Osteoarthritis: pathobiology-targets and ways for therapeutic intervention

Nordihydroguaiaretic acid microparticles are effective in the treatment of osteoarthritis

Several disease-modifying osteoarthritis (OA) drugs have emerged, but none have been approved for clinical use due to their systemic side effects, short half-life, and rapid clearance from the joints. Nordihydroguaiaretic acid (NDGA), a reactive oxygen species (ROS) scavenger and autophagy inducer, could be a potential treatment for OA. In this report, we show for the first time that sustained delivery of NDGA through polymeric microparticles maintains therapeutic concentrations of drug in the joint and ameliorates post-traumatic OA (PTOA) in a mouse model. In vitro treatment of oxidatively stressed primary chondrocytes from OA patients using NDGA-loaded poly(lactic-co-glycolic acid) (PLGA) microparticles (NDGA-MP) inhibited 15-lipoxygenase, induced autophagy, prevented chondrosenescence, and sustained matrix production. In vivo intra-articular delivery of NDGA-MP was non-toxic and had prolonged retention time (up to 35 days) in murine knee joints. Intra-articular therapy using NDGA-MP effectively reduced cartilage damage and reduced pain in the surgery-induced PTOA mouse model. Our studies open new avenues to modulate the immune environment and treat post-traumatic OA using ROS quenchers and autophagy inducers.

Pyroptosis: A spoiler of peaceful coexistence between cells in degenerative bone and joint diseases

BACKGROUND

As people age, degenerative bone and joint diseases (DBJDs) become more prevalent. When middle-aged and elderly people are diagnosed with one or more disorders such as osteoporosis (OP), osteoarthritis (OA), and intervertebral disc degeneration (IVDD), it often signals the onset of prolonged pain and reduced functionality. Chronic inflammation has been identified as the underlying cause of various degenerative diseases, including DBJDs. Recently, excessive activation of pyroptosis, a form of programed cell death (PCD) mediated by inflammasomes, has emerged as a primary driver of harmful chronic inflammation. Consequently, pyroptosis has become a potential target for preventing and treating DBJDs.

AIM OF REVIEW

This review explored the physiological and pathological roles of the pyroptosis pathway in bone and joint development and its relation to DBJDs. Meanwhile, it elaborated the molecular mechanisms of pyroptosis within individual cell types in the bone marrow and joints, as well as the interplay among different cell types in the context of DBJDs. Furthermore, this review presented the latest compelling evidence supporting the idea of regulating the pyroptosis pathway for DBJDs treatment, and discussed the potential, limitations, and challenges of various therapeutic strategies involving pyroptosis regulation.

KEY SCIENTIFIC CONCEPTS OF REVIEW

In summary, an interesting identity for the unregulated pyroptosis pathway in the context of DBJDs was proposed in this review, which was undertaken as a spoiler of peaceful coexistence between cells in a degenerative environment. Over the extended course of DBJDs, pyroptosis pathway perpetuated its activity through crosstalk among pyroptosis cascades in different cell types, thus exacerbating the inflammatory environment throughout the entire bone marrow and joint degeneration environment. Correspondingly, pyroptosis regulation therapy emerged as a promising option for clinical treatment of DBJDs.

Attenuation of osteoarthritis progression via locoregional delivery of Klotho-expressing plasmid DNA and Tanshinon IIA through a stem cell-homing hydrogel

BACKGROUND

Osteoarthritis (OA) is an aging-related degenerative joint disorder marked by joint discomfort and rigidity. Senescent chondrocytes release pro-inflammatory cytokines and extracellular matrix-degrading proteins, creating an inflammatory microenvironment that hinders chondrogenesis and accelerates matrix degradation. Targeting of senescent chondrocytes may be a promising approach for the treatment of OA. Herein, we describe the engineering of an injectable peptide-hydrogel conjugating a stem cell-homing peptide PFSSTKT for carrying plasmid DNA-laden nanoparticles and Tanshinon IIA (pPNP + TIIA@PFS) that was designed to attenuate OA progression by improving the senescent microenvironment and fostering cartilage regeneration.

RESULTS

Specifically, pPNP + TIIA@PFS elevates the concentration of the anti-aging protein Klotho and blocks the transmission of senescence signals to adjacent healthy chondrocytes, significantly mitigating chondrocyte senescence and enhancing cartilage integrity. Additionally, pPNP + TIIA@PFS recruit bone mesenchymal stem cells and directs their subsequent differentiation into chondrocytes, achieving satisfactory chondrogenesis. In surgically induced OA model rats, the application of pPNP + TIIA@PFS results in reduced osteophyte formation and attenuation of articular cartilage degeneration.

CONCLUSIONS

Overall, this study introduces a novel approach for the alleviation of OA progression, offering a foundation for potential clinical translation in OA therapy.

Intra-articular injection of rapamycin microparticles prevent senescence and effectively treat osteoarthritis

Trauma to the knee joint is associated with significant cartilage degeneration and erosion of subchondral bone, which eventually leads to osteoarthritis (OA), resulting in substantial morbidity and healthcare burden. With no disease-modifying drugs in clinics, the current standard of care focuses on symptomatic relief and viscosupplementation. Modulation of autophagy and targeting senescence pathways are emerging as potential treatment strategies. Rapamycin has shown promise in OA disease amelioration by autophagy upregulation, yet its clinical use is hindered by difficulties in achieving therapeutic concentrations, necessitating multiple weekly injections. Rapamycin-loaded in poly(lactic-co-glycolic acid) microparticles (RMPs) induced autophagy, prevented senescence, and sustained sulphated glycosaminoglycans production in primary human articular chondrocytes from OA patients. RMPs were potent, nontoxic, and exhibited high retention time (up to 35 days) in mice joints. Intra-articular delivery of RMPs effectively mitigated cartilage damage and inflammation in surgery-induced OA when administered as a prophylactic or therapeutic regimen. Together, the study demonstrates the feasibility of using RMPs as a potential clinically translatable therapy to prevent the progression of post-traumatic OA.

Metaphyseal fixation in revision knee arthroplasty: a systematic review of the literature and meta-analysis of mid-long-term outcomes of metaphyseal sleeves and cones

Metaphyseal augmentation has in recent years formed a key strategy in management of bone loss in revision knee arthroplasty. There are studies reporting excellent short-term results, however long- term data is lacking. There is also a paucity of studies comparing the most frequently utilised augments, metaphyseal sleeves, and cones. We conducted a systematic review and meta-analysis to evaluate and compare the mid to long term outcomes of metaphyseal cones and sleeves. We conducted systematic search of 4 databases (Medline, Embase, CINALH and PubMed). Seventeen studies were found to be eligible for inclusion of which ten investigated metaphyseal sleeves and the remaining seven investigated cones. Mean follow up across all studies was 6.2 years. The total number of patients included in the studies was 1319 and the number of knees operated on was 1431. We noted a higher revision rate of metaphyseal cones when compared to sleeves 10.85% vs 6.31 (p=0.007). Reoperation rates were also higher in cones compared to sleeves, 13.78% vs 3.68% (p<0.001). Prosthetic joint infection was the most common reason for revision. The difference in conversion rates, based on augment location was statistically significant p=0.019. When undertaking further sub-analysis; there was no statistically significant difference when comparing revision rates of; tibial vs femoral augments p=0.108, tibial vs tibial & femur p=0.54 but a difference was seen between femoral vs tibial & femoral augments p=0.007. Based on our data, metaphyseal sleeves demonstrate significantly lower revision rates compared to metaphyseal cones. However overall, both demonstrate reliable mid to long-term outcomes.

Correlations in radiographic and MAKO Total Knee Robotic-Assisted Surgery intraoperative limb coronal alignment

Robotic-assisted arthroplasty has become increasingly established in recent years. The aim of the study is to determine if intraoperative coronal alignment during robotic-assisted total knee arthroplasty correlates with radiographic alignment. We prospectively compared the pre- and postoperative limb alignment values measured on long leg standing radiographs with intraoperative robotic-assisted measurements for 100 patients who underwent primary total knee arthroplasty. Two-tailed bivariate Pearson correla- tions were performed to evaluate the strength of the association between radiographic and robotic- assisted alignment. The intraclass correlation coeffi- cient (ICC) was used to estimate interrater reliability. There was a male/female ratio of 1.16 and the mean age was 67 years (range 42-88). Robotic-assisted measurements slightly overestimated the degree of varus relative to radiographs. Radiographic and robotic-assisted measurements were strongly correlated (r = 0.915, p < 0.001) preoperatively, with a difference of 1.6 ± 3.2°. The average measure ICC was 0.996 with a 95% confidence interval from 0.995 to 0.997 (p < 0.001). Postoperatively a bigger difference was measured (3.1° ± 1.9°), comparing radiographic and MAKO alignment. A moderate correlation was observed between the postoperative radiographic and MAKO outcome alignment (r = 0.604, p < 0.001). The average measure ICC was 0.977 with a 95% confidence interval from 0.967 to 0.984 (p < 0.001). There is a strong correlation in the preoperative set- ting between radiographic and robotic-assisted lower limb alignment and a moderate correlation in the post-operative setting. The values measured by the MAKO Total Knee application were considerably more in varus.

