Is RANKL a potential molecular target in osteoarthritis?

OBJECTIVE: Osteoarthritis (OA) is a disease of joints, in which the bone under the articular cartilage undergoes increased remodelling activity. The question is whether a better understanding of the causes and mechanisms of bone remodelling can predict disease-modifying treatments. DESIGN: This review summarises the current understanding of the aetiology of OA, with an emphasis on events in the subchondral bone (SCB), and the cells and cytokines involved, to seek an answer to this question. RESULTS: SCB remodelling across OA changes the microstructure of the SCB, which alters the load-bearing properties of the joint and seems to have an important role in the initiation and progression of OA. Bone remodelling is tightly controlled by numerous cytokines, of which Receptor Activator of NFκB ligand (RANKL) and osteoprotegerin are central factors in almost all known bone conditions. In terms of finding therapeutic options for OA, an important question is whether controlling the rate of SCB remodelling would be beneficial. The role of RANKL in the pathogenesis and progression of OA and the effect of its neutralisation remain to be clarified. CONCLUSIONS: This review further makes the case for SCB remodelling as important in OA and for additional study of RANKL in OA, both its pathophysiological role and its potential as an OA disease target.

Microstructural and cellular characterisation of the subchondral trabecular bone in human knee and hip osteoarthritis using synchrotron tomography.

OBJECTIVE: It is unclear if different factors influence osteoarthritis (OA) progression and degenerative changes characterising OA disease in hip and knee. We investigated the difference between hip OA and knee OA at the subchondral bone (SCB) tissue and cellular level, relative to the degree of cartilage degeneration. DESIGN: Bone samples were collected from 11 patients (aged 70.4 ± 10.7years) undergoing knee arthroplasty and 8 patients (aged 62.3 ± 13.4years) undergoing hip arthroplasty surgery. Trabecular bone microstructure, osteocyte-lacunar network, and bone matrix vascularity were evaluated using synchrotron micro-CT imaging. Additionally, osteocyte density, viability, and connectivity were determined histologically. RESULTS: The associations between severe cartilage degeneration and increase of bone volume fraction (%) [- 8.7, 95% CI (-14.1, -3.4)], trabecular number (#/mm) [- 1.5, 95% CI (-0.8, -2.3)], osteocyte lacunar density (#/mm3) [4714.9; 95% CI (2079.1, 7350.6)] and decrease of trabecular separation (mm) [- 0.07, 95% CI (0.02, 0.1)] were found in both knee and hip OA. When compared to knee OA, hip OA was characterised by larger (µm3) but less spheric osteocyte lacunae [47.3; 95% CI (11.2, 83.4), - 0.04; 95% CI (-0.06, -0.02), respectively], lower vascular canal density (#/mm3) [- 22.8; 95% CI (-35.4, -10.3)], lower osteocyte cell density (#/mm2) [- 84.2; 95% CI (-102.5, -67.4)], and less senescent (#/mm2) but more apoptotic osteocytes (%) [- 2.4; 95% CI (-3.6, -1.2), 24.9; 95% CI (17.7, 32.1)], respectively. CONCLUSION: SCB from hip OA and knee OA exhibits different characteristics at the tissue and cellular levels, suggesting different mechanisms of OA progression in different joints.

A Mild Case of Autosomal Recessive Osteopetrosis Masquerading as the Dominant Form Involving Homozygous Deep Intronic Variations in the CLCN7 Gene.

