Bone remodelling in osteoarthritis

Halofuginone attenuates osteoarthritis by inhibition of TGF-β activity and H-type vessel formation in subchondral bone

Objectives

Examine whether osteoarthritis (OA) progression can be delayed by halofuginone in anterior cruciate ligament transection (ACLT) rodent models.

Methods

3-month-old male C57BL/6J (wild type; WT) mice and Lewis rats were randomised to sham-operated, ACLT-operated, treated with vehicle, or ACLT-operated, treated with halofuginone. Articular cartilage degeneration was graded using the Osteoarthritis Research Society International (OARSI)-modified Mankin criteria. Immunostaining, flow cytometry, RT-PCR and western blot analyses were conducted to detect relative protein and RNA expression. Bone micro CT (μCT) and CT-based microangiography were quantitated to detect alterations of microarchitecture and vasculature in tibial subchondral bone.

Results

Halofuginone attenuated articular cartilage degeneration and subchondral bone deterioration, resulting in substantially lower OARSI scores. Specifically, we found that proteoglycan loss and calcification of articular cartilage were significantly decreased in halofuginone-treated ACLT rodents compared with vehicle-treated ACLT controls. Halofuginone reduced collagen X (Col X), matrix metalloproteinase-13 and A disintegrin and metalloproteinase with thrombospondin motifs 5 (ADAMTS 5) and increased lubricin, collagen II and aggrecan. In parallel, halofuginone-attenuated uncoupled subchondral bone remodelling as defined by reduced subchondral bone tissue volume, lower trabecular pattern factor (Tb.pf) and increased thickness of subchondral bone plate compared with vehicle-treated ACLT controls. We found that halofuginone exerted protective effects in part by suppressing Th17-induced osteoclastic bone resorption, inhibiting Smad2/3-dependent TGF-β signalling to restore coupled bone remodelling and attenuating excessive angiogenesis in subchondral bone.

Conclusions

Halofuginone attenuates OA progression by inhibition of subchondral bone TGF-β activity and aberrant angiogenesis as a potential preventive therapy for OA.

Repeated exposure to high-frequency low-amplitude vibration induces degeneration of murine intervertebral discs and knee joints

OBJECTIVE

High-frequency, low-amplitude whole-body vibration (WBV) is being used to treat a range of musculoskeletal disorders; however, there is surprisingly limited knowledge regarding its effect(s) on joint tissues. This study was undertaken to examine the effects of repeated exposure to WBV on bone and joint tissues in an in vivo mouse model.

METHODS

Ten-week-old male mice were exposed to vertical sinusoidal vibration under conditions that mimic those used clinically in humans (30 minutes per day, 5 days per week, at 45 Hz with peak acceleration at 0.3g). Following WBV, skeletal tissues were examined by micro-computed tomography, histologic analysis, and immunohistochemistry, and gene expression was quantified using real-time polymerase chain reaction.

RESULTS

Following 4 weeks of WBV, intervertebral discs showed histologic hallmarks of degeneration in the annulus fibrosus, disruption of collagen organization, and increased cell death. Greater Mmp3 expression in the intervertebral disc, accompanied by enhanced collagen and aggrecan degradation, was found in mice exposed to WBV as compared to controls. Examination of the knee joints after 4 weeks of WBV revealed meniscal tears and focal damage to the articular cartilage, changes resembling osteoarthritis. Moreover, mice exposed to WBV also demonstrated greater Mmp13 gene expression and enhanced matrix metalloproteinase-mediated collagen and aggrecan degradation in articular cartilage as compared to controls. No changes in trabecular bone microarchitecture or density were detected in the proximal tibia.

CONCLUSION

Our experiments reveal significant negative effects of WBV on joint tissues in a mouse model. These findings suggest the need for future studies of the effects of WBV on joint health in humans.

Efficacy study of two novel hyaluronic acid-based formulations for viscosupplementation therapy in an early osteoarthrosic rabbit model

Viscosupplementation (VS) is a therapy for osteoarthrosis (OA) consisting of repetitive intra-articular injections of hyaluronic acid (HA). It is known to be clinically effective in relieving pain and increasing joint mobility by restoring joint homeostasis. In this study, the effects of two novel HA-based VS hydrogel formulations were assessed and challenged against a pure HA commercial formulation for the first time and this in a rabbit model of early OA induced by anterior cruciate ligament transection (ACLT). The first formulation tested was a hybrid hydrogel composed of HA and reacetylated chitosan, a biopolymer considered to be chondroprotective, assembled thanks to an ionic shielding. The second formulation consisted of a novel HA polymer grafted with antioxidant molecules (HA-4AR) aiming at decreasing OA oxidative stress and increasing HA retention time in the articulation. ACLT was performed on rabbits in order to cause structural changes comparable to traumatic osteoarthrosis. The protective effects of the different formulations were observed on the early phase of the pathology in a full randomized and blinded manner. The cartilage, synovial membrane, and subchondral bone were evaluated by complementary investigation techniques such as gross morphological scoring, scanning electron microscopy, histological scoring, and micro-computed tomography were used. In this study, ACLT was proven to successfully reproduce early OA articular characteristics found in humans. HA and HA-4AR hydrogels were found to be moderately protective for cartilage as highlighted by μCT. The HA-4AR was the only formulation able to decrease synovial membrane hypertrophy occurring in OA. Finally, the hybrid HA-reacetylated chitosan hydrogel surprisingly led to increased subchondral bone remodeling and cartilage defect formation. This study shows significant effects of two innovative HA modification strategies in an OA rabbit model, which warrant further studies toward more effective viscosupplementation formulations.

The type 2 cannabinoid receptor regulates susceptibility to osteoarthritis in mice

OBJECTIVE

Cannabinoid receptors and their ligands have been implicated in the regulation of various physiological processes but their role in osteoarthritis has not been investigated. The aim of this study was to evaluate the role of the type 2 cannabinoid receptor (Cnr2) in regulating susceptibility to osteoarthritis in mice.

METHODS

We analysed the severity of knee osteoarthritis as assessed by the Osteoarthritis Research Society International (OARSI) scoring system in mice with targeted deletion of Cnr2 (Cnr2(-/-)) and wild type (WT) littermates. Studies were conducted in mice subjected to surgical destabilisation of the medial meniscus (DMM) and in those with spontaneous age-related osteoarthritis (OA).

RESULTS

Osteoarthritis was more severe following DMM in the medial compartment of the knee in Cnr2(-/-) compared with WT mice (mean ± sem score = 4.9 ± 0.5 vs 3.6 ± 0.3; P = 0.017). Treatment of WT mice with the CB2-selective agonist HU308 following DMM reduced the severity of OA in the whole joint (HU308 = 8.4 ± 0.2 vs vehicle = 10.4 ± 0.6; P = 0.007). Spontaneous age related osteoarthritis was also more severe in the medial compartment of the knee in 12-month old Cnr2(-/-) mice compared with WT (5.6 ± 0.5 vs 3.5 ± 0.3, P = 0.008). Cultured articular chondrocytes from Cnr2(-/-) mice produced less proteoglycans in vitro than wild type chondrocytes.

CONCLUSION

These studies demonstrate that the Cnr2 pathway plays a role in the pathophysiology of osteoarthritis in mice and shows that pharmacological activation of CB2 has a protective effect. Further studies of the role of cannabinoid receptors in the pathogenesis of osteoarthritis in man are warranted.

