Subchondral bone remodelling in osteoarthritis

Wheel Running Exacerbates Joint Damage after Meniscal Injury in Mice, but Does Not Alter Gait or Physical Activity Levels

PURPOSE

Exercise and physical activity are recommended to reduce pain and improve joint function in patients with knee osteoarthritis (OA). However, exercise has dose effects, with excessive exercise accelerating OA development and sedentary behaviors also promoting OA development. Prior work evaluating exercise in preclinical models has typically used prescribed exercise regimens; however, in-cage voluntary wheel running creates opportunities to evaluate how OA progression affects self-selected physical activity levels. This study aimed to evaluate how voluntary wheel running after a surgically induced meniscal injury affects gait characteristics and joint remodeling in C57Bl/6 mice. We hypothesize that injured mice will reduce physical activity levels as OA develops after meniscal injury and will engage in wheel running to a lesser extent than the uninjured animals.

METHODS

Seventy-two C57Bl/6 mice were divided into experimental groups based on sex, lifestyle (physically active vs sedentary), and surgery (meniscal injury or sham control). Voluntary wheel running data were continuously collected throughout the study, and gait data were collected at 3, 7, 11, and 15 wk after surgery. At end point, joints were processed for histology to assess cartilage damage.

RESULTS

After meniscal injury, physically active mice showed more severe joint damage relative to sedentary mice. Nevertheless, injured mice engaged in voluntary wheel running at the same rates and distances as mice with sham surgery. In addition, physically active mice and sedentary mice both developed a limp as meniscal injury progressed, yet exercise did not further exacerbate gait changes in the physically active mice, despite worsened joint damage.

CONCLUSIONS

Taken together, these data indicate a discordance between structural joint damage and joint function. Although wheel running after meniscal injury did worsen OA-related joint damage, physical activity did not necessarily inhibit or worsen OA-related joint dysfunction or pain in mice.

Identification and Analysis of Neutrophil Extracellular Trap-Related Genes in Osteoarthritis by Bioinformatics and Experimental Verification

Background

Osteoarthritis (OA) is a common joint disease with long-term pain and dysfunction that negatively affects the quality of life of patients. Neutrophil extracellular traps (NETs), consisting of DNA, proteins and cytoplasm, are released by neutrophils and play an important role in a variety of diseases. However, the relationship between OA and NETs is unclear.

Methods

In our study, we used bioinformatics to explore the relationship between OA and NETs and the potential biological markers. GSE55235, GSE55457, GSE117999 and GSE98918 were downloaded from the Gene Expression Omnibus (GEO) database for subsequent analysis.After differential analysis of OA expression matrices, intersection with NET-related genes (NRGs) was taken to identify Differentially expressed NRGs (DE-NRGs) in OA processes. Evaluation of immune cell infiltration by ssGSEA and CIBERSORT algorithm. The GSVA method was used to analyze the activity changes of Neutrophils pathway, Neutrophil degranulation and Neutrophil granule constituents pathway.

Results

Based on RandomForest (RF), Least Absolute Shrinkage and Selection Operator (LASSO), and Support Vector Machine-Recursive Feature Elimination (SVM-RFE) learning algorithms, five core genes (CRISPLD2, IL1B, SLC25A37, MMP9, and TLR7) were identified to construct an OA-related nomogram model for predicting OA progression. ROC curve results for these genes validated the nomogram's reliability. Correlation analysis, functional enrichment, and drug predictions were performed for the core genes. TLR7 emerged as a key focus due to its high importance ranking in RF and SVM-RFE analyses. Gene Set Enrichment Analysis (GSEA) revealed a strong association between TLR7 and the Neutrophil extracellular trap pathway. Expression of core genes was demonstrated in mice OA models and human OA samples. TLR7 expression in ATDC5 cell line was significantly higher than control after TNFα induction, along with increased IL6 and MMP13.

Conclusion

TLR7 may be related to NETs and affects OA.

Low-frequency whole-body vibration can enhance cartilage degradation with slight changes in subchondral bone in mice with knee osteoarthritis and does not have any morphologic effect on normal joints

PURPOSES

To evaluate the effects of low frequency whole-body vibration (WBV) on degeneration of articular cartilage and subchondral bone in mice with destabilization of the medial meniscus (DMM)induced osteoarthritis(OA) and mice with normal knee.

METHODS

Ten-week-old C57BL/6J male mice received DMM on right knees, while the left knees performed sham operation. There were six groups: DMM, SHAM DMM, DMM+WBV,SHAM DMM+WBV, DMM+ NON-WBV and SHAM DMM+NON-WBV. After four weeks, the knees were harvested from the DMM and SHAM DMM group. The remaining groups were treated with WBV (10 Hz) or NON-WBV. Four weeks later, the knees were harvested. Genes, containing Aggrecan(Acan) and CollagenⅡ(Col2a1), Matrix Metalloproteinases 3 and 13(MMP3,13), TNFα and IL6, were measured and staining was also performed. OA was graded with OARSI scores, and tibial plateaubone volume to tissue volume ratio(BV/TV), bone surface area to bone volume ratio (BS/BV), trabecular number(Tb.N) and trabecular thickness separation(TS) between groups were analyzed.

RESULTS

Increased OARSI scores and cartilage degradation were observed after WBV. BV/TV, Tb.N and TS were not significant between the groups. Significant reductions were observed in MMP3, MMP13, Col2a1, Acan, TNFα and IL6 in the DMM+WBV compared to SHAM DMM+WBV group. BV/TV, BS/BV, Tb.N, TS and OARSI scores were not significantly changed in the left knees. IL6 expression in the SHAM DMM+WBV group was significantly increased compared with the SHAM DMM+ NON-WBV group, while Col2a1, Acan and MMP13 expression decreased.

CONCLUSION

WBV accelerated cartilage degeneration and caused slight changes in subchondral bone in a DMM-induced OA model. WBV had no morphologic effect on normal joints.

Low back pain and osteoarthritis pain: a perspective of estrogen

Low back pain (LBP) is the world's leading cause of disability and is increasing in prevalence more rapidly than any other pain condition. Intervertebral disc (IVD) degeneration and facet joint osteoarthritis (FJOA) are two common causes of LBP, and both occur more frequently in elderly women than in other populations. Moreover, osteoarthritis (OA) and OA pain, regardless of the joint, are experienced by up to twice as many women as men, and this difference is amplified during menopause. Changes in estrogen may be an important contributor to these pain states. Receptors for estrogen have been found within IVD tissue and nearby joints, highlighting the potential roles of estrogen within and surrounding the IVDs and joints. In addition, estrogen supplementation has been shown to be effective at ameliorating IVD degeneration and OA progression, indicating its potential use as a therapeutic agent for people with LBP and OA pain. This review comprehensively examines the relationship between estrogen and these pain conditions by summarizing recent preclinical and clinical findings. The potential molecular mechanisms by which estrogen may relieve LBP associated with IVD degeneration and FJOA and OA pain are discussed.

Osteoarthritis: The Most Common Joint Disease and Outcome of Sports Injury

Osteoarthritis (OA) is the most common joint disease and affects an estimated 240 million people worldwide [...].

Clinical and radiological efficacy of single-dose intra-articular high-molecular-weight hyaluronic acid in knee osteoarthritis

Context

While visco-supplementation is being used for the treatment of knee osteoarthritis (OA), the published reports vary widely in benefits afforded by this treatment. It was therefore proposed to assess the objective parameters along with subjective outcomes.

Aims

Our study assessed the radiological and clinical efficacy of single-dose high-molecular-weight intra-articular hyaluronic acid (HMW-IAHA) injection in knee OA.

Settings and Design

This interventional cohort study was conducted in a calculated sample size of 44 patients with knee OA.

Materials and Methods

Visual analog scale (VAS) and knee OA and outcome score (KOOS) were used for clinical assessment, and whole organ magnetic resonance imaging score (WORMS) for radiological assessment. The subjects were given a single dose of HMW-IAHA injection, 90 mg/3 ml, and were assessed on day 0 and day 90.

Statistical Analysis

Statistical Package for Social Sciences (SPSS) software was used.

Results

At the day 90 follow-up, there was an improvement in mean ± standard deviation values of VAS score (day 0: 8.53 ± 0.81, day 90: 5.97 ± 0.87), KOOS score (day 0: 27.33 ± 15.18, day 90: 57.26 ± 14.26), and the cartilage signal and morphology in the medial femorotibial joint (day 0: 11.02 ± 6.26 and day 90: 10.91 ± 6.22) and patellofemoral joint (day 0: 10.35 ± 4.36 and day 90: 10.28 ± 4.39) compartments. There was a decrease in synovitis score from 2.3 ± 1.61 to 1.3 ± 1.3 in the medial femorotibial joint compartment and total WORMS score (day 0: 66.57 ± 36.06, day 90: 65.14 ± 35.62).

Conclusions

A single dose of intra-articular injection with high-molecular-weight hyaluronic acid produces improvement in the clinical symptoms and quality of life as well as is effective in maintaining the articular cartilage integrity and reducing synovial inflammation.

