Regulation of chondrocytic gene expression by biomechanical signals

Urolithin B reduces cartilage degeneration and alleviates osteoarthritis by inhibiting inflammation

Osteoarthritis is the most prevalent degenerative joint disease reported worldwide. Conventional treatment strategies mainly focus on medication and involve surgical joint replacement. The use of these therapies is limited by gastrointestinal complications and the lifespan of joint prostheses. Hence, safe and efficacious drugs are urgently needed to impede the osteoarthritis progression. Urolithin B, a metabolite of ellagic acid in the gut, exhibits anti-inflammatory and antioxidant properties; however, its role in osteoarthritis remains unclear. In this study, we demonstrated that urolithin B efficiently inhibits the inflammatory factor-induced production of matrix metalloproteinases (MMP3 and MMP13) in vitro and upregulates the expression of type II collagen and aggrecan. Urolithin B alleviates cartilage erosion and osteophyte formation induced by anterior cruciate ligament transections. Moreover, urolithin B inhibits the activation of the NF-κB pathway by reducing the phosphorylation of Iκb-α and the nuclear translocation of P65. In summary, urolithin B significantly inhibits inflammation and alleviates osteoarthritis. Hence, urolithin B can be considered a potential agent suitable for the effective treatment of osteoarthritis in the future.

Mechanical loading rescues mechanoresponsiveness in a human osteoarthritis explant model despite Wnt activation

OBJECTIVES

Optimizing rehabilitation strategies for osteoarthritis necessitates a comprehensive understanding of chondrocytes' mechanoresponse in both health and disease, especially in the context of the interplay between loading and key pathways involved in osteoarthritis (OA) development, like canonical Wnt signaling. This study aims to elucidate the role of Wnt signaling in the mechanoresponsiveness of healthy and osteoarthritic human cartilage.

METHODS

We used an ex-vivo model involving short-term physiological mechanical loading of human cartilage explants. First, the loading protocol for subsequent experiments was determined. Next, loading was applied to non-OA-explants with or without Wnt activation with CHIR99021. Molecular read-outs of anabolic, pericellular matrix and matrix remodeling markers were used to assess the effect of Wnt on cartilage mechanoresponse. Finally, the same set-up was used to study the effect of loading in cartilage from patients with established OA.

RESULTS

Our results confirm that physiological loading maintains expression of anabolic genes in non-OA cartilage, and indicate a deleterious effect of Wnt activation in the chondrocyte mechanoresponsiveness. This suggests that loading-induced regulation of chondrocyte markers occurs downstream of canonical Wnt signaling. Interestingly, our study highlighted contrasting mechanoresponsiveness in the model of Wnt activation and the established OA samples, with established OA cartilage maintaining its mechanoresponsiveness, and mechanical loading rescuing the chondrogenic phenotype.

CONCLUSION

This study provides insights into the mechanoresponsiveness of human cartilage in both non-OA and OA conditions. These findings hold the potential to contribute to the development of strategies that optimize the effect of dynamic compression by correcting OA pathological cell signaling.

The role of apoptosis in the pathogenesis of osteoarthritis

PURPOSE

Apoptosis is an important physiological process, making a great difference to development and tissue homeostasis. Osteoarthritis (OA) is a chronic joint disease characterized by degeneration and destruction of articular cartilage and bone hyperplasia. This purpose of this study is to provide an updated review of the role of apoptosis in the pathogenesis of osteoarthritis.

METHODS

A comprehensive review of the literature on osteoarthritis and apoptosis was performed, which mainly focused on the regulatory factors and signaling pathways associated with chondrocyte apoptosis in osteoarthritis and other pathogenic mechanisms involved in chondrocyte apoptosis.

RESULTS

Inflammatory mediators such as reactive oxygen species (ROS), nitric oxide (NO), IL-1β, tumor necrosis factor-α (TNF-α), and Fas are closely related to chondrocyte apoptosis. NF-κB signaling pathway, Wnt signaling pathway, and Notch signaling pathway activate proteins and gene targets that promote or inhibit the progression of osteoarthritis disease, including chondrocyte apoptosis and ECM degradation. Long non-coding RNAs (LncRNAs) and microRNAs (microRNAs) have gradually replaced single and localized research methods and become the main research approaches. In addition, the relationship between cellular senescence, autophagy, and apoptosis was also briefly explained.

CONCLUSION

This review offers a better molecular delineation of apoptotic processes that may help in designing new therapeutic options for OA treatment.

Ceria Nanoparticles Alleviated Osteoarthritis through Attenuating Senescence and Senescence-Associated Secretory Phenotype in Synoviocytes

Accumulation of senescent cells is the prominent risk factor for osteoarthritis (OA), accelerating the progression of OA through a senescence-associated secretory phenotype (SASP). Recent studies emphasized the existence of senescent synoviocytes in OA and the therapeutic effect of removing senescent synoviocytes. Ceria nanoparticles (CeNP) have exhibited therapeutic effects in multiple age-related diseases due to their unique capability of ROS scavenging. However, the role of CeNP in OA remains unknown. Our results revealed that CeNP could inhibit the expression of senescence and SASP biomarkers in multiple passaged and hydrogen-peroxide-treated synoviocytes by removing ROS. In vivo, the concentration of ROS in the synovial tissue was remarkably suppressed after the intra-articular injection of CeNP. Likewise, CeNP reduced the expression of senescence and SASP biomarkers as determined by immunohistochemistry analysis. The mechanistic study showed that CeNP inactivated the NFκB pathway in senescent synoviocytes. Finally, safranin O-fast green staining showed milder destruction of articular cartilage in the CeNP-treated group compared with the OA group. Overall, our study suggested that CeNP attenuated senescence and protected cartilage from degeneration via scavenging ROS and inactivating the NFκB signaling pathway. This study has potentially significant implications in the field of OA as it provides a novel strategy for OA treatment.

Intervertebral disc degeneration and osteoarthritis: a common molecular disease spectrum

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

NFκB inhibition to lift the mechano-competence of mesenchymal stromal cell-derived neocartilage toward articular chondrocyte levels

Background

Fully functional regeneration of skeletal defects by multipotent progenitor cells requires that differentiating cells gain the specific mechano-competence needed in the target tissue. Using cartilage neogenesis as an example, we asked whether proper phenotypic differentiation of mesenchymal stromal cells (MSC) into chondrocytes in vitro will install the adequate biological mechano-competence of native articular chondrocytes (AC).

Methods

The mechano-competence of human MSC- and AC-derived neocartilage was compared during differentiation for up to 35 days. The neocartilage layer was subjected to physiologic dynamic loading in a custom-designed bioreactor and assayed for mechano-sensitive gene and pathway activation, extracellular matrix (ECM) synthesis by radiolabel incorporation, nitric oxide (NO) and prostaglandin E₂ (PGE₂) production. Input from different pathways was tested by application of agonists or antagonists.

Results

MSC and AC formed neocartilage of similar proteoglycan content with a hardness close to native tissue. Mechano-stimulation on day 21 and 35 induced a similar upregulation of mechano-response genes, ERK phosphorylation, NO production and PGE₂ release in both groups, indicating an overall similar transduction of external mechanical signals. However, while AC maintained or enhanced proteoglycan synthesis after loading dependent on tissue maturity, ECM synthesis was always significantly disturbed by loading in MSC-derived neocartilage. This was accompanied by significantly higher COX2 and BMP2 background expression, > 100-fold higher PGE₂ production and a weaker SOX9 stimulation in response to loading in MSC-derived neocartilage. Anabolic BMP-pathway activity was not rate limiting for ECM synthesis after loading in both groups. However, NFκB activation mimicked the negative loading effects and enhanced PGE₂ production while inhibition of catabolic NFκB signaling rescued the load-induced negative effects on ECM synthesis in MSC-derived neocartilage.