β2-Adrenergic signal transduction plays a detrimental role in subchondral bone loss of temporomandibular joint in osteoarthritis

The present study tested whether activation of the sympathetic tone by aberrant joint loading elicits abnormal subchondral bone remodeling in temporomandibular joint (TMJ) osteoarthritis. Abnormal dental occlusion was created in experimental rats, which were then intraperitoneally injected by saline, propranolol or isoproterenol. The norepinephrine contents, distribution of sympathetic nerve fibers, expression of β-adrenergic receptors (β-ARs) and remodeling parameters in the condylar subchondral bone were investigated. Mesenchymal stem cells (MSCs) from condylar subchondral bones were harvested for comparison of their β-ARs, pro-osteoclastic gene expressions and pro-osteoclastic function. Increases in norepinephrine level, sympathetic nerve fiber distribution and β2-AR expression were observed in the condylar subchondral bone of experimental rats, together with subchondral bone loss and increased osteoclast activity. β-antagonist (propranolol) suppressed subchondral bone loss and osteoclast hyperfunction while β-agonist (isoproterenol) exacerbated those responses. MSCs from experimental condylar subchondral bone expressed higher levels of β2-AR and RANKL; norepinephrine stimulation further increased their RANKL expression and pro-osteoclastic function. These effects were blocked by inhibition of β2-AR or the PKA pathway. RANKL expression by MSCs decreased after propranolol administration and increased after isoproterenol administration. It is concluded that β2-AR signal-mediated subchondral bone loss in TMJ osteoarthritisis associated with increased RANKL secretion by MSCs.

Bone mineral density distribution in the proximal femur and its relationship to morphologic factors in progressed unilateral hip osteoarthritis

Although an adverse relationship between osteoporosis and osteoarthritis (OA) has been reported, it remains controversial. In most previous reports of OA, bone mineral density (BMD) changes in the subtrochanteric region have not been clarified, whilst BMD of the femoral neck and trochanteric region has been well investigated. In our current study, we investigated the BMD ratio compared to the contralateral side in the whole proximal femurs of hip OA patients. We aimed to clarify the morphologic factor that may influence these BMD ratios. We performed dual energy X-ray absorptiometry (DEXA) analysis of 69 hip joints from unilateral progressed OA cases. The minimum joint space, center edge angle, Sharp angle, acetabular head index, neck-shaft angle, and leg length discrepancy were also measured as radiographic factors. The correlation between BMD ratio and radiographic morphologic factors was then evaluated by logistic regression. The BMD ratio was higher in the femoral neck than in the distal region. In terms of radiographic factors, the neck-shaft angle was revealed to influence the decreased BMD ratio in the distal subtrochanteric part, whilst the leg length discrepancy and Sharp angle showed a relationship with the increased BMD ratio in the proximal neck region. The discrepancy in the BMD ratio between the femoral neck and the distal subtrochanteric region in the proximal femur is influenced by several morphologic factors.

DXA in the assessment of subchondral bone mineral density in knee osteoarthritis--A semi-standardized protocol after systematic review

INTRODUCTION

Subchondral bone mineral density (sBMD) contributes to the initiation and progression of knee osteoarthritis (OA). Reliable methods to assess sBMD status may predict the response of specific OA phenotypes to targeted therapies. While dual-energy X-ray absorptiometry (DXA) of the knee can determine sBMD, no consensus exists regarding its methodology.

OBJECTIVE

Construct a semi-standardized protocol for knee DXA to measure sBMD in patients with OA of the knee by evaluating the varying methodologies present in existing literature.

METHODS

We performed a systematic review of original papers published in PubMed and Web of Science from their inception to July 2014 using the following search terms: subchondral bone, osteoarthritis, and bone mineral density.

RESULTS

DXA of the knee can be performed with similar reproducibility values to those proposed by the International Society for Clinical Densitometry for the hip and spine. We identified acquisition view, hip rotation, knee positioning and stabilization, ROI location and definition, and the type of analysis software as important sources of variation. A proposed knee DXA protocol was constructed taking into consideration the results of the review.

CONCLUSIONS

DXA of the knee can be reliably performed in patients with knee OA. Nevertheless, we found substantial methodological variation across previous studies. Methodological standardization may provide a foundation from which to establish DXA of the knee as a valid tool for identification of SB changes and as an outcome measure in clinical trials of disease modifying osteoarthritic drugs.

Possible role of methylglyoxal and glyoxalase in arthritis

OA (osteoarthritis) and RA (rheumatoid arthritis) lead to deterioration of the joints. Early OA is associated with loss of bone due to increased bone remodelling. A role for inflammation is thought to be integral to the pathology. RA is a chronic inflammatory disease of the synovium, a membrane lining the non-weight-bearing surfaces of the joint. The mainstay of RA diagnostic testing is for autoantibodies. Rheumatoid factor has been a primary diagnostic test; however, sensitivity is approximately 75%, but specificity is limited. Recently, detection of antibodies against cyclic citrullinated peptide, identified as a screening marker and marker of disease progression, has been proposed. Studies of glycation in arthritis have focused mostly on levels of AGEs (advanced glycation end-products), Nε-carboxymethyl-lysine and pentosidine. There was a weak correlation of skin and urinary pentosidine with joint damage in early-stage OA. RAGE (receptor for AGEs) is a cell-surface receptor in the synovial tissue of patients with OA and RA. The RAGE agonist S100A12 is increased in RA and OA. Activation of RAGE may decrease expression of Glo1 (glyoxalase I). Conflict between RAGE-activated inflammatory signalling and Nrf2 (nuclear factor-erythroid 2-related factor 2) regulation of basal and inducible expression of Glo1 may be involved. Thereby glyoxal- and methylglyoxal-derived AGEs may be increased in OA and RA. Further studies are now required to investigate the role of glyoxalase and dicarbonyl glycation in OA and RA for early-stage diagnosis and potential novel preventive therapy.

Use of 18F-fluoride positron emission tomography as a predictor of the hip osteoarthritis progression

OBJECTIVE

The prediction of hip osteoarthritis (OA) progression is still a difficult issue. We have adopted (18)F-fluoride positron emission tomography (PET) for the evaluation of hip osteoarthritis, and investigated the prediction utility of (18)F-fluoride PET for both pain worsening and OA progression using a logistic regression model.

MATERIALS AND METHODS

A total of 57 hip joints were analyzed for progression risk factors for pain worsening and minimum joint space (MJS) narrowing by logistic regression analysis. Sex, age, BMI, existence of pain, the PET maximum standardized uptake value (SUV(max)), Kellgren and Lawrence grade, MJS, and follow-up period were used as explanatory variables. Receiver operating characteristic analysis was performed to calculate the cutoff value of the SUV(max).

RESULTS

Multivariate logistic regression analysis revealed significant differences only in the SUV(max) values for pain worsening and MJS narrowing. The odds ratio of the SUV(max) for pain worsening was 1.89, and for MJS narrowing it was 11.02. The SUV(max) cutoff value was 7.2 (sensitivity: 1.00, specificity: 0.84) for pain worsening and 6.4 (sensitivity: 0.92, specificity: 0.83) for MJS narrowing.

CONCLUSIONS

Our results indicate that the PET SUV(max) is a best predictor of pain worsening and MJS narrowing. This imaging modality has a great potential for the prediction of OA progression.

SCFβ-TRCP regulates osteoclastogenesis via promoting CYLD ubiquitination

CYLD negatively regulates the NF-κB signaling pathway and osteoclast differentiation largely through antagonizing TNF receptor-associated factor (TRAF)-mediated K63-linkage polyubiquitination in osteoclast precursor cells. CYLD activity is controlled by IκB kinase (IKK), but the molecular mechanism(s) governing CYLD protein stability remains largely undefined. Here, we report that SCF^β-TRCP regulates the ubiquitination and degradation of CYLD, a process dependent on prior phosphorylation of CYLD at Ser432/Ser436 by IKK. Furthermore, depletion of β-TRCP induced CYLD accumulation and TRAF6 deubiquitination in osteoclast precursor cells, leading to suppression of RANKL-induced osteoclast differentiation. Therefore, these data pinpoint the IKK/β-TRCP/CYLD signaling pathway as an important modulator of osteoclastogenesis.

