Cartilage and subchondral bone interaction in osteoarthrosis of human knee joint: a histological and histomorphometric study

Mechanical and structural properties of articular cartilage and subchondral bone in human osteoarthritic knees

Knee osteoarthritis (OA), characterized by multiple joint tissue degenerations, remains a significant clinical challenge. Recent evidence suggests that crosstalk within the osteochondral unit may drive OA progression. Although structural-biomechanical properties of bone and cartilage have been studied, potential interaction within the osteochondral unit in the context of OA has yet to be investigated. We performed comprehensive structural and biomechanical quantification of the cartilage, subchondral bone plate (SBP), and subchondral trabecular bone (STB) using 101 osteochondral cores collected from tibial plateaus of 12 control human cadavers (CT, 5 male/7 female) and 19 patients undergoing total knee replacement (OA, 6 male/13 female). For each sample, we quantified SBP microstructure, plate-and-rod morphological properties of the STB using individual trabecula segmentation, and morphological and compositional properties of the articular cartilage. We also performed indentation testing on each compartment of the osteochondral unit to extract the respective structural-mechanical properties. Cartilage thickness was lower in moderate and severe OA regions, while Osteoarthritis Research Society International score was higher only in severe OA regions. GAG content did not change in any OA region. Aggregate and shear moduli were lower only in severe OA regions, while permeability was lower only in moderate OA regions. In the SBP, thickness and tissue mineral density were higher in moderate and severe OA regions. Tissue modulus of STB was lower in moderate OA regions despite a thicker and more mineralized SBP; this deterioration was not observed in severe OA regions. Regression analysis revealed strong correlations between cartilage and STB properties in CT; these correlations were also found in moderate OA regions but were not observed in severe OA regions. In summary, our findings comprehensively characterize the human OA osteochondral unit. Importantly, uncoupling cartilage and subchondral bone structural-mechanical properties may be a hallmark of OA.

Strategies for Cartilage Repair in Osteoarthritis Based on Diverse Mesenchymal Stem Cells-Derived Extracellular Vesicles

Osteoarthritis (OA) causes disability and significant economic and social burden. Cartilage injury is one of the main pathological features of OA, and is often manifested by excessive chondrocyte death, inflammatory response, abnormal bone metabolism, imbalance of extracellular matrix (ECM) metabolism, and abnormal vascular or nerve growth. Regrettably, due to the avascular nature of cartilage, its capacity to repair is notably limited. Mesenchymal stem cells-derived extracellular vesicles (MSCs-EVs) play a pivotal role in intercellular communication, presenting promising potential not only as early diagnostic biomarkers in OA but also as efficacious therapeutic strategy. MSCs-EVs were confirmed to play a therapeutic role in the pathological process of cartilage injury mentioned above. This paper comprehensively provides the functions and mechanisms of MSCs-EVs in cartilage repair.

Early zoledronate treatment inhibits subchondral bone microstructural changes in skeletally-mature, ACL-transected canine knees

Anterior cruciate ligament (ACL) tear leads to post-traumatic osteoarthritis (PTOA), a significant clinical burden worldwide that currently has no cure. Recent studies suggest a role of subchondral bone adaptations in the development of PTOA. Particularly, microstructural changes in the rod-and-plate microstructure of subchondral bone may precede and contribute to OA progression. In this study, we quantified microstructural changes in subchondral trabecular rods and plates after ACL-transection for the first time in the well-established preclinical canine model of PTOA and investigated the therapeutic potentials of a bisphosphonate (zoledronate) and NSAID treatment (meloxicam). Unilateral hindlimb ACL transection was performed on skeletally-mature (2-year-old, N = 20) and juvenile (10-month-old, N = 20) male beagles. Animals were assigned to 4 groups (N = 5): ACLT, un-operated control, ACLT with zoledronate, and ACLT with meloxicam treatment. Subchondral bone microstructure was evaluated by micro-computed tomography and cartilage integrity was evaluated histologically. We found that ACL-induced subchondral bone changes depended on skeletal maturity of animals. In mature animals, significant loss of trabecular plates that resulted in reduced PR ratio occurred at Month 1 and persisted until Month 8. Zoledronate treatment prevented trabecular plate loss while meloxicam treatment did not. Whether cartilage degeneration is also attenuated warrants further investigation. In juvenile animals that have not reached skeletal maturity, transient changes in trabecular plate and rod microstructure occurred at Month 3 but not Month 9. Neither zoledronate nor meloxicam treatment attenuated bone microstructural changes or cartilage damages. Findings from this study suggest that early inhibition of bone resorption by bisphosphonate after injury may be a promising therapeutic approach to prevent alterations in subchondral bone microstructure associated with PTOA. Our results further demonstrate that pathogenesis of PTOA may differ between adolescent and adult patients and therefore require distinct management strategies.

Osthole Suppresses Knee Osteoarthritis Development by Enhancing Autophagy Activated via the AMPK/ULK1 Pathway

Knee osteoarthritis (KOA) is an increasingly prevalent heterogeneous disease characterized by cartilage erosion and inflammation. As the main chemical constituent of Angelicae Pubescentis Radix (APR), an anti-inflammatory herbal medicine, the potential biological effects and underlying mechanism of osthole on chondrocytes and KOA progression remain elusive. In this study, the potential effect and mechanism of osthole on KOA were investigated in vitro and in vivo. We found that osthole inhibited IL-1β-induced apoptosis and cartilage matrix degeneration by activating autophagy in rat chondrocytes. In addition, osthole could activate autophagy through phosphorylation of AMPK/ULK1, and AMPK serves as a positive upstream regulator of ULK1. Furthermore, KOA rats treated with osthole showed phosphorylation of the AMPK/ULK1 pathway and autophagy activation, as well as cartilage protection. Collectively, the AMPK/ULK1 signaling pathway can be activated by osthole to enhance autophagy, thereby suppressing KOA development. Osthole may be a novel and effective therapeutic agent for the clinical treatment of KOA.

Hip osteoarthritis: A novel network analysis of subchondral trabecular bone structures

Hip osteoarthritis (HOA) is a degenerative joint disease that leads to the progressive destruction of subchondral bone and cartilage at the hip joint. Development of effective treatments for HOA remains an open problem, primarily due to the lack of knowledge of its pathogenesis and a typically late-stage diagnosis. We describe a novel network analysis methodology for microcomputed tomography (micro-CT) images of human trabecular bone. We explored differences between the trabecular bone microstructure of femoral heads with and without HOA. Large-scale automated extraction of the network formed by trabecular bone revealed significant network properties not previously reported for bone. Profound differences were discovered, particularly in the proximal third of the femoral head, where HOA networks demonstrated elevated numbers of edges, vertices, and graph components. When further differentiating healthy joint and HOA networks, the latter showed fewer small-world network properties, due to decreased clustering coefficient and increased characteristic path length. Furthermore, we found that HOA networks had reduced length of edges, indicating the formation of compressed trabecular structures. In order to assess our network approach, we developed a deep learning model for classifying HOA and control cases, and we fed it with two separate inputs: (i) micro-CT images of the trabecular bone, and (ii) the network extracted from them. The model with plain micro-CT images achieves 74.6% overall accuracy while the trained model with extracted networks attains 96.5% accuracy. We anticipate our findings to be a starting point for a novel description of bone microstructure in HOA, by considering the phenomenon from a graph theory viewpoint.

Knee Cartilage and Subchondral Bone Evaluations by Magnetic Resonance Imaging Correlate with Histological Biomarkers in an Osteoarthritis Rabbit Model

OBJECTIVE

To evaluate pathological changes in cartilage and subchondral bone MRI biomarkers in a rabbit model of osteoarthritis (OA) and correlate these with histological variations.

DESIGN

Transection of the anterior cruciate ligament was performed on the right knee of eighteen 12-week-old New Zealand white rabbits to induce OA. 3-Tesla MR images were obtained from 18 healthy control knees (left) and 18 knees with OA (right). Imaging biomarkers included volume, thickness, T1 and T2* cartilage parametric maps, and several subchondral bone features: bone volume to total volume ratio, trabecular thickness, trabecular spacing, trabecular number (TbN), 2D and 3D fractal dimensions, and quality of trabecular score (QTS). Microscopic analysis of the lateral femoral condyles was set as the ground truth.

RESULTS

When healthy and osteoarthritic knees were compared, significant differences were seen in the T1 and T2* values of the femur and tibia cartilage and in the subchondral bone volume to total volume, TbN, and QTS of both the lateral and medial aspects of the femur and tibia. Histological findings revealed significant osteoarthritic changes between healthy and osteoarthritic knees in stain, structure, chondrocyte density, total score, and subchondral bone biomarker levels. A positive correlation was found between histological staining, structure, chondrocyte density, and total score variables in T1 and T2* cartilage biomarkers. A negative correlation was observed between histological subchondral bone variables and magnetic resonance D2D and QTS biomarkers.

