Experimentally induced degenerative joint lesions following partial meniscectomy in the rabbit

Rabbit knee joint biomechanics: motion analysis and modeling of forces during hopping

Although the rabbit hindlimb has been commonly used as an experimental animal model for studies of osteoarthritis, bone growth and fracture healing, the in vivo biomechanics of the rabbit knee joint have not been quantified. The purpose of this study was to investigate the kinematic and kinetic patterns during hopping of the adult rabbit, and to develop a model to estimate the joint contact force distribution between the tibial plateaus. Force platform data and three-dimensional motion analysis using infrared markers mounted on intracortical bone pins were combined to calculate the knee and ankle joint intersegmental forces and moments. A statically determinate model was developed to predict muscle, ligament and tibiofemoral joint contact forces during the stance phase of hopping. Variations in hindlimb kinematics permitted the identification of two landing patterns, that could be distinguished by variations in the magnitude of the external knee abduction moment. During hopping, the prevalence of an external abduction moment led to the prediction of higher joint contact forces passing through the lateral compartment as compared to the medial compartment of the knee joint. These results represent critical data on the in vivo biomechanics of the rabbit knee joint, which allow for comparisons to both other experimental animal models and the human knee, and may provide further insight into the relationships between mechanical loading, osteoarthritis, bone growth, and fracture healing.

Arthroscopy -- a potential "gold standard" for the diagnosis of the chondropathy of early osteoarthritis

OBJECTIVES

The aims of this study were to: 1. Evaluate the performance of arthroscopy for the diagnosis of chondropathy and to compare it to that of direct non-arthroscopic assessments; 2. Determine intra-observer reliability of arthroscopic assessments; 3. Evaluate the effects of the arthroscopic video quality and probing upon diagnostic performance.

DESIGN

The ovine medial meniscectomy (MMx) model of early osteoarthritis (OA) was used assuming that pre-MMx articular cartilage (AC) was "normal" and post-MMx AC "chondropathic". Video recordings of arthroscopic assessments of each stifle compartment were evaluated. Scores were given for the quality of the video and the amount of probing. The diagnostic performances of dynamic shear modulus (G), light microscopic assessment and superficial zone collagen birefringence assessments were evaluated and compared to that of arthroscopy. Intra-observer reliability of arthroscopic assessments was also evaluated.

RESULTS

Arthroscopic assessments had high sensitivity (91-100%), specificity (62-88%) and accuracy (75-93%) for the diagnosis of chondropathy 16 weeks after MMx. Arthroscopy compared favourably with the direct non-arthroscopic assessments in the lateral compartment and was found to have extremely high intra-observer reliability (kappa 0.78-1.00). The quality of arthroscopic video recordings and the amount of probing did not significantly influence accuracy or reliability.

CONCLUSIONS

Arthroscopy performs as well as direct non-arthroscopic assessments of AC for diagnosis of early OA. These results suggest that arthroscopy can be used as a "gold standard" for the validation of non-invasive assessments like magnetic resonance imaging and that arthroscopic diagnosis can be based on small amounts of video footage without AC probing.

Increase in degraded collagen type II in synovial fluid early in the rabbit meniscectomy model of osteoarthritis

OBJECTIVE

The objective of this study was to determine whether collagen type II breakdown products in synovial fluid (SF), detected by an enzyme-linked immunoassay, represent a useful marker for early events in osteoarthritis (OA) in the rabbit medial meniscectomy model.

DESIGN

Complete medial meniscectomy was performed on the right knee joints of 32 rabbits. Balanced groups of rabbits were then sacrificed at 2, 4, 8, and 12 weeks post-surgery. An additional 8 unoperated and 11 sham-operated animals served as controls. SF lavages were performed on right and left knee joints of the same animals at sacrifice. The proteolytic epitope of type II collagen was monitored using an enzyme-linked immunoassay.

RESULTS

Macroscopically visible surface fibrillation and focal erosions appeared as early as 2 weeks after meniscectomy in the femorotibial joint (P<0.01). OA developed gradually during the later observation period, and then predominantly on the medial tibial plateau and medial femur. Significant histological alterations in cartilage, including a loss of proteoglycans, surface irregularities, and clefts, were detected at 2 weeks after meniscectomy (P<0.01). Collagen type II epitope levels in SF lavage samples were elevated peaking at 2 weeks after meniscectomy (P<0.02). Levels decreased at later time points, but they were still raised at 12 weeks (P< or =0.05). Highly significant correlations were found between the SF collagen type II epitope levels and the macroscopic and microscopic scoring results (Spearman rho correlation coefficient, macroscopy-collagen type II epitope r=0.222, P=0.025; microscopy-collagen type II epitope r=0.436, P< or =0.01).

CONCLUSION

In this rabbit model of medial meniscectomy, levels of type II collagen fragments in SF appear to provide a useful marker of the early degenerative changes.

The effects of cyclic mechanical strain and tumor necrosis factor alpha on the response of cells of the meniscus

OBJECTIVES

Cells of the knee meniscus respond to changes in their biochemical and biomechanical environments with alterations in the biosynthesis of matrix constituents and inflammatory mediators. Tumor necrosis factor alpha (TNF-alpha) is a pro-inflammatory cytokine that is involved in the pathogenesis of both osteoarthritis and rheumatoid arthritis, but its influence on meniscal physiology or mechanobiology is not fully understood. The objectives of this study were to examine the hypothesis that cyclic mechanical strain of meniscal cells modulates the biosynthesis of matrix macromolecules and pro-inflammatory mediators, and to determine if this response is altered by TNF-alpha.

METHODS

Cells were isolated from the inner two-thirds of porcine medial menisci and subjected to biaxial tensile strain of 5-15% at a frequency of 0.5Hz. The synthesis of proteoglycan, protein, nitric oxide (NO), and prostaglandin E(2) were determined.

RESULTS

Cyclic tensile strain increased the production of nitric oxide through the upregulation of nitric oxide synthase 2 (NOS2) and also increased synthesis rates of prostaglandin E(2), proteoglycan, and total protein in a manner that depended on strain magnitude. TNF-alpha increased the production of NO and total protein, but inhibited proteoglycan synthesis rates. TNF-alpha prevented the mechanical stimulation of proteoglycan synthesis, and this effect was not dependent on NOS2.

CONCLUSIONS

These findings indicate that pro-inflammatory cytokines can modulate the responses of meniscal cells to mechanical signals, suggesting that both biomechanical and inflammatory factors could contribute to the progression of joint disease as a consequence of altered loading of the meniscus.

Histopathological correlation of cartilage swelling detected by magnetic resonance imaging in early experimental osteoarthritis

OBJECTIVE

We previously reported that an increase of cartilage thickness is the earliest measurable change by magnetic resonance imaging (MRI) in early stages of experimental osteoarthritis (OA). Our present objective was to study the microscopic translation of this finding in order to know whether the cartilage thickness increment represents the earliest structural damage or whether it alternatively constitutes a non-progressive reversible phenomenon.

METHODS

OA was induced by partial medial meniscectomy in rabbits. Normal and sham-operated animals were used as controls. Gross and microscopic cartilage changes were sequentially assessed after surgery at 0, 2, 4, 6, 8, 10 and 52 weeks, and compared to MRI findings.

RESULTS

The swelling of cartilage detected by MRI correlated with depletion in matrix proteoglycans and cellular loss, which were closely related to the progression of OA at the earliest stages. Abnormalities of the cartilage structure appeared only in advanced OA.

CONCLUSION

Cartilage swelling detected by MRI is due to proteoglycan depletion and represents the earliest abnormality in OA. Because it is accompanied by cellular loss, it cannot be merely attributed to surgical trauma and represents true tissue damage. The biological meaning of volume variations detected by MRI should be assessed carefully taking into account the disease stage as an increase in cartilage height also reflects cartilage damage and not a reparative process.

