Proteoglycan 4 downregulation in a sheep meniscectomy model of early osteoarthritis

Osteoarthritis is a disease of multifactorial aetiology characterised by progressive breakdown of articular cartilage. In the early stages of the disease, changes become apparent in the superficial zone of articular cartilage, including fibrillation and fissuring. Normally, a monolayer of lubricating molecules is adsorbed on the surface of cartilage and contributes to the minimal friction and wear properties of synovial joints. Proteoglycan 4 is the lubricating glycoprotein believed to be primarily responsible for this boundary lubrication. Here we have used an established ovine meniscectomy model of osteoarthritis, in which typical degenerative changes are observed in the operated knee joints at three months after surgery, to evaluate alterations in proteoglycan 4 expression and localisation in the early phases of the disease. In normal control joints, proteoglycan 4 was immunolocalised in the superficial zone of cartilage, particularly in those regions of the knee joint covered by a meniscus. After the onset of early osteoarthritis, we demonstrated a loss of cellular proteoglycan 4 immunostaining in degenerative articular cartilage, accompanied by a significant (p < 0.01) decrease in corresponding mRNA levels. Early loss of proteoglycan 4 from the cartilage surface in association with a decrease in its expression by superficial-zone chondrocytes might have a role in the pathogenesis of osteoarthritis.     

The meniscus,calcification and osteoarthritis: a pathologic team

Articular calcification correlates with osteoarthritis (OA) severity but its exact role in the disease process is unclear. In examining OA meniscal cell function, Sun and colleagues have shown recently that meniscal cells from end-stage OA subjects can generate calcium crystals and that genes involved in calcification are upregulated in OA meniscal cells. Also, this in vitro calcium deposition by OA menisci is inhibited by phosphocitrate. This study should catalyse further work examining the pathological contribution or otherwise of calcium crystals in OA. This would significantly aid the development of potential disease modifying agents in OA, which are currently unavailable.     

Rigid-body modeling of knee cartilage and meniscus using experimental pressure-strain curves

Rigid-body knee models have gained popularity thanks to computational speed and ease of setup compared to finite element models—showing exciting potential for clinical patient-specific models in the future. However, Rigid-body studies in general have encountered difficulty in modeling cartilage and especially meniscus material properties, often relying on computationally costly optimization techniques. This paper presents two new methods to alleviate the difficulty—one to define model contact pressure and one to define meniscus internal forces—and is the first to our knowledge to use experimental pressure-strain curves from the literature to simulate cartilage and meniscus behavior in a rigid body model. This paper describes the methodology to derive the proof of concept model and preliminary results from a gait simulation based on ISO 14243-1.     

Oestrogen is important for maintenance of cartilage and subchondral bone in a murine model of knee osteoarthritis

Introduction  

Oestrogen depletion may influence onset and/or progression of osteoarthritis. We investigated in an ovariectomized mouse model the impact of oestrogen loss and oestrogen supplementation on articular cartilage and subchondral bone in tibia and patella, and assessed bone changes in osteoarthritis development.     

Inflammatory molecules produced by meniscus and synovium in early and end-stage osteoarthritis: a coculture study

The aim of this study was to identify the molecules and pathways involved in the cross-talk between meniscus and synovium that may play a critical role in osteoarthritis (OA) pathophysiology. Samples of synovium and meniscus were collected from patients with early and end-stage OA and cultured alone or cocultured. Cytokines, chemokines, metalloproteases, and their inhibitors were evaluated at the gene and protein levels. The extracellular matrix (ECM) changes were also investigated. In early OA cultures, higher levels of interleukin-6 (IL-6) and IL-8 messenger RNA were expressed by synovium and meniscus in coculture compared with meniscus cultured alone. RANTES release was significantly increased when the two tissues were cocultured compared with meniscus cultured alone. Increased levels of matrix metalloproteinase-3 (MMP-3) and MMP-10 proteins, as well as increased release of glycosaminoglycans and aggrecan CS846 epitope, were observed when synovium was cocultured with meniscus. In end-stage OA cultures, increased levels of IL-8 and monocyte chemoattractant protein-1 (MCP-1) proteins were released in cocultures compared with cultures of meniscus alone. Chemokine (C-C motif) ligand 21 (CCL21) protein release was higher in meniscus cultured alone and in coculture compared with synovium cultured alone. Increased levels of MMP-3 and 10 proteins were observed when tissues were cocultured compared with meniscus cultured alone. Aggrecan CS846 epitope release was increased in cocultures compared with cultures of either tissue cultured alone. Our study showed the production of inflammatory molecules by synovium and meniscus which could trigger inflammatory signals in early OA patients, and induce ECM loss in the progressive and final stages of OA pathology.     