CONCLUSION

Quantification of several cartilage and subchondral bone imaging biomarkers in a rabbit model of OA allows the detection of significant changes, which are correlated with histological findings.

Improved Joint Health Following Oral Administration of Glycosaminoglycans with Native Type II Collagen in a Rabbit Model of Osteoarthritis

Simple Summary

Osteoarthritis is an incurable chronic disease. For this reason, new therapies are constantly emerging to improve clinical signs and the quality of life of our pets. Chondroitin sulfate, glucosamine and hyaluronic acid have been proven effective and are the most widely used in many formulations. In the present study, adding native type II collagen to the combination of chondroitin sulfate, glucosamine and hyaluronic acid showed improvements on osteoarthritis progression in an experimental model of osteoarthritis induced by transection of the cranial cruciate ligament of the knee in New Zealand white rabbits. Disease progression was monitored at different time points using magnetic resonance imaging biomarkers, measurement of hyaluronic acid in synovial fluid, and macroscopic and microscopic evaluations of cartilage, synovial membrane and subchondral bone. Overall, our results showed that adding native type II collagen to a combination of glycosaminoglycans allows a significantly slower osteoarthritis progression, compared to glycosaminoglycans alone.

Abstract

A prospective, experimental, randomized, double blinded study was designed to evaluate the effects of glycosaminoglycans, with or without native type II collagen (NC), in an osteoarthritis model induced by cranial cruciate ligament transection. The following compounds were tested: chondroitin sulfate (CS), glucosamine hydrochloride (GlHCl), hyaluronic acid (HA) and NC. Fifty-four female 12-week-old New Zealand rabbits were classified into three groups: CTR (control–no treatment), CGH (CS + GlHCl + HA) and CGH-NC (CS + GlHCl + HA + NC). Each group was subdivided into three subgroups according to survival times of 24, 56 and 84 days. Over time, all rabbits developed degenerative changes associated with osteoarthritis. CGH-NC showed significantly improved values on macroscopic evaluation, compared to CTR and CGH. Microscopically, significantly better results were seen with CGH and CGH-NC, compared to CTR, and synovial membrane values were significantly better with CGH-NC compared to CGH. A significant improvement in magnetic resonance imaging biomarkers was also observed with CGH-NC in cartilage transversal relaxation time (T2) and subchondral bone D2D fractal dimension in the lateral condyle. In conclusion, our results show beneficial effects on joint health of CGH and CGH-NC and also supports that adding NC to CGH results in even greater efficacy.

Standardized Histomorphometric Evaluation of Osteoarthritis in a Surgical Mouse Model

One of the most prevalent joint disorders in the United States, osteoarthritis (OA) is characterized by progressive degeneration of articular cartilage, primarily in the hip and knee joints, which results in significant impacts on patient mobility and quality of life. To date, there are no existing curative therapies for OA able to slow down or inhibit cartilage degeneration. Presently, there is an extensive body of ongoing research to understand OA pathology and discover novel therapeutic approaches or agents that can efficiently slow down, stop, or even reverse OA. Thus, it is crucial to have a quantitative and reproducible approach to accurately evaluate OA-associated pathological changes in the joint cartilage, synovium, and subchondral bone. Currently, OA severity and progression are primarily assessed using the Osteoarthritis Research Society International (OARSI) or Mankin scoring systems. In spite of the importance of these scoring systems, they are semiquantitative and can be influenced by user subjectivity. More importantly, they fail to accurately evaluate subtle, yet important, changes in the cartilage during the early disease states or early treatment phases. The protocol we describe here uses a computerized and semiautomated histomorphometric software system to establish a standardized, rigorous, and reproducible quantitative methodology for the evaluation of joint changes in OA. This protocol presents a powerful addition to the existing systems and allows for more efficient detection of pathological changes in the joint.

Bone marrow lesions in knee osteoarthritis: regional differences in tibial subchondral bone microstructure and their association with cartilage degeneration

OBJECTIVE

The aim of this study was to investigate how bone microstructure within bone marrow lesions (BMLs) relates to the bone and cartilage across the whole human tibial plateau.

DESIGN

Thirty-two tibial plateaus from patients with osteoarthritis (OA) at total knee arthroplasty and eleven age-matched non-OA controls, were scanned ex vivo by MRI to identify BMLs and by micro CT to quantitate the subchondral (plate and trabecular) bone microstructure. For cartilage evaluation, specimens were processed histologically.

RESULTS

BMLs were detected in 75% of the OA samples (OA-BML), located predominantly in the anterior-medial (AM) region. In contrast to non-OA control and OA-no BML, in OA-BML differences in microstructure were significantly more evident between subregions. In OA-BML, the AM region contained the most prominent structural alterations. Between-group comparisons showed that the AM region of the OA-BML group had significantly higher histological degeneration (OARSI grade) (P < .0001, P < .05), thicker subchondral plate (P < .05, P < .05), trabeculae that are more anisotropic (P < .0001, P < .05), well connected (P < .05, P = n.s), and more plate-like (P < 0.05, P < 0.05), compared to controls and OA-no BML at this site. Compared to controls, OA-no BML had significantly higher OARSI grade (P < .0001), and lower trabecular number (P < .05).

CONCLUSION

In established knee OA, both the extent of cartilage damage and microstructural degeneration of the subchondral bone were dependent on the presence of a BML. In OA-no BML, bone microstructural alterations are consistent with a bone attrition phase of the disease. Thus, the use of BMLs as MRI image-based biomarkers appear to inform on the degenerative state within the osteochondral unit.

Spatially matching morphometric assessment of cartilage and subchondral bone in osteoarthritic human knee joint with micro-computed tomography

OBJECTIVE

The objective of this study was to develop a reproducible and semi-automatic method based on micro computed tomography (microCT) to analyze cartilage and bone morphology of human osteoarthritic knee joints in spatially matching regions of interest.

MATERIALS AND METHODS

Tibial plateaus from randomly selected patients with advanced osteoarthritis (OA) who underwent total knee arthroplasty surgery were microCT scanned once fresh and once after staining with Hexabrix. The articular surface was determined manually in the first scan. Total articular surface, defect surface and cartilage surface were computed by triangulation of the cartilage surface and the spatially corresponding subchondral bone regions were automatically generated and the standard cortical bone and trabecular bone morphometric indices were computed.

RESULTS

The method to identify cartilage surface and defects was successfully validated against photographic examinations. The microCT measurements of the cartilage defect were also verified by conventional histopathology using safranin O-stained sections. Cartilage thickness and volume was significantly lower for OA condyle compared with healthy condyle. Bone fraction, bone tissue mineral density, cortical density and trabecular thickness differed significantly depending on the level of cartilage damage.

CONCLUSION

This new microCT imaging workflow can be used for reproducible quantitative evaluation of articular cartilage damage and the associated changes in subchondral bone morphology in osteoarthritic joints with a relatively high throughput compared to manual contouring. This methodology can be applied to gain better understanding of the OA disease progress in large cohorts.

Systematic mapping of the subchondral bone 3D microarchitecture in the human tibial plateau: Variations with joint alignment

Tibial subchondral bone plays an important role in knee osteoarthritis (OA). Microarchitectural characterization of subchondral bone plate (SBP), underlying subchondral trabecular bone (STB) and relationships between these compartments, however, is limited. The aim of this study was to characterize the spatial distribution of SBP thickness, SBP porosity and STB microarchitecture, and relationships among them, in OA tibiae of varying joint alignment. Twenty-five tibial plateaus from end-stage knee-OA patients, with varus (n = 17) or non-varus (n = 8) alignment were micro-CT scanned (17 μm/voxel). SBP and STB microarchitecture was quantified via a systematic mapping in 22 volumes of interest per knee (11 medial, 11 lateral). Significant within-condylar and between-condylar (medial vs. lateral) differences (p < 0.05) were found. In varus, STB bone volume fraction (BV/TV) was consistently high throughout the medial condyle, whereas in non-varus, medially, it was more heterogeneously distributed. Regions of high SBP thickness were co-located with regions of high STB BV/TV underneath. In varus, BV/TV was significantly higher medially than laterally, however, not so in non-varus. Moreover, region-specific significant associations between the SBP thickness and SBP porosity and the underlying STB microarchitecture were detected, which in general were not captured when considering the values averaged for each condyle. As subchondral bone changes reflect responses to local mechanical and biochemical factors within the joint, our results suggest that joint alignment influences both the medial-to-lateral and the within-condyle distribution of force across the tibia, generating corresponding local bony responses (adaptation) of both the subchondral bone plate and underlying subchondral trabecular bone microarchitecture. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1927-1941, 2017.