The role of biomechanics and inflammation in cartilage injury and repair

Osteoarthritis is a painful and debilitating disease characterized by progressive degenerative changes in the articular cartilage and other joint tissues. Biomechanical factors play a critical role in the initiation and progression of this disease, as evidenced by clinical and animal studies of alterations in the mechanical environment of the joint caused by trauma, joint instability, disuse, or obesity. The onset of these changes after joint injury generally has been termed posttraumatic arthritis and can be accelerated by factors such as a displaced articular fracture. Within this context, there is considerable evidence that interactions between biomechanical factors and proinflammatory mediators are involved in the progression of cartilage degeneration in posttraumatic arthritis. In vivo studies have shown increased concentrations of inflammatory cytokines and mediators in the joint in mechanically induced models of osteoarthritis. In vitro explant studies confirm that mechanical load is a potent regulator of matrix metabolism, cell viability, and the production of proinflammatory mediators such as nitric oxide and prostaglandin E2. Knowledge of the interaction of inflammatory and biomechanical factors in regulating cartilage metabolism would be beneficial to an understanding of the etiopathogenesis of posttraumatic osteoarthritis and in the improvement of therapies for joint injury.

Intra-articular hyaluronate in experimental rabbit osteoarthritis can prevent changes in cartilage proteoglycan content

OBJECTIVE

The purpose of this study was to determine the effects of intra-articular injections of high molecular weight (2000 kDa) sodium hyaluronate (HA) on the progression of articular cartilage degeneration in a rabbit partial medial meniscectomy model of osteoarthritis.

DESIGN

Six experimental groups included normal, sham operated, and operated and injected animals, the latter injected once-weekly (for two weeks or twelve weeks, beginning four weeks after surgery) with either 1% (w/v) HA or phosphate buffered saline (PBS). Following assessment of gross morphology, serial adjacent blocks of full-depth articular cartilage were prepared from the tibial condyle for analysis of total water, hydroxyproline, DNA and proteoglycan (uronic acid) content, as well as the ratio of galactosamine to glucosamine. Samples were sub-divided into inner (medial) and outer (lateral) regions.

RESULTS

No morphological differences were recognized between joints injected with PBS and those receiving HA. When analysed biochemically, there were no significant differences in hydration, hydroxyproline or DNA content between the experimental groups. In contrast, HA injection did affect changes in proteoglycan content. Expressed per tissue dry weight, uronic acid content in the operated group injected with PBS for two weeks was lower than normal (P<0.02), a result not seen in the corresponding HA injected group. After 12 weeks of PBS injections, uronic acid content (per dry weight) was higher than normal (P<0.01), an effect again not observed in the corresponding HA injected group. Results for the galactosamine: glucosamine ratio showed a reduction after 12 weeks of injections, but no differences between PBS and HA injected groups.

CONCLUSIONS

Once-weekly, intra-articular injection of high molecular weight HA can prevent changes in proteoglycan content in tibial condylar articular cartilage, compared to PBS injected controls, in the rabbit partial meniscectomy model of osteoarthritis.

Sodium iodoacetate-induced experimental osteoarthritis and associated pain model in rats

Degenerative lesions were induced in the knee joint of Wistar rats by intraarticular injection of chondrocyte metabolism inhibitor mono-iodoacetate (MIA) at doses of 0, 0.3 or 3 mg/joint. Histopathological examination and the measurement of hind paw weight ratio as an index of joint pain by incapacitance tester were performed. Histological findings that are similar to those observed in human osteoarthritis (OA), such as disorganization of chondrocytes, erosion and fibrillation of cartilage surface, and subchondral bone exposure etc., were observed in a MIA-dose-dependent manner. Saflanin-O fast green staining revealed that marked diffuse reduction of proteoglycan in cartilage tissue of rats treated with MIA. The clinical scores of the joint pain were closely correlated to the grade of histological findings. We conclude that the present experimental model in combination with a novel dual channel weight averager would be very useful for the study of human OA, and could be applied for estimation of therapeutic effect of new anti-OA drugs.

Cell-based therapy for meniscal repair: a large animal study

BACKGROUND

The avascular portion of the meniscus cartilage in the knee does not have the ability to repair spontaneously.

HYPOTHESIS

Cell-based therapy is able to repair a lesion in the swine meniscus.

STUDY DESIGN

Controlled laboratory study.

METHODS

Sixteen Yorkshire pigs were divided into four groups. A longitudinal tear was produced in the avascular portion of the left medial meniscus of 4 pigs. Autologous chondrocytes were seeded onto devitalized allogenic meniscal slices and were secured inside the lesion with two sutures. Identical incisions were created in 12 other pigs, which were used as three separate control groups: 4 animals treated with an unseeded scaffold, 4 were simply sutured, and 4 were left untreated. Meniscal samples were collected after 9 weeks, and the samples were analyzed grossly, histologically, and histomorphometrically.

RESULTS

Gross results showed bonding of the lesion margins in the specimens of the experimental group, whereas no repair was noted in any of the control group specimens. Histological and histomorphometrical analysis showed multiple areas of healing in the specimens of the experimental group.

CONCLUSIONS

This study demonstrated the ability of seeded chondrocytes to heal a meniscal tear.

CLINICAL RELEVANCE

Cell-based therapy could be a potential tool for avascular meniscus repair.

A critical appraisal of quantitative arthroscopy as an outcome measure in osteoarthritis of the knee

BACKGROUND AND OBJECTIVES

To review the performance of arthroscopic assessment of articular cartilage damage in osteoarthritis.

METHODS

The literature was reviewed for publications containing data regarding validity and reliability of arthroscopic systems of cartilage evaluation in knee osteoarthritis.

RESULTS

Fifty-two distinct measurement systems were identified in 60 publications. There were 30 simple severity-scoring systems, 3 global visual analogue scale systems, and 19 composite systems. No systems consisted solely of measurements of lesion size or site, although 13 systems used either or both of these for the calculation of composite scores. Only 6 publications (10%) undertook any reliability evaluation and these generally used inappropriate methods of statistical analysis. Thirty-five publications (58%) evaluated validity. Construct validity was tested using several constructs (clinical in 2, magnetic resonance imaging in 10, radiographs in 10, or other arthroscopic assessments in 5 publications). Criterion validity was ascertained by using several methods including cartilage histology, histochemistry, or biomechanics in 10 publications. Responsiveness was determined in 1 publication.

DISCUSSION

Many publications evaluated composite systems but only a few evaluated fundamental aspects of arthroscopic measurement. Conceptually, composite scoring systems have the best validity; however, at present, there is only enough evidence to support the use of simple chondropathy severity scores and there are little data on the responsiveness of these methods. A proposed program for comprehensive evaluation and development of valid and responsive arthroscopic assessments of articular cartilage is outlined.

Regulation of matrix turnover in meniscal explants: role of mechanical stress, interleukin-1, and nitric oxide

The meniscus is an intra-articular fibrocartilaginous structure that serves essential biomechanical roles in the knee. With injury or arthritis, the meniscus may be exposed to significant changes in its biochemical and biomechanical environments that likely contribute to the progression of joint disease. The goal of this study was to examine the influence of mechanical stress on matrix turnover in the meniscus in the presence of interleukin-1 (IL-1) and to determine the role of nitric oxide (NO) in these processes. Explants of porcine menisci were subjected to dynamic compressive stresses at 0.1 MPa for 24 h at 0.5 Hz with 1 ng/ml IL-1, and the synthesis of total protein, proteoglycan, and NO was measured. The effects of a nitric oxide synthase 2 (NOS2) inhibitor were determined. Dynamic compression significantly increased protein and proteoglycan synthesis by 68 and 58%, respectively, compared with uncompressed explants. This stimulatory effect of mechanical stress was prevented by the presence of IL-1 but was restored by specifically inhibiting NOS2. Release of proteoglycans into the medium was increased by IL-1 or mechanical compression and further enhanced by IL-1 and compression together. Stimulation of proteoglycan release in response to compression was dependent on NOS2 regardless of the presence of IL-1. These finding suggest that IL-1 may modulate the effects of mechanical stress on extracellular matrix turnover through a pathway that is dependent on NO.