Osteopetrosis is a heterogeneous group of rare hereditary diseases characterized by increased bone mass of poor quality. Autosomal-dominant osteopetrosis type II (ADOII) is most often caused by mutation of the CLCN7 gene leading to impaired bone resorption. Autosomal recessive osteopetrosis (ARO) is a more severe form and is frequently accompanied by additional morbidities. We report an adult male presenting with classical clinical and radiological features of ADOII. Genetic analyses showed no amino-acid-converting mutation in CLCN7 but an apparent haploinsufficiency and suppression of CLCN7 mRNA levels in peripheral blood mononuclear cells. Next generation sequencing revealed low-frequency intronic homozygous variations in CLCN7, suggesting recessive inheritance. In silico analysis of an intronic duplication c.595-120_595-86dup revealed additional binding sites for Serine- and Arginine-rich Splicing Factors (SRSF), which is predicted to impair CLCN7 expression. Quantitative backscattered electron imaging and histomorphometric analyses revealed bone tissue and material abnormalities. Giant osteoclasts were present and additionally to lamellar bone, and abundant woven bone and mineralized cartilage were observed, together with increased frequency and thickness of cement lines. Bone mineralization density distribution (BMDD) analysis revealed markedly increased average mineral content of the dense bone (CaMean T-score + 10.1) and frequency of bone with highest mineral content (CaHigh T-score + 19.6), suggesting continued mineral accumulation and lack of bone remodelling. Osteocyte lacunae sections (OLS) characteristics were unremarkable except for an unusually circular shape. Together, our findings suggest that the reduced expression of CLCN7 mRNA in osteoclasts, and possibly also osteocytes, causes poorly remodelled bone with abnormal bone matrix with high mineral content. This together with the lack of adequate bone repair mechanisms makes the material brittle and prone to fracture. While the skeletal phenotype and medical history were suggestive of ADOII, genetic analysis revealed that this is a possible mild case of ARO due to deep intronic mutation.

Musculoskeletal Health in the Context of Spinal Cord Injury.

PURPOSE OF REVIEW: This review assembles recent understanding of the profound loss of muscle and bone in spinal cord injury (SCI). It is important to try to understand these changes, and the context in which they occur, because of their impact on the wellbeing of SC-injured individuals, and the urgent need for viable preventative therapies. RECENT FINDINGS: Recent research provides new understanding of the effects of age and systemic factors on the response of bone to loading, of relevance to attempts to provide load therapy for bone in SCI. The rapidly growing dataset describing the biochemical crosstalk between bone and muscle, and the cell and molecular biology of myokines signalling to bone and osteokines regulating muscle metabolism and mass, is reviewed. The ways in which this crosstalk may be altered in SCI is summarised. Therapeutic approaches to the catabolic changes in muscle and bone in SCI require a holistic understanding of their unique mechanical and biochemical context.

MALDI mass spectrometry imaging of N-glycans on tibial cartilage and subchondral bone proteins in knee osteoarthritis.

Magnetic resonance imaging (MRI) is a non-invasive technique routinely used to investigate pathological changes in knee osteoarthritis (OA) patients. MRI uniquely reveals zones of the most severe change in the subchondral bone (SCB) in OA, called bone marrow lesions (BMLs). BMLs have diagnostic and prognostic significance in OA, but MRI does not provide a molecular understanding of BMLs. Multiple N-glycan structures have been observed to play a pivotal role in the OA disease process. We applied matrix-assisted laser desorption/ionization (MALDI) mass spectrometry imaging (MSI) of N-glycans to formalin-fixed paraffin-embedded (FFPE) SCB tissue sections from patients with knee OA, and liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS) was conducted on consecutive sections to structurally characterize and correlate with the N-glycans seen by MALDI-MSI. The application of this novel MALDI-MSI protocol has enabled the first steps to spatially investigate the N-glycome in the SCB of knee OA patients.

Peroxidase Enzymes Regulate Collagen Biosynthesis and Matrix Mineralization by Cultured Human Osteoblasts.

The early recruitment of inflammatory cells to sites of bone fracture and trauma is a critical determinant in successful fracture healing. Released by infiltrating inflammatory cells, myeloperoxidase (MPO) and eosinophil peroxidase (EPO) are heme-containing enzymes, whose functional involvement in bone repair has mainly been studied in the context of providing a mechanism for oxidative defense against invading microorganisms. We report here novel findings that show peroxidase enzymes have the capacity to stimulate osteoblastic cells to secrete collagen I protein and generate a mineralized extracellular matrix in vitro. Mechanistic studies conducted using cultured osteoblasts show that peroxidase enzymes stimulate collagen biosynthesis at a post-translational level in a prolyl hydroxylase-dependent manner, which does not require ascorbic acid. Our studies demonstrate that osteoblasts rapidly bind and internalize both MPO and EPO, and the catalytic activity of these peroxidase enzymes is essential to support collagen I biosynthesis and subsequent release of collagen by osteoblasts. We show that EPO is capable of regulating osteogenic gene expression and matrix mineralization in culture, suggesting that peroxidase enzymes may play an important role not only in normal bone repair, but also in the progression of pathological states where infiltrating inflammatory cells are known to deposit peroxidases.