T2 MR imaging vs. computational modeling of human articular cartilage tissue functionality

The detection of early stages of cartilage degeneration remains diagnostically challenging. One promising non-invasive approach is to functionally assess the tissue response to loading by serial magnetic resonance (MR) imaging in terms of T2 mapping under simultaneous mechanical loading. As yet, however, it is not clear which cartilage component contributes to the tissue functionality as assessed by quantitative T2 mapping. To this end, quantitative T2 maps of histologically intact cartilage samples (n=8) were generated using a clinical 3.0-T MR imaging system. Using displacement-controlled quasi-static indentation loading, serial T2 mapping was performed at three defined strain levels and loading-induced relative changes were determined in distinct regions-of-interest. Samples underwent conventional biomechanical testing (by unconfined compression) as well as histological assessment (by Mankin scoring) for reference purposes. Moreover, an anisotropic hyperelastic constitutive model of cartilage was implemented into a finite element (FE) code for cross-referencing. In efforts to simulate the evolution of compositional and structural intra-tissue changes under quasi-static loading, the indentation-induced changes in quantitative T2 maps were referenced to underlying changes in cartilage composition and structure. These changes were parameterized as cartilage fluid, proteoglycan and collagen content as well as collagen orientation. On a pixel-wise basis, each individual component correlation with T2 relaxation times was determined by Spearman's ρ_s and significant correlations were found between T2 relaxation times and all four tissue parameters for all indentation strain levels. Thus, the biological changes in functional MR Imaging parameters such as T2 can further be characterized to strengthen the scientific basis of functional MRI techniques with regards to their perspective clinical applications.

Association between subchondral bone structure and osteoarthritis histopathological grade

Despite increasing evidence that subchondral bone contributes to osteoarthritis (OA) pathogenesis, little is known about local changes in bone structure compared to cartilage degeneration. This study linked structural adaptation of subchondral bone with histological OA grade. Twenty-five osteochondral samples of macroscopically different degeneration were prepared from tibiae of 14 patients. Samples were scanned with micro-computed tomography (μCT) and both conventional structural parameters and novel 3D parameters based on local patterns were analyzed from the subchondral plate and trabecular bone. Subsequently, samples were processed for histology and evaluated for OARSI grade. Each bone parameter and OARSI grade was compared to assess structural adaptation of bone with OA severity. In addition, thicknesses of cartilage, calcified cartilage, and subchondral plate were analyzed from histological sections and compared with subchondral bone plate thickness from μCT. With increasing OARSI grade, the subchondral plate became thicker along with decreased specific bone surface, while there was no change in tissue mineral density. Histological analysis showed that subchondral plate thickness from μCT also includes calcified cartilage. Entropy of local patterns increased with OA severity, reflecting higher tissue heterogeneity. In the trabecular compartment, bone volume fraction and both trabecular thickness and number increased with OARSI grade while trabecular separation and structure model index decreased. Also, elevation of local patterns became longitudinal in the subchondral plate and axial transverse in trabecular bone with increasing OARSI grade. This study demonstrates the possibility of radiological assessment of OA severity by structural analysis of bone. © 2016 The Authors. Journal of Orthopaedic Research Published by Wiley Periodicals, Inc. J Orthop Res 35:785-792, 2017.

Individual and combined effects of OA-related subchondral bone alterations on proximal tibial surface stiffness: a parametric finite element modeling study

The role of subchondral bone in OA pathogenesis is unclear. While some OA-related changes to morphology and material properties in different bone regions have been described, the effect of these alterations on subchondral bone surface stiffness has not been investigated. The objectives of this study were to characterize the individual (Objective 1) and combined (Objective 2) effects of OA-related morphological and mechanical alterations to subchondral and epiphyseal bone on surface stiffness of the proximal tibia. We developed and validated a parametric FE model of the proximal tibia using quantitative CT images of 10 fresh-frozen cadaveric specimens and in situ macro-indentation testing. Using this validated FE model, we estimated the individual and combined roles of OA-related alterations in subchondral cortical thickness and elastic modulus, and subchondral trabecular and epiphyseal trabecular elastic moduli on local surface stiffness. A 20% increase in subchondral cortical or subchondral trabecular elastic moduli resulted in little change in stiffness (1% increase). A 20% reduction in epiphyseal trabecular elastic modulus, however, resulted in an 11% reduction in stiffness. Our parametric analysis suggests that subchondral bone stiffness is affected primarily by epiphyseal trabecular bone elastic modulus rather than subchondral cortical and trabecular morphology or mechanical properties. Our results suggest that observed OA-related alterations to epiphyseal trabecular bone (e.g., lower mineralization, bone volume fraction, density and elastic modulus) may contribute to OA proximal tibiae being less stiff than normal.

Three-Dimensional Quantitative Morphometric Analysis (QMA) for In Situ Joint and Tissue Assessment of Osteoarthritis in a Preclinical Rabbit Disease Model

This work utilises advances in multi-tissue imaging, and incorporates new metrics which define in situ joint changes and individual tissue changes in osteoarthritis (OA). The aims are to (1) demonstrate a protocol for processing intact animal joints for microCT to visualise relevant joint, bone and cartilage structures for understanding OA in a preclinical rabbit model, and (2) introduce a comprehensive three-dimensional (3D) quantitative morphometric analysis (QMA), including an assessment of reproducibility. Sixteen rabbit joints with and without transection of the anterior cruciate ligament were scanned with microCT and contrast agents, and processed for histology. Semi-quantitative evaluation was performed on matching two-dimensional (2D) histology and microCT images. Subsequently, 3D QMA was performed; including measures of cartilage, subchondral cortical and epiphyseal bone, and novel tibio-femoral joint metrics. Reproducibility of the QMA was tested on seven additional joints. A significant correlation was observed in cartilage thickness from matching histology-microCT pairs. The lateral compartment of operated joints had larger joint space width, thicker femoral cartilage and reduced bone volume, while osteophytes could be detected quantitatively. Measures between the in situ tibia and femur indicated an altered loading scenario. High measurement reproducibility was observed for all new parameters; with ICC ranging from 0.754 to 0.998. In conclusion, this study provides a novel 3D QMA to quantify macro and micro tissue measures in the joint of a rabbit OA model. New metrics were established consisting of: an angle to quantitatively measure osteophytes (σ), an angle to indicate erosion between the lateral and medial femoral condyles (ρ), a vector defining altered angulation (λ, α, β, γ) and a twist angle (τ) measuring instability and tissue degeneration between the femur and tibia, a length measure of joint space width (JSW), and a slope and intercept (m, Χ) of joint contact to demonstrate altered loading with disease progression, as well as traditional bone and cartilage and histo-morphometry measures. We demonstrate correlation of microCT and histology, sensitive discrimination of OA change and robust reproducibility.

Comparison of the Chemical Composition of Subchondral Trabecular Bone of Medial Femoral Condyle between with Advanced Osteoarthritis and without Osteoarthritis

Background

The purpose of this study is to investigate differences of chemical composition between subchondral bone in advanced osteoarthritic (OA) and non-OA distal femur.

Methods

Twenty femurs were harvested, respectively. The subchondral trabeculae were obtained from the middle of medial articular surface of distal femurs. A 10 mm diameter cylindrical saw was used to harvest. Raman spectroscopy, a non-destructive technique, was employed to determine the chemical information of the trabecular bones in the human distal femurs.

Results

The maximum intensity of the phosphate peak was 2,376.51±954.6 for the non-OA group and 1,936.3±831.75 for the OA group. The maximum intensity of the phosphate peak observed between the two groups was significantly different (P=0.017). The maximum intensity of the amide I peak were 474.17±253.42 for the nonOA group and 261.91±205.61 for the OA group. The maximum intensity of the amide I peak were significantly different between the two groups (P=0.042). Also, among other chemical and matrix components (Hydroxyproline,Carbonate, Amide IIIdisordered;ordered, and CH2), the spectrums showed similar significant differences in the intensity (P=0.027, P=0.014, P=0.012; P=0.038, P=0.029). Area integration were performed to determine disorder in collagen's secondary structure via amide III (alpha helix/random coil). The value of the alpha helix to random coil band area are significantly different (P=0.021) and result showing that there was a trend toward higher collagen maturity for the nonosteoarthritic bone specimens.

Conclusions

The result suggested that OA may affect the chemical compositions of trabecular bone, and such distinctive chemical information may be.

