Meniscus Osteoarthritis Research Articles

Characterization of regional meniscal cell and chondrocyte phenotypes and chondrogenic differentiation with histological analysis in osteoarthritic donor-matched tissues

Meniscus degeneration is closely related to the progression of knee osteoarthritis (OA). However, there is currently a lack of quantitative and objective metrics to assess OA meniscal cell phenotypes. In this study we investigated the phenotypic markers and chondrogenic potency of avascular and vascular meniscal cells and chondrocytes from medial OA knee joints (n = 10). Flow cytometry results showed that a significantly greater percentage of meniscal cells were positive for CD49b, CD49c and CD166 compared to donor-matched chondrocytes after 14 days in monolayer culture. The integrins, CD49b and CD29, were expressed at a significantly higher level on avascular meniscal cells derived from tissues with a more degenerated inner border than non-degenerate menisci, suggesting that the integrin family may play an important role in meniscus OA pathology. Collagen fibres arranged in a “tree-like” formation within the meniscus appeared to have less blood vessels associated with them in the vascular region of the most degenerate menisci, which may indicate that such structures are involved in the pathological process. We have demonstrated that meniscal cells derived from the lateral meniscus in medial OA patients have chondrogenic capacity in vitro and hence could represent a potential cell source to consider for meniscus tissue engineering.

Role of the Hypoxia-Inducible Factor Pathway in Normal and Osteoarthritic Meniscus and in Mice after Destabilization of the Medial Meniscus.

Meniscus injury and the hypoxia-inducible factor (HIF) pathway are independently linked to osteoarthritis pathogenesis, but the role of the meniscus HIF pathway remains unclear. We sought to identify and evaluate HIF pathway response in normal and osteoarthritic meniscus and to examine the effects of Epas1 (HIF-2α) insufficiency in mice on early osteoarthritis development. Normal and osteoarthritic human meniscus specimens were obtained and used for immunohistochemical evaluation and cell culture studies for the HIF pathway. Meniscus cells were treated with pro-inflammatory stimuli, including interleukins (IL)-1β, IL-6, transforming growth factor (TGF)-α, and fibronectin fragments (FnF). Target genes were also evaluated with HIF-1α and HIF-2α (Epas1) overexpression and knockdown. Wild-type (n = 36) and Epas1+/- (n = 30) heterozygous mice underwent destabilization of the medial meniscus (DMM) surgery and were evaluated at 2 and 4 weeks postoperatively for osteoarthritis development using histology. HIF-1α and HIF-2α immunostaining and gene expression did not differ between normal and osteoarthritic meniscus. While pro-inflammatory stimulation significantly increased both catabolic and anabolic gene expression in the meniscus, HIF-1α and Epas1 expression levels were not significantly altered. Epas1 overexpression significantly increased Col2a1 expression. Both wild-type and Epas1+/- mice developed osteoarthritis following DMM surgery. There were no significant differences between genotypes at either time point. The HIF pathway is likely not responsible for osteoarthritic changes in the human meniscus. Additionally, Epas1 insufficiency does not protect against osteoarthritis development in the mouse at early time points after DMM surgery. The HIF pathway may be more important for protection against catabolic stress.

Risk Factors for Early Total Knee Replacement after Ipsilateral Knee Arthroscopy in Patients over 55 Years of Age

Arthroscopic knee surgery (AKS) is often not successful in elderly patients with osteoarthritis and degenerative meniscus tears. Many patients require subsequent total knee replacement (TKR). We performed a case-control study to identify risk factors for early TKR following AKS in patients over 55. Data were collected on patients in an integrated healthcare system who underwent AKS between January 2010 and December 2012, and then had ipsilateral total knee replacement (TKR) within one year. Controls were matched from patients who did not have TKR within one year. Of the 7,301 AKS patients, 453 (6.2%) went on to TKR. We matched 390 cases with controls (780 total subjects); 186 subjects were excluded due to inadequate radiographs or medical records resulting in a cohort of 594 patients. Statistical analysis showed that a Kellgren-Lawrence score of 3 or 4 (OR 1.9 CI 1.3-2.8, p < 0.01), age greater than 65 (OR 2.2, CI 1.5-3.2, p < 0.01), contralateral TKR (OR 2.3, CI 1.1-5.0, p < 0.04) were associated with a higher likelihood of early TKR. Sex, race, diagnosis of diabetes, prior ipsilateral knee surgery, and prior contralateral knee surgery were not associated with early TKR. When considering AKS for older patients with degenerative arthritis and meniscus tears, care providers should consider the risk of early TKR. Older patients with advanced arthritis and a diagnosis of osteoarthritis, or combined with a meniscus tear, are especially at risk for early TKR.