Histopathological features of hypertrophic bone mass of temporomandibular joint ankylosis (TMJA): An explanation of pathogenesis of TMJA

Temporomandibular joint ankylosis (TMJA) is a severe organic disease with progressive limitation of the mouth opening. Histopathologically, a residual joint space is reported to consist of fibrous tissue and/or cartilage, indicating two types of interface (osteo-fibrous and osteo-chondral) of residual joint space. It is well known that adverse mechanical stress results in pathological changes of osteoarthritis and enthesopathy in these interfaces. What would happen pathologically in these interfaces of TMJA under repeated mandible movement has not been elucidated. Fourteen tissue samples of residual joint space and temporal and condylar bone were stained with hematoxylin and eosin and evaluated by collagen I and II immunohistochemistry. A pathological study of 14 TMJA patients showed that the residual joint space presented a fibrocartilage entheses structure and an articular cartilage structure. Moreover, these two structures were associated with pathological alterations of both osteoarthritis and enthesopathy, including degenerated and necrotized tissue, chondrocyte cloning, crack and fissure, various bone scleroses, and inflammatory granulation tissue. It is suggested that the pathological alterations of both osteoarthritis and enthesopathy occurred in TMJA, which hints at mechanical stress on TMJA development.

Endogenous parathyroid hormone and knee osteoarthritis: a cross-sectional study

AIM

Although animal studies have shown that parathyroid hormone (PTH) analogs can have disease-modifying effect on experimental osteoarthritis, there is little human data. This study aimed to analyze the association between endogenous PTH and knee osteoarthritis in humans.

METHODS

This was a cross-sectional study including 5880 participants of The Fifth Korean National Health and Nutrition Examination Survey. Serum intact PTH was measured by chemiluminescence assay. Radiographic knee osteoarthritis was defined as a Kellgren-Lawrence grade of ≥ 2. The association between knee osteoarthritis and natural log-transformed PTH (lnPTH) was modeled using logistic regression analyses adjusting for age, body mass index categories, calcium intake and serum 25-hydroxyvitamin D in both sexes.

RESULTS

The prevalence of radiographic knee osteoarthritis tended to be higher in the highest quartile of PTH in women. In men, there was no clear trend across the quartiles of PTH. In multivariable analyses, there was no significant association between lnPTH and radiographic knee osteoarthritis in either sex (odds ratio [95% confidence interval]): 0.81 (0.64-1.02) in women and 0.88 (0.67-1.16) in men. Analyses on symptomatic radiographic knee osteoarthritis showed no significant association.

CONCLUSION

Although there was a trend for a negative association in women, no statistically significant association was found between endogenous PTH and knee osteoarthritis.

Emerging targets in osteoarthritis therapy

Osteoarthritis (OA) is a destructive joint disease in which the initiation may be attributed to direct injury and mechanical disruption of joint tissues, but the progressive changes are dependent on active cell-mediated processes that can be observed or inferred during the generally long time-course of the disease. Based on clinical observations and experimental studies, it is now recognized a that it is possible for individual patients to exhibit common sets of symptoms and structural abnormalities due to distinct pathophysiological pathways that act independently or in combination. Recent research that has focused on the underlying mechanisms involving biochemical cross talk among the cartilage, synovium, bone, and other joint tissues within a background of poorly characterized genetic factors will be addressed in this review.

Glenoid subchondral bone density distribution in male total shoulder arthroplasty subjects with eccentric and concentric wear

BACKGROUND

Glenoid component loosening in total shoulder arthroplasty may be prevented by component placement on a congruent and adequate bony surface. Glenoid subchondral bone density (SBD) variability may be correlated with this concept. This study analyzed the 3-dimensional distribution of glenoid SBD in total shoulder arthroplasty patients with osteoarthritis.

MATERIALS AND METHODS

Three-dimensional computed tomography osteoabsorptiometry (CT-OAM) was performed in 42 men (21 with eccentric and 21 with concentric wear patterns) with glenohumeral arthritis. Glenoid SBD was measured from the joint surface based on 5 clinically relevant topographic zones. The correlation of the wear pattern with the SBD distribution was investigated.

RESULTS

The glenoid subarticular layers could be separated into distinct regions: calcified cartilage (≤ 1.5 mm), subchondral plate (2-4.5 mm) and cancellous bone (≥ 5 mm). There were significant differences in SBD among these layers within and between patients with concentric and eccentric wear patterns. In concentric glenoids, the SBD distribution was homogeneous, with greater mineralization in the central zone, 1,749.1 ± 162.3 Hounsfield units (HU) (at 2.5 mm), compared with the posterior, anterior, and superior zones (P < .001). In the eccentric group, the SBD distribution was inhomogeneous. Mineralization was greatest in the posterior zone, 1,739.0 ± 172.6 HU (at 2.5 mm), followed by the inferior zone, 1,722.1 ± 186.6 HU (at 3 mm).

CONCLUSION

This study represents the first study using CT-OAM to evaluate the 3-dimensional SBD distribution of the glenoid vault for different arthritic wear patterns. The study findings indicate that the SBD distribution is dependent on (1) depth from the articular surface, (2) topographic zone, and (3) wear pattern. CT-OAM may be an effective tool to assist in preoperative planning for shoulder arthroplasty.

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.

Adult mice lacking the type 2 iodothyronine deiodinase have increased subchondral bone but normal articular cartilage

BACKGROUND

Although osteoarthritis (OA) is the commonest joint disorder and has a rising prevalence as the population ages, no drugs are available that prevent or delay the onset and progression of disease. Recent studies identified the DIO2 gene encoding type 2 deiodinase (D2) as a susceptibility locus for OA, and further data suggest deiodinase-regulated local availability of triiodothyronine (T3) in the joint plays an important role in cartilage maintenance and repair. To investigate the hypothesis that reduced tissue T3 availability protects joints from development of OA, the joint phenotypes of adult mice lacking D2 (D2KO) or lacking both D1 and D2 (D1D2KO), the only enzymes that catalyze conversion of the prohormone thyroxine to active T3, were determined.

METHODS

Knee joints were prepared from male 16-week-old adult wild type (WT; n=9), D2KO (n=5), and D1D2KO (n=3) mice. Articular cartilage pathology was scored using the Osteoarthritis Research Society International (OARSI) histopathology scale for murine OA to determine the severity and extent of disease. Digital X-ray microradiography was used to determine the area and mineral content of subchondral bone immediately beneath the articular cartilage surface.

RESULTS

There were no differences in maximum and standardized OA scores, cartilage erosion indices, or articular cartilage cellularity among WT, D2KO, and D1D2KO mice. Subchondral bone area did not differ among genotypes, but mineral content was markedly increased in both D2KO and D1D2KO mice compared to WT.

CONCLUSIONS

Although adult D2KO mice have normal articular cartilage and no other features of spontaneous joint damage, they exhibit increased subchondral bone mineral content.

Effect of alendronate on post-traumatic osteoarthritis induced by anterior cruciate ligament rupture in mice

Introduction

Previous studies in animal models of osteoarthritis suggest that alendronate (ALN) has antiresorptive and chondroprotective effects, and can reduce osteophyte formation. However, these studies used non-physiologic injury methods, and did not investigate early time points during which bone is rapidly remodeled prior to cartilage degeneration. The current study utilized a non-invasive model of knee injury in mice to investigate the effect of ALN treatment on subchondral bone changes, articular cartilage degeneration, and osteophyte formation following injury.

Methods

Non-invasive knee injury via tibial compression overload or sham injury was performed on a total of 90 mice. Mice were treated with twice weekly subcutaneous injections of low-dose ALN (40 μg/kg/dose), high-dose ALN (1,000 μg/kg/dose), or vehicle, starting immediately after injury until sacrifice at 7, 14 or 56 days. Trabecular bone of the femoral epiphysis, subchondral cortical bone, and osteophyte volume were quantified using micro-computed tomography (μCT). Whole-joint histology was performed at all time points to analyze articular cartilage and joint degeneration. Blood was collected at sacrifice, and serum was analyzed for biomarkers of bone formation and resorption.