Conclusions

MSC-derived chondrocytes showed a higher vulnerability to be disturbed by loading despite proper differentiation and did not acquire an AC-like mechano-competence to cope with the mechanical stress of a physiologic loading protocol. Managing catabolic NFκB influences was one important adaptation to install a mechano-resistance closer to AC-derived neocartilage. This new knowledge asks for a more functional adaptation of MSC chondrogenesis, novel pharmacologic co-treatment strategies for MSC-based clinical cartilage repair strategies and may aid a more rational design of physical rehabilitation therapy after AC- versus MSC-based surgical cartilage intervention.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-02843-x.

Cartilage Tissue Engineering Approaches Need to Assess Fibrocartilage When Hydrogel Constructs Are Mechanically Loaded

Chondrocytes that are impregnated within hydrogel constructs sense applied mechanical force and can respond by expressing collagens, which are deposited into the extracellular matrix (ECM). The intention of most cartilage tissue engineering is to form hyaline cartilage, but if mechanical stimulation pushes the ratio of collagen type I (Col1) to collagen type II (Col2) in the ECM too high, then fibrocartilage can form instead. With a focus on Col1 and Col2 expression, the first part of this article reviews the latest studies on hyaline cartilage regeneration within hydrogel constructs that are subjected to compression forces (one of the major types of the forces within joints) in vitro. Since the mechanical loading conditions involving compression and other forces in joints are difficult to reproduce in vitro, implantation of hydrogel constructs in vivo is also reviewed, again with a focus on Col1 and Col2 production within the newly formed cartilage. Furthermore, mechanotransduction pathways that may be related to the expression of Col1 and Col2 within chondrocytes are reviewed and examined. Also, two recently-emerged, novel approaches of load-shielding and synchrotron radiation (SR)–based imaging techniques are discussed and highlighted for future applications to the regeneration of hyaline cartilage. Going forward, all cartilage tissue engineering experiments should assess thoroughly whether fibrocartilage or hyaline cartilage is formed.

Biotribology of Synovial Cartilage: A New Method for Visualization of Lubricating Film and Simultaneous Measurement of the Friction Coefficient

A healthy natural synovial joint is very important for painless active movement of the natural musculoskeletal system. The right functioning of natural synovial joints ensures well lubricated contact surfaces with a very low friction coefficient and wear of cartilage tissue. The present paper deals with a new method for visualization of lubricating film with simultaneous measurements of the friction coefficient. This can contribute to better understanding of lubricating film formation in a natural synovial joint. A newly developed device, a reciprocating tribometer, is used to allow for simultaneous measurement of friction forces with contact visualization by fluorescence microscopy. The software allowing for snaps processing and subsequent evaluation of fluorescence records is developed. The evaluation software and the follow-up evaluation procedure are also described. The experiments with cartilage samples and model synovial fluid are carried out, and the new software is applied to provide their evaluation. The primary results explaining a connection between lubrication and friction are presented. The results show a more significant impact of albumin proteins on the lubrication process, whereas its clusters create a more stable lubrication layer. A decreasing trend of protein cluster count, which corresponds to a decrease in the thickness of the lubrication film, is found in all experiments. The results highlight a deeper connection between the cartilage friction and the lubrication film formation, which allows for better understanding of the cartilage lubrication mechanism.

Downregulation of miR-34a Promotes Proliferation and Inhibits Apoptosis of Rat Osteoarthritic Cartilage Cells by Activating PI3K/Akt Pathway

Objective

To elucidate the expression and function of miR-34a in rat osteoarthritic cartilage cells, and further to explore its mechanism.

Material and Methods

Rat model of osteoarthritis was constructed and knee joint cartilage cells were isolated in vitro. Immunocytochemical staining was used for identification. qRT-PCR was used to detect the expression of miR-34a in cartilaginous tissues and cartilage cells. Cartilage cells were divided into blank control (BC), negative control (NC), miR-34a inhibitor (34aI), osteoarthritis model (OA), osteoarthritis model + negative control (OA + NC) and osteoarthritis model + miR-34a inhibitor (OA + 34aI) groups. Cell proliferation was detected by CCK-8 and colony formation assays. Cell apoptosis was studied by flow cytometry and Western blot. PI3K/AKT-pathway-related proteins were also analyzed by Western blot. To further validate the effect of miR-34a on the PI3K/Akt pathway, the cartilage cells were divided into blank control (BC), osteoarthritis model (OA), osteoarthritis model + miR-34a inhibitor (OA + 34aI), osteoarthritis model + PI3K activator (OA + IGF-1) and osteoarthritis model + miR-34a inhibitor + PI3K inhibitor (OA + 34aI + LY) groups, the experiments above were repeated.

Results

The expression of miR-34a in cartilaginous tissues and cells of osteoarthritis model was significantly higher than that in normal (p < 0.05). After silencing miR-34a gene, the cell proliferation and proteins expression of PI3K/Akt pathway were increased, while the apoptosis rate and expression of apoptosis-related proteins were decreased. Addition of PI3K activator also evidently promoted proliferation and inhibited apoptosis. The protein expression of Bax, Cleaved caspase-3 and Cleaved caspase-9 were dramatically decreased, while the ratios of p-PI3K/PI3K and p-Akt/Akt were increased in OA + IGF-1 group.

Conclusion

Downregulation of miR-34a regulated proliferation and apoptosis of cartilage cells by activating PI3K/Akt pathway, providing a potential therapeutic approach for the treatment of osteoarthritis.

Level of pain, muscle strength and posture: effects of PBM on an exercise program in women with knee osteoarthritis - a randomized controlled trial

To evaluate the effectiveness of an exercise program associated to photobiomodulation (PBM) on pain, postural changes, functionally, and muscular strength in women, one of the risk factors, with knee osteoarthritis (OA). A randomized controlled trial, with a blinded assessor and intention-to-treat analysis and placebo control. Sixty-two participants with knee OA (with confirmed radiological diagnosis) were evaluated for this study. However, 34 were considered eligible and were randomized into two groups: EPPG - exercise and PBM placebo group (n = 17) and EPAG - exercise and PBM active group (n = 16), but one participant was excluded of EPAG. The exercise program and PBM (808 nm, 100 mW/point, 4 J/point, 56 J total, 91 J/cm²) were realized twice a week, during 8 weeks. West Ontario and the McMaster University Osteoarthritis Index (WOMAC) and Lequesne questionnaires, 1-repetition maximum test (1-RM) and posture evaluation software (SAPO) were used to analyze the effects of the therapies. In intragroup analysis, a significant improvement in pain WOMAC (p < 0.001), stiffness (p < 0.001), function (p < 0.001), Lequesne (p < 0.001), and 1-RM (all muscle groups) (p < 0.001) were observed. In this study, the exercise program improved pain, function, and muscle strength of all the participants. However, PBM, in the parameters used, did not optimize the effects of the exercise program in women with knee OA.

Effect of a Moderate-Intensity Aerobic Training on Joint Biomarkers and Functional Adaptations in Rats Subjected to Induced Knee Osteoarthritis

Background

Knee osteoarthritis (_kOA) is a common chronic disease that induces changes in redox status and inflammatory biomarkers, cell death, and motor impairment. Aerobic training can be a non-pharmacological alternative to prevent the progression of the disease.

Objective

To evaluate the effects of an 8 weeks moderate-intensity treadmill aerobic training program on redox status and inflammatory biomarkers and motor performance in _kOA-like changes induced by monosodium iodoacetate (MIA) in rats.

Methods

Twenty-seven rats were randomly divided into three groups: SHAM; induced _kOA (OA); and induced _kOA + aerobic training (OAE). Motor performance was evaluated by the number of falls on rotarod test, the total time of displacement and the number of failures on a 100 cm footbridge. Data for cytokines and histology were investigated locally, whereas plasma was used for redox status biomarkers.

Results

The OA group, compared to the SHAM group, increased 1.13 times the total time of displacement, 6.05 times the number of failures, 2.40 times the number of falls. There was also an increase in cytokine and in thiobarbituric acid reactive substances (TBARS) (IL1β: 5.55-fold, TNF: 2.84-fold, IL10: 1.27-fold, IL6: 1.50-fold, TBARS: 1.14-fold), and a reduction of 6.83% in the total antioxidant capacity (FRAP), and of 35% in the number of chondrocytes. The aerobic training improved the motor performance in all joint function tests matching to SHAM scores. Also, it reduced inflammatory biomarkers and TBARS level at values close to those of the SHAM group, with no change in FRAP level. The number of falls was explained by IL1β and TNF (58%), and the number of failures and the total time of displacement were also explained by TNF (29 and 21%, respectively).