Pathways of load-induced cartilage damage causing cartilage degeneration in the knee after meniscectomy

Results of both clinical and animal studies show that meniscectomy often leads to osteoarthritic degenerative changes in articular cartilage. It is generally assumed that this process of cartilage degeneration is due to changes in mechanical loading after meniscectomy. It is, however, not known why and where this cartilage degeneration starts. Load induced cartilage damage is characterized as either type (1)--damage without disruption of the underlying bone or calcified cartilage layer--or type (2), subchondral fracture with or without damage to the overlying cartilage. We asked the question whether cartilage degeneration after meniscectomy is likely to be initiated by type (1) and/or type (2) cartilage damage. To investigate that we applied an axisymmetric biphasic finite element analysis model of the knee joint. In this model the articular cartilage layers of the tibial and the femoral condyles, the meniscus and the bone underlying the articular cartilage of the tibia plateau were included. The model was validated with data from clinical studies, in which the effects of meniscectomy on contact areas and pressures were measured. It was found that both the maximal values and the distributions of the shear stress in the articular cartilage changed after meniscectomy, and that these changes could lead to both type (1) and type (2) cartilage damage. Hence it likely that the cartilage degeneration seen after meniscectomy is initiated by both type (1) and type (2) cartilage damage.

Glucosamine and chondroitin sulfate: biological response modifiers of chondrocytes under simulated conditions of joint stress

OBJECTIVE

To test the hypothesis that chondrocytes are more responsive to the chondroprotective agents, glucosamine (glcN) and chondroitin sulfate (CS), under in vitro conditions simulating in vivo joint stress.

DESIGN

Synthetic and anticatabolic activities of bovine articular cartilage were assayed using 35-sulfate labeling and assaying the specific activity of glycosaminoglycans (GAGs) under the conditions of enzyme-induced matrix depletion, heat stress, mechanical compression and cytokine stress.

RESULTS

The response of cartilage to simulated conditions of in vivo stress varies, depending on the type stress and age of the animal. Cartilage from aged animals was more responsive to stress and to glcN and CS. Pronase-induced matrix depletion and mechanical stress increased proteoglycan synthetic activity. Exposure to glcN and CS significantly enhanced this stress response from 85 to 191% and from 40 to 1000%, respectively. Heat stress and stromelysin digestion decreased synthetic activity, which was reversed or normalized on exposure to glcN and CS. Cartilage from young joints was somewhat refractory to the level of stress imposed and to treatment with glcN and CS.

CONCLUSION

The metabolic response of cartilage from aged animals to glcN and CS under simulated conditions of in vivo stress is significantly greater than that seen in nonstressed or young tissue. By enhancing the "protective" metabolic response of chondrocytes to stress, glcN and CS may improve its ability for repair and regeneration. These observations suggest that these compounds function as biological response modifiers (BRMs), agents which boost natural protective responses of tissues under adverse environmental conditions.

Induction of osteoarthritis in the rat by surgical tear of the meniscus: Inhibition of joint damage by a matrix metalloproteinase inhibitor

OBJECTIVE

Characterize a model of osteoarthritis (OA) induced by a surgically transecting the medial collateral ligament and meniscus. Evaluate the effectiveness of a matrix metalloproteinase (MMP) inhibitor in this model.

METHODS

The medial collateral ligament of the right knee of rats was transected and a single full thickness cut was made through meniscus. Rats were sacrificed at various times after the surgery to assess the severity of gross cartilage damage using an image analyser and microscopically by histology. The effect of an MMP inhibitor in this model was assessed by administering compound twice daily for the 21 days and evaluating gross and histological joint damage at day 21. The in vitro potency of the MMP inhibitor (MMPI) against a panel of human recombinant MMPs was assessed kinetically using a quenched fluorescent substrate.

RESULTS

Surgical transection of the medial collateral ligament and meniscus resulted in a time dependent increase in the severity of the cartilage lesion (depth) as measured histologically but only a slight increase in the area of the lesion as assessed grossly by image analysis. Administration of a MMPI orally twice daily (b.i.d.) at 25mg/kg to rats in the meniscal tear model resulted in significant inhibition of cartilage degradation and osteophyte formation (total joint score) of 39+/-7% (mean+/-S.E.M., from four separate experiments).

CONCLUSION

These results demonstrate that MMP inhibition is effective in reducing the joint damage that occurs in the meniscal tear model of OA and support a potential therapeutic role for MMP inhibition in the treatment of human OA.

Chondropathy after meniscal tear or partial meniscectomy in a canine model

A primary goal in considering treatment for meniscal injuries is the preservation of the health of the articular cartilage. However, the chondroprotective effects of various techniques for meniscal injury treatments are unknown. We used a canine model to quantify articular cartilage degeneration in the medial compartment of the canine knee, resulting from a surgically created tear or a partial meniscectomy (PM) of the posterior region of the medial meniscus (each group, n = 10). After sacrifice at 12 weeks, the development of gross chondropathy and the changes in cartilage tensile stiffness were quantified, and correlations between these measurements were examined. Both treatment surgical treatment groups caused significantly greater gross chondropathy as compared to the unoperated contralateral controls. Cartilage tensile stiffness was significantly lower than unoperated controls by nearly 28% in both experimental groups. However, there were no significant differences observed between the gross chondropathy or the cartilage mechanical property changes between the experimental groups. Importantly, the severity of gross chondropathy was found to significantly correlate with the decrement in tensile stiffness properties of the articular cartilage. These findings indicate that significant degeneration of canine articular cartilage develops to a similar degree in the presence of a partially healed meniscus tear or a PM of the knee.

Synovial fluid biomarker levels predict articular cartilage damage following complete medial meniscectomy in the canine knee

The purposes of this study were to document the histological changes present in the tibial plateaus 12 weeks after complete medial meniscectomy in dogs and to determine if synovial lavage fluid biomarker levels are predictive of the severity of joint damage. Twelve adult dogs underwent complete unilateral medial meniscectomy and synovial lavage fluid biomarker levels, including cartilage oligomeric matrix protein (COMP), keratan sulfate (5D4). 3B3(-), and 3B3(+), were measured serially at 4-week intervals. The dogs were euthanized 12 weeks after surgery and each medial and lateral tibial plateau from the meniscectomized and contralateral knees was graded histologically. Histological data were analyzed using principal components analysis, which resulted in 4 factors that explained 70% of the variation in the data. Factor 2 (weighted most heavily by subchondral bone thickness) and Factor 3 (representative of articular cartilage damage) were significantly affected by compartmental site (P < 0.01 for both). Both of these factors were highest in the medial tibial plateau of the meniscectomized knee, and Factor 3 was significantly higher in this site than in the medial tibial plateau of the contralateral knee (P < 0.01). Peak levels of all 4 synovial lavage fluid biomarkers occurred at 4 weeks post-meniscectomy and 4-week minus baseline levels of all biomarkers were significantly correlated with the Factor 3 scores. This study demonstrates that significant articular cartilage damage occurs relatively quickly following complete medial meniscectomy in dogs and establishes the content and criterion validity for these synovial fluid lavage biomarkers in canine meniscectomy as surrogate measures of articular cartilage damage.

Moderation of iodoacetate-induced experimental osteoarthritis in rats by matrix metalloproteinase inhibitors

OBJECTIVE

To determine the effect of matrix metalloproteinase (MMP) inhibitors in mono-iodoacetate-induced arthritis in rats.

DESIGN

The ability of compounds to inhibit MMPs in vitro was assessed kinetically using a quenched fluorescent substrate. Rats were injected with iodoacetate intraarticularly in one knee joint and damage to the tibial plateau was evaluated from digitized images captured using an image analyser and by histology. Collagenase and gelatinase activity in cartilage from iodoacetate injected knees were evaluated using(3)H-rat type I collagen and gelatin zymography, respectively.

RESULTS

Collagenase and gelatinase activity significantly increased in the knee cartilage of rats injected with iodoacetate with peak activity by day 7. Three MMP inhibitors were examined for their efficacy in the rat iodoacetate-induced arthritis model. Significant (P< 0.05) inhibition of cartilage damage was observed in animals treated orally with 35 mg/kg b.i.d. of the three different MMP inhibitors. Inhibition of cartilage damage by the MMP inhibitors ranged from 36-42%.

CONCLUSION

MMP inhibitors are partially protective against cartilage and subchondral bone damage induced by iodoacetate. These results support an important role for MMPs in mediating the joint damage in this model of arthritis.