The Role of Genetics and Epigenetic Regulation in the Pathogenesis of Osteoarthritis

Osteoarthritis (OA) is progressive disease characterised by cartilage degradation, subchondral bone remodelling and inflammation of the synovium. The disease is associated with obesity, mechanical load and age. However, multiple pro-inflammatory immune mediators regulate the expression of metalloproteinases, which take part in cartilage degradation. Furthermore, genetic factors also contribute to OA susceptibility. Recent studies have highlighted that epigenetic mechanisms may regulate the expression of OA-associated genes. This review aims to present the mechanisms of OA pathogenesis and summarise current evidence regarding the role of genetics and epigenetics in this process.

Biomechanics of Chondrocytes and Chondrons in Healthy Conditions and Osteoarthritis: A Review of the Mechanical Characterisations at the Microscale

Biomechanical studies are expanding across a variety of fields, from biomedicine to biomedical engineering. From the molecular to the system level, mechanical stimuli are crucial regulators of the development of organs and tissues, their growth and related processes such as remodelling, regeneration or disease. When dealing with cell mechanics, various experimental techniques have been developed to analyse the passive response of cells; however, cell variability and the extraction process, complex experimental procedures and different models and assumptions may affect the resulting mechanical properties. For these purposes, this review was aimed at collecting the available literature focused on experimental chondrocyte and chondron biomechanics with direct connection to their biochemical functions and activities, in order to point out important information regarding the planning of an experimental test or a comparison with the available results. In particular, this review highlighted (i) the most common experimental techniques used, (ii) the results and models adopted by different authors, (iii) a critical perspective on features that could affect the results and finally (iv) the quantification of structural and mechanical changes due to a degenerative pathology such as osteoarthritis.

Evaluation of clinical signs and magnetic resonance imaging findings in patients with temporomandibular disorders

This study assessed the relationship between clinical symptoms and magnetic resonance imaging (MRI) findings in temporomandibular disorders (TMD). A total of 324 temporomandibular joints (TMJs) from 162 patients were included. The TMJs were divided into three groups based on disc positions on MRI: normal disc position, anterior disc displacement with reduction (ADDwR), and anterior disc displacement without reduction (ADDwoR). Clinical findings included TMJ pain, TMJ noise, and maximum mouth opening (MMO). The disc configuration, disc positions, condylar morphology, and joint effusion were evaluated in proton density-weighted and T2-weighted open and closed-mouth sagittal sections. Patients comprised 135 females and 27 males, with a mean age of 37.63 ± 13.86 years. The VAS score was significantly higher in ADDwoR than in ADDwR (p = 0.007). Condylar sclerosis (β coefficient: 1.449, 95% confidence interval (CI): 0.505-2.393, p = 0.003) and condylar flattening (β coefficient: 1.024, 95% CI: 0.209-1.840, p = 0.014) had higher VAS scores than the other MRI findings in multiple regression analyses. Limited mouth opening (MO) was independently associated with ADDwoR. ADDwoR had a higher risk of having limited MO than normal disc position (odds ratio: 5.268), while there were no associations between limited MO and other MRI findings. None of the MRI findings showed significant performance in predicting TMJ noise. The convex and folded disc configuration percentages, the frequencies of osteophyte formation, and grade 3 effusion were significantly higher in the ADDwoR group. More severe clinical symptoms and a higher degree of disc deformity, osteophyte formation, and high-grade effusion were shown to be associated with ADDwoR.

Suppressing Chondrocyte Hypertrophy to Build Better Cartilage

Current clinical strategies for restoring cartilage defects do not adequately consider taking the necessary steps to prevent the formation of hypertrophic tissue at injury sites. Chondrocyte hypertrophy inevitably causes both macroscopic and microscopic level changes in cartilage, resulting in adverse long-term outcomes following attempted restoration. Repairing/restoring articular cartilage while minimizing the risk of hypertrophic neo tissue formation represents an unmet clinical challenge. Previous investigations have extensively identified and characterized the biological mechanisms that regulate cartilage hypertrophy with preclinical studies now beginning to leverage this knowledge to help build better cartilage. In this comprehensive article, we will provide a summary of these biological mechanisms and systematically review the most cutting-edge strategies for circumventing this pathological hallmark of osteoarthritis.

Changes in the Subchondral Bone, Visfatin, and Cartilage Biomarkers after Pharmacological Treatment of Experimental Osteoarthritis with Metformin and Alendronate

Subchondral bone that has intense communication with the articular cartilage might be a potential target for pharmacological treatment in the early stages of osteoarthritis (OA). Considering the emerging data about the role of adipokines in the pathogenesis of OA, the administration of drugs that influence their level is also intriguing. Metformin and alendronate were administered in mice with collagenase-induced OA (CIOA) as a monotherapy and in combination. Safranin O staining was used for the assessment of changes in subchondral bone and articular cartilage. Before and after treatment, serum levels of visfatin and biomarkers of cartilage turnover (CTX-II, MMP-13, and COMP) were assessed. In the current study, the combined administration of alendronate and metformin in mice with CIOA led to the protection against cartilage and subchondral bone damage. In mice with CIOA, metformin led to a decrease in visfatin level. In addition, treatment with metformin, alendronate, or their combination lowered the level of cartilage biomarkers (CTX-II and COMP), while the level of MMP-13 was not influenced. In conclusion, personalized combination treatment in OA according to clinical phenotype, especially in the early stages of the disease, might lead to the identification of a successful disease-modifying therapeutic protocol in OA.

Evaluation of surgical fixation methods for the implantation of melt electrowriting-reinforced hyaluronic acid hydrogel composites in porcine cartilage defects

The surgical repair of articular cartilage remains an ongoing challenge in orthopedics. Tissue engineering is a promising approach to treat cartilage defects; however, scaffolds must (i) possess the requisite material properties to support neocartilage formation, (ii) exhibit sufficient mechanical integrity for handling during implantation, and (iii) be reliably fixed within cartilage defects during surgery. In this study, we demonstrate the reinforcement of soft norbornene-modified hyaluronic acid (NorHA) hydrogels via the melt electrowriting (MEW) of polycaprolactone to fabricate composite scaffolds that support encapsulated porcine mesenchymal stromal cell (pMSC, three donors) chondrogenesis and cartilage formation and exhibit mechanical properties suitable for handling during implantation. Thereafter, acellular MEW-NorHA composites or MEW-NorHA composites with encapsulated pMSCs and precultured for 28 days were implanted in full-thickness cartilage defects in porcine knees using either bioresorbable pins or fibrin glue to assess surgical fixation methods. Fixation of composites with either biodegradable pins or fibrin glue ensured implant retention in most cases (80%); however, defects treated with pinned composites exhibited more subchondral bone remodeling and inferior cartilage repair, as evidenced by micro-computed tomography (micro-CT) and safranin O/fast green staining, respectively, when compared to defects treated with glued composites. Interestingly, no differences in repair tissue were observed between acellular and cellularized implants. Additional work is required to assess the full potential of these scaffolds for cartilage repair. However, these results suggest that future approaches for cartilage repair with MEW-reinforced hydrogels should be carefully evaluated with regard to their fixation approach for construct retention and surrounding cartilage tissue damage.

Intra-osseous plasma rich in growth factors enhances cartilage and subchondral bone regeneration in rabbits with acute full thickness chondral defects: Histological assessment

Background

Intra-articular (IA) combined with intra-osseous (IO) infiltration of plasma rich in growth factors (PRGF) have been proposed as an alternative approach to treat patients with severe osteoarthritis (OA) and subchondral bone damage. The aim of the study is to evaluate the efficacy of IO injections of PRGF to treat acute full depth chondral lesion in a rabbit model by using two histological validated scales (OARSI and ICRS II).

Methodology

A total of 40 rabbits were included in the study. A full depth chondral defect was created in the medial femoral condyle and then animals were divided into 2 groups depending on the IO treatment injected on surgery day: control group (IA injection of PRGF and IO injection of saline) and treatment group (IA combined with IO injection of PRGF). Animals were euthanized 56 and 84 days after surgery and the condyles were processed for posterior histological evaluation.

Results

Better scores were obtained in treatment group in both scoring systems at 56- and 84-days follow-up than in control group. Additionally, longer-term histological benefits have been obtained in the treatment group.

Conclusions

The results suggests that IO infiltration of PRGF enhances cartilage and subchondral bone healing more than the IA-only PRGF infiltration and provides longer-lasting beneficial effects.

Intervertebral disc degeneration and osteoarthritis: a common molecular disease spectrum

Intervertebral disc degeneration (IDD) and osteoarthritis (OA) affecting the facet joint of the spine are biomechanically interdependent, typically occur in tandem, and have considerable epidemiological and pathophysiological overlap. Historically, the distinctions between these degenerative diseases have been emphasized. Therefore, research in the two fields often occurs independently without adequate consideration of the co-dependence of the two sites, which reside within the same functional spinal unit. Emerging evidence from animal models of spine degeneration highlight the interdependence of IDD and facet joint OA, warranting a review of the parallels between these two degenerative phenomena for the benefit of both clinicians and research scientists. This Review discusses the pathophysiological aspects of IDD and OA, with an emphasis on tissue, cellular and molecular pathways of degeneration. Although the intervertebral disc and synovial facet joint are biologically distinct structures that are amenable to reductive scientific consideration, substantial overlap exists between the molecular pathways and processes of degeneration (including cartilage destruction, extracellular matrix degeneration and osteophyte formation) that occur at these sites. Thus, researchers, clinicians, advocates and policy-makers should consider viewing the burden and management of spinal degeneration holistically as part of the OA disease continuum.

