Soluble biomarkers in osteoarthritis in 2022: year in review

Ghrelin suppresses apoptosis and autophagy in osteoarthritis synovial cells by modulating the ADORA2B/PI3K/Akt/mTOR signaling pathway

Given the pivotal role that apoptosis and autophagy play in the pathogenesis of osteoarthritis (OA), the current study aims to examine the regulatory effects of ghrelin on these processes via the ADORA2B/PI3K/Akt/mTOR signaling pathway. Serum levels of ghrelin were measured in both OA patients and healthy controls using an ELISA kit. Cell proliferation was evaluated through the Cell Counting Kit-8 (CCK-8) assay, while Western blot analysis was utilized to determine the expression levels of autophagy-related proteins (LC3II/I, BECLIN-1) and apoptosis markers (BAX, Bcl-2), as well as to assess the activation status of the PI3K/Akt/mTOR signaling pathway in OA synovial cells. These analyses were performed under conditions of ADORA2B and mTOR silencing, as well as in control settings. The results revealed that ghrelin expression was significantly reduced in the serum of OA patients. Furthermore, ghrelin was found to enhance synovial cell proliferation while simultaneously inhibiting apoptosis and autophagy, as evidenced by lowered expression levels of LC3/I, BECLIN-1, and BAX, alongside an increase in Bcl-2 expression. This modulation occurred through the regulation of the PI3K/Akt/mTOR signaling pathway mediated by ADORA2B. These findings underscore the role of ghrelin in the progression of osteoarthritis by influencing synovial cell activity through the ADORA2B/PI3K/Akt/mTOR pathway, thus laying the groundwork for investigating targeted therapeutic strategies in clinical practice.

Comparative Proteomic Analysis of Osteoarthritis and Rheumatoid Arthritis: Identifying Potential Biomarkers

This study investigates proteomic differences between knee osteoarthritis (OA) and rheumatoid arthritis (RA) to identify protein signatures with potential diagnostic and therapeutic relevance. Using SWATH mass spectrometry, synovial fluid proteome from OA patients across Kellgren-Lawrence OA grades 2, 3, and 4 was analyzed and compared with RA patients. Out of 333 quantified proteins, 45 were differentially expressed, including aggrecan, versican, and inflammation-related proteins (e.g., CRP, APCS, S100A8, and SAA2). ELISA validation confirmed aggrecan, versican, and cartilage oligomeric matrix protein (COMP) as significantly altered proteins in OA compared to RA, along with distinct trends with OA progression and mirrored patterns in paired serum samples. ROC curve analysis highlighted COMP's strong diagnostic potential, with an AUC of 96%, 87.2%, and 85.2% for OA grades 2, 3, and 4 versus RA, respectively. COMP differentiated OA from RA at a synovial fluid concentration of < 3136 ng/mL, AUC of 92.1%, 89% sensitivity, and 82% specificity. Versican also demonstrated diagnostic utility, particularly in later OA stages. Gender-specific analysis revealed no differences for aggrecan and versican, while COMP levels were significantly higher in males. Simultaneously, a lower aggrecan, versican, and COMP levels were observed in OA (females) as compared to RA, potentially linked to estrogen decline with age and cartilage degradation. However, gender variability underscores the need for a larger, sex-balanced cohort study. Future studies could aim to account for validating COMP's diagnostic potential with healthy controls, demonstrating its reliability to characterize different OA grades.

Can Circulating MicroRNAs, Cytokines, and Adipokines Help to Differentiate Psoriatic Arthritis from Erosive Osteoarthritis of the Hand? A Case-Control Study