Inhibition of Knee Osteoarthritis Progression in Mice by Administering SRT2014, an Activator of Silent Information Regulator 2 Ortholog 1

OBJECTIVE

Previous findings suggest that silent information regulator 2 ortholog 1 (SIRT1) plays essential roles in chondrocytes and prevents osteoarthritis (OA) development. The purpose of this study was to investigate the effects of intraperitoneal (i.p.) and intra-articular (i.a.) administration of the SIRT1 activator SRT2104, which has been approved for use in humans.

DESIGN

OA was induced by destabilizing the medial meniscus in the knee joint of 12-week-old CL57BL/6J mice. The mice were divided into 3 groups, that is, the control group, SRT2104 i.p.-injection group, and SRT2104 i.a.-injection group. Tissues were harvested at 4, 8, 12, and 16 weeks postsurgery. OA progression was evaluated using the Osteoarthritis Research Society International (OARSI) score. The production of OA-related proteins in cartilage and synovium was examined by immunohistochemistry.

RESULTS

OARSI scores in the control group were significantly higher at 8 and 12 weeks compared with other 2 groups. Immunohistochemical analysis showed that Sirt1 and type-2 collagen significantly increased, whereas MMP-13, ADAMTS-5, IL-1β, IL-6, cleaved caspase 3, PARP p85, acetylated NF-κB p65, and iNOS decreased significantly in cartilage tissues from the i.p. and i.a, SRT2104 groups. In the synovium, more iNOS-positive M1-like macrophages were observed in the control group than in the i.p. and i.a, SRT2104 groups, whereas more CD206-positive M2-like macrophages were detected in the i.p. and i.a. SRT2104 groups.

CONCLUSIONS

Both i.p. and i.a. SRT2104 injection reduced OA progression in the mouse OA model, suggesting that SRT2104 can serve as a new treatment for OA.

Impact of Controlling Abnormal Joint Movement on the Effectiveness of Subsequent Exercise Intervention in Mouse Models of Early Knee Osteoarthritis

OBJECTIVE

Moderate mechanical stress is necessary for preserving the cartilage. The clinician empirically understands that prescribing only exercise will progress osteoarthritis (OA) for knee OA patients with abnormal joint movement. When prescribing exercise for OA, we hypothesized that degeneration of articular cartilage could be further prevented by combining interventions with the viewpoint of normalizing joint movement.

DESIGN

Twelve-week-old ICR mice underwent anterior cruciate ligament transection (ACL-T) surgery in their right knee and divided into 4 groups: ACL-T, controlled abnormal joint movement (CAJM), ACL-T with exercise (ACL-T/Ex), CAJM with exercise (CAJM/Ex). Animals in the walking group were subjected to treadmill exercise 6 weeks after surgery, which included walking for 18 m/min, 30 min/d, 3 d/wk for 4 weeks. Joint instability was measured by anterior drawer test, and safranin-O staining and immunohistochemical staining were performed.

RESULTS

OARSI (Osteoarthritis Research Society International) score of ACL-T/Ex group showed highest among 4 groups (P < 0.001). And CAJM/Ex group was lower than ACL-T/Ex group. Positive cell ratio of IL-1β and MMP-13 in CAJM/Ex group was lower than ACL-T/Ex group (P < 0.05).

CONCLUSIONS

We found that the state of the intra-articular environment can greatly influence the effect of exercise on cartilage degeneration, even if exercise is performed under the same conditions. In the CAJM/Ex group where joint movement was normalized, abnormal mechanical stress such as shear force and compression force accompanying ACL cutting was alleviated. These findings may highlight the need to consider an intervention to correct abnormal joint movement before prescribing physical exercise in the treatment of OA.

Echinacoside Upregulates Sirt1 to Suppress Endoplasmic Reticulum Stress and Inhibit Extracellular Matrix Degradation In Vitro and Ameliorates Osteoarthritis In Vivo

Background

Osteoarthritis (OA) is a progressive illness that destroys cartilage. Oxidative stress is a major contributor of OA, while endoplasmic reticulum (ER) stress is the key cellular damage under oxidative stress in chondrocytes. Echinacoside (ECH) is the main extract and active substance of Cistanche, with potent antioxidative stress (OS) properties, and currently under clinical trials in China. However, its function in OA is yet to be determined.

Purpose

We aimed to explore the specific role of ECH in the occurrence and development of OA and its underlying mechanism in vivo and in vitro.

Methods

After the mice were anesthetized, the bilateral medial knee joint meniscus resection was performed to establish the DMM model. TBHP was used to induce oxidative stress to establish the OA model in chondrocytes in vitro. Western blot and RT-PCR were used to evaluate the level of ER stress-related biomarkers such as p-PERK/PERK, GRP78, ATF4, p-eIF2α/eIF2α, and CHOP and apoptosis-related proteins such as BAX, Bcl-2, and cleaved caspase-3. Meanwhile, we used SO staining, immunofluorescence, and immunohistochemical staining to evaluate the pharmacological effects of ECH in mice in vivo.

Results

We demonstrated the effectiveness of ECH in suppressing ER stress and restoring ECM metabolism in vitro. In particular, ECH was shown to suppress tert-Butyl hydroperoxide- (TBHP-) induced OS and subsequently lower the levels of p-PERK/PERK, GRP78, ATF4, p-eIF2α/eIF2α, and CHOP in vitro. Simultaneously, ECH reduced MMP13 and ADAMTS5 levels and promoted Aggrecan and Collagen II levels, suggesting ECM degradation suppression. Moreover, we showed that ECH mediates its cellular effects via upregulation of Sirt1. Lastly, we confirmed that ECH can protect against OA in mouse OA models.

Conclusion

In summary, our findings indicate that ECH can inhibit ER stress and ECM degradation by upregulating Sirt1 in mouse chondrocytes treated with TBHP. It can also prevent OA development in vivo.

Synovial Fluid Cytokines, Chemokines and MMP Levels in Osteoarthritis Patients with Knee Pain Display a Profile Similar to Many Rheumatoid Arthritis Patients

Background: There are currently no effective disease-modifying drugs to prevent cartilage loss in osteoarthritis and synovial fluid is a potentially valuable source of biomarkers to understand the pathogenesis of different types of arthritis and identify drug responsiveness. The aim of this study was to compare the differences between SF cytokines and other proteins in patients with OA (n = 21) to those with RA (n = 27) and normal knees (n = 3). Methods: SF was obtained using ultrasound (US) guidance and an external pneumatic compression device. RA patients were categorized as active (n = 20) or controlled (n = 7) based upon SF white blood cell counts (> or <300 cells/mm³). Samples were cryopreserved and analyzed by multiplex fluorescent bead assays (Luminex). Between-group differences of 16 separate biomarker proteins were identified using ANOVA on log10-transformed concentrations with p values adjusted for multiple testing. Results: Only six biomarkers were significantly higher in SF from active RA compared to OA—TNF-α, IL-1-β IL-7, MMP-1, MMP-2, and MMP-3. Only MMP-8 levels in RA patients correlated with SF WBC counts (p < 0.0001). Among OA patients, simultaneous SF IL-4, IL-6, IL-8, and IL-15 levels were higher than serum levels, whereas MMP-8, MMP-9, and IL-18 levels were higher in serum (p < 0.05). Conclusion: These results support the growing evidence that OA patients have a pro-inflammatory/catabolic SF environment. SF biomarker analysis using multiplex testing and US guidance may distinguish OA phenotypes and identify treatment options based upon targeted inflammatory pathways similar to patients with RA.

Angiotensin II triggers knee joint lesions in experimental osteoarthritis

OBJECTIVES

This study aimed to evaluate the involvement of Angiotensin II (Ang II) in joint lesions associated with osteoarthritis (OA) in vitro and in vivo.

METHODS

Chondrocyte cultures were obtained from knee joints of neonatal rats and stimulated with Ang II/MIA/ACE inhibitors. In vivo, rats treated or not with the ACE inhibitor captopril, received daily injections of Ang II or sodium monoiodoacetate (MIA) in knee joints for evaluation of cartilage, bone, and synovial lesions.