Healthy and Osteoarthritis-Affected Joints Facing the Cellular Crosstalk

Osteoarthritis (OA) is a chronic, progressive, severely debilitating, and multifactorial joint disease that is recognized as the most common type of arthritis. During the last decade, it shows an incremental global rise in prevalence and incidence. The interaction between etiologic factors that mediate joint degradation has been explored in numerous studies. However, the underlying processes that induce OA remain obscure, largely due to the variety and complexity of these mechanisms. During synovial joint dysfunction, the osteochondral unit undergoes cellular phenotypic and functional alterations. At the cellular level, the synovial membrane is influenced by cartilage and subchondral bone cleavage fragments and extracellular matrix (ECM) degradation products from apoptotic and necrotic cells. These "foreign bodies" serve as danger-associated molecular patterns (DAMPs) that trigger innate immunity, eliciting and sustaining low-grade inflammation in the synovium. In this review, we explore the cellular and molecular communication networks established between the major joint compartments-the synovial membrane, cartilage, and subchondral bone of normal and OA-affected joints.

Assessment of the Impact of Physical Activity on the Musculoskeletal System in Early Degenerative Knee Joint Lesions in an Animal Model

Osteoarthritis (OA) is one of the most prevalent diseases of the osteoarticular system. Progressive destruction of joints is accompanied by development of pathological changes in the muscle tissue, i.e., weakening, atrophy, and remodelling (sarcopenia). The aim of the present study is to assess the impact of physical activity on the musculoskeletal system in an animal model of early degenerative lesions in the knee joint. The study involved 30 male Wistar rats. The animals were allocated to three subgroups of 10 animals each. Each animal from the three subgroups received sodium iodoacetate by injection into the patellar ligament of the right knee joint, whereas saline was administered through the patellar ligament in the left knee joint. The rats in the first group were stimulated to exercise on a treadmill. The animals in the second group were allowed to lead a natural lifestyle (no treadmill stimulation). In the third group, all parts of the right hind limb muscle were injected with Clostridium botulinum toxin type A. The study demonstrated that, compared to the active rats, bone density in the immobilised rats decreased, as indicated by the densitometric assessment of the whole body and the examination of rats' hind limbs and knee joints alone. This clearly evidenced the impact of physical activity on bone mineralisation. The weight of both fat and muscle tissues in the physically inactive rats was reduced. Additionally, the adipose tissue had higher weight in the entire right hind limbs, where monoiodoacetic acid was administered to the knee joint. The animal model clearly showed the importance of physical activity in the early stages of OA, as it slows down the process of joint destruction, bone atrophy, and muscle wasting, whereas physical inactivity contributes to progression of generalised changes in the musculoskeletal system.

Correlation between Bone Mineral Density and Progression of Hip Osteoarthritis in Adult Men and Women in Bulgaria-Results from a 7-Year Study

Changes in clinical presentation, radiographic progression (RP), bone mineral density (BMD), bone turnover (BT), and cartilage turnover (CT) markers were compared in two groups of patients with hip osteoarthritis (HOA) over a period of 7 years. Each group consisted of 150 patients, including a control group on standard-of-care therapy (SC) with simple analgesics and physical exercises, and a study group (SG) on standard-of-care therapy supplemented by vitamin D3 and intravenous administration of zoledronic acid (5 mg) yearly for 3 consecutive years. Patient groups were homogenized regarding the following: (1) radiographic grade (RG), including 75 patients with hip OA RG II according to the Kellgren-Lawrence grading system (K/L), and 75 with RG III on K/L; (2) radiographic model (RM), as each of the K/L grades was subdivided into three subgroups consisting of 25 patients of different RMs: atrophic ('A'), intermediate ('I'), and hypertrophic ('H'); (3) gender-equal ratio of men and women in each subgroup (Female/Male = 15/10). The following parameters were assessed: (1) clinical parameters (CP), pain at walking (WP-VAS 100 mm), functional ability (WOMAC-C), and time to total hip replacement (tTHR); (2) radiographic indicators(RI)-joint space width (JSW) and speed of joint space narrowing (JSN), changes in BMD (DXA), including proximal femur (PF-BMD), lumbar spine (LS-BMD), and total body (TB-BMD); (3) laboratory parameters (LP)-vitamin D3 levels and levels of BT/CT markers. RV were assessed every 12 months, whereas CV/LV were assessed every 6 months. Results: Cross-sectional analysis (CsA) at baseline showed statistically significant differences (SSD) at p < 0.05 in CP (WP, WOMAC-C); BMD of all sites and levels of CT/BT markers between the 'A' and 'H' RM groups in all patients. Longitudinal analysis (LtA) showed SSD (p < 0.05) between CG and SG in all CP (WP, WOMAC-C, tTHR) parameters of RP (mJSW, JSN), BMD of all sites, and levels of CT/BT markers for all 'A' models and in 30% of 'I'-RMs (those with elevated markers for BT/CT at baseline and during the observation period). Conclusion: The presence of SSD at baseline ('A' vs. 'H') supported the thesis that at least two different subgroups of HOA exist: one associated with 'A' and the other with 'H' models. D3 supplementation and the intravenous administration of bisphosphonate were the treatment strategies that slowed down RP and postponed tTHR by over 12 months in the 'A' and 'I' RM with elevated BT/CT markers.

Biochanin A protects against iron overload associated knee osteoarthritis via regulating iron levels and NRF2/System xc-/GPX4 axis

BACKGROUND

Iron homeostasis plays a positive role in articular cartilage health. Excessive iron or iron overload can induce oxidative stress damage in chondrocytes and ferroptosis cell death, advancing knee osteoarthritis (KOA). However, up to date, few effective agents treat iron overload-induced KOA (IOKOA). Chinese herbal medicine (CHM) provides abundant resources for drug selection to manage bone metabolic conditions, including osteoporosis. Biochanin A (BCA) is a novel bioactive multifunctional natural compound isolated from Huangqi, which has protective effects on bone loss. Nevertheless, the function and mechanism of BCA in treating IOKOA are still elusive.

PURPOSE

This study seeks to uncover the potential therapeutic targets and mechanisms of BCA in the management of KOA with iron accumulation.

METHODS

Iron dextrin (500 mg/kg) was intraperitoneally injected into mice to establish the iron overloaded mice model. OA was induced through surgery, and the progression was evaluated eight weeks following surgery. OA severity was evaluated with micro-CT and Safranin-O/Fast green staining in vivo. Iron deposition in the knee joint and synovium was assessed using Perl's Prussian blue staining. Ferric ammonium citrate (FAC) was then administered to primary chondrocytes to evaluate iron regulators mediated iron homeostasis. Toluidine blue staining was utilized to identify chondrocytes in vitro. The vitality of the cells was assessed using the CCK-8 test. The apoptosis rate of cells was measured using Annexin V-FITC/PI assay. The intracellular iron level was detected utilizing the calcein-AM test. Reactive oxygen species (ROS), lipid-ROS, and mitochondrial membrane potentiality were reflected via fluorescence density. Utilizing RT-qPCR and western blotting, the expression level was determined.

RESULTS

Micro-CT and histological staining of knee joints showed greater cartilage degradation and higher iron buildup detected in iron-overloaded mice. BCA can reduce iron deposition and the severity of KOA. Toluidine blue staining and the CCK-8 assay indicated that BCA could rescue chondrocytes killed by iron. Cell apoptosis rates were increased due to iron overload but improved by BCA. Further, the intracellular content of iron, ROS, and lipid-ROS was increased with ferric ammonium citrate (FAC) treatment but restored after treatment with different concentrations of BCA. JC-1 staining revealed that BCA could reduce mitochondrial damage induced by iron overload.

CONCLUSION

Iron overload was shown to promote chondrocyte ferroptosis in vivo and in vitro. Moreover, iron overload suppressed the expression of collagen II and induced MMP expression by catalyzing ROS generation with mitochondrial dysfunction. Our results showed that BCA could directly reduce intracellular iron concentration by inhibiting TfR1 and promoting FPN but also target the Nrf2/system xc-/GPX4 signaling pathway to scavenge free radicals and prevent lipid peroxidation. The results of this research indicate that BCA regulates iron homeostasis during the progression of osteoarthritis, which can open a new field of treatment for KOA.

Fire Needling Therapy of Different Frequencies versus External Diclofenac Diethylamine Emulgel for Knee Osteoarthritis: Study Protocol for a Pilot Randomized Controlled Trial

Purpose

Knee osteoarthritis (KOA) is regarded as one of the leading musculoskeletal diseases. Although the efficacy is under exploration, fire needling therapy is considered an effective alternative for KOA. This trial aims to investigate the effectiveness of different frequencies of fire needling therapy in attenuating pain and promoting function in KOA patients.