Intra-articular resveratrol injection prevents osteoarthritis progression in a mouse model by activating SIRT1 and thereby silencing HIF-2α

We investigated the feasibility of the intra-articular injection of resveratrol for preventing the progression of existing cartilage degeneration in a mouse model of osteoarthritis (OA). The effects of resveratrol on the expression of silent information regulator 2 type 1 (SIRT1), hypoxia-inducible factor-2α (HIF-2α) and catabolic factors in OA cartilage was explored. OA was induced in the mouse knee via destabilization of the medial meniscus (DMM). Resveratrol was injected weekly into the operated knee beginning 4 weeks after surgery. The OA phenotype was evaluated via histological and immunohistochemical analyses at 8 weeks after DMM. Western blot analysis was performed to identify whether resveratrol modulated the interleukin (IL)-1β-induced expression of HIF-2α in human chondrocytes. Histologically, resveratrol treatment preserved the structural homeostasis of the articular cartilage and the subchondral bone. Following resveratrol injection, the expression of collagen type II was retained, but the expression of inducible nitric oxide synthase and matrix metalloproteinase-13 was reduced in OA cartilage. Moreover, the administration of resveratrol significantly induced the activation of SIRT1 and the inhibition of HIF-2α expression in mouse OA cartilage and in IL-1β-treated human chondrocytes. These findings indicate that the intra-articular injection of resveratrol significantly prevents the destruction of OA cartilage by activating SIRT1 and thereby suppressing the expression of HIF-2α and catabolic factors.

Alterations in subchondral bone plate, trabecular bone and articular cartilage properties of rabbit femoral condyles at 4 weeks after anterior cruciate ligament transection

OBJECTIVE

To quantify early osteoarthritic-like changes in the structure and volume of subchondral bone plate and trabecular bone and properties of articular cartilage in a rabbit model of osteoarthritis (OA) induced by anterior cruciate ligament transection (ACLT).

METHODS

Left knee joints from eight skeletally mature New Zealand white rabbits underwent ACLT surgery, while the contralateral (CTRL) right knee joints were left unoperated. Femoral condyles were harvested 4 weeks after ACLT. Micro-computed tomography imaging was applied to evaluate the structural properties of subchondral bone plate and trabecular bone. Additionally, biomechanical properties, structure and composition of articular cartilage were assessed.

RESULTS

As a result of ACLT, significant thinning of the subchondral bone plate (P < 0.05) was accompanied by significantly reduced trabecular bone volume fraction and trabecular thickness in the medial femoral condyle compartment (P < 0.05), while no changes were observed in the lateral compartment. In both lateral and medial femoral condyles, the equilibrium modulus and superficial zone proteoglycan (PG) content were significantly lower in ACLT than CTRL joint cartilage (P < 0.05). Significant alterations in the collagen orientation angle extended substantially deeper into cartilage from the ACLT joints in the lateral femoral condyle relative to the medial condyle compartment (P < 0.05).

CONCLUSIONS

In this model of early OA, significant changes in volume and microstructure of subchondral bone plate and trabecular bone were detected only in the femoral medial condyle, while alterations in articular cartilage properties were more severe in the lateral compartment. The former finding may be associated with reduced joint loading in the medial compartment due to ACLT, while the latter finding reflects early osteoarthritic changes in the lateral compartment.

UP3005, a Botanical Composition Containing Two Standardized Extracts of Uncaria gambir and Morus alba, Improves Pain Sensitivity and Cartilage Degradations in Monosodium Iodoacetate-Induced Rat OA Disease Model

Osteoarthritis (OA) is a multifactorial disease primarily noted by cartilage degradation in association with inflammation that causes significant morbidity, joint pain, stiffness, and limited mobility. Present-day management of OA is inadequate due to the lack of principal therapies proven to be effective in hindering disease progression where symptomatic therapy focused approach masks the actual etiology leading to irreversible damage. Here, we describe the effect of UP3005, a composition containing a proprietary blend of two standardized extracts from the leaf of Uncaria gambir and the root bark of Morus alba, in maintaining joint structural integrity and alleviating OA associated symptoms in monosodium-iodoacetate- (MIA-) induced rat OA disease model. Pain sensitivity, micro-CT, histopathology, and glycosaminoglycans (GAGs) level analysis were conducted. Diclofenac at 10 mg/kg was used as a reference compound. UP3005 resulted in almost a complete inhibition in proteoglycans degradation, reductions of 16.6% (week 4), 40.5% (week 5), and 22.0% (week 6) in pain sensitivity, statistically significant improvements in articular cartilage matrix integrity, minimal visual subchondral bone damage, and statistically significant increase in bone mineral density when compared to the vehicle control with MIA. Therefore, UP3005 could potentially be considered as an alternative therapy from natural sources for the treatment of OA and/or its associated symptoms.

Distribution of vitamin K2 in subchondral bone in osteoarthritic knee joints

PURPOSE

Vitamin K may have multiple effects on articular cartilage and subchondral bone that could modulate the pathogenesis of osteoarthritis (OA). The purpose of this study was to evaluate the distribution of vitamin K2 in harvested bones obtained during total knee arthroplasty in knee OA patients.

METHODS

High-performance liquid chromatography was used to measure vitamin K2 in harvested bones obtained during 58 TKA procedures. Vitamin K2 levels were analysed in the medial (FM) and lateral (FL) femoral condyles and in the medial (TM) and lateral (TL) tibial condyles.

RESULTS

There was significantly more vitamin K2 in the lateral femoral and tibial condyles than in the corresponding medial condyles (FL vs. FM, p < 0.0001; TL vs. TM, p < 0.0001). There was significantly more vitamin K2 in the FL than in the TL (p = 0.003), and in the FM, vitamin K2 levels were higher than those of the TM, although this was not significant (n.s.). There were no significant differences in vitamin K2 levels in men versus women nor was there a significant correlation with age.

CONCLUSIONS

This study suggested that vitamin K2 might affect bone turnover since medial condyles showing advanced OA had lower vitamin K2 levels, while lateral condyles showing less advanced OA contained more vitamin K2. Gender and age were not correlated with vitamin K2 localization. All cases had Grade IV OA, and this study suggested that OA grade might be important in controlling the vitamin K2 levels in human bones.

Assessment of articular cartilage and subchondral bone using EPIC-microCT in Labrador retrievers with incipient medial coronoid disease

The aetiopathogenesis of medial coronoid disease (MCD) remains obscure, despite its high prevalence. The role of changes to subchondral bone or articular cartilage is much debated. Although there is evidence of micro-damage to subchondral bone, it is not known whether this is a cause or a consequence of MCD, nor is it known whether articular cartilage is modified in the early stages of the disease. The aim of the present study was to use equilibrium partitioning of an ionic contrast agent with micro-computed tomography (microCT) to investigate changes to both the articular cartilage and the subchondral bone of the medial coronoid processes (MCP) of growing Labrador retrievers at an early stage of the disease and at different bodyweights. Of 14 purpose-bred Labrador retrievers (15-27 weeks), six were diagnosed with bilateral MCD and one was diagnosed with unilateral MCD on the basis of microCT studies. The mean X-ray attenuation of articular cartilage was significantly higher in dogs with MCD than in dogs without MCD (P<0.01). In all dogs, the mean X-ray attenuation of articular cartilage was significantly higher at the lateral (P<0.001) than at the proximal aspect of the MCP, indicating decreased glycosaminoglycan content. Changes in parameters of subchondral bone micro-architecture, namely the ratio of bone volume to tissue volume (BV/TV), bone surface density (BS/TV), bone surface to volume ratio (BS/BV), trabecular thickness (Tb.Th; mm), size of marrow cavities described by trabecular spacing (Tb.Sp; mm), and structural model index (SMI), differed significantly by litter (P<0.05) due to the difference in age and weight, but not by the presence/absence of MCD (P>0.05), indicating that subchondral bone density is not affected in early MCD. This study demonstrated that cartilage matrix and not subchondral bone density is affected in the early stages of MCD.

Histological and molecular characterisation of feline humeral condylar osteoarthritis

Background

Osteoarthritis (OA) is a clinically important and common disease of older cats. The pathological changes and molecular mechanisms which underpin the disease have yet to be described. In this study we evaluated selected histological and transcriptomic measures in the articular cartilage and subchondral bone (SCB) of the humeral condyle of cats with or without OA.

Results

The histomorphometric changes in humeral condyle were concentrated in the medial aspect of the condyle. Cats with OA had a reduction in articular chondrocyte density, an increase in the histopathological score of the articular cartilage and a decrease in the SCB porosity of the medial part of the humeral condyle. An increase in LUM gene expression was observed in OA cartilage from the medial part of the humeral condyle.