RESULTS

Cultured chondrocytes expressed the mRNA for Ace, Agtr1, Agtr2, and Mas1. Stimulating cells with Ang II reduced chondrocyte viability and metabolism. Accordingly, in vivo Ang II injection into the knees of rats triggered hyperalgesia, joint edema, increased the number of leukocytes in the joint cavity, and induced cartilage lesions associated with OA alterations. In further experiments, Ang II synthesis was prevented with the ACE inhibitor Captopril in the context of MIA-induced OA. Ang II inhibition with captopril improved the OARSI score, induced chondroprotection, and reduced the leukocyte recruitment from synovium after MIA. Additionally, captopril prevented MIA-induced bone resorption, by decreasing the number of osteoclasts and increasing the expression of IL-10 in the bone. In vitro, inhibiting Ang II synthesis decreased MIA-induced chondrocyte death and increased Col2a1 transcription.

CONCLUSION

Ang II induces chondrocyte death and joint tissue damages associated with OA and its modulation can be a therapeutic strategy in osteoarthritis.

DMY protects the knee joints of rats with collagen-induced arthritis by inhibition of NF-κB signaling and osteoclastic bone resorption

Collagen-induced arthritis (CIA) is a widely used animal model for studying rheumatoid arthritis (RA), which manifests serious joint dysfunction, progressive bone erosion and articular cartilage destruction. Considering that joint damage in RA is caused by systemic inflammation and dihydromyricetin (DMY), the main flavonoid of Ampelopsis Michx, possesses anti-inflammatory properties, in the present study we have investigated the potential capability of DMY to inhibit inflammation-mediated joint damage and explore the underlying mechanisms. A rat model of RA induced by CIA was administered with DMY for 5 weeks. Prior to histological analysis, the knee joints were scanned by microcomputed tomography (μCT) to detect bone damage. Articular cartilage destruction was assessed by Alcian blue and Toluidine blue staining and the pathological alteration of osteoblasts and osteoclasts in joints was evaluated by hematoxylin-eosin (H&E) and tartrate-resistant acid phosphatase (TRAP) staining, respectively. The effects of DMY on osteoblast differentiation and osteoclast formation in vitro were investigated. Consistent with the in vivo results, DMY had no significant effect on osteoblast differentiation but an inhibitory effect on osteoclast formation. Furthermore, we determined that the mechanism of the DMY-suppressed osteoclast formation was blocking the phosphorylation of I-κB kinase (IKK) so as to hinder the activation of nuclear factor-κB (NF-κB). Collectively, DMY could ameliorate knee joint damage, especially in articular cartilage, which is the weight-bearing region, by inhibiting osteoclast formation through NF-κB signaling.

Effects of two different aquatic exercise trainings on cardiopulmonary endurance and emotional status in patients with knee osteoarthritis

BACKGROUND

Aquatic exercises are often recommended for people with osteoarthritis (OA), however, there is a lack of evidence about the effects of these exercises.

OBJECTIVES

The purpose of this study was to investigate the effects of two different aquatic exercise trainings on cardiopulmonary endurance and emotional status in patients with knee osteoarthritis.

METHODS

Eighty-nine patients who had been diagnosed with knee osteoarthritis were divided into three groups as two different aquatic exercise training groups (only lower extremity training vs. lower extremity + upper extremity and trunk exercises) or the control group. All groups have received the conventional therapy which consisted of hotpack, ultrasound, transcutaneous electrical nerve stimulation (TENS), and home exercises. Six-minute walk test (6MWT) and the Hospital Anxiety and Depression Scale (HAD) were used for assessing cardiopulmonary endurance and emotional status, respectively.

RESULTS

Following the treatment, all groups improved in terms of systolic blood pressure, walking distance and total HAD scores. Group 1 showed additional improvements in diastolic blood pressure, heart rate and perceived exertion, while Group 2 showed additional improvements only in perceived exertion. Greater changes before and after the treatment in diastolic blood pressure at rest and following 6MWT, perceived exertion following 6MWT, walking distance, HAD depression scores and HAD anxiety scores were observed in Group 1.

CONCLUSIONS

Exercise therapy consisting of only lower extremity exercises in water might be more effective in improving exercise capacity and depression levels in comparison to upper extremity and trunk added exercises or conventional physical therapy.

Long Noncoding RNA Nuclear Enriched Abundant Transcript 1 (NEAT1) Regulates Proliferation, Apoptosis, and Inflammation of Chondrocytes via the miR-181a/Glycerol-3-Phosphate Dehydrogenase 1-Like (GPD1L) Axis

Background

Osteoarthritis (OA) is one of the most common chronic musculoskeletal diseases, yet to date it lacks effective therapeutic strategies. Increasing evidence suggests that long noncoding RNAs (lncRNAs) serve pivotal roles in the occurrence and development of OA. However, the possible molecular mechanism involving lncRNAs, such as nuclear enriched abundant transcript 1 (NEAT1), in OA progression is still unclear.

Material/Methods

First, NEAT1 and miR-181a expression in OA synovium tissues and normal synovium tissues were detected. Then, the effect of NEAT1 on modulating growth ability, apoptosis, and inflammation in OA chondrocytes was investigated by a series of loss-function experiments. Next, the correlation between NEAT1, miR-181a, and glycerol-3-phosphate dehydrogenase 1-like (GPD1L) was fully investigated. Finally, the downregulation of miR-181a was employed as a recovery experiment to explore the functional mechanism of NEAT1 in OA.

Results

In the present study, we found that NEAT1 expression was downregulated in OA tissues, while miR-181a expression was prominently upregulated. Moreover, reduced expression of NEAT1 suppressed cell growth while elevating the apoptotic rate and increasing the abundance of inflammatory cytokines released in OA chondrocytes. Furthermore, we clarified that miR-181a was a direct sponge of NEAT1, and GPD1L was able to bind to miR-181a. Additionally, we found that downregulation of miR-181a was able to attenuate the effect of NEAT1 on apoptosis, inflammatory response, and proliferation in OA chondrocytes.

Conclusions

Our findings indicate that downregulation of NEAT1 aggravated progression of OA via modulating the miR-181a/GPD1L axis, providing a novel insight into the mechanism of OA pathogenesis.

Regulatory Effects and Interactions of the Wnt and OPG-RANKL-RANK Signaling at the Bone-Cartilage Interface in Osteoarthritis

Cartilage and the bordering subchondral bone form a functionally active regulatory interface with a prominent role in osteoarthritis pathways. The Wnt and the OPG-RANKL-RANK signaling systems, as key mediators, interact in subchondral bone remodeling. Osteoarthritic osteoblasts polarize into two distinct phenotypes: a low secretory and an activated, pro-inflammatory and anti-resorptive subclass producing high quantities of IL-6, PGE2, and osteoprotegerin, but low levels of RANKL, thus acting as putative effectors of subchondral bone sclerosis. Wnt agonists, Wnt5a, Wisp-1 initiate excessive bone remodeling, while Wnt3a and 5a simultaneously cause loss of proteoglycans and phenotype shift in chondrocytes, with decreased expression of COL2A, aggrecan, and Sox-9. Sclerostin, a Wnt antagonist possesses a protective effect for the cartilage, while DKK-1 inhibits VEGF, suspending neoangiogenesis in the subchondral bone. Experimental conditions mimicking abnormal mechanical load, the pro-inflammatory milieu, but also a decreased OPG/RANKL ratio in the cartilage, trigger chondrocyte apoptosis and loss of the matrix via degradative matrix metalloproteinases, like MMP-13 or MMP-9. Hypoxia, an important cofactor exerts a dual role, promoting matrix synthesis via HIF-1α, a Wnt silencer, but turning on HIF-2α that enhances VEGF and MMP-13, along with aberrant collagen expression and extracellular matrix deterioration in the presence of pro-inflammatory cytokines.

Estrogen prevents articular cartilage destruction in a mouse model of AMPK deficiency via ERK-mTOR pathway

Background

To investigate the mechanism underlying the chondroprotective effect of estrogen in AMP-activated protein kinase (AMPK) deficiency mice.

Methods

Female cartilage-specific AMPKα double knockout (AMPKα cDKO) mice were generated and subjected to ovariectomy (OVX). The model of osteoarthritis (OA) was induced by destabilization of medial meniscus (DMM). Histopathological changes were evaluated by using OARSI scoring systems. Autophagy changes were analyzed by immunofluorescence staining. Human chondrocytes were subjected to mechanical stress to mimic OA development. and incubated in presence of or absence of 17β-estradiol or/and compound C (AMPK inhibitor) or/and U0126 (ERK inhibitor). The expression levels of ERK1/2 phosphorylation, p70S6K phosphorylation and light chain 3 (LC3) were detected by Western blot.