Results

μCT analysis revealed significant loss of trabecular bone from the femoral epiphysis 7 and 14 days post-injury, which was effectively prevented by high-dose ALN treatment. High-dose ALN treatment was also able to reduce subchondral bone thickening 56 days post-injury, and was able to partially preserve articular cartilage 14 days post-injury. However, ALN treatment was not able to reduce osteophyte formation at 56 days post-injury, nor was it able to prevent articular cartilage and joint degeneration at this time point. Analysis of serum biomarkers revealed an increase in bone resorption at 7 and 14 days post-injury, with no change in bone formation at any time points.

Conclusions

High-dose ALN treatment was able to prevent early trabecular bone loss and cartilage degeneration following non-invasive knee injury, but was not able to mitigate long-term joint degeneration. These data contribute to understanding the effect of bisphosphonates on the development of osteoarthritis, and may support the use of anti-resorptive drugs to prevent joint degeneration following injury, although further investigation is warranted.

Loss of sclerostin promotes osteoarthritis in mice via β-catenin-dependent and -independent Wnt pathways

Introduction

Sclerostin is a Wnt inhibitor produced by osteocytes that regulates bone formation. Because bone tissue contributes to the development of osteoarthritis (OA), we investigated the role of sclerostin in bone and cartilage in a joint instability model in mice.

Methods

Ten-week-old SOST-knockout (SOST-KO) and wild-type (WT) mice underwent destabilization of the medial meniscus (DMM). We measured bone volume at the medial femoral condyle and osteophyte volume and determined the OA score and expression of matrix proteins. Primary murine chondrocytes were cultured with Wnt3a and sclerostin to assess the expression of matrix proteins, proteoglycan release and glycosaminoglycan accumulation.

Results

Sclerostin was expressed in calcified cartilage of WT mice with OA. In SOST-KO mice, cartilage was preserved despite high bone volume. However, SOST-KO mice with DMM had a high OA score, with increased expression of aggrecanases and type X collagen. Moreover, SOST-KO mice with OA showed disrupted anabolic–catabolic balance and cartilage damage. In primary chondrocytes, sclerostin addition abolished Wnt3a-increased expression of a disintegrin and metalloproteinase with thrombospondin motifs, matrix metalloproteinases and type X collagen by inhibiting the canonical Wnt pathway. Moreover, sclerostin inhibited Wnt-phosphorylated c-Jun N-terminal kinase (JNK) and rescued the expression of anabolic genes. Furthermore, sclerostin treatment inhibited both Wnt canonical and non-canonical JNK pathways in chondrocytes, thus preserving metabolism.

Conclusion

Sclerostin may play an important role in maintaining cartilage integrity in OA.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-015-0540-6) contains supplementary material, which is available to authorized users.

Osteoarthritis and bone mineral density: are strong bones bad for joints?

Osteoarthritis (OA) is a common and disabling joint disorder affecting millions of people worldwide. In OA, pathological changes are seen in all of the joint tissues including bone. Although both cross-sectional and longitudinal epidemiological studies have consistently demonstrated an association between higher bone mineral density (BMD) and OA, suggesting that increased BMD is a risk factor for OA, the mechanisms underlying this observation remain unclear. Recently, novel approaches to examining the BMD-OA relationship have included studying the disease in individuals with extreme high bone mass, and analyses searching for genetic variants associated with both BMD variation and OA, suggesting possible pleiotropic effects on bone mass and OA risk. These studies have yielded valuable insights into potentially relevant pathways that might one day be exploited therapeutically. Although animal models have suggested that drugs reducing bone turnover (antiresorptives) may retard OA progression, it remains to be seen whether this approach will prove to be useful in human OA. Identifying individuals with a phenotype of OA predominantly driven by increased bone formation could help improve the overall response to these treatments. This review aims to summarise current knowledge regarding the complex relationship between BMD and OA.

Correlation between mechanical stress by finite element analysis and 18F-fluoride PET uptake in hip osteoarthritis patients

18F-fluoride positron emission tomography (18F-fluoride PET) is a functional imaging modality used primarily to detect increased bone metabolism. Increased 18F-fluoride PET uptake suggests an association between increased bone metabolism and load stress at the subchondral level. This study therefore examined the relationship between equivalent stress distribution calculated by finite element analysis and 18F-fluoride PET uptake in patients with hip osteoarthritis. The study examined 34 hips of 17 patients who presented to our clinic with hip pain, and were diagnosed with osteoarthritis or pre-osteoarthritis. The hips with trauma, infection, or bone metastasis of cancer were excluded. Three-dimensional models of each hip were created from computed tomography data to calculate the maximum equivalent stress by finite element analysis, which was compared with the maximum standardized uptake value (SUVmax) examined by 18F-fluoride PET. The SUVmax and equivalent stress were correlated (Spearman's rank correlation coefficient ρ=0.752), and higher equivalent stress values were noted in higher SUVmax patients. The correlation between SUVmax and maximum equivalent stress in osteoarthritic hips suggests the possibility that 18F-fluoride PET detect increased bone metabolism at sites of stress concentration. This study demonstrates the correlation between mechanical stress and bone remodeling acceleration in hip osteoarthritis.

Role of Vitamin D in Osteoarthritis: Molecular, Cellular, and Clinical Perspectives

Osteoarthritis is a debilitating and degenerative disease which affects millions of people worldwide. The causes and mechanisms of osteoarthritis remain to be fully understood. Vitamin D has been hypothesised to play essential roles in a number of diseases including osteoarthritis. Many cell types within osteoarthritic joints appear to experience negative effects often at increased sensitivity to vitamin D. These findings contrast clinical research which has identified vitamin D deficiency to have a worryingly high prevalence among osteoarthritis patients. Randomised-controlled trial is considered to be the most rigorous way of determining the effects of vitamin D supplementation on the development of osteoarthritis. Studies into the effects of low vitamin D levels on pain and joint function have to date yielded controversial results. Due to the apparent conflicting effects of vitamin D in knee osteoarthritis, further research is required to fully elucidate its role in the development and progression of the disease as well as assess the efficacy and safety of vitamin D supplementation as a therapeutic strategy.

Quantitative proteomic profiling of human articular cartilage degradation in osteoarthritis

Osteoarthritis (OA) is the most common rheumatic pathology and is characterized primarily by articular cartilage degradation. Despite its high prevalence, there is no effective therapy to slow disease progression or regenerate the damaged tissue. Therefore, new diagnostic and monitoring tests for OA are urgently needed, which would also promote the development of alternative therapeutic strategies. In the present study, we have performed an iTRAQ-based quantitative proteomic analysis of secretomes from healthy human articular cartilage explants, comparing their protein profile to those from unwounded (early disease) and wounded (advanced disease) zones of osteoarthritic tissue. This strategy allowed us to identify a panel of 76 proteins that are distinctively released by the diseased tissue. Clustering analysis allowed the classification of proteins according to their different profile of release from cartilage. Among these proteins, the altered release of osteoprotegerin (decreased in OA) and periostin (increased in OA), both involved in bone remodelling processes, was verified in further analyses. Moreover, periostin was also increased in the synovial fluid of OA patients. Altogether, the present work provides a novel insight into the mechanisms of human cartilage degradation and a number of new cartilage-characteristic proteins with possible biomarker value for early diagnosis and prognosis of OA.

Subchondral bone in osteoarthritis: insight into risk factors and microstructural changes

Osteoarthritis (OA) is a major cause of disability in the adult population. As a progressive degenerative joint disorder, OA is characterized by cartilage damage, changes in the subchondral bone, osteophyte formation, muscle weakness, and inflammation of the synovium tissue and tendon. Although OA has long been viewed as a primary disorder of articular cartilage, subchondral bone is attracting increasing attention. It is commonly reported to play a vital role in the pathogenesis of OA. Subchondral bone sclerosis, together with progressive cartilage degradation, is widely considered as a hallmark of OA. Despite the increase in bone volume fraction, subchondral bone is hypomineralized, due to abnormal bone remodeling. Some histopathological changes in the subchondral bone have also been detected, including microdamage, bone marrow edema-like lesions and bone cysts. This review summarizes basic features of the osteochondral junction, which comprises subchondral bone and articular cartilage. Importantly, we discuss risk factors influencing subchondral bone integrity. We also focus on the microarchitectural and histopathological changes of subchondral bone in OA, and provide an overview of their potential contribution to the progression of OA. A hypothetical model for the pathogenesis of OA is proposed.