Conclusion

All findings indicate the efficacy of moderate-intensity aerobic training to regulate inflammatory biomarkers associated with improved motor performance in induced _kOA-like changes, thus preventing the loss of chondrocytes.

NF-κB Signaling Pathways in Osteoarthritic Cartilage Destruction

Osteoarthritis (OA) is a type of joint disease associated with wear and tear, inflammation, and aging. Mechanical stress along with synovial inflammation promotes the degradation of the extracellular matrix in the cartilage, leading to the breakdown of joint cartilage. The nuclear factor-kappaB (NF-κB) transcription factor has long been recognized as a disease-contributing factor and, thus, has become a therapeutic target for OA. Because NF-κB is a versatile and multi-functional transcription factor involved in various biological processes, a comprehensive understanding of the functions or regulation of NF-κB in the OA pathology will aid in the development of targeted therapeutic strategies to protect the cartilage from OA damage and reduce the risk of potential side-effects. In this review, we discuss the roles of NF-κB in OA chondrocytes and related signaling pathways, including recent findings, to better understand pathological cartilage remodeling and provide potential therapeutic targets that can interfere with NF-κB signaling for OA treatment.

Redox and NF-κB signaling in osteoarthritis

Human cells have to deal with the constant production of reactive oxygen species (ROS). Although ROS overproduction might be harmful to cell biology, there are plenty of data showing that moderate levels of ROS control gene expression by maintaining redox signaling. Osteoarthritis (OA) is the most common joint disorder with a multi-factorial etiology including overproduction of ROS. ROS overproduction in OA modifies intracellular signaling, chondrocyte life cycle, metabolism of cartilage matrix and contributes to synovial inflammation and dysfunction of the subchondral bone. In arthritic tissues, the NF-κB signaling pathway can be activated by pro-inflammatory cytokines, mechanical stress, and extracellular matrix degradation products. This activation results in regulation of expression of many cytokines, inflammatory mediators, transcription factors, and several matrix-degrading enzymes. Overall, NF-κB signaling affects cartilage matrix remodeling, chondrocyte apoptosis, synovial inflammation, and has indirect stimulatory effects on downstream regulators of terminal chondrocyte differentiation. Interaction between redox signaling and NF-κB transcription factors seems to play a distinctive role in OA pathogenesis.

Mechanical stress protects against osteoarthritis via regulation of the AMPK/NF-κB signaling pathway

Mechanical stress plays a key role in regulating cartilage degradation in osteoarthritis (OA). The aim of this study was to evaluate the effects and mechanisms of mechanical stress on articular cartilage. A total of 80 male Sprague‐Dawley rats were randomly divided into eight groups (n = 10 for each group): control group (CG), OA group (OAG), and CG or OAG subjected to low‐, moderate‐, or high‐intensity treadmill exercise (CL, CM, CH, OAL, OAM, and OAH, respectively). Chondrocytes were obtained from the knee joints of rats; they were cultured on Bioflex 6‐well culture plates and subjected to different durations of cyclic tensile strain (CTS) with or without exposure to interleukin‐1β (IL‐1β). The results of the histological score, immunohistochemistry, enzyme‐linked immunosorbent assay, and western‐blot analyses indicated that there were no differences between CM and CG, but OAM showed therapeutic effects compared with OAG. However, CH and OAH experienced more cartilage damage than CG and OAG, respectively. CTS had no therapeutic effects on collagen II of normal chondrocytes, which is consistent with findings after treadmill exercise. However, CTS for 4 hr could alleviate the chondrocyte damage induced by IL‐1β by activating AMP‐activated protein kinase (AMPK) phosphorylation and suppressing nuclear translocation of nuclear factor (NF)‐κB p65. Our findings indicate that mechanical stress had no therapeutic effects on normal articular cartilage and chondrocytes; mechanical stress only caused damage with excessive stimulation. Still, moderate biomechanical stress could reduce sensitization to the inflammatory response of articular cartilage and chondrocytes through the AMPK/NF‐κB signaling pathway.

Mithramycin A Alleviates Osteoarthritic Cartilage Destruction by Inhibiting HIF-2α Expression

Osteoarthritis (OA) is the most common and increasing joint disease worldwide. Current treatment for OA is limited to control of symptoms. The purpose of this study was to determine the effect of specificity protein 1 (SP1) inhibitor Mithramycin A (MitA) on chondrocyte catabolism and OA pathogenesis and to explore the underlying molecular mechanisms involving SP1 and other key factors that are critical for OA. Here, we show that MitA markedly inhibited expressions of matrix-degrading enzymes induced by pro-inflammatory cytokine interleukin-1β (IL-1β) in mouse primary chondrocytes. Intra-articular injection of MitA into mouse knee joint alleviated OA cartilage destruction induced by surgical destabilization of the medial meniscus (DMM). However, modulation of SP1 level in chondrocyte and mouse cartilage did not alter catabolic gene expression or cartilage integrity, respectively. Instead, MitA significantly impaired the expression of HIF-2α known to be critical for OA pathogenesis. Such reduction in expression of HIF-2α by MitA was caused by inhibition of NF-κB activation, at least in part. These results suggest that MitA can alleviate OA pathogenesis by suppressing NF-κB-HIF-2α pathway, thus providing insight into therapeutic strategy for OA.

Interleukin-6 from subchondral bone mesenchymal stem cells contributes to the pathological phenotypes of experimental osteoarthritis

As a main cause of morbidity in the aged population, osteoarthritis (OA) is characterized by cartilage destruction, synovium inflammation, osteophytes, and subchondral bone sclerosis. To date its etiology remains elusive. Recent data highlight an important role of subchondral bone in the onset and progression of OA. Therefore, elucidating the mechanisms underlying abnormal subchondral bone could be of importance in the treatment of OA. Interleukin-6 is a proinflammatory cytokine involved in many physiological and pathological processes. Although in vitro and in vivo studies have indicated that IL-6 is an important cytokine in the physiopathogenesis of OA, its effects on subchondral bone have not been studied in OA animal models. In this study, we aimed to i) investigate the role of IL-6 in the pathological phenotypes of OA subchondral bone MSCs including increase in cell numbers, mineralization disorder and abnormal type I collagen production; ii) explore whether the systemic blockade of IL-6 signaling could alleviate the pathological phenotypes of experimental OA. We found that IL-6 was over-secreted by OA subchondral bone MSCs compared with normal MSCs and IL-6/STAT3 signaling was over-activated in subchondral bone MSCs, which contributed to the pathological phenotypes of OA subchondral bone MSCs. More importantly, systemic inhibition of IL-6/STAT3 signaling with IL-6 antibody or STAT3 inhibitor AG490 decreased the severity of pathological phenotypes of OA subchondral bone MSCs and cartilage lesions in OA. Our findings provide strong evidence for a pivotal role for IL-6 signaling in OA and open up new therapeutic perspectives.

Jaw closing movement and sex differences in temporomandibular joint energy densities

Energy densities (ED, mJ/mm3 ) quantify mechanical work imposed on articular cartilages during function. This cross-sectional study examined differences in temporomandibular joint (TMJ) ED during asymmetric versus symmetric jaw closing in healthy females versus males. ED component variables were tested for differences between and within sexes for two types of jaw closing. Seventeen female and 17 male subjects gave informed consent to participate. Diagnostic criteria for temporomandibular disorders and images (magnetic resonance (MR), computed tomography) were used to confirm healthy TMJ status. Numerical modelling predicted TMJ loads (Fnormal ) consequent to unilateral canine biting. Dynamic stereometry combined MR imaging and jaw-tracking data to measure ED component variables during 10 trials of each type of jaw closing in each subject's TMJs. These data were then used to calculate TMJ ED during jaw closing asymmetrically and symmetrically. Paired and Student's t tests assessed ED between jaw closing movements and sexes, respectively. Multivariate data analyses assessed ED component variable differences between jaw closing movements and sexes (α = 0.05). Contralateral TMJ ED were 3.6-fold and significantly larger (P < .0001) during asymmetric versus symmetric jaw closing, due to significantly larger (P ≤ .001) distances of TMJ stress-field translation in asymmetric versus symmetric movement. During asymmetric jaw closing, contralateral TMJ ED were twofold and significantly larger (P = .036) in females versus males, due to 1.5-fold and significantly smaller (P ≤ .010) TMJ disc cartilage volumes under stress fields in females versus males. These results suggest that in healthy individuals, asymmetric compared to symmetric jaw closure in females compared to males has higher TMJ mechanical fatigue liabilities.