Results

Compared with in OVX-sham AMPKα cDKO and OVX-sham WT mice, DMM-induced OA is more severe, and significantly low level of LC3 was observed in articular cartilage in OVX AMPK cDKO mice. Both mechanical stress and compound C were shown to induce an increase in phosphorylation of p70S6K, respectively. 17β-estradiol stimulation led to a reduction in the basal level of p70S6K phosphorylation as well as in the compound C or mechanical stress-induced level of p70S6K phosphorylation. 17β-estradiol stimulation not only led to an increase in LC3 conversion but also overrode the inhibitory effect of compound C on LC3 conversion. The effects of 17β-estradiol were abrogated by blocking ERK signaling pathway.

Conclusions

Our findings suggest that estrogen can protect articular cartilage from damage during OA development by promoting chondrocyte autophagy via ERK-mammalian target of rapamycin (mTOR) signaling, and give new insight into the mechanism of the chondroprotective effect of estrogen.

EGR1 promotes the cartilage degeneration and hypertrophy by activating the Krüppel-like factor 5 and β-catenin signaling

Osteoarthritis is one of the most common orthopedic diseases in elderly people who have lost their mobility. In this study，we observed abnormally high EGR1 expression in the articular cartilage of patients with osteoarthritis. We also found significantly high EGR1 expression in the articular cartilage of mice with destabilized medial meniscus (DMM)-induced osteoarthritis and 20-month-old mice. In vitro experiments indicated that IL-1β could significantly enhance EGR1 expression in primary mouse chondrocytes. EGR1 over-expression in chondrocytes using adenovirus could inhibit COl2A1 expression and enhance MMP9 and MMP13 expression. And silencing EGR1, using RNAi, had the opposite effects. Moreover, EGR1 over-expression accelerated chondrocyte hypertrophy in vitro, and EGR1 knockdown reversed this effect. We then explored the underlying mechanism. EGR1 over-expression increased Kruppel-Like Factor 5 (KLF5) protein level without influencing its synthesis. Enhanced EGR1 expression induced its integration with KLF5, leading to suppressed ubiquitination of KLF5. Moreover, EGR1 prompted β-catenin nuclear transportation to control chondrocyte hypertrophy. Ectopic expression of EGR1 in articular cartilage aggravated the degradation of the cartilage matrix in vivo. The EGR1 inhibitor, ML264, protected chondrocytes from IL-1β-mediated cartilage matrix degradation in vitro and DMM-induced osteoarthritis in vivo. Above all, we demonstrate the effect and mechanisms of EGR1 on osteoarthritis and provide evidence that the ML264 might be a potential drug for treating osteoarthritis in the future.

Development of matrix metalloproteinase-13 inhibitors - A structure-activity/structure-property relationship study

A structure-activity/structure-property relationship study based on the physicochemical as well as in vitro pharmacokinetic properties of a first generation matrix metalloproteinase (MMP)-13 inhibitor (2) was undertaken. After systematic variation of inhibitor 2, compound 31 was identified which exhibited microsomal half-life higher than 20 min, kinetic solubility higher than 20 μM, and a permeability coefficient greater than 20 × 10^-6 cm/s. Compound 31 also showed excellent in vivo PK properties after IV dosing (C_max = 56.8 μM, T_1/2 (plasma) = 3.0 h, Cl = 0.23 mL/min/kg) and thus is a suitable candidate for in vivo efficacy studies in an OA animal model.

Composition, structure and tensile biomechanical properties of equine articular cartilage during growth and maturation

Articular cartilage undergoes structural and biochemical changes during maturation, but the knowledge on how these changes relate to articular cartilage function at different stages of maturation is lacking. Equine articular cartilage samples of four different maturation levels (newborn, 5-month-old, 11-month-old and adult) were collected (N = 25). Biomechanical tensile testing, Fourier transform infrared microspectroscopy (FTIR-MS) and polarized light microscopy were used to study the tensile, biochemical and structural properties of articular cartilage, respectively. The tensile modulus was highest and the breaking energy lowest in the newborn group. The collagen and the proteoglycan contents increased with age. The collagen orientation developed with age into an arcade-like orientation. The collagen content, proteoglycan content, and collagen orientation were important predictors of the tensile modulus (p < 0.05 in multivariable regression) and correlated significantly also with the breaking energy (p < 0.05 in multivariable regression). Partial least squares regression analysis of FTIR-MS data provided accurate predictions for the tensile modulus (r = 0.79) and the breaking energy (r = 0.65). To conclude, the composition and structure of equine articular cartilage undergoes changes with depth that alter functional properties during maturation, with the typical properties of mature tissue reached at the age of 5-11 months.

Glucagon-like peptide-1 receptor regulates endoplasmic reticulum stress-induced apoptosis and the associated inflammatory response in chondrocytes and the progression of osteoarthritis in rat

Treatments for osteoarthritis (OA) are designed to restore chondrocyte function and inhibit cell apoptosis. Previous studies have shown that activation of the glucagon-like peptide-1 receptor (GLP-1R) leads to anti-inflammatory and anti-apoptotic effects. However, the role of GLP-1R in the pathological process of OA is unclear. In present work, we aimed to demonstrate the potential effect of GLP-1R on chondrocytes and elucidate its underlying mechanisms. We found that activation of GLP-1R with liraglutide could protect chondrocytes against endoplasmic reticulum stress and apoptosis induced by interleukin (IL)-1β or triglycerides (TGs). These effects were partially attenuated by GLP-1R small interfering RNA treatment. Moreover, inhibiting PI3K/Akt signaling abolished the protective effects of GLP-1R by increase the apoptosis activity and ER stress. Activating GLP-1R suppressed the nuclear factor kappa-B pathway, decreased the release of inflammatory mediators (IL-6, tumor necrosis factor α), and reduced matrix catabolism in TG-treated chondrocytes; these effects were abolished by GLP-1R knockdown. In the end, liraglutide attenuated rat cartilage degeneration in an OA model of knee joints in vivo. Our results indicate that GLP-1R is a therapeutic target for the treatment of OA, and that liraglutide could be a therapeutic candidate for this clinical application.

Short-term effects of Theracurmin dose and exercise type on pain, walking ability, and muscle function in patients with knee osteoarthritis

The purpose of this study was to investigate the short-term of Theracurmin dose and exercise type on pain, walking ability, and muscle function in patients with knee osteoarthritis. Twenty-five patients with knee osteoarthritis randomly selected to Theracurmin intake (T) group and Theracurmin in combined with exercise (T+E) group. T group (n= 13) was taken orally a capsule of 700 mg, 3 times per day, (total 2,100 mg, 35 mg/kg-body weight). T+E group (n= 12) performed aerobic training of 30-min walking and weight training for increasing leg muscular strength. After treatment, the number of steps, muscle mass, range of motion of knee, and the muscle strength in flexion and extension significantly increased. The percent body fat, visual analogue scale, The Western Ontario and McMaster score, centers of pressure with closed eye, 10-m walking ability, stair ascending speed were significantly decreased after treatment. Although no difference observed between the T and T+E groups, the 4-week intake of Theracurmin with and without exercise appeared to be effective in reducing the pain and enhancing muscular and balancing function. Therefore, Theracurmin intake for early symptoms and additional exercise as symptoms alleviate might be an effective way of delaying and managing osteoarthritis, and additional studies investigating the effects of Theracurmin and exercise on osteoarthritis could be beneficial.

Suppressive Effects of Insulin on Tumor Necrosis Factor-Dependent Early Osteoarthritic Changes Associated With Obesity and Type 2 Diabetes Mellitus

Objective

Obesity is a state of chronic inflammation that is associated with insulin resistance and type 2 diabetes mellitus (DM), as well as an increased risk of osteoarthritis (OA). This study was undertaken to define the links between obesity‐associated inflammation, insulin resistance, and OA, by testing the hypotheses that 1) tumor necrosis factor (TNF) is critical in mediating these pathologic changes in OA, and 2) insulin has direct effects on the synovial joint that are compromised by insulin resistance.

Methods

The effects of TNF and insulin on catabolic gene expression were determined in fibroblast‐like synoviocytes (FLS) isolated from human OA synovium. Synovial TNF expression and OA progression were examined in 2 mouse models, high‐fat (HF) diet–fed obese mice with type 2 DM and TNF‐knockout mice. Insulin resistance was investigated in synovium from patients with type 2 DM.