Identification of lncRNA and mRNA Biomarkers in Osteoarthritic Degenerative Meniscus by Weighted Gene Coexpression Network and Competing Endogenous RNA Network Analysis.

Background Long noncoding RNAs (lncRNAs) play a crucial role in varieties of biological processes. This study is aimed at investigating meniscal degeneration-specific lncRNAs and mRNAs and their related networks in knee osteoarthritis (KOA). Methods The dataset GSE98918, which included 24 meniscus samples and related clinical data, was downloaded from the Gene Expression Omnibus database. The differentially expressed lncRNAs and mRNAs in the meniscus between KOA and control groups were identified. Based on the enriched differentially expressed lncRNAs and mRNAs, we constructed the coexpression network using WGCNA (weighted correlation network analysis) and identified the critical module related to KOA. For mRNAs in the key module, gene ontology and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analyses were carried out using the DAVID database. A competing endogenous RNA network (ceRNA) based on the screened mRNAs, lncRNAs, and related miRNAs was constructed to reveal presumptive biomarkers further. Finally, the hub lncRNAs and mRNAs were screened, and the diagnostic value was evaluated using a receiver operating characteristic (ROC) curve. Hub mRNAs were validated using the dataset GSE113825. Results We screened 208 significantly differentially expressed lncRNAs and mRNAs in menisci between the KOA and non-KOA samples, which were enriched in sixteen modules using WGCNA, especially the green module. Coexpression network based on the enriched differentially expressed lncRNAs and mRNAs in the green module uncovered 5 lncRNAs and 56 mRNAs. The lncRNA-miRNA-mRNA ceRNA network revealed that lnc-HLA-DQA1-5, lnc-RP11-127H5.1.1-1, lnc-RTN2-1, IGFBP4 (insulin-like growth factor binding protein 4), and KLF2 (Kruppel-like factor 2) were significantly correlated with the meniscus degeneration of KOA. ROC curve analysis revealed that these hub lncRNAs and mRNAs showed excellent diagnostic value for KOA. Conclusions These hub lncRNAs and mRNAs were potential prognostic biomarkers for the meniscus degeneration of KOA. Further studies are required to validate these new biomarkers and better understand the pathological process of the meniscus degeneration of KOA.

Repeatability of quantification of extrusion of the medial meniscus in knee osteoarthritis using three-dimensional models

Meniscal damage is one of risk factors for the development of knee osteoarthritis (KOA). Medial meniscal extrusion (MME) is associated with the progression of cartilage loss in the medial compartment. The objective of this study was to determine the intra-rater repeatability of our method of three-dimensionally analyzing MME in patients with KOA. Eight knees with medial KOA were examined in participants aged between fifty and eighty years old. We created three-dimensional models of the tibia and medial meniscus using a 0.4 Tesla MRI scanner and embedded a local coordinate system into the tibia. Repeatability of measurements of the MME volume and width were tested using intraclass correlation coefficient (ICC). The ICC for measuring the MME volume was 0.998 [95% confidence interval, 0.992, 1.000]. Measurement error for the MME volume was 0.5-7.0%. The ICC for measuring the MME width was 0.983 [0.924, 0.996]. Measurement error for the MME width was 0.0-11.4%. There was no correlation between the MME volume and width (r=0.565, p=0.145). This study concluded that three-dimensional volume and width measurements of the MME by a single rater using MRI images had high repeatability even in the limited image quality. The result of non-significant correlation between the MME width and volume suggests that MME width measured using a low-magnet MRI scanner not considered reliable. Further studies are needed to determine the association between the MME volume and disease progression of KOA.

Clinical Utility of Multi-Energy Spectral Photon-Counting Computed Tomography in Crystal Arthritis.

