perform functional enrichment analysis. Enriched BPs known to be associated with both healthy and diseased cartilage were compared in depth. ResultsDifferential co-expression network analyses allowed the identification of DDX43 and USP42 as exclusively co-expressed with DEGs in normal and osteoarthritis networks, respectively. The top hub and hub centrality genes of these networks were HIST1H3A and SNHG12 (normal) and TAF9B and OTUD1 (osteoarthritis). Enrichment analysis revealed several shared BPs between the contrasting groups, which are well-known in osteoarthritis pathogenesis. Protein-protein interaction network analysis for these BPs showed a global down-regulation of transcription factors in osteoarthritis. Specific transcription factors were identified as pleiotropic mediators in articular cartilage maintenance since they take part in several BPs. In addition, chromatin organisation and modification proteins were found relevant for osteoarthritis development. ConclusionDifferential gene co-expression analysis allowed the identification of novel and high priority therapeutic candidate genes that may drive modifications in the transcriptional “status” of cartilage in osteoarthritis.

Expression and regulation of recently discovered hyaluronidases, HYBID and TMEM2, in chondrocytes from knee osteoarthritic cartilage

Destruction of articular cartilage in osteoarthritis (OA) is initiated by depletion of the hyaluronan (HA)-aggrecan network, followed by degradation of the collagen fibrils. Previously, we reported the implications of HA-binding protein involved in HA depolymerization (HYBID), alias cell migration-inducing protein (CEMIP) and KIAA1199, for HA degradation. However, transmembrane protein 2 (TMEM2), which is ~ 50% homologous to HYBID, was discovered as another hyaluronidase, but their expression and regulation by OA chondrocytes remain elusive. Here we report that the absolute mRNA copy numbers of HYBID are significantly (7.1-fold) higher in OA cartilage than normal cartilage, whereas TMEM2 levels are not different between the groups. HA-degrading activity of cultured OA chondrocytes disappeared by siRNA-mediated knockdown of HYBID, but not TMEM2. HYBID expression was significantly up-regulated by treatment with interleukin-6 (IL-6) or tumor necrosis factor-α (TNF-α) and additively increased by the combined treatment. No significant changes in the TMEM2 expression were seen by the factors examined. IL-1α remarkably enhanced IL-6 production and increased HYBID expression when soluble IL-6 receptor was supplemented. These results demonstrate that in stark contrast to the constitutive expression of TMEM2 and its negligible HA-degrading activity, HYBID is overexpressed in OA cartilage and up-regulated by IL-6 and TNF-α in OA chondrocytes.

The Expression of αvβ3 and Osteopontin in Osteoarthritic Knee Cartilage and Their Correlations With Disease Severity and Chondrocyte Senescence.

Osteoarthritis (OA) is the main joint disease associated with aging. Previous studies have confirmed that both osteopontin (OPN) and αvβ3 integrin are involved in the progression of knee OA. The purpose of this study was to determine the expression of OPN and αvβ3 integrin and chondrocyte senescence levels in OA. Forty-six cartilage tissues from normal and knee OA patients were divided into 4 groups of normal, minor, moderate, and severe lesions based on the Mankin score. Immunohistochemistry and western blotting were used to determine the expression of αvβ3, OPN, and senescent-associated-β-galactosidase (SAβ-gal) in articular cartilage. Then, Spearman's correlation was used to analyze the correlations between the Mankin scores and αvβ3, OPN and SAβ-gal. Pearson correlation analysis was used to analyze the correlations among αvβ3, OPN, and SAβ-gal. The expression of OPN, αvβ3, and SAβ-gal in articular cartilage was explored. αvβ3, OPN, and SAβ-gal proteins were all elevated in OA cartilage, and the correlation coefficient between the Mankin score and the average optical density value of αvβ3, OPN, SAβ-gal were r =0.60, r =0.75, and r =0.87, respectively, all P <0.001; the correlation between the average optical density value of αvβ3 and OPN was r =0.3191, P <0.05; the correlation between αvβ3 and SAβ-gal was r =0.4955, P <0.001; and the correlation between OPN and SAβ-gal was r =0.7821, P <0.001. The correlations among αvβ3, OPN, and SAβ-gal expression in articular cartilage might be important in OA progression and pathogenesis. Nonetheless, more research is needed to elucidate the exact contribution of αvβ3, OPN, and SAβ-gal to the degenerative process of OA.