Results

Insulin receptors (IRs) were abundant in both mouse and human synovial membranes. Human OA FLS were insulin responsive, as indicated by the dose‐dependent phosphorylation of IRs and Akt. In cultures of human OA FLS with exogenous TNF, the expression and release of MMP1, MMP13, and ADAMTS4 by FLS were markedly increased, whereas after treatment with insulin, these effects were selectively inhibited by >50%. The expression of TNF and its abundance in the synovium were elevated in samples from obese mice with type 2 DM. In TNF‐knockout mice, increases in osteophyte formation and synovial hyperplasia associated with the HF diet were blunted. The synovium from OA patients with type 2 DM contained markedly more macrophages and showed elevated TNF levels as compared to the synovium from OA patients without diabetes. Moreover, insulin‐dependent phosphorylation of IRs and Akt was blunted in cultures of OA FLS from patients with type 2 DM.

Conclusion

TNF appears to be involved in mediating the advanced progression of OA seen in type 2 DM. While insulin plays a protective, antiinflammatory role in the synovium, insulin resistance in patients with type 2 DM may impair this protective effect and promote the progression of OA.

miR-181a Modulates Chondrocyte Apoptosis by Targeting Glycerol-3-Phosphate Dehydrogenase 1-Like Protein (GPD1L) in Osteoarthritis

BACKGROUND miR-181a is a small non-coding RNA known to be dysregulated in osteoarthritis (OA), but the role of miR-181a in human OA remains unclear. The aim of this study was to identify its function and molecular target in chondrocytes during OA pathogenesis. MATERIAL AND METHODS The function of miR-181a was assessed by gain-of-function studies in human OA chondrocytes. Potential targets of miR-181a were predicted using series of bioinformatics and intersection analysis, then confirmed by luciferase reporter assay. Gene expression was quantified using quantitative reverse transcription PCR (qRT-PCR) assays, and protein production was quantified by Western blot analysis. RESULTS The FITC apoptosis assay results indicated that the upregulation of miR-181a led to an increase of apoptosis rate in chondrocytes. Then bioinformatic analysis identified potential target sites of the miR-181a located in the 3' untranslated region of GPD1L. Dual-luciferase reporter assays results showed that GPD1L is a target gene of miR-181a. Furthermore, Western blot and qRT-PCR analysis demonstrated that miR-181a inhibited GPD1L gene expression. Increased GPD1L and decreased miRNA-181a were observed in tissues from osteoarthritis patients. Moreover, we found a highly negative correlation between miRNA-181a and GPD1L. CONCLUSIONS Our results demonstrated that miR-181a may play an important role in the pathogenesis of OA through targeting GPD1L and regulating chondrocyte apoptosis.

Clinical platform for understanding the relationship between joint contact mechanics and articular cartilage changes after meniscal surgery

Injury to the meniscus of the knee has been implicated as a significant risk factor for the subsequent development of osteoarthritis, but the mechanisms of joint degeneration are unclear. Our objective was to develop a clinically applicable methodology to evaluate the relationship of joint contact mechanics at the time of surgery to biological changes of articular cartilage as a function of time following surgery. A series of pre-, intra-, and post-operative protocols were developed which utilized electronic sensors for the direct measurement of contact mechanics, and advanced imaging to assess cartilage health. The tests were applied to a pilot cohort of young active patients undergoing meniscus allograft transplantation. Our study demonstrated significant variability across patients in terms of contact area and peak contact stress, both before and after transplantation. Nonetheless, the majority of patients exhibited decreased peak contact stress and increased contact area after graft implantation. MR scans at 3-6 months showed decreased T1ρ values in tibial articular cartilage, suggesting an increase in proteoglycan content or concomitant decrease in water content. Prolongation of T2 values was found primarily within the central, cartilage-cartilage contact region of the tibial plateau suggested disruption of the collagen network. Minimal differences were found in cartilage thickness over the short time frame of this preliminary study. With longer clinical follow-up, our platform of clinical tests can be used to better understand the patient-specific mechanical factors that are related to increased risk of OA after meniscus injury and surgery. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:600-611, 2017.

AMPK deficiency in chondrocytes accelerated the progression of instability-induced and ageing-associated osteoarthritis in adult mice

Osteoarthritis (OA) is a progressive degenerative disease of the joints that is associated with both joint injury and ageing. Here, we investigated the role of the energy sensor AMP-activated protein kinase (AMPK) in maintaining a healthy state of articular cartilage and in OA development. Using cartilage-specific, tamoxifen-inducible AMPKα1 conditional knockout (AMPKα1 cKO), AMPKα2 conditional knockout (AMPKα2 cKO) and AMPKα1α2 conditional double knockout (AMPKα cDKO) mice, we found that compared with wild-type (WT) littermates, mutant mice displayed accelerated severity of surgically induced OA, especially AMPKα cDKO mice. Furthermore, male but not female AMPKα cDKO mice exhibited severely spontaneous ageing-associated OA lesions at 12 months of age. The chondrocytes isolated from AMPKα cDKO mice resulted in an enhanced interleukin-1β (IL-1β)-stimulated catabolic response. In addition, upregulated expression of matrix metalloproteinase-3 (MMP-3), MMP-13 and phospho-nuclear factor-κB (phospho-NF-κB) p65 and increased levels of apoptotic markers were detected in the cartilage of AMPKα cDKO mice compared with their WT littermates in vivo. Thus, our findings suggest that AMPK activity in chondrocytes is important in maintaining joint homeostasis and OA development.

Synthesis, Biological Evaluation, and Docking Studies of a Novel Sulfonamido-Based Gallate as Pro-Chondrogenic Agent for the Treatment of Cartilage

Gallic acid (GA) and its derivatives are anti-inflammatory agents and are reported to have potent effects on Osteoarthritis (OA) treatment. Nonetheless, it is generally accepted that the therapeutic effect and biocompatibility of GA is much weaker than its esters due to the high hydrophilicity. The therapeutic effect of GA on OA could be improved if certain structural modifications were made to increase its hydrophobicity. In this study, a novel sulfonamido-based gallate was synthesized by bonding sulfonamide with GA, and its biological evaluations on OA were investigated. Results show that 5-[4-(Pyrimidin-2-ylsulfamoylphenyl)]-carbamoyl-benzene-1,2,3-triyl triacetate (HAMDC) was able to reverse the effects induced by Interleukin-1 (IL-1) stimulation, and it also had a great effect on chondro-protection via promoting cell proliferation and maintaining the phenotype of articular chondrocytes, as well as enhancing synthesis of cartilage specific markers such as aggrecan, collagen II and Sox9. Furthermore, a docking study showed that HAMDC fits into the core of the active site of a disintegrin and metalloproteinase with thrombospondin motifs 5 (ADAMTS-5), which provides an explanation for its activity and selectivity.

Context-specific protection of TGFα null mice from osteoarthritis

Transforming growth factor alpha (TGFα) is a growth factor involved in osteoarthritis (OA). TGFα induces an OA-like phenotype in articular chondrocytes, by inhibiting matrix synthesis and promoting catabolic factor expression. To better understand TGFα’s potential as a therapeutic target, we employed two in vivo OA models: (1) post-traumatic and (2) aging related OA. Ten-week old and six-month old male Tgfa null mice and their heterozygous (control) littermates underwent destabilization of the medial meniscus (DMM) surgery. Disease progression was assessed histologically using the Osteoarthritis Research Society International (OARSI) scoring system. As well, spontaneous disease progression was analyzed in eighteen-month-old Tgfa null and heterozygous mice. Ten-week old Tgfa null mice were protected from OA progression at both seven and fourteen weeks post-surgery. No protection was seen however in six-month old null mice after DMM surgery, and no differences were observed between genotypes in the aging model. Thus, young Tgfa null mice are protected from OA progression in the DMM model, while older mice are not. In addition, Tgfa null mice are equally susceptible to spontaneous OA development during aging. Thus, TGFα might be a valuable therapeutic target in some post-traumatic forms of OA, however its role in idiopathic disease is less clear.

Imaging of Osteoarthritic Human Articular Cartilage using Fourier Transform Infrared Microspectroscopy Combined with Multivariate and Univariate Analysis

The changes in chemical composition of human articular cartilage (AC) caused by osteoarthritis (OA) were investigated using Fourier transform infrared microspectroscopy (FTIR-MS). We demonstrate the sensitivity of FTIR-MS for monitoring compositional changes that occur with OA progression. Twenty-eight AC samples from tibial plateaus were imaged with FTIR-MS. Hyperspectral images of all samples were combined for K-means clustering. Partial least squares regression (PLSR) analysis was used to compare the spectra with the OARSI grade (histopathological grading of OA). Furthermore, the amide I and the carbohydrate regions were used to estimate collagen and proteoglycan contents, respectively. Spectral peak at 1338 cm(-1) was used to estimate the integrity of the collagen network. The layered structure of AC was revealed using the carbohydrate region for clustering. Statistically significant correlation was observed between the OARSI grade and the collagen integrity in the superficial (r = -0.55) and the deep (r = -0.41) zones. Furthermore, PLSR models predicted the OARSI grade from the superficial (r = 0.94) and the deep (r = 0.77) regions of the AC with high accuracy. Obtained results suggest that quantitative and qualitative changes occur in the AC composition during OA progression, and these can be monitored by the use of FTIR-MS.