The effects of different frequency treadmill exercise on lipoxin A4 and articular cartilage degeneration in an experimental model of monosodium iodoacetate-induced osteoarthritis in rats

The aim was to investigate the effects of different frequencies treadmill exercise with total exercise time being constancy on articular cartilage, lipoxin A₄ (LXA₄) and the NF-κB pathway in rat model of monosodium iodoacetate-induced osteoarthritis (OA). Fifty male Sprague-Dawley rats were randomly divided into five groups (n = 10): controls (CG), knee OA model (OAG), OA + treadmill exercise once daily (OAE1), OA + treadmill exercise twice daily, rest interval between exercise>4h (OAE2) and OA + treadmill exercise three times daily, rest interval between exercise>4h (OAE3). Rats were evaluated after completing the treadmill exercise program (speed, 18 m/min; total exercise time 60 min/day; 5 days/week for 8 weeks). Interleukin (IL)-1β, tumor necrosis factor (TNF)-α, and LXA₄ in serum and intra-articular lavage fluid were measured by ELISA. Changes in articular cartilage were evaluated by histology, immunohistochemistry, western blotting and quantitative real-time-PCR. LXA₄ in the serum and intra-articular lavage fluid increased in all OAE groups, and histological evaluation indicated that the OAE3 group had the best treatment response. The expression of COL2A1 and IκB-β in articular cartilage increased in all OAE groups vs the OAG group, whereas expression of IL-1β, TNF-α, matrix metalloproteinase (MMP)-13, and NF-κB p65 was reduced in all OAE groups compared with the OAG. Under the condition of 60 min treadmill exercise with moderate-intensity, to fulfill in three times would have better chondroprotective effects than to fulfill in two or one time on monosodium iodoacetate-induced OA in rats. And it may be worked through the anti-inflammatory activity of LXA₄ and the NF-κB pathway.

Systemic inhibition of IL-6/Stat3 signalling protects against experimental osteoarthritis

Objective

To investigate the impact of systemic inhibition of interleukin 6 (IL-6) or signal transducer and activator of transcription (Stat3) in an experimental model of osteoarthritis (OA).

Methods

Expression of major catabolic and anabolic factors of cartilage was determined in IL-6-treated mouse chondrocytes and cartilage explants. The anti-IL-6-receptor neutralising antibody MR16-1 was used in the destabilisation of the medial meniscus (DMM) mouse model of OA. Stat3 blockade was investigated by the small molecule Stattic ex vivo and in the DMM model.

Results

In chondrocytes and cartilage explants, IL-6 treatment reduced proteoglycan content with increased production of matrix metalloproteinase (MMP-3 and MMP-13) and a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS-4 and ADAMTS-5). IL-6 induced Stat3 and extracellular signal-regulated kinase (ERK) 1/2 signalling but not p38, c-Jun N-terminal kinase or Akt. In the DMM model, Stat3 was activated in cartilage, but neither in the synovium nor in the subchondral bone. Systemic blockade of IL-6 by MR16-1 alleviated DMM-induced OA cartilage lesions, impaired the osteophyte formation and the extent of synovitis. In the same model, Stattic had similar beneficial effects on cartilage and osteophyte formation. Stattic, but not an ERK1/2 inhibitor, significantly counteracted the catabolic effects of IL-6 on cartilage explants and suppressed the IL-6-induced chondrocytes apoptosis.

Conclusion

IL-6 induces chondrocyte catabolism mainly via Stat3 signalling, a pathway activated in cartilage from joint subjected to DMM. Systemic blockade of IL-6 or STAT-3 can alleviate DMM-induced OA in mice.

Exercise-driven metabolic pathways in healthy cartilage

OBJECTIVE

Exercise is vital for maintaining cartilage integrity in healthy joints. Here we examined the exercise-driven transcriptional regulation of genes in healthy rat articular cartilage to dissect the metabolic pathways responsible for the potential benefits of exercise.

METHODS

Transcriptome-wide gene expression in the articular cartilage of healthy Sprague-Dawley female rats exercised daily (low intensity treadmill walking) for 2, 5, or 15 days was compared to that of non-exercised rats, using Affymetrix GeneChip arrays. Database for Annotation, Visualization and Integrated Discovery (DAVID) was used for Gene Ontology (GO)-term enrichment and Functional Annotation analysis of differentially expressed genes (DEGs). Kyoto Encyclopedia of Genes and Genome (KEGG) pathway mapper was used to identify the metabolic pathways regulated by exercise.

RESULTS

Microarray analysis revealed that exercise-induced 644 DEGs in healthy articular cartilage. The DAVID bioinformatics tool demonstrated high prevalence of functional annotation clusters with greater enrichment scores and GO-terms associated with extracellular matrix (ECM) biosynthesis/remodeling and inflammation/immune response. The KEGG database revealed that exercise regulates 147 metabolic pathways representing molecular interaction networks for Metabolism, Genetic Information Processing, Environmental Information Processing, Cellular Processes, Organismal Systems, and Diseases. These pathways collectively supported the complex regulation of the beneficial effects of exercise on the cartilage.

CONCLUSIONS

Overall, the findings highlight that exercise is a robust transcriptional regulator of a wide array of metabolic pathways in healthy cartilage. The major actions of exercise involve ECM biosynthesis/cartilage strengthening and attenuation of inflammatory pathways to provide prophylaxis against onset of arthritic diseases in healthy cartilage.

Aerobic exercise training and low-level laser therapy modulate inflammatory response and degenerative process in an experimental model of knee osteoarthritis in rats

OBJECTIVE

The aim of this study was to evaluate the effects of an aerobic exercise training and low-level laser therapy (LLLT) (associated or not) on degenerative modifications and inflammatory mediators on the articular cartilage using an experimental model of knee OA.

MATERIAL AND METHODS

Fifty male Wistar rats were randomly divided into five groups: control group (CG); knee OA control group (OAC); OA plus exercise training group (OAT); OA plus LLLT group (OAL); OA plus exercise training associated with LLLT group (OATL). The exercise training (treadmill; 16 m/min; 50 min/day) and the laser irradiation (two points-medial and lateral side of the left joint; 24 sessions) started 4 weeks after the surgery, 3 days/week for 8 weeks.

RESULTS

The results showed that all treated groups showed (irradiated or not) a better pattern of tissue organization, with less fibrillation and irregularities along the articular surface and chondrocytes organization, a lower degenerative process measured by OARSI score and higher thickness values. Additionally, all treated group showed a reduced expression in IL-1β, caspase-3 and MMP-13 compared to OAC. Moreover, a lower caspase-3 expression was observed in OATL compared to OAL and OAT.

CONCLUSION

These results suggest that exercise training and LLLT were effective in preventing cartilage degeneration and modulating inflammatory process induced by knee OA.

Effects of exercise on physical limitations and fatigue in rheumatic diseases

Physical activity covers not just sports but also simple everyday movements such as housework, walking and playing. Regular exercise has a great importance in maintaining good health, indeed inactivity is a risk factor for different chronic diseases. Physical exercise can play a crucial role in the treatment of rheumatic diseases, optimizing both physical and mental health, enhancing energy, decreasing fatigue and improving sleep. An exercise program for patients with rheumatic diseases aims to preserve or restore a range of motion of the affected joints, to increase muscle strength and endurance, and to improve mood and decrease health risks associated with a sedentary lifestyle. In this editorial I describe the benefits of the exercise on physical limitations and fatigue in rheumatic diseases that seem to have a short and long-term effectiveness. A literature review was conducted on PubMed, Scopus and Google Scholar using appropriate keywords based on the present editorial.