The paired-box homeodomain transcription factor Pax6 binds to the upstream region of the TRAP gene promoter and suppresses receptor activator of NF-κB ligand (RANKL)-induced osteoclast differentiation.

Osteoclast formation is regulated by balancing between the receptor activator of nuclear factor-κB ligand (RANKL) expressed in osteoblasts and extracellular negative regulatory cytokines such as interferon-γ (IFN-γ) and interferon-ß (IFN-ß), which can suppress excessive bone destruction. However, relatively little is known about intrinsic negative regulatory factors in RANKL-mediated osteoclast differentiation. Here, we show the paired-box homeodomain transcription factor Pax6 acts as a negative regulator of RANKL-mediated osteoclast differentiation. Electrophoretic mobility shift and reporter assays found that Pax6 binds endogenously to the proximal region of the tartrate acid phosphatase (TRAP) gene promoter and suppresses nuclear factor of activated T cells c1 (NFATc1)-induced TRAP gene expression. Introduction of Pax6 retrovirally into bone marrow macrophages attenuates RANKL-induced osteoclast formation. Moreover, we found that the Groucho family member co-repressor Grg6 contributes to Pax6-mediated suppression of the TRAP gene expression induced by NFATc1. These results suggest that Pax6 interferes with RANKL-mediated osteoclast differentiation together with Grg6. Our results demonstrate that the Pax6 pathway constitutes a new aspect of the negative regulatory circuit of RANKL-RANK signaling in osteoclastogenesis and that the augmentation of Pax6 might therefore represent a novel target to block pathological bone resorption.

SaOS2 Osteosarcoma cells as an in vitro model for studying the transition of human osteoblasts to osteocytes.

The central importance of osteocytes in regulating bone homeostasis is becoming increasingly apparent. However, the study of these cells has been restricted by the relative paucity of cell line models, especially those of human origin. Therefore, we investigated the extent to which SaOS2 human osteosarcoma cells can differentiate into osteocyte-like cells. During culture under the appropriate mineralising conditions, SaOS2 cells reproducibly synthesised a bone-like mineralised matrix and temporally expressed the mature osteocyte marker genes SOST, DMP1, PHEX and MEPE and down-regulated expression of RUNX2 and COL1A1. SaOS2 cells cultured in 3D collagen gels acquired a dendritic morphology, characteristic of osteocytes, with multiple interconnecting cell processes. These findings suggest that SaOS2 cells have the capacity to differentiate into mature osteocyte-like cells under mineralising conditions. PTH treatment of SaOS2 cells resulted in strong down-regulation of SOST mRNA expression at all time points tested. Interestingly, PTH treatment resulted in the up-regulation of RANKL mRNA expression only at earlier stages of differentiation. These findings suggest that the response to PTH is dependent on the differentiation stage of the osteoblast/osteocyte. Together, our results demonstrate that SaOS2 cells can be used as a human model to investigate responses to osteotropic stimuli throughout differentiation to a mature osteocyte-like stage.

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.

Cemented liner exchange with bone grafting halts the progression of periacetabular osteolysis.

The aims of this were to examine the effect of acetabular liner exchange and intra-operative bone grafting surgery on peri-prosthetic osteolysis. Seven patients with well-fixed Harris-Galante-1 acetabular components received cemented exchange liners for worn liners associated with pre-operatively CT-quantified osteolysis. During surgery, accessible osteolytic lesions were debrided and bone-grafted. Except for one patient with recurrent dislocation and acetabular component revision, the other patients had CT scans at a median of 4 months and at approximately 4 years after surgery. None of the pre-operative lesions increased in volume during the post-operative reporting period and no new lesions were detected. These results show that cemented liner exchange surgery can halt the progression of osteolysis and that bone grafting has the potential to restore bone.

Critical role of p38 MAPK for regeneration of the sciatic nerve following crush injury in vivo.