Trichostatin A increases the TIMP-1/MMP ratio to protect against osteoarthritis in an animal model of the disease

The histone deacetylase inhibitor trichostatin A (TSA) has been demonstrated to alleviate certain symptoms associated with osteoarthritis (OA). However, the exact mechanisms underlying this protective effect remain to be elucidated. The present study therefore examined the effects of TSA on the expression levels of interleukin-1β (IL-1β)-induced matrix metalloproteinases (MMPs) and tissue inhibitor of metalloproteinases-1 (TIMP-1) in vitro and in vivo. In vitro, reverse transcription-quantitative polymerase chain reaction was performed to investigate alterations in mRNA expression levels in TSA-treated chondrocytes in the presence or absence of IL-1β; in addition, protein expression and acetylation levels were assessed by western blotting. In vivo, TSA was administered to rats by intra-articular injection, following which the mRNA and protein expression levels were analyzed. In addition, macroscopic and histological observations were conducted. Chondrocytes treated with IL-1β demonstrated increased mRNA and protein expression levels of MMP-1, MMP-3 and MMP-13, and decreased expression levels of TIMP-1 mRNA and protein; these alterations were significantly attenuated by TSA treatment. In addition, increased MMPs and decreased TIMP-1 expression levels were observed in vivo in the OA rat model. TSA treatment demonstrated in vivo efficacy through the attenuation of various OA-associated molecular and physiological changes. Taken together, the results of the present study suggest that TSA has potential therapeutic value for the treatment of OA.

Vitamin E slows down the progression of osteoarthritis

Osteoarthritis is a chronic degenerative joint disorder with the characteristics of articular cartilage destruction, subchondral bone alterations and synovitis. Clinical signs and symptoms of osteoarthritis include pain, stiffness, restricted motion and crepitus. It is the major cause of joint dysfunction in developed nations and has enormous social and economic consequences. Current treatments focus on symptomatic relief, however, they lack efficacy in controlling the progression of this disease, which is a leading cause of disability. Vitamin E is safe to use and may delay the progression of osteoarthritis by acting on several aspects of the disease. In this review, how vitamin E may promote the maintenance of skeletal muscle and the regulation of nucleic acid metabolism to delay osteoarthritis progression is explored. In addition, how vitamin E may maintain the function of sex organs and the stability of mast cells, thus conferring a greater resistance to the underlying disease process is also discussed. Finally, the protective effect of vitamin E on the subchondral vascular system, which decreases the reactive remodeling in osteoarthritis, is reviewed.

Detecting early stage osteoarthritis by optical coherence tomography?

Osteoarthritis (OA) is the most common chronic disease of our joints, manifested by a dynamically increasing degeneration of hyaline articular cartilage (AC). While currently no therapy can reverse this process, the few available treatment options are hampered by the inability of early diagnosis. Loss of cartilage surface, or extracellular matrix (ECM), integrity is considered the earliest sign of OA. Despite the increasing number of imaging modalities surprisingly few imaging biomarkers exist. In this narrative review, recent developments in optical coherence tomography are critically evaluated for their potential to assess different aspects of AC quality as biomarkers of OA. Special attention is paid to imaging surface irregularities, ECM organization and the evaluation of posttraumatic injuries by light-based modalities.

Depletion of SIRT6 causes cellular senescence, DNA damage, and telomere dysfunction in human chondrocytes

OBJECTIVE

SIRT6, a member of the sirtuin family of nicotinamide adenine dinucleotide (NAD(+))-dependent protein deacetylases, has been implicated as a key factor in aging-related diseases. However, the role of SIRT6 in chondrocytes has not been fully explored. The purpose of this study was to examine the role of SIRT6 in human chondrocytes by inhibiting SIRT6 in vitro.

DESIGN

First, the localization of SIRT6 and proliferation cell nuclear antigen (PCNA) in human cartilages was examined by immunohistochemistry. Next, SIRT6 was depleted by RNA interference (RNAi), and the effect of SIRT6 depletion on changes in gene expression, protein levels, proliferation, and senescence in human chondrocytes was assessed. Furthermore, to detect DNA damage and telomere dysfunction, γH2AX foci and telomere dysfunction-induced foci (TIFs) were examined using immunofluorescence microscopy. The protein levels of two mediators for DNA damage induced-senescence, p16 and p21, were examined by western blotting.

RESULTS

Immunohistochemical analysis showed SIRT6 was preferentially expressed in the superficial zone chondrocytes and PCNA-positive cluster-forming chondrocytes in the osteoarthritic cartilage tissue samples. Real-time PCR analysis showed that matrix metalloproteinase 1 (MMP-1) and MMP-13 mRNA were significantly increased by SIRT6 inhibition. Moreover, SIRT6 inhibition significantly reduced proliferation and increased senescence associated β-galactosidase (SA-β-Gal)-positive chondrocytes; it also led to increased p16 levels. Immunofluorescence microscopy showed that γH2AX foci and TIFs were increased by SIRT6 inhibition.

CONCLUSION

Depletion of SIRT6 in human chondrocytes caused increased DNA damage and telomere dysfunction, and subsequent premature senescence. These findings suggest that SIRT6 plays an important role in the regulation of senescence of human chondrocytes.

Unravelling osteoarthritis-related synovial fibrosis: a step closer to solving joint stiffness

Synovial fibrosis is often found in OA, contributing heavily to joint pain and joint stiffness, the main symptoms of OA. At this moment the underlying mechanism of OA-related synovial fibrosis is not known and there is no cure available. In this review we discuss factors that have been reported to be involved in synovial fibrosis. The aim of the study was to gain insight into how these factors contribute to the fibrotic process and to determine the best targets for therapy in synovial fibrosis. In this regard, the following factors are discussed: TGF-β, connective tissue growth factor, procollagen-lysine, 2-oxoglutarate 5-dioxygenase 2, tissue inhibitor of metalloproteinase 1, A disintegrin and metalloproteinase domain 12, urotensin-II, prostaglandin F2α and hyaluronan.

Deletion of Panx3 Prevents the Development of Surgically Induced Osteoarthritis

Osteoarthritis (OA) is a highly prevalent, disabling joint disease with no existing therapies to slow or halt its progression. Cartilage degeneration hallmarks OA pathogenesis, and pannexin 3 (Panx3), a member of a novel family of channel proteins, is upregulated during this process. The function of Panx3 remains poorly understood, but we consistently observed a strong increase in Panx3 immunostaining in OA lesions in both mice and humans. Here, we developed and characterized the first global and conditional Panx3 knockout mice to investigate the role of Panx3 in OA. Interestingly, global Panx3 deletion produced no overt phenotype and had no obvious effect on early skeletal development. Mice lacking Panx3 specifically in the cartilage and global Panx3 knockout mice were markedly resistant to the development of OA following destabilization of medial meniscus surgery. These data indicate a specific catabolic role of Panx3 in articular cartilage and identify Panx3 as a potential therapeutic target for OA. Lastly, while Panx1 has been linked to over a dozen human pathologies, this is the first in vivo evidence for a role of Panx3 in disease.

KEY MESSAGE

Panx3 is localized to cartilage lesions in mice and humans. Global Panx3 deletion does not result in any developmental abnormalities. Mice lacking Panx3 are resistant to the development of osteoarthritis. Panx3 is a novel therapeutic target for the treatment of osteoarthritis.

α-Melanocyte-stimulating-hormone (α-MSH) modulates human chondrocyte activation induced by proinflammatory cytokines

Background

Alpha-melanocyte-stimulating-hormone (α-MSH) has marked anti-inflammatory potential. Proinflammatory cytokines are critical mediators of the disturbed cartilage homeostasis in osteoarthritis, inhibiting anabolic activities and increasing catabolic activities in chondrocytes. Since human chondrocytes express α-MSH receptors, we evaluated the role of the peptide in modulating chondrocyte production of pro-inflammatory cytokines, matrix metalloproteinases (MMPs), tissue inhibitors of MMPs (TIMPs), inducible nitric oxide synthase (iNOS) and nitric oxide (NO) in response to interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α).

Methods

Human articular chondrocytes were obtained from osteoarthritic joint cartilage from subjects undergoing hip routine arthroplasty procedures. The cells were cultured with or without α-MSH in the presence of IL-1β or TNF-α. Cell-free supernatants were collected and cells immediately lysed for RNA purification. Expression of cytokines, MMPs, TIMPs, iNOS was determined by Reverse Transcription Real-time Polymerase Chain Reaction and enzyme-linked immunosorbent assay. Griess reaction was used for NO quantification.