Methods

This is a study protocol for a pilot, three-arm, single-center, randomized controlled trial. A total of 90 participants with KOA will be recruited and randomly assigned to the high-frequency fire needling group (3 sessions per week, for 6 weeks), the low-frequency fire needling group (1 session per week, for 6 weeks) or the positive control group (Diclofenac Diethylamine Emulgel, 3 times per day, for 6 weeks) in a 1:1:1 ratio. Participants will accomplish the trial at Week 14 after a follow-up evaluation. The response rate will be set as the primary outcome that the proportion of participants obtaining a minimal clinically important difference, which is identified as ≥2 units on the numerical rating scale (NRS) and ≥6 units on the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) function score at Week 6 compared with Week 0. Secondary outcomes are NRS, WOMAC, Brief Pain Inventory, Short-Form Health Survey-12, Timed Up and Go Test, and pain threshold.

Discussion

This is the first standardized protocol comparing fire needling therapy and positive control drugs. This trial may provide reliable evidence for the effectiveness of fire needling therapy and dose-effect property of it in KOA. Trial registration: The trial has been registered on Chinese Clinical Trial Registry (Registered number: ChiCTR2100043041), registered on 4 February 2021.

Novel micro-MRI approach for subchondral trabecular bone analysis in patients with hip osteoarthritis is comparable to micro-CT approach

AIM

To test the agreement between a newly developed micro-magnetic resonance imaging (MRI) analysis of the subchondral bone and the micro-computed tomography (CT) approach.

METHODS

Samples obtained from 10 patients with osteoarthritis undergoing total hip arthroplasty were scanned with a 7.0 T micro-MRI. Proton density-weighted images and proton density-weighted images with fat suppression were obtained. The results were validated with a micro-CT device. Micro-MRI and micro-CT scans of the same sample were aligned, and regions of interest were delineated on equal areas of the sample. Bone volume fraction was calculated by using in-house plugins. The agreement between the methods was tested with Bland-Altman analysis.

RESULTS

The agreement between the methods was good, with average difference of 2.167%. The differences between the methods were not significant (P=0.272, t test).

CONCLUSION

The novel micro-MRI approach could be used for subchondral bone analysis. With further optimization for clinical MRI machines, the approach can be also used in the diagnostics of hip osteoarthritis.

Can guided wave ultrasound predict bone mechanical properties at the femoral neck in patients undergoing hip arthroplasty?

The bone quality of patients undergoing hip replacement surgery is poorly predicted by radiographs alone. With better bone quality information available to a surgeon, the operation can be performed more safely. The aim of this study was to investigate whether ultrasound signals of cortical bone at peripheral sites such as the tibia and radius can be used to predict the compressive mechanical properties of cortical bone at the femoral neck. We recruited 19 patients undergoing elective hip arthroplasty and assessed the radius and tibia of these patients with the Azalée guided wave ultrasound to estimate the porosity and thickness of the cortex. Excess bone tissues were collected from the femoral neck and the compressive mechanical properties of the cortex were characterised under a mechanical loading rig to determine stiffness, ultimate strength, and density. The correlations between the ultrasound measurements and mechanical properties were analysed using linear regression, Pearson correlation statistics, and multiple regression analysis. Cortical mechanical properties were weakly to moderately correlated with the ultrasound measurements at various sites (R2 = 0.00-0.36). The significant correlations found were not consistent across all 4 peripheral measurement sites. Additionally, weak to moderate ability of the ultrasound to predict mechanical properties at the neck of femur with multiple regression analysis was found (R2 = 0.00-0.48). Again, this was inconsistent across the different anatomical sites. Overall, the results demonstrate the need for ultrasound scans to be collected directly from clinically relevant sites such as the femoral neck due to the inconsistency of mechanical properties across various sites.

Novel micro-MRI approach for subchondral trabecular bone analysis in patients with hip osteoarthritis is comparable to micro-CT approach

AIM

To test the agreement between a newly developed micro-magnetic resonance imaging (MRI) analysis of the subchondral bone and the micro-computed tomography (CT) approach.

METHODS

Samples obtained from 10 patients with osteoarthritis undergoing total hip arthroplasty were scanned with a 7.0 T micro-MRI. Proton density-weighted images and proton density-weighted images with fat suppression were obtained. The results were validated with a micro-CT device. Micro-MRI and micro-CT scans of the same sample were aligned, and regions of interest were delineated on equal areas of the sample. Bone volume fraction was calculated by using in-house plugins. The agreement between the methods was tested with Bland-Altman analysis.

RESULTS

The agreement between the methods was good, with average difference of 2.167%. The differences between the methods were not significant (P=0.272, t test).

CONCLUSION

The novel micro-MRI approach could be used for subchondral bone analysis. With further optimization for clinical MRI machines, the approach can be also used in the diagnostics of hip osteoarthritis.

Proteomic Analyses Reveals the Mechanism of Acupotomy Intervention on the Treatment of Knee Osteoarthritis in Rabbits

Acupotomy intervention (AI) is an available treatment for knee osteoarthritis (KOA) in China, which is a common health problem over the world. However, the underlying mechanism of AI on the KOA treatment is still unknown. To further understand the mechanism of acupotomy in treating KOA, the morphological observation and TMT proteomic analyses were conducted in rabbits. By using X-ray and MRI, we found that the space of the knee joint was bigger in AI than in KOA. Moreover, the chondrocytes were neatly arranged in AI but disordered in KOA. With proteomic analyses in chondrocytes, 68 differently accumulated proteins (DAPs) were identified in AI vs. KOA and DAPs related to energy metabolism and the TCA cycle were suggested to play a central role in response to AI. Furthermore, AIFM1 was proposed to be an important regulator in controlling the energy production in mitochondrial. Besides, FN1, VIM, COL12A1, COL14A1, MYBPH, and DPYSL3 were suggested to play crucial roles in AI for the treatment of KOA. Our study was systematically elucidating the regulation mechanism of acupotomy intervention in the treatment of KOA.

Increased joint loading induces subchondral bone loss of the temporomandibular joint via the RANTES-CCRs-Akt2 axis

Early-stage temporomandibular joint osteoarthritis (TMJOA) is characterized by excessive subchondral bone loss. Emerging evidence suggests that TMJ disc displacement is involved, but the pathogenic mechanism remains unclear. Here, we established a rat model of TMJOA that simulated disc displacement with a capacitance-based force-sensing system to directly measure articular surface pressure in vivo. Micro-CT, histological staining, immunofluorescence staining, IHC staining, and Western blot were used to assess pathological changes and underlying mechanisms of TMJOA in the rat model in vivo as well as in RAW264.7 cells in vitro. We found that disc displacement led to significantly higher pressure on the articular surface, which caused rapid subchondral bone loss via activation of the RANTES-chemokine receptors-Akt2 (RANTES-CCRs-Akt2) axis. Inhibition of RANTES or Akt2 attenuated subchondral bone loss and resulted in improved subchondral bone microstructure. Cytological studies substantiated that RANTES regulated osteoclast formation by binding to its receptor CCRs and activating the Akt2 pathway. The clinical evidence further supported that RANTES was a potential biomarker for predicting subchondral bone loss in early-stage TMJOA. Taken together, this study demonstrates important functions of the RANTES-CCRs-Akt2 axis in the regulation of subchondral bone remodeling and provides further knowledge of how disc displacement causes TMJOA.

Osteoarthritis: New Insight on Its Pathophysiology

Understanding of the basis of osteoarthritis (OA) has seen some interesting advancements in recent years. It has been observed that cartilage degeneration is preceded by subchondral bone lesions, suggesting a key role of this mechanism within the pathogenesis and progression of OA, as well as the formation of ectopic bone and osteophytes. Moreover, low-grade, chronic inflammation of the synovial lining has gained a central role in the definition of OA physiopathology, and central immunological mechanisms, innate but also adaptive, are now considered crucial in driving inflammation and tissue destruction. In addition, the role of neuroinflammation and central sensitization mechanisms as underlying causes of pain chronicity has been characterized. This has led to a renewed definition of OA, which is now intended as a complex multifactorial joint pathology caused by inflammatory and metabolic factors underlying joint damage. Since this evidence can directly affect the definition of the correct therapeutic approach to OA, an improved understanding of these pathophysiological mechanisms is fundamental. To this aim, this review provides an overview of the most updated evidence on OA pathogenesis; it presents the most recent insights on the pathophysiology of OA, describing the interplay between immunological and biochemical mechanisms proposed to drive inflammation and tissue destruction, as well as central sensitization mechanisms. Moreover, although the therapeutic implications consequent to the renewed definition of OA are beyond this review scope, some suggestions for intervention have been addressed.