Genome-wide expression profiles of subchondral bone in osteoarthritis

Introduction

The aim of this study was to evaluate, for the first time, the differences in gene expression profiles of normal and osteoarthritic (OA) subchondral bone in human subjects.

Methods

Following histological assessment of the integrity of overlying cartilage and the severity of bone abnormality by micro-computed tomography, we isolated total RNA from regions of interest from human OA (n = 20) and non-OA (n = 5) knee lateral tibial (LT) and medial tibial (MT) plateaus. A whole-genome profiling study was performed on an Agilent microarray platform and analyzed using Agilent GeneSpring GX11.5. Confirmatory quantitative reverse-transcription polymerase chain reaction (qRT-PCR) analysis was performed on samples from 9 OA individuals to confirm differential expression of 85 genes identified by microarray. Ingenuity Pathway Analysis (IPA) was used to investigate canonical pathways and immunohistochemical staining was performed to validate protein expression levels in samples.

Results

A total of 972 differentially expressed genes were identified (fold change ≥ ± 2, P ≤0.05) between LT (minimal degeneration) and MT (significant degeneration) regions from OA samples; these data implicated 279 canonical pathways in IPA. The qRT-PCR data strongly confirmed the accuracy of microarray results (R² = 0.58, P <0.0001). Novel pathways were identified in this study including Periostin (POSTN) and Leptin (LEP), which are implicated in bone remodeling by osteoblasts.

Conclusions

To the best of our knowledge, this study represents the most comprehensive direct assessment to date of gene expression profiling in OA subchondral bone. This study provides insights that could contribute to the development of new biomarkers and therapeutic strategies for OA.

Hypoxia and vitamin D differently contribute to leptin and dickkopf-related protein 2 production in human osteoarthritic subchondral bone osteoblasts

Introduction

Bone remodelling and increased subchondral densification are important in osteoarthritis (OA). Modifications of bone vascularization parameters, which lead to ischemic episodes associated with hypoxic conditions, have been suspected in OA. Among several factors potentially involved, leptin and dickkopf-related protein 2 (DKK2) are good candidates because they are upregulated in OA osteoblasts (Obs). Therefore, in the present study, we investigated the hypothesis that hypoxia may drive the expression of leptin and DKK2 in OA Obs.

Methods

Obs from the sclerotic portion of OA tibial plateaus were cultured under either 20% or 2% oxygen tension in the presence or not of 50 nM 1,25-dihydroxyvitamin D₃ (VitD₃). The expression of leptin, osteocalcin, DKK2, hypoxia-inducible factor 1α (Hif-1α) and Hif-2α was measured by real-time polymerase chain reaction and leptin production was measured by enzyme-linked immunosorbent assay (ELISA). The expression of Hif-1α, Hif-2α, leptin and DKK2 was reduced using silencing RNAs (siRNAs). The signalling pathway of hypoxia-induced leptin was investigated by Western blot analysis and with mitogen-activated protein kinase (MAPK) inhibitors.

Results

The expression of leptin and DKK2 in Obs was stimulated 7-fold and 1.8-fold, respectively (P <0.05) under hypoxia. Interestingly, whereas VitD₃ stimulated leptin and DKK2 expression 2- and 4.2-fold, respectively, under normoxia, it stimulated their expression by 28- and 6.2-fold, respectively, under hypoxia (P <0.05). The hypoxia-induced leptin production was confirmed by ELISA, particularly in the presence of VitD₃ (P <0.02). Compared to Obs incubated in the presence of scramble siRNAs, siHif-2α inhibited VitD₃-stimulated leptin mRNA and protein levels by 70% (P =0.004) and 60% (P <0.02), respectively, whereas it failed to significantly alter the expression of DKK2. siHif-1α has no effect on these genes. Immunoblot analysis showed that VitD₃ greatly stabilized Hif-2α under hypoxic conditions. The increase in leptin expression under hypoxia was also regulated, by p38 MAPK (P <0.03) and phosphoinositide 3-kinase (P <0.05). We found that the expression of leptin and DKK2 were not related to each other under hypoxia.

Conclusions

Hypoxic conditions via Hif-2 regulation trigger Obs to produce leptin, particularly under VitD₃ stimulation, whereas DKK2 is regulated mainly by VitD₃ rather than hypoxia.

The Pathophysiology and Progression of Hip Osteoarthritis Accompanied with Joint Pain are Potentially Due to Bone Alterations - Follow-up Study of Hip OA Patients

OBJECTIVES

This study examined hip osteoarthritis (OA) patients with joint pain and accompanying signal changes detected by magnetic resonance imaging (MRI).

METHODS

A total of 19 hip OA patients with suddenly occurring or worsening pain regardless of Kellgren-Lawrence grading were enrolled. The patients were monitored using MRI, plain radiographs, and the Denis pain scale for a minimum of 6 months. The patients were classified into 2 groups: those whose pain improved during conservative treatment (Group A) and those whose pain persisted (Group B).

RESULTS

Joint pain disappeared or was markedly improved in all 10 cases in Group A. Radiographic OA progression occurred in 7 of 8 cases with available radiographs. Hip MRI was performed on 7 of 10 patients, among whom bone signal changes disappeared in 6 patients. One patient exhibited persisting bone signal alterations although joint pain had completely disappeared. In Group B, joint pain remained in all 9 cases. Radiographic OA progression occurred in 8 of 9 cases, and local (4 cases) or broad (5 cases) bone signal alterations were present in end-point MRI examinations. Two patients exhibited different regional MRI bone signal changes (local or broad) at the end of follow-up. The mean age of Group B was significantly higher than that of Group A.

CONCLUSION

THIS STUDY UNCOVERED THE FOLLOWING OBSERVATIONS: 1) hip OA with joint pain had bone alterations that were detectable by MRI, 2) these bone alterations disappeared when joint pain improved, 3) bone alterations remained when joint pain continued, and 4) radiographic OA progressed to a more advanced stage over a short time period. These findings indicate that the pathophysiology of OA, joint pain, and OA progression may primarily be due to bone changes.

Quantitative X-ray microradiography for high-throughput phenotyping of osteoarthritis in mice

OBJECTIVE

To investigate and validate digital X-ray microradiography as a novel, high-throughput and cost-effective screening approach to identify abnormal joint phenotypes in mice.

METHOD

Digital X-ray microradiography was used to quantify the subchondral bone mineral content (BMC) in the medial tibial plateau. Accuracy and reproducibility of the method were determined in 22 samples from C57BL/6(B6Brd;B6Dnk;B6N-Tyr(c-Brd)) wild-type mice. The method was then validated in wild-type mice that had undergone surgical destabilisation of medial meniscus (DMM) and in a genetically modified mouse strain with an established increase in trabecular bone mass.

RESULTS

The measurement of subchondral BMC by digital X-ray microradiography had a coefficient of variation of 3.6%. Digital X-ray microradiography was able to demonstrate significantly increased subchondral BMC in the medial tibial plateau of male mice 4 and 8 weeks after DMM surgery and in female mice 8 weeks after surgery. Furthermore, digital X-ray microradiography also detected the increase in subchondral BMC in a genetically modified mouse strain with high trabecular bone mass.

CONCLUSION

Quantitation of subchondral BMC by digital X-ray microradiography is a rapid, sensitive and cost-effective method to identify abnormal joint phenotypes in mice of both genders at several ages.

