Variation patterns of two degradation enzyme systems in articular cartilage in different stages of osteoarthritis: regulation by dehydroepiandrosterone

Gender-Related Aspects in Osteoarthritis Development and Progression: A Review

Osteoarthritis (OA) is a common degenerative joint disease treated mostly symptomatically before approaching its definitive treatment, joint arthroplasty. The rapidly growing prevalence of OA highlights the urgent need for a more efficient treatment strategy and boosts research into the mechanisms of OA incidence and progression. As a multifactorial disease, many aspects have been investigated as contributors to OA onset and progression. Differences in gender appear to play a role in the natural history of the disease, since female sex is known to increase the susceptibility to its development. The aim of the present review is to investigate the cues associated with gender by analyzing various hormonal, anatomical, molecular, and biomechanical parameters, as well as their differences between sexes. Our findings reveal the possible implications of gender in OA onset and progression and provide evidence for gaps in the current state of art, thus suggesting future research directions.

Transcriptome Analysis Reveals Novel Genes Associated with Cartilage Degeneration in Posttraumatic Osteoarthritis Progression

OBJECTIVE

The current therapeutic strategy for posttraumatic osteoarthritis (PTOA) focuses on early intervention to attenuate disease progression, preserve joint function, and defer joint replacement timing. Sequential transcriptomic changes of articular cartilage in a rat model were investigated to explore the molecular mechanism in early PTOA progression.

DESIGN

Anterior cruciate ligament transection and medial meniscectomy (ACLT + MMx)-induced PTOA model was applied on male Wistar rats. Articular cartilages were harvested at time 0 (naïve), 2 week, and 4 weeks after surgery. Affymetrix Rat genome 230 2.0 array was utilized to analyze the gene expression changes of articular cartilages.

RESULTS

We identified 849 differentially expressed genes (DEGs) at 2 weeks and 223 DEGs at 4 weeks post-ACLT + MMx surgery compared with time 0 (naïve group). Gene ontology and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis were performed to gain further insights from these DEGs. 22 novel genes and 1 novel KEGG pathway (axon guidance) in cartilage degeneration of osteoarthritis were identified. Axon guidance molecules-Gnai1, Sema4d, Plxnb1, and Srgap2 commonly dysregulated in PTOA progression. Gnai1 gene showed a concordant change in protein expression by immunohistochemistry staining.

CONCLUSIONS

Our study identified 22 novel dysregulated genes and axon guidance pathway associated with articular cartilage degeneration in PTOA progression. These findings provide the potential candidates of biomarkers and therapeutic targets for further investigation.

Sex Steroids and Osteoarthritis: A Mendelian Randomization Study

Objective

Sex steroids are thought to contribute to the pathogenesis of osteoarthritis (OA). This study investigated the causal role of sex steroids in site- and sex-specific OA and risk of joint replacement surgery using the Mendelian randomization (MR) method.

Methods

Instrumental variables for estradiol, dehydroepiandrosterone sulfate, testosterone (T), and dihydrotestosterone (DHT) were selected. We used the inverse variance weighting (IVW) approach as the main MR method to estimate causal effects based on the summary-level data for OA and joint replacement surgery from genome-wide association studies (GWAS).

Results

A positive causal association was observed between serum T level and risks of hip OA (odds ratio [OR]=1.558, 95% confidence interval [CI]: 1.193-2.034; P=0.001) and hip replacement (OR=1.013, 95% CI: 1.008-1.018; P=2.15×10-8). Serum DHT level was also positively associated with the risk of hip replacement (OR=1.011, 95% CI: 1.006-1.015; P=4.03×10-7) and had potential causality with hip OA (OR=1.398, 95% CI: 1.054-1.855; P=0.020).

Conclusions

Serum T and DHT levels may play causal roles in the development of hip OA and contribute to the risk of hip replacement, although the underlying mechanisms require further investigation.

Dehydroepiandrosterone and age-related musculoskeletal diseases: Connections and therapeutic implications

Musculoskeletal disorders related to ageing are one of the most common causes of mortality and morbidity among elderly individuals worldwide. The typical constitutive components of the musculoskeletal system, including bone, muscle, and joints, gradually undergo a process of tissue loss and degeneration as a result of life-long mechanical and biological stress, ultimately leading to the onset of a series of age-related musculoskeletal diseases, including osteoporosis (OP), sarcopenia, and osteoarthritis (OA). Dehydroepiandrosterone (DHEA), a precursor of androgen secreted mainly by the adrenal gland, has attracted much attention as a marker for senescence due to its unique age-related changes. This pre-hormone has been publicly regarded as an "antidote for ageing" because of its favourable effect against a wide range of age-related diseases, such as Alzheimer disease, cardiovascular diseases, immunosenescence and skin senescence, though its effect on age-related musculoskeletal diseases has been explored to a lesser extent. In the present review, we summarized the action of DHEA against OP, sarcopenia and OA. Extensive detailed descriptions of the pathogenesis of each of these musculoskeletal disorders are beyond the scope of this review; instead, we aim to highlight the association of changes in DHEA with the processes of OP, sarcopenia and OA. A special focus will also be placed on the overlapping pathogeneses among these three diseases, and the molecular mechanisms underlying the action of DHEA against these diseases are discussed or postulated.