Prospective double-blind randomised controlled trial protocol comparing bone marrow aspirate concentrate intra-articular injection combined with subchondral injection versus intra-articular injection alone for the treatment of symptomatic knee osteoarthritis

INTRODUCTION

Subchondral and intra-articular injections of bone marrow aspirate concentrate (BMAC) showed promising results for knee osteoarthritis (OA) patients. To date, there is no evidence to demonstrate whether the combination of these treatments provides higher benefits than the intra-articular injection alone.

METHODS AND ANALYSIS

Eighty-six patients with symptomatic knee OA (aged between 40 and 70 years) are randomised to BMAC intra-articular injection combined with subchondral BMAC injection or BMAC intra-articular injection alone in a ratio of 1:1. The primary outcome is the total Western Ontario and McMaster Universities Osteoarthritis Index, the secondary outcomes are the International Knee Documentation Committee Subjective and Objective Knee Evaluation Form, the Tegner activity scale, the EuroQol-Visual Analogue Scale, and the health questionnaire European Quality of Life Five Dimension score. Additional CT and MRI evaluations are performed at the baseline assessment and at the final 12-month follow-up. The hypothesis is that the combined injections provide higher knee pain and function improvement compared with BMAC intra-articular injection alone. The primary analysis follows an intention to treat principle.

ETHICS AND DISSEMINATION

The study protocol has been approved by the Emilia Wide Area Ethical Committee of the Emilia-Romagna Region (CE-AVEC), Bologna, Italy. Written informed consent is obtained from all the participants. Findings of this study will be disseminated through peer-reviewed publications and conference presentations.

PROTOCOL VERSION

Version 1 (14 May 2018).

TRIAL REGISTRATION NUMBER

NCT03876795.

Dynamic Postural Stability after Cartilage Repair in the Knee

Background:

Articular cartilage has an exceptionally poor capacity for healing, but Autologous Matrix Induced Chondrogenesis is a procedure with a substantial body of literature that demonstrates its performance in chondral and osteochondral repair. However, data concerning dynamic postural stability after cartilage repair procedures is lacking.

Objective:

Therefore, the present study was designed to assess postural stability following cartilage repair in the knee.

Methods:

20 adults had undergone Autologous Matrix Induced Chondrogenesis for the treatment of full-thickness cartilage defects, with minimum 36 months of follow-up. Clinical outcomes were evaluated by patient reported outcome measures while dynamic postural stability was assessed using the star excursion balance test. The untreated, contralateral limbs served as controls.

Results:

At a mean follow-up of 43 months, patients reported a Visual Analog Score for pain of 1.6±2.2, a mean Lysholm score of 78.5±17.9 and a mean Knee Osteoarthritis Outcome Score of 143.3±16.1. The star excursion balance test showed no significant difference between limbs.

Conclusion:

With no difference in dynamic postural stability, our results indicate that this treatment provides a positive clinical outcome, with no deficits in postural stability when compared to the contralateral, untreated leg.

Phenotype-Genotype analysis of caucasian patients with high risk of osteoarthritis

Background: Osteoarthritis (OA) is a common cause of disability and pain around the world. Epidemiologic studies of family history have revealed evidence of genetic influence on OA. Although many efforts have been devoted to exploring genetic biomarkers, the mechanism behind this complex disease remains unclear. The identified genetic risk variants only explain a small proportion of the disease phenotype. Traditional genome-wide association study (GWAS) focuses on radiographic evidence of OA and excludes sex chromosome information in the analysis. However, gender differences in OA are multifactorial, with a higher frequency in women, indicating that the chromosome X plays an essential role in OA pathology. Furthermore, the prevalence of comorbidities among patients with OA is high, indicating multiple diseases share a similar genetic susceptibility to OA. Methods: In this study, we performed GWAS of OA and OA-associated key comorbidities on 3366 OA patient data obtained from the Osteoarthritis Initiative (OAI). We performed Mendelian randomization to identify the possible causal relationship between OA and OA-related clinical features. Results: One significant OA-associated locus rs2305570 was identified through sex-specific genome-wide association. By calculating the LD score, we found OA is positively correlated with heart disease and stroke. A strong genetic correlation was observed between knee OA and inflammatory disease, including eczema, multiple sclerosis, and Crohn's disease. Our study also found that knee alignment is one of the major risk factors in OA development, and we surprisingly found knee pain is not a causative factor of OA, although it was the most common symptom of OA. Conclusion: We investigated several significant positive/negative genetic correlations between OA and common chronic diseases, suggesting substantial genetic overlaps between OA and these traits. The sex-specific association analysis supports the critical role of chromosome X in OA development in females.

Exercise-induced modulation of myokine irisin in bone and cartilage tissue—Positive effects on osteoarthritis: A narrative review

Osteoarthritis is a chronic degenerative musculoskeletal disease characterized by pathological changes in joint structures along with the incidence of which increases with age. Exercise is recommended for all clinical treatment guidelines of osteoarthritis, but the exact molecular mechanisms are still unknown. Irisin is a newly discovered myokine released mainly by skeletal muscle in recent years—a biologically active protein capable of being released into the bloodstream as an endocrine factor, the synthesis and secretion of which is specifically induced by exercise-induced muscle contraction. Although the discovery of irisin is relatively recent, its role in affecting bone density and cartilage homeostasis has been reported. Here, we review the production and structural characteristics of irisin and discuss the effects of the different types of exercise involved in the current study on irisin and the role of irisin in anti-aging. In addition, the role of irisin in the regulation of bone mineral density, bone metabolism, and its role in chondrocyte homeostasis and metabolism is reviewed. A series of studies on irisin have provided new insights into the mechanisms of exercise training in improving bone density, resisting cartilage degeneration, and maintaining the overall environmental homeostasis of the joint. These studies further contribute to the understanding of the role of exercise in the fight against osteoarthritis and will provide an important reference and aid in the development of the field of osteoarthritis prevention and treatment.

Monosodium iodoacetate-induced subchondral bone microstructure and inflammatory changes in an animal model of osteoarthritis

The monosodium iodoacetate (MIA)-induced osteoarthritis (OA) may lead to cartilage degeneration and histopathological lesions. However, the correlation between inflammatory reaction and subchondral bone remodeling in a rodent osteoarthritic model is ambiguous. In this study, intra-articular injection of MIA was performed in 36 four-week-old specific pathogen-free male Wistar rats to induce OA. After 4 weeks of intervention, changes in intrinsic structural properties of the subchondral bones were measured, and the histological evaluation, as well as biochemical analysis, was conducted. We found that intra-articular injection of MIA increased chondrocyte apoptosis and promoted cartilage matrix degradation, such as cartilage surface defects and shallow or disappearing staining. MIA also induced inflammation, improved the expression of IL-1β, TNF-α, and matrix metalloproteinase, and decreased the expression of cartilage-specific proteins with the extension of modeling time. Meanwhile, the MIA also significantly accelerated the subchondral bone remodeling, as shown by the decreased subchondral bone density, thinning of trabeculae, disordered cartilage structure, and morphology. In conclusion, we have shown that MIA-induced rodent osteoarthritic model would cause decreased subchondral bone density, sparse trabecular bone, and other manifestations of osteoporosis accompanied by an inflammatory response, which would worsen with the progression of modeling time. Our results suggest that different phases of MIA-induced OA are associated with the changes in subchondral bone microstructure and the progression of local inflammation.

The Involvement of Neutrophils in the Pathophysiology and Treatment of Osteoarthritis

Osteoarthritis (OA) is a chronic disability that significantly impairs quality of life. OA is one of the most prevalent joint pathologies in the world, characterized by joint pain and stiffness due to the degeneration of articular cartilage and the remodeling of subchondral bone. OA pathogenesis is unique in that it involves simultaneous reparative and degradative mechanisms. Low-grade inflammation as opposed to high-grade allows for this coexistence. Previously, macrophages and T cells have been identified as playing major roles in the inflammation and destruction of OA joints, but recent studies have demonstrated that neutrophils also contribute to the pathogenesis. Neutrophils are the first immune cells to enter the synovium after joint injury, and neutrophilic activity is indispensably a requisite for the progression of OA. Neutrophils act through multiple mechanisms including tissue degeneration via neutrophil elastase (NE), osteophyte development, and the release of inflammatory cytokines and chemokines. As the actions of neutrophils in OA are discovered, the potential for novel therapeutic targets as well as diagnostic methods are revealed. The use of chondrogenic progenitor cells (CPCs), microRNAs, and exosomes are among the newest therapeutic advances in OA treatment, and this review reveals how they can be used to mitigate destructive neutrophil activity.

Subchondral bone changes after joint distraction treatment for end stage knee osteoarthritis

OBJECTIVE

Increased subchondral cortical bone plate thickness and trabecular bone density are characteristic of knee osteoarthritis (OA). Knee joint distraction (KJD) is a joint-preserving knee OA treatment where the joint is temporarily unloaded. It has previously shown clinical improvement and cartilage regeneration, indicating reversal of OA-related changes. The purpose of this research was to explore 3D subchondral bone changes after KJD treatment using CT imaging.

DESIGN

Twenty patients were treated with KJD and included to undergo knee CT imaging before, one, and two years after treatment. Tibia and femur segmentation and registration to canonical surfaces were performed semi-automatically. Cortical bone thickness and trabecular bone density were determined using an automated algorithm. Statistical parametric mapping (SPM) with two-tailed F-tests was used to analyze whole-joint changes.

