Osteoarthritis pathogenesis: a review of molecular mechanisms

Protective Effects of Hydrogen-Rich Water Against Cartilage Damage in a Rat Model of Osteoarthritis by Inhibiting Oxidative Stress, Matrix Catabolism, and Apoptosis

Background

The aim of this study was to investigate the mechanisms underlying the potential effects of hydrogen-rich water (HW) on articular cartilage in a rat osteoarthritis (OA) model.

Material/Methods

A rat model of OA was established using the modified Hulth method, and rats were forced to exercise for 30 min every day 1 week after surgery for 7 weeks. Mankin’s method was used to score the severity of OA. The animals were assigned into the OA group, OA+HW group, and sham operation group. After 8 weeks, the animals in the OA group had a Mankin score >8 points, and HW was administered into the knee joint. After 2 weeks of treatment, articular cartilage was obtained for pathological examination, consisting of hematoxylin and eosin, toluidine blue, and Hoechst staining, as well as quantitative real-time PCR and Western blot analyses. This combination of pharmacological and molecular biological analyses was performed to examine the mechanism underlying the protective effect of HW on articular cartilage.

Results

The antioxidant effects of HW suppressed oxidative damage, which may have aided the inhibition of ECM-degrading enzymes (MMP3, MMP13, ADAMT4, and ADAMT5), the upregulation of Col II and aggrecan expression, and the downregulation of COX-2, iNOS, and NO expression. The results of HE staining indicated intra-articular treatment of HW attenuated cartilage degradation. However, Hoechst staining in the OA group indicated the nuclei of the fragmented chondrocytes were condensed compared to the sham operation group, and this effect was inhibited by HW.

Conclusions

HW showed a protective effect against the progression of OA in an animal model, which may have been mediated by its anti-oxidant and anti-apoptotic activities.

Functional role of hedgehog pathway in osteoarthritis

The hedgehog signalling pathway is one of the key regulators of metazoan development, and it plays an important role in the regulation of a variety of developmental and physiological processes. But it is aberrantly activated in many human diseases, including osteoarthritis (OA). In this study, we have reviewed the association of hedgehog signalling pathway in the development and progression of OA and evaluated the efforts to target this pathway for the prevention of OA. Usually in OA, activation of hedgehog induces up-regulation of the expression of hypertrophic markers, including type X collagen, increases production of nitric oxide and prostaglandin E2, several matrix-degrading enzymes including matrix metalloproteinase and a disintegrin and metalloproteinase with thrombospondin motifs in human knee joint cartilage leading to cartilage degeneration, and thus contributes in OA. Targeting hedgehog signalling might be a viable strategy to prevent or treat OA. Chemical inhibitors of hedgehog signalling is promising, but they cause severe side effects. Knockdown of HH gene is not an option for OA treatment in humans because it is not possible to delete HH in larger animals. Efficient knockdown of HH achieved by local delivery of small interfering RNA in future studies utilizing large animal OA models might be a more efficient approach for the prevention of OA. However, it remains a major problem to develop one single scaffold due to the different physiological functions of cartilage and subchondral bones possess. More studies are necessary to identify selective inhibitors for efficiently targeting the hedgehog pathway in clinical conditions.

Oral administration of N-acetyl cysteine prevents osteoarthritis development and progression in a rat model

The number of osteoarthritis patients is increasing with the rise in the number of elderly people in developed countries. Osteoarthritis, which causes joint pain and deformity leading to loss of activities of daily living, is often treated surgically. Here we show that mechanical stress promotes accumulation of reactive oxygen species (ROS) in chondrocytes in vivo, resulting in chondrocyte apoptosis and leading to osteoarthritis development in a rat model. We demonstrate that mechanical stress induces ROS accumulation and inflammatory cytokine expression in cultured chondrocytes in vitro and that both are inhibited by treatment with the anti-oxidant N-acetyl cysteine (NAC). In vivo, osteoarthritis development in a rat osteoarthritis model was also significantly inhibited by oral administration of NAC. MMP13 expression and down-regulation of type II collagen in chondrocytes, both of which indicate osteoarthritis, as well as chondrocyte apoptosis in osteoarthritis rats were inhibited by NAC. Interestingly, osteoarthritis development in sham-operated control sides, likely due to disruption of normal weight-bearing activity on the control side, was also significantly inhibited by NAC. We conclude that osteoarthritis development in rats is significantly antagonized by oral NAC administration. Currently, no oral medication is available to prevent osteoarthritis development. Our work suggests that NAC may represent such a reagent and serve as osteoarthritis treatment.

Quercetin alleviates rat osteoarthritis by inhibiting inflammation and apoptosis of chondrocytes, modulating synovial macrophages polarization to M2 macrophages

Osteoarthritis (OA) is a progressive joint disorder that is primarily characterized by the degeneration and destruction of the articular cartilage. Cartilage matrix degradation, production of proinflammatory mediators, chondrocyte apoptosis and activation of macrophages in the synovial are involved in OA pathogenesis. Current non-surgical therapies for OA mainly aim at relieving pain but can barely alleviate the progression of OA. Quercetin, a naturally occurring flavonoid has shown potent anti-inflammatory effects, however, its effects and underlying mechanisms on OA have seldom been systematically illuminated. In this study, we explored the protective effects of quercetin on repairing OA-induced cartilage injuries and its possible mechanisms. In vitro, quercetin remarkably suppressed the expression of matrix degrading proteases and inflammatory mediators, meantime promoted the production of cartilage anabolic factors in interleukin-1β-induced (IL-1β) rat chondrocytes. In addition, quercetin exhibited anti-apoptotic effects by decreasing intracellular reactive oxygen species (ROS), restoring mitochondrial membrane potential (MMP) and inhibiting the Caspase-3 pathway in apoptotic rat chondrocytes. Moreover, quercetin induced M2 polarization of macrophages and upregulated the expression of transforming growth factor β (TGF-β) and insulin-like growth factor (IGF), which in turn created a pro-chondrogenic microenvironment for chondrocytes and promoted the synthesis of glycosaminoglycan (GAG) in chondrocytes. In vivo, intra-articular injection of quercetin alleviated the degradation of the cartilage and the apoptosis of chondrocytes in a rat OA model. Moreover, the expression of TGF-β1 and TGF-β2 in the synovial fluid and the ratio of M2 macrophages in the synovial membrane were elevated. In summary, our study proves that quercetin exerts chondroprotective effects by inhibiting inflammation and apoptosis of chondrocytes, modulating synovial macrophages polarization to M2 macrophages and creating a pro-chondrogenic environment for chondrocytes to enhance cartilage repair under OA environment. It is suggested that quercetin may serve as a potential drug for OA treatment.

Gene Expression Profiles of Peripheral Blood Monocytes in Osteoarthritis and Analysis of Differentially Expressed Genes

Background

There is little understanding of the molecular processes involved in the pathogenesis of osteoarthritis, limiting early diagnosis and effective treatment of OA. Use of genechips can provide insights into the molecular pathogenesis of diseases. In this study, determination of gene expression profiles of osteoarthritis peripheral blood mononuclear cells will allow exploration of the molecular pathogenesis of OA and find out more candidate biomarkers and potential drug targets of OA.