Chondrocyte apoptosis and regional differential expression of nitric oxide in the medial meniscus following partial meniscectomy

Partial medial meniscectomy leads to tibial articular cartilage degeneration. Nitric oxide (NO) production increases with the development of osteoarthritis (OA) and has been shown to have a catabolic effect on chondrocytes. Since distribution of chondrocytic and fibroblastic cell types within the total cell population comprising meniscus is region-specific, we compared NO production in the peripheral and central regions of the medial meniscus 12 weeks after partial medial meniscectomy and assessed chondrocyte apoptosis and NO production in the tibial articular cartilage. Additionally, transcriptional gene expression of inducible nitric oxide synthetase (iNOS) and immunohistochemical staining of nitrotyrosine were examined. The results showed that following partial medial meniscectomy, NO production in the central region of the medial meniscus and in the tibial articular cartilage were significantly higher than respective NO levels in normal and sham-operated controls. Reverse transcription polymerase chain reaction (RT-PCR) revealed a high transcriptional expression of the iNOS gene in the central region of the meniscus and in tibial articular cartilage following partial medial meniscectomy. Nitrotyrosine immunoreactivity was prominent in the central region of the medial meniscus and in the deep layer of the tibial articular cartilage and apoptotic cells were also detected in situ in the superficial zone of the tibial articular cartilage and central regions of the medial meniscus following partial medial meniscectomy. These observations suggest that the central region of the meniscus is responsible for NO synthesis associated with apoptosis in both meniscal and articular cartilage cells following partial meniscectomy.

High-resolution MRI detects cartilage swelling at the early stages of experimental osteoarthritis

OBJECTIVE

The progressive early changes in cartilage and subchondral bone in an experimental model of osteoarthritis (OA) were investigated with high-resolution magnetic resonance imaging (MRI) and microradiography.

METHODS

Partial medial meniscectomy was performed in the left knee of 16 rabbits. Four normal and four sham-operated additional rabbits were used as controls. Changes in cartilage and subchondral bone were sequentially assessed after surgery with MRI at 0, 2, 4, 6, 8 and 10 weeks, subchondral bone variations quantified postoperatively on microradiographs of sagittal sections at 6 and 10 weeks and the macroscopic alterations graded according to the severity of joint changes.

RESULTS

MRI demonstrated a progressive increase in the articular cartilage thickness in the weight-bearing area of the femur at weeks 4, 6 and 8 vs basal. Tibial cartilage thickness only showed a significant increment at week 6. No significant abnormalities were detected on X-rays in subchondral bone when compared to controls. Macroscopically, 4 weeks after the operation OA rabbits had only slight cartilage discoloration. Cartilage eburnation, pitting, superficial erosions and osteophytes were detected at week 6. These abnormalities were more evident at 8 and 10 weeks after meniscectomy.

CONCLUSION

The focal increase in cartilage thickness is one of the earliest measurable changes in OA and preceeds subchondral bone remodeling. The measurement of cartilage thickness variations with MRI can be used to follow the course of OA and to evaluate the potential beneficial effect of novel therapies.

Capsular disruption as a complication of thermal alteration of the glenohumeral capsule

Thermal energy, delivered through various means, has been used to alter the length of collagen in the unstable shoulder. Laboratory studies have shown that the collagen, following thermal alteration, has reduced strength. We present a case of radiofrequency capsulorrhaphy of the shoulder for symptomatic posterior instability in a multidirectionally lax patient that led to early catastrophic failure of the capsule, with complete capsular disruption and hyaline degeneration of the treated tissue.

Strontium ranelate increases cartilage matrix formation

Based on previous studies showing that strontium ranelate (S12911) modulates bone loss in osteoporosis, it could be hypothesized that this drug also is effective on cartilage degradation in osteoarthritis (OA). This was investigated in vitro on normal and OA human chondrocytes treated or not treated with interleukin-1beta (IL-1beta). This model mimics, in vitro, the imbalance between chondroformation and chondroresorption processes observed in vivo in OA cartilage. Chondrocytes were isolated from cartilage by enzymatic digestion and cultured for 24-72 h with 10(-4)-10(-3) M strontium ranelate, 10(-3) M calcium ranelate, or 2 x 10(-3) M SrCl2 with or without IL-1beta or insulin-like growth factor I (IGF-I). Stromelysin activity and stromelysin quantitation were assayed by spectrofluorometry and enzyme amplified sensitivity immunoassay (EASIA), respectively. Proteoglycans (PG) were quantified using a radioimmunoassay. Newly synthesized glycosaminoglycans (GAGs) were quantified by labeled sulfate (Na2(35)SO4) incorporation. This method allowed the PG size after exclusion chromatography to be determined. Strontium ranelate, calcium ranelate, and SrCl2 did not modify stromelysin synthesis even in the presence of IL-1beta. Calcium ranelate induced stromelysin activation whereas strontium compounds were ineffective. Strontium ranelate and SrCl2 both strongly stimulated PG production suggesting an ionic effect of strontium independent of the organic moiety. Moreover, 10(-3) M strontium ranelate increased the stimulatory effect of IGF-I (10(-9) M) on PG synthesis but did not reverse the inhibitory effect of IL-1beta. Strontium ranelate strongly stimulates human cartilage matrix formation in vitro by a direct ionic effect without stimulating the chondroresorption processes. This finding provides a preclinical basis for in vivo testing of strontium ranelate in OA.

In vivo chondroprotection and metabolic synergy of glucosamine and chondroitin sulfate

Supplements of glucosamine hydrochloride, low molecular weight chondroitin sulfate, and manganese ascorbate were tested separately and in combination for their ability to retard progression of cartilage degeneration in a rabbit instability model of osteoarthrosis. Computerized quantitative histologic evaluation of safranin O stained sections of the medial femoral condyles measured the grade and extent of tissue involvement of lesions. Severe lesions (Mankin grade greater than 7) were absent in all animals supplemented with a dietary mixture of glucosamine, chondroitin sulfate, and manganese ascorbate. Total linear involvement (mm of lesioned surface) and total grade (mean grade x number of lesions per animal) were reduced significantly in animals given the combination compared with controls (59% and 74% respectively). Animals supplemented with glucosamine, chondroitin sulfate, or manganese ascorbate alone had less moderate and severe tissue involvement than controls but not to the extent of the combined group. In vitro, a combination of glucosamine hydrochloride and chondroitin sulfate acted synergistically in stimulating glycosaminoglycan synthesis (96.6%). Chondroitin sulfate and manganese ascorbate but not glucosamine were effective in inhibiting degradative enzyme activity. These data suggest that the disease modifying effect (the ability to retard progression of cartilage degeneration) of a mixture of glucosamine, chondroitin sulfate, and manganese ascorbate is more efficacious than either agent alone.

The acute structural changes of loaded articular cartilage following meniscectomy or ACL-transection

OBJECTIVE

Meniscectomy and anterior cruciate ligament (ACL) rupture have been identified as precursors of osteoarthrosis (OA) in clinical reviews and animal experiments. In this study, the acute effects of these injuries on articular cartilage matrix deformation, preserved in a loaded state using a cryopreservation technique, were studied by scanning electron microscopy (SEM).

METHOD

Whole knee joints from adult White New Zealand rabbits (N=87) were loaded ex vivo, using a simulated quadriceps pull under static and cyclic loading conditions, following medial meniscectomy or transection of the ACL. Specimens were plunge-frozen while under load, or following a recovery period, and prepared for SEM by cryofixation. Using SEM and photographic images, the medial tibial plateau cartilage was assessed both qualitatively and quantitatively.

RESULTS

After meniscectomy, significantly increased bending and crimping of radial collagen fibers occurred with static loading. Compared to intact knees, the area of tibial cartilage showing an indentation was increased by 80% (P< 0.05), the articular cartilage thickness was significantly more reduced when under load (for high force long duration static loading, intact joints had 53%+/-3 reduction in cartilage thickness compared to 39%+/-4 after meniscectomy, P< 0.05), and it took nearly twice as long for the cartilage thickness to recover following loading. These post-meniscectomy differences were either not present or were minimal when the joint was allowed to extend when loaded. ACL-transection slightly increased collagen deformation in the deeper zones, but only with cyclic loading.

CONCLUSION

The findings indicate that, with static loading, significantly increased deformation of articular cartilage collagen structure can occur following meniscectomy, but is minimized by joint motion. This increased deformation may be relevant to the etiology and progression of joint degeneration.