BACKGROUND: The physiological function of p38α, which is an isoform of p38 MAPK, has been investigated previously in several studies using pharmacological inhibitors. However, the results regarding whether p38α promotes or inhibits nerve regeneration in vivo have been controversial. METHODS: We generated novel p38α mutant mice (sem mice) with a point mutation in the region encoding the p38α substrate-docking-site, which serves as a limited loss-of-function model of p38α. In the present study, we utilized sem mice and wild-type littermates (wt mice) to investigate the physiological role of p38α in nerve regeneration following crush injuries. RESULTS: At four weeks after crush injury, the average axon diameter and the average axon area in sem mice were significantly smaller than those in wt mice. The average myelin sheath thickness in sem mice was reduced compared to wt mice, but no significant difference was observed in the G-ratio between the two groups. The sciatic functional index value demonstrated that functional nerve recovery in sem mice following crush injury was delayed, which is consistent with the histological findings. To investigate the underlying mechanisms of these findings, we examined inflammatory responses of the sciatic nerve by immunohistochemistry and western blotting. At an early phase following crush injury, sem mice showed remarkably lower expression of inflammatory cytokines, such as TNF-α and IL-1ß, than wt mice. The expression of Caspase-3 and Tenascin-C were also lower in sem mice. Conversely, at a late phase of the response, sem mice showed considerably higher expression of TNF-α and of IL-1ß with lower expression of S-100 than wt mice. CONCLUSIONS: This is the first study of the physiological role of p38 MAPK in nerve regeneration that does not rely on the use of pharmacological inhibitors. Our results indicate that p38α insufficiency may cause an inflammatory disorder, resulting in a delay of histological and functional nerve recovery following crush injury. We conclude that p38 MAPK has an important physiological role in nerve regeneration and may be important for controlling both initiation of inflammation and recovery from nerve injury.

Periprosthetic osteolysis after total hip replacement: molecular pathology and clinical management.

Periprosthetic osteolysis is a serious complication of total hip replacement (THR) in the medium to long term. Although often asymptomatic, osteolysis can lead to prosthesis loosening and periprosthetic fracture. These complications cause significant morbidity and require complex revision surgery. Here, we review advances in our understanding of the cell and tissue response to particles produced by wear of the articular and non-articular surfaces of prostheses. We discuss the molecular and cellular regulators of osteoclast formation and bone resorptive activity, a better understanding of which may lead to pharmacological treatments for periprosthetic osteolysis. We describe the development of imaging techniques for the detection and measurement of osteolysis around THR prostheses, which enable improved clinical management of patients, provide a means of evaluating outcomes of non-surgical treatments for periprosthetic osteolysis, and assist in pre-operative planning for revision surgery. Finally, there have been advances in the materials used for bearing surfaces to minimise wear, and we review the literature regarding the performance of these new materials to date.

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.

A preclinical study of stem subsidence and graft incorporation after femoral impaction grafting using porous hydroxyapatite as a bone graft extender.

This preclinical in vivo screening study compared bone graft incorporation and stem subsidence in cemented hemiarthroplasty after femoral impaction bone grafting with either morselized allograft bone (n = 5, control group) or a 1:1 mix of allograft and porous hydroxyapatite ceramics (HA) granules (n = 5, HA group). At 14 weeks, there was excellent bone graft incorporation by bone, and the stems were well fixed in both groups. The median subsidence at the cement-bone interface, measured using radiostereometric analysis, was 0.14 and 0.93 mm in the control and HA groups, respectively. The comparable histologic results between groups and good stem fixation in this study support the conduct of a larger scale investigation of the use of porous HA in femoral impaction bone grafting at revision hip arthroplasty.

Greater heterogeneity of the bone mineralisation density distribution and low bone matrix mineralisation characterise tibial subchondral bone marrow lesions in knee osteoarthritis patients.