Result

A total of 1231 DEGs were screened out including 791 upregulated DEGs and 440 downregulated DEGs. The most significant upregulated DEG was RPL38, which may inhibit chondrocyte differentiation and synthesis of the extracellular matrix. PIK3CA, PIK3CB, PIK3CD, PIK3R1, MAPK14, IL1A, JUND, FOSL2, and PPP3CA were the gene symbols of the osteoclast differentiation pathway which was the most significant pathway enriched by DEGs. However, the MAPK signaling pathway occupied the core position of all the pathways which can regulate apoptosis, cell cycle, wnt signaling pathway, p53 signaling pathway, and phosphatidylinositol signaling system. Furthermore, PI3Ks may regulate IL1A, JUND, FOSL2 and PPP3CA through the MAPK signaling pathway.

Conclusion

These identified DEGs and pathways may be novel biomarkers to monitor the changes of OA and can be a potential drug target for the treatment of OA.

Stromal cell-derived factor-1 as a potential therapeutic target for osteoarthritis and rheumatoid arthritis

With age, joints become subject to chronic inflammatory processes that lead to degeneration of articular cartilage. Although multifactorial, cytokines have been shown to play a role in the pathogenesis of these chronic disease states. Stromal cell-derived factor 1 (SDF-1) is a chemokine that has been shown to be active in homeostatic mechanisms and developmental processes throughout the body, such as endochondral bone formation. SDF-1 plays a role in the transition from cartilage to bone. Although it has been shown to be a factor in normal development, it has also been shown to involve in the pathogenesis of rheumatoid arthritis (RA) and osteoarthritis (OA). In RA, SDF-1 has been shown to stimulate the recruitment of proinflammatory cells, as well as osteoclasts to the synovium, aiding in the facilitation of synovial degradation. Similarly, in OA, SDF-1 has been shown to regulate key proteins involved in the degradation of the cartilage of the joint. Because of its role in degenerative joint disease, SDF-1 has been investigated as a potential therapeutic target. Animal studies have been employing SDF-1 inhibitors, such as AMD3100 and T140, to study their effects on attenuating degenerative joint disease. These studies have shown promising results in slowing the progression of cartilage degradation and could potentially be used as therapeutic target for humans OA and RA.

Variations of Wnt/β-catenin pathway-related genes in susceptibility to knee osteoarthritis: A three-centre case-control study

Excessive activation of the Wnt signalling pathway in the articular cartilage is demonstrated to be related to the onset and severity of osteoarthritis (OA). However, few studies have investigated the association between variants in Wnt‐pathway‐related genes and the risk of OA by searching Pubmed and EMBASE. Totally, 471 knee OA patients and 532 controls were recruited from three hospitals to evaluate the associations of five genetic variants (rs61735963, rs2908004, rs10795550, rs1799986 and rs1127379) with the risk of knee OA. These polymorphisms were genotyped through polymerase chain reaction and Sanger sequencing. Genetic risk scores (GRSs) were calculated to evaluate the combined effect of these genetic variants. No significant association was found between OA risk and polymorphisms (rs61735963, rs10795550 or rs1127379). However, WNT16 rs2908004 polymorphism was correlated with a decreased risk of OA, especially among females, smokers, non‐drinkers and individuals with age < 60 years or BMI ≥ 25. This SNP was also associated with Kellgren‐Lawrence grade and CRP. Similarly, LRP1 rs1799986 polymorphism decreased the risk of OA among males, smokers, drinkers and individuals with age < 60 years or BMI ≥ 25. TT genotype was more frequent in the group of VAS ≥ 6 versus VAS < 6. A low GRS was positively correlated with a decreased risk of OA. In addition, rs2908004 or rs1799986 polymorphism reduces the expression of WNT16 or LRP1. In conclusion, two SNPs (rs2908004 and rs1799986) are associated with the decreased risk of OA by regulating the Wnt pathway.

Effects of electromagnetic fields on osteoarthritis

Osteoarthritis (OA), characterized by joint malfunction and chronic disability, is the most common form of arthritis. The pathogenesis of OA is unclear, yet studies have shown that it is due to an imbalance between the synthesis and decomposition of chondrocytes, cell matrices and subchondral bone, which leads to the degeneration of articular cartilage. Currently, there are many therapies that can be used to treat OA, including the use of pulsed electromagnetic fields (PEMFs). PEMFs stimulate proliferation of chondrocytes and exert a protective effect on the catabolic environment. Furthermore, this technique is beneficial for subchondral trabecular bone microarchitecture and the prevention of subchondral bone loss, ultimately blocking the progression of OA. However, it is still unknown whether PEMFs could be used to treat OA in the clinic. Furthermore, the deeper signaling pathways underlying the mechanism by which PEMFs influence OA remain unclear.

Cartilage and Bone Destruction in Arthritis: Pathogenesis and Treatment Strategy: A Literature Review

Arthritis is inflammation of the joints accompanied by osteochondral destruction. It can take many forms, including osteoarthritis, rheumatoid arthritis, and psoriatic arthritis. These diseases share one commonality—osteochondral destruction based on inflammation. The background includes a close interaction between osseous tissues and immune cells through various inflammatory cytokines. However, the tissues and cytokines that play major roles are different in each disease, and as a result, the mechanism of osteochondral destruction also differs. In recent years, there have been many findings regarding not only extracellular signaling pathways but also intracellular signaling pathways. In particular, we anticipate that the intracellular signals of osteoclasts, which play a central role in bone destruction, will become novel therapeutic targets. In this review, we have summarized the pathology of arthritis and the latest findings on the mechanism of osteochondral destruction, as well as present and future therapeutic strategies for these targets.

Expression of Ihh signaling pathway in condylar cartilage after bite-raising in adult rats

Temporomandibular joint osteoarthritis (TMJOA) is a complex inflammatory condition with multiple factors and degenerative processes co-occurring. However, its pathogenesis remains uncertain. The purpose of the study was to observe the expression of Indian hedgehog (Ihh) signal related molecules in TMJOA induced by bite-raising and to study the effect and mechanism of Ihh signaling. Our research indicated that Ihh signaling pathway can be activated in condylar cartilage induced by bite-raising. The histological analysis showed TMJOA-like structural changes of condylar cartilage in experiment groups. Ihh, Smoothened (Smo), and Gli zinc finger transcription factors-1 (Gli-1) were activated in the experimental groups, and the expression levels increased significantly over time, whereas the sham control groups showed no fluctuation. Additionally, the expression levels of matrix metalloproteinase-13 (MMP-13) and cysteinyl aspartate specific proteinase-3 (Caspase-3) in the experiment groups increased in a time-dependent manner compared with the matched sham control groups. In conclusion, our results indicated that the Ihh signaling pathway may activate the occurrence of TMJOA by mediating the hypertrophy of chondrocytes, which may be an important regulatory mechanism and potential therapeutic target in the repair of condylar cartilage.