Acute changes in knee cartilage transverse relaxation time after running and bicycling

PurposeTo compare the acute effect of running and bicycling of an equivalent cumulative load on knee cartilage composition and morphometry in healthy young men. A secondary analysis investigated the relationship between activity history and the change in cartilage composition after activity.MethodsIn fifteen men (25.8±4.2 years), the vertical ground reaction force was measured to determine the cumulative load exposure of a 15-min run. The vertical pedal reaction force was recorded during bicycling to define the bicycling duration of an equivalent cumulative load. On separate visits that were spaced on average 17 days apart, participants completed these running and bicycling bouts. Mean cartilage transverse relaxation times (T₂) were determined for cartilage on the tibia and weight-bearing femur before and after each exercise. T₂ was measured using a multi-echo spin-echo sequence and 3T MRI. Cartilage of the weight bearing femur and tibia was segmented using a highly-automated segmentation algorithm. Activity history was captured using the International Physical Activity Questionnaire.ResultsThe response of T₂ to bicycling and running was different (p=0.019; mean T₂: pre-running=34.27 ms, pre-bicycling=32.93 ms, post-running=31.82 ms, post-bicycling=32.36 ms). While bicycling produced no change (−1.7%, p=0.300), running shortened T₂ (−7.1%, p<0.001). Greater activity history predicted smaller changes in tibial, but not femoral, T₂.ConclusionsChanges in knee cartilage vary based on activity type, independent of total load exposure, in healthy young men. Smaller changes in T₂ were observed after bicycling relative to running. Activity history was inversely related to tibial T₂, suggesting cartilage conditioning.     

Finite element simulations of a focal knee resurfacing implant applied to localized cartilage defects in a sheep model

Articular resurfacing metal implants have recently been tested in animal models to treat full thickness localized articular cartilage defects, showing promising results. However, the mechanical behavior of cartilage surrounding the metal implant has not been studied yet as it is technically challenging to measure in vivo contact areas, pressures, stresses and deformations from the metal implant. Therefore, we implemented a detailed numerical finite element model by approximating one of the condyles of the sheep tibiofemoral joint and created a defect of specific size to accommodate the implant. Using this model, the mechanical behavior of the surrounding of metal implant was studied. The model showed that the metal implant plays a significant role in the force transmission. Two types of profiles were investigated for metal implant. An implant with a double-curved profile, i.e., a profile fully congruent with the articular surfaces in the knee, gives lower contact pressures and stresses at the rim of the defect than the implant with unicurved spherical profile. The implant should be placed at a certain distance into the cartilage to avoid damage to opposing biological surface. Too deep positions, however, lead to high shear stresses in the cartilage edges around the implant. Mechanical sealing was achieved with a wedge shape of the implant, also useful for biochemical sealing of cartilage edges at the defect.     

Articular cartilage and changes in Arthritis: Cell biology of osteoarthritis

The reaction patterns of chondrocytes in osteoarthritis can be summarized in five categories: (1) proliferation and cell death (apoptosis); changes in (2) synthetic activity and (3) degradation; (4) phenotypic modulation of the articular chondrocytes; and (5) formation of osteophytes. In osteoarthritis, the primary responses are reinitiation of synthesis of cartilage macromolecules, the initiation of synthesis of types IIA and III procollagens as markers of a more primitive phenotype, and synthesis of active proteolytic enzymes. Reversion to a fibroblast-like phenotype, known as 'dedifferentiation', does not appear to be an important component. Proliferation plays a role in forming characteristic chondrocyte clusters near the surface, while apoptosis probably occurs primarily in the calcified cartilage.     

