Osteoarthritis

Regeneration of the articular surface of the rabbit synovial joint by cell homing: a proof of concept study

BACKGROUND

A common approach for tissue regeneration is cell delivery, for example by direct transplantation of stem or progenitor cells. An alternative, by recruitment of endogenous cells, needs experimental evidence. We tested the hypothesis that the articular surface of the synovial joint can regenerate with a biological cue spatially embedded in an anatomically correct bioscaffold.

METHODS

In this proof of concept study, the surface morphology of a rabbit proximal humeral joint was captured with laser scanning and reconstructed by computer-aided design. We fabricated an anatomically correct bioscaffold using a composite of poly-epsilon-caprolactone and hydroxyapatite. The entire articular surface of unilateral proximal humeral condyles of skeletally mature rabbits was surgically excised and replaced with bioscaffolds spatially infused with transforming growth factor beta3 (TGFbeta3)-adsorbed or TGFbeta3-free collagen hydrogel. Locomotion and weightbearing were assessed 1-2, 3-4, and 5-8 weeks after surgery. At 4 months, regenerated cartilage samples were retrieved from in vivo and assessed for surface fissure, thickness, density, chondrocyte numbers, collagen type II and aggrecan, and mechanical properties.

FINDINGS

Ten rabbits received TGFbeta3-infused bioscaffolds, ten received TGFbeta3-free bioscaffolds, and three rabbits underwent humeral-head excision without bioscaffold replacement. All animals in the TGFbeta3-delivery group fully resumed weightbearing and locomotion 3-4 weeks after surgery, more consistently than those in the TGFbeta3-free group. Defect-only rabbits limped at all times. 4 months after surgery, TGFbeta3-infused bioscaffolds were fully covered with hyaline cartilage in the articular surface. TGFbeta3-free bioscaffolds had only isolated cartilage formation, and no cartilage formation occurred in defect-only rabbits. TGFbeta3 delivery yielded uniformly distributed chondrocytes in a matrix with collagen type II and aggrecan and had significantly greater thickness (p=0.044) and density (p<0.0001) than did cartilage formed without TGFbeta3. Compressive and shear properties of TGFbeta3-mediated articular cartilage did not differ from those of native articular cartilage, and were significantly greater than those of cartilage formed without TGFbeta3. Regenerated cartilage was avascular and integrated with regenerated subchondral bone that had well defined blood vessels. TGFbeta3 delivery recruited roughly 130% more cells in the regenerated articular cartilage than did spontaneous cell migration without TGFbeta3.

INTERPRETATION

Our findings suggest that the entire articular surface of the synovial joint can regenerate without cell transplantation. Regeneration of complex tissues is probable by homing of endogenous cells, as exemplified by stratified avascular cartilage and vascularised bone. Whether cell homing acts as an adjunctive or alternative approach of cell delivery for regeneration of tissues with different organisational complexity warrants further investigation.

FUNDING

New York State Stem Cell Science; US National Institutes of Health.

Analysis of early changes in the articular cartilage transcriptisome in the rat meniscal tear model of osteoarthritis: pathway comparisons with the rat anterior cruciate transection model and with human osteoarthritic cartilage

OBJECTIVE

The purpose of this study was to use microarray technology to: (1) understand the early molecular events underlying the damage of articular cartilage initiated by this surgical procedure, and (2) determine whether these changes mimic those that are occurring in human osteoarthritic (OA) cartilage.

DESIGN

Cartilage was harvested from both medial and lateral sides of the tibial plateaus and femoral condyles of both meniscal tear (MT) and sham surgery groups on days 3, 7 and 21 post-surgery. mRNA prepared from these rat cartilage samples was used for microarray analysis.

RESULTS

Statistical analysis identified 475 genes that were differentially expressed between the sham and MT groups, at one or more of the time points that were analyzed. By integrating these genes with OA-related genes reported previously in a rat OA model and in human OA array studies, we identified 20 commonly changed genes. Six out of these 20 genes (Col5A1, Col6A2, INHBA, LTBP2, NBL1 and SERPINA1) were differentially expressed in two animal models and in human OA. Pathway analysis identified some key features of OA pathology, namely cartilage extracellular matrix remodeling, angiogenesis, and chondrocyte cell death that were recapitulated in the animal models. The rat models suggested increased inflammation and cholesterol metabolic pathways may play important role in early cartilage degeneration.

CONCLUSION

We identified a large number of differentially expressed genes in the articular cartilage of the MT model. While there was lack of overall identity in cartilage gene expression between the rat models and human OA, several key biological processes were recapitulated in the rat MT OA model.