Articular cartilage proteoglycan metabolism in avian degenerative joint disease: effects of strain selection and body weight

The effects of strain selection and body weight on proteoglycan metabolism and the onset of degenerative joint disease (DJD) were investigated in avian articular cartilage. Samples from the hock joint (proximal tarsometatarsus, PTM; distal tibiotarsus, DTT) of rapidly growing broiler fowl, fed either ad libitum or on a restricted-diet, were compared with those from a slow growing, light and non-selected strain (J-line). Synthesis and degradation of proteoglycans were investigated by radioactive pulse-chase studies, determination of total sulphated glycosaminoglycans and electrophoretic analysis. By gross morphology, degenerative changes in articular cartilage occurred solely in the DTT from ad libitum-fed broiler fowl, after 13 weeks. Differences in proteoglycan metabolism were also observed, most markedly in the DTT, where the rate of proteoglycan synthesis in the ad libitum-fed group was less than in age-matched J-line cartilage, and the proportions of both newly synthesised and resident proteoglycans released into the culture medium were greater. Results with the feed-restricted group were intermediate between ad libitum-fed and J-line. Electrophoretic analysis of proteoglycans in the culture media showed evidence of degradation solely in the ad libitum-fed group, with earliest onset in the DTT. The results indicate that proteoglycan metabolism in avian articular cartilage is similar to that in mammalian cartilage during the development of DJD, and that the onset of cartilage degeneration is linked with excessive load bearing.

The role of cytokines as inflammatory mediators in osteoarthritis: lessons from animal models

Studies in animal models of osteoarthritis (OA) have been used extensively to gain insight into the pathogenesis of OA, but early studies largely ignored inflammation except as a secondary phenomenon. Synovitis has often been noted as a feature in experimental OA, and more recent work has established a central role for inflammatory cytokines as biochemical signals which stimulate chondrocytes to release cartilage-degrading proteinases. Thus, proteinase inhibitors, cytokine antagonists and receptor blocking antibodies, and growth/differentiation factors have been considered as potential therapeutic agents and targets for gene therapy. Although there is some disagreement, it is generally accepted that IL-1 is the pivotal cytokine at early and late stages, while TNF-alpha is involved primarily in the onset of arthritis. Other cytokines released during the inflammatory process in the OA joint may be regulatory (IL-6, IL-8) or inhibitory (IL-4, IL-10, IL-13, IFN-gamma). Furthermore, studies in animal models have illustrated the potentially beneficial effects of anticytokine therapy with monoclonal antibodies or receptor antagonists, although local rather than systemic delivery would be necessary for the largely localized OA in humans. Transgenic or knockout mice have also provided insights into general mechanisms of cytokine-induced cartilage degradation but have not directly addressed OA pathogenesis. Similarly, animals with spontaneous or transgenic modifications in cartilage matrix components, growth/differentiation factors, or developmentally regulated transcription factors have provided information about potential gene defects that predispose to OA without addressing the role of inflammatory mediators in cartilage destruction. Although the multiple etiologies of human OA indicate that it is more complex than any animal model, the use of appropriate, well-defined animal models will establish the feasibility of novel forms of therapy.

Simultaneous changes in the mechanical properties, quantitative collagen organization, and proteoglycan concentration of articular cartilage following canine meniscectomy

The mechanical properties and microstructure of articular cartilage from the canine tibial plateau were studied 12 weeks after total medial meniscectomy. The organization of the birefringent collagen network was measured with quantitative polarized light microscopy to determine the thickness and the degree of organization of the superficial and deep zones. The zonal concentration of sulfated glycosaminoglycan was quantified with digital densitometry of safranin-O staining. Equilibrium compressive and shear properties, as well as dynamic shear properties, were measured at sites adjacent to those of microstructural analysis. The results evinced significant loss of cartilage function following meniscectomy, with decreases of 20-50% in the compressive and shear moduli. There was no evidence of alterations in the degree of collagen fibrillar organization, although a complete loss of the surface zone was seen in 60% of the samples that underwent meniscectomy. Meniscectomy resulted in a decreased concentration of sulfated glycosaminoglycan, and significant positive correlations were found between the equilibrium compressive modulus and the glycosaminoglycan content. Furthermore, the shear properties of cartilage correlated directly with collagen fibrillar organization measured at the superficial zone of corresponding sites. These findings demonstrate that meniscectomy leads to impaired mechanical function of articular cartilage, with significant evidence of quantitative correlations between cartilage microstructure and mechanics.

Longitudinal characterization of synovial fluid biomarkers in the canine meniscectomy model of osteoarthritis

Damage to the meniscus can lead to posttraumatic osteoarthritis. Early markers of joint injury and tissue disease may be useful in developing and administering clinical treatment. We investigated the effects of total medial meniscectomy on biomarkers measured serially in synovial lavage fluid each month for 3 months. Following meniscectomy in dogs, four biomarkers were evaluated: cartilage oligomeric matrix protein, keratan sulfate epitope (5D4), the 3B3(-) neoepitope of chondroitin-6-sulfate, and the 3B3(+) chondroitinase-generated epitope of chondroitin-6-sulfate. Meniscectomy led to statistically significant elevations of all four biomarkers, with levels peaking at 4 weeks. By 12 weeks, the level of the 5D4 epitope returned to the preoperative baseline level whereas that of cartilage oligomeric matrix protein, 3B3(-), and 3B3(+) remained above the baseline. Concentrations of these biomarkers in the knees not operated on did not change significantly from the baseline. The levels of cartilage oligomeric matrix protein and 3B3(-) relative to 3B3(+) remained constant in all knees. In contrast, the level of 5D4 relative to 3B3(+) declined over time in the knee operated on but remained constant in the knee not operated on. These results demonstrate a quantitative change in the molecular components of synovial fluid after meniscectomy, as well as a qualitative change evinced by an alteration in the relative proportions of these epitopes. Extensive analyses showed a strong correlation between serum levels of 3B3(-) from the femoral and cephalic veins; however, serum 3B3(-) was not correlated with synovial fluid 3B3(-). These findings support the hypothesis that the concentrations of select cartilage biomarkers in synovial fluid are altered following meniscectomy and are promising tools for objectively monitoring the induction of osteoarthritis in this model system.

The protective effects of meniscal transplantation on cartilage. An experimental study in sheep

BACKGROUND

Meniscal loss may result in arthritis. The aim of this study was to establish a simple operative method for meniscal transplantation in a large-animal model and to determine whether meniscal transplantation provides protection of the articular surfaces, whether meniscal allografts have the same protective effect as meniscal autogenous grafts, and whether there is any rejection phenomenon associated with meniscal allografts.

METHODS

Twenty-eight sheep were divided into four study groups, which were treated with (1) a sham operation (four sheep), (2) a meniscectomy (eight sheep), (3) a meniscal autogenous graft (eight sheep), or (4) a meniscal allograft (eight sheep). The meniscal transplant was secured with three suture anchors to the tibia. At four months after the operation, macroscopic and microscopic evaluations of the articular cartilage and the menisci of the sheep knees were performed in a blinded fashion.

RESULTS

The group treated with the sham operation had no cartilage damage and had normal meniscal tissue. The meniscectomies resulted in significant macroscopic and microscopic damage to the articular cartilage in the medial compartment. The mean score (and standard error of the mean) for macroscopic damage to the cartilage in the group treated with the meniscectomy was 6.5+/-0.8 points compared with 3.9+/-0.7 points in the group treated with the autogenous graft and 4.3+/-0.6 points in the group treated with the allograft (p<0.05). The size of the area of damaged articular cartilage was reduced by approximately 50 percent in both groups treated with a meniscal transplant compared with the group treated with the meniscectomy (p<0.05). There were no significant differences between the group treated with the autogenous graft and that treated with the allograft. The histological appearance of the meniscal autogenous grafts was within normal limits. Interestingly, all of the allografts had evidence of fibrinoid degeneration with areas of hypocellularity and cloning of chondroid cells.

CONCLUSIONS

These results suggest that meniscal transplantation provides noticeable although not complete protection against damage to the articular cartilage after a meniscectomy. The meniscal allografts were just as effective in providing this protection as were the meniscal autogenous grafts.