Semiquantitative analysis of ECM molecules in the different cartilage layers in early and advanced osteoarthritis of the knee joint

The study was conducted to examine the expression of collagen type I and II in the different cartilage layers in relation to other ECM molecules during the progression of early osteoarthritic degeneration in human articular cartilage (AC). Quantitative real-time (RT)-PCR and colorimetrical techniques were used for calibration of Photoshop-based image analysis in detecting such lesions. Immunohistochemistry and histology were performed with 40 cartilage tissue samples showing mild (ICRS grade 1b) respectively moderate/advanced (ICRS grade 3a or 3b) (20 each) osteoarthritis compared with 15 healthy biopsies. Furthermore, we quantified our results on the gene expression of collagen type I and II and aggrecan with the help of real-time (RT)-PCR. Proteoglycan content was measured colorimetrically. The digitized images of histology and immunohistochemistry stains were analyzed with Photoshop software. T-test and Spearman correlation analysis were used for statistical analysis. In the earliest stages of AC deterioration the loss of collagen type II was associated with the appearance of collagen type I, shown by increasing amounts of collagen type I mRNA. During subsequent stages, a progressive loss of structural integrity was associated with increasing deposition of collagen type I as part of a natural healing response. A decrease of collagen type II is visible especially in the upper fibrillated area of the advanced osteoarthritic samples, which then leads to an overall decrease. Analysis of proteoglycan showed losses of the overall content and a loss of the classical zonal formation. Correlation analysis of the proteoglycan Photoshop measurements with the RT-PCR revealed strong correlation for Safranin O and collagen type I, medium for collagen type II, alcian blue and glycoprotein but weak correlation with PCR aggrecan results. Photoshop based image analysis might become a valuable supplement for well known histopathological grading systems of lesioned articular cartilage. The evidence of collagen type I production early in the OA disease process coupled with the ability of chondrocytes to up-regulate collagen type II production suggests that therapeutic agents that suppress collagen type I production and increase collagen type II production may enable chondrocytes to generate a more effective repair response.     

Bone and cartilage characteristics in postmenopausal women with mild knee radiographic osteoarthritis and those without radiographic osteoarthritis

Objectives:

To evaluate the association between radiographically-assessed knee osteoarthritis and femoral neck bone characteristics in women with mild knee radiographic osteoarthritis and those without radiographic osteoarthritis.

Methods:

Ninety postmenopausal women (mean age [SD], 58 [4] years; height, 163 [6] cm; weight, 71 [11] kg) participated in this cross-sectional study. The severity of radiographic knee osteoarthritis was defined using Kellgren-Lawrence grades 0=normal (n=12), 1=doubtful (n=25) or 2=minimal (n=53). Femoral neck bone mineral content (BMC), section modulus (Z), and cross-sectional area (CSA) were measured with DXA. The biochemical composition of ipsilateral knee cartilage was estimated using quantitative MRI measures, T2 mapping and dGEMRIC. The associations between radiographic knee osteoarthritis grades and bone and cartilage characteristics were analyzed using generalized linear models.

Results:

Age-, height-, and weight-adjusted femoral neck BMC (p for linearity=0.019), Z (p for linearity=0.033), and CSA (p for linearity=0.019) increased significantly with higher knee osteoarthritis grades. There was no linear relationship between osteoarthritis grades and knee cartilage indices.

Conclusions:

Increased DXA assessed hip bone strength is related to knee osteoarthritis severity. These results are hypothesis driven that there is an inverse relationship between osteoarthritis and osteoporosis. However, MRI assessed measures of cartilage do not discriminate mild radiographic osteoarthritis severity.     

Relationships between biomarkers of cartilage, bone, synovial metabolism and knee pain provide insights into the origins of pain in early knee osteoarthritis

Introduction

We tested the hypothesis that there exist relationships between the onset of early stage radiographically defined knee osteoarthritis (OA), pain and changes in biomarkers of joint metabolism.

Methods

Using Kellgren-Lawrence (K/L) grading early radiographic knee OA (K/L 2) was detected in 16 of 46 patients. These grades (K/L 1 is no OA and K/L 2 is early OA) were divided into two groups according to the presence or absence of persistent knee pain. Sera (s) and urines (u) were analysed with biomarkers for cartilage collagen cleavage (sC2C and uCTX-II) and synthesis (sCPII), bone resorption (uNTx) and synovitis (hyaluronic acid: sHA).