Knee pain and mobility impairments: meniscal and articular cartilage lesions

The Orthopaedic Section of the American Physical Therapy Association presents this fifth set of clinical practice guidelines on knee pain and mobility impairments, linked to the International Classification of Functioning, Disability, and Health (ICF). The purpose of these practice guidelines is to describe evidence-based orthopaedic physical therapy clinical practice and provide recommendations for (1) examination and diagnostic classification based on body functions and body structures, activity limitations, and participation restrictions, (2) interventions provided by physical therapists, (3) and assessment of outcome for common musculoskeletal disorders.

Matrix metalloproteinase-3 in articular cartilage is upregulated by joint immobilization and suppressed by passive joint motion

Both underloading and overloading of joints can lead to articular cartilage degradation, a process mediated in part by matrix metalloproteinases (MMPs). Here we examine the effects of reduced loading of rat hindlimbs on articular cartilage expression of MMP-3, which not only digests matrix components but also activates other proteolytic enzymes. We show that hindlimb immobilization resulted in elevated MMP-3 mRNA expression at 6h that was sustained throughout the 21day immobilization period. MMP-3 upregulation was higher in the medial condyle than the lateral, and was greatest in the superficial cartilage zone, followed by middle and deep zones. These areas also showed decreases in safranin O staining, consistent with reduced cartilage proteoglycan content, as early as 7days after immobilization. One hour of daily moderate mechanical loading, applied as passive joint motion, reduced the MMP-3 and ADAMTS-5 increases that resulted from immobilization, and also prevented changes in safranin O staining. Intra-articular injections of an MMP-3 inhibitor, N-isobutyl-N-(4-methoxyphenylsulfonyl)-glycylhydroxamic acid (NNGH), dampened the catabolic effects of a 7day immobilization period, indicating a likely requirement for MMP-3 in the regulation of proteoglycan levels through ADAMTS-5. These results suggest that biomechanical forces have the potential to combat cartilage destruction and can be critical in developing effective therapeutic strategies.

2-D finite difference time domain model of ultrasound reflection from normal and osteoarthritic human articular cartilage surface

Quantitative high-frequency ultrasonic evaluation of articular cartilage has shown a potential for the diagnosis of osteoarthritis, where the roughness of the surface, collagen and proteoglycan contents, and the density and mechanical properties of cartilage change concurrently. Experimentally, these factors are difficult to investigate individually and thus a numerical model is needed. The present study is the first one to use finite difference time domain modeling of pulse-echo measurements of articular cartilage. Ultrasound reflection from the surface was investigated with varying surface roughness, material parameters (Young's modulus, density, longitudinal, and transversal velocities) and inclination of the samples. The 2-D simulation results were compared with the results from experimental measurements of the same samples in an identical geometry. Both the roughness and the material parameters contributed significantly to the ultrasound reflection. The angular dependence of the ultrasound reflection was strong for a smooth cartilage surface but disappeared for the samples with a rougher surface. These results support the findings of previous experimental studies and indicate that ultrasound detects changes in the cartilage that are characteristic of osteoarthritis. In the present study there are differences between the results of the simulations and the experimental measurements. However, the systematic patterns in the experimental behavior are correctly reproduced by the model. In the future, our goal is to develop more realistic acoustic models incorporating inhomogeneity and anisotropy of the cartilage.

Nanog maintains human chondrocyte phenotype and function in vitro

Previous work showed that Nanog, a homeobox family transcription factor, maintains embryonic stem cell pluripotency, suggesting that it has a role in stabilizing cell phenotype. Human chondrocytes lose their phenotype and dedifferentiate after relatively few passages in culture, changes that may limit their value in restoring damaged articular cartilage. We hypothesized that Nanog could stabilize the phenotype of cultured human chondrocytes in long-term monolayer cultures. To test this hypothesis, the human Nanog gene was stably transduced into human chondrocytes using a retroviral vector. Chondrocyte-specific gene expression (collagen type II, aggrecan, cartilage link protein, and Sox9) was measured by reverse transcription-polymerase chain reaction (RT-PCR) and real-time PCR in monolayer cultured chondrocytes transduced with Nanog and in control chondrocytes transduced with empty vector. In vitro cartilage matrix protein formation by Nanog-transduced and control cells was compared using Safranin-O and immunofluorescence stains. We found that after 25 passages, Nanog-transduced chondrocytes maintained significantly higher expression of collagen type II, aggrecan, and cartilage link protein genes than controls. Under chondrogenic conditions, Nanog-transduced cells produced significantly more cartilage-specific matrix than control cells. These findings support the hypothesis that Nanog maintains the human chondrocyte phenotype and function after long-term monolayer culture. Preservation of the chondrocyte phenotype may improve the ability of cultured chondrocytes to repair or restore articular cartilage.