Effects of various dietary supplements on inflammatory processes in primary canine chondrocytes as a model of osteoarthritis

The use of dietary supplements as an alternative treatment for joint-related pathologies such as osteoarthritis (OA) is increasing. However, there is little scientific evidence to support the intended use. The aim of this study was to evaluate the anti-inflammatory effects of creatine- and amino acid-based supplements in primary cultured canine chondrocytes (CnCs) as an in-vitro model of OA and compare the effects to more commonly used agents, such as the non-steroidal anti-inflammatory drug (NSAID), carprofen, and the joint supplement, glucosamine (GS). CnCs were stimulated with interleukin-1β (IL-1β) and the subsequent release of prostaglandin E2 (PGE2) and tumor necrosis factor alpha (TNFα) was measured using an enzyme-linked immunosorbent assay (ELISA). Changes in oxylipins were also assessed using high-performance liquid chromatography/tandem mass spectrometry (HPLC/MS/MS). All compounds examined were able to significantly reduce the release of PGE2 and TNFα and were associated with reductions in cyclooxygenase-2 (COX-2) expression and nuclear factor-kappaB (NF-κB) phosphorylation. The creatine- and amino acids-based supplements also altered the profile of oxylipins produced. All compounds examined were less effective at reducing the release of PGE2 than carprofen. Carprofen significantly increased release of TNFα from CnCs, however, while the other agents reduced TNFα release. This study suggests that creatine- and amino acid-based supplements may have a beneficial role in preventing inflammation within the joint and that further studies are warranted.

Rice Porridge Containing Welsh Onion Root Water Extract Alleviates Osteoarthritis-Related Pain Behaviors, Glucose Levels, and Bone Metabolism in Osteoarthritis-Induced Ovariectomized Rats

Rice porridge containing Allium fistulosum (Welsh onion) root water extract (RAFR) has anti-inflammatory bioactive compounds. We examined whether the long-term administration of rice porridge with RAFR would prevent or delay the progression of osteoarthritis and menopausal symptoms in estrogen-deficient animals by ovariectomy. The rats consumed 40% fat energy diets containing 250 mg RAFR (rice: Allium fistulosum root = 13:1)/kg body weight (bw) (OVX-OA-RAFR-Low), 750 mg RAFR/kg bw (OVX-OA-RAFR-High) and 750 mg starch and protein/kg bw(OVX), respectively. After consuming the assigned diets for eight weeks, monoiodoacetate (OVX-OA) or saline (OVX) were injected into the knee joints of the rats for an additional three weeks. Sham rats were administered saline injections (normal-control). OVX-OA-RAFR improved oral glucose tolerance and also protected against decreases in bone mineral density and lean body mass in the legs and increases in fat mass in the abdomen, compared to the OVX and OVX-OA. OVX-OA-RAFR improved swelling and limping scores, normalized weight distribution between the osteoarthritic and normal limbs, and increased maximum running speeds compared to the OVX-OA. The OVX-OA deteriorated the articular cartilage by reducing the articular matrix and bone loss in the knee joint and it prevented knee joint deterioration when compared to the OVX. The improvement in osteoarthritis symptoms in OVX-OA-RAFR decreased the mRNA expression of matrix metallo-proteinase-1 and matrix metalloproteinase-13, tumor necrosis factor-α, and interleukin-1β and interleukin-6 in the articular cartilage compared to OVX-OA rats. In conclusions, RAFR is effective in treating osteoarthritis symptoms and it may be used for a therapeutic agent in osteoarthritis-induced menopausal women.

Anticatabolic Effects of Morin through the Counteraction of Interleukin-1β-Induced Inflammation in Rat Primary Chondrocytes

Morin, a flavonoid isolated from various medicinal herbal plants, has an anti-inflammatory effect. This study aimed to elucidate the anticatabolic effects and cellular mechanism of morin against interleukin-1β (IL-1β) in rat primary chondrocytes. Morin at 10-100 μM did not affect the viability of rat primary chondrocytes. Treatment with morin for 21 days ameliorated the IL-1β-induced decrease in extracellular matrix. Furthermore, treatment with morin attenuated IL-1β-induced proteoglycan loss in the articular cartilage through suppression of catabolic factors, such as matrix metalloproteinases, inflammatory mediators, and pro-inflammatory cytokines. These data indicated that morin exerted anticatabolic effects that can prevent and reduce progressive degeneration of the articular cartilage, and thus may be a potential candidate treatment for osteoarthritis.

The Association between Dietary Magnesium Intake and Magnetic Resonance Parameters for Knee Osteoarthritis

The aim of the study was to evaluate the relationship between dietary magnesium (Mg) intake and prevalence of knee osteoarthritis (OA), a topic poorly explored in the literature. Overall, 783 people participating in the Osteoarthritis Initiative (59.8% females; mean age: 62.3 years) and having an MRI assessment were enrolled in this cross-sectional study. Mg intake was measured with a semi-quantitative food frequency questionnaire, and its association with knee OA was evaluated for an increased intake of 100 mg/day. Using an adjusted linear regression analysis, a higher Mg intake (i.e., increase of 100 mg/day) corresponded to a significant increase in mean cartilage thickness, cartilage volume at medial tibia, cartilage volume and mean cartilage thickness at central medial femur, and cartilage volume and mean cartilage thickness in the central medial tibiofemoral compartment. In conclusion, an increased Mg dietary intake is associated with a better knee cartilage architecture, also when adjusting for potential confounders, suggesting a potential role of Mg in the prevention and treatment of knee OA.

[The effectiveness of complex therapy using the injectable form of chondroitin sulfate and sodium hyaluronate with osteoarthritis of the knee joint]

AIM

The study on the effectiveness of complex therapy for osteoarthritis (OA) of the knee joint was conducted in real clinical practice.

MATERIALS AND METHODS

The survey involved 125 patients aged fr om 50 to 70 years (25 men and 100 women) with a diagnosis of knee joint OA (the III roentgenologic Kellgren-Lawrence stage).The average age of the patients was 62±3.21, the average duration of the disease - 9.4±2.8 years. Patients were randomly assigned to three groups of 35 people, the control group had 20 patients. Group 1 patients received non - steroidal anti - inflammatory drugs (NSAIDs) + Injectran(Chondroitin sulfate) 200 mg intramuscularly (I.M.) every other day No. 25.In group 2, patients received NSAIDs + Fermatron 1% 2 ml with an interval of 7 days intra - articularly (I.A.) No. 3. In group 3 - NSAIDs + Injectran 200 mg (I.M.) every other day No. 25 + Fermatron 1% 2 ml with an interval of 7 days (I.A.) No. 3. In the control group (20 people), patients received only NSAIDs. Evaluation of the symptoms was carried out using the WOMAC index before the start of thetherapy, after 8 and 12 weeks of treatment. The intensity of pain while walking was estimated on a visual analogue scale.

RESULTS

In the groups that received Injectran (I; group 1) or Fermatron (F; group 2), the dynamics of pain while walking reduction was comparable and had slightly more than 30% in both groups, the figures are reliable in comparison withinitial data (p.