To determine whether novel multi-energy spectral photon-counting computed tomography (SPCCT) imaging can detect and differentiate between monosodium urate (MSU), calcium pyrophosphate (CPP), and hydroxyapatite (HA) crystal deposits ex vivo. A finger with a subcutaneous gouty tophus and a calcified knee meniscus excised at the time of surgery were obtained. The finger was imaged using plain x-ray, dual-energy CT (DECT), and multi-energy SPCCT. Plain x-ray and multi-energy SPCCT images of the meniscus were acquired. For validation purposes, samples of the crystals were obtained from the tophus and meniscus, and examined by polarized light microscopy and/or x-ray diffraction. As further validation, synthetic crystal suspensions of MSU, CPP, and HA were scanned using multi-energy SPCCT. Plain x-ray of the gouty finger revealed bone erosions with overhanging edges. DECT and multi-energy SPCCT both showed MSU crystal deposits; SPCCT was able to show finer detail. Plain x-ray of the calcified meniscus showed chondrocalcinosis consistent with CPP, while SPCCT showed and differentiated CPP and HA. Multi-energy SPCCT can not only detect, differentiate, and quantify MSU crystal deposits in a gouty finger ex vivo, but also specifically detect, identify, and quantify CPP within an osteoarthritic meniscus, and distinguish them from HA crystal deposits. There is potential for multi-energy SPCCT to become useful in the diagnosis of crystal arthropathies.

Quercetin attenuates oxidative stress-induced apoptosis via SIRT1/AMPK-mediated inhibition of ER stress in rat chondrocytes and prevents the progression of osteoarthritis in a rat model.

Apoptosis of chondrocytes are the main initiator of osteoarthritis (OA) and can be explained by oxidative stress and endoplasmic reticulum (ER) stress, thus the pharmacological interventions aimed at inhibiting of these pathways may be a promising approach for the management of OA. Quercetin is a member of the flavonoid family and has antioxidant and anti-inflammatory properties in degenerative diseases. However, its effects and potential mechanisms on the pathological process of OA are not very clear. The present study aimed to investigate the protective effects of quercetin on OA and the underlying mechanisms. The tert-butyl hydroperoxide (TBHP)-stimulated rat chondrocytes and destabilization of the medial meniscus OA rat model was used to explore the protective effects of quercetin. Our results showed thatquercetin treatment can attenuate oxidative stress, ER stress, and associated apoptosis. Moreover,quercetin inhibited ER stress through activating the sirtuin1/adenosine monophosphate-activated protein kinase (SIRT1/AMPK) signaling pathway. The protective effects ofquercetin were also observed in OA rat model which is evidenced by abolished cartilage degeneration and decreased chondrocytes apoptosis in the knee joints. Our results suggested thatquercetin is a promising treatment for OA.

Morphological and ultrastructural analysis of normal, injured and osteoarthritic human knee menisci.

The human meniscus plays a crucial role for transmission and distribution of load across the knee, as well as shock absorption, joint stability, lubrication, and congruity. The aim of this study was to compare the complex geometry, and unique ultrastructure and tissue composition of the meniscus in healthy (control) and pathological conditions to provide understanding of structural changes that could be helpful in the future design of targetted therapies and improvement of treatment indications. We analyzed meniscus samples collected from 3 healthy multi-organ donors (median age, 66 years), 5 patients with traumatic meniscal tear (median age, 41 years) and 3 patients undergoing total knee replacement (TKR) for end-stage osteoarthritis (OA) (median age, 72 years). We evaluated the extracellular matrix (ECM) organization, the appearance and distribution of areas of calcification, and modifications of cellular organization and structure by electron microscopy and histology. The ECM structure was similar in specimens from traumatic meniscus tears compared to those from patients with late-stage OA, showing disorganization of collagen fibers and increased proteoglycan content. Cells of healthy menisci showed mainly diffuse chromatin and well preserved organelles. Both in traumatic and in OA menisci, we observed increased chromatin condensation, organelle degeneration, and cytoplasmic vacuolization, a portion of which contained markers of autophagic vacuoles. Areas of calcification were also observed in both traumatic and OA menisci, as well as apoptotic- like features that were particularly prominent in traumatic meniscal tear samples. We conclude that meniscal tissue from patients with traumatic meniscal injury demonstrate pathological alterations characteristic of tissue from older patients undergoing TKR, suggesting that they have high susceptibility to develop OA.