Immunohistochemical characterization of reparative tissue present in human osteoarthritic tissue

Studies involving disease progression in osteoarthritis (OA) have typically focused on the deterioration of native articular cartilage (AC) rather than the de novo cartilage which is frequently present. In general, there are two categories of de novo tissue observed in OA: (1) a pannus-like fibrocartilage that overlays native AC and (2) osteophytes. In this study, 30 AC samples representing a range of disease stages consistent with early to intermediate OA were examined for the occurrence of pannus-like tissue. All AC samples were examined immunohistochemically and compared with cartilage from three mature-looking osteophytes. To accomplish this, serial cartilage sections, derived from total knee arthroplasty specimens, were stained with hematoxylin and eosin and probed with antibodies raised against collagen type I, collagen type II, and aggrecan. Pannus-like tissue ranging from fibrous tissue to fibrocartilage was observed in 3 out of 30 AC samples. The appearance of this tissue was restricted to cartilage displaying signs of intermediate deterioration consistent with Outerbridge grade 2. Collagen type I, collagen type II, and aggrecan were abundant in both pannus-like tissue and osteophyte cartilage. In OA, the intrinsic repair process can yield a range of tissue types between fibrous tissue and fibrocartilage that is well integrated with the underlying, eroded AC. The absence of repair tissue from osteoarthritic samples representing the early stages of AC deterioration indicated that a relationship exists between macroscopic damage and a localized cellular repair response. Several histological and immunohistochemical similarities were also observed between the pannus-like tissue and osteophyte-derived cartilage, suggesting a common developmental process.

Cellular Senescence is a Common Characteristic Shared by Preneoplasic and Osteo-Arthritic Tissue

Objective:

This study aims at highlighting the common signature between cartilaginous tissue in osteoarthritis (OA) and preneoplasic tissues preceding neoplasia and tumour formation and, second, focusing on the molecular mechanisms at the aetiology of both pathologies.

Results:

Because age is the highest risk factor common for both OA and cancer development, it is tempting to compare the molecular mechanisms occurring at the onset of OA and preneoplasic lesions. Indeed, cellular senescence seems to be a common characteristic. Cellular senescence represents a natural barrier to suppress the unscheduled proliferation of damaged cells acting as a strong tumour suppressor pathway and in OA, it also occurs prematurely in chondrocytes. In this study, we review a number of molecular factors associated with the senescent phenotype.

Conclusion:

Whereas accumulation of senescent cells in preneoplasic-like lesions leads to tissue degeneration and potentially tumour development; in OA, senescent cells accumulate in a slowly proliferative tissue. This is likely contributing at reducing the risk of cell transformation.

Tissue formation and vascularization in anatomically shaped human joint condyle ectopically in vivo

Scale-up of bioengineered grafts toward clinical applications is a challenge in regenerative medicine. Here, we report tissue formation and vascularization of anatomically shaped human tibial condyles ectopically with a dimension of 20 x 15 x 15 mm(3). A composite of poly-epsilon-caprolactone and hydroxyapatite was fabricated using layer deposition of three-dimensional interlaid strands with interconnecting microchannels (400 microm) and seeded with human bone marrow stem cells (hMSCs) with or without osteogenic differentiation. An overlaying layer (1 mm deep) of poly(ethylene glycol)-based hydrogel encapsulating hMSCs or hMSC-derived chondrocytes was molded into anatomic shape and anchored into microchannels by gel infusion. After 6 weeks of subcutaneous implantation in athymic rats, hMSCs generated not only significantly more blood vessels, but also significantly larger-diameter vessels than hMSC-derived osteoblasts, although hMSC-derived osteoblasts yielded mineralized tissue in microchannels. Chondrocytes in safranin-O-positive glycosaminoglycan matrix were present in the cartilage layer seeded with hMSC-derived chondrogenic cells, although significantly more cells were present in the cartilage layer seeded with hMSCs than hMSC-derived chondrocytes. Together, MSCs elaborate substantially more angiogenesis, whereas their progenies yield corresponding differentiated tissue phenotypes. Scale up is probable by incorporating a combination of stem cells and their progenies in repeating modules of internal microchannels.