RESULTS

Data was available of 16 patients. Subchondral cortical bone plate thickness and trabecular bone density were higher in the weight-bearing region of the most affected compartment (MAC; mostly medial). Especially the MAC showed a decrease in thickness and density in the first year after treatment, which was sustained towards the second year.

CONCLUSIONS

KJD treatment results in bone changes that include thinning of the subchondral cortical bone plate and decrease of subchondral trabecular bone density in the first two years after treatment, potentially indicating a partial normalization of subchondral bone.

Source and hub of inflammation: The infrapatellar fat pad and its interactions with articular tissues during knee osteoarthritis

Knee osteoarthritis, the most prevalent degenerative joint disorder worldwide, is driven by chronic low-grade inflammation and subsequent cartilage degradation. Clinical data on the role of the Hoffa or infrapatellar fat pad in knee osteoarthritis are, however, scarce. The infrapatellar fat pad is a richly innervated intracapsular, extrasynovial adipose tissue, and an abundant source of adipokines and proinflammatory and catabolic cytokines, which may contribute to chronic synovial inflammation, cartilage destruction, and subchondral bone remodeling during knee osteoarthritis. How the infrapatellar fat pad interacts with neighboring tissues is poorly understood. Here, we review available literature with regard to the infrapatellar fat pad's interactions with cartilage, synovium, bone, menisci, ligaments, and nervous tissue during the development and progression of knee osteoarthritis. Signaling cascades are described with a focus on immune cell populations, pro- and anti-inflammatory cytokines, adipokines, mesenchymal stromal cells, and molecules derived from conditioned media from the infrapatellar fat pad. Understanding the complex interplay between the infrapatellar fat pad and its neighboring articular tissues may help to better understand and treat the multifactorial pathogenesis of osteoarthritis.

In vitro Exposure to Inflammatory Mediators Affects the Differentiation of Mesenchymal Progenitors

The increasing prevalence of joint disease, and in particular osteoarthritis (OA), calls for novel treatment strategies to prevent disease progression in addition to existing approaches focusing mainly on the relief of pain symptoms. The inherent properties of mesenchymal stem cells (MSCs) make them an attractive candidate for novel tissue repair strategies, as these progenitors have the potential to differentiate into chondrocytes needed to replace degraded cartilage and can exert a modulating effect on the inflammatory environment of the diseased joint. However, the inflammatory environment of the joint may affect the ability of these cells to functionally integrate into the host tissue and exert beneficial effects, as hinted by a lack of success seen in clinical trials. Identification of factors and cell signalling pathways that influence MSC function is therefore critical for ensuring their success in the clinic, and here the effects of inflammatory mediators on bone marrow-derived MSCs were evaluated. Human MSCs were cultured in the presence of inflammatory mediators typically associated with OA pathology (IL-1β, IL-8, IL-10). While exposure to these factors did not produce marked effects on MSC proliferation, changes were observed when the mediators were added under differentiating conditions. Results collected over 21 days showed that exposure to IL-1β significantly affected the differentiation response of these cells exposed to chondrogenic and osteogenic conditions, with gene expression analysis indicating changes in MAPK, Wnt and TLR signalling pathways, alongside an increased expression of pro-inflammatory cytokines and cartilage degrading enzymes. These results highlight the value of MSCs as a preclinical model to study OA and provide a basis to define the impact of factors driving OA pathology on the therapeutic potential of MSCs for novel OA treatments.

Diterbutyl phthalate attenuates osteoarthritis in ACLT mice via suppressing ERK/c-fos/NFATc1 pathway, and subsequently inhibiting subchondral osteoclast fusion

Osteoarthritis (OA) is the most common arthritis with a rapidly increasing prevalence. Disease progression is irreversible, and there is no curative therapy available. During OA onset, abnormal mechanical loading leads to excessive osteoclastogenesis and bone resorption in subchondral bone, causing a rapid subchondral bone turnover, cyst formation, sclerosis, and finally, articular cartilage degeneration. Moreover, osteoclast-mediated angiogenesis and sensory innervation in subchondral bone result in abnormal vascularization and OA pain. The traditional Chinese medicine Panax notoginseng (PN; Sanqi) has long been used in treatment of bone diseases including osteoporosis, bone fracture, and OA. In this study we established two-dimensional/bone marrow mononuclear cell/cell membrane chromatography/time of flight mass spectrometry (2D/BMMC/CMC/TOFMS) technique and discovered that diterbutyl phthalate (DP) was the active constituent in PN inhibiting osteoclastogenesis. Then we explored the therapeutic effect of DP in an OA mouse model with anterior cruciate ligament transaction (ACLT). After ACLT was conducted, the mice received DP (5 mg·kg^-1·d^-1, ip) for 8 weeks. Whole knee joint tissues of the right limb were harvested at weeks 2, 4, and 8 for analysis. We showed that DP administration impeded overactivated osteoclastogenesis in subchondral bone and ameliorated articular cartilage deterioration. DP administration blunted aberrant H-type vessel formation in subchondral bone marrow and alleviated OA pain assessed in Von Frey test and thermal plantar test. In RANKL-induced RAW264.7 cells in vitro, DP (20 μM) retarded osteoclastogenesis by suppressing osteoclast fusion through inhibition of the ERK/c-fos/NFATc1 pathway. DP treatment also downregulated the expression of dendritic cell-specific transmembrane protein (DC-STAMP) and d2 isoform of the vacuolar (H+) ATPase V0 domain (Atp6v0d2) in the cells. In conclusion, we demonstrate that DP prevents OA progression by inhibiting abnormal osteoclastogenesis and associated angiogenesis and neurogenesis in subchondral bone.

Subchondral versus intra-articular orthobiologic injections for the treatment of knee osteoarthritis: a review

Recent perspectives suggest that osteoarthritis (OA) is a disease involving not only the articular cartilage but also the osteochondral unit, including the synovium, supportive cartilage and subchondral bone. Current conservative treatments for OA are symptomatic and do not prevent progression or reverse the disease process. Compelling data show that intra-articular orthobiologic injections, such as platelet-rich plasma and mesenchymal stromal cells, are effective in providing relief of OA symptoms. However, recent data suggest that injections of orthobiologics into the subchondral bone may be superior to intra-articular injections for the management of OA. This review highlights the rationale and current evidence for intra-articular and subchondral bone injections of orthobiologics for the treatment of OA.

Alterations of the Subchondral Bone in Osteoarthritis: Complying with Wolff's law

Osteoarthritis (OA) is a whole joint disease that is significantly related to abnormal mechanical loads. Subchondral bone alterations, during the evolution course of OA, are considered as a reflection of adaptation of the bone tissue to mechanical loads. However, some of these alterations are taken as detriment and paradoxical. What are these structure, composition, and mechanical property alterations or mechanical functions for are not quite clear. In this review, we evaluate the possibility that these alterations are used for maintaining joint function. With taking excessive load as a risk factor and under conditions of articular cartilage gradually loss its thickness and its function of evenly distributing load on subchondral bone plate, and applying poroelasticity. Moreover, Boussinesq's pressure bulb theory and bone optimal design principles are utilized for bone mechanics. We found that each subchondral bone alteration has its unique mechanical function in resisting loads and maintaining joint function, and these alterations comply with both bone optimal design principles and Wolff's law within a proper range.

β2-Adrenoceptor Deficiency Results in Increased Calcified Cartilage Thickness and Subchondral Bone Remodeling in Murine Experimental Osteoarthritis

Purpose

Recent studies demonstrated a contribution of adrenoceptors (ARs) to osteoarthritis (OA) pathogenesis. Several AR subtypes are expressed in joint tissues and the β2-AR subtype seems to play a major role during OA progression. However, the importance of β2-AR has not yet been investigated in knee OA. Therefore, we examined the development of knee OA in β2-AR-deficient (Adrb2^-/-) mice after surgical OA induction.

Methods

OA was induced by destabilization of the medial meniscus (DMM) in male wildtype (WT) and Adrb2^-/- mice. Cartilage degeneration and synovial inflammation were evaluated by histological scoring. Subchondral bone remodeling was analyzed using micro-CT. Osteoblast (alkaline phosphatase - ALP) and osteoclast (cathepsin K - CatK) activity were analyzed by immunostainings. To evaluate β2-AR deficiency-associated effects, body weight, sympathetic tone (splenic norepinephrine (NE) via HPLC) and serum leptin levels (ELISA) were determined. Expression of the second major AR, the α2-AR, was analyzed in joint tissues by immunostaining.