The Importance of the Knee Joint Meniscal Fibrocartilages as Stabilizing Weight Bearing Structures Providing Global Protection to Human Knee-Joint Tissues

The aim of this study was to review aspects of the pathobiology of the meniscus in health and disease and show how degeneration of the meniscus can contribute to deleterious changes in other knee joint components. The menisci, distinctive semilunar weight bearing fibrocartilages, provide knee joint stability, co-ordinating functional contributions from articular cartilage, ligaments/tendons, synovium, subchondral bone and infra-patellar fat pad during knee joint articulation. The meniscus contains metabolically active cell populations responsive to growth factors, chemokines and inflammatory cytokines such as interleukin-1 and tumour necrosis factor-alpha, resulting in the synthesis of matrix metalloproteases and A Disintegrin and Metalloprotease with ThromboSpondin type 1 repeats (ADAMTS)-4 and 5 which can degrade structural glycoproteins and proteoglycans leading to function-limiting changes in meniscal and other knee joint tissues. Such degradative changes are hall-marks of osteoarthritis (OA). No drugs are currently approved that change the natural course of OA and translate to long-term, clinically relevant benefits. For any pharmaceutical therapeutic intervention in OA to be effective, disease modifying drugs will have to be developed which actively modulate the many different cell types present in the knee to provide a global therapeutic. Many individual and combinatorial approaches are being developed to treat or replace degenerate menisci using 3D printing, bioscaffolds and hydrogel delivery systems for therapeutic drugs, growth factors and replacement progenitor cell populations recognising the central role the menisci play in knee joint health.

Negative effects of high mechanical tensile strain stimulation on chondrocyte injury in vitro

The mechanism underlying the development of osteoarthritis induced by high tensile strain is unclear. In this study, the effects of different degrees of mechanical tensile strain stimulation on Sprague-Dawley rat chondrocytes were explored. Rat chondrocytes were subjected to mechanical tensile strain at different intensities and frequencies (control group, low tensile strain group, intermediate tensile strain group, and high tensile strain group) using a self-made in vitro tensile strain device. After applying mechanical tensile strain, chondrocytes were collected to detect the expression of collagen II, Aggrecan, matrix metalloproteinase 13 (MMP13), ADAMTS5, and uncoupling protein 2 (UCP2) by real-time quantitative PCR and western blotting as well as reactive oxygen species (ROS) by fluorescence probes. Mechanical tensile strain at different frequencies and intensities had different effects on the biological functions of chondrocytes. Compared with the control group, the expression levels of Col II and Aggrecan in the low and intermediate tensile strain groups increased significantly, while the expression of MMP13 and ADAMTS5 decreased. There were no significant differences between the low and intermediate tensile strain groups. Col II and Aggrecan levels were significantly lower in the high tensile strain group than in the control group, while MMP13 and ADAMTS5 levels were higher. There were no significant differences in ROS production between the low and intermediate tensile strain groups and the control group, but the high tensile strain group exhibited significantly increased ROS production. The expression of UCP2 was significantly lower in the high tensile strain group than in all other groups. These results showed that stimulation with different levels of mechanical tensile strain has different effects on chondrocytes. Repeated high tensile strain promoted the anabolic function of chondrocytes, increased ROS production, and decreased UCP2. These results provide a potential mechanism by which osteoarthritis is induced by high mechanical tensile strain.

Knowledge of knee osteoarthritis among general population in Aseer region

Background

Osteoarthritis (OA) is the most common articular disease of the developed country and cause of chronic disability, and may cause joint failure. OA is one of the most prevalent situation that gives rise to disability, especially in elderly population.

Aim

To assess the knowledge of knee OA among general population in Aseer region.

Materials and Methods

A cross-sectional survey was conducted in Aseer region including 1052 participants. The participants were included by visiting the public areas in different cities in Aseer region where many people of different social and economic level were available, and because of the the nature of Saudi community regarding home-to-home interviews.

Results

The research included 1052 participants from different areas in Aseer region. The ages of participants ranged from 17 to 80 years old, with a mean age of 38 ± 12 years old. Approximately 89.0% of the sampled population had good awareness regarding preventive measures of knee OA. The second highest awareness level was recorded for relieving the measures of knee OA as 84.1% of the sampled population recorded good level of knowledge. In general, 82.6% of the population had good awareness level regarding OA in total.

Conclusions and Recommendations

The current research revealed that the awareness of the general population in Aseer region regarding knee OA was more than satisfactory, especially for preventive measures, relieving measures, and its risk factors.

Naproxen attenuates osteoarthritis progression through inhibiting the expression of prostaglandinl-endoperoxide synthase 1

OBJECTIVE

This study aims to test the effect of naproxen treatment and the biological target of naproxen for treating osteoarthritis (OA).

METHODS

Differentially expressed genes (DEGs) in OA synovial tissues and normal counterparts were analyzed by messenger RNA microarray analysis. R package (weighted gene coexpression network analysis) was used to divide DEGs into several modules and determine the hub genes in each module. The expression level of prostaglandin-endoperoxide synthase 1 ( PTGS1) in OA synovial cells and tissues was verified by a quantitative real-time polymerase chain reaction and western blot. Transwell assay evaluated the numbers of cell migration and invasion. Furthermore, Safranin O and fast green staining and hematoxylin and eosin staining were performed on joints from anterior cruciate ligament transection mice.

RESULTS

Microarray analysis determined PTGS1 was the hub gene in the black module, which was overexpressed in OA synovial cells and tissues compared with normal synovial cells. OA synovial cells transfected with sh-PTGS1 showed downregulation of PTGS1. After treatment with naproxen, the expression of PTGS1 sharply decreased in the OA group. The migration and invasion of OA synovial cells increased, whereas the cell apoptosis rate decreased when PTGS1 was overexpressed. However, the cell migration and invasion decreased, whereas cells apoptosis increased when it was treated with naproxen. Naproxen could also influence the expression level of six OA-related genes: LUBRICIN, matrix metalloproteinase 13 (MMP-13), cyclooxygenase-2 (COX-2), ACAN, COL2A1, and COL1A1.

CONCLUSION

We validated that naproxen could suppress the expression of PTGS1 in synovial cells. Moreover, naproxen could inhibit the migration/invasion ability of OA synoviocytes and promote the apoptosis rate OA synoviocytes.

The Role of Adenosine Receptor Activation in Attenuating Cartilaginous Inflammation

Adenosine receptor activation has been explored as a modulator of the inflammatory process that propagates osteoarthritis. It has been reported that cartilage has enhanced regenerative potential when influenced by adenosine receptor activation. As adenosine's role in maintaining chondrocyte homeostasis at the cellular and molecular levels is explored, successful in vivo applications of adenosine delivery for cartilage repair continue to be reported. This review summarizes the role adenosine receptor ligation plays in chondrocyte homeostasis and regeneration of articular cartilage damaged in osteoarthritis. It also reports on all the modalities reported for delivery of adenosine through in vivo applications.