Association between Sub-Clinical Acetabular Dysplasia and a Younger Age at Hip Arthroplasty in Idiopathic Osteoarthritis

This retrospective study was designed to investigate whether sub-clinical acetabular dysplasia, defined by a reduced centre-edge angle of Wiberg, was associated with a younger age at hip arthroplasty in patients with idiopathic osteoarthritis (OA). Fifty-four patients with 69 performed arthroplasties and no previous referral for hip dysplasia were selected from a list of consecutive recipients of hip endoprostheses due to idiopathic OA. The centre-edge angle was measured from standard pelvic radiographs taken a mean of 5.1 years prior to the endoprosthesis operation when there were minimal signs of hip OA. The age at which hip arthroplasty was carried out was compared between those patients with low (20° − 35°) and those with high (≥ 35°) centre-edge angles. The mean age at hip arthroplasty was significantly younger in the group with centre-edge angles of 20° − 35° (65.6 years) compared with those with centre-edge angles ≥ 35° (69.2 years). These results suggest that sub-clinical acetabular dysplasia was associated with a younger age at hip arthroplasty in idiopathic OA.

Bilayered scaffolds for osteochondral tissue engineering

Osteoarthritis (OA) is a prevalent degenerative joint disease that places a significant burden on the socioeconomic efficacy of communities around the world. Tissue engineering repair of articular cartilage in synovial joints represents a potential OA treatment strategy superior to current surgical techniques. In particular, osteochondral tissue engineering, which promotes the simultaneous regeneration of articular cartilage and underlining subchondral bone, may be a clinically relevant approach toward impeding OA progression. The unique and complex functional demands of the two contrasting tissues that comprise osteochondral tissue require the use of bilayered scaffolds to promote individual growth of both on a single integrated implant. This paper reviews the three current bilayered scaffold strategies applied to solve this challenging problem, with a focus on the need for an innovative approach to design and fabrication of new optimized scaffold combinations to reinforce materials science as an important element of osteochondral tissue engineering.

Advanced glycation end products induce cell cycle arrest and proinflammatory changes in osteoarthritic fibroblast-like synovial cells

INTRODUCTION

Advanced glycation end products (AGEs) have been introduced to be involved in the pathogenesis of osteoarthritis (OA). The influence of AGEs on osteoarthritic fibroblast-like synovial cells (FLS) has been incompletely understood as yet. The present study investigates a potential influence of AGE-modified bovine serum albumin (AGE-BSA) on cell growth, and on the expression of proinflammatory and osteoclastogenic markers in cultured FLS.

METHODS

FLS were established from OA joints and stimulated with AGE-BSA. The mRNA expression of p27Kip1, RAGE (receptor for AGEs), nuclear factor kappa B subunit p65 (NFkappaB p65), tumor necrosis factor alpha (TNF-alpha, interleukin-6 (IL-6), receptor activator of NFkappaB ligand (RANKL) and osteoprotegerin was measured by real-time PCR. The respective protein expression was evaluated by western blot analysis or ELISA. NFkappaB activation was investigated by luciferase assay and electrophoretic mobility shift assay (EMSA). Cell cycle analysis, cell proliferation and markers of necrosis and early apoptosis were assessed. The specificity of the response was tested in the presence of an anti-RAGE antibody.

RESULTS

AGE-BSA was actively taken up into the cells as determined by immunohistochemistry and western blots. AGE-induced p27Kip1 mRNA and protein expression was associated with cell cycle arrest and an increase in necrotic, but not apoptotic cells. NFkappaB activation was confirmed by EMSAs including supershift experiments. Anti-RAGE antibodies attenuated all AGE-BSA induced responses. The increased expression of RAGE, IL-6 and TNF-alpha together with NFkappaB activation indicates AGE-mediated inflammation. The decreased expression of RANKL and osteoprotegerin may reflect a diminished osteoclastogenic potential.

CONCLUSIONS

The present study demonstrates that AGEs modulate growth and expression of genes involved in the pathophysiological process of OA. This may lead to functional and structural impairment of the joints.

A review of the differences between normal and osteoarthritis articular cartilage in human knee and ankle joints

BACKGROUND

Osteoarthritis (OA) is the most common joint disease yet its pathophysiology is still poorly understood. It is more prevalent in some lower limb joints than others; in particular the knee is more commonly affected than the ankle. Research into articular cartilage and OA has primarily focussed on using animal models. However, it is apparent that articular cartilage differs between species, so more research is concentrating on human cartilage.

OBJECTIVE

This paper reviews recent studies that have been undertaken to elucidate the reasons for this, and to discover if the findings would alter the conception that articular cartilage is not capable of repair.

METHOD

Primary research papers into human knee and ankle cartilage published since 1997 have been reviewed.

RESULTS

Differences in the structure, metabolism, physical properties and response to trauma have been found, implying that ankle cartilage may be more resistant to damage.

CONCLUSIONS

More research is needed before definitive conclusions can be reached, but the findings so far suggest that OA should not be accepted as the inevitable outcome of joint injury and individuals and practitioners, such as podiatrists, may be able to use simple measures to prevent or delay its onset.