Tibial subchondral bone marrow lesions (BMLs) identified by MRI have been recognised as potential disease predictors in knee osteoarthritis (KOA), and may associate with abnormal bone matrix mineralisation and reduced bone quality. However, these tissue-level changes of BMLs have not been extensively investigated. Thus, the aim of this study was to quantify the degree of subchondral bone matrix mineralisation (both plate and trabeculae) in relation to histomorphometric parameters of bone remodelling and osteocyte lacunae (OL) characteristics in the tibial plateau (TP) of KOA patients with and without BMLs (OA-BML and OA No-BML, respectively) in comparison to nonOA cadaveric controls (CTL). Osteochondral (cartilage-bone) tissue was sampled from the BML signal region within the medial compartment for each OA-BML TP, and from a corresponding medial region for OA No-BML and CTL TPs. The tissue samples were embedded in resin, and sections stained with Von-Kossa Haematoxylin and Eosin (H&E) for quantitation of static indices of bone remodelling. Resin blocks were then further polished, and carbon-coated for quantitative backscattered electron imaging (qBEI) to determine the bone mineralisation density distribution (BMDD), as well as OL characteristics. It was found that OA-BML contained higher osteoid volume per tissue volume (OV/TV; %) and per bone volume (OV/BV; %) in both subchondral plate and trabecular bone compared to OA No-BML and CTL. The BMDD of OA-BML in both subchondral plate and trabecular bone was shifted toward a lower degree of mineralisation. Typically, an increase in both the heterogeneity of mineralisation density (Ca Width; wt%Ca) and the percentage of lower calcium (Ca Low; % B.Ar) in trabecular bone with OA-BML versus CTL was observed. Further, unmineralised OL density (#/mm2) in subchondral plate was distinctly higher in OA-BML samples compared to CTL. The KOA patients with and without BMLs had significantly decreased density of mineralised OL (#/mm2) in trabecular bone compared to CTL. Taken together, these findings indicate that tibial BMLs in advanced KOA patients are characterised by significantly hypo-mineralised subchondral bone compared with CTL. These differences associated with evidence of increased bone remodelling in OA-BML, and may influence the mechanical properties of the subchondral bone, with implications for the overlying cartilage.

Zoledronic acid protects against osteosarcoma-induced bone destruction but lacks efficacy against pulmonary metastases in a syngeneic rat model.

Osteosarcoma (OS) is the most common primary malignant tumor of bone in children and adolescents. In spite of successful control of the primary tumor, death from lung metastasis occurs in more than a third of patients. To investigate the efficacy of zoledronic acid (ZOL) on the development, progression and metastatic spread of OS, we used a rat model of OS, with features of the disease similar to human patients, including spontaneous metastasis to lungs. Rat OS cells were inoculated into the tibial marrow cavity of syngeneic rats. OS development was associated with osteolysis mixed with new bone formation, adjacent to the periosteum and extended into the surrounding soft tissue. Metastatic foci in the lungs formed 3-4 weeks postcancer cell transplantation. Treatment with a clinically relevant dose of ZOL was initiated 1 week after tumors were established and continued once weekly or as a single dose. ZOL preserved the integrity of both trabecular and cortical bone and reduced tumor-induced bone formation. However, the overall tumor burden at the primary site was not reduced because of the persistent growth of cancer cells in the extramedullary space, which was not affected by ZOL treatment. ZOL treatment failed to prevent the metastatic spread of OS to the lungs. These findings suggest that ZOL as a single agent protects against OS-induced bone destruction but lacks efficacy against pulmonary metastases in this rat model. ZOL may have potential value as an adjuvant therapy in patients with established OS.

Zoledronic acid inhibits both the osteolytic and osteoblastic components of osteosarcoma lesions in a mouse model.

PURPOSE: To evaluate the efficacy of zoledronic acid (ZOL) against osteosarcoma (OS) growth, progression, and metastatic spread using an animal model of human OS that closely resembles the human disease. EXPERIMENTAL DESIGN: Human K-HOS or KRIB OS cells, tagged or untagged with a luciferase reporter construct, were transplanted directly into the tibial cavity of nude mice. ZOL was given as weekly, or a single dose of 100 microg/kg body weight, equivalent to the 4 mg i.v. dose used clinically. Tumor growth at the primary site and as pulmonary metastases was monitored by bioluminescence imaging and histology, and OS-induced bone destruction was measured using high-resolution micro-computed tomography. RESULTS: Mice transplanted with OS cells exhibited aberrant bone remodeling in the area of cancer cell transplantation, with areas of osteolysis mixed with extensive new bone formation extending from the cortex. ZOL administration prevented osteolysis and significantly reduced the amount of OS-induced bone formation. However, ZOL had no effect on tumor burden at the primary site. Importantly, ZOL failed to reduce lung metastasis and in some cases was associated with larger and more numerous metastatic lesions. CONCLUSIONS: Our data show that clinically relevant doses of ZOL, while protecting the bone from OS-induced bone destruction, do not inhibit primary tumor growth. Moreover, lung metastases were not reduced and may even have been promoted by this treatment, indicating that caution is required when the clinical application of the bisphosphonate class of antiresorptives is considered in OS.