Prophylactic and Therapeutic Use of Strontium Ranelate Reduces the Progression of Experimental Osteoarthritis

Introduction: Strontium ranelate (SrRan) has the potential to interfere in the progression of osteoarthritis (OA), multifactorial disease associated with mechanical problems and articular inflammatory changes. Objectives: This study aimed to test the effects of prophylactic and therapeutic use of SrRan on clinical parameters of pain, the inflammatory process, and degradation of the articular cartilage. Methods: This was an experimental study, using a model of knee OA induced by intra-articular injection of monoiodoacetate. Thirty Wistar rats were divided into five groups and treated as indicated: control, without intervention; prophylactic, received SrRan at a daily oral dose of 250 mg/kg for 28 days before OA induction; SrRan treatments, administered 250 or 500 mg/kg/day for 28 days after the induction; and model control, received saline solution after the induction. Behavioral tests (joint incapacity, mechanical hyperalgesia, tactile sensitivity, and forced ambulation), histological evaluation of articular cartilage, and determination of inflammatory cytokines in the synovial fluid (interleukin [IL]-6, IL-10, tumor necrosis factor [TNF]-α, and interferon [INF]-γ) were performed. Results: Both prophylactic and therapeutic treatments improved the articular discomfort. A prophylactic dose of 500 mg/kg/day also improved mechanical hyperalgesia and the same dose was beneficial on tactile sensitivity. SrRan did not improve ambulation. Levels of IL-6, IL-10, TNF-α, and IFN-γ in SrRan-treated groups with OA were not significantly different compared with those in the normal control animals. The histopathological evaluation showed less articular damage in the SrRan-treated and control groups compared to the saline-treated group. Conclusion: The prophylactic and therapeutic administration of SrRan was associated with improved behavioral patterns of pain, especially joint discomfort. SrRan administration mitigated histological changes in the articular cartilage and reduced the inflammatory process, which beneficially reduced the progression of OA in the experimental model studied.

Integration of Gene Expression Profile Data to Screen and Verify Hub Genes Involved in Osteoarthritis

Osteoarthritis (OA) is one of the most common diseases worldwide, but the pathogenic genes and pathways are largely unclear. The aim of this study was to screen and verify hub genes involved in OA and explore potential molecular mechanisms. The expression profiles of GSE12021 and GSE55235 were downloaded from the Gene Expression Omnibus (GEO) database, which contained 39 samples, including 20 osteoarthritis synovial membranes and 19 matched normal synovial membranes. The raw data were integrated to obtain differentially expressed genes (DEGs) and were deeply analyzed by bioinformatics methods. The Gene Ontology (GO) and pathway enrichment of DEGs were performed by DAVID and Kyoto Encyclopedia of Genes and Genomes (KEGG) online analyses, respectively. The protein-protein interaction (PPI) networks of the DEGs were constructed based on data from the STRING database. The top 10 hub genes VEGFA, IL6, JUN, IL1β, MYC, IL4, PTGS2, ATF3, EGR1, and DUSP1 were identified from the PPI network. Module analysis revealed that OA was associated with significant pathways including TNF signaling pathway, cytokine-cytokine receptor interaction, and osteoclast differentiation. The qRT-PCR result showed that the expression level of IL6, VEGFA, JUN, IL-1β, and ATF3 was significantly increased in OA samples (p < 0.05), and these candidate genes could be used as potential diagnostic biomarkers and therapeutic targets of OA.

Daily oral supplementation with collagen peptides combined with vitamins and other bioactive compounds improves skin elasticity and has a beneficial effect on joint and general wellbeing

Aging is a multifactorial and natural process that causes physiological changes in organs, tissues and cells over time. In the skin and cartilage, aging leads to a decrease in the synthesis and changes in the arrangement of proteoglycans and collagen, in addition to the loss of glycosaminoglycans, which are responsible for the integrity and health of these tissues. We hypothesized that daily oral supplementation with a liquid nutraceutical containing hydrolyzed fish collagen, vitamins, antioxidants and other active ingredients could improve skin texture and elasticity, and in addition have a protective effect on joint health. A double-blind, randomized, placebo-controlled clinical trial was conducted on 120 subjects who consumed either the test product or placebo on a daily basis for 90 days. Subjects consuming the test product had an overall significant increase in skin elasticity (+40%; P < .0001) when compared to placebo. Histological analysis of skin biopsies revealed positive changes in the skin architecture, with a reduction in solar elastosis and improvement in collagen fiber organization in the test product group. As reported in the self-perception questionnaires, these results were confirmed by the subjects' own perceptions in that participants agreed their skin was more hydrated and more elastic. In addition, the consumption of the test product reduced joint pain by -43% and improved joint mobility by +39%. Oral supplementation with collagen bioactive peptides combined with chondroitin sulphate, glucosamine, L-carnitine, vitamins, and minerals significantly improved the clinical parameters related to skin aging and joint health, and therefore, might be an effective solution to slow down the hallmarks of aging.

Phospholipid-Coated Mesoporous Silica Nanoparticles Acting as Lubricating Drug Nanocarriers

Osteoarthritis (OA) is a severe disease caused by wear and inflammation of joints. In this study, phospholipid-coated mesoporous silica nanoparticles (MSNs@lip) were prepared in order to treat OA at an early stage. The phospholipid layer has excellent lubrication capability in aqueous media due to the hydration lubrication mechanism, while mesoporous silica nanoparticles (MSNs) act as effective drug nanocarriers. The MSNs@lip were characterized by scanning electron microscope, transmission electron microscope, Fourier transform infrared spectrum, X-ray photoelectron spectrum, thermogravimetric analysis and dynamic light scattering techniques to confirm that the phospholipid layer was coated onto the surface of MSNs successfully. A series of tribological tests were performed under different experimental conditions, and the results showed that MSNs@lip with multi-layers of phospholipids greatly reduced the friction coefficient in comparison with MSNs. Additionally, MSNs@lip demonstrated sustained drug release behavior and were biocompatible based on CCK-8 assay using MC3T3-E1 cells. The MSNs@lip developed in the present study, acting as effective lubricating drug nanocarriers, may represent a promising strategy to treat early stage OA by lubrication enhancement and drug delivery therapy.

Intraperitoneal injection of thalidomide alleviates early osteoarthritis development by suppressing vascular endothelial growth factor expression in mice

Vascular endothelial growth factor (VEGF) is expressed in articular cartilage and increases in expression levels have been associated with the progression of osteoarthritis (OA). Thalidomide is a drug that has been reported to inhibit angiogenesis and reduce VEGF production by downregulating VEGF expression. The objective of the present study was to determine whether intraperitoneal administration of thalidomide may attenuate early OA development in mice. Male C57BL/6 mice (10‑weeks‑old) were randomly assigned into the destabilization of the medial meniscus (Dmm) with thalidomide treatment (Dmm+Th), Dmm and Sham groups equally. An OA model was induced surgically in Dmm+Th and Dmm groups, and mice of the Dmm+Th group were subsequently treated with an intraperitoneal injection of thalidomide (200 mg/kg/day). At 2 and 4 weeks following surgery, the pathological alterations in cartilage samples were assessed qualitatively by hematoxylin and eosin staining and Safranin O/Fast green staining, and quantitatively by the Osteoarthritis Research Society International scoring system. The mRNA expression levels of matrix metalloproteinase‑13 (MMP‑13) and VEGF were measured by reverse transcription‑quantitative polymerase chain reaction. The protein expression levels of MMP‑13 and VEGF were detected by immunofluorescence and immunohistochemistry, respectively. The production of VEGF in serum was evaluated via an ELISA assay. Pathological scores were significantly higher in the Dmm and the Dmm+Th groups than those in the Sham group; however, the Dmm+Th group exhibited markedly less severe pathological changes compared with the Dmm group. Compared with the Sham group, the mRNA and protein expression levels of VEGF and MMP‑13 in the Dmm and the Dmm+Th groups were significantly increased. The Dmm+Th group exhibited significantly decreased expression levels of VEGF and MMP‑13, as well as significantly decreased serum VEGF concentration compared with the Dmm group. Thus, the results of the present study demonstrated that intraperitoneal administration of thalidomide may alleviate the development of early OA by suppressing VEGF expression in mice and may have potential as a novel therapy for the treatment of OA.