A case with atypical clinical course diagnosed as osteoarthritis, osteonecrosis, subchondral insufficiency fracture, or rapidly destructive coxopathy

Osteonecrosis (ON), subchondral insufficiency fracture (SIF), and rapidly destructive coxopathy (RDC) are considered to be clinically different disorders despite exhibiting several overlapping features. We encountered an elderly female patient with an atypical clinical course who was radiographically diagnosed as having osteoarthritis (OA), ON, SIF, and/or RDC over a long-term follow-up. In this case, radiographic diagnosis was apparently affected by the timing of imaging evaluation and was challenging because of radiographic overlap and atypical disease progression. The disorders of OA, SIF, ON, and RDC might share a similar pathophysiology.

Hypoxia modulates the phenotype of osteoblasts isolated from knee osteoarthritis patients, leading to undermineralized bone nodule formation

Objective

To investigate the role of hypoxia in the pathology of osteoarthritic (OA) bone by exploring its effect on the phenotype of isolated primary osteoblasts from patients with knee OA.

Methods

OA bone samples were collected at the time of elective joint replacement surgery for knee or hip OA. Normal bone samples were collected postmortem from cadaver donors. Primary osteoblasts were isolated from knee OA bone chips and cultured under normoxic or hypoxic (2% O₂) conditions. Alkaline phosphatase activity was quantified using an enzymatic assay, and osteopontin and prostaglandin E₂ (PGE₂) production was assayed by enzyme-linked immunosorbent assay. Total RNA was extracted from bone and osteoblasts, and gene expression was profiled by quantitative reverse transcription–polymerase chain reaction.

Results

Human OA bone tissue sections stained positively for carbonic anhydrase IX, a biomarker of hypoxia, and exhibited differential expression of genes that mediate the vasculature and blood coagulation as compared to those found in normal bone. Culture of primary osteoblasts isolated from knee OA bone under hypoxic conditions profoundly affected the osteoblast phenotype, including the expression of genes that mediate bone matrix, bone remodeling, and bone vasculature. Hypoxia also increased the expression of cyclooxygenase 2 and the production of PGE₂ by OA osteoblasts. Osteoblast expression of type II collagen α1 chain, angiopoietin-like 4, and insulin-like growth factor binding protein 1 was shown to be mediated by hypoxia-inducible factor 1α. Chronic hypoxia reduced osteoblast- mineralized bone nodule formation.

Conclusion

These findings demonstrate that hypoxia can induce pathologic changes in osteoblast functionality consistent with an OA phenotype, providing evidence that hypoxia is a key driver of OA pathology.

Bone-cartilage interface crosstalk in osteoarthritis: potential pathways and future therapeutic strategies

Currently, osteoarthritis (OA) is considered a disease of the entire joint, which is not simply a process of wear and tear but rather abnormal remodelling and joint failure of an organ. The bone-cartilage interface is therefore a functioning synergistic unit, with a close physical association between subchondral bone and cartilage suggesting the existence of biochemical and molecular crosstalk across the OA interface. The crosstalk at the bone-cartilage interface may be elevated in OA in vivo and in vitro. Increased vascularisation and formation of microcracks associated with abnormal bone remodelling in joints during OA facilitate molecular transport from cartilage to bone and vice versa. Recent reports suggest that several critical signalling pathways and biological factors are key regulators and activate cellular and molecular processes in crosstalk among joint compartments. Therapeutic interventions including angiogenesis inhibitors, agonists/antagonists of molecules and drugs targeting bone remodelling are potential candidates for this interaction. This review summarised the premise for the presence of crosstalk in bone-cartilage interface as well as the current knowledge of the major signalling pathways and molecular interactions that regulate OA progression. A better understanding of crosstalk in bone-cartilage interface may lead to development of more effective strategies for treating OA patients.

Knee osteoarthritis is associated with increased prevalence of vertebral fractures despite high systemic bone mineral density: a cross-sectional study in an Asian population

OBJECTIVES

This study aimed to evaluate the relationship between radiographic knee osteoarthritis and vertebral fractures (VFs) in an Asian population.

METHODS

This cross-sectional study involved data from 1,829 participants of the Fifth Korean National Health and Nutrition Examination Survey. Radiographic knee osteoarthritis was defined as Kellgren-Lawrence (KL) grades ≥ 2. Prevalent VF was defined as a loss of ≥ 4 cm of height from the peak height. BMD was measured using dual-energy X-ray absorptiometry, in the lumbar spine and femoral neck.

RESULTS

In both sexes, the prevalence of VFs increased with age, and was higher in the knee osteoarthritis group than in the control group (in men 13.2 % in osteoarthritis group and 7.9 % in control group; in women 27.7 % in osteoarthritis group and 14.7 % in control group). Age-adjusted BMD at the lumbar spine and femoral neck was significantly higher in the knee osteoarthritis group. In multivariable analysis, KL grade 4 was significantly associated with vertebral fractures in men. In women, there was a significant trend for a positive association between KL grades and vertebral fractures.

CONCLUSIONS

Despite high systemic BMD, knee osteoarthritis was positively associated with VFs. These results suggest that bone quality, and consequently bone strength, may be decreased at the systemic level in knee osteoarthritis.

Low magnitude high frequency vibration accelerated cartilage degeneration but improved epiphyseal bone formation in anterior cruciate ligament transect induced osteoarthritis rat model

OBJECTIVES

To evaluate the effects of low-magnitude high-frequency vibration (LMHFV) on degenerated articular cartilage and subchondral bone in anterior cruciate ligament transection (ACLT) induced osteoarthritis (OA) rat model.

METHODS

6 months old female Sprague-Dawley rats received ACLT on right knee and randomly divided into treatment and control groups. OA developed 12 weeks after surgery. LMHFV (35 Hz, 0.3 g) treatment was given 20 min/day and 5 days/week. After 6, 12 and 18 weeks, six rats of each group were sacrificed at each time point and the right knees were harvested. OA grading score, distal femur cartilage volume (CV), subchondral bone morphology, elastic modulus of cartilage and functional changes between groups were analyzed.

RESULTS

Increased cartilage degradation (higher OA grading score) and worse functional results (lower duty cycle, regular index and higher limb idleness index) were observed after LMHFV treatment (P = 0.011, 0.020, 0.012 and 0.005, respectively). CV increased after LMHFV treatment (P = 0.019). Subchondral bone density increased with OA progress (P < 0.01). Increased BV/TV, Tb.N and decreased Tb.Sp were observed in distal femur epiphysis in LMHFV treatment group (P = 0.006, 0.018 and 0.011, respectively).

CONCLUSION

LMHFV accelerated cartilage degeneration and caused further functional deterioration of OA affected limb in ACLT-induced OA rat model. In contrast, LMHFV promoted bone formation in OA affected distal femur epiphysis, but did not reverse OA progression.

PTH [1-34]-induced alterations of the subchondral bone provoke early osteoarthritis

OBJECTIVE

To test the hypothesis that changes in the subchondral bone induced by parathyroid hormone (PTH [1-34]) reciprocally affect the integrity of the articular cartilage within a naïve osteochondral unit in vivo.

DESIGN

Daily subcutaneous injections of 10 μg PTH [1-34]/kg were given to adult rabbits for 6 weeks, controls received saline. Blood samples were continuously collected to monitor renal function. The subchondral bone plate and subarticular spongiosa of the femoral heads were separately assessed by micro-computed tomography. Articular cartilage was evaluated by macroscopic and histological osteoarthritis scoring, polarized light microscopy, and immunohistochemical determination of type-I, type-II, type-X collagen contents, PTH [1-34] receptor and caspase-3 expression. Absolute and relative extents of hyaline and calcified articular cartilage layers were measured histomorphometrically. The correlation between PTH-induced changes in subchondral bone and articular cartilage was determined.