The differential diagnosis of erosive osteoarthritis of the hand (EHOA) and psoriatic arthritis (PsA) is challenging, especially considering the absence of specific diagnostic biomarkers. The aim of the present study was to evaluate whether a pattern of microRNAs (miRNAs) (miR-21, miR-140, miR-146a, miR-155, miR-181a, miR-223), pro-inflammatory cytokines [interleukin (IL)-1β, IL-6, IL-17a, IL-23a, and tumor necrosis factor (TNF)-α], and adipokines (adiponectin, chemerin, leptin, resistin, and visfatin) could help to differentiate EHOA from PsA. Fifty patients with EHOA, fifty patients with PsA, and fifty healthy subjects (HS) were studied. The gene expression of miRNAs and cytokines were evaluated by real-time PCR from peripheral blood mononuclear cells and serum levels of cytokines and adipokines were quantified by ELISA in PsA and EHOA patients and HS. Gene expression showed the significant up-regulation of the analyzed miRNAs in EHOA and PsA patients as compared to HS and higher miR-155 in EHOA vs. PsA patients. The expression levels of IL-1β and IL-6 did not show any significant differences between EHOA and PsA, while IL-17a and IL-23a were significantly up-regulated in PsA compared to EHOA. Circulating TNF-α levels were higher in EHOA compared to PsA, while PsA patients exhibited significantly elevated levels of IL-23a. The combination of miR-155 with C-reactive protein enhanced the ability to differentiate EHOA from PsA, further supporting the potential of miR-155 as a diagnostic biomarker.

[Biomarkers and Their Role in Understanding Osteoarthritis]

Osteoarthritis (OA) is a degenerative joint disease characterized by progressive damage and loss of articular cartilage with concomitant structural and functional changes in the joint. It is the most common cause of joint pain globally and the resulting productivity loss to the economy. The clinical symptoms of osteoarthritis are mostly determined by the difficulties of patients related to the development of articular degenerative changes, which secondarily lead to joint stiffness and functional limitation. The diagnosis of this disease is currently based on typical clinical symptoms and radiographic findings (e.g. joint space narrowing, osteophytes, subchondral sclerosis, etc.). These parameters, however, are difficult to detect in the early stages of the disease and are most often recognized in the advanced stages. For these reasons, the diagnosis of osteoarthritis is often delayed until irreversible destruction of joint tissue occurs and conservative treatment is less effective. Despite recent scientific progress in understanding the genetic and molecular principles of joint degeneration, currently there is no reliable causal therapy for OA. This review aims to summarize current knowledge of osteoarthritis and possible future directions for diagnosis and early intervention. One of such directions is the study of the so-called biomarkers. A biomarker is defined as an indicator of biological processes and can include radiographic, histological, physiological, or molecular characteristics. In particular, molecular biomarkers are widely studied in knee OA. Attention of the research community is focused on the study of biomarkers as a method of detection and prediction of the early stages of osteoarthritis before irreversible joint damage occurs. Biomarkers help develop more effective and, above all, personalized treatment, thus improve the overall clinical approach to the patient.

MicroRNA signature for early prediction of knee osteoarthritis structural progression using integrated machine and deep learning approaches

OBJECTIVE

Conventional methodologies are ineffective in predicting the rapid progression of knee osteoarthritis (OA). MicroRNAs (miRNAs) show promise as biomarkers for patient stratification. We aimed to develop a miRNA prognosis model for identifying knee OA structural progressors/non-progressors using integrated machine/deep learning tools.

METHODS

Baseline serum miRNAs from Osteoarthritis Initiative (OAI) participants were isolated and sequenced. Participants were categorized based on their likelihood of knee structural progression/non-progression using magnetic resonance imaging and X-ray data. For prediction model development, 152 OAI participants (91 progressors, 61 non-progressors) were used. MiRNA features were reduced through VarClusHi clustering. Key miRNAs and OA determinants (age, sex, body mass index, race) were identified using seven machine learning tools. The final prediction model was developed using advanced machine/deep learning techniques. Model performance was assessed with area under the curve (AUC) (95% confidence intervals) and accuracy. Monte Carlo cross-validation ensured robustness. Model validation used 30 OAI baseline plasma samples from an independent set of participants (14 progressors, 16 non-progressors).

RESULTS

Feature clustering selected 107 miRNAs. Elastic Net was chosen for feature selection. An optimized prediction model based on an Artificial Neural Network comprising age and four miRNAs (hsa-miR-556-3p, hsa-miR-3157-5p, hsa-miR-200a-5p, hsa-miR-141-3p) exhibited excellent performance (AUC, 0.94 [0.89, 0.97]; accuracy, 0.84 [0.77, 0.89]). Model validation performance (AUC, 0.81 [0.63, 0.92]; accuracy, 0.83 [0.66, 0.93]) demonstrated the potential for generalization.