Results

WT and Adrb2^-/- DMM mice developed comparable changes in cartilage degeneration and synovial inflammation. Adrb2^-/- DMM mice displayed elevated calcified cartilage and subchondral bone plate thickness as well as increased epiphyseal BV/TV compared to WTs, while there were no significant differences in Sham animals. In the subchondral bone of Adrb2^-/- mice, osteoblasts activity increased and osteoclast activity deceased. Adrb2^-/- mice had significantly higher body weight and fat mass compared to WT mice. Serum leptin levels increased in Adrb2^-/- DMM compared to WT DMM without any difference between the respective Shams. There was no difference in the development of meniscal ossicles and osteophytes or in the subarticular trabecular microstructure between Adrb2^-/- and WT DMM as well as Adrb2^-/- and WT Sham mice. Number of α2-AR-positive cells was lower in Adrb2^-/- than in WT mice in all analyzed tissues and decreased in both Adrb2^-/- and WT over time.

Conclusion

We propose that the increased bone mass in Adrb2^-/- DMM mice was not only due to β2-AR deficiency but to a synergistic effect of OA and elevated leptin concentrations. Taken together, β2-AR plays a major role in OA-related subchondral bone remodeling and is thus an attractive target for the exploration of novel therapeutic avenues.

IκB-ζ signaling promotes chondrocyte inflammatory phenotype, senescence, and erosive joint pathology

Osteoarthritis is a joint disease characterized by a poorly-defined inflammatory response that does not encompass a massive immune cell infiltration yet contributes to cartilage degradation and loss of joint mobility, suggesting a chondrocyte intrinsic inflammatory response. Using primary chondrocytes from joints of osteoarthritic mice and patients, we first show that these cells express ample pro-inflammatory markers and RANKL in an NF-κB dependent manner. The inflammatory phenotype of chondrocytes was recapitulated by exposure of chondrocytes to IL-1β and bone particles, which were used to model bone matrix breakdown products revealed to be present in synovial fluid of OA patients, albeit their role was not defined. We further show that bone particles and IL-1β can promote senescent and apoptotic changes in primary chondrocytes due to oxidative stress from various cellular sources such as the mitochondria. Finally, we provide evidence that inflammation, oxidative stress and senescence converge upon IκB-ζ, the principal mediator downstream of NF-κB, which regulates expression of RANKL, inflammatory, catabolic, and SASP genes. Overall, this work highlights the capacity and mechanisms by which inflammatory cues, primarily joint degradation products, i.e., bone matrix particles in concert with IL-1β in the joint microenvironment, program chondrocytes into an "inflammatory phenotype" which inflects local tissue damage.

Osteoclasts secrete leukemia inhibitory factor to promote abnormal bone remodeling of subchondral bone in osteoarthritis

BACKGROUND

Osteoarthritis (OA) is a common chronic degenerative joint disease. At present, there is no effective treatment to check the progression of osteoarthritis. Osteochondral units are considered to be one of the most important structures affecting the occurrence and development of osteoarthritis. Osteoclasts mediate an increase in abnormal bone remodeling in subchondral bone in the early stage of osteoarthritis. Here, alendronate (ALN) that inhibit osteoclasts was used to study the regulatory effect of osteoclast-derived leukemia inhibitory factor (LIF) on early abnormal bone remodeling.

METHODS

This study involved 10-week-old wild-type female C57BL/6 mice and female SOST knockout (KO) mice that were divided into the sham, vehicle, ALN, and SOST KO groups.

RESULTS

The expression of LIF was found to decrease by inhibiting osteoclasts, and the histological OA score suggested that the degeneration of articular cartilage was attenuated. Additionally, micro-CT showed that osteoclasts inhibited in the early stage of OA could maintain the microstructure of the subchondral bone. The parameters of bone volume fraction (BV/TV), subchondral bone plate thickness (SBP.Th), and trabecular separation (Tb.Sp) of the treated group were better than those of the vehicle group.

CONCLUSIONS

These results suggested that downregulating the expression of sclerostin in osteocytes by secreting LIF from osteoclasts, activate the Wnt/β-catenin signaling pathway, and promote abnormal bone remodeling in OA. Therefore, clastokine LIF might be a potential molecular target to promote abnormal bone remodeling in early OA.

Post-traumatic Osteoarthritis in Rabbits Following Traumatic Injury and Surgical Reconstruction of the Knee

Post-traumatic osteoarthritis (PTOA) of the knee is often attributed to anterior cruciate ligament (ACL) and meniscus injury. The development of PTOA, however, does not seem to depend on whether or not the damaged ACL is reconstructed. There has been a need to develop animal models to study the mechanisms of PTOA following reconstruction of a traumatized knee. Eighteen rabbits underwent closed-joint trauma to produce ACL rupture and meniscus damage. Then, for the first time, the traumatized knee was surgically repaired in this animal model. Upon euthanasia at 1-, 3- or 6-month post-trauma, joint stability, cartilage morphology and mechanical properties, as well as histology of the cartilage and subchondral bone were evaluated. Trauma-induced knee injury involved 72% mid-substance ACL rupture, 28% partial ACL tear and 56% concurrent medial meniscal damage. ACL reconstruction effectively restored joint stability by reducing joint laxity to a level similar to that in the contralateral intact knee. Compared to their contralateral controls, reconstructed limbs showed osteoarthritic changes to the cartilage and subchondral bone as early as 1-month post-trauma. The degeneration progressed over time up to 6-month. Overall, the medial compartments had more tissue damage than their corresponding lateral counterparts. Damage patterns to the ACL, the frequency of observed concurrent meniscal injury, and reductions in cartilage integrity and health were consistent with clinical observations of human patients who undergo ACL injury and reconstruction. Thus, we believe the combined closed-joint injury and surgical repair lapine model of PTOA, being first-ever and clinically relevant, shows promise to evaluate well-targeted therapeutics and other interventions for this chronic disease.

Variation characteristics of stress distribution in the subchondral bone of the knee joint of judo athletes with long-term stress changes

OBJECTIVE

To investigate the distribution of bone density in the subchondral bone tissue of the knee joint due to the mechanical stress load generated by judo, the bone tissue volume of different densities and the bone remodeling characteristics of the subchondral bone of the knee joint.

METHODS

CT imaging data of the knee joint were collected from 15 healthy individuals as controls and 15 elite judo athletes. Firstly, they were processed by the CTOAM technique, and secondly, the distribution pattern of high-density areas of the knee joint was localized using nine anatomical regions. In addition, three tomographic images were selected in the sagittal, coronal, and axial 2D image windows to observe the distribution of different densities of bone tissue. Finally, the percentage of bone tissue volume (%BTV) and bone remodeling trend of bone tissues with different densities were determined.

RESULTS

In this study, high-density areas were found in the 4th, 5th, and 6th regions of the articular surface of the distal femur and the 1st, 2nd, 3rd, 4th, 5th, 6th, 7th and 8th regions of the tibial plateau in judo athletes; the distribution of high-density areas on the articular surface of the distal femur in control subjects was similar with judo athletes, and high-density areas were mainly found in the 4th and 5th regions of the tibial plateau. The %BTV of low (401-500HU in the distal femur; 301-400 HU and 401-500HU in the tibial plateau), moderate, and high bone density was higher in judo athletes than in controls in the subchondral bone of the distal femur and tibial plateau (P< 0.05).

CONCLUSION

The history of compressive stresses, struck stresses, soft tissue tension and pull, self-gravity and intra-articular stress loading generated by the lower limb exercise technique of judo leads to specific forms of stress distribution and bone tissue remodeling in the subchondral bone tissue within the distal femur and tibia plateau.

Hemp Seeds in Post-Arthroplasty Rehabilitation: A Pilot Clinical Study and an In Vitro Investigation

Osteoarthritis is a type of degenerative joint disease that results from the breakdown of joint cartilage and underlying bone. Due to their antioxidants and anti-inflammatory action, the phytochemical constituents of many vegetable varieties could represent a new frontier for the treatment of patients with Osteoarthritis and are still being explored. The aim of this pilot human study was to investigate the effects of pasta enriched with hemp seed flour on osteoarticular pain and bone formation markers in patients in post-arthroplasty rehabilitation. Another purpose was to evaluate the effect of hemp seed extract on bone metabolism, in vitro. A pilot, controlled, clinical study was conducted to verify the feasibility of pain symptom reduction in patients with Osteoarthritis undergoing arthroplasty surgery. We also investigated the effect of hemp seed extract on the Wnt/β-catenin and ERK1/2 pathways, alkaline phosphatase, RANKL, RUNX-2, osteocalcin, and COL1A on Saos-2. After 6 weeks, the consumption of hemp seed pasta led to greater pain relief compared to the regular pasta control group (−2.9 ± 1.3 cm vs. −1.3 ± 1.3 cm; p = 0.02). A significant reduction in serum BALP was observed in the participants consuming the hemp seed pasta compared to control group (−2.8 ± 3.2 µg/L vs. 1.1 ± 4.3 µg/L; p = 0.04). In the Saos-2 cell line, hemp seed extract also upregulated Wnt/β-catenin and Erk1/2 pathways (p = 0.02 and p = 0.03) and osteoblast differentiation markers (e.g., ALP, OC, RUNX2, and COL1A) and downregulated RANKL (p = 0.02), compared to the control. Our study demonstrated that hemp seed can improve pain symptoms in patients with osteoarthritis undergoing arthroplasty surgery and also improves bone metabolism both in humans and in vitro. However, more clinical studies are needed to confirm our preliminary findings.