Apo2L/TRAIL inhibits tumor growth and bone destruction in a murine model of multiple myeloma.

PURPOSE: Multiple myeloma is an incurable disease, for which the development of new therapeutic approaches is required. Here, we report on the efficacy of recombinant soluble Apo2L/tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) to inhibit tumor progression and bone destruction in a xenogeneic model of human multiple myeloma. EXPERIMENTAL DESIGN: We established a mouse model of myeloma, in which Apo2L/TRAIL-sensitive RPMI-8226 or KMS-11 cells, tagged with a triple reporter gene construct (NES-HSV-TK/GFP/Luc), were transplanted directly into the tibial marrow cavity of nude mice. Tumor burden was monitored progressively by bioluminescence imaging and the development of myeloma-induced osteolysis was measured using high resolution in vivo micro-computed tomography. RESULTS: Tumor burden increased progressively in the tibial marrow cavity of mice transplanted with Apo2L/TRAIL-sensitive RPMI-8226 or KMS-11 cells associated with extensive osteolysis directly in the area of cancer cell transplantation. Treatment of mice with recombinant soluble Apo2L/TRAIL reduced myeloma burden in the bone marrow cavity and significantly protected against myeloma-induced osteolysis. The protective effects of Apo2L/TRAIL treatment on bone were mediated by the direct apoptotic actions of Apo2L/TRAIL on myeloma cells within the bone microenvironment. CONCLUSIONS: This is the first in vivo study that investigates the efficacy of recombinant Apo2L/TRAIL on myeloma burden within the bone microenvironment and associated myeloma-induced bone destruction. Our findings that recombinant soluble Apo2L/TRAIL reduces myeloma burden within the bone microenvironment and protects the bone from myeloma-induced bone destruction argue against an inhibitory role of osteoprotegerin in Apo2L/TRAIL-induced apoptosis in vivo and highlight the need to clinically evaluate Apo2L/TRAIL in patients with multiple myeloma.

Distribution of periacetabular osteolytic lesions varies according to component design.

Using computed tomography, the volume, location, and number of osteolytic lesions were determined adjacent to 38 Harris-Galante 1 (HG-1) acetabular components fixed with screws and 19 porous-coated anatomic (PCA) acetabular components press-fitted without screws. The median implantation times were 16 and 15 years, respectively. The mean total lesion volumes were similar: 11.1 cm(3) (range, 0.7-49 cm(3)) and 9.8 cm(3) (range, 0.4-52 cm(3)), respectively, for hips with HG-1 and PCA components (P = .32). There was a significant difference in the proportion of rim-related, screw or screw hole-related, and combined lesions between the 2 component designs (P < .0001). HG-1 components had more screw and screw hole-related lesions, and PCA components had more rim-related lesions. Although there are concerns regarding screw and screw hole-associated osteolysis, these findings suggest that peripheral fixation may be well maintained in the long term with the use of multiple-hole acetabular components with screw fixation.

Raman microspectroscopy demonstrates reduced mineralization of subchondral bone marrow lesions in knee osteoarthritis patients.

INTRODUCTION: Bone marrow lesions (BMLs) are frequently identified by MRI in the subchondral bone in knee osteoarthritis (KOA). BMLs are known to be closely associated with joint pain, loss of the cartilage and structural changes in the subchondral trabecular bone (SCTB). Despite this, understanding of the nature of BMLs at the trabecular tissue level is incomplete. Thus, we used Raman microspectroscopy to examine the biochemical properties of SCTB from KOA patients with presence or absence of BMLs (OA-BML, OA No-BML; respectively), in comparison with age-matched cadaveric non-symptomatic controls (Non-OA CTL). METHODS: Tibial plateau (TP) specimens were collected from 19 KOA arthroplasty patients (6-Male, 13-Female; aged 56-74 years). BMLs were identified ex-vivo by MRI, using PDFS- and T1-weighted sequences. The KOA specimens were then categorized into an OA-BML group (n = 12; containing a BML within the medial condyle only) and an OA No-BML group (n = 7; with no BMLs identified in the TP). The control (CTL) group consisted of Non-OA cadaveric TP samples with no BMLs and no macroscopic or microscopic evidence of OA