CONCLUSION

This study introduces a novel miRNA prognosis model for knee OA patients at risk of structural progression. It requires five baseline features, demonstrates excellent performance, is validated with an independent set, and holds promise for future personalized therapeutic monitoring.

Circulating miR-126-3p is a mechanistic biomarker for knee osteoarthritis

Osteoarthritis is a major contributor to pain and disability worldwide, yet there are currently no validated soluble biomarkers or disease-modifying treatments. Given that microRNAs are promising mechanistic biomarkers that can be therapeutically targeted, in this study, we aimed to identify and prioritize reproducible circulating microRNAs associated with radiographic knee osteoarthritis. Across four independent cohorts, we find circulating miR-126-3p is elevated in knee osteoarthritis versus controls. Across six primary human knee osteoarthritis tissues, miR-126-3p is highest in subchondral bone, fat pad and synovium, and lowest in cartilage. Following both intravenous and intra-articular miR-126-3p mimic treatment in a surgical mouse model of knee osteoarthritis, we show reduced disease severity in males. In human knee osteoarthritis biospecimens, miR-126-3p mimic treatment reduces genes and markers associated with angiogenesis, as well as genes linked to osteogenesis, adipogenesis, and synovitis-processes secondary to angiogenesis. Our findings indicate that miR-126-3p is elevated in knee osteoarthritis and mitigates disease severity, supporting its potential as a biomarker and therapeutic target.

CircTBCK protects against osteoarthritis by regulating extracellular matrix and autophagy

Osteoarthritis (OA) is a widespread chronic bone and joint disease for which there is currently no effective preventive or therapeutic treatment. Accumulating evidence indicates that circular RNAs (circRNAs), a class of noncoding RNAs, play critical roles in OA. Therefore, in this study, we aimed to reveal an unexplored circTBCK and elucidate its mechanism of action in the pathological process of OA. The different expression of circTBCK was obtained both in vitro and in vivo. In the in vivo model, mice were induced via destabilization of the medial meniscus (DMM) surgery, while in vitro model, mouse cells like primary chondrocytes of newborn mice and ATDC5 cell line were treated with IL-1β treatment (10 ng/mL for 24 h). The level of circTBCK was examined by quantitative real-time polymerase chain reaction (qRT-PCR). After circTBCK was overexpressed or knocked down, IL-1β treatment was performed, and then, chondrocyte viability was detected via a Cell Counting Kit-8 (CCK-8) assay at 0, 24, 48, or 72 h. To assess type II collagen (Collagen II) expression, immunofluorescence (IF) analysis was used. The levels of mRNAs and proteins related to proliferation, the extracellular matrix (ECM) and autophagy were determined by qRT-PCR and Western blotting. Compared with OA treatment, primary chondrocytes with treatment of both circTBCK overexpression and IL-1βincreased the expression of anabolic factors-Collagen II and SRY-box transcription factor 9 (SOX9), proliferation-related molecules-Ki-67 and proliferating cell nuclear antigen (PCNA), and autophagy-related molecules-Microtubule-associated protein 1 light chain 3 (LC3), B-cell lymphoma 1 (Bcl1), and autophagy-related 5 (Atg5) and decreased Sequestosome 1 (SQSTM1 or P62). In contrast, knockdown of circTBCK aggravated the chondrocyte degeneration induced by IL-1β. Overall, our findings suggest that circTBCK, an unexplored circRNA, could regulate autophagy, proliferation, and the extracellular matrix (ECM) to mitigate the development of OA, suggesting a possible target for OA prevention and therapy.

Serum fibulin-3 as a diagnostic and prognostic biomarker in patients with knee osteoarthritis

BACKGROUND

Osteoarthritis is a chronic degenerative disorder with rising prevalence. Early detection of structural damage is difficult. Consequently, there is a pressing demand for reliable biomarkers that enable an earlier diagnosis of osteoarthritis. The aim is to investigate the level of serum fibulin-3 in patients with primary knee osteoarthritis and its correlation with disease severity.

SUBJECTS AND METHODS

A case-control study was conducted at the Baqubah Teaching Hospital from November 2023 to January 2024. One hundred twenty persons participated in this study (eighty females with the diagnosis of knee osteoarthritis in its early and late stages, and forty age-matched, apparently healthy control. Serum fibulin-3, ESR, CRP, and calcium levels were measured for all participants. Ethical approval was obtained. SPSS was used for data analysis.