Runx1 Activities in Superficial Zone Chondrocytes, Osteoarthritic Chondrocyte Clones and Response to Mechanical Loading

Runx1, the hematopoietic lineage determining transcription factor, is present in perichondrium and chondrocytes. Here we addressed Runx1 functions, by examining expression in cartilage during mouse and human osteoarthritis (OA) progression and in response to mechanical loading. Spared and diseased compartments in knees of OA patients and in mice with surgical destabilization of the medial meniscus were examined for changes in expression of Runx1 mRNA (Q-PCR) and protein (immunoblot, immunohistochemistry). Runx1 levels were quantified in response to static mechanical compression of bovine articular cartilage. Runx1 function was assessed by cell proliferation (Ki67, PCNA) and cell type phenotypic markers. Runx1 is enriched in superficial zone (SZ) chondrocytes of normal bovine, mouse, and human tissues. Increasing loading conditions in bovine cartilage revealed a positive correlation with a significant elevation of Runx1. Runx1 becomes highly expressed at the periphery of mouse OA lesions and in human OA chondrocyte 'clones' where Runx1 co-localizes with Vcam1, the mesenchymal stem cell (MSC) marker and lubricin (Prg4), a cartilage chondroprotective protein. These OA induced cells represent a proliferative cell population, Runx1 depletion in MPCs decreases cell growth, supporting Runx1 contribution to cell expansion. The highest Runx1 levels in SZC of normal cartilage suggest a function that supports the unique phenotype of articular chondrocytes, reflected by upregulation under conditions of compression. We propose Runx1 co-expression with Vcam1 and lubricin in murine cell clusters and human 'clones' of OA cartilage, participate in a cooperative mechanism for a compensatory anabolic function.

New developments in the treatment of osteoarthritis - focus on biologic agents

Osteoarthritis (OA) is one of the most common diseases around the world. Medical, social, and financial consequences oblige clinicians, surgeons, and researchers to focus on finding the best treatment option, to eradicate and stop this degenerative joint disease, in order to avoid surgical options which in many instances are over-indicated. Noninvasive treatments, such as anti-inflammatory drugs, physiotherapy, orthotic devices, dietary supplements, have demonstrated lack of effectiveness. The possibility to perform intra-articular injections with hyaluronic acid, corticosteroids, or the newest but criticized treatment based on platelet-rich plasma (PRP) has changed the management of OA disease. The use of PRP has led to many differences in treatment since there is a lack of consensus about protocols, indications, number of doses, cost-effectiveness, and duration of the treatment. Many publications have suggested efficacy in tendon injuries, but when PRP has been indicated to treat cartilage injuries, things are more inconsistent. Some authors have reported their experience treating OA with PRP, and it seems that, if well indicated, it is an option as a supplementary therapy. Therefore, we need to understand that OA is a mechanical disease which not only produces changes in radiographs, but also affects the quality of life. Pathogenesis of OA has been well explained, providing us new knowledge and future possibilities to improve the clinical approach. From basic science to surgery, there is a great field we all need to contribute to, because the general population is aging and total joint replacements should not be the only solution for OA. So herein is an actual review of the developments for treating OA with biologics, intended to be useful for the population inside orthopedics who could be called bio-orthopedists, since OA is a molecular homeostasis disbalance between catabolism and anabolism triggered by mechanical stress.

Exercise modulates the expression of IL-1β and IL-10 in the articular cartilage of normal and osteoarthritis-induced rats

After a joint lesion, high-impact exercise is a risk factor for the development of osteoarthritis (OA). The degradation of articular cartilage in OA has been associated with the activation of inflammatory cytokine signaling pathways. However, differences in cytokine expression in healthy and injured cartilage after exercise have not yet been analyzed. We used immunofluorescence and Western blot to study the expression of IL-1β and IL-10 in the articular cartilage of normal (N), sham-operated (S), and menisectomized (OA) rats subjected or not to high-impact exercise (E) for 3, 6, and 10 days (N, NE, S, SE, and OA groups). Cartilage integrity and proteoglycan content were only affected in the OA groups. Exercise increased the amount of IL-1β and IL-10 positive chondrocytes in NE and SE groups compared with non-exercised groups (N and S). The expression of IL-1β was up-regulated over time in the NE and OA groups, although in the late stages the increase was higher in the OA groups. In contrast, the expression of anti-inflammatory IL-10 was low in the OA group, whereas in the NE groups expression levels were higher at each time point analyzed. These results suggest that anti- and pro-inflammatory molecules in the cartilage might be tightly regulated to maintain the integrity of the tissue and that when this equilibrium is broken (when the meniscus is removed), the pro-inflammatory cytokines take over and OA develops.

Controlled chondrogenesis from adipose-derived stem cells by recombinant transforming growth factor-β3 fusion protein in peptide scaffolds

Adipose-derived stem cells (ADSCs) are promising for cartilage repair due to their easy accessibility and chondrogenic potential. Although chondrogenesis of transforming growth factor-β (TGF-β) mediated mesenchymal stem cells (MSCs) is well established in vitro, clinical tissue engineering requires effective and controlled delivery of TGF-β in vivo. In this work, a self-assembled peptide scaffold was employed to construct cartilages in vivo through the chondrogenesis from ADSCs controlled by recombinant fusion protein LAP-MMP-mTGF-β3 that was transfected by lentiviral vectors. During this course, the addition of matrix metalloproteinases (MMPs) can trigger the release of mTGF-β3 from the recombinant fusion protein of LAP-MMP-mTGF-β3 in the combined scaffolds, thus stimulating the differentiation of ADSCs into chondrogenesis. The specific expression of cartilage genes was analyzed by real-time polymerase chain reaction and Western blot. The expression of chondrocytic markers was obviously upregulated to a higher level compared to the one by commonly used TGF-β3 alone. After 3 weeks of in vitro culturing, the hybrids with differentiated chondrogenesis were then injected subcutaneously into nude mice and retrieved after 4 weeks of culturing in vivo. Histological analysis also confirmed that the recombinant fusion protein was more effective for the formation of cartilage matrix than the cases either with TGF-β3 alone or without LAP-MMP-mTGF-β3 (P<0.05). This study demonstrates that controlled local delivery of the LAP-MMP-mTGF-β3 constructs can accelerate differentiation of ADSCs into the cartilage in vivo, which indicates the great potential of this hybrid in rapid therapy of osteoarthritis.

Anti-inflammatory strategies in cartilage repair

Cartilage defects are normally concomitant with posttraumatic inflammation and pose a major challenge in cartilage repair. Due to the avascular nature of cartilage and its inability to surmount an inflammatory response, the cartilage is easily attacked by proinflammatory factors and oxidative stress; if left untreated, osteoarthritis may develop. Suppression of inflammation has always been a crux for cartilage repair. Pharmacological drugs have been successfully applied in cartilage repair; however, they cannot optimally work alone. This review article will summarize current pharmacological drugs and their application in cartilage repair. The development of extracellular matrix-based scaffolds and preconditioned tissue-specific stem cells will be emphasized because both of these tissue engineering components could contribute to an enhanced ability not only for cartilage regeneration but also for anti-inflammation. These strategies could be combined to boost cartilage repair under inflammatory conditions.

Homeostatic mechanisms in articular cartilage and role of inflammation in osteoarthritis

Osteoarthritis (OA) is a whole joint disease, in which thinning and disappearance of cartilage is a critical determinant in OA progression. The rupture of cartilage homeostasis whatever its cause (aging, genetic predisposition, trauma or metabolic disorder) induces profound phenotypic modifications of chondrocytes, which then promote the synthesis of a subset of factors that induce cartilage damage and target other joint tissues. Interestingly, among these factors are numerous components of the inflammatory pathways. Chondrocytes produce cytokines, chemokines, alarmins, prostanoids, and adipokines and express numerous cell surface receptors for cytokines and chemokines, as well as Toll-like receptors. These receptors activate intracellular signaling pathways involved in inflammatory and stress responses of chondrocytes in OA joints. This review focuses on mechanisms responsible for the maintenance of cartilage homeostasis and highlights the role of inflammatory processes in OA progression.