Articular collagen degradation in the Hulth-Telhag model of osteoarthritis

OBJECTIVE

This study employed immunohistochemistry to investigate the pattern of type II collagen (CII) degradation in an acute injury model of osteoarthritis. It was hypothesized, based on previous studies of primary osteoarthritis (OA), that the worst areas of CII degradation would be located in the superficial and upper middle zones of the articular cartilage, with staining extending into the deep zone as the OA became more severe.

DESIGN

In this model of secondary OA, rabbits were made osteoarthritic by transecting the anterior and posterior cruciate ligaments and removing the meniscus. At various times post surgery, articular cartilage was examined for CII degradation using monoclonal antibody 18:6:D6. This antibody reacts to an epitope that is exposed when CII is degraded as the result of protease cleavage. Proteoglycans (PG) were localized using Safranin-O/Fast Green. Staining intensities were quantitated using image analysis software.

RESULTS

In the joints with surgically induced OA, degradation of CII was seen as early as 3 weeks with the majority of the degradation localized in zones I and III. At 14 weeks the destruction of CII was more pronounced, but there was a surprising lack of degradation in zone II. There were also several other unexpected findings. The sham-operated joints, for example, were intended to serve as controls yet CII degradation was observed in rabbits killed 3 weeks after surgery. It was also expected that greater CII degradation would occur in cartilage from medial condyles, but after 14 weeks there was no significant difference between medial and lateral condyles. Finally, the loss of staining for PG correlated with the degradation of CII except in zone III where limited PG loss was observed.

CONCLUSION

Differences were observed between the pattern of articular cartilage destruction in this model of secondary OA and that of primary OA. Further investigation of the mechanical and biochemical processes underlying the development of both types of OA needs to be conducted.

Nitric oxide production and apoptosis in cells of the meniscus during experimental osteoarthritis

OBJECTIVE

To examine the pathologic changes in meniscus tissue during experimental osteoarthritis (OA) and to determine the relationship between nitric oxide (NO) synthesis, apoptosis, and meniscus degradation.

METHODS

OA was induced in rabbits by anterior cruciate ligament (ACL) transection. Knees were harvested after 9 weeks and assessed for OA severity. Menisci were subjected to histologic, immunohistochemical, and electron microscopic analyses for the presence of nitrotyrosine and apoptosis. Menisci were also cultured for analysis of NO production.

RESULTS

All menisci from joints with ACL transection demonstrated degenerative changes. A high number of apoptotic cells was present in the medial part of menisci, which contains chondrocytic cells. Menisci from nonoperated contralateral knees contained only small numbers of cells in apoptosis. Conditioned media from meniscus cultures contained similarly elevated levels of nitrite as cartilage cultures from the same arthritic knees. Nitrotyrosine immunoreactivity, an indicator of in vivo NO production, was prominent in menisci from knees with ACL transection. In addition, menisci from normal knees produced high levels of NO in response to in vitro stimulation with interleukin-1beta or lipopolysaccharide.

CONCLUSION

These observations suggest that pathologic changes in menisci are a regular feature of experimentally induced OA and are associated with NO production and meniscus cell apoptosis.

Meniscus regeneration in a rabbit partial meniscectomy model

Meniscectomy is known to be associated with osteoarthrosis of the knee. The purpose of this study was to compare the natural and augmented repair of menisci in the knees of New Zealand White rabbits. To create a partial defect in the medial meniscus, we used an experimental model that has been well characterized and extensively used in the study of osteoarthrosis and articular cartilage repair. The defect was left untreated or treated with one of the following: a periosteal autograft, a type I collagen sponge, or the same sponge loaded with autologous, bone marrow-derived, cultured mesenchymal stem cells. The natural repair was always incomplete and degenerative changes within these joints were progressive. The periosteal autograft underwent differentiation into a bone and hyaline cartilage composite that was ineffectual as a meniscus and accelerated the degenerative changes in those joints when compared to natural repair controls. There was evidence of a consistent sequence of events in the transformation of the periosteal grafts to a core of cartilage that underwent endochondral ossification. In the last two groups, the collagen sponge functioned as a scaffold that resulted in more abundant repair tissue. The collagen sponge alone supported a largely fibrous repair process. The cultured mesenchymal stem cells were observed to augment the repair process in some specimens to include fibrocartilage histologically similar to normal meniscus. Degenerative changes were present in both of these groups, which indicates that the biomechanical function of the meniscus was not restored, or an irreversible osteoarthrosis cascade was initiated during the repair period. Based on these preliminary studies, further investigation of cell-based meniscus regeneration appears to be warranted.

Tensile properties of articular cartilage are altered by meniscectomy in a canine model of osteoarthritis

Loss of or damage to the meniscus alters the pattern of loading in the knee joint and frequently leads to cartilage degeneration and osteoarthritis. The mechanical properties of articular cartilage have been shown to reflect the extent of cartilage degeneration in human osteoarthritis and in experimental models of joint disease, but there is little experimental data documenting changes in cartilage mechanics following meniscectomy. We hypothesized that the tensile properties of the surface zone of articular cartilage are altered following total medial meniscectomy. Twelve mongrel dogs underwent complete resection of the medial meniscus in the right knee, and the femoral cartilage was studied 12 weeks after the operation. We performed uniaxial, tensile stress-relaxation tests to determine the equilibrium tensile modulus of surface-zone cartilage. Water and glycosaminoglycan content were also measured at site-matched locations. The tensile moduli of the cartilage decreased significantly following meniscectomy. The linear region modulus decreased by 40%, from 25.5 +/- 7.7 to 15.3 +/- 7.2 MPa. There was a weak (r = -0.45), but significant, correlation between the linear region modulus and the gross morphological grade for cartilage damage. Water and glycosaminoglycan content did not change following meniscectomy. Composition was not correlated with mechanical properties or morphological grade, suggesting that cartilage structure may play a more important role than composition in determining the mechanical properties. The observed decrease in cartilage material properties provides a quantitative measure of the loss of cartilage function following meniscectomy and reflects a pattern of change that is consistent with damage to the collagen-proteoglycan solid network.

In vivo transfer of interleukin-1 receptor antagonist gene in osteoarthritic rabbit knee joints: prevention of osteoarthritis progression

The goal of this study was to determine the efficacy of local IL-1Ra gene therapy by intra-articular plasmid injections on structural changes in the meniscectomy rabbit model of osteoarthritis. A partial meniscectomy of the right knee was performed on the rabbits through a medial parapatellar incision. The rabbits were then divided into four experimental groups. Group 1 received no treatment. Group 2 received three consecutive intra-articular injections at 24-hour intervals of 0.9% saline containing a lipid, gammaAP-DLRIE/DOPE, and a DNA plasmid, VR1012. Group 3 received three consecutive injections of saline containing 1000 microg of canine IL-1Ra plasmid and lipid. The injections were given starting 4 weeks post-surgery. Rabbits from Group 1 were killed 4 weeks post-surgery, and all other rabbits 8 weeks post-surgery. The severity of macroscopic and microscopic changes on cartilage on the medial and femoral condyles and tibial plateaus and synovium were graded separately. Specimens were also processed for immunohistochemical staining using a rabbit polyclonal antibody against canine IL-1Ra. The level of canine IL-1Ra in synovial fluid was determined using enzyme-linked immunosorbent assay. The presence of the DNA plasmid in the synovium was tested by polymerase chain reaction. A significant reduction in the width of osteophytes and size of macroscopic lesions (P < 0.04) was observed, and was dependent on the amount of IL-1Ra plasmid injected. A significant reduction was also noted in the severity of histologic cartilage lesions (P < 0.01) in the group that received the highest dosage (1000 microg) of IL-1Ra plasmid. IL-1Ra was detected in synovial fluid by enzyme-linked immunosorbent assay and by immunohistochemical staining in the synovium and cartilage of rabbits that received injections containing the IL-1Ra plasmid. Polymerase chain reaction analysis of synovial DNA revealed the presence of the cloned cDNA dog IL-1Ra up to 4 weeks after the first intra-articular injection. This study demonstrates that direct in vivo transfer of the IL-1Ra gene into osteoarthritis knee cells using intra-articular injections of a plasmid vector and lipids can significantly reduce the progression of experimental osteoarthritis. This avenue may therefore represent a promising future treatment for osteoarthritis.

Principles of cartilage repair and regeneration

An experimental approach and logic are presented for the regeneration of skeletal tissues that focus on the recapitulation of embryonic events starting with an uncommitted progenitor cell population that the authors refer to as mesenchymal stem cells. The repair and regeneration of articular cartilage, which itself has no repair potential, is the subject of this presentation. Full thickness cartilage defects were created in the medial condyle of the distal femur. Self repair (empty defects), articular chondrocytes (allografts), and autologous mesenchymal stem cells were used and the results are reported in selected examples from more than 800 rabbit knees. The optimal number of the appropriate cells delivered in a supportive vehicle to a defect pretreated with a dilute trypsin solution to optimize the integration of repair with normal host cartilage provides a methodology in which regeneration of articular cartilage can be observed. The principles have relevance to the clinical repair and regeneration of cartilage and other skeletal defects.

Analysis of heat shock proteins and cytokines expressed during early stages of osteoarthritis in a mouse model

OBJECTIVE

Osteoarthritis (OA) is a debilitating disease of the joints. The joints of affected individuals are characterized by a progressive degeneration of articular cartilage leading to inflammation and pain. The expression of heat shock proteins (HSPs) is a ubiquitous self-protective mechanism of all cells under stress, furthermore, the synovium of osteoarthritic individuals contains high levels of cytokines. This study seeks to establish the role of HSPs and cytokines in OA.

METHODS

We have investigated the presence of HSPs and cytokines in articular cartilage during early stages of OA in a mouse that is known to develop spontaneous OA lesions (C57 black mouse). The articular cartilage from closely related mice (C57BL/6) was used as control. Messenger RNAs (mRNAs) for HSPs (HSP32, HSP47, HSP60, HSP70, HSP84 and HSP86) and cytokines [interleukin-1 beta (IL-1 beta), interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-alpha) and interferon-gamma (IFN-gamma)] were detected by reverse transcription-polymerase chain reaction (RT-PCR).

RESULTS

The mRNA levels of HSP47, HSP70, HSP86, IL-6, and IFN-gamma were up-regulated in the cartilage of C57 black mice, whereas, the level of expression of HSP32, HSP60, HSP84 and IL-1 beta remained unchanged. Furthermore, the expression of IL-1 beta, IL-6, TNF-alpha and IFN-gamma mRNA was associated with expression of HSP60, HSP47, HSP70 and HSP70/HSP86 mRNA, respectively.

CONCLUSIONS

The findings in this study suggest that chondrocytes are conditioned under non-physiological stress during early stages of OA, In addition, among HSPs, HSP70 was associated with two different highly expressed cytokines in C57 black mice, indicating the possible role of HSP70 as a characteristic indicator of early stage of OA.

Mono-iodoacetate-induced experimental osteoarthritis: a dose-response study of loss of mobility, morphology, and biochemistry

OBJECTIVE

To characterize the dose-responsiveness of morphologic and biochemical chondral changes relative to mobility in mono-iodoacetate (MIA)-induced osteoarthritis (OA) in rats.

METHODS

Rat mobility was assessed by biotelemetry. Articular lesions were characterized by macroscopic and histologic examinations. Cartilage proteoglycan metabolism was evaluated by the 1,9-dimethylmethylene blue dye binding assay and by radiosulfate incorporation in patellar cartilage.

RESULTS

Spontaneous locomotor activity was rapidly, transiently, and dose-dependently decreased after MIA injection into rat knees (primary response). Thereafter, only high doses (0.3 mg and 3.0 mg) led to a secondary progressive long-term loss of spontaneous mobility on day 15, when subchondral bone was exposed. These 2 doses resulted in significant changes in cartilage proteoglycan concentration at day 15 and a strong inhibition of anabolism in the peripheral patellae by day 2, contrasting with the effects of lower doses (0.01, 0.03, and 0.1 mg).

CONCLUSION

When a sufficient dose of MIA is used, this model can easily and quickly reproduce OA-like lesions and functional impairment in rats, similar to that observed in human disease. These parameters, as well as proteoglycan metabolism, could serve as indicators for studying chondroprotective drugs, or for evaluating the ability of imaging techniques to detect and evaluate chondral lesions.

Temporal pattern of cysteine endopeptidase (cathepsin B) expression in cartilage and synovium from rabbit knees with experimental osteoarthritis: gene expression in chondrocytes in response to interleukin-1 and matrix depletion

OBJECTIVE

To determine the temporal pattern of expression of cathepsin-B in chondrocytes and synovium in experimental osteoarthritis, and to determine possible mechanisms for upregulation and secretion of cathepsin-B from chondrocytes.

METHODS

Experimental osteoarthritis was induced with partial medial meniscectomy (PM); sham operated (SH) and normal (N) rabbits were used as controls. Cathepsin-B mRNA expression was assessed with northern blotting with a 32P labelled cDNA probe. Cathepsin-B was measured in conditioned media or cell extracts using a fluorogenic substrate Z-Arg-Arg-AMC. Chondrocyte monolayers were used to determine cathepsin-B expression in response to interleukin-1 beta (IL-1 beta). Cartilage explants were used to test the effect of matrix depletion on cathepsin-B release.

RESULTS

Chondrocytes obtained from experimental osteoarthritis knees did not show cathepsin-B mRNA upregulation. However, isolated chondrocytes secreted cathepsin-B into the culture medium. Enzyme release was significantly higher at 8 weeks relative to controls, but not at 12 weeks or 4 weeks. Enzyme released from synovium was significantly higher in PM group compared with SH group at 4 and 8 weeks. IL-1 beta was ineffective in upregulating steady state cathepsin-B mRNA in chondrocytes; however, it upregulated the intracellular enzyme, and this was blocked with cycloheximide. Enzymatic depletion of cartilage matrix after exposure of explants to IL-1 resulted in release of significantly higher amounts of cathepsin-B into the medium by matrix depleted chondrocytes compared with intact explants.

CONCLUSIONS

In experimental osteoarthritis, cathepsin-B is upregulated in synovial tissue during the early degenerative phase. Progression of experimental osteoarthritis is accompanied by upregulation of cathepsin-B in cartilage. Cartilage and synovial cathepsin-B levels decline as experimental osteoarthritis advances to more degenerative states. IL-1 upregulates intracellular cathepsin-B by increasing cathepsin-B protein synthesis; it is not an effective stimulus for enzyme secretion. Depletion of cartilage matrix during progression of experimental osteoarthritis may contribute to secretion of cathepsin-B and perpetuation of cartilage destruction.

Characterization of cartilage metabolic response to static and dynamic stress using a mechanical explant test system

A new mechanical explant test system was used to study the metabolic response (via proteoglycan biosynthesis) of mature, weight-bearing canine articular cartilage subjected to static and dynamic compressive stresses. Stresses ranging from 0.5 to 24 MPa were applied sinusoidally at 1 Hz for intervals of 2-24 h. The explants were loaded in unconfined compression and compared to age-matched unloaded explants. Both static and dynamic compressive stress significantly decreased proteoglycan biosynthesis (range 25-85%) for all loading time intervals. The inhibition was proportional to the applied stress but was independent of loading time. After rehydration upon load removal, the measured water content of the loaded explants was not different from the unloaded explants for all test variables. Autoradiographic and electron microscopic analysis of loaded explants showed viable chondrocytes throughout the matrix. Our results suggest that the decreased metabolic response of cyclically loaded explants may be dominated by the static component (RMS) of the dynamic load. Furthermore, the observed decreased metabolism may be more representative of the in situ tissue response than that of unloaded explants, in which we found an increasing rate of metabolism for up to 6 days after explant removal.

Cartilage swelling and loss in a spontaneous model of osteoarthritis visualized by magnetic resonance imaging

The objective of this study was to investigate whether the rate of change in cartilage pathology could be effectively monitored by magnetic resonance imaging (MRI) as part of a longitudinal investigation of an osteoarthritis model in vivo, and to define the minimum requirements necessary to establish disease progression. Magnetic resonance images of the knee of eight male Dunkin-Hartley guinea-pigs were obtained at 8, 12, 18, 24, 30, 36 and 52 weeks of age using a two-dimension spin-echo sequence with a TR of 1500 ms and TE of 40 ms. The total thickness of the femoral and tibial cartilage was measured from those images. Over the same time course, sets of spin-spin relaxation-weighted images were acquired from two additional animals of the same age, from which the T2 relaxation times of water in the articular cartilage were estimated and compared with those of muscle and adipose tissue within the same joint. The cartilage thickness of all the animals increased during the first 6 months, then either stayed thicker (4/8) or became progressively thinner (4/8). Up to 18 weeks of age, the cartilage T2 value was between 23-24 ms but became elevated by 30 weeks and the mean value was more than 40 ms at the end of the study, T2 values for the muscle and adipose tissue remained within the range 30-33 ms, or 47 ms, respectively. We concluded that in this model, cartilage thickness measurements from an magnetic resonance image would not provide a reliable marker to stage osteoarthritis progression partly because the cartilage was so thin in a joint of this size, but also because the changes with time were not linear but biphasic. However, quantitation of the T2 relaxation values may provide a more predictable indicator of cartilage pathology for longitudinal studies because the changes were monotonic and independent of cartilage thickness.

Direct measurement of hoop strains in the intact and torn human medial meniscus

OBJECTIVE: To measure the circumferential or hoop strains generated in the medial meniscus during loading of the knee joint and to examine the effect of longitudinal and radial tears in the meniscus on these strain values. DESIGN: An in vitro investigation measuring the circumferential strains in the medial menisci of cadaveric human knees as they were loaded in a materials testing machine. BACKGROUND: The menisci transmit approximately 50% of the load through the knee, the rest being transmitted by direct contact of the articular cartilage. Damage to the menisci will alter the pattern of load transmission as will meniscectomy. This study examined the changes in the mechanics of the meniscus in situ as a result of simulated tears to assess the effect of its load carrying capacity and the implications of surgery to remove part or all of a damaged meniscus. METHODS: Nineteen human cadaveric knees were tested. Windows were made in the joint capsule and strain gauges inserted into the anterior, middle and posterior sections of the medial meniscus. The knees were then loaded to three times body weight at speeds of 50 and 500 mm/min, with the knee joint at 0 degrees and 30 degrees of flexion. The tests were repeated following the creation of a longitudinal or a radial tear in the meniscus. RESULTS: The intact menisci showed significantly less strain in the posterior section compared to the anterior and middle sections (P < 0.003, with strains of 1.54%, 2.86% and 2.65% respectively). With a longitudinal tear this pattern changed with strains decreasing anteriorly and increasing posteriorly. There were also significant differences at different angles of knee joint flexion not seen in the intact meniscus. 50% radial tears reduced the strains anteriorly whilst a complete radial tear completely defunctioned the meniscus. CONCLUSIONS: This study has shown that there are significantly different hoop strains produced in different sections of the medial meniscus under load and the patterns of strain distribution are disturbed by meniscal tears. RELEVANCE: These results provide important data for mathematical models which must include non-uniform behaviour. They also have implications for the surgical management of torn menisci. Undamaged portions should be preserved and the integrity of the circumferential fibres maintained to ensure the menisci retain a load bearing capability.

Characterization of a model of osteoarthritis in the rabbit knee

A new computerized method of histomorphometry was used to assess the development of osteoarthritis (OA) in a rabbit model. Three groups of 10 New Zealand White rabbits with closed epiphyses underwent unilateral anterior cruciate ligament transection (ACLT) and contralateral arthrotomy (sham). Groups were killed at 4, 8 and 12 weeks. At the time of death the femoral condyles were assessed grossly following the application of India ink using the following grading scale. Grade 1: intact surface; grade 2: minimal fibrillation; grade 3: overt fibrillation; grade 4: erosion. All histological sections were assessed using a color image analysis system. The mean thickness and area were measured for a defined cartilage region. The root mean square surface roughness (based on deviations from an idealized smooth surface) was calculated to assess the surface profile of the articular cartilage. The results were as follows. After ACLT, no full-thickness ulceration was noted at 4 weeks. Four of the medial femoral condyles at 8 weeks and six at 12 weeks showed full-thickness ulceration of the articular cartilage. The per cent cartilage area and cartilage thickness (ACLT divided by sham) in almost all regions showed decreases with time, indicating progressive erosion. The surface of the ACLT knees was much rougher than that of sham of the knees. These results demonstrate the usefulness of a quantitative methodology using a computerized video analysis system to assess the articular cartilage following ACLT in a rabbit model for the development of OA.

Primary osteoarthrosis in guinea pigs: a stereological study

Volumes and surfaces of articular cartilage and subchondral bone of the proximal tibial epiphysis were measured by unbiased stereological methods on the light microscopic level in groups of 6, 12, and 30-month-old (adult, middle-aged, and old) guinea pigs with primary osteoarthrosis. At 12 months, structural changes similar to those of human osteoarthrosis had developed, predominantly on the central medial condyle, which was not covered with meniscus. The lateral condyle was virtually unaffected; this allowed separate analysis of age-related and disease-related changes. Fibrillation and destruction of cartilage was accompanied by a simultaneous increase of the volume of both cartilage (66%) and subchondral bone (50%). The epiphyseal volume increased by 27% at 12 months, predominantly on the medial (osteoarthrotic) condyle, whereas the volume of the lateral condyle increased only in the oldest age group; this indicated that the joint has a potential for growth and remodeling. Joint growth has been suggested as a pathogenic factor in osteoarthrosis. The 65% increase in thickness noted in subchondral bone was a further indication of the importance of proliferative bone changes in early osteoarthrosis. The low variability of osteoarthrosis in this animal model makes it possible to obtain stable quantitative data from relatively small groups of animals.

Regional mitogenic response of the meniscus to platelet-derived growth factor (PDGF-AB)

Since meniscal healing is region-specific, we studied the regional (peripheral compared with central) response of meniscal explants to human, recombinant platelet-derived growth factor-AB. Meniscal explants from the hindlimbs of both knees of mature sheep were sectioned and were cultured with variable doses of human, recombinant platelet-derived growth factor-AB, and incorporation of [3H]-thymidine was measured. The mitogenic response was measured at different times in culture (48 or 96 hours) and by location (lateral or medial). In the absence of the growth factor, the peripheral third of both menisci incorporated 10-fold more [3H]-thymidine on a weight basis than did the central two-thirds. Cellularity was equivalent in the two regions. Doses of less than 100 ng/ml of growth factor produced either no stimulation or a variable response. A dose of 100 ng/ml resulted in consistent, significant (p < 0.05) stimulation in all groups in the peripheral region, and a dose of 200 ng/ml provided more than a 2.5-fold increase. Multiple-factor analysis of variance demonstrated that there were no significant differences between experiments, times in culture, or menisci. The central region did not respond to stimulation with the growth factor at any of the doses tested. These data suggest that regional differences (peripheral compared with central) in responsiveness to human, recombinant platelet-derived growth factor-AB may reflect a different level of signal transduction machinery for growth factor receptors and distinct fibrobchondrocyte populations. These findings are consistent with the variable healing capacity of the meniscal regions in vivo and suggest a pharmacological means to promote the repair of the peripheral meniscal region.

Prostromelysin and procollagenase genes are differentially up-regulated in chondrocytes from the knees of rabbits with experimental osteoarthritis

OBJECTIVE

To determine the relative expressions of matrix metalloprotease (MMP) genes pro-MMP1 and pro-MMP3 in the cartilage of rabbits with experimentally induced osteoarthritis (OA), and to assess the role of the chondrocyte in this process.

METHODS

OA was induced in rabbits after partial medial meniscectomy. Rabbits were killed at 4 weeks or 8 weeks, and total cellular RNA was prepared from cartilage and probed by Northern blotting with pro-MMP 32P-labeled complementary DNA. Monolayer chondrocytes were used to assess MMP-inducing activity of chondrocyte factor(s).

RESULTS

Pro-MMP messenger RNAs (mRNAs) were up-regulated in experimental OA cartilage; pro-MMP3 mRNA expression exceeded that of pro-MMP1. Conditioned medium from OA-derived chondrocytes up-regulated pro-MMP mRNAs in normal chondrocytes.

CONCLUSION

Up-regulation of MMP genes in this OA model may contribute to cartilage degradation. Chondrocytes up-regulate MMP genes via an autocrine pathway.