Results

sCPII decreased and sC2C/sCPII, uCTX-II/sCPII and sHA increased with onset of OA (K/L 2 versus K/L 1) irrespective of joint pain. In contrast, sC2C and uCTX-II remained unchanged in early OA patients. Of the patients with K/L grades 1 and 2 sC2C, sCPII, sHA, uNTX and uCTX-II were all significantly increased in patients with knee pain independent of grade. Among the K/L grade 2 subjects, only uCTX-II and uCTX-II/sCPII were increased in those with knee pain. In grade 1 patients both sC2C and sCPII were increased in those with knee pain. No such grade specific changes were seen for the other biomarkers including sHA.

Conclusions

These results suggest that changes in cartilage matrix turnover detected by molecular biomarkers may reflect early changes in cartilage structure that account directly or indirectly for knee pain. Also K/L grade 1 patients with knee pain exhibit biomarker features of early OA.     

Lack of association between acupoint sensitization and microcirculatory structural changes in a mouse model of knee osteoarthritis: A pilot study

As a stimulating point in acupuncture, acupoint has unique microcirculatory features, and its dynamics vary greatly depending on health status. Acupoint sensitization is defined as the transformation of an acupoint from a “silenced status” (healthy) to an “activated status” (disease). Our previous study demonstrated that acupoint sensitization is associated with an increase in the level of local blood perfusion. However, the structural changes in microcirculation during acupoint sensitization have yet to be elucidated because the high‐resolution microcirculation imaging of acupoints has been difficult to obtain. In this study, the structural changes in microcirculation at the Zusanli (ST36), Yanglingquan (GB34) and nonacupoint sites on days 0, 7 and 21 were dynamically observed during acupoint sensitization in an experimental knee osteoarthritis mouse model by using optical‐resolution photoacoustic microscopy. The results showed that no significant differences in microvessel density, the distribution of vessel diameters or vascular tortuosity were observed at the GB34, ST36 or nonacupoint sites among days 0, 7 and 21. We proposed that acupoint sensitization may not be associated with the structural changes in microcirculation and that the microcirculatory changes during acupoint sensitization are more likely to be functional. The functional characteristics of the sensitized acupoints warrant further investigation.      

Effect of eldecalcitol on articular cartilage through the regulation of transcription factor Erg in a murine model of knee osteoarthritis

Clinical studies have reported an association between low blood levels of 25-hydroxyvitamin D and the progression of osteoarthritis (OA), but the mechanism and effects of vitamin D signaling on articular chondrocytes and cartilage remains unclear. The purpose of this study was to investigate the effects of vitamin D on articular cartilage degeneration using eldecalcitol (ED-71), which is an active vitamin D₃ analog. Eight-week old male C57BL/6NCrSlc mice were subjected to experimental surgery to induce OA and local treatments with 10 μL ED-71 (0.5 μg/mL) were administered weekly. Four and 12 weeks after surgery, joints were evaluated using histological scoring systems. In addition, gene expression was analyzed in chondrocytes that were isolated from wildtype neonatal mice, cultured, and treated with ED-71 (10^?8 M). Joints treated with ED-71 demonstrated slowed progression of OA at 4 weeks after surgery, but few effects were observed at 12 weeks after surgery. Ets-related gene (Erg) expression was upregulated in OA articular cartilage, and further increased by ED-71 treatment. In primary chondrocytes cultured with ED-71, the gene expression of Erg and lubricin/proteoglycan 4 significantly increased, as compared to that of cells cultured without ED-71. Local treatment with ED-71 reduced degenerative changes to the articular cartilage during the early phase of experimental OA. Regulation of Erg by ED-71 in articular cartilage could confer resistance to early osteoarthritic changes.     