Conclusions

Histopathological changes identified in OA of the feline humeral condyle appear to primarily affect the medial aspect of the joint. Histological changes suggest that SCB is involved in the OA process in cats. Differentiating which changes represent OA rather than the aging process, or the effects of obesity and or bodyweight requires further investigation.

In situ fatty acid profile of femoral cancellous subchondral bone in osteoarthritic and fragility fracture females: implications for bone remodelling

We report here differences in the fatty acid profile of cancellous bone matrix, including n-3, n-6, mono- and poly-unsaturated, as well as saturated fats, between femoral heads from female OA (n=8, aged 68-88years), fractured neck of femur (#NOF) (n=19, 67-88years) and autopsy controls (CTRL) (n=4, 85-97years). Femoral heads were collected from individuals undergoing orthopaedic surgery for OA or #NOF; the fatty acid profile of sub-samples from the superior principal compressive and superior principal tensile regions were determined by gas chromatography. A total of 42 individual fatty acids were detected at varying concentrations with significant differences between subchondral bone from OA subjects, subchondral bone from #NOF subjects and subchondral bone from CTRL subjects, as well as between the superior principal compressive and superior principal tensile regions (for saturated fats only). Subchondral bone from OA subjects had higher total n-6 (OA=10.89±3.17, #NOF=11.11±1.83, CTRL=8.32±2.05, p=0.008) and total n-3 (OA=1.34±0.38, #NOF=1.19±0.18, CTRL=1.15±0.48, p=0.011) percentages than subchondral bone from #NOF subjects and subchondral bone from CTRL subjects, and there was no difference in the n-6:n-3 ratio, nor within the percentage of n-9 fatty acids. Arachidonic acid (OA=0.42±0.16, #NOF=0.26±0.06, CTRL=0.28±0.06, p=0.01), and γ-linolenic acid (OA=0.11±0.03, #NOF=0.05±0.02, CTRL=0.04±0.02, p<0.001) were higher in subchondral bone from OA subjects than subchondral bone from #NOF subjects and subchondral bone from CTRL subjects. In conclusion, there is a wide diversity of fatty acids in cancellous bone matrix from the femoral heads of OA and #NOF, suggesting they may have regulatory effects on inflammatory processes, and their metabolites. This article is part of a Special Issue entitled "Osteoarthritis".

Pathophysiology of peri-articular bone changes in osteoarthritis

Osteoarthritis (OA) is a disease that involves the entire joint, but its pathophysiology is not well described. Alterations in peri-articular bone are an integral part of the OA disease process and different aspects of bone changes have been described in different patient (sub)groups and animal models. In this review we will discuss the osteoarthritis pathophysiology from the perspective of periarticular bone changes, which can be considered at three hierarchical levels: the bone (or joint) shape, the subchondral bone architecture and its cellular and molecular phenotype. In this review we try to provide an overview of the current knowledge of peri-articular bone changes in OA and what it could possibly imply for the initiation of OA and its progression. This article is part of a Special Issue entitled "Osteoarthritis".

Relationship between cartilage and subchondral bone lesions in repetitive impact trauma-induced equine osteoarthritis

OBJECTIVE

To correlate degenerative changes in cartilage and subchondral bone in the third carpal bone (C3) of Standardbred racehorses with naturally occurring repetitive trauma-induced osteoarthritis.

DESIGN

Fifteen C3, collected from Standardbred horses postmortem, were assessed for cartilage lesions by visual inspection and divided into Control (CO), Early Osteoarthritis (EOA) and Advanced Osteoarthritis (AOA) groups. Two osteochondral cores were harvested from corresponding dorsal sites on each bone and scanned with a micro-computed tomography (CT) instrument. 2D images were assembled into 3D reconstructions that were used to quantify architectural parameters from selected regions of interest, including bone mineral density and bone volume fraction. 2D images, illustrating the most severe lesion per core, were scored for architectural appearance by blinded observers. Thin sections of paraffin-embedded decalcified cores stained with Safranin O-Fast Green, matched to the micro-CT images, were scored using a modified Mankin scoring system.

RESULTS

Subchondral bone pits with deep focal areas of porosity were seen more frequently in AOA than EOA but never in CO. Articular cartilage damage was seen in association with a reduction in bone mineral and loss of bone tissue. Histological analyses revealed significant numbers of microcracks in the calcified cartilage of EOA and AOA groups and a progressive increase in the score compared with CO bones.

CONCLUSION

The data reveal corresponding, progressive degenerative changes in articular cartilage and subchondral bone, including striking focal resorptive lesions, in the third carpal bone of racehorses subjected to repetitive, high impact trauma.

Predicting subchondral bone stiffness using a depth-specific CT topographic mapping technique in normal and osteoarthritic proximal tibiae

BACKGROUND

Subchondral bone stiffness is thought to be involved in osteoarthritis pathogenesis. Our objective was to determine if a CT imaging technique, which measures density in relation to depth from the subchondral surface, could predict the stiffness of proximal tibial subchondral bone. A second objective was to determine whether cartilage degeneration (an indicator of osteoarthritis) affected predictions.

METHODS

Thirteen proximal tibial compartments (4 medial, 9 lateral) from 10 male donors (age: mean 73.2, SD 10.6 years) were scanned using quantitative CT. We assessed average subchondral bone mineral density across different depths (0-2.5, 0-5, 0-10 mm) and layers (2.5-5, 5-10 mm) measured relative to the subchondral surface. We classified cartilage status as normal or degenerated using the International Cartilage Repair Society system. We performed macro indentation testing directly at the subchondral surface, and related stiffness to density measures using power-law regression models adjusted for side, age and cartilage status. We tested the coincidence of normal and degenerated regression models using F test statistics.

FINDINGS

Density measures nearest the subchondral bone surface (0-2.5 mm) were most effective at predicting subchondral bone stiffness (r²=0.67, p<0.001). The predictive ability of depth-specific density measures decreased when density was averaged across larger depths or layers deep to the subchondral surface. Cartilage status did not affect model predictions.

INTERPRETATION

Depth-specific density measures have potential use as in vivo imaging tools for characterizing subchondral bone density and estimating stiffness. This information could help explain the role of subchondral bone in osteoarthritis pathogenesis.

Association of Baseline Knee Bone Size, Cartilage Volume, and Body Mass Index with Knee Cartilage Loss Over Time: A Longitudinal Study in Younger or Middle-aged Adults

Objective.

To determine the association of knee bone size, cartilage volume, and body mass index (BMI) at baseline with knee cartilage loss over 2 years in younger or middle-aged adults.

Methods.

A total of 324 subjects (mean age 45 yrs, range 26–61) were measured at baseline and about 2 years later. Knee cartilage volume and bone size were determined using T1-weighted fat-saturated magnetic resonance imaging.

Results.

In multivariable analysis, baseline knee bone size was negatively associated with annual change in knee cartilage volume at medial and lateral tibial sites (ß = −0.62% to −0.47%/cm2, all p < 0.001). The associations disappeared at medial tibial site after adjustment for baseline cartilage volume and became of borderline statistical significance at lateral tibial site after adjustment for both baseline cartilage volume and osteophytes (ß = −0.29, p = 0.059). Baseline knee cartilage volume was consistently and negatively associated with annual change in knee cartilage volume at all 3 medial tibial, lateral tibial, and patellar sites (ß = −4.41% to −1.37%/ml, all p < 0.001). Baseline BMI was negatively associated with an annual change in knee cartilage volume, but only in subjects within the upper tertile of baseline cartilage volume, even after adjusting for cartilage defects (ß = −0.16% to −0.34%/kg/m2, all p < 0.05).

Conclusion.

Our study suggests that both higher baseline tibial bone area and knee cartilage volume (most likely due to cartilage swelling) are associated with greater knee cartilage loss over 2 years. A higher BMI was associated with greater knee cartilage loss only in subjects with higher baseline cartilage volume.

Computed tomography topographic mapping of subchondral density (CT-TOMASD) in osteoarthritic and normal knees: methodological development and preliminary findings

OBJECTIVES

To develop a precise imaging tool which measures three-dimensional (3D) subchondral bone mineral density (BMD), and investigate its ability to distinguish subchondral bone properties in osteoarthritic and normal cadaveric tibiae.

METHODS

We developed a novel imaging tool [Computed tomography topographic mapping of subchondral density (CT-TOMASD)], which employs a surface projection image processing technique to map 3D subchondral BMD measured in relation to depth from the joint surface. Sixteen intact cadaver knees from 10 donors (8M:2F; age: 77.8+/-7.4) were scanned using quantitative computed tomography (QCT). Projections of average BMD to normalized depths of 2.5mm and 5.0mm were acquired, with regional analyses including: (1) medial and lateral BMD, (2) anterior/central/posterior compartmental BMD, (3) max BMD contained within a 10mm diameter 'core', and (4) medial:lateral BMD ratio. Precision was assessed using coefficients of variation (CV%). Osteoarthritis (OA) severity was assessed by examination of computed tomography (CT) and fluoroscopic radiographic images, and categorized using modified Kellgren-Lawrence (mKL) scoring.