RESULTS

PTH [1-34] enhanced volume, mineral density, and trabecular thickness within the subarticular spongiosa, and increased thickness of the calcified cartilage layer (all P < 0.05). Moreover, PTH [1-34] led to cartilage surface irregularities and reduced matrix staining (both P < 0.03). These early osteoarthritic changes correlated with and were ascribed to the increased thickness of the calcified cartilage layer (P = 0.026) and enhanced mineral density of the subarticular spongiosa (P = 0.001).

CONCLUSIONS

Modifications of the subarticular spongiosa by PTH [1-34] cause broadening of the calcified cartilage layer, resulting in osteoarthritic cartilage degeneration. These findings identify a mechanism by which PTH-induced alterations of the normal subchondral bone microarchitecture may provoke early osteoarthritis.

Biomarkers of cartilage and surrounding joint tissue

The identification and clinical demonstration of efficacy and safety of osteo- and chondro-protective drugs are met with certain difficulties. During the last few decades, the pharmaceutical industry has, in the field of rheumatology, experienced disappointments associated with the development of disease modification. Today, the vast amount of patients suffering from serious, chronic joint diseases can only be offered treatments aimed at improving symptoms, such as pain and acute inflammation, and are not aimed at protecting the joint tissue. This huge, unmet medical need has been the driver behind the development of improved analytical techniques allowing better and more efficient clinical trial design, implementation and analysis. With this review, we aim to provide a brief and general overview of biochemical markers of joint tissue, with special focus on neoepitopes. Furthermore, we highlight recent studies applying biochemical markers in joint degenerative diseases. These disorders, including osteoarthritis, rheumatoid arthritis and spondyloarthropathies, are the most predominant disorders in Europe and the USA, and have enormous socioeconomical impact.

Effect of self-assembled peptide-mesenchymal stem cell complex on the progression of osteoarthritis in a rat model

PURPOSE

To evaluate the efficacy of mesenchymal stem cells (MSCs) encapsulated in self-assembled peptide (SAP) hydrogels in a rat knee model for the prevention of osteoarthritis (OA) progression.

MATERIALS AND METHODS

Nanostructured KLD-12 SAPs were used as the injectable hydrogels. Thirty-three Sprague Dawley rats were used for the OA model. Ten rats were used for the evaluation of biotin-tagged SAP disappearance. Twenty-three rats were divided into four groups: MSC (n=6), SAP (n=6), SAP-MSC (n=6), and no treatment (n=5). MSCs, SAPs, and SAP-MSCs were injected into the knee joints 3 weeks postsurgery. Histologic examination, immunofluorescent staining, measurement of cytokine levels, and micro-computed tomography analysis were conducted 6 weeks after injections. Behavioral studies were done to establish baseline measurements before treatment, and repeated 3 and 6 weeks after treatment to measure the efficacy of SAP-MSCs.

RESULTS

Concentration of biotinylated SAP at week 1 was not significantly different from those at week 3 and week 6 (P=0.565). Bone mineral density was significantly lower in SAP-MSC groups than controls (P=0.002). Significant differences in terminal deoxynucleotidyl transferase deoxyuridine triphosphate nick-end labeling staining between the control group and all other groups were observed. Caspase-8, tissue inhibitor of metalloproteinases 1, and matrix metalloproteinase 9 were diffusely stained in controls, whereas localized or minimal staining was observed in other groups. Modified Mankin scores were significantly lower in the SAP and SAP-MSC groups than in controls (P=0.001 and 0.013). Although not statistically significant, synovial inflammation scores were lower in the SAP (1.3±0.3) and SAP-MSC (1.3±0.2) groups than in controls (2.6±0.2). However, neither the cytokine level nor the behavioral score was significantly different between groups.

CONCLUSION

Injection of SAP-MSC hydrogels showed evidence of chondroprotection, as measured by the histologic grading and decreased expression of biochemical markers of inflammation and apoptosis. It also lowered subchondral bone mineral density, which can be increased by OA. This suggests that the SAP-MSC complex may have clinical potential to inhibit OA progression.

Early intra-articular injection of alendronate reduces cartilage changes and subchondral bone loss in rat temporomandibular joints after ovariectomy

This study investigated the effects of intra-articular injection of alendronate on the mandibular condyle in ovariectomized rats. Sixty rats were divided into five groups: ovariectomy with vehicle treatment alone, early alendronate treatment at ovariectomy, late alendronate treatment at 4 weeks after ovariectomy, sham-operation with vehicle treatment, and normal controls. The changes in cartilage and subchondral bone were evaluated by micro-computed tomography, histology, tartrate-resistant acid phosphatase (TRAP) staining, immunohistochemistry, and real-time quantitative polymerase chain reaction. Compared with late alendronate treatment, early alendronate treatment completely inhibited cartilage thickening (727.6±39.3 vs. 1013.3±51.6; P=0.017) and improved microstructural properties of the subchondral bone, with a higher bone volume ratio (46.4±2.5 vs. 37.5±2.1; P=0.038), trabecular thickness (47.3±1.7 vs. 34.6±1.4; P=0.029), and trabecular number (8.5±0.6 vs. 6.2±0.3; P=0.041) and lower trabecular separation (30.2±1.6 vs. 37.7±2.6; P=0.034). Fewer TRAP-positive cells (4.2±0.2 vs. 6.8±0.4; P=0.019) and a higher OPG/RANKL ratio (0.38±0.01 vs. 0.25±0.03; P=0.043) in the subchondral bone were observed in the animals with early treatment compared to late treatment or ovariectomy/vehicle treatment. In addition, early alendronate treatment blocked the up-regulation of matrix metalloproteinase (MMP)-13 expression in the chondrocytes, whereas late alendronate treatment attenuated the up-regulation of MMP-13 expression. Our results suggest the therapeutic potential of intra-articular alendronate injection in the treatment of osteoporosis-associated temporomandibular disorders.

The hallmarks of osteoarthritis and the potential to develop personalised disease-modifying pharmacological therapeutics

Osteoarthritis (OA) is an age-related condition and the leading cause of pain, disability and shortening of adult working life in the UK. The incidence of OA increases with age, with 25% of the over 50s population having OA of the knee. Despite promising preclinical data covering various molecule classes, there is regrettably at present no approved disease-modifying OA drugs (DMOADs). With the advent of next generation sequencing technologies, other therapeutic areas, in particular oncology, have experienced a paradigm shift towards defining disease by its molecular composition. This paradigm shift has enabled high resolution patient stratification and supported the emergence of personalised or precision medicines. In this review we evaluate the potential for the development of OA therapeutics to undergo a similar paradigm shift given that OA is increasingly being recognised as a heterogeneous disease affecting multiple joint tissues. We highlight the evidence for the role of these tissues in OA pathology as different "hallmarks" of OA biology and review the opportunities to identify and develop targeted disease-modifying pharmacological therapeutics. Finally, we consider whether it is feasible to expect the emergence of personalised disease-modifying medicines for patients with OA and how this might be achieved.

Targeting TGFβ signaling in subchondral bone and articular cartilage homeostasis

Osteoarthritis (OA) is the most common degenerative joint disease and no disease-modifying therapy for OA is currently available. Targeting articular cartilage alone may not be sufficient to halt this disease progression. Articular cartilage and subchondral bone act as a functional unit. Increasing evidence indicates that transforming growth factor β (TGFβ) plays a crucial role in maintaining homeostasis of both articular cartilage and subchondral bone. Activation of extracellular matrix (ECM) latent TGFβ at the appropriate time and location is a prerequisite for its function. Aberrant activation of TGFβ in the subchondral bone in response to an abnormal mechanical loading environment induces formation of osteroid islets at the onset of OA. As a result, alteration of subchondral bone structure changes the stress distribution on the articular cartilage and leads to its degeneration. Thus, inhibition of TGFβ activity in the subchondral bone may provide a new avenue of treatment for OA. In this review we will discuss the role of TGFβ in the homeostasis of articular cartilage and subchondral bone as a novel target for OA therapy.