RESULTS

Patients with osteoarthritis had considerably higher serum levels of fibulin-3. In patients with late-stage knee osteoarthritis, this rise was greater than in earlier stages. Serum fibulin and ESR are positively correlated. Fibulin's area under the curve is 0.830 for diagnosis and 0.709 for differentiating between osteoarthritis's early and late stages.

CONCLUSION

Serum levels of fibulin-3 can act as diagnostic markers for OA and may be useful in determining the severity of knee osteoarthritis.

Evaluation of circulating microRNA signature in patients with erosive hand osteoarthritis: The HOAmiR study

OBJECTIVES

To identify circulating micro-RNAs differentially expressed in patients with erosive hand osteoarthritis (HOA) compared to patients with non-erosive HOA and patients without HOA.

METHODS

In the screening phase, 768 well-characterized micro-RNAs using Taqman low-density array cards were measured in 30 sera from 10 patients with erosive HOA, 10 patients with non-erosive HOA, and 10 controls without HOA, matched for age and body mass index (BMI). In a second step, we validated the micro-RNAs identified at the screening phase (adjusted p value < 0.05 after false discovery rate correction using Benjamini-Hochberg method and literature review) in larger samples (60 patients with erosive HOA and 60 patients without HOA matched for age and BMI).

RESULTS

In the screening phase, we identified 21 down-regulated and 4 up-regulated micro-RNAs of interest between erosive HOA and control groups. Among these, 9 micro-RNAs (miR-373-3p, miR-558, miR-607, miR-653-5p, miR-137 and miR448 were down-regulated, and miR-142-3p, miR-144-3p and miR-34a-5p were up-regulated) were previously described in chondrocytes homeostasis or OA. We found only one significantly down-regulated micro-RNA between erosive and non-erosive HOA. In the validation phase, we showed replication of a single micro-RNA the significant downregulation of miR-196-5p, that had been previously identified in the screening phase among patients with erosive HOA compared to those without HOA. After reviewing the literature and the miRNA-gene interaction prediction model, we found that this microRNA could interact with bone homeostasis and HOXC8, which could explain its role in osteoarthritis.

CONCLUSIONS

We found that miR-196-5p was down-regulated in patients with erosive HOA and some of its targets could explain a role in OA.

Evolution and advancements in genomics and epigenomics in OA research: How far we have come

OBJECTIVE

Osteoarthritis (OA) is the most prevalent musculoskeletal disease affecting articulating joint tissues, resulting in local and systemic changes that contribute to increased pain and reduced function. Diverse technological advancements have culminated in the advent of high throughput "omic" technologies, enabling identification of comprehensive changes in molecular mediators associated with the disease. Amongst these technologies, genomics and epigenomics - including methylomics and miRNomics, have emerged as important tools to aid our biological understanding of disease.

DESIGN

In this narrative review, we selected articles discussing advancements and applications of these technologies to OA biology and pathology. We discuss how genomics, deoxyribonucleic acid (DNA) methylomics, and miRNomics have uncovered disease-related molecular markers in the local and systemic tissues or fluids of OA patients.

RESULTS

Genomics investigations into the genetic links of OA, including using genome-wide association studies, have evolved to identify 100+ genetic susceptibility markers of OA. Epigenomic investigations of gene methylation status have identified the importance of methylation to OA-related catabolic gene expression. Furthermore, miRNomic studies have identified key microRNA signatures in various tissues and fluids related to OA disease.

CONCLUSIONS

Sharing of standardized, well-annotated omic datasets in curated repositories will be key to enhancing statistical power to detect smaller and targetable changes in the biological signatures underlying OA pathogenesis. Additionally, continued technological developments and analysis methods, including using computational molecular and regulatory networks, are likely to facilitate improved detection of disease-relevant targets, in-turn, supporting precision medicine approaches and new treatment strategies for OA.

Blood and urine biomarkers for the diagnosis of early stages of knee osteoarthritis: A systematic review

Purpose

To identify biomarkers in human blood or urine at an early stage of knee osteoarthritis (OA) and to elucidate if any can accurately differentiate between healthy controls and early knee OA patients and be considered as a candidate for widespread clinical use for early diagnosis of the disease.