Inducible nitric oxide synthase as a target for osteoarthritis treatment

INTRODUCTION

Inducible nitric oxide synthase (iNOS) is the enzyme responsible for the production of nitric oxide (NO), a major proinflammatory and destructive mediator in osteoarthritis (OA). Areas covered: This is a comprehensive review of the recent literature on the involvement of iNOS in osteoarthritis and its potential to be used as a target for OA treatment. Evidence from in vitro, in vivo and human studies was systematically collected using medical search engines. Preclinical studies have focused on the effect of direct and indirect iNOS inhibitors in both animal and human tissues. Apart from direct inhibitors, common pharmacological agents, herbal and dietary medicines as well as hyperbaric oxygen, low level laser and low intensity pulsed ultrasound have been shown to exhibit a chondroprotective effect by inhibiting the expression of iNOS. Expert opinion: Data support the further investigation of iNOS inhibitors for the treatment of OA in human studies and clinical trials. Indirect iNOS inhibitors such as interleukin 1 inhibitors also need to be studied in greater detail. Finally, human studies need to be conducted on the herbal and dietary medicines and on the non-invasive, non-pharmacological treatments.

Osteoarthritis: Trauma vs Disease

Osteoarthritis (OA) is the most prevalent joint disease characterized by pain and degenerative lesions of the cartilage, subchondral bone, and other joint tissues. The causes of OA remain incompletely understood. Over the years, it has become recognized that OA is a multifactorial disease. In particular, aging and trauma are the main risk factors identified for the development of OA; however, other factors such as genetic predisposition, obesity, inflammation, gender and hormones, or metabolic syndrome contribute to OA development and lead to a more severe outcome. While this disease mainly affects people older than 60 years, OA developed after joint trauma affects all range ages and has a particular impact on young individuals and people who have highest levels of physical activity such as athletes. Traumatic injury to the joint often results in joint instability or intra-articular fractures which lead to posttraumatic osteoarthritis (PTOA). In response to injury, several molecular mechanisms are activated, increasing the production and activation of different factors that contribute to the progression of OA.In this chapter, we have focused on the interactions and contribution of the multiple factors involved in joint destruction and progression of OA. In addition, we overview the main changes and molecular mechanisms related to OA pathogenesis.

Lowering side effects of NSAID usage in osteoarthritis: recent attempts at minimizing dosage

INTRODUCTION

Osteoarthritis is a burdensome disease that causes progressive damage to articular cartilage. Non-steroidal anti-inflammatory drugs (NSAIDs) are one of the preferred treatments for symptomatic relief. However, NSAIDs can cause serious dose-dependent side effects, which has prompted experts to recommend the minimization of NSAID dosage.

AREAS COVERED

This review focuses on three broad strategies that are currently being investigated or implemented to minimize NSAID dosage: nano-formulation, encapsulation, and topical delivery. The benefits, challenges and current status of these methods are discussed.

EXPERT OPINION

Multiple strategies are under investigation to lower NSAID dosage. There is great potential in developing formulations that utilize more than one of these strategies together. However, there are challenges to developing these lower dose preparations. In order to maximize the clinical potential of the abundance of NSAIDs that are both available and being developed, there is a major need for additional clinical studies directly comparing safety and efficacy of different preparations.

Increased 15-lipoxygenase-1 expression in chondrocytes contributes to the pathogenesis of osteoarthritis

15-Lipoxygenase-1 (15-LO-1) is involved in many pathological processes. The purpose of this study was to determine the potential role of 15-LO-1 in osteoarthritis (OA). The levels of 15-LO-1 expression were measured by western blotting and quantitative real-time PCR in articular cartilage from the OA rat models and OA patients. To further investigate the effects of 15-LO-1 on chondrocyte functions, such as extracellular matrix (ECM) secretion, the release of matrix-degrading enzymes, the production of reactive oxygen species (ROS), cell proliferation and apoptosis, we decreased or increased 15-LO-1 expression in chondrocytes by means of transfecting with siRNA targeting 15-LO-1 and plasmid encoding 15-LO-1, respectively. The results showed that 15-LO-1 expression was obviously increased in articular cartilage from OA rats and OA patients. It was also found that many factor-related OA, such as mechanical loading, ROS, SNP and inflammatory factor, significantly promoted 15-LO-1 expression and activity in chondrocytes. Silencing 15-LO-1 was able to markedly alleviate mechanical loading-induced cartilage ECM secretion, cartilage-degrading enzyme secretion and ROS production. Overexpression of 15-LO-1 could inhibit chondrocyte proliferation and induce chondrocyte apoptosis. In addition, reduction of 15-LO-1 in vivo significantly alleviated OA. Taken together, these results indicate that 15-LO-1 has an important role in the disease progression of OA. Thus 15-LO-1 may be a good target for developing drugs in the treatment of OA.

Intra-articular injection of microRNA-140 (miRNA-140) alleviates osteoarthritis (OA) progression by modulating extracellular matrix (ECM) homeostasis in rats

OBJECTIVE

Disruptions of extracellular matrix (ECM) homeostasis are key events in the pathogenesis of osteoarthritis (OA). MicroRNA-140 (miRNA-140) is expressed specifically in cartilage and regulates ECM-degrading enzymes. Our objective in this study was to determine if intra-articular injection of miRNA-140 can attenuate OA progression in rats.

DESIGN

miRNA-140 levels in human normal and OA cartilage derived chondrocytes and synovial fluid were assessed by polymerase chain reaction (PCR). After primary human chondrocytes were transfected with miRNA-140 mimic or inhibitor, PCR and western blotting were performed to quantify Collagen II, MMP-13, and ADAMTS-5 expression. An OA model was induced surgically in rats, and subsequently treated with one single intra-articular injection of miRNA-140 agomir. At 4, 8, and 12 weeks after surgery, OA progression were evaluated macroscopically, histologically, and immunohistochemically in these rats.

RESULTS

miRNA-140 levels were significantly reduced in human OA cartilage derived chondrocytes and synovial fluid compared with normal chondrocytes and synovial fluid. Overexpressing miRNA-140 in primary human chondrocytes promoted Collagen II expression and inhibited MMP-13 and ADAMTS-5 expression. miRNA-140 levels in rat cartilage were significantly higher in the miRNA-140 agomir group than in the control group. Moreover, behavioural scores, chondrocyte numbers, cartilage thickness and Collagen II expression levels in cartilage were significantly higher, while pathological scores and MMP-13 and ADAMTS-5 expression levels were significantly lower in the miRNA-140 agomir group than in the control group.