Results

Gene expression and secretion of IL-6, IL-8, MMP-3, MMP-13 were significantly increased in IL-1β or TNF-α-stimulated chondrocytes; α-MSH did not modify the release of IL-6 or IL-8 while the peptide significantly reduced their gene expression on TNF-α-stimulated cells. A significant inhibition of MMP3 gene expression and secretion from IL-1β or TNFα-stimulated chondrocytes was induced by α-MSH. On the other hand, α-MSH did not modify the release of MMP-13 by cytokine-stimulated chondrocyte but significantly decreased gene expression of the molecule on TNF-α-stimulated cells. Detectable amount of TIMP-3 and TIMP-4 were present in the supernatants of resting chondrocytes and a significant increase of TIMP-3 gene expression and release was induced by α-MSH on unstimulated cells. TIMP-3 secretion and gene expression were significantly increased in IL-1β-stimulated chondrocytes and α-MSH down-regulated gene expression but not secretion of the molecule. TIMP-4 gene expression (but not secretion) was moderately induced in IL-1β-stimulated chondrocytes with a down-regulation exerted by α-MSH. IL-1β and TNF-α were potent stimuli for NO production and iNOS gene expression by chondrocytes; no inhibition was induced by α-MSH on cytokine-stimulated NO production, while the peptide significantly reduced gene expression of iNOS.

Conclusions

Our results underscore a potential anti-inflammatory and chondroprotective activity exerted by α-MSH, increasing TIMP-3 gene expression and release on resting cells and down- modulating TNF-α-induced activation of human chondrocytes. However, the discrepancy between the influences exerted by α-MSH on gene expression and protein release as well as the difference in the inhibitory pattern exerted by α-MSH in TNF-α- or IL-1β-stimulated cells leave some uncertainty on the role of the peptide on chondrocyte modulation.

An ex vivo model using human osteoarthritic cartilage demonstrates the release of bioactive insulin-like growth factor-1 from a collagen-glycosaminoglycan scaffold

Biomimetic scaffolds hold great promise for therapeutic repair of cartilage, but although most scaffolds are tested with cells in vitro, there are very few ex vivo models (EVMs) where adult cartilage and scaffolds are co-cultured to optimize their interaction prior to in vivo studies. This study describes a simple, non-compressive method that is applicable to mammalian or human cartilage and provides a reasonable throughput of samples. Rings of full-depth articular cartilage slices were derived from human donors undergoing knee replacement for osteoarthritis and a 3 mm core of a collagen/glycosaminoglycan biomimetic scaffold (Tigenix, UK) inserted to create the EVM. Adult osteoarthritis chondrocytes were seeded into the scaffold and cultures maintained for up to 30 days. Ex vivo models were stable throughout experiments, and cells remained viable. Chondrocytes seeded into the EVM attached throughout the scaffold and in contact with the cartilage explants. Cell migration and deposition of extracellular matrix proteins in the scaffold was enhanced by growth factors particularly if the scaffold was preloaded with growth factors. This study demonstrates that the EVM represents a suitable model that has potential for testing a range of therapeutic parameters such as numbers/types of cell, growth factors or therapeutic drugs before progressing to costly pre-clinical trials. © 2015 The Authors. Cell Biochemistry and Function Published by John Wiley & Sons Ltd.

Correlating high-resolution magic angle spinning NMR spectroscopy and gene analysis in osteoarthritic cartilage

Osteoarthritis (OA) is a common multifactorial and heterogeneous degenerative joint disease, and biochemical changes in cartilage matrix occur during the early stages of OA before morphological changes occur. Thus, it is desired to measure regional biochemical changes in the joint. High-resolution magic angle spinning (HRMAS) NMR spectroscopy is a powerful method of observing cartilaginous biochemical changes ex vivo, including the concentrations of alanine and N-acetyl, which are markers of collagen and total proteoglycan content, respectively. Previous studies have observed significant changes in chondrocyte metabolism of OA cartilage via the altered gene expression profiles of ACAN, COL2A1 and MMP13, which encode aggrecan, type II collagen and matrix metalloproteinase 13 (a protein crucial in the degradation of type II collagen), respectively. Employing HRMAS, this study aimed to elucidate potential relationships between N-acetyl and/or alanine and ACAN, COL2A1 and/or MMP13 expression profiles in OA cartilage. Thirty samples from the condyles of five subjects undergoing total knee arthroplasty to treat OA were collected. HRMAS spectra were obtained at 11.7 T for each sample. RNA was subsequently extracted to determine gene expression profiles. A significant negative correlation between N-acetyl metabolite and ACAN gene expression levels was observed; this provides further evidence of N-acetyl as a biomarker of cartilage degeneration. The alanine doublet was distinguished in the spectra of 15 of the 30 specimens of this study. Alanine can only be detected with HRMAS NMR spectroscopy when the collagen framework has been degraded such that alanine is sufficiently mobile to form a distinguished peak in the spectrum. Thus, HRMAS NMR spectroscopy may provide unique localized measurements of collagenous degeneration in OA cartilage. The identification of imaging markers that could provide a link between OA pathology and chondrocyte metabolism will facilitate the development of more sensitive diagnostic techniques and will improve methods of monitoring treatment for patients suffering from OA.

The influence of osteophyte depiction in CT for patient-specific guided hip resurfacing procedures

PURPOSE

An accurate fit of a patient-specific instrument guide during an intervention is one of the critical factors affecting accuracy of the surgical procedure. In this study, we investigated how well osteophytes, which are abnormal bone growths that form along joints, are depicted in clinical preoperative CT scans and estimated the influence of such depiction errors on the intraoperative accuracy of the guide.

METHODS

In 34 hip resurfacing patients, 227 osteophyte surface points on the anterior aspect of the femoral neck were collected intraoperatively, using an optoelectronic navigation system. These points were registered to a preoperative CT scan of the patient, and distances between collected points and segmented virtual bone surface, as well as Hounsfield units for these points, were determined. We simulated the registration error of a patient-specific guide, using a modified registration algorithm, to test placement on the anterior aspect of the femoral neck without removing any osteophytes. This error was then applied to the surgical plan of the femoral central-pin position and orientation for evaluation.

RESULTS

The average distance between the collected points and the segmented surface was 2.6 mm. We estimated the average error for the entrance point of the central-pin to be 0.7 mm in the distal direction and 3.2 mm in the anterior direction. The average orientation error was 2.8° in anteversion.

CONCLUSIONS

The depiction of osteophytes in clinical preoperative CT scans for proximal femurs can be unreliable and can possibly result in significant intraoperative instrument alignment errors during image-guided surgeries.

Magnetic resonance analysis of loaded meniscus deformation: a novel technique comparing participants with and without radiographic knee osteoarthritis

OBJECTIVE

To establish a novel method of quantifying meniscal deformation using loaded MRI. More specifically, the goals were to evaluate the (1) accuracy, (2) inter-rater reliability, (3) intra-rater reliability, and (4) scan-rescan reliability. The secondary purpose of this experiment was to evaluate group differences in meniscal deformation in participants with and without radiographic knee OA.

MATERIALS AND METHODS

Weight-bearing 3-T MRIs of the knee in full extension and 30° of flexion were processed to create 3D models of meniscal deformation. Accuracy was assessed using a custom-designed phantom. Twenty-one participants either with or without signs of OA were evaluated, and another six participants (14 knees, one subject was scanned twice) underwent repeated imaging to assess scan-rescan reproducibility. Intraclass correlation coefficient (ICC), root-mean squared error (RMSE), and root-mean-square percent coefficient-of-variation (RMS%CV) analyses were performed. Exploratory comparisons were made between those with and without OA to evaluate potential group differences.

RESULTS

All variables were found to be accurate with RMSE ranging from 0.08 to 0.35 mm and 5.99 to 14.63 mm(2). Reproducibility of peak anterior-posterior meniscal deformation was excellent (ICC > 0.821; p < 0.013) with RMS%CV for intra-rater ranging from 0.06 to 1.53 % and 0.17 to 1.97 %, inter-rater ranging from 0.10 to 7.20 % and 3.95 to 18.53 %, and scan-rescan reliability ranging from 1.531 to 7.890 % and 4.894 to 9.142 %, for distance and area metric, respectively. Participants with OA were found to have significantly greater anterior horn movement of both the medial (p = 0.039) and lateral meniscus (p = 0.015), and smaller flexed medial meniscus outer area (p = 0.048) when compared to controls.

CONCLUSIONS

MRI-based variables of meniscus deformation were found to be valid in participants with and without OA. Significant differences were found between those with and without radiographic OA; further study is warranted.