Potential of dehydroepiandrosterone in modulating osteoarthritis-related pain

Osteoarthritis (OA) is the most common form of degenerative arthropathy, and the primary symptom is chronic joint pain. Dehydroepiandrosterone (DHEA) exerts a chondroprotective effect against OA and has been reported to have potent structure-modifying effects on osteoarthritic cartilage, thereby attenuating disease progression. However, the ability of DHEA to modulate OA-related pain has not yet been verified. Recent evidence suggests that there may be a link between the pharmacological effects of DHEA and pain generation. For example, DHEA synthesized in the adrenal gland interferes directly with nerve growth factor (NGF) receptors, a major biochemical contributor to peripheral hypersensitivity. Similarly, endogenous DHEA produced in the spinal cord exerts a regulatory effect on nociception in neuropathic rats. In this short review, we discuss recent studies concerning crucial signalling cascades and molecular mechanisms involved in pain generation as well as the potential link between DHEA activity and nociception. Particular attention is given to the putative molecular mechanisms underlying the favourable efficacy of DHEA against pain generation. Elucidating the molecular mechanisms of DHEA against osteoarthritic pain may pave the way for the discovery and development of novel anti-OA drugs, as effective drugs for OA treatment are not currently available.

Dehydroepiandrosterone: Molecular mechanisms and therapeutic implications in osteoarthritis

Dehydroepiandrosterone (DHEA), a 19-carbon steroid hormone primarily synthesized in the adrenal gland, exerts a chondroprotective effect against osteoarthritis (OA) and has been considered an effective candidate of disease-modifying OA drugs (DMOADs) that slow disease progression. We and others previously demonstrated that DHEA exerted a beneficial effect on osteoarthritic cartilage by positively modulating the balance between anabolic and catabolic factors (e.g., MMPs/TIMP-1, ADAMTS/TIMP-3 and cysteine proteinases/cystatin C), inhibiting catabolic signaling pathways (e.g., Wnt/β-catenin), and suppressing proinflammatory cytokines-mediated low-grade synovial inflammation (e.g., IL-1β). However, the full picture of the pharmacological molecular mechanism(s) underlying the activity of DHEA against OA is still incomplete, and a comprehensive and up-to-date review article in this field is unavailable. In this review, recent findings (apart from the well documented pathogenesis of OA) regarding disease-related mechanisms involving low grade synovial inflammation, cartilage matrix stiffness, chondrocyte autophagy and the roles of a variety of catabolic cellular signaling pathways are discussed. Moreover, the possible relationship between these disease-related mechanisms and DHEA action is discussed. Emerging evidence from in vivo and in vitro studies were scrutinized and are concisely presented to demonstrate the investigational and putative mechanisms underlying the anti-OA potential of DHEA.

Dehydroepiandrosterone and Experimental Osteoarthritis

Despite an increased understanding of the pathogenesis of osteoarthritis (OA) and the availability of a number of drugs designed to ameliorate its symptoms, a successful disease-modifying therapy remains elusive. Recent lines of evidence suggest that dehydroepiandrosterone (DHEA), a 19-carbon steroid hormone classified as an adrenal androgen, exerts a chondroprotective effect in OA patients, and it has been proven to be an effective DMOAD candidate that slows OA progression. However, the exact mechanisms underlying its anti-OA effect is largely unknown. This review summarizes emerging observations from studies of cell biology, preclinical animal studies, and preliminary clinical trials and describes the findings of investigations on this topic to develop an initial blueprint of the mechanisms by which DHEA slows OA progression. Presently, studies on DMOADs are increasing in importance but have met limited success. Encouragingly, the current data on DHEA are promising and may prove that DHEA-based treatment is efficacious for preventing and slowing human OA progression.

Overexpression of cystatin C in synovium does not reduce synovitis or cartilage degradation in established osteoarthritis

Introduction

Cathepsin K (catK) expression is increased in cartilage, bone and synovium during osteoarthritis (OA). To study the role of catK expression and elevated cathepsin activity in the synovium on cartilage destruction in established OA, we overexpressed cystatin C (cysC), a natural cysteine protease inhibitor, in the synovium of rabbit OA joints.