CONCLUSION

Intra-articular injection of miRNA-140 can alleviate OA progression by modulating ECM homeostasis in rats, and may have potential as a new therapy for OA.

Inhibition of the TGF-β1/Smad signaling pathway protects against cartilage injury and osteoarthritis in a rat model

Transforming growth factor-β1 (TGF-β1) in osteoblastic cells triggers pathological changes observed in osteoarthritis (OA). Thus, we hypothesized that the inhibition of the TGF-β1/Smad signaling pathway could act to protect against cartilage injury in rats with OA. After establishment of rat models induced by papain and L-cysteine, rats were subsequently assigned into the TβRI inhibitors, normal control (NC) and OA model groups. RT-qPCR and western blotting were performed to determine mRNA and protein expressions of TGFβ1, Smad2, Smad3 and Activin receptor-like kinase 5 (ALK5), respectively. Immunofluorescence staining was used to detect the expression of collagen X (COLX). Immunohistochemical staining was used to determine the expression of the specific transcription factor Osterix as well as TGF-β1 related factors. Increased expression levels of TGFβ1, Smad2, Smad3 and ALK5in the OA model group were higher than those in the TβRI inhibitors group. Compared with the NC group, the OA model groups exhibited elevated expressions of TGF-β1, p-Smad2/3 and ALK5 in the TGF-β1 signaling pathway, and elevated numbers of COLX and Osterix positive cells. The rats in the TβRI inhibitors group had decreased expressions of p-Smad2/3 and ALK5, as well as decreased COLX and Osterix positive cells when compared with OA model group. However, these levels were still higher than that of the NC group. Our findings suggested that up-regulation of TGF-β1 inhibited the TGF-β1/Smad signaling pathway acting to alleviate OA, thus highlighting the potential of the TGF-β1/Smad signaling pathway as a therapeutic target for treatment of OA.

Integrative epigenomics, transcriptomics and proteomics of patient chondrocytes reveal genes and pathways involved in osteoarthritis

Osteoarthritis (OA) is a common disease characterized by cartilage degeneration and joint remodeling. The underlying molecular changes underpinning disease progression are incompletely understood. We investigated genes and pathways that mark OA progression in isolated primary chondrocytes taken from paired intact versus degraded articular cartilage samples across 38 patients undergoing joint replacement surgery (discovery cohort: 12 knee OA, replication cohorts: 17 knee OA, 9 hip OA patients). We combined genome-wide DNA methylation, RNA sequencing, and quantitative proteomics data. We identified 49 genes differentially regulated between intact and degraded cartilage in at least two -omics levels, 16 of which have not previously been implicated in OA progression. Integrated pathway analysis implicated the involvement of extracellular matrix degradation, collagen catabolism and angiogenesis in disease progression. Using independent replication datasets, we showed that the direction of change is consistent for over 90% of differentially expressed genes and differentially methylated CpG probes. AQP1, COL1A1 and CLEC3B were significantly differentially regulated across all three -omics levels, confirming their differential expression in human disease. Through integration of genome-wide methylation, gene and protein expression data in human primary chondrocytes, we identified consistent molecular players in OA progression that replicated across independent datasets and that have translational potential.

Identification of potential target genes associated with the pathogenesis of osteoarthritis using microarray based analysis

The aim of the present study was to investigate the molecular circuitry of osteoarthritis (OA) and identify more potential target genes for OA treatment. Microarray data of GSE32317 was downloaded from the National Center for Biotechnology Information Gene Expression Omnibus database. Differentially expressed genes (DEGs) were identified in samples of synovial membrane from patients with early stage of knee OA (OA_Early) and late stage of knee OA (OA_End) that were compared with healthy specimens. Bioinformatics analysis was applied to analyze the significant functions and pathways that were enriched by the common DEGs identified in OA_Early and OA_End samples. Furthermore, a protein‑protein interaction (PPI) network was constructed and significant modules were extracted. Transcription factors (TFs) that could regulate genes in the significant modules were identified. A total of 1,207 and 1,575 DEGs were identified in OA_Early and OA_End samples compared with healthy samples, respectively. A total of 740 genes were upregulated and 308 genes were downregulated across the OA_Early and OA_End samples. These common DEGs were enriched in different gene ontology terms and pathways, such as immune response. Angiotensinogen (AGT) and C‑X‑C motif chemokine ligand 12 (CXCL12) were identified to be hub proteins in the PPI network or in the selected module 1. In addition, the DEG lysine demethylase 2B (KDM2B) was identified as a TF that can regulate genes in the significant modules 2 and 3. In conclusion, the present study has identified AGT, CXCL12 and KDM2B as potentially essential genes associated with the pathogenesis of knee OA.

Vitamin D and Its Effects on Articular Cartilage and Osteoarthritis

Background:

Osteoarthritis (OA) currently affects 10% of the American population. There has been a recent push to determine exactly what causes OA and how it can be treated most effectively. Serum vitamin D levels have been associated with OA and may have an effect on articular cartilage remodeling.

Purpose:

To critically review the published research on the effect of vitamin D on articular cartilage and the development of OA as well as on the mechanism behind cartilage regeneration and degeneration.

Study Design:

Review.

Methods:

A systematic search of PubMed and the Web of Science was performed for relevant studies published in the English language through April 30, 2016, using the terms vitamin D, articular cartilage, and osteoarthritis.

Results:

On a molecular level, 1α,25(OH)₂D₃, the activated form of vitamin D, plays a role in articular cartilage degeneration. Vitamin D binds to vitamin D receptors, triggering a signaling cascade that leads to chondrocyte hypertrophy. In clinical trials, vitamin D deficiency poses a risk factor for OA, and those with decreased cartilage thickness are more likely to be vitamin D–insufficient.

Conclusion:

The role of vitamin D supplementation in the treatment or prevention of OA remains uncertain. More research is needed to reconcile these conflicting findings.

The potential of induced pluripotent stem cells as a tool to study skeletal dysplasias and cartilage-related pathologic conditions

The development of induced pluripotent stem cells (iPSCs) technology has opened up new horizons for development of new research tools especially for skeletal dysplasias, which often lack human disease models. Regenerative medicine and tissue engineering could be the next areas to benefit from refinement of iPSC methods to repair focal cartilage defects, while applications for osteoarthritis (OA) and drug screening have evolved rather slowly. Although the advances in iPSC research of skeletal dysplasias and repair of focal cartilage lesions are not directly relevant to OA, they can be considered to pave the way to future prospects and solutions to OA research, too. The same problems which face the present cell-based treatments of cartilage injuries concern also the iPSC-based ones. However, established iPSC lines, which have no genomic aberrations and which efficiently differentiate into extracellular matrix secreting chondrocytes, could be an invaluable cell source for cell transplantations in the future. The safety issues concerning the recipient risks of teratoma formation and immune response still have to be solved before the potential use of iPSCs in cartilage repair of focal cartilage defects and OA.