Methods

Medline, Embase and Web of Science were screened to identify comparative studies measuring differences in blood or urine biomarkers between healthy controls and knee OA patients at an early stage (grade 1 or 2 Kellgren-Laurence). Two independent reviewers screened the abstracts for eligibility, reviewed the full texts, assessed the methodological quality and extracted the data. The Joanna Briggs Institute critical appraisal tool for diagnostic test accuracy studies was used to assess the quality of the included studies. Due to relevant heterogeneity, meta-analysis was not appropriate.

Results

Five studies met the eligibility criteria. The examined biomarkers were adropin, collagen type II metabolite, C-terminal cross-linked telopeptide of type II collagen, C-terminal cross-linked telopeptide of type I collagen, cartilage oligomeric matrix protein, matrix metalloproteinase 3, N-terminal propeptide of procollagen type IIA, type I procollagen N-terminal propeptides, N-terminal osteocalcin, angiopoietin-2, follistatin, granulocyte colony-stimulating factor, hepatocyte growth factor, interleukin-8, leptin, platelet-derived growth factor-BB, platelet endothelial cell adhesion molecule-1, vascular endothelial growth factor and calprotectin and totalling 19 biomarkers. All of the biomarkers were studied only once in the selected papers.

Conclusions

There is no reliable biomarker available to differentiate between early knee OA in patients and healthy controls, but a potential role of a cluster of biomarkers to close this gap. There are several limitations, including inappropriate study designs, small sample sizes, nonconsecutive patient groups and inadequate statistical methods for evaluating biomarker performance in studies included.

Level of Evidence

Level III.

Unveiling inflammatory and prehypertrophic cell populations as key contributors to knee cartilage degeneration in osteoarthritis using multi-omics data integration

OBJECTIVES

Single-cell and spatial transcriptomics analysis of human knee articular cartilage tissue to present a comprehensive transcriptome landscape and osteoarthritis (OA)-critical cell populations.

METHODS

Single-cell RNA sequencing and spatially resolved transcriptomic technology have been applied to characterise the cellular heterogeneity of human knee articular cartilage which were collected from 8 OA donors, and 3 non-OA control donors, and a total of 19 samples. The novel chondrocyte population and marker genes of interest were validated by immunohistochemistry staining, quantitative real-time PCR, etc. The OA-critical cell populations were validated through integrative analyses of publicly available bulk RNA sequencing data and large-scale genome-wide association studies.

RESULTS

We identified 33 cell population-specific marker genes that define 11 chondrocyte populations, including 9 known populations and 2 new populations, that is, pre-inflammatory chondrocyte population (preInfC) and inflammatory chondrocyte population (InfC). The novel findings that make this an important addition to the literature include: (1) the novel InfC activates the mediator MIF-CD74; (2) the prehypertrophic chondrocyte (preHTC) and hypertrophic chondrocyte (HTC) are potentially OA-critical cell populations; (3) most OA-associated differentially expressed genes reside in the articular surface and superficial zone; (4) the prefibrocartilage chondrocyte (preFC) population is a major contributor to the stratification of patients with OA, resulting in both an inflammatory-related subtype and a non-inflammatory-related subtype.

CONCLUSIONS

Our results highlight InfC, preHTC, preFC and HTC as potential cell populations to target for therapy. Also, we conclude that profiling of those cell populations in patients might be used to stratify patient populations for defining cohorts for clinical trials and precision medicine.

Exploring the Early Molecular Pathogenesis of Osteoarthritis Using Differential Network Analysis of Human Synovial Fluid

The molecular mechanisms that drive the onset and development of osteoarthritis (OA) remain largely unknown. In this exploratory study, we used a proteomic platform (SOMAscan assay) to measure the relative abundance of more than 6000 proteins in synovial fluid (SF) from knees of human donors with healthy or mildly degenerated tissues, and knees with late-stage OA from patients undergoing knee replacement surgery. Using a linear mixed effects model, we estimated the differential abundance of 6251 proteins between the three groups. We found 583 proteins upregulated in the late-stage OA, including MMP1, collagenase 3 and interleukin-6. Further, we selected 760 proteins (800 aptamers) based on absolute fold changes between the healthy and mild degeneration groups. To those, we applied Gaussian Graphical Models (GGMs) to analyze the conditional dependence of proteins and to identify key proteins and subnetworks involved in early OA pathogenesis. After regularization and stability selection, we identified 102 proteins involved in GGM networks. Notably, network complexity was lost in the protein graph for mild degeneration when compared to controls, suggesting a disruption in the regular protein interplay. Furthermore, among our main findings were several downregulated (in mild degeneration versus healthy) proteins with unique interactions in the healthy group, one of which, SLCO5A1, has not previously been associated with OA. Our results suggest that this protein is important for healthy joint function. Further, our data suggests that SF proteomics, combined with GGMs, can reveal novel insights into the molecular pathogenesis and identification of biomarker candidates for early-stage OA.