Ultra-high field magnetic resonance imaging parameter mapping in the posterior horn of ex vivo human menisci

To investigate the relationship between meniscus magnetic resonance (MR) relaxation parameters and meniscus degradation through quantitative imaging of exvivo posterior horns of menisci from subjects with and without knee osteoarthritis (OA). We sampled medial and lateral menisci from ten medial compartment knee OA patients (mean age 63 years) undergoing total knee replacement and from ten deceased donors (references, mean age 51 years). MR relaxation parameters T2*, T2 and T1 of the posterior horn were measured at a 9.4T scanner. Comparisons were made between OA patients and references (with adjustment for age) as well as between medial and lateral menisci from the same knees. Mean values (standard deviation) of mean T2* were 13 (3.8), 6.9 (2.3), 7.2 (1.9) and 7.2 (1.7) ms for the medial and lateral patient menisci and the medial and lateral reference menisci, respectively. Corresponding values were 17 (3.7), 9.0 (2.2), 12 (4) and 9.0 (1.3) ms for T2 and 1810 (150), 1630 (30), 1580 (90) and 1560 (50) ms for T1. All three relaxation times were significantly longer in medial OA menisci compared to the other groups. Among medial reference menisci, relaxation times (mainly T1) tended to increase with age. MR relaxation times T2*, T2 and T1 in the posterior horn are longer in the medial menisci of patients with end-stage medial compartment knee OA compared to the corresponding lateral menisci and to reference menisci. The meniscus seems to undergo intrasubstance alterations related to both OA and ageing.

3D convolutional neural networks for detection and severity staging of meniscus and PFJ cartilage morphological degenerative changes in osteoarthritis and anterior cruciate ligament subjects.

Semiquantitative assessment of MRI plays a central role in musculoskeletal research; however, in the clinical setting MRI reports often tend to be subjective and qualitative. Grading schemes utilized in research are not used because they are extraordinarily time-consuming and unfeasible in clinical practice. To evaluate the ability of deep-learning models to detect and stage severity of meniscus and patellofemoral cartilage lesions in osteoarthritis and anterior cruciate ligament (ACL) subjects. Retrospective study aimed to evaluate a technical development. In all, 1478 MRI studies, including subjects at various stages of osteoarthritis and after ACL injury and reconstruction. 3T MRI, 3D FSE CUBE. Automatic segmentation of cartilage and meniscus using 2D U-Net, automatic detection, and severity staging of meniscus and cartilage lesion with a 3D convolutional neural network (3D-CNN). Receiver operating characteristic (ROC) curve, specificity and sensitivity, and class accuracy. Sensitivity of 89.81% and specificity of 81.98% for meniscus lesion detection and sensitivity of 80.0% and specificity of 80.27% for cartilage were achieved. The best performances for staging lesion severity were obtained by including demographics factors, achieving accuracies of 80.74%, 78.02%, and 75.00% for normal, small, and complex large lesions, respectively. In this study we provide a proof of concept of a fully automated deep-learning pipeline that can identify the presence of meniscal and patellar cartilage lesions. This pipeline has also shown potential in making more in-depth examinations of lesion subjects for multiclass prediction and severity staging. 2 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2019;49:400-410.

Composition of Cell Clusters in Torn Menisci and Their Extracellular Matrix Components.

Cell clusters, or groups of cells sharing a single chondron-like structure, are frequently found in degenerated areas of the osteoarthritic (OA) meniscus. However, little is known about these meniscal clusters in humans. The aim of our study was to determine the composition of the extracellular matrix deposition around cell clusters in human OA menisci. Twenty-six menisci were obtained through total knee arthroplasty from patients with OA knee joints. The specimens were subjected to safranin O staining and immunostaining for Sry-type HMG box 9 (SOX9), type II collagen, and aggrecan. Their signal density after staining was assessed using ImageJ software. Five regions of interest were analyzed within each tissue sample. The SOX9, type II collagen, and aggrecan densities were considerably higher in cluster areas than in intact superficial layers of the meniscus. In addition, a substantial difference was detected between cluster areas and degenerative areas without cell clusters. We demonstrated that cell clusters localized near fissures and clefts showed remarkable uniformity in menisci exposed to a broad range of injuries. In addition, the chondrogenic proteins SOX9, type II collagen, and aggrecan were highly expressed in these tissues.

A Switch of an Idea: Simultaneous High Tibial Osteotomy and Lateral Meniscal Allograft Transplantation

High tibial osteotomy (HTO) has been regarded as an effective treatment modality for isolated medial compartment knee osteoarthritis (OA) with varus deformity. However, management for relatively young active patients with both varus-aligned medial compartment knee OA and symptomatic irreparable lateral meniscus tear can be challenging. In this situation, correction of varus alignment by HTO and restoring the function of the lateral meniscus by meniscal allograft transplantation (MAT) can be a possible solution. We present the clinical result and technical considerations for a case of varus-aligned medial compartment OA combined with lateral meniscus tear treated by simultaneously performed medial open wedge HTO and lateral MAT.