RESULTS

Precision errors for CT-TOMASD BMD measures were focused around 1.5%, reaching a maximum CV% of 3.5%. OA was identified in eight compartments of six knees. Substantial qualitative and quantitative differences were observed between the OA and normal knees, with the medial:lateral BMD ratio and peak core regional analyses demonstrating differences greater than 4.7 standard deviations (SDs) when compared with normals. Preliminary results revealed effect sizes ranging from 1.6 to 4.3 between OA and normal knees.

CONCLUSIONS

CT-TOMASD offers precise 3D measures of subchondral BMD. Preliminary results demonstrate large qualitative and quantitative differences and large effect sizes between OA and normal knees. This method has the potential to identify and quantify changes in subchondral BMD associated with OA disease progression.

Perilesional changes of focal osteochondral defects in an ovine model and their relevance to human osteochondral injuries

Perilesional changes of chronic focal osteochondral defects were assessed in the knees of 23 sheep. An osteochondral defect was created in the main load-bearing region of the medial condyle of the knees in a controlled, standardised manner. The perilesional cartilage was evaluated macroscopically and biopsies were taken at the time of production of the defect (T0), during a second operation one month later (T1), and after killing animals at three (T3; n = 8), four (T4; n = 8), and seven (T7; n = 8) months. All the samples were histologically assessed by the International Cartilage Repair Society grading system and Mankin histological scores. Biopsies were taken from human patients (n = 10) with chronic articular cartilage lesions and compared with the ovine specimens. The ovine perilesional cartilage presented with macroscopic and histological signs of degeneration. At T1 the International Cartilage Repair Society ‘Subchondral Bone’ score decreased from a mean of 3.0 (sd 0) to a mean of 1.9 (sd 0.3) and the ‘Matrix’ score from a mean of 3.0 (sd 0) to a mean of 2.5 (sd 0.5). This progressed further at T3, with the International Cartilage Repair Society ‘Surface’ grading, the ‘Matrix’ grading, ‘Cell Distribution’ and ‘Cell Viability’ grading further decreasing and the Mankin score rising from a mean of 1.3 (sd 1.4) to a mean of 5.1 (sd 1.6). Human biopsies achieved Mankin grading of a mean of 4.2 (sd 1.6) and were comparable with the ovine histology at T1 and T3.

The perilesional cartilage in the animal model became chronic at one month and its histological appearance may be considered comparable with that seen in human osteochondral defects after trauma.

Automated objective scoring of histologically apparent cartilage degeneration using a custom image analysis program

Histologic assessment of cartilage degradation has traditionally involved semiquantitative techniques, the most commonly utilized being the Mankin scale. Such assessments depend on human observer subjectivity, and thus have drawn criticism on the basis of associated inter- and intraobserver variability. We report a newly developed computational image analysis procedure for fully automated and fully objective assessment of the Mankin scale. Image processing routines were developed in a widely used programming environment (Matlab) to analyze cartilage degradation. One hundred and twenty-five histology images incorporating a wide range of degradation features were analyzed by the algorithm and by seven observers experienced in cartilage histologic assessment. Based on random effects linear statistical models, the computer program performed well, showing a correlation of 0.88 between its Mankin scores and latent (average of human observers') image scores. Regarding the four subcomponents of the Mankin scale, computer program correlations with observer scores were best for surface defect and proteoglycan depletion, but less favorable for cellularity and tidemark invasion. While limitations exist with image processing techniques, the new algorithm provides an objective and automated method for analyzing cartilage histology sections, consistent with human observer grading.

Protective effects of total fraction of avocado/soybean unsaponifiables on the structural changes in experimental dog osteoarthritis: inhibition of nitric oxide synthase and matrix metalloproteinase-13

INTRODUCTION

The aims of this study were, first, to investigate the in vivo effects of treatment with avocado/soybean unsaponifiables on the development of osteoarthritic structural changes in the anterior cruciate ligament dog model and, second, to explore their mode of action.

METHODS

Osteoarthritis was induced by anterior cruciate ligament transection of the right knee in crossbred dogs. There were two treatment groups (n = 8 dogs/group), in which the animals received either placebo or avocado/soybean unsaponifiables (10 mg/kg per day), which were given orally for the entire duration of the study (8 weeks). We conducted macroscopic and histomorphological analyses of cartilage and subchondral bone of the femoral condyles and/or tibial plateaus. We also conducted immunohistochemical analyses in cartilage for the following antigens: inducible nitric oxide synthase, matrix metalloproteinase (MMP)-1, MMP-13, a disintegrin and metalloproteinase domain with thrombospondin motifs (ADAMTS)4 and ADAMTS5.

RESULTS

The size of macroscopic lesions on the tibial plateaus was decreased (P = 0.04) in dogs treated with the avocado/soybean unsaponifiables. Histologically, in these animals the severity of cartilage lesions on both tibial plateaus and femoral condyles, and the cellular infiltration in synovium were significantly decreased (P = 0.0002 and P = 0.04, respectively). Treatment with avocado/soybean unsaponifiables also reduced loss of subchondral bone volume (P < 0.05) and calcified cartilage thickness (P = 0.01) compared with placebo. Immunohistochemical analysis of cartilage revealed that avocado/soybean unsaponifiables significantly reduced the level of inducible nitric oxide synthase (P < 0.05) and MMP-13 (P = 0.01) in cartilage.

CONCLUSIONS

This study demonstrates that treatment with avocado/soybean unsaponifiables can reduce the development of early osteoarthritic cartilage and subchondral bone lesions in the anterior cruciate ligament dog model of osteoarthritis. This effect appears to be mediated through the inhibition of inducible nitric oxide synthase and MMP-13, which are key mediators of the structural changes that take place in osteoarthritis.

Relationship between low bone mineral density and varus deformity in postmenopausal women with knee osteoarthritis

OBJECTIVE

To assess the relationship between bone mineral density (BMD) and varus deformity arising from bone structural changes caused by knee osteoarthritis (OA) in postmenopausal women.

METHODS

This cross-sectional study involved 135 consecutive postmenopausal female patients who had varus knee OA and a Kellgren-Lawrence grade > or = 2. Knee radiographs were obtained with the patient standing on one leg, and subjects were classified into 3 tertile groups according to femorotibial angle, which was taken as a measure of varus knee OA severity. We also measured the 3 subangles that make up the femorotibial angle, and focused on the varus inclination of the tibial plateau. BMD was measured in the lumbar spine, femoral neck, and medial and lateral tibial condyles using dual-energy X-ray absorptiometry. Differences between femorotibial angle tertile groups were assessed, and associations between femorotibial sub-angles and BMD values at various points were evaluated.

RESULTS

After adjustment for age and body mass index, there was no significant association between the varus inclination of the tibial plateau and lumbar spine BMD. A weak but statistically significant negative correlation existed between varus inclination of the tibial plateau and BMD at the ipsilateral proximal femur and lateral tibial condyle.

CONCLUSION

Varus inclination of the tibial plateau was significantly more severe in the femorotibial angle tertile 3 group, and in patients with lower BMD in the ipsilateral lower limb. Varus knee OA may result not only from cartilage loss but also from structural changes of the bone.

Quantitative MRI of parallel changes of articular cartilage and underlying trabecular bone in degeneration

OBJECTIVE

To determine the interrelations between degenerative changes in articular cartilage and underlying trabecular bone during development of osteoarthritis and to test the ability of quantitative magnetic resonance imaging (MRI) to detect those changes.

METHODS

Human cadaver patellae were investigated with quantitative MRI methods, T(2) and dGEMRIC, at 1.5T. Same measurements for isolated cartilage samples were performed at 9.4T. Bone samples, taken at sites matched with cartilage analyses, were measured with MRI and peripheral quantitative computed tomography (pQCT). Mechanical and quantitative microscopic methods were also utilized for both cartilage and bone samples.

RESULTS

Significant differences were found between the samples with different stages of degeneration in mechanical properties, T(2) at 1.5T and proteoglycan (PG) content of articular cartilage. dGEMRIC at 9.4T discerned samples with advanced degeneration from the others. Bone variables measured with pQCT discerned samples with no or minimal and advanced degeneration, and mechanical properties of trabecular bone discerned samples with no or minimal degeneration from the others. Significant linear correlations were found between the bone and cartilage parameters. Characteristically, associations between variables were stronger within the samples with no or minimal degeneration compared to all samples.