Osteoarthritis: Insights into Diagnosis, Pathophysiology, Therapeutic Avenues, and the Potential of Natural Extracts

Osteoarthritis (OA) stands as a prevalent and progressively debilitating clinical condition globally, impacting joint structures and leading to their gradual deterioration through inflammatory mechanisms. While both non-modifiable and modifiable factors contribute to its onset, numerous aspects of OA pathophysiology remain elusive despite considerable research strides. Presently, diagnosis heavily relies on clinician expertise and meticulous differential diagnosis to exclude other joint-affecting conditions. Therapeutic approaches for OA predominantly focus on patient education for self-management alongside tailored exercise regimens, often complemented by various pharmacological interventions primarily targeting pain alleviation. However, pharmacological treatments typically exhibit short-term efficacy and local and/or systemic side effects, with prosthetic surgery being the ultimate resolution in severe cases. Thus, exploring the potential integration or substitution of conventional drug therapies with natural compounds and extracts emerges as a promising frontier in enhancing OA management. These alternatives offer improved safety profiles and possess the potential to target specific dysregulated pathways implicated in OA pathogenesis, thereby presenting a holistic approach to address the condition's complexities.

Noncoding RNAs in skeletal development and disorders

Protein-encoding genes only constitute less than 2% of total human genomic sequences, and 98% of genetic information was previously referred to as "junk DNA". Meanwhile, non-coding RNAs (ncRNAs) consist of approximately 60% of the transcriptional output of human cells. Thousands of ncRNAs have been identified in recent decades, and their essential roles in the regulation of gene expression in diverse cellular pathways associated with fundamental cell processes, including proliferation, differentiation, apoptosis, and metabolism, have been extensively investigated. Furthermore, the gene regulation networks they form modulate gene expression in normal development and under pathological conditions. In this review, we integrate current information about the classification, biogenesis, and function of ncRNAs and how these ncRNAs support skeletal development through their regulation of critical genes and signaling pathways in vivo. We also summarize the updated knowledge of ncRNAs involved in common skeletal diseases and disorders, including but not limited to osteoporosis, osteoarthritis, rheumatoid arthritis, scoliosis, and intervertebral disc degeneration, by highlighting their roles established from in vivo, in vitro, and ex vivo studies.

Senescence-regulatory factors as novel circulating biomarkers and therapeutic targets in regenerative medicine for osteoarthritis

Recent discoveries reveal that the chronic presence of senescent cells in osteoarticular tissues provides a focal point of disease development for osteoarthritis (OA). Nevertheless, senescence-regulatory factors associated with OA still need to be identified. Furthermore, few diagnostic- and prognostic-validated biochemical markers (biomarkers) are currently used in clinics to evaluate OA patients. In the future, alongside imaging and clinical examination, detecting senescence-regulatory biomarkers in patient fluids could become a prospective method for disease: diagnosis, monitoring, progression and prognosis following treatment. This review summarizes a group of circulating OA biomarkers recently linked to senescence onset. Remarkably, these factors identified in proteomics, metabolomic and microRNA studies could also have deleterious or protective roles in osteoarticular tissue homeostasis. In addition, we discuss their potentially innovative modulation in combination with senotherapeutic approaches, for long-lasting OA treatment.

Plasma Cartilage Acidic Protein 1 Measured by ELISA Is Associated With the Progression to Total Joint Replacement in Postmenopausal Women

OBJECTIVE

To investigate the association of plasma cartilage acidic protein 1 (CRTAC1), a novel biochemical marker of osteoarthritis (OA), and total joint replacement (TJR) in postmenopausal women.