Transcriptome comparison of meniscus from patients with and without osteoarthritis.

To assess the impact of osteoarthritis (OA) on the meniscus by comparing transcripts and biological processes in the meniscus between patients with and without OA. RNA microarrays were used to identify transcripts differentially expressed (DE) in meniscus obtained from 12 OA and 12 non-OA patients. The non-OA specimens were obtained at the time of arthroscopic partial meniscectomy. Real-time PCR was performed on selected transcripts. Biological processes and gene-networking was examined computationally. Transcriptome signatures were mapped with 37 OA-related transcripts to evaluate how meniscus gene expression relates to that of OA cartilage. We identified 168 transcripts significantly DE between OA (75 elevated, 93 repressed) and non-OA samples (≥1.5-fold). Among these, CSN1S1, COL10A1, WIF1, and SPARCL1 were the most prominent transcripts elevated in OA meniscus, POSTN and VEGFA were most highly repressed in OA meniscus. Transcripts elevated in OA meniscus represented response to external stimuli, cell migration and cell localization while those repressed in OA meniscus represented histone deacetylase activity (related to epigenetics) and skeletal development. Numerous long non-coding RNAs (lncRNAs) were DE between the two groups. When segregated by OA-related transcripts, two distinct clustering patterns appeared: OA meniscus appeared to be more inflammatory while non-OA meniscus exhibited a "repair" phenotype. Numerous transcripts with potential relevance to the pathogenesis of OA are DE in OA and non-OA meniscus. These data suggest an involvement of epigenetically regulated histone deacetylation in meniscus tears as well as expression of lncRNAs. Patient clustering based on transcripts related to OA in articular cartilage confirmed distinct phenotypes between injured (non-OA) and OA meniscus.

Viscoelastic properties of rabbit osteoarthritic menisci: A correlation with matrix alterations

The aim of this study was to evaluate the effect of early osteoarthritis (OA) on the viscoelastic properties of rabbit menisci and to correlate the mechanical alterations with the microstructural changes. Anterior Cruciate Ligament Transection (ACLT) was performed in six male New-Zealand White rabbits on the right knee joint. Six healthy rabbits served as controls. Menisci were removed six weeks after ACLT and were graded macroscopically. Indentation-relaxation tests were performed in the anterior and posterior regions of the medial menisci. The collagen fibre organization and glycosaminoglycan (GAG) content were assessed by biphotonic confocal microscopy and histology, respectively. OA menisci displayed severe macroscopic lesions compared with healthy menisci (p=0.009). Moreover, the instantaneous and equilibrium moduli, which were 2.9±1.0MPa and 0.60±0.18MPa in the anterior region of healthy menisci, respectively, decreased significantly (p=0.03 and p=0.004, respectively) in OA menisci by 55% and 57%, respectively, indicating a global decrease in meniscal stiffness in this region. The equilibrium modulus alone decreased significantly (p=0.04) in the posterior region, going from 0.60±0.18MPa to 0.26±012MPa. This induced a loss of tissue elasticity. These mechanical changes were associated in the posterior region with a structural disruption of the superficial layers, from which the tie fibres emanate, and with a decrease in the GAG content in the anterior region. Consequently, the circumferential collagen fibres of the deep zone were dissociated and the collagen bundles were less compact. Our results demonstrate the strong meniscal modifications induced by ACLT at an early stage of OA and highlight the relationship between structural and chemical matrix alterations and mechanical properties.