Low oxygen tension increased fibronectin fragment induced catabolic activities--response prevented with biomechanical signals

Introduction

The inherent low oxygen tension in normal cartilage has implications on inflammatory conditions associated with osteoarthritis (OA). Biomechanical signals will additionally contribute to changes in tissue remodelling and influence the inflammatory response. In this study, we investigated the combined effects of oxygen tension and fibronectin fragment (FN-f) on the inflammatory response of chondrocytes subjected to biomechanical signals.

Methods

Chondrocytes were cultured under free-swelling conditions at 1%, 5% and 21% oxygen tension or subjected to dynamic compression in an ex vivo 3D/bioreactor model with 29 kDa FN-f, interleukin-1beta (IL-1β) and/or the nitric oxide synthase (NOS) inhibitor for 6 and 48 hours. Markers for catabolic activity (NO, PGE₂), tissue remodelling (GAG, MMPs) and cytokines (IL-1β, IL-6 and TNFα) were quantified by biochemical assay. Aggrecan, collagen type II, iNOS and COX-2 gene expression were examined by real-time quantitative PCR. Two-way ANOVA and a post hoc Bonferroni-corrected t-test were used to analyse data.

Results

Both FN-fs and IL-1β increased NO, PGE₂ and MMP production (all P < 0.001). FN-f was more active than IL-1β with greater levels of NO observed at 5% than 1% or 21% oxygen tension (P < 0.001). Whilst FN-f reduced GAG synthesis at all oxygen tension, the effect of IL-1β was significant at 1% oxygen tension. In unstrained constructs, treatment with FN-f or IL-1β increased iNOS and COX-2 expression and reduced aggrecan and collagen type II (all P < 0.001). In unstrained constructs, FN-f was more effective than IL-1β at 5% oxygen tension and increased production of NO, PGE₂, MMP, IL-1β, IL-6 and TNFα. At 5% and 21% oxygen tension, co-stimulation with compression and the NOS inhibitor abolished fragment or cytokine-induced catabolic activities and restored anabolic response.

Conclusions

The present findings revealed that FN-fs are more potent than IL-1β in exerting catabolic effects dependent on oxygen tension via iNOS and COX-2 upregulation. Stimulation with biomechanical signals abolished catabolic activities in an oxygen-independent manner and NOS inhibitors supported loading-induced recovery resulting in reparative activities. Future investigations will utilize the ex vivo model as a tool to identify key targets and therapeutics for OA treatments.

Manual khalifa therapy in patients with completely ruptured anterior cruciate ligament in the knee: first results from near-infrared spectroscopy

Background:

Manual Khalifa therapy has been practiced in Hallein, Austria, for more than 30 years; however, there are no scientific results available on the topic.

Aims:

The goal of the present study was to investigate possible acute effects of Khalifa therapy on regional oxygen saturation of knee tissues in patients with completely ruptured anterior cruciate ligament.

Materials and Methods:

We investigated 10 male patients (mean age ± standard deviation (SD) 35.9 ± 6.1 year) using a four-channel oximeter. The sensors were applied anterolaterally and anteromedially, beside the patella, on both the injured and the healthy (control) knee.

Results:

The results of the controlled study showed that values of oxygen saturation on the knee with the ruptured ligament were significantly increased (P < 0.001) immediately after Khalifa therapy, whereas the values on the control knee showed insignificant increases. Baselines values of the anterolateral side of the injured knee were significantly (P < 0.001) different from those of the anterolateral side of the control knee. The same effect was present on the anteromedial side; however, with a lower degree of significance (P < 0.05).

Conclusions:

Khalifa therapy was clinically successful in all 10 patients. Further, investigations and analyzes are necessary to explain the underlying mechanism.

Muscle cell-derived factors inhibit inflammatory stimuli-induced damage in hMSC-derived chondrocytes

OBJECTIVE

Pro-inflammatory cytokines play an important role in inducing cartilage degradation during osteoarthritis pathogenesis. Muscle is a tissue that lies near cartilage in situ. However, muscle's non-loading biochemical effect on cartilage has been largely unexplored. Here, we tested the hypothesis that muscle cells can regulate the response to pro-inflammatory cytokine-mediated damage in chondrocytes derived from human bone marrow-derived mesenchymal stem cells (hMSCs).

METHOD

hMSCs were allowed to undergo chondrogenic differentiation in porous silk scaffolds in the typical chondrogenic medium for 12 days. For the next 9 days, the cells were cultured in chondrogenic medium containing 50% conditioned medium derived from C2C12 muscle cells or fibroblast control cells, and were subject to treatments of pro-inflammatory cytokines IL-1β or TNFα.

RESULTS

Both IL-1β and TNFα-induced strong expression of multiple MMPs and hypertrophic markers Runx2 and type X collagen. Strikingly, culturing hMSC-derived chondrocytes in C2C12 muscle cell-conditioned medium strongly inhibited the expression of all these genes, a result further confirmed by GAG content and histological evaluation of matrix protein. To determine whether these effects were due to altered chondrocyte growth and survival, we assayed the expression of cell proliferation marker Ki67, cell cycle arrest markers p21 and p53, and apoptosis marker caspase 3. Muscle cell-conditioned medium promoted proliferation and inhibited apoptosis, thereby suggesting a possible decrease in the cellular aging and death that typically accompanies cartilage inflammation.

CONCLUSION

Our findings suggest the role of muscle in cartilage homeostasis and provide insight into designing strategies for promoting resistance to pro-inflammatory cytokines in hMSC-derived chondrocytes.

A biological therapy to osteoarthritis treatment using platelet-rich plasma

INTRODUCTION

Osteoarthritis (OA) is a degenerative disease affecting the synovial joint. It is caused by cells exposure to non-physiological stimuli, either mechanical or biochemical, and the loss of bone-cartilage homeostasis. Some of these changes, however, may be reversed by the use of single or combined growth factors, suggesting that the treatment of OA could be addressed using a pool of growth factors.

AREAS COVERED

This review addresses current molecular and biological knowledge and implicates the recapitulation of some developmental processes during endochondral ossification in OA aetiology and pathogenesis. Platelets act as carriers of endogenous morphogens that may modulate cell fate and therefore affect joint tissues structure and function. We shed light on the platelet-rich plasma effects on biological level that might drive the osteoarthritic joint's improvement both in structure and function.

EXPERT OPINION

We present the therapeutic potential of plasma rich in growth factors (PRGF-Endoret), an endogenous biological therapy that might modulate the gene expression of cells such as chondrocytes, synoviocytes, macrophages, and mesenchymal stem cells, and thereby influence an anabolic microenvironment of synovial joint which is conducive to maintaining the homeostatic state of the joint's tissues, and hence reduce pain and improve the joint motion.

The effects of a moderate exercise program on knee osteoarthritis in male wistar rats

OBJECTIVE(S)

Osteoarthritis (OA) or degenerative joint disease is the commonest form of arthritis and can lead to joint pain, decrease in joint's range of motion, loss of function, and ultimately disability. Exercise is considered as one of the non-pharmacological treatments of OA. But the effects of exercise on knee joint cartilage remain ambiguous. The aim of the present study was to investigate the effect of a four-week moderate treadmill exercise on rats' knee osteoarthritis.

MATERIALS AND METHODS

Eighteen male Wistar rats (173 ± 1 g, 8 weeks old) were randomly divided into three groups (n = 6): Intact control, monosodium iodoacetate (MIA) only (OA), and training. The osteoarthritis model was induced by intra-articular injection of monosodium iodoacetate (MIA). Subjects followed a moderate-intensity exercise program for 28 days. Rats were killed after 28 days and histological assessment was done on their knee joints. One-way ANOVA (P<0.05) and post-hoc Tukey test was used for the statistical analysis.