CONCLUSIONS

Quantitative MRI variables, especially T(2) relaxation time of articular cartilage, may be feasible surrogate markers for early and advanced osteoarthritic changes in joint tissues, including decreased elastic moduli, PG and collagen contents of cartilage and mineral density and volume fraction of trabecular bone. Further work is required to resolve the relaxation mechanisms at clinically applicable field strengths.

The effects of glucosamine hydrochloride on subchondral bone changes in an animal model of osteoarthritis

OBJECTIVE

To quantify periarticular subchondral bone changes in a rabbit model of experimental osteoarthritis (OA), and to determine the effects of continuous administration of a clinically relevant dose of glucosamine HCl on subchondral bone changes in this model.

METHODS

Anterior cruciate ligament transection (ACLT) was performed on the left femorotibial joints of 16 rabbits to induce OA. Ten rabbits that did not undergo ACLT served as unoperated controls. Eight rabbits that underwent ACLT and 6 control rabbits were treated with 100 mg of glucosamine daily, and the others were given a placebo. The articular cartilage was evaluated macroscopically and graded at the time of necropsy, 8 weeks after ACLT. Bone mineral density (BMD) was measured using dual-energy x-ray absorptiometry on the dissected distal femur and proximal tibia. Subchondral trabecular bone turnover, architecture, and connectivity, as well as subchondral plate thickness and mineralization were studied on the undecalcified tibia sections from each animal.

RESULTS

Eight weeks after ACLT, most of the operated joints had various degrees of cartilage damage and fibrillation. Compared with the control group, the ACLT group had significantly increased subchondral bone turnover and lower BMD, bone volume, connectivity, and bone mineralization. The high bone turnover was significantly reduced in glucosamine-treated animals that underwent ACLT. In fact, there were no significant differences between the ACLT/glucosamine group and the control/glucosamine group in most of the bone parameters studied.

CONCLUSION

This study shows that subchondral bone turnover, structure, and mineralization are significantly altered in the early stages of experimental OA, and that these changes are attenuated by glucosamine treatment.

Subchondral bone micro-architectural alterations in osteoarthritis: a synchrotron micro-computed tomography study

OBJECTIVES

We evaluated the three-dimensional (3D) micro-architecture of subchondral trabecular (Tb) bone in osteoarthritis (OA). Due to high signal-to-noise ratio and high resolution, micro-computed tomography (micro-CT) by synchrotron radiation is considered as the gold standard for bone micro-architecture imaging.

DESIGN

Subchondral bone were extracted from femoral heads in OA cases in areas without cartilage (OAc-; n=6) and in adjacent areas with cartilage (OAc+; n=6) and compared to eight subchondral bone cores from osteoporosis cases (OP). The voxel size of images was 10.13 microm. We measured the bone volume fraction (BV/TV) and morphological parameters: Tb thickness (TbTh), Tb spacing (TbSp), Tb number (TbN), and bone surface/bone volume (BS/BV). The degree of anisotropy (DA), the connectivity by the Euler number and the degree of mineralization (DM) were equally assessed.

RESULTS

BV/TV and morphological parameters showed significant differences between OAc- and OP samples (P<0.01 except TbTh: P<0.05) and between OAc- and OAc+ (0.05<P<0.01) but no difference between OAc+ and OP except TbN (P<0.01). The connectivity was higher in OAc- comparatively to OAc+ and OP. The DA were significantly different between OA and OP cases (P<0.01) but not between OAc- and OAc+ specimens. The DMs (mean+/-SD) were 0.817+/-0.142 g/cm(3), 0.873+/-0.161 g/cm(3), 0.906+/-0.156 g/cm(3) for OAc-, OAc+, OP (P<0.01), respectively.

CONCLUSION

Subchondral bone changes were mainly observed in advanced OA, when cartilage has been deleted and preserved in adjacent area. These data suggest that subchondral bone changes would be rather secondary to the cartilage deterioration than a primitive mechanism of OA. Nevertheless, longitudinal data could bring more accurate conclusions.

Altered cartilage mechanics and histology in knee osteoarthritis: relation to clinical assessment (ICRS Grade)

OBJECTIVE

Substantial changes in articular cartilage composition and mechanical properties occur during the development of osteoarthritis (OA). While softening in the initial stage is reported and sometimes used as an indicator of early OA, there is a lack of data relating the macroscopic appearance of cartilage to its mechanical and histological properties in all stages of degeneration. Knowledge about the mechanical quality of the tissue is important for diagnostic reasons and the understanding of the development of OA.

DESIGN

The cartilage areas of 21 osteoarthritic human cadaver tibia plateaus were classified using the International Cartilage Repair Society (ICRS) system. A material testing device determined the Young's modulus of the cartilage by unconfined compression. Histological analysis used haematoxylin and eosin staining and Safranin-O staining for the evaluation of the Mankin score.

RESULTS

A correlation between increasing ICRS Grade and stiffness reduction was found (R2=0.69). Stiffness values were for ICRS Grades 1, 2 and 3: E1=0.50+/-0.14 MPa, E2=0.37+/-0.13 MPa and E3=0.28+/-0.12 MPa, respectively. The histological evaluation confirmed the ICRS classification (R2=0.74). A moderate correlation between Mankin score and cartilage stiffness was observed (R2=0.47).

CONCLUSIONS

The results indicate a relation between structural, mechanical and histological changes in all stages of the degeneration. With increasing ICRS Grade the cartilage stiffness, which is primarily influenced by the integrity of the extracellular matrix, decreases. Therefore, methods of stiffness determination such as indentation may be used to characterize cartilage in all stages of OA. However, the data suggest that differentiating between healthy cartilage and ICRS Grade 1 may be difficult using mechanical testing alone.

Evaluation of subchondral bone mineral density associated with articular cartilage structure and integrity in healthy equine joints with different functional demands

OBJECTIVE

To determine and correlate subchondral bone mineral density and overlying cartilage structure and tensile integrity in mature healthy equine stifle (low magnitude loading) and metacarpophalangeal (high magnitude loading) joints.

ANIMALS

8 healthy horses, 2 to 3 years of age.

PROCEDURE

Osteochondral samples were acquired from the medial femoral condyle (FC) and medial trochlear ridge (TR) of the stifle joint and from the dorsal (MC3D) and palmar (MC3P) aspects of the distal medial third metacarpal condyles of the metacarpophalangeal joint. Articular cartilage surface fibrillation (evaluated via India ink staining) and tensile biomechanical properties were determined. The volumetric bone mineral density (vBMD) of the underlying subchondral plate was assessed via dual-energy x-ray absorptiometry.

RESULTS

Cartilage staining (fibrillation), tensile moduli, tensile strength, and vBMD were greater in the MC3D and MC3P locations, compared with the FC and TR locations, whereas tensile strain at failure was less in MC3D and MC3P locations than FC and TR locations. Cartilage tensile moduli correlated positively with vBMD, whereas cartilage staining and tensile strain at failure correlated negatively with vBMD.

CONCLUSIONS AND CLINICAL RELEVANCE

In areas of high joint loading, the subchondral bone had high vBMD and the articular cartilage surface layer had high tensile stiffness but signs of structural wear (fibrillation and low failure strain). The site-dependent variations and relationships in this study support the concept that articular cartilage and subchondral bone normally adapt to physiologic loading in a coordinated way.

The relationships between bone mineral density in the spine, hip, distal femur and proximal tibia and medial minimum joint space width in the knees of healthy females

OBJECTIVE

To investigate the relationships between bone mineral density (BMD) in the hip, spine, distal femur and proximal tibia and minimum joint space width (mJSW) in the knees of healthy women.

METHODS

Women 22-68 years old without a history of knee pain, bone or joint disease or injury underwent a single, fixed-flexion knee X-ray. Radiographs were graded according to the Kellgren-Lawrence scale and analyzed for mJSW using a computer algorithm. Dual X-ray absorptiometry scans of the spine, hip, distal femur and proximal tibia were also acquired for each participant. Femur and tibia scans were acquired and analyzed using a modified version of the lumbar spine software.

RESULTS

Forty-five females, mean [standard deviation (SD)] age and body mass index (BMI) of 40.1 (13.9) years and 24.6 (4.5)kg/m(2), respectively, participated. The mean (SD) mJSW was 4.64 (0.68)mm. Linear regression analyses controlling for age and BMI revealed that BMD in the femoral trochanter and the central two regions of the tibia (T2 and T3) was significantly related to mJSW in the knee. A backwards regression analysis performed to determine which region of interest is most significantly related to mJSW revealed that femoral trochanter BMD (beta-value=0.416) is the most significant.