Reduced response of human meniscal cells to Osteogenic Protein 1 during osteoarthritis and pro-inflammatory stimulation

Many cell types lose responsiveness to anabolic factors during inflammation and disease. Osteogenic Protein 1 (OP1/BMP7) was evaluated for the ability to enhance extracellular matrix synthesis in healthy and OA meniscus cells. Mechanisms of cell response to OP1 were explored. Meniscus and cartilage tissues from healthy tissue donors and osteoarthritis (OA) patients undergoing total knee arthroplasties were acquired. Primary cell cultures were stimulated with OP1 and/or inflammatory factors (IL1α, IL1β, or fibronectin fragments (FnF)) and cellular responses were analyzed by RT-qPCR and immunoblots. Frozen section immunohistochemistry (IHC) was conducted to assess OP1 and receptor proteins in normal and OA meniscus. OP1 treatment of normal meniscus cells resulted in significant, dose-dependent increases in ACAN (aggrecan) and COL2A1, and decreased MMP13 gene transcription, while only ACAN was upregulated (P<0.01) at the highest dose of OP1 in OA meniscus cells. OP1 induced significantly more ACAN gene transcription in normal meniscus than normal articular cartilage (P=0.05), and no differences between normal and OA cartilage were detected. Receptor expression and kinetics of canonical signaling activation were similar between normal and OA specimens. Normal meniscus cells treated with inflammatory factors were refractory to OP1 stimulation. Smad1 phosphorylation at an inhibitory site was induced (P=0.01 for both normal and OA meniscus) by inflammatory cytokine treatment. The meniscus demonstrates resistance to OP1 stimulation in OA and in the presence of inflammatory mediators. MAPK-mediated Smad1 linker phosphorylation is a possible mediator of the loss of anabolic extracellular matrix production in the inflammatory cytokine affected meniscus.

EXPRESSION OF COLLAGEN TYPE I IN UNALTERED AND OSTEOARTHRITIC MENISCI OF KNEE JOINT.

Knee osteoarthritis is a progressive degenerative disease which affects meniscal tissue. The aim of this study was to determine the differences in collagen type I expression in macroscopically unaltered and osteoarthritic menisci, and correlate the expression with the grade of macroscopic damage, age and body mass index of patients, preoperative condition of anterior cruciate ligament, angulation and knee contracture. The control group consisted of 10 macroscopically unaltered menisci, while the experimental group had 35 osteoarthritic menisci. Besides macroscopic grading of meniscal damage, the analysis of collagen type I expression was determined by immunohistochemical staining with the corresponding antibody using semiquantitative scale scores and quantitative parameters: intensity of expression and stained area size. The results of semiquantitative evaluation showed a statistically significant decrease in collagen type I expression in osteoarthritic menisci, which correlated with an increase in macroscopic damage grade. The results of quantitative evaluation did not show a statistically significant decrease in the expression. In posterior meniscal horns, a more intense collagen type I expression was seen in the women, as well as a positive correlation of quantitatively evaluated expression with body mass index. Collagen type I expression in the anterior horns was significantly lower in varus alignment. In the semiquantitative evaluation, collagen type I expression in osteoarthritic menisci was significantly lower compared to macroscopically unchanged menisci. The decrease in the expression level correlates with the increase in the grade of macroscopic meniscal damage. There was no statistically significant difference in the quantitative evaluation of expression.

Meniscal degeneration in human knee osteoarthritis: in situ hybridization and immunohistochemistry study.

Meniscus injury is one of the causes of secondary osteoarthritis (OA). However, the role of meniscus is still unclear. Human meniscal distribution of cells and cartilage oligomeric matrix protein (COMP) and their changes in advanced OA were analyzed. Thirty-one medial menisci from patients with knee OA that underwent a total knee arthroplasty were studied. Normal meniscal tissue was obtained from partial arthroscopic meniscectomy. Meniscal samples were processed for histology, immunohistochemistry and in situ hybridization, for cell assessment including density, active divisions, apoptosis, COMP distribution and proteoglycan content. Osteoarthritic menisci demonstrated areas of cell depletion and significant decrease in COMP immunostaining. Actively dividing cells were only found in the meniscectomy group, but not in the osteoarthritic group. Proteoglycan staining was less prominent in menisci from the osteoarthritis group. Our results show a decreased cell population, with low COMP and altered matrix organization in osteoarthritis menisci that suggest an altered meniscal scaffold and potential impairment of meniscal function. These meniscal changes may be associated with the development of knee osteoarthritis.