Diclofenac sodium gel in patients with primary hand osteoarthritis: a randomized, double-blind, placebo-controlled trial

OBJECTIVE

To measure the efficacy and safety of diclofenac sodium gel in patients with primary hand osteoarthritis (OA).

METHODS

In a randomized, double-blind, placebo-controlled trial, men and women aged > or = 40 years diagnosed with primary OA in the dominant hand were randomly assigned to self-apply topical 1% diclofenac sodium gel (Voltaren Gel) (n = 198) or vehicle (n = 187) to both hands 4 times daily for 8 weeks. Primary outcome measures included OA pain intensity (100-mm visual analog scale), total Australian/Canadian Osteoarthritis Hand Index (AUSCAN) score, and global rating of disease activity at 4 and 6 weeks. Secondary outcomes included onset of efficacy in Weeks 1 and 2, durability of efficacy at 8 weeks, measures of disease activity in the dominant hand, pain intensity in the non-dominant hand, AUSCAN subindices, end of study rating of efficacy, and Osteoarthritis Research Society International response criteria.

RESULTS

Diclofenac sodium gel decreased pain intensity scores by 42%-45%, total AUSCAN scores by 35%-40%, and global rating of disease by 36%-40%. Significant differences favoring diclofenac sodium gel over vehicle were observed at Week 4 for pain intensity and AUSCAN, with a trend for global rating of disease activity. At Week 6, diclofenac sodium gel treatment significantly improved each primary outcome measure compared with vehicle. Secondary outcomes generally supported the primary outcomes. The most common treatment-related adverse event (AE) was application-site paresthesia. Most AE were mild. No cardiac events, gastrointestinal bleeding, or ulcers were reported.

CONCLUSION

Topical diclofenac sodium gel was generally well tolerated and effective in primary hand OA. (NCT ID: NCT00171665).

The role of obesity, biomechanical constitution of the pelvis and contact joint stress in progression of hip osteoarthritis

OBJECTIVE

The aim of our study was to explore whether earlier hip arthroplasty for idiopathic osteoarthritis (OA) might be explained by enlarged contact stress in the hip joint, and to what amount can that be attributed to obesity and biomechanical constitution of the pelvis.

METHOD

Fifty subjects were selected from a list of consecutive recipients of hip endoprosthesis due to idiopathic OA; standard pelvic radiographs made years prior to surgery were the main selection criteria. For 65 hips resultant hip force and peak contact hip stress normalized to the body weight (R/Wb and p(max)/Wb) were determined from the radiographs with the HIPSTRESS method. Body weight and body mass index (BMI) were obtained with an interview. Regression analysis was used to correlate parameters of obesity (body weight, BMI), biomechanical constitution of the pelvis (R/Wb, p(max)/Wb) and mechanical loading within the hip joint (R, p(max)) with age at hip arthroplasty.

RESULTS

Younger age at hip arthroplasty was associated with higher body weight (P=0.009), higher peak contact hip stress normalized to the body weight - p(max)/Wb (P=0.019), higher resultant hip force -R (P=0.027) and larger peak contact hip stress - p(max) (P<0.001), but not with BMI (P=0.121) or R/Wb (P=0.614).

CONCLUSION

Our results suggest that enlarged contact stress (p(max)) plays an important role in rapid progression of hip OA with both obesity (increased body weight) and unfavorable biomechanical constitution of the pelvis (greater p(max)/Wb) contributing.

Effects of ultrasound frequency, temporal sampling frequency, and spatial sampling step on the quantitative ultrasound parameters of articular cartilage

Quantitative ultrasound imaging may provide a technique for diagnosing initial signs of osteoarthritis (OA), such as surface fibrillation of articular cartilage. Because subchondral sclerosis and osteophyte formation occur in OA as well, ultrasonic analysis of subchondral bone could yield useful diagnostic information. In this study, we investigated whether low-frequency (5 MHz) ultrasound, typically used in bone diagnostics, would be feasible for evaluating the integrity of the surface of the cartilage. The reflection parameters in the time and frequency domains, the ultrasound roughness index, and the wavelet-based parameters were evaluated using ultrasound transducers operating at 5, 10, and 50 MHz frequencies. The effects of variable size of spatial sampling steps and of temporal sampling frequencies were also investigated. Custom-made phantoms and cartilage samples with various surface characteristics were analyzed. The reflection parameters detected the surface degradation with all ultrasound frequencies. The roughness of the surface could only be evaluated reliably with the 50 MHz-focused transducer. In conclusion, simultaneous analysis of the reflection parameters of the cartilage and the subchondral bone is feasible at low (5 MHz) ultrasound frequencies. However, reliable evaluation of the microtopography of the cartilage requires use of a higher ultrasound frequency.