Aberrant Fluid Shear Stress Contributes to Articular Cartilage Pathogenesis via Epigenetic Regulation of ZBTB20 by H3K4me3

Purpose

Osteoarthritis (OA) is a common disease for human beings, characterized by severe inflammation, cartilage degradation, and subchondral bone destruction. However, current therapies are limited to relieving pain or joint replacement and no effective treatment methods have been discovered to improve degenerative changes. Currently, a variety of evidences have indicated that aberrant mechanical stimuli is closely associated with articular joint pathogenesis, while the detailed underlying mechanism remains unelucidated. In the present study, we determined to investigate the impact of excessive high fluid shear stress (FSS) on primary chondrocytes and the underlying epigenetic mechanisms.

Materials and Methods

Phalloidin staining and EdU staining were used to evaluate cell morphology and viability. The mRNA level and protein level of genes were determined by qPCR, Western blot assay, and immunofluorescence staining. Mechanistic investigation was performed through RNA-sequencing and CUT&Tag sequencing. In vivo, we adopted unilateral anterior crossbites (UAC) mice model to investigate the expression of H3K4me3 and ZBTB20 in aberrant force-related cartilage pathogenesis.

Results

The results demonstrated that FSS greatly disrupts cell morphology and significantly decreased chondrocyte viability. Aberrant FSS induces remarkable inflammatory mediators production, leading to cartilage degeneration and degradation. In depth mechanistic study showed that FSS results in more than 10-fold upregulation of H3K4me3, and the modulatory effect of H3K4me3 on cartilage was obtained by directly targeting ZBTB20. Furthermore, Wnt signaling was strongly activated in high FSS-induced OA pathogenesis, and the negative impact of ZBTB20 on chondrocytes was also achieved through activating Wnt signaling pathway. Moreover, pharmacological inhibition of H3K4me3 activation by MM-102 or treatment with Wnt pathway inhibitor LF3 could effectively alleviate the destructive effect of FSS on chondrocytes. In vivo UAC mice model validated the dysregulation of H3K4me3 and ZBTB20 in aberrant force-induced cartilage pathogenesis.

Conclusion

Through the combination of in vitro FSS model and in vivo UAC model, KMT2B-H3K4me3-ZBTB20 axis was first identified in aberrant FSS-induced cartilage pathogenesis, which may provide evidences for epigenetic-based therapy in the future.

Effects of and Response to Mechanical Loading on the Knee

Mechanical loading to the knee joint results in a differential response based on the local capacity of the tissues (ligament, tendon, meniscus, cartilage, and bone) and how those tissues subsequently adapt to that load at the molecular and cellular level. Participation in cutting, pivoting, and jumping sports predisposes the knee to the risk of injury. In this narrative review, we describe different mechanisms of loading that can result in excessive loads to the knee, leading to ligamentous, musculotendinous, meniscal, and chondral injuries or maladaptations. Following injury (or surgery) to structures around the knee, the primary goal of rehabilitation is to maximize the patient's response to exercise at the current level of function, while minimizing the risk of re-injury to the healing tissue. Clinicians should have a clear understanding of the specific injured tissue(s), and rehabilitation should be driven by knowledge of tissue-healing constraints, knee complex and lower extremity biomechanics, neuromuscular physiology, task-specific activities involving weight-bearing and non-weight-bearing conditions, and training principles. We provide a practical application for prescribing loading progressions of exercises, functional activities, and mobility tasks based on their mechanical load profile to knee-specific structures during the rehabilitation process. Various loading interventions can be used by clinicians to produce physical stress to address body function, physical impairments, activity limitations, and participation restrictions. By modifying the mechanical load elements, clinicians can alter the tissue adaptations, facilitate motor learning, and resolve corresponding physical impairments. Providing different loads that create variable tensile, compressive, and shear deformation on the tissue through mechanotransduction and specificity can promote the appropriate stress adaptations to increase tissue capacity and injury tolerance. Tools for monitoring rehabilitation training loads to the knee are proposed to assess the reactivity of the knee joint to mechanical loading to monitor excessive mechanical loads and facilitate optimal rehabilitation.

Potential of Exosomes as Cell-Free Therapy in Articular Cartilage Regeneration: A Review

Treatment of cartilage defects such as osteoarthritis (OA) and osteochondral defect (OCD) remains a huge clinical challenge in orthopedics. OA is one of the most common chronic health conditions and is mainly characterized by the degeneration of articular cartilage, shown in the limited capacity for intrinsic repair. OCD refers to the focal defects affecting cartilage and the underlying bone. The current OA and OCD management modalities focus on symptom control and on improving joint functionality and the patient’s quality of life. Cell-based therapy has been evaluated for managing OA and OCD, and its chondroprotective efficacy is recognized mainly through paracrine action. Hence, there is growing interest in exploiting extracellular vesicles to induce cartilage regeneration. In this review, we explore the in vivo evidence of exosomes on cartilage regeneration. A total of 29 in vivo studies from the PubMed and Scopus databases were identified and analyzed. The studies reported promising results in terms of in vivo exosome delivery and uptake; improved cartilage morphological, histological, and biochemical outcomes; enhanced subchondral bone regeneration; and improved pain behavior following exosome treatment. In addition, exosome therapy is safe, as the included studies documented no significant complications. Modifying exosomal cargos further increased the cartilage and subchondral bone regeneration capacity of exosomes. We conclude that exosome administration is a potent cell-free therapy for alleviating OA and OCD. However, additional studies are needed to confirm the therapeutic potential of exosomes and to identify the standard protocol for exosome-based therapy in OA and OCD management.

Intraosseous Injections Are Safe And Effective in Knee Osteoarthritis: A Systematic Review

PURPOSE

To evaluate clinical outcomes after intraosseous injection for knee osteoarthritis systematically with available clinical evidence.

METHODS

A systematic search methodology of the PUBMED, EMBASE, and CINAHL databases was conducted in November 2020. The search workflow was in adherence to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). The following inclusion criteria were adopted: clinical trials of any level of evidence, reporting clinical outcomes following intraosseous injections of bone substitutes or biologic agents, and mesenchymal stem cells or platelet-rich plasma into the knee as treatment modalities for osteoarthritis. Duplicate data and articles not written in English were excluded from this review.

RESULTS

Six studies were identified and included in this review, with a total of 167 patients. Two studies used subchondroplasty CaP injections, while 4 studies used intraosseous injections of platelet-rich plasma. Two studies provided Level II evidence, 2 studies provided Level III evidence, and a further 2 provided Level IV evidence. Five out of 6 studies reported data using the visual analog scale, 4 studies used the Knee Injury and Osteoarthritis Outcome Score, while 3 studies used the Western Ontario and McMaster Universities Osteoarthritis Index. Clinical improvements in pain and functionality were documented in all trials, with only a few patients experiencing adverse events.

CONCLUSION

Intraosseous injections for knee osteoarthritis are safe and effective. However, multiple pertinent variables such as safety, cost of treatment, and performance against placebos and other treatment modalities require further evaluation before intraosseous injections can be considered as standard treatment for patients presenting with osteoarthritis of the knee.

Cardiovascular Drugs and Osteoarthritis: Effects of Targeting Ion Channels

Osteoarthritis (OA) and cardiovascular diseases (CVD) share many similar features, including similar risk factors and molecular mechanisms. A great number of cardiovascular drugs act via different ion channels and change ion balance, thus modulating cell metabolism, osmotic responses, turnover of cartilage extracellular matrix and inflammation. These drugs are consumed by patients with CVD for many years; however, information about their effects on the joint tissues has not been fully clarified. Nevertheless, it is becoming increasingly likely that different cardiovascular drugs may have an impact on articular tissues in OA. Here, we discuss the potential effects of direct and indirect ion channel modulating drugs, including inhibitors of voltage gated calcium and sodium channels, hyperpolarization-activated cyclic nucleotide-gated channels, β-adrenoreceptor inhibitors and angiotensin-aldosterone system affecting drugs. The aim of this review was to summarize the information about activities of cardiovascular drugs on cartilage and subchondral bone and to discuss their possible consequences on the progression of OA, focusing on the modulation of ion channels in chondrocytes and other joint cells, pain control and regulation of inflammation. The implication of cardiovascular drug consumption in aetiopathogenesis of OA should be considered when prescribing ion channel modulators, particularly in long-term therapy protocols.

Stem Cells in Autologous Microfragmented Adipose Tissue: Current Perspectives in Osteoarthritis Disease

Osteoarthritis (OA) is a chronic debilitating disorder causing pain and gradual degeneration of weight-bearing joints with detrimental effects on cartilage volume as well as cartilage damage, generating inflammation in the joint structure. The etiology of OA is multifactorial. Currently, therapies are mainly addressing the physical and occupational aspects of osteoarthritis using pharmacologic pain treatment and/or surgery to manage the symptomatology of the disease with no specific regard to disease progression or prevention. Herein, we highlight alternative therapeutics for OA specifically considering innovative and encouraging translational methods with the use of adipose mesenchymal stem cells.