Osteoarthritic changes in vervet monkey knees correlate with meniscus degradation and increased matrix metalloproteinase and cytokine secretion

Meniscus injury increases osteoarthritis risk but its pathobiology in osteoarthritis is unclear. We hypothesized that older adult vervet monkeys would exhibit knee osteoarthritic changes and the degenerative menisci from these animals would secrete matrix metalloproteinases (MMPs) and pro-inflammatory cytokines that contribute to the development of osteoarthritis. In a cross sectional analysis of healthy young adult (9-12 years) and old (19-26 years) adult female vervet monkeys, knees were evaluated in vivo with computed tomography (CT) imaging, and joint tissues were morphologically graded at necropsy. Meniscus explants were subsequently cultured to evaluate meniscal MMP and cytokine secretion. CT images revealed significant bony osteoarthritic changes in 80% of older monkeys which included increases in osteophyte number and meniscal calcification. Meniscus and cartilage degradation scores were greater in the older monkeys and were positively correlated (r > 0.7). Menisci from older animals exhibiting osteoarthritic changes secreted significantly more MMP-1, MMP-3, and MMP-8 than healthy menisci from younger monkeys. Older menisci without significant osteoarthritic changes secreted more IL-7 than healthy young menisci while older osteoarthritic menisci secreted more IL-7 and granulocyte-macrophage colony-stimulating factor than healthy older menisci. Aged vervets develop naturally occurring knee osteoarthritis that includes involvement of the meniscus. Degenerative menisci secreted markedly increased amounts of matrix-degrading enzymes and inflammatory cytokines. These factors would be expected to act on the meniscus tissue and local joint tissues and may ultimately promote osteoarthritis development. These finding also suggest vervet monkeys are a useful animal model for studying the progression of osteoarthritis.

Heparin-binding epidermal growth factor-like growth factor (HB-EGF) is increased in osteoarthritis and regulates chondrocyte catabolic and anabolic activities

We determined if the epidermal growth factor receptor ligand HB-EGF is produced in cartilage and if it regulates chondrocyte anabolic or catabolic activity. HB-EGF expression was measured by quantitative PCR using RNA isolated from mouse knee joint tissues and from normal and osteoarthritis (OA) human chondrocytes. Immunohistochemistry was performed on normal and OA human cartilage and meniscus sections. Cultured chondrocytes were treated with fibronectin fragments (FN-f) as a catabolic stimulus and osteogenic protein 1 (OP-1) as an anabolic stimulus. Effects of HB-EGF on cell signaling were analyzed by immunoblotting of selected signaling proteins. MMP-13 was measured in conditioned media, proteoglycan synthesis was measured by sulfate incorporation, and matrix gene expression by quantitative PCR. HB-EGF expression was increased in 12-month old mice at 8 weeks after surgery to induce OA and increased amounts of HB-EGF were noted in human articular cartilage from OA knees. FN-f stimulated chondrocyte HB-EGF expression and HB-EGF stimulated chondrocyte MMP-13 production. However, HB-EGF was not required for FN-f stimulation of MMP-13 production. HB-EGF activated the ERK and p38 MAP kinases and stimulated phosphorylation of Smad1 at an inhibitory serine site which was associated with inhibition of OP-1 mediated proteoglycan synthesis and reduced aggrecan (ACAN) but not COL2A1 expression. HB-EGF is a new factor identified in OA cartilage that promotes chondrocyte catabolic activity while inhibiting anabolic activity suggesting it could contribute to the catabolic-anabolic imbalance seen in OA cartilage.

Melatonin‐mediated suppression of early peripheral sensitization in osteoarthritic meniscus

Joint pain is classified as a major symptom in most of osteoarthritic (OA) cases. Most common management for OA is to alleviate symptoms through administration with conventional analgesic drugs, but patients continued to experience pain. Therefore, the present study is aimed at determining the effects of melatonin on peripheral nociceptive processing in animals with collagenase‐induced cartilage damage. Melatonin (10 mg/kg) was injected twice daily subcutaneously. There was TrkB upregulation as well as increase of non‐glycosylated NK‐1R despite no difference of its glycosylation in OA meniscus, but melatonin blocked it. To study the effect of melatonin on cells exposed to inflammatory neuropeptides, primary cultured chondrocytes were treated with both TNF‐α and rCGRP. Increase of Bax/Bcl‐2 ratio is accompanied by reduction of cell viability, and there were a loss of type II collagen, increase of active MMP‐13, and nuclear Ca2+ deposition. But melatonin at the nanomolar concentration rescued from damage responses. These molecular results might indicate early anti‐nociceptive effect of melatonin, but behavior of the animals was deemed hypersensitive to innocuous mechanical stimuli. Further experiments are needed to elucidate their inconsistency.Funding: 2012R1A1A2005089, 2013R1A2A2A01067169, KGM4611512