Impaired glucose transporter-1 degradation and increased glucose transport and oxidative stress in response to high glucose in chondrocytes from osteoarthritic versus normal human cartilage

Introduction

Disorders that affect glucose metabolism, namely diabetes mellitus (DM), may favor the development and/or progression of osteoarthritis (OA). Thus far, little is known regarding the ability of chondrocytes to adjust to variations in the extracellular glucose concentration, resulting from hypoglycemia and hyperglycemia episodes, and so, to avoid deleterious effects resulting from deprivation or intracellular accumulation of glucose. The aim of this study was to compare the ability of normal and OA chondrocytes to regulate their glucose transport capacity in conditions of insufficient or excessive extracellular glucose and to identify the mechanisms involved and eventual deleterious consequences, namely the production of reactive oxygen species (ROS).

Methods

Chondrocytes, isolated from normal and OA human cartilage, were maintained in high-density monolayer cultures, in media without or with 10 or 30 mM glucose. Glucose transport was measured as the uptake of 2-deoxy-D-glucose (2-DG). Glucose transporter-1 (GLUT-1) mRNA and protein content were evaluated by real-time RT-PCR and western blot, respectively. ROS production was measured with 2',7'-dichlorodihydrofluorescein diacetate.

Results

Basal and IL-1β-induced 2-DG uptake, including the affinity (1.066 ± 0.284 and 1.49 ± 0.59 mM) and maximal velocity (0.27 ± 0.08 and 0.33 ± 0.08 nmol/μg protein/hour), and GLUT-1 content were identical in normal and OA chondrocytes. Glucose deprivation increased 2-DG uptake and GLUT-1 protein both in normal and OA chondrocytes. Exposure to high glucose (30 mM) for 18 or 48 hours decreased those parameters in normal but not in OA chondrocytes. GLUT-1 mRNA levels were unaffected by high glucose, either in normal or OA chondrocytes. The high glucose-induced reduction in GLUT-1 protein in normal chondrocytes was reversed by treatment with a lysosome inhibitor. High glucose induced ROS production, which lasted significantly longer in OA than in normal chondrocytes.

Conclusions

Normal human chondrocytes adjust to variations in the extracellular glucose concentration by modulating GLUT-1 synthesis and degradation which involves the lysosome pathway. Although capable of adjusting to glucose deprivation, OA chondrocytes exposed to high glucose were unable downregulate GLUT-1, accumulating more glucose and producing more ROS. Impaired GLUT-1 downregulation may constitute an important pathogenic mechanism by which conditions characterized by hyperglycemia, like DM, can promote degenerative changes in chondrocytes that can facilitate the progression of OA.

The chondroprotective effect of selective COX-2 inhibition in osteoarthritis: ex vivo evaluation of human cartilage tissue after in vivo treatment

OBJECTIVE

Recent in vitro studies showed that celecoxib, a selective cyclooxygenase (COX)-2 inhibitor, protects human osteoarthritic cartilage tissue from degeneration. The objective was to substantiate these beneficial effects in an in vivo (clinical) study with celecoxib treatment of patients with severe knee osteoarthritis (OA) and subsequent evaluation of cartilage tissue ex vivo.

METHODS

Patients with knee OA were treated 4 weeks prior to total knee replacement surgery with either celecoxib 200mg b.d., indomethacin 50mg b.d., or received no treatment. During surgery cartilage and synovium were collected and analyzed in detail ex vivo.

RESULTS

When compared to non-treated patients, patients treated with celecoxib showed significant beneficial effects on proteoglycan synthesis, -release, and -content, confirming the in vitro data. In the indomethacin group, no significant differences were found compared to the control group. On the contrary, a tendency towards a lower content and lower synthesis rate was found. In the treated groups prostaglandin-E(2) levels were lower than in the control group, indicating COX-2 inhibition. Ex vivo release of interleukin-1 beta (IL-1 beta) and tumour necrosis factor-alpha by synovial tissue was decreased by treatment with celecoxib, whereas in the indomethacin group only IL-1 beta release was decreased.

CONCLUSION

Using this novel approach we were able to demonstrate an in vivo generated chondrobeneficial effect of celecoxib in patients with end stage knee OA.