Toward regeneration of articular cartilage

Articular cartilage is classified as permanent hyaline cartilage and has significant differences in structure, extracelluar matrix components, gene expression profile, and mechanical property from transient hyaline cartilage found in the epiphyseal growth plate. In the process of synovial joint development, articular cartilage originates from the interzone, developing at the edge of the cartilaginous anlagen, and establishes zonal structure over time and supports smooth movement of the synovial joint through life. The cascade actions of key regulators, such as Wnts, GDF5, Erg, and PTHLH, coordinate sequential steps of articular cartilage formation. Articular chondrocytes are restrictedly controlled not to differentiate into a hypertrophic stage by autocrine and paracrine factors and extracellular matrix microenvironment, but retain potential to undergo hypertrophy. The basal calcified zone of articular cartilage is connected with subchondral bone, but not invaded by blood vessels nor replaced by bone, which is highly contrasted with the growth plate. Articular cartilage has limited regenerative capacity, but likely possesses and potentially uses intrinsic stem cell source in the superficial layer, Ranvier's groove, the intra-articular tissues such as synovium and fat pad, and marrow below the subchondral bone. Considering the biological views on articular cartilage, several important points are raised for regeneration of articular cartilage. We should evaluate the nature of regenerated cartilage as permanent hyaline cartilage and not just hyaline cartilage. We should study how a hypertrophic phenotype of transplanted cells can be lastingly suppressed in regenerating tissue. Furthermore, we should develop the methods and reagents to activate recruitment of intrinsic stem/progenitor cells into the damaged site.

The future of osteoarthritis therapeutics: targeted pharmacological therapy

Osteoarthritis (OA) is one of the most common forms of degenerative joint disease and a major cause of pain and disability affecting the aging population. It is estimated that more than 20 million Americans and 35 to 40 million Europeans suffer from OA. Analgesics and non-steroidal anti-inflammatory drugs (NSAIDs) are the only therapeutic treatment options for OA. Effective pharmacotherapy for OA, capable of restoring the original structure and function of damaged cartilage and other synovial tissue, is urgently needed, and research into such disease-modifying osteoarthritis drugs (DMOADs) is in progress. This is the first of three reviews focusing on OA therapeutics. This paper provides an overview of current research into potential structure-modifying drugs and more appropriately targeted pharmacological therapy. The challenges and opportunities in this area of research and development are reviewed, covering the most up-to-date initiatives, trends, and topics.

Osteoblast-chondrocyte interactions in osteoarthritis

There is now general agreement that osteoarthritis (OA) involves all structures in the affected joint, culminating in the degradation of the articular cartilage. It is appropriate to focus particularly on the subchondral bone because characteristic changes occur in this tissue with disease progression, either in parallel, or contributing to, the loss of cartilage volume and quality. Changes in both the articular cartilage and the subchondral bone are mediated by the cells in these two compartments, chondrocytes and cells of the osteoblast lineage, respectively, whose primary roles are to maintain the integrity and function of these tissues. In addition, altered rates of bone remodeling across the disease process are due to increased or decreased osteoclastic bone resorption. In the altered mechanical and biochemical environment of a progressively diseased joint, the cells function differently and show a different profile of gene expression, suggesting direct effects of these external influences. There is also ex vivo and in vitro evidence of chemical crosstalk between the cells in cartilage and subchondral bone, suggesting an interdependence of events in the two compartments and therefore indirect effects of, for example, altered loading of the joint. It is ultimately these cellular changes that explain the altered morphology of the cartilage and subchondral bone. With respect to crosstalk between the cells in cartilage and bone, there is evidence that small molecules can transit between these tissues. For larger molecules, such as inflammatory mediators, this is an intriguing possibility but remains to be demonstrated. The cellular changes during the progression of OA almost certainly need to be considered in a temporal and spatial manner, since it is important when and where observations are made in either human disease or animal models of OA. Until recently, comparisons have been made with the assumption, for example, that the subchondral bone is behaviorally uniform, but this is not the case in OA, where regional differences of the bone are evident using magnetic resonance imaging (MRI). Nevertheless, an appreciation of the altered cell function during the progression of OA will identify new disease modifying targets. If, indeed, the cartilage and subchondral bone behave as an interconnected functional unit, normalization of cell behavior in one compartment may have benefits in both tissues.

Methanol Extract of Euchelus asper Prevents Bone Resorption in Ovariectomised Mice Model

Marine molluscs are widely distributed throughout the world and many bioactive compounds exhibiting antiviral, antitumor, antileukemic, and antibacterial activity have been reported worldwide. The present study was designed to investigate the beneficial effect of methanol extract of Euchelus asper (EAME) on estrogen deficiency induced osteoporosis in ovariectomised mice model. Forty-two female Swiss albino mice were randomly assigned into Sham operated (Sham) group and six ovariectomised (OVX) subgroups such as OVX with vehicle (OVX); OVX with estradiol (2 mg/kg/day); OVX with EAME of graded doses (25, 50, 100, and 200 mg/kg/day). Bone turnover markers like serum alkaline phosphatase (ALP), serum acid phosphatase (ACP), serum calcium, and histological investigations of tibia and uterus were analysed. Metaphyseal DNA content of the femur bone was also studied. Antiosteoclastogenic activity of EAME was examined. Administration of EAME was able to reduce the increased bone turnover markers in the ovariectomised mice. Histomorphometric analysis revealed an increase in bone trabeculation and restoration of trabecular separation by EAME treatment. Metaphyseal DNA content of the femur of the OVX mice was increased by EAME administration. EAME also showed a potent antiosteoclastogenic behaviour. Thus, the present study reveals that EAME was able to successfully reduce the estrogen deficiency induced bone loss.

The Pathophysiology of Primary Hip Osteoarthritis may Originate from Bone Alterations

Objectives:

The aim of this study was to investigate whether bone alterations detected by hip magnetic resonance imaging (MRI) were associated with subsequent primary hip OA.

Methods:

We enrolled 7 patients with hip joint pain from their first visit, at which hip joints were classified as grade 0 or I on the Kellgren-Lawrence grading scale. Plain radiographs and magnetic resonance imaging (MRI) were performed on all cases, and pain was assessed with the Denis pain scale. Average age, height, weight, body mass index, bone mineral density (L1-4), central edge angle, Sharp’s angle, and acetabular hip index were calculated.

Results:

Within two months of the onset of pain, 4 of the 7 cases showed broad bone signal changes, while 3 cases showed local signal changes in the proximal femur on hip MRI. Three to 6 months after the onset of pain, in all patients whose pain was much improved, plain radiographs showed progression to further-stage OA.

Conclusion:

Our findings suggest that bone abnormalities in the proximal femur might be involved in the pathogenesis of primary hip OA.

Nutraceuticals: potential for chondroprotection and molecular targeting of osteoarthritis

Osteoarthritis (OA) is a degenerative joint disease and a leading cause of adult disability. There is no cure for OA, and no effective treatments which arrest or slow its progression. Current pharmacologic treatments such as analgesics may improve pain relief but do not alter OA disease progression. Prolonged consumption of these drugs can result in severe adverse effects. Given the nature of OA, life-long treatment will likely be required to arrest or slow its progression. Consequently, there is an urgent need for OA disease-modifying therapies which also improve symptoms and are safe for clinical use over long periods of time. Nutraceuticals-food or food products that provide medical or health benefits, including the prevention and/or treatment of a disease-offer not only favorable safety profiles, but may exert disease- and symptom-modification effects in OA. Forty-seven percent of OA patients use alternative medications, including nutraceuticals. This review will overview the efficacy and mechanism of action of commonly used nutraceuticals, discuss recent experimental and clinical data on the effects of select nutraceuticals, such as phytoflavonoids, polyphenols, and bioflavonoids on OA, and highlight their known molecular actions and limitations of their current use. We will conclude with a proposed novel nutraceutical-based molecular targeting strategy for chondroprotection and OA treatment.