Conditional Deletion of the Phd2 Gene in Articular Chondrocytes Accelerates Differentiation and Reduces Articular Cartilage Thickness

Based on our findings that PHD2 is a negative regulator of chondrocyte differentiation and that hypoxia signaling is implicated in the pathogenesis of osteoarthritis, we investigated the consequence of disruption of the Phd2 gene in chondrocytes on the articular cartilage phenotype in mice. Immunohistochemistry detected high expression of PHD2 in the superficial zone (SZ), while PHD3 and HIF-1α (target of PHD2) are mainly expressed in the middle-deep zone (MDZ). Conditional deletion of the Phd2 gene (cKO) in chondrocytes accelerated the transition of progenitors to hypertrophic (differentiating) chondrocytes as revealed by reduced SZ thickness, and increased MDZ thickness, as well as increased chondrocyte hypertrophy. Immunohistochemistry further revealed decreased levels of progenitor markers but increased levels of hypertrophy markers in the articular cartilage of the cKO mice. Treatment of primary articular chondrocytes, in vitro, with IOX2, a specific inhibitor of PHD2, promoted articular chondrocyte differentiation. Knockdown of Hif-1α expression in primary articular chondrocytes using lentiviral vectors containing Hif-1α shRNA resulted in reduced expression levels of Vegf, Glut1, Pgk1, and Col10 compared to control shRNA. We conclude that Phd2 is a key regulator of articular cartilage development that acts by inhibiting the differentiation of articular cartilage progenitors via modulating HIF-1α signaling.

Altered joint tribology in osteoarthritis: Reduced lubricin synthesis due to the inflammatory process. New horizons for therapeutic approaches

Osteoarthritis (OA) is the most common form of joint disease. This review aimed to consolidate the current evidence that implicates the inflammatory process in the attenuation of synovial lubrication and joint tissue homeostasis in OA. Moreover, with these findings, we propose some evidence for novel therapeutic strategies for preventing and/or treating this complex disorder. The studies reviewed support that inflammatory mediators participate in the onset and progression of OA after joint injury. The flow of pro-inflammatory cytokines following an acute injury seems to be directly associated with altered lubricating ability in the joint tissue. The latter is associated with reduced level of lubricin, one of the major joint lubricants. Future research should focus on the development of new therapies that attenuate the inflammatory process and restore lubricin synthesis and function. This approach could support joint tribology and synovial lubrication leading to improved joint function and pain relief.

Mimicked cartilage scaffolds of silk fibroin/hyaluronic acid with stem cells for osteoarthritis surgery: Morphological, mechanical, and physical clues

Osteoarthritis is a critical disease that comes from degeneration of cartilage tissue. In severe cases surgery is generally required. Tissue engineering using scaffolds with stem cell transplantation is an attractive approach and a challenge for orthopedic surgery. For sample preparation, silk fibroin (SF)/hyaluronic acid (HA) scaffolds in different ratios of SF/HA (w/w) (i.e., 100:0, 90:10, 80:20, and 70:30) were formed by freeze-drying. The morphological, mechanical, and physical clues were considered in this research. The morphological structure of the scaffolds was observed by scanning electron microscope. The mechanical and physical properties of the scaffolds were analyzed by compressive and swelling ratio testing, respectively. For the cell experiments, scaffolds were seeded and cultured with human umbilical cord-derived mesenchymal stem cells (HUMSCs). The cultured scaffolds were tested for cell viability, histochemistry, immunohistochemistry, and gene expression. The SF with HA scaffolds showed regular porous structures. Those scaffolds had a soft and elastic characteristic with a high swelling ratio and water uptake. The SF/HA scaffolds showed a spheroid structure of the cells in the porous structure particularly in the SF80 and SF70 scaffolds. Cells could express Col2a, Agg, and Sox9 which are markers for chondrogenesis. It could be deduced that SF/HA scaffolds showed significant clues for suitability in cartilage tissue engineering and in surgery for osteoarthritis.

Animal models of osteoarthritis: classification, update, and measurement of outcomes

Osteoarthritis (OA) is one of the most commonly occurring forms of arthritis in the world today. It is a debilitating chronic illness causing pain and immense discomfort to the affected individual. Significant research is currently ongoing to understand its pathophysiology and develop successful treatment regimens based on this knowledge. Animal models have played a key role in achieving this goal. Animal models currently used to study osteoarthritis can be classified based on the etiology under investigation, primary osteoarthritis, and post-traumatic osteoarthritis, to better clarify the relationship between these models and the pathogenesis of the disease. Non-invasive animal models have shown significant promise in understanding early osteoarthritic changes. Imaging modalities play a pivotal role in understanding the pathogenesis of OA and the correlation with pain. These imaging studies would also allow in vivo surveillance of the disease as a function of time in the animal model. This review summarizes the current understanding of the disease pathogenesis, invasive and non-invasive animal models, imaging modalities, and pain assessment techniques in the animals.

ROS/oxidative stress signaling in osteoarthritis

Osteoarthritis is the most common joint disorder with increasing prevalence due to aging of the population. Its multi-factorial etiology includes oxidative stress and the overproduction of reactive oxygen species, which regulate intracellular signaling processes, chondrocyte senescence and apoptosis, extracellular matrix synthesis and degradation along with synovial inflammation and dysfunction of the subchondral bone. As disease-modifying drugs for osteoarthritis are rare, targeting the complex oxidative stress signaling pathways would offer a valuable perspective for exploration of potential therapeutic strategies in the treatment of this devastating disease.

Comparative Pathology of Aging Great Apes: Bonobos, Chimpanzees, Gorillas, and Orangutans

The great apes (chimpanzees, bonobos, gorillas, and orangutans) are our closest relatives. Despite the many similarities, there are significant differences in aging among apes, including the human ape. Common to all are dental attrition, periodontitis, tooth loss, osteopenia, and arthritis, although gout is uniquely human and spondyloarthropathy is more prevalent in apes than humans. Humans are more prone to frailty, sarcopenia, osteoporosis, longevity past reproductive senescence, loss of brain volume, and Alzheimer dementia. Cerebral vascular disease occurs in both humans and apes. Cardiovascular disease mortality increases in aging humans and apes, but coronary atherosclerosis is the most significant type in humans. In captive apes, idiopathic myocardial fibrosis and cardiomyopathy predominate, with arteriosclerosis of intramural coronary arteries. Similar cardiac lesions are occasionally seen in wild apes. Vascular changes in heart and kidneys and aortic dissections in gorillas and bonobos suggest that hypertension may be involved in pathogenesis. Chronic kidney disease is common in elderly humans and some aging apes and is linked with cardiovascular disease in orangutans. Neoplasms common to aging humans and apes include uterine leiomyomas in chimpanzees, but other tumors of elderly humans, such as breast, prostate, lung, and colorectal cancers, are uncommon in apes. Among the apes, chimpanzees have been best studied in laboratory settings, and more comparative research is needed into the pathology of geriatric zoo-housed and wild apes. Increasing longevity of humans and apes makes understanding aging processes and diseases imperative for optimizing quality of life in all the ape species.