CONCLUSIONS

In contrast to the suggestion that BMD is negatively correlated with mJSW in the knees of osteoarthritic individuals, these results suggest that increasing BMD in the femoral trochanter and tibia is significantly associated with increasing mJSW in healthy females. Further investigation of this relationship is warranted.

The 'anvil' osteophyte-a primary cause of fixed flexion of the knee?

Three cases are reported in which clinical presentation was with arthritic symptoms and inability to straighten the knee. An unusually prominent anterior tibial osteophyte, whose shape is remarkably suggestive of a blacksmith's anvil, appeared to be a contributory factor through its apparent impingement with the femoral trochlea at the limit of extension. The osteophyte was radically removed arthroscopically in each case as an isolated gesture, and the patients were followed up with particular emphasis on fixed flexion deformity. At clinical review, after a mean follow-up period of 5.3 years, it was concluded that there had not been a convincing or sustained improvement in knee function, although the fixed flexion deformities had not increased significantly. Our conclusion is that the 'anvil' osteophyte may simply be a part of a more diffuse degenerative process and that it was probably not, in itself, the primary cause of fixed flexion deformity in these cases.

The determinants of change in tibial plateau bone area in osteoarthritic knees: a cohort study

Bone is integral to the pathogenesis of osteoarthritis (OA). Whether the bone area of the tibial plateau changes over time in subjects with knee OA is unknown. We performed a cohort study to describe this and identify factors that might influence the change. One hundred and twenty-six subjects with knee OA underwent baseline knee radiography and magnetic resonance imaging on their symptomatic knee. They were followed up with a repeatmagnetic resonance image of the same knee approximately 2 years later. The bone area of the tibial plateau was measured at baseline and follow-up. Risk factors assessed at baseline were tested for their association with change in tibial plateau bone area over time. One hundred and seventeen subjects completed the study. The medial and lateral tibial plateau bone areas increased by 2.2 ± 6.9% and 1.5 ± 4.3% per year, respectively. Being male (P = 0.001), having a higher body mass index (P = 0.002), and having a higher baseline grade of medial joint-space narrowing (P = 0.01) were all independently and positively associated with an increased rate of enlargement of bone area of the medial tibial plateau. A larger baseline bone area of the medial tibial plateau was inversely associated with the rate of increase of that area (P < 0.001). No factor examined affected the rate of increase of the bone area of the lateral tibial plateau. In subjects with established knee OA, tibial plateau bone area increases over time. The role of subchondral bone change in the pathogenesis of knee OA will need to be determined but may be one explanation for the mechanism of action of risk factors such as body mass index on knee OA.

The relationship of antiresorptive drug use to structural findings and symptoms of knee osteoarthritis

OBJECTIVE

To examine the cross-sectional association between use of medications that have a bone antiresorptive effect (estrogen, raloxifene, and alendronate) and both the structural features of knee osteoarthritis (OA), assessed by magnetic resonance imaging (MRI) and radiography, and the symptoms of knee OA in elderly women.

METHODS

Women in the Health, Aging and Body Composition Study underwent MRI and radiography of the knee if they reported symptoms of knee OA, and women without significant knee symptoms were selected as controls. MR images of the knee were assessed for multiple features of OA using the Whole-Organ MRI scoring method, and radiographs were read for Kellgren and Lawrence grade and individual features of OA. Concurrent medication use and knee symptoms were assessed by interview, and knee pain severity was evaluated using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC).

RESULTS

There were 818 postmenopausal women from whom we obtained MR images of the knee and data on medication use. Among these women, 214 (26.2%) were receiving antiresorptive drugs. We found no significant association between overall use of antiresorptive drugs and the presence of knee pain and radiographic changes of OA of the knee. Use of alendronate, but not estrogen, was associated with less severity of knee pain as assessed by WOMAC scores. Both alendronate use and estrogen use were associated with significantly less subchondral bone attrition and bone marrow edema-like abnormalities in the knee as assessed by MRI, as compared with women who had not received these medications.

CONCLUSION

Elderly women being treated with alendronate and estrogen had a significantly decreased prevalence of knee OA-related subchondral bone lesions compared with those reporting no use of these medications. Alendronate use was also associated with a reduction in knee pain according to the WOMAC scores.

Effects of calcitonin on subchondral trabecular bone changes and on osteoarthritic cartilage lesions after acute anterior cruciate ligament deficiency

Because SBM may contribute to cartilage breakdown in OA, experimental OA was induced in dogs by transecting the anterior cruciate ligament of the knee and treating with either CT or a placebo. CT significantly reduced both SBM and cartilage lesions. This study supports the use of CT in the treatment of canine experimental OA.

INTRODUCTION

Because subchondral bone remodeling (SBM) may contribute to cartilage breakdown in osteoarthritis (OA), we evaluated to what extend calcitonin (CT) might affect cartilage and bone changes in the early stages of canine experimental OA.

MATERIALS AND METHODS

Twelve dogs underwent transection of the anterior cruciate ligament (ACLT) of the right knee. After ACLT, each animal received a daily nasal spray delivering either 400 U of CT (CT-treated group; n = 6) or a placebo (PL-treated group; n = 6). At day 84 after surgery, animals were killed, and cartilage changes were graded. BMD and volume fraction (BVF) were assessed by pQCT in different regions of interest (ROIs) of the subchondral cancellous bone of tibial plateaus (TPs). Statistics included a 2 x 2 factorial analysis with +/-CT as one factor and +/-ACLT as the other.

RESULTS AND CONCLUSIONS

Nonoperated (N-OP) knees were normal in both groups. In the PL-treated group, ACLT knees all exhibited OA changes, which predominated in the medial knee compartment. Furthermore, compared with N-OP knees, the BMD and BVF of ACLT joints were both markedly reduced in medial TP but not in lateral TP. In contrast, in the CT-treated group, cartilage OA lesions of ACLT knees were significantly reduced, and there was no difference in BMD and BFV between N-OP and ACLT knees. These findings suggest that the loss of subchondral trabeculae contributes to cartilage breakdown, possibly by enhancing cartilage deformation on joint loading. By counteracting bone loss, CT reduced cartilage OA lesions, and thus, might be useful in the treatment of OA in cruciate-deficient dogs.

Microfractures and microcracks in subchondral bone: are they relevant to osteoarthrosis?

The existing data are consistent with the view that reactivation of the secondary center of ossification and not the stiffening of the metaphyseal trabecular bone is a mechanism of cartilage loss in idiopathic OA. The stiffening of the subchondral calcified structures would appear to be etiologically incidental and, as the arthrotic process progresses, sometimes locally transient. It is also now clear that although the apparent density of the subchondral cortical plate increases because of thickening of the plate as the OA process progresses, the elastic modulus of the bone might be reduced locally because of increases in vascularization and in the rate of bony remodeling subjacent to the cartilage. Microcracks in the subchondral mineralized tissues might contribute to degeneration of the hyaline cartilage by initiating vascular invasion of the calcified cartilage, leading to reactivation of the tidemark and enchondral ossification with subsequent thinning of the overlying articular cartilage. The thinning would tend to increase shear stresses at the base of the articular cartilage [38], overwhelming the ability of the cartilage to repair itself, resulting in cartilage degeneration. The pathogenesis of cartilage breakdown in OA is a biological and a mechanical process. OA can be understood only if the relationship between the mechanics and the biology is fully appreciated. Failure to properly absorb impact leads to microdamage in the subchondral plate and calcified cartilage. The authors believe that this action causes the secondary center of ossification at the tidemark to advance by enchondral ossification, leading to thickening of the mineralized tissues and thinning of the overlying hyaline articular cartilage. Microcracks will cause the initiation of targeted remodeling, accounting for the increased turnover and reduced material density of the subchondral plate. The resultant thinning of the articular cartilage might lead to initiation of further microdamage in bone and cartilage through a positive feedback mechanism, which can ultimately lead to complete loss of the articular cartilage. In this view, the mechanical overload that initiates microdamage of the subchondral bone provokes a biological response that potentiates the progression of articular cartilage damage in OA.

The role of osteophytic growth in hip osteoarthritis

We studied the appearance and frequency of the medial epiarticular osteophyte in human femoral heads. Specimens were sampled from 24 men and 31 women who underwent total hip arthroplasty. On radiography, medial epiarticular osteophytes were present in two thirds of the cases. However, histological examination revealed endochondral ossification in all. Presumably, the bone formation was preceded by the formation of canals and cavities containing vessels. Due to the ossification around these canals and cavities, the histological picture frequently featured two layers of cartilage with bone in the middle. Also in the marginal osteophytes, bone was formed by endochondral ossification. However, this bone appeared more irregular. The new bone formation most likely indicates a reactivated growth as an attempt to repair the osteoarthritic lesions rather than a process of degradation.