The expression of vascular endothelial growth factor and Syndecan-4 in cartilage from osteoarthritic knees

Previous studies support the important role of vascular endothelial growth factor (VEGF) and syndecan-4 in the pathogenesis of osteoarthritis (OA). Both VEGF and syndecan-4 are expressed by chondrocytes and both are involved in the regulation of matrix metalloproteinase-3, resulting in the activation of aggrecanase II (ADAMTS-5), which is essential in the pathogenesis of OA. However, the relationship between VEGF and syndecan-4 has not been established. As a pilot study, we assayed the expression of VEGF and syndecan-4 in cartilage samples and cultured chondrocytes from osteoarthritic knee joints and analysed the relationship between these two factors. Specimens were collected from 21 female patients (29 knees) who underwent total knee replacement due to severe medial OA of the knee (Kellgren-Lawrence grade 4). Articular cartilage samples, obtained from bone and cartilage excised during surgery, were analysed and used for chondrocyte culture. We found that the levels of expression of VEGF and syndecan-4 mRNA did not differ significantly between medial femoral cartilage with severe degenerative changes and lateral femoral cartilage that appeared grossly normal (p = 0.443 and 0.622, respectively). Likewise, the levels of expression of VEGF and syndecan-4 mRNA were similar in cultured chondrocytes from medial and lateral femoral cartilage. The levels of expression of VEGF and syndecan-4 mRNAs were significantly and positively correlated in cartilage explant (r = 0.601, p = 0.003) but not in cultured chondrocytes. These results suggest that there is a close relationship between VEGF and syndecan-4 in the cartilage of patients with OA. Further studies are needed to determine the exact pathway by which these two factors interact in the pathogenesis of OA.

Disturbed cartilage and joint homeostasis resulting from a loss of mitogen-inducible gene 6 in a mouse model of joint dysfunction

OBJECTIVE

Mitogen-inducible gene 6 (MIG-6) regulates epidermal growth factor receptor (EGFR) signaling in synovial joint tissues. Whole-body knockout of the Mig6 gene in mice has been shown to induce osteoarthritis and joint degeneration. To evaluate the role of chondrocytes in this process, Mig6 was conditionally deleted from Col2a1-expressing cell types in the cartilage of mice.

METHODS

Bone and cartilage in the synovial joints of cartilage-specific Mig6-deleted (knockout [KO]) mice and control littermates were compared. Histologic staining and immunohistochemical analyses were used to evaluate joint pathology as well as the expression of key extracellular matrix and regulatory proteins. Calcified tissue in synovial joints was assessed by micro-computed tomography (micro-CT) and whole-skeleton staining.

RESULTS

Formation of long bones was found to be normal in KO animals. Cartilage thickness and proteoglycan staining of articular cartilage in the knee joints of 12-week-old KO mice were increased as compared to controls, with higher cellularity throughout the tissue. Radiopaque chondro-osseous nodules appeared in the knees of KO animals by 12 weeks of age and progressed to calcified bone-like tissue by 36 weeks of age. Nodules were also observed in the spine of 36-week-old animals. Erosion of bone at ligament entheses was evident by 12 weeks of age, by both histologic and micro-CT assessment.

CONCLUSION

MIG-6 expression in chondrocytes is important for the maintenance of cartilage and joint homeostasis. Dysregulation of EGFR signaling in chondrocytes results in anabolic activity in cartilage, but erosion of ligament entheses and the formation of ectopic chondro-osseous nodules severely disturb joint physiology.

The effects of different molecular weight chondroitin-4-sulfates in chondrocyte pellet culture

For this study, we cultured chondrocyte pellets in Dulbecco's modified Eagle's medium plus a 2 % fetal bovine serum medium, and treated them with 2- to 8-mer oligosaccharides of chondroitin sulfate A to examine the effects of these oligosaccharides on the differentiation and protection of chondrocytes. We found low-molecular-weight CSAs to increase the ratio of the gene expression levels of collagen II/collagen I of chondrocytes from the first day up to 14 days after culture compared with those under a CSA-free medium. Moreover, low-molecular-weight CSAs inhibited the expression of matrix metalloproteinases and peptidases, and stimulated an endogenous tissue inhibitor of metalloproteinases. The dp-8 (8-mer) CSA yielded the most effective response among promoting collagen type II protein secretions compared with other groups.

Effect of self-assembled peptide-mesenchymal stem cell complex on the progression of osteoarthritis in a rat model

PURPOSE

To evaluate the efficacy of mesenchymal stem cells (MSCs) encapsulated in self-assembled peptide (SAP) hydrogels in a rat knee model for the prevention of osteoarthritis (OA) progression.

MATERIALS AND METHODS

Nanostructured KLD-12 SAPs were used as the injectable hydrogels. Thirty-three Sprague Dawley rats were used for the OA model. Ten rats were used for the evaluation of biotin-tagged SAP disappearance. Twenty-three rats were divided into four groups: MSC (n=6), SAP (n=6), SAP-MSC (n=6), and no treatment (n=5). MSCs, SAPs, and SAP-MSCs were injected into the knee joints 3 weeks postsurgery. Histologic examination, immunofluorescent staining, measurement of cytokine levels, and micro-computed tomography analysis were conducted 6 weeks after injections. Behavioral studies were done to establish baseline measurements before treatment, and repeated 3 and 6 weeks after treatment to measure the efficacy of SAP-MSCs.

RESULTS

Concentration of biotinylated SAP at week 1 was not significantly different from those at week 3 and week 6 (P=0.565). Bone mineral density was significantly lower in SAP-MSC groups than controls (P=0.002). Significant differences in terminal deoxynucleotidyl transferase deoxyuridine triphosphate nick-end labeling staining between the control group and all other groups were observed. Caspase-8, tissue inhibitor of metalloproteinases 1, and matrix metalloproteinase 9 were diffusely stained in controls, whereas localized or minimal staining was observed in other groups. Modified Mankin scores were significantly lower in the SAP and SAP-MSC groups than in controls (P=0.001 and 0.013). Although not statistically significant, synovial inflammation scores were lower in the SAP (1.3±0.3) and SAP-MSC (1.3±0.2) groups than in controls (2.6±0.2). However, neither the cytokine level nor the behavioral score was significantly different between groups.

CONCLUSION

Injection of SAP-MSC hydrogels showed evidence of chondroprotection, as measured by the histologic grading and decreased expression of biochemical markers of inflammation and apoptosis. It also lowered subchondral bone mineral density, which can be increased by OA. This suggests that the SAP-MSC complex may have clinical potential to inhibit OA progression.

Synovitis in knee osteoarthritis assessed by contrast-enhanced magnetic resonance imaging (MRI) is associated with radiographic tibiofemoral osteoarthritis and MRI-detected widespread cartilage damage: the MOST study

OBJECTIVE

To examine the cross-sectional association of whole-knee synovitis assessed by contrast-enhanced magnetic resonance imaging (CEMRI) with radiographic tibiofemoral osteoarthritis (OA), non-CEMRI-assessed cartilage damage, and meniscal status.

METHODS

Multicenter Osteoarthritis Study (MOST) is a cohort study of people with or at high risk of knee OA. Subjects are a subset of MOST who volunteered for both CEMRI and non-CEMRI. Using CEMRI, synovitis was assessed at 11 sites and graded 0-2 at each site. Presence of "whole-knee synovitis" was defined as the synovitis score of ≥ 1 at any site from each knee. Cartilage and meniscal damage was evaluated using non-CEMRI based on the Whole Organ MRI Score. Logistic regression was used to assess associations of synovitis with radiographic OA (Kellgren-Lawrence grade ≥ 2), widespread cartilage damage, and meniscal damage, adjusting for age, sex, and body mass index (BMI). Additional analyses were performed excluding subjects who had chondrocalcinosis on radiography and those taking antiinflammatory medications.

RESULTS

Four hundred four subjects were included (mean age 58.8 ± 7.0 yrs, BMI 29.6 ± 4.9 kg/m(2), 45.5% women). On CEMRI, the maximum synovitis score across 11 sites in each knee was 0 in 106 knees (26.2%), 1 in 135 (33.4%), and 2 in 163 (40.4%). Synovitis was associated with radiographic OA [adjusted OR (aOR) 3.25, 95% CI 1.98-5.35] and widespread cartilage damage (aOR 1.91, 95% CI 1.24-2.92). Severe meniscal damage showed a borderline significant association with synovitis (aOR 1.74, 95% CI 0.99-3.04). Additional analyses as described did not notably change the results.

CONCLUSION

CEMRI-detected synovitis is strongly associated with tibiofemoral radiographic OA and MRI-detected widespread cartilage damage.