RESULTS

Histological assessment on 3 measurements of, depth ratio of lesions (P=0.001), total cartilage degeneration width (P=0.001), and significant cartilage degeneration width (P=0.001), demonstrated that moderate exercise for 4 weeks could surprisingly almost treat OA symptoms of rats' knee joints.

CONCLUSION

The findings of the present study indicate that a moderate treadmill exercise program exert a beneficial influence on rats' knee osteoarthritis.

The adverse effect of elevated body mass index on outcome after autologous chondrocyte implantation

We analysed whether a high body mass index (BMI) had a deleterious effect on outcome following autologous chondrocyte implantation (ACI) or matrix-carried autologous chondrocyte implantation (MACI) for the treatment of full-thickness chondral defects of the knee from a subset of patients enrolled in the ACI vs MACI trial at The Royal National Orthopaedic Hospital.

The mean Modified Cincinnati scores (MCS) were significantly higher (p < 0.001) post-operatively in patients who had an ideal body weight (n = 53; 20 to 24.9 kg/m2) than in overweight (n = 63; 25 to 30 kg/m2) and obese patients (n = 22; > 30 kg/m2). At a follow-up of two years, obese patients demonstrated no sustained improvement in the MCS. Patients with an ideal weight experienced significant improvements as early as six months after surgery (p = 0.007). In total, 82% of patients (31 of 38) in the ideal group had a good or excellent result, compared with 49% (22 of 45) of the overweight and 5.5% (one of 18) in the obese group (p < 0.001). There was a significant negative relationship between BMI and the MCS 24 months after surgery (r = -0.4, p = 0.001).

This study demonstrates that obese patients have worse knee function before surgery and experience no sustained benefit from ACI or MACI at two years after surgery. There was a correlation between increasing BMI and a lower MCS according to a linear regression analysis. On the basis of our findings patient selection can be more appropriately targeted.

Inflammation and Joint Tissue Interactions in OA: Implications for Potential Therapeutic Approaches

It is increasingly recognized that the pathogenesis of cartilage degradation in osteoarthritis (OA) is multifactorial and involves the interactions between cartilage and its surrounding tissues. These interactions regulate proinflammatory cytokine-mediated cartilage destruction, contributing to OA progression as well as cartilage repair. This review explores the pathogenesis of OA in the context of the multiple tissue types in the joint and discusses the implications of such complex tissue interaction in the development of anti-inflammatory therapeutics for the treatment of OA.

The osteoarthritic niche and modulation of skeletal stem cell function for regenerative medicine

Osteoarthritis (OA) is the most common cause of arthritis worldwide and represents a significant healthcare burden, particularly in the context of an ageing population. Traditionally, painkillers, injections and physiotherapy have been the mainstay of treatment, with patients being referred for joint replacement surgery (arthroplasty) when these options fail. Whilst effective in reducing pain and improving joint function, these approaches are not without potential complications. With the development of tissue-engineering techniques over recent years there has been considerable interest in applying these strategies to provide new, innovative, alternative effective means of treating OA. This review explores the unique microenvironment present within an osteoarthritic joint, highlighting the features that comprise the osteoarthritic niche and could be modulated in the development of novel treatments for OA. Existing tissue-engineering strategies for repairing bone and cartilage defects are discussed, with particular reference to how these might be modified, both to improve existing treatments, such as impaction bone grafting, as well as in the development of future treatments for OA.

Computational approaches for translational clinical research in disease progression

Today, there is an ever-increasing amount of biological and clinical data available that could be used to enhance a systems-based understanding of disease progression through innovative computational analysis. In this article, we review a selection of published research regarding computational methods, primarily from systems biology, which support translational research from the molecular level to the bedside, with a focus on applications in trauma and critical care. Trauma is the leading cause of mortality in Americans younger than 45 years, and its rapid progression offers both opportunities and challenges for computational analysis of trends in molecular patterns associated with outcomes and therapeutic interventions.This review presents methods and domain-specific examples that may inspire the development of new algorithms and computational methods that use both molecular and clinical data for diagnosis, prognosis, and therapy in disease progression.

A 3D system for culturing human articular chondrocytes in synovial fluid

Cartilage destruction is a central pathological feature of osteoarthritis, a leading cause of disability in the US. Cartilage in the adult does not regenerate very efficiently in vivo; and as a result, osteoarthritis leads to irreversible cartilage loss and is accompanied by chronic pain and immobility (1,2). Cartilage tissue engineering offers promising potential to regenerate and restore tissue function. This technology typically involves seeding chondrocytes into natural or synthetic scaffolds and culturing the resulting 3D construct in a balanced medium over a period of time with a goal of engineering a biochemically and biomechanically mature tissue that can be transplanted into a defect site in vivo (3-6). Achieving an optimal condition for chondrocyte growth and matrix deposition is essential for the success of cartilage tissue engineering. In the native joint cavity, cartilage at the articular surface of the bone is bathed in synovial fluid. This clear and viscous fluid provides nutrients to the avascular articular cartilage and contains growth factors, cytokines and enzymes that are important for chondrocyte metabolism (7,8). Furthermore, synovial fluid facilitates low-friction movement between cartilaginous surfaces mainly through secreting two key components, hyaluronan and lubricin (9 10). In contrast, tissue engineered cartilage is most often cultured in artificial media. While these media are likely able to provide more defined conditions for studying chondrocyte metabolism, synovial fluid most accurately reflects the natural environment of which articular chondrocytes reside in. Indeed, synovial fluid has the advantage of being easy to obtain and store, and can often be regularly replenished by the body. Several groups have supplemented the culture medium with synovial fluid in growing human, bovine, rabbit and dog chondrocytes, but mostly used only low levels of synovial fluid (below 20%) (11-25). While chicken, horse and human chondrocytes have been cultured in the medium with higher percentage of synovial fluid, these culture systems were two-dimensional (26-28). Here we present our method of culturing human articular chondrocytes in a 3D system with a high percentage of synovial fluid (up to 100%) over a period of 21 days. In doing so, we overcame a major hurdle presented by the high viscosity of the synovial fluid. This system provides the possibility of studying human chondrocytes in synovial fluid in a 3D setting, which can be further combined with two other important factors (oxygen tension and mechanical loading) (29,30) that constitute the natural environment for cartilage to mimic the natural milieu for cartilage growth. Furthermore, This system may also be used for assaying synovial fluid activity on chondrocytes and provide a platform for developing cartilage regeneration technologies and therapeutic options for arthritis.

Engineering lubrication in articular cartilage

Despite continuous progress toward tissue engineering of functional articular cartilage, significant challenges still remain. Advances in morphogens, stem cells, and scaffolds have resulted in enhancement of the bulk mechanical properties of engineered constructs, but little attention has been paid to the surface mechanical properties. In the near future, engineered tissues will be able to withstand and support the physiological compressive and tensile forces in weight-bearing synovial joints such as the knee. However, there is an increasing realization that these tissue-engineered cartilage constructs will fail without the optimal frictional and wear properties present in native articular cartilage. These characteristics are critical to smooth, pain-free joint articulation and a long-lasting, durable cartilage surface. To achieve optimal tribological properties, engineered cartilage therapies will need to incorporate approaches and methods for functional lubrication. Steady progress in cartilage lubrication in native tissues has pushed the pendulum and warranted a shift in the articular cartilage tissue-engineering paradigm. Engineered tissues should be designed and developed to possess both tribological and mechanical properties mirroring natural cartilage. In this article, an overview of the biology and engineering of articular cartilage structure and cartilage lubrication will be presented. Salient progress in lubrication treatments such as tribosupplementation, pharmacological, and cell-based therapies will be covered. Finally, frictional assays such as the pin-on-disk tribometer will be addressed. Knowledge related to the elements of cartilage lubrication has progressed and, thus, an opportune moment is provided to leverage these advances at a critical step in the development of mechanically and tribologically robust, biomimetic tissue-engineered cartilage. This article is intended to serve as the first stepping stone toward future studies in functional tissue engineering of articular cartilage that begins to explore and incorporate methods of lubrication.