The pregnant sheep as a model for human pregnancy

Successful outcome of human pregnancy not only impacts the quality of infant life and well-being, but considerable evidence now suggests that what happens during fetal development may well impact health and well-being into adulthood. Consequently, a thorough understanding of the developmental events that occur between conception and delivery is needed. For obvious ethical reasons, many of the questions remaining about the progression of human pregnancy cannot be answered directly, necessitating the use of appropriate animal models. A variety of animal models exist for the study of both normal and compromised pregnancies, including laboratory rodents, non-human primates and domestic ruminants. While all of these animal models have merit, most suffer from the inability to repetitively sample from both the maternal and fetal side of the placenta, limiting their usefulness in the study of placental or fetal physiology under non-stressed in vivo conditions. No animal model truly recapitulates human pregnancy, yet the pregnant sheep has been used extensively to investigate maternal-fetal interactions. This is due in part to the ability to surgically place and maintain catheters in both the maternal and fetal vasculature, allowing repeated sampling from non-anesthetized pregnancies. Considerable insight has been gained on placental oxygen and nutrient transfer and utilization from use of pregnant sheep. These findings were often confirmed in human pregnancies once appropriate technologies became available. The purpose of this review is to provide an overview of human and sheep pregnancy, with emphasis placed on placental development and function as an organ of nutrient transfer.     

Biomechanics of knee ligaments: injury, healing, and repair

Knee ligament injuries are common, particularly in sports and sports related activities. Rupture of these ligaments upsets the balance between knee mobility and stability, resulting in abnormal knee kinematics and damage to other tissues in and around the joint that lead to morbidity and pain. During the past three decades, significant advances have been made in characterizing the biomechanical and biochemical properties of knee ligaments as an individual component as well as their contribution to joint function. Further, significant knowledge on the healing process and replacement of ligaments after rupture have helped to evaluate the effectiveness of various treatment procedures. This review paper provides an overview of the current biological and biomechanical knowledge on normal knee ligaments, as well as ligament healing and reconstruction following injury. Further, it deals with new and exciting functional tissue engineering approaches (ex. growth factors, gene transfer and gene therapy, cell therapy, mechanical factors, and the use of scaffolding materials) aimed at improving the healing of ligaments as well as the interface between a replacement graft and bone. In addition, it explores the anatomical, biological and functional perspectives of current reconstruction procedures. Through the utilization of robotics technology and computational modeling, there is a better understanding of the kinematics of the knee and the in situ forces in knee ligaments and replacement grafts. The research summarized here is multidisciplinary and cutting edge that will ultimately help improve the treatment of ligament injuries. The material presented should serve as an inspiration to future investigators.     

Procyanidin B3 prevents articular cartilage degeneration and heterotopic cartilage formation in a mouse surgical osteoarthritis model

Osteoarthritis (OA) is a common disease in the elderly due to an imbalance in cartilage degradation and synthesis. Heterotopic ossification (HO) occurs when ectopic masses of endochondral bone form within the soft tissues around the joints and is triggered by inflammation of the soft tissues. Procyanidin B3 (B3) is a procyanidin dimer that is widely studied due to its high abundance in the human diet and antioxidant activity. Here, we evaluated the role of B3 isolated from grape seeds in the maintenance of chondrocytes in vitro and in vivo. We observed that B3 inhibited H(2)O(2)-induced apoptosis in primary chondrocytes, suppressed H(2)O(2)- or IL-1?-induced nitric oxide synthase (iNOS) production, and prevented IL-1?-induced suppression of chondrocyte differentiation marker gene expression in primary chondrocytes. Moreover, B3 treatment enhanced the early differentiation of ATDC5 cells. To examine whether B3 prevents cartilage destruction in vivo, OA was surgically induced in C57BL/6J mice followed by oral administration of B3 or vehicle control. Daily oral B3 administration protected articular cartilage from OA and prevented chondrocyte apoptosis in surgically-induced OA joints. Furthermore, B3 administration prevented heterotopic cartilage formation near the surgical region. iNOS protein expression was enhanced in the synovial tissues and the pseudocapsule around the surgical region in OA mice fed a control diet, but was reduced in mice that received B3. Together, these data indicated that in the OA model, B3 prevented OA progression and heterotopic cartilage formation, at least in a part through the suppression of iNOS. These results support the potential therapeutic benefits of B3 for treatment of human OA and heterotopic ossification.