Methods

The ability of cysC to inhibit activity of cathepsins in rabbit OA synovium lysates was tested in vitro using protease activity assay. In vivo, the tissue localization of recombinant adeno-associated virus (rAAV) with LacZ gene after intra-articular injection was determined by β-galactosidase staining of rabbit joints 4 weeks later. To inhibit cathepsin activity in the synovium, a rAAV2-encoding cysC was delivered intra-articularly into rabbit joints 4 weeks after OA was induced by anterior cruciate ligament transection (ACLT). Seven weeks postinjection, endogenous catK and cysC levels as well as the vector-derived cysC expression in the synovium of normal and OA joints were examined by RNA quantification. Synovial cathepsin activity and catK, catB and catL protein levels were determined by activity and Western blot analyses, respectively. Synovitis and cartilage degradation were evaluated by histopathological scoring.

Results

In vitro, the ability of cysC to efficiently inhibit activity of purified catK and OA-induced cathepsins in rabbit synovial lysates was demonstrated. In vivo, the intra-articular delivery of rAAV2/LacZ showed transduction of mostly synovium. Induction of OA in rabbit joints resulted in fourfold increase in catK mRNA compared to sham controls while no change was detected in endogenous cysC mRNA levels in the synovium. Protein levels for catK, catB and catL were also increased in the synovium with a concomitant fourfold increase in cathepsin activity. Joints treated with rAAV2/cysC showed both detection of vector genomes and vector-derived cysC transcripts in the synovium. Production of functional cysC by the vector was demonstrated by complete block of cathepsin activity in the synovium. However, this did not decrease synovitis, bone sclerosis or progression of cartilage degradation.

Conclusions

Increased production of natural cathepsin inhibitor, cysC, in OA synovium does not alleviate synovitis or cartilage pathology during a preexisting OA.

Shear stress modulates macrophage-induced urokinase plasminogen activator expression in human chondrocytes

Introduction

Synovial macrophages, which can release proinflammatory factors, are responsible for the upregulation of cartilage-breakdown proteases and play critical roles in cartilage degradation during the progression of osteoarthritis (OA). In addition, shear stress exerts multifunctional effects on chondrocytes by inducing the synthesis of catabolic or anabolic genes. However, the interplay of macrophages, chondrocytes, and shear stress during the regulation of cartilage function remains poorly understood. We investigated the mechanisms underlying the modulation of human chondrocyte urokinase plasminogen activator (uPA) expression by macrophages and shear stress.

Methods

Human chondrocytes were stimulated by peripheral blood-macrophage- conditioned medium (PB-MCM), or exposure of chondrocytes cultured in PB-MCM to different levels of shear stress (2 to 20 dyn/cm²). Real-time polymerase chain reaction was used to analyze uPA gene expression. Inhibitors and small interfering RNA were used to investigate the mechanism for the effects of PB-MCM and shear stress in chondrocytes.

Results

Stimulation of human chondrocytes with PB-MCM was found to induce uPA expression. We demonstrated that activation of the JNK and Akt pathways and NF-κB are critical for PB-MCM-induced uPA expression. Blocking assays by using IL-1ra further demonstrated that IL-1β in PB-MCM is the major mediator of uPA expression in chondrocytes. PB-MCM-treated chondrocytes subjected to a lower level of shear stress showed inhibition of MCM-induced JNK and Akt phosphorylation, NF-κB activation, and uPA expression. The PB-MCM-induced uPA expression was suppressed by AMP-activated protein kinase (AMPK) agonist. The inhibitor or siRNA for AMPK abolished the shear-mediated inhibition of uPA expression.

Conclusions

These data support the hypothesis that uPA upregulation stimulated by macrophages may play an active role in the onset of OA and in the shear-stress protection against this induction.

The chondroprotective effects of dehydroepiandrosterone probably exerted by its conversion to estradiol

The sex hormone precursor dehydroepiandrosterone (DHEA), which can be converted into estradiol by the enzyme aromatase, has a protective role against osteoarthritis (OA). To determine whether the protective effects of DHEA are dependent on its conversion to estradiol, the aromatase inhibitor letrozole and/or the estrogen receptor inhibitor fulvestrant were administered in the presence of DHEA in both interleukin 1β (IL-1β)-induced rabbit chondrocytes and a rabbit anterior cruciate ligament transaction (ACLT) model of OA. Expression levels of matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinase-1 (TIMP-1) were used to monitor these effects. Expression of MMP-3 and MMP-13 increased in both DHEA-treated chondrocytes and cartilage in the presence of letrozole and/or fulvestrant, while the expression of TIMP-1 and collagen type II (Col-II) decreased. Our findings suggest that the effects of DHEA may be mediated by its conversion to estradiol.