Rehabilitation after Articular Cartilage Repair of the Knee in the Football (Soccer) Player

BACKGROUND

Participation in football can put both male and female players at an increased risk for knee osteoarthritis. There is a higher prevalence of focal chondral defects in the knee of athletes compared to nonathletes. The management of chondral defects in the football player is complex and multifactorial.

OBJECTIVE

The aim of this study is to provide an overview of the current strategies for rehabilitation after articular cartilage repair of the knee in the football player.

DESIGN

A review of current literature and the scientific evidence for rehabilitation after articular cartilage repair of the knee.

CONCLUSIONS

Articular cartilage repair has been shown to allow return to sport but rehabilitation timescales are lengthy. Successful rehabilitation for a return to football after articular cartilage repair of the knee requires the player to be able to accept the load of the sport. This necessitates a multidisciplinary approach to rehabilitation, especially in the transition from therapy to performance care. It should be recognized that not all players will return to football after articular cartilage repair. The evidence base for rehabilitative practice after articular cartilage repair is increasing but remains sparse in areas.

Computational approaches for translational clinical research in disease progression

Today, there is an ever-increasing amount of biological and clinical data available that could be used to enhance a systems-based understanding of disease progression through innovative computational analysis. In this article, we review a selection of published research regarding computational methods, primarily from systems biology, which support translational research from the molecular level to the bedside, with a focus on applications in trauma and critical care. Trauma is the leading cause of mortality in Americans younger than 45 years, and its rapid progression offers both opportunities and challenges for computational analysis of trends in molecular patterns associated with outcomes and therapeutic interventions.This review presents methods and domain-specific examples that may inspire the development of new algorithms and computational methods that use both molecular and clinical data for diagnosis, prognosis, and therapy in disease progression.

Roles of inflammatory and anabolic cytokines in cartilage metabolism: signals and multiple effectors converge upon MMP-13 regulation in osteoarthritis

Human cartilage is a complex tissue of matrix proteins that vary in amount and orientation from superficial to deep layers and from loaded to unloaded zones. A major challenge to efforts to repair cartilage by stem cell-based and other tissue engineering strategies is the inability of the resident chondrocytes to lay down new matrix with the same structural and resilient properties that it had upon its original formation. This is particularly true of the collagen network, which is susceptible to cleavage once proteoglycans are depleted. Thus, a thorough understanding of the similarities and particularly the marked differences in mechanisms of cartilage remodeling during development, osteoarthritis, and aging may lead to more effective strategies for preventing cartilage damage and promoting repair. To identify and characterize effectors or regulators of cartilage remodeling in these processes, we are using culture models of primary human and mouse chondrocytes and cell lines and mouse genetic models to manipulate gene expression programs leading to matrix remodeling and subsequent chondrocyte hypertrophic differentiation, pivotal processes which both go astray in OA disease. Matrix metalloproteinases (MMP)-13, the major type II collagen-degrading collagenase, is regulated by stress-, inflammation-, and differentiation-induced signals that not only contribute to irreversible joint damage (progression) in OA, but importantly, also to the initiation/onset phase, wherein chondrocytes in articular cartilage leave their natural growth- and differentiation-arrested state. Our work points to common mediators of these processes in human OA cartilage and in early through late stages of OA in surgical and genetic mouse models.

Decrease in oxidative stress and histological changes induced by physical exercise calibrated in rats with osteoarthritis induced by monosodium iodoacetate

OBJECTIVE

The purpose of this study was to evaluate the effects of impact exercise on the joint cartilage of rats with osteoarthritis (OA) induced by monosodium iodoacetate (MIA).

METHODS

Eighteen male rats were divided into three groups of six animals each: control, OA, and OA plus exercise (OAE). The OAE group trained on a treadmill for 8 weeks. Afterward, the right joints of the animals were washed with saline solution and joint lavage was used for biochemical analyses of myeloperoxidase (MPO) and enzyme superoxide dismutase (SOD) activities and total thiol content. The same limb provided samples of the articular capsule for analyses of MPO activity and total thiol content. The left joint was used for histological analysis.

RESULTS

Our results indicate that MPO activity was increased in both OA groups in the lavage as well as the articular capsule, regardless of exercise status. SOD activity was increased in animals with OA, especially in the animals that had run on the treadmill. On the other hand, thiol content in the articular capsule and joint lavage decreased in the OA group, while the OAE group had values similar to those of the control group. The histological data indicate that animals that were submitted to running exercise showed a higher preservation rate of proteoglycan content in the superficial and intermediate areas of the joint cartilage.

CONCLUSION

Our results show that physical training contributes to the preservation of joint cartilage in animals with OA and to increase the defense mechanism against oxidative stress.

Protein geranylgeranylation controls collagenase expression in osteoarthritic cartilage

OBJECTIVE

Statins possess anti-inflammatory properties. This study was undertaken to characterize the mechanism of action of statin drugs on collagenase expression in primary human osteoarthritic cartilage tissue.

METHOD

Human articular chondrocytes and cartilage explants from osteoarthritic donors were exposed to simvastatin in the presence or absence of interleukin-1 beta (IL-1beta). Collagenase expression was determined by quantifying levels of matrix metalloproteinase 13 (MMP-13) and MMP-1 mRNA and MMP-13 protein. The mechanism of statin action was tested by addition of farnesyl pyrophosphate (FPP) and geranylgeranyl pyrophosphate (GGPP) or by using inhibitors of farnesyl transferase (FT) and geranylgeranyl transferase (GGT-1).

RESULTS

Treatment of osteoarthritic chondrocytes with simvastatin decreased mRNA levels of MMP-13 and MMP-1 whether under basal conditions or during stimulation with IL-1beta. MMP-13 protein secreted into the culture media was also decreased. Genes involved in cartilage synthesis (type II collagen and aggrecan) were not down-regulated by simvastatin. Exogenous addition of GGPP completely reversed the statin-mediated decrease in MMP-13 mRNA and protein levels whereas FPP partially reversed the statin-mediated effect. An inhibitor of GGT-1 mimicked the simvastatin-mediated reduction in MMP-13 expression by chondrocytes. Finally, consistent with impacts on MMP-13 and MMP-1 expression, simvastatin as well as the GGT-1 inhibitor both blocked type II collagen degradation in primary human articular cartilage explants.

CONCLUSION

These results suggest that statins modulate chondrocyte metabolism by reducing prenylation of key signaling molecules that control the expression of collagen-degrading enzymes. Our results strongly support the hypothesis that protein prenyltransferases including geranylgeranyl transferase regulate chondrocyte collagenase expression in osteoarthritis.

NF-kappaB signaling: multiple angles to target OA

In the context of OA disease, NF-kappaB transcription factors can be triggered by a host of stress-related stimuli including pro-inflammatory cytokines, excessive mechanical stress and ECM degradation products. Activated NF-kappaB regulates the expression of many cytokines and chemokines, adhesion molecules, inflammatory mediators, and several matrix degrading enzymes. NF-kappaB also influences the regulated accumulation and remodeling of ECM proteins and has indirect positive effects on downstream regulators of terminal chondrocyte differentiation (including beta-catenin and Runx2). Although driven partly by pro-inflammatory and stress-related factors, OA pathogenesis also involves a "loss of maturational arrest" that inappropriately pushes chondrocytes towards a more differentiated, hypertrophic-like state. Growing evidence points to NF-kappaB signaling as not only playing a central role in the pro-inflammatory stress-related responses of chondrocytes to extra- and intra-cellular insults, but also in the control of their differentiation program. Thus unlike other signaling pathways the NF-kappaB activating kinases are potential therapeutic OA targets for multiple reasons. Targeted strategies to prevent unwanted NF-kappaB activation in this context, which do not cause side effects on other proteins or signaling pathways, need to be focused on the use of highly specific drug modalities, siRNAs or other biological inhibitors that are targeted to the activating NF-kappaB kinases IKKalpha or IKKbeta or specific activating canonical NF-kappaB subunits. However, work remains in its infancy to evaluate the effects of efficacious, targeted NF-kappaB inhibitors in animal models of OA disease in vivo and to also target these strategies only to affected cartilage and joints to avoid other undesirable systemic effects.