24R,25-Dihydroxyvitamin D3 Protects against Articular Cartilage Damage following Anterior Cruciate Ligament Transection in Male Rats.

Osteoarthritis (OA) in humans is associated with low circulating 25-hydroxyvitamin D3 [25(OH)D3]. In vitamin D replete rats, radiolabeled 24R,25-dihydroxyvitamin D3 [24R,25(OH)2D3] accumulates in articular cartilage following injection of [3H]-25(OH)D3. Previously, we showed that 24R,25(OH)2D3 blocks chondrocyte apoptosis via phospholipase D and p53, suggesting a role for 24R,25(OH)2D3 in maintaining cartilage health. We examined the ability of 24R,25(OH)2D3 to prevent degenerative changes in articular cartilage in an OA-like environment and the potential mechanisms involved. In vitro, rat articular chondrocytes were treated with IL-1ß with and without 24R,25(OH)2D3 or 1α,25(OH)2D3. 24R,25(OH)2D3 but not 1α,25(OH)2D3 blocked the effects of IL-1ß in a dose-dependent manner, and its effect was partially mediated through the TGF-ß1 signaling pathway. In vivo, unilateral anterior cruciate ligament transections were performed in immunocompetent rats followed by intra-articular injections of 24R,25(OH)2D3 or vehicle (t = 0, 7, 14, 21 days). Tissues were harvested on day 28. Joints treated with vehicle had changes typical of OA whereas joints treated with 24R,25(OH)2D3 had less articular cartilage damage and levels of inflammatory mediators. These results indicate that 24R,25(OH)2D3 protects against OA, and suggest that it may be a therapeutic approach for preventing trauma-induced osteoarthritis.

Characterization of osteoarthritic human knees indicates potential sex differences.

BACKGROUND: The prevalence of osteoarthritis is higher in women than in men in every age group, and overall prevalence increases with advancing age. Sex-specific differences in the properties of osteoarthritic joint tissues may permit the development of sex-specific therapies. Sex hormones regulate cartilage and bone development and homeostasis in a sex-dependent manner. Recent in vitro studies show that the vitamin D3 metabolite 1α,25-dihydroxyvitamin D3 [1α,25(OH)2D3] also has sex-specific effects on musculoskeletal cells, suggesting that vitamin D3 metabolites may play a role in osteoarthritis-related sex-specific differences. The purpose of this study was to determine if sex-specific differences exist in synovial fluid and knee tissues isolated from male and female patients with severe knee osteoarthritis. We determined the presence of vitamin D3 metabolites, inflammatory cytokines, growth factors, and matrix metalloproteinases (MMPs) in synovial fluid and assessed responses of articular chondrocytes and subchondral osteoblasts to 17ß-estradiol, dihydrotestosterone, and 1α,25(OH)2D3. METHODS: Samples from knee joints of 10 Caucasian male and 10 Caucasian female patients with advanced osteoarthritis aged 65 to 75 years were obtained from total knee arthroplasty. Vitamin D metabolites, cytokines, MMPs, and growth factors in the synovial fluid were measured. Primary cultures of chondrocytes were isolated from fibrillated articular cartilage adjacent to osteoarthritis lesions and minimally affected cartilage distal to the lesion. Osteoblasts were isolated from the subchondral bone. Expression of receptors for 17ß-estradiol and 1α,25(OH)2D3 was assessed by real-time PCR. Chondrocytes and osteoblasts were treated with 10(-8) M 17ß-estradiol, dihydrotestosterone, or 1α,25(OH)2D3 and effects on gene expression and protein synthesis determined. RESULTS: Histology of the articular cartilage confirmed advanced osteoarthritis. Sex differences were found in synovial fluid levels of vitamin D metabolites, cytokines, and metalloproteinases as well as in the cellular expression of receptors for 17ß-estradiol and 1α,25(OH)2D3. Male cells were more responsive to 1α,25(OH)2D3 and dihydrotestosterone, whereas 17ß-estradiol-affected female cells. CONCLUSIONS: These results demonstrate that there are underlying sex differences in knee tissues affected by osteoarthritis. Our findings do not address osteoarthritis etiology but have implications for different prevention methods and treatments for men and women. Further research is needed to better understand these sex-based differences.