METHODS

The association of plasma CRTAC1 with the incidence of TJR was investigated in a prospective cohort including 478 postmenopausal women. A total of 38 women underwent a TJR for OA during a median follow-up of 18 years. Every one of the TJR cases were age- and BMI (kg/m2)-matched with 2 controls with no TJR from the same cohort. Plasma CRTAC1 was measured before TJR. The association between CRTAC1 and TJR incidence was investigated by conditional logistic regression.

RESULTS

Increased CRTAC1 was associated with a higher risk of TJR with an odds ratio (OR) of 1.80 (95% CI 1.11-2.92) for 1 SD increase, which remained significant after adjusting for Western Ontario and McMaster Universities Osteoarthritis Index, knee OA baseline severity (Kellgren-Lawrence grade), hip OA, and hip bone mineral density. Urinary crosslinked C-telopeptide of type II collagen (CTX-II) was also associated with a higher risk of TJR with an adjusted OR of 1.83 (95% CI 1.11-3.00). When CRTAC1 and CTX-II were included in the same model, both markers were significantly associated with TJR with similar ORs.

CONCLUSION

CRTAC1 is a new risk indicator of TJR for OA in postmenopausal women. Combined with knee and hip OA and CTX-II, it may help to identify subjects at risk for TJR.

Evaluating the causal effect of circulating proteome on the risk of osteoarthritis-related traits

OBJECTIVES

This study aims to identify circulating proteins that are causally associated with osteoarthritis (OA)-related traits through Mendelian randomisation (MR)-based analytical framework.

METHODS

Large-scale two-sample MR was employed to estimate the effects of thousands of plasma proteins on 12 OA-related traits. Additional analyses including Bayesian colocalisation, Steiger filtering analysis, assessment of protein-altering variants and mapping expression quantitative trait loci to protein quantitative trait loci were performed to investigate the reliability of the MR findings; protein-protein interaction, pathway enrichment analysis and evaluation of drug targets were conducted to deepen the understanding and identify potential therapeutic targets of OA.

RESULTS

Dozens of circulating proteins were identified to have putatively causal effects on OA-related traits, and a majority of these proteins were either drug targets or considered druggable.

CONCLUSIONS

Through MR analysis, we have identified numerous plasma proteins associated with OA-related traits, shedding light on protein-mediated mechanisms and offering promising therapeutic targets for OA.

Effect of vitamin D supplementation on circulating level of autophagosome protein LC3A, inflammation, and physical performance in knee osteoarthritis

Aberrant autophagic activity is observed in osteoarthritic joints. Vitamin D was shown to alleviate not only osteoarthritis severity, but also autophagy process. However, the influence of vitamin D on autophagy in knee osteoarthritis (KOA) remains ambiguous. This study aimed to determine the effect of vitamin D2 on serum levels of autophagosome protein LC3A in patients with KOA and whether LC3A levels were correlated with serum 25-hydroxyvitamin D (25(OH)D) and clinical outcomes of patients with KOA. A total of 165 patients with KOA and 25 healthy controls were recruited. Vitamin D2 (ergocalciferol) was administered to patients with KOA at a weekly dosage of 40,000 IU. Serum LC3A, knee pain and functional scores, muscle strength, physical performance, and biochemical parameters were examined before and after 6 months of vitamin D2 supplementation. Serum LC3A levels were significantly higher in patients with KOA than healthy controls. In patients with KOA, vitamin D2 supplementation significantly decreased serum LC3A levels. Furthermore, baseline levels of serum LC3A were significantly associated with radiographic severity, pain and functional scores, total cholesterol, hs-CRP, IL-6, protein carbonyl, and serum 25(OH)D. After adjusting for established confounders, independent relationships among serum LC3A and radiographic severity, pain and functional scores, total cholesterol, hs-CRP, IL-6, protein carbonyl, and serum 25(OH)D were also observed. Vitamin D2 supplementation was shown to not only decrease serum levels of LC3A, inflammatory markers, as well as oxidative stress, but also improve muscle strength and physical performance in patients with KOA.