Intra-articular depot formulation principles: role in the management of postoperative pain and arthritic disorders

The joint cavity constitutes a discrete anatomical compartment that allows for local drug action after intra-articular injection. Drug delivery systems providing local prolonged drug action are warranted in the management of postoperative pain and not least arthritic disorders such as osteoarthritis. The present review surveys various themes related to the accomplishment of the correct timing of the events leading to optimal drug action in the joint space over a desired time period. This includes a brief account on (patho)physiological conditions and novel potential drug targets (and their location within the synovial space). Particular emphasis is paid to (i) the potential feasibility of various depot formulation principles for the intra-articular route of administration including their manufacture, drug release characteristics and in vivo fate, and (ii) how release, mass transfer and equilibrium processes may affect the intra-articular residence time and concentration of the active species at the ultimate receptor site.

First in Vivo SPECT Imaging of Mouse Femorotibial Cartilage Using 99mTc-NTP 15-5

This study aimed to report the first single-photon emission computed tomographic (SPECT) imaging of articular cartilage in mice using 99mTc-NTP 15-5 radiotracer. Mice intravenously injected with 99mTc-NTP 15-5 were submitted to (1) dynamic planar imaging, (2) static planar imaging, (3) 1 mm pinhole SPECT acquisition, and (4) dissection. Tomographic reconstruction of SPECT data was performed with a three-dimensional ordered subset expectation maximization algorithm, and slices were reconstructed in three axes. 99mTc-NTP 15-5 rapidly accumulated in the joint, with a peak of radioactivity being reached from 5 minutes postinjection and maintained for at least 90 minutes. Given that bone and muscle did not show any accumulation of the tracer, highly contrasted joint imaging was obtained from 15 minutes postinjection. When 1 mm pinhole SPECT acquisition was focused on the knee, the medial and lateral compartments of both the femoral condyle and tibial plateau were highly delineated, allowing a separate quantitation of tracer accumulation within each component of the femorotibial joint. A good correlation was found between tracer uptake determined by region of interest analysis of both planar and SPECT scans and dissection. This new approach to imaging of cartilage in mice provides joint functionality assessment in vivo, giving a unique opportunity to achieve a greater understanding of cartilage physiology in health and disease.

N-((8-hydroxy-5-substituted-quinolin-7-yl)(phenyl)methyl)-2-phenyloxy/amino-acetamide inhibitors of ADAMTS-5 (Aggrecanase-2)

N-((8-Hydroxy-5-substituted-quinolin-7-yl)(phenyl)methyl)-2-phenyloxy/amino-acetamide inhibitors of ADAMTS-5 (Aggrecanase-2) have been prepared. Selected compounds 10, 14, 25, and 53 show sub-microM ADAMTS-5 potency and good selectivity over the related metalloproteases ADAMTS-4 (Aggrecanase-1), MMP-13, and MMP-12. Compound 53 shows a good balance of potent ADAMTS-5 inhibition, moderate CYP3A4 inhibition and good rat liver microsome stability. This series of compounds represents progress towards selective ADAMTS-5 inhibitors as disease modifying osteoarthritis agents.

Surgical suturing of articular cartilage induces osteoarthritis-like changes

INTRODUCTION

In clinical tissue-engineering-based approaches to articular cartilage repair, various types of flap are frequently used to retain an implanted construct within the defect, and they are usually affixed by suturing. We hypothesize that the suturing of articular cartilage is associated with a loss of chondrocytes from, and osteoarthritis-like changes within, the perisutural area.

MATERIALS AND METHODS

We established a large, partial-thickness defect model in the femoral groove of adult goats. The defects were filled with bovine fibrinogen to support a devitalized flap of autologous synovial tissue, which was sutured to the surrounding articular cartilage with single, interrupted stitches. The perisutural and control regions were analyzed histologically, histochemically and histomorphometrically shortly after surgery and 3 weeks later.

RESULTS

Compared to control regions, chondrocytes were lost from the perisutural area even during the first few hours of surgery. During the ensuing 3 weeks, the numerical density of cells in the perisutural area decreased significantly. The cell losses were associated with a loss of proteoglycans from the extracellular matrix. Shortly after surgery, fissures were observed within the walls of the suture channels. By the third week, their surface density had increased significantly and they were filled with avascular mesenchymal tissue.

CONCLUSIONS

The suturing of articular cartilage induces severe local damage, which is progressive and reminiscent of that associated with the early stages of osteoarthritis. This damage could be most readily circumvented by adopting an alternative mode of flap affixation, such as gluing with a biological adhesive.

Thermal rehabilitation and osteoarticular diseases of the elderly

Elderly people with osteoarticular disease (OAD) traditionally visit spas for cycles of treatment comprising mud therapy and balneotherapy. We believe that the thermal environment is a suitable place for providing rehabilitative and preventive treatment both in association with traditional spa therapy and as the sole means of treatment. The aim of this paper is to describe the advantages and possible developments of these integrated approaches to OAD in the elderly.