Perinatal xenohormone exposure impacts sweet preference and submandibular development in male rats

OBJECTIVE

To determine the effect of perinatal exposure to low doses of genistein and/or vinclozolin on submandibular salivary gland (SSG) development in juvenile and adult male rats and to establish a link with sweet preference.

MATERIAL AND METHODS

Female rats received orally (1 mg kg(-1) body weight/day) genistein and vinclozolin, alone or in combination, from the first gestational day up to weaning. Sweet preference was assessed at weaning and in adulthood in male offspring; submandibular glands were then collected to study the morphogenesis and mRNA expression of steroid receptors, growth factors and taste related proteins.

RESULTS

Exposure to genistein and/or vinclozolin resulted in a higher saccharin intake on postnatal day 25 (P < 0.05) linked to a higher number of pro-acinar cells (P < 0.01) and mRNA expression of progesterone receptor, growth factors and gustine (P < 0.01). These increases disappeared in adulthood, but mRNA expressions of sex hormone receptors and growth factors were strongly repressed in all treated groups (P < 0.01).

CONCLUSION

Our findings confirm that the SSG are target for xenohormones and provide evidence that perinatal exposure to low doses of genistein and/or vinclozolin could simultaneously disrupt not only the salivary gland prepubertal development and sweet intake but also endocrine gene mRNA expression later in life.

Trichostatin A inhibits expression of cathepsins in experimental osteoarthritis

The aim of this study was to investigate the effects of trichostatin A (TSA) on expression of cathepsins in cartilage in experimental osteoarthritis (OA). OA was induced in 18 rabbits by bilateral anterior cruciate ligament transection (ACLT). Four weeks after surgery, rabbits received intra-articular injection with TSA dissolved in the dimethylsulphoxide (DMSO) in the right knees and DMSO in the left knees once a week for 5 weeks. Rabbits were killed 7 days after the last injection. The knee joints were assessed by morphological and histological examination. Messenger RNA expression of cathepsins K, B, L, S and cystatin C was studied by real-time PCR. TSA inhibited the expression of cathepsins K, B, L, S and cystatin C accompanied with the less degradation in cartilage. The results suggest that TSA exhibits protective effects against cartilage degradation in rabbits with OA and the effects may be associated with the inhibition of cathepsins.

Thymoquinone inhibits matrix metalloproteinase expression in rabbit chondrocytes and cartilage in experimental osteoarthritis

Thymoquinone (TQ) is the main constituent of Nigella sativa oil, which has been traditionally used against arthritis in the Middle East. In this study, we investigated the effect of TQ against matrix metalloproteinase (MMP) expression in both rabbit chondrocytes and animal mode of osteoarthritis (OA) induced by anterior cruciate ligament transection and tested whether or not nuclear factor kappa B (NF- κB) was involved in this process. TQ down-regulated MMP-1, MMP-3 and MMP-13 expression and up-regulated tissue inhibitors of metalloproteinase-1 expression as assessed by quantitative realtime polymerase chain reaction. In addition, NF- κB p65 protein level as well as its translocation induced by interleukin-1 β were inhibited by TQ. Our findings suggest the potential of TQ in the treatment of OA.

Anti-arthritic effects of chlorogenic acid in interleukin-1β-induced rabbit chondrocytes and a rabbit osteoarthritis model

Cartilage degradation is one of the pathological changes of osteoarthritis (OA), and accumulating evidence suggests an excess of matrix metalloproteinases (MMPs) plays a role in this cartilage breakdown. Here, we investigated the effects of chlorogenic acid (CGA) on the mRNA and protein expression of MMPs in interleukin (IL)-1β-induced rabbit chondrocytes and evaluated the in vivo effects of CGA in experimental OA induced by anterior cruciate ligament transection (ACLT) in rabbits. Using quantitative real-time PCR and ELISA to investigate the expression levels of MMP-1, MMP-3, MMP-13, and tissue inhibitors of metalloproteinase-1(TIMP-1) in IL-1β-induced rabbit chondrocytes, we showed that CGA inhibits the expression of these MMPs while increasing TIMP-1 expression, at both the mRNA and protein levels. In addition, IL-1β-induced activation of nuclear factor kappa B (NF-κB) and the degradation of inhibitor of κB (IκB)-α were suppressed by CGA. In rabbits, CGA decreased cartilage degradation as assessed by morphological and histological analyses. The down-regulation of MMP-1, MMP-3, and MMP-13 expression and up-regulation of TIMP-1 expression were also detected in CGA-treated cartilage compared with vehicle-treated cartilage, confirming these findings in an in vivo model. Taken together, these findings indicate that CGA may be considered as a possible candidate agent in the treatment of OA.

withdrawn The anti-inflammatory effects of apocynin, inhibitor of NADPH oxidase, contrasting hyaluronic acid on articular cartilage during the development of osteoarthritis in a rabbit model

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