Inhibition of LncRNA SNHG14 protects chondrocyte from injury in osteoarthritis via sponging miR-137

Long-chain noncoding small nucleolar RNA host gene 14 (LncRNA SNHG14) is highly expressed in various diseases and promotes diseases progression, but the role and mechanism of LncRNA SNHG14 on targeting miR-137 in promoting osteoarthritis (OA) chondrocyte injury remains unclear. To measure the expression of the LncRNAs SNHG14 and miR-137, cell survival, inflammatory response, chondrocyte apoptosis, and extracellular matrix (ECM) levels, we subjected human chondrocytes to a variety of lipopolysaccharide (LPS) concentrations. To measure the luciferase activity of SNHG14-WT and SNHG14-MUT transfected with miR-137 mimic or miR-NC mimic, luciferase reporter genes were utilized. The results showed that chondrocyte viability was significantly inhibited with LPS treatment and chondrocyte inflammatory response, apoptosis and extracellular matrix degradation were significantly increased. However, the above results were significantly reversed after LncRNA SNHG14 inhibition. The luciferase activity bound to miR-137 was decreased in SNHG14-WT group, but there was no change in SNHG14-mut group, which indicated that LncRNA SNHG14 inhibited miR-137 expression as a miRNA sponge. In conclusion, inhibition of LncRNA SNHG14 attenuates chondrocyte inflammatory response, apoptosis and extracellular matrix degradation by targeting miR-137 in LPS induced chondrocytes.

Emerging molecular biomarkers in osteoarthritis pathology

Osteoarthritis (OA) is the most common form of arthritis resulting in joint discomfort and disability, culminating in decline in life quality. Attention has been drawn in recent years to disease-associated molecular biomarkers found in readily accessible biofluids due to low invasiveness of acquisition and their potential to detect early pathological molecular changes not observed with traditional imaging methodology. These biochemical markers of OA have been found in synovial fluid, blood, and urine. They include emerging molecular classes, such as metabolites and noncoding RNAs, as well as classical biomarkers, like inflammatory mediators and by-products of degradative processes involving articular cartilage. Although blood-based biomarkers tend to be most studied, the use of synovial fluid, a more isolated biofluid in the synovial joint, and urine as an excreted fluid containing OA biomarkers can offer valuable information on local and overall disease activity, respectively. Furthermore, larger clinical studies are required to determine relationships between biomarkers in different biofluids, and their impacts on patient measures of OA. This narrative review provides a concise overview of recent studies of OA using these four classes of biomarkers as potential biomarker for measuring disease incidence, staging, prognosis, and therapeutic intervention efficacy.

Evaluation of osteogenic induction potency of miR-27a-3p in adipose tissue-derived human mesenchymal stem cells (AD-hMSCs)

BACKGROUND

Bone tissue as a dynamic tissue is able to repair its minor injuries, however, sometimes the repair cannot be completed by itself due to the size of lesion. In such cases, the best treatment could be bone tissue engineering. The use of stem cells in skeletal disorders to repair bone defects has created bright prospects. On the other hand, changes in the expression level of microRNAs (miRs) can lead to the commitment of mesenchymal stem cells (MSCs) to cell lineage. Many studies reported that post-transcriptional regulations by miRNAs are involved in all stages of osteoblast differentiation.

METHOD

After the preparing adipose tissue-derived mesenchymal stem cells, the target cells from the third passage were cultured in two groups, transfected MSCs with miR-27a-3p (DM.C + P) and control group. In different times, 7 and 14 days after culture, differentiation of these cells into osteoblast were measured using various techniques including the ALP test and calcium content test, Alizarin Red staining, Immunocytochemistry technique (ICC). Also, the relative expression of bone differentiation marker genes including Osteonectin (ON), Osteocalcin (OC), RUNX Family Transcription Factor 2 (RUNX2), Collagen type I alpha 1 (COL1) was investigated by real-time RT PCR.

RESULTS

In comparison with control groups, overexpression of miR-27a-3p in transfected cells resulted in a significant increase in the expression of bone markers genes (ON, OC, RUNX2, COL1), alkaline phosphatase (ALP) activity, and calcium content (p < 0.05). In addition, the results obtained from ICC technique showed that osteocalcin protein is expressed at the surface of bone cells. Furthermore, the expression of APC, as a target of miR-27a-3p, decreased in transfected cells.

CONCLUSION

Our data suggest that miR-27a-3p may positively regulates adipose tissue-derived mesenchymal stem cell differentiation into bone by targeting APC and activating the Wnt/b-catenin pathway.