Transforming growth factor alpha suppression of articular chondrocyte phenotype and Sox9 expression in a rat model of osteoarthritis

OBJECTIVE

To define the roles of transforming growth factor alpha (TGFalpha) in cartilage degradation.

METHODS

Primary rat articular chondrocytes and articular osteochondral explants were cultured with TGFalpha to assess the effects of TGFalpha on chondrocyte physiology and phenotype.

RESULTS

TGFalpha altered chondrocyte morphology through reorganization of the actin cytoskeleton and formation of stress fibers. Expression of anabolic genes, including aggrecan, type II collagen, and cartilage link protein, was reduced in response to TGFalpha. Proliferation of chondrocytes and formation of articular chondrocyte clusters was stimulated by TGFalpha. Expression of matrix metalloproteinase 13 and cathepsin C was increased by TGFalpha. We demonstrated the down-regulation of Sox9 messenger RNA and protein levels by TGFalpha. This was associated with reduced levels of phosphorylated and total SOX9 in cartilage explants upon TGFalpha treatment. In contrast, another growth factor identified in our microarrays, Kitl, had no effects on the chondrocyte parameters tested. To examine correlations between the increased levels of TGFalpha in experimental knee osteoarthritis (OA) with the levels of TGFalpha in humans with knee OA, a microarray analysis of mRNA from 13 normal and 12 late-stage OA cartilage samples was performed. Seven OA samples showed TGFA mRNA levels similar to those in the normal controls, but expression was markedly increased in the other 5 OA samples. These data confirm that TGFA transcript levels are increased in a subset of patients with OA.

CONCLUSION

This study adds TGFalpha to the list of dysregulated cytokines present in degrading cartilage in OA. Since TGFalpha inhibits articular chondrocyte anabolic capacity, increases catabolic factors, and contributes to the development of chondrocyte clusters, TGFalpha may be a potential target for therapeutic strategies in the treatment of OA.

Global analyses of gene expression in early experimental osteoarthritis

OBJECTIVE

To analyze genome-wide changes in chondrocyte gene expression in a surgically induced model of early osteoarthritis (OA) in rats, to assess the similarity of this model to human OA, and to identify genes and mechanisms leading to OA pathogenesis.

METHODS

OA was surgically induced in 5 rats by anterior cruciate ligament transection and partial medial meniscectomy. Sham surgery was performed in 5 additional animals, which were used as controls. Both groups underwent 4 weeks of forced mobilization, 3 times per week. RNA was extracted directly from articular chondrocytes in the OA (operated), contralateral, and sham-operated knees. Affymetrix GeneChip expression arrays were used to assess genome-wide changes in gene expression. Expression patterns of selected dysregulated genes, including Col2a1, Mmp13, Adamts5, Ctsc, Ptges, and Cxcr4, were validated by real-time polymerase chain reaction, immunofluorescence, or immunohistochemistry 2, 4, and 8 weeks after surgery.

RESULTS

After normalization, comparison of OA and sham-operated samples showed 1,619 differentially expressed probe sets with changes in their levels of expression > or = 1.5-fold, 722 with changes > or = 2-fold, 135 with changes > or = 4-fold, and 20 with changes of 8-fold. Dysregulated genes known to be involved in human OA included Mmp13, Adamts5, and Ptgs2, among others. Several dysregulated genes (e.g., Reln, Phex, and Ltbp2) had been identified in our earlier microarray study of hypertrophic chondrocyte differentiation. Other genes involved in cytokine and chemokine signaling, including Cxcr4 and Ccl2, were identified. Changes in gene expression were also observed in the contralateral knee, validating the sham operation as the appropriate control.

CONCLUSION

Our results demonstrate that the animal model mimics gene expression changes seen in human OA, supporting the relevance of newly identified genes and pathways to early human OA. We propose new avenues for OA pathogenesis research and potential targets for novel OA treatments, including cathepsins and cytokine, chemokine, and growth factor signaling pathways, in addition to factors controlling the progression of chondrocyte differentiation.

Synthesis and evaluation of aryl thioxothiazolidinone inhibitors of ADAMTS-5 (Aggrecanase-2)

5-Benzylidene-2-thioxo-thiazolidin-4-one inhibitors of ADAMTS-5 (Aggrecanase-2) have been prepared via commercially available starting materials. The identified compounds show micromolar ADAMTS-5 potency and demonstrate SAR trends for both the aryl group and thioxothiazolidinone zinc chelator. This series of compounds represents steps toward a metalloprotease inhibitor as a disease-modifying osteoarthritis drug.