Hormonal modulation of connective tissue homeostasis and sex differences in risk for osteoarthritis of the knee.

Young female athletes experience a higher incidence of ligament injuries than their male counterparts, females experience a higher incidence of joint hypermobility syndrome (a risk factor for osteoarthritis development), and post-menopausal females experience a higher prevalence of osteoarthritis than age-matched males. These observations indicate that fluctuating sex hormone levels in young females and loss of ovarian sex hormone production due to menopause likely contribute to observed sex differences in knee joint function and risk for loss of function. In studies of osteoarthritis, however, there is a general lack of appreciation for the heterogeneity of hormonal control in both women and men. Progress in this field is limited by the relatively few preclinical osteoarthritis models, and that most of the work with established models uses only male animals. To elucidate sex differences in osteoarthritis, it is important to examine sex hormone mechanisms in cells from knee tissues and the sexual dimorphism in the role of inflammation at the cell, tissue, and organ levels. There is a need to determine if the risk for loss of knee function and integrity in females is restricted to only the knee or if sex-specific changes in other tissues play a role. This paper discusses these gaps in knowledge and suggests remedies.

Addressing the gaps: sex differences in osteoarthritis of the knee.

An introduction to the accompanying three papers.

Mechanical contributors to sex differences in idiopathic knee osteoarthritis.

The occurrence of knee osteoarthritis (OA) increases with age and is more common in women compared with men, especially after the age of 50 years. Recent work suggests that contact stress in the knee cartilage is a significant predictor of the risk for developing knee OA. Significant gaps in knowledge remain, however, as to how changes in musculoskeletal traits disturb the normal mechanical environment of the knee and contribute to sex differences in the initiation and progression of idiopathic knee OA. To illustrate this knowledge deficit, we summarize what is known about the influence of limb alignment, muscle function, and obesity on sex differences in knee OA. Observational data suggest that limb alignment can predict the development of radiographic signs of knee OA, potentially due to increased stresses and strains within the joint. However, these data do not indicate how limb alignment could contribute to sex differences in either the development or worsening of knee OA. Similarly, the strength of the knee extensor muscles is compromised in women who develop radiographic and symptomatic signs of knee OA, but the extent to which the decline in muscle function precedes the development of the disease is uncertain. Even less is known about how changes in muscle function might contribute to the worsening of knee OA. Conversely, obesity is a stronger predictor of developing knee OA symptoms in women than in men. The influence of obesity on developing knee OA symptoms is not associated with deviation in limb alignment, but BMI predicts the worsening of the symptoms only in individuals with neutral and valgus (knock-kneed) knees. It is more likely, however, that obesity modulates OA through a combination of systemic effects, particularly an increase in inflammatory cytokines, and mechanical factors within the joint. The absence of strong associations of these surrogate measures of the mechanical environment in the knee joint with sex differences in the development and progression of knee OA suggests that a more multifactorial and integrative approach in the study of this disease is needed. We identify gaps in knowledge related to mechanical influences on the sex differences in knee OA.

Neural and psychosocial contributions to sex differences in knee osteoarthritic pain.

People with osteoarthritis (OA) can have significant pain that interferes with function and quality of life. Women with knee OA have greater pain and greater reductions in function and quality of life than men. In many cases, OA pain is directly related to sensitization and activation of nociceptors in the injured joint and correlates with the degree of joint effusion and synovial thickening. In some patients, however, the pain does not match the degree of injury and continues after removal of the nociceptors with a total joint replacement. Growth of new nociceptors, activation of nociceptors in the subchondral bone exposed after cartilage degradation, and nociceptors innervating synovium sensitized by inflammatory mediators could all augment the peripheral input to the central nervous system and result in pain. Enhanced central excitability and reduced central inhibition could lead to prolonged and enhanced pain that does not directly match the degree of injury. Psychosocial variables can influence pain and contribute to pain variability. This review explores the neural and psychosocial factors that contribute to knee OA pain with an emphasis on differences between the sexes and gaps in knowledge.

Effect of light-emitting diode (LED) therapy on the development of osteoarthritis (OA) in a rabbit model.

OBJECTIVE: The objective of this study was to evaluate whether light-emitting diodes (LEDs) could be effective in a noninvasive, therapeutic device for the treatment of osteoarthritic (OA) knee joints. DESIGN: Five weeks following the anterior cruciate ligament transection (ACLT) of mature New Zealand White rabbits, the animal knees were exposed to LED stimulation at intervals of 10 min/day, 5 days/week for 5 weeks in the experimental group (n=7). The device used high intensity red and infrared (IR) LEDs with a total amount of energy delivered to the skin of 2.4 J/cm(2). Animals were sacrificed at 9 weeks postoperatively. Femoral surface gross morphology was evaluated with a modified Outerbridge classification and mRNA expression of catabolic and anabolic markers from femoral condyle cartilage and synovial tissue was assessed using RT-PCR. A control group was harvested 9 weeks following untreated ACLT. RESULTS: Gross morphometry of the control group showed four Grade II, two Grade III and one Grade IV (average 2.6) condyles macroscopically. The experimental group showed two Grade I and five Grade II (average 1.7) (Table 1). mRNA expression of aggrecan in the cartilage showed no difference between the groups, however type II collagen expression increased in the experimental group compared with control. TNF-α expression was significantly decreased in the experimental group compared to control. CONCLUSIONS: There was general preservation of the articular surface and decreased levels of inflammation in the osteoarthritic joints with the application of LED therapy. This may provide potential application as a noninvasive treatment.

Topographic Patterns of Cartilage Lesions in Knee Osteoarthritis.

OBJECTIVE: Treatments for articular cartilage lesions could benefit from characterization of lesion patterns and their progression to end-stage osteoarthritis. The objective of this study was to identify, quantitatively, topographic patterns of cartilage lesions in the human knee. DESIGN: Photographs were taken of 127 unilateral distal femora (from 109 cadavers and 18 arthroplasty remnants) with full-thickness cartilage lesions. Using digital image analysis, the lesions were localized and normalized lesion size was determined for the patellofemoral groove (PFG) and the lateral and medial femoral condyles (LFC, MFC). Samples were classified into patterns using cluster analysis of the lesion size at each compartment. For each pattern, maps showing the extent and frequency of lesions were created. RESULTS: Four main patterns (a-d) were identified (each p<0.001), with the lesion size varying from small (a) to large in distinct regions (b-d). Pattern b had a predominant lesion (23% area) in the MFC, and smaller (<3%) lesions elsewhere. Pattern c had predominant lesions in the LFC (19%) and MFC (10%). Pattern d had a predominant lesion in the PFG (15%) and smaller lesions in the MFC (6%) and LFC (2%). The sub-patterns of a (a1, a2, a3) had relatively small lesions, with similarity between a2 and b, and a3 and d. CONCLUSION: The present methods facilitated quantitative identification of distinct topographic patterns of full-thickness cartilage lesions, based on lesion size and location. These results have implications for stratifying OA patients using precise quantitative methods and, with additional longitudinal data, targeting cartilage treatments.

Variation of mesenchymal cells in polylactic acid scaffold in an osteochondral repair model.

OBJECTIVE: To achieve osteochondral regeneration utilizing transplantation of cartilage-lineage cells and adequate scaffolds, it is essential to characterize the behavior of transplanted cells in the repair process. The objectives of this study were to elucidate the survival of mesenchymal cells (MCs). In a polylactic acid (PLA) scaffold and assess the possibility of MC/PLA constructs for osteochondral repair. DESIGN: Bone marrow from mature male rabbits was cultured for 2 weeks, and fibroblast-like MCs, which contain mesenchymal stem cells (MSCs), were obtained. A cell/scaffold construct was prepared with one million MCs and a biodegradable PLA core using a rotator device. One week after culturing, the construct was transplanted into an osteochondral defect in the medial femoral condyle of female rabbits and the healing process examined histologically. To examine the survivability of transplanted MCs, the male-derived sex-determining region Y (SRY) gene was assessed as a marker of MCs in the defect by polymerase chain reaction (PCR). RESULTS: In the groups of defects without any treatment, and the transplantation of PLA without cells, the defects were not repaired with hyaline cartilage. The cartilaginous matrix by safranin O staining and type II collagen by immunohistochemical staining were recognized, however the PLA matrix was still present in the defects at 24 weeks after transplantation of the construct. During the time passage, transplanted MCs numbers decreased from 7.8 x 105 at 1 week, to 3.5 x 105 at 4 weeks, and to 3.8 x 104 at 12 weeks. Transplanted MCs were not detectable at 24 weeks. CONCLUSIONS: MCs contribute to the osteochondral repair expressing the cartilaginous matrix, however the number of MCs were decreasing with time (i.e. 24 weeks). These results could be essential for achieving cartilage regeneration by cell transplantation strategies with growth factors and/or gene therapy.

Failure analysis of a ceramic bearing acetabular component.

BACKGROUND: Alternative bearings have been explored in an attempt to improve the longevity of total hip prostheses. A Food and Drug Administration (FDA)-approved clinical study of a nonmodular acetabular component consisting of a porous metal shell, compression-molded polyethylene, and a ceramic liner inlay was discontinued following reports of early failures. METHODS: Between October 1999 and January 2003, 429 patients were enrolled in a prospective study to evaluate a cementless ceramic-on-ceramic total hip arthroplasty design (Hedrocel ceramic bearing cup; Implex, Allendale, New Jersey). Two hundred and eighty-two patients (315 hips) were treated with the experimental acetabular implant and 147 patients (157 hips) were treated with an acetabular implant that consisted of the same porous shell but an allpolyethylene liner. Clinical data including a Harris hip score and responses to the Short Form-12 (SF-12) health survey were collected preoperatively and at twelve and twenty-four months postoperatively. Serial radiographs were made preoperatively; at six weeks, three months, six months, and twelve months postoperatively; and annually thereafter. Retrieval analysis was performed on all failed explanted components. Failure was defined as fracture or displacement of the ceramic liner out of the acetabular component. In addition, biomechanical testing was performed on unimplanted acetabular components and mechanically altered cups in an effort to recreate the mechanisms of failure. Finite element analysis was used to estimate stress and strain within the ceramic liner under extreme physiologic loading conditions. RESULTS: The ceramic liner failed in fourteen of the 315 experimental acetabular components; all of the failures were at the ceramic-polyethylene interface. Patients with a body weight of >91 kg had a 4.76 times greater odds of the ceramic liner failing than those who weighed < or =91 kg. Retrieval analysis demonstrated stripe and rim wear with evidence of adhesive wear, indicating a potentially high-friction interaction at the articulation. Finite element analysis demonstrated that the forces on the ceramic liner in cups subjected to extreme loading conditions were insufficient to cause fracture. Biomechanical testing was unable to reproduce an initial ceramic liner displacement in vitro; however, when the ceramic liner was forcibly displaced prior to biomechanical testing, complete displacement and eventual fracture of the ceramic liner resulted. CONCLUSIONS: We hypothesized that the combination of a high patient body weight, an extensive range of motion, and subluxation of the femoral head led to high friction at the articulation between the femoral head and the rim of the liner, which initiated displacement of the ceramic liner. Subsequent normal gait led to further displacement of the liner in all of the fourteen failed components and eventually to ceramic fracture in twelve of the fourteen components.

Pseudoseptic reactions to hylan viscosupplementation: diagnosis and treatment.

Hyaluronans are used widely in the treatment of osteoarthritis of the knee. Three commercial hyaluronan preparations currently are available in the United States: sodium hyaluronate (Hyalgan), sodium hyaluronate (Supartz), and hylan G-F 20 (Synvisc). Although the sodium hyaluronates are derived naturally, hylan is chemically modified to increase its molecular weight. All three products have been shown to be well tolerated in clinical trials, however, there have been reports in the literature of pseudoseptic reactions, or severe acute inflammatory reactions, after injections with hylan. Our study reviewed the reported incidence of pseudosepsis. The pathogenic mechanisms and clinical treatment of this reaction are presented.

Indentation testing of human cartilage: sensitivity to articular surface degeneration.

OBJECTIVE: To determine, for clinical indentation testing of human articular cartilage, the effects of aging and degeneration on indentation stiffness and traditional indices of cartilage degeneration; the relationship between indentation stiffness and indices of degeneration; and the sensitivity and specificity of indentation stiffness to cartilage degeneration. METHODS: Osteochondral cores from femoral condyles of cadaveric human donors were harvested. Samples were distributed into experimental groups based on donor age (young [20-39 years], middle [40-59 years], and old [>/=60 years]), and a macroscopic articular surface appearance that was either normal or mildly degenerate, without deep erosion. Samples were analyzed for indentation stiffness, cartilage thickness, India ink staining (quantitated as the reflected light score), and Mankin-Shapiro histopathology score. RESULTS: Indentation stiffness, India ink staining, and the histopathology score each varied markedly between normal-sample and degenerate-sample groups but varied relatively little between normal samples obtained from different age groups. A decrease in indentation stiffness (softening) correlated with a decrease in the reflectance score and an increase in the overall histopathology score, especially the surface irregularity component of the histopathology score. Receiver operating characteristic analysis suggested that the indentation testing could accurately detect cartilage degeneration as indicated by macroscopic appearance, India ink staining, and histopathology score. CONCLUSION: The indentation stiffness of the normal to mildly degenerate samples tested in this study was sensitive to mild degeneration at the articular surface and was insensitive to changes associated with normal aging or to slight variations in cartilage thickness. This suggests that indentation testing may be a useful clinical tool for the evaluation of early-stage degenerative changes in articular cartilage.

Adhesion of perichondrial cells to a polylactic acid scaffold.

The number of chondrogenic cells available locally is an important factor in the repair process for cartilage defects. Previous studies demonstrated that the number of transplanted rabbit perichondrial cells (PC) remaining in a cartilage defect in vivo, after being carried into the site in a polylactic acid (PLA) scaffold, declined markedly within two days. This study examined the ability of in vitro culture of PC/PLA constructs to enhance subsequent biomechanical stability of the cells and the matrix content in an in vitro screening assay. PC/PLA constructs were analyzed after 1 h, 1 and 2 weeks of culture. The biomechanical adherence of PC to the PLA scaffold was tested by subjecting the PC/PLA constructs to a range of flow velocities (0.25-25 mm/s), spanning the range estimated to occur under conditions of construct insertion in vivo. The adhesion of PC to the PLA carrier was increased significantly by 1 and 2 weeks of incubation, with 25 mm/s flow causing a 57% detachment of cells after 1 h of seeding, but only 7% and 16% after 1 and 2 weeks of culture, respectively (p<0.001). This adherence was associated with marked deposition of glycosaminoglycan and collagen. These findings suggest that pre-incubation of PC-laden PLA scaffolds markedly enhances the stability of the indwelling cells.

Effect of gravity on localization of chondrocytes implanted in cartilage defects.

The transplantation of autologous chondrocytes under a periosteal flap has been used to treat focal cartilage defects. Results have been promising but occasionally involve complications ranging from graft hypertrophy to detachment. The objective of this study was to determine if gravitational forces affect the uniformity of cell distribution within the defect. Using an ex vivo bovine model, the orientation relative to gravity of a repaired full-thickness articular cartilage defect was found to affect the initial distribution of transplanted chondrocytes, prelabeled with 3H-thymidine. After 4 hours, the injected cells (3H-radioactivity) were primarily at the base of the defect (79%) in samples oriented in the up position, primarily at the dependent semicylindrical half of the defect (83%) in samples oriented to the side, and primarily at the periosteal top of the defect (78%) in samples oriented upside-down. Subsequently, the cell distribution remained unchanged after reorientation into other positions. These results indicate that injected chondrocytes localize under the influence of gravity within the initial few hours after injection. Therefore, the defect orientation during this time can be an important factor in the uniformity of cell distribution in the autologous chondrocyte implantation procedure and may be an important determinant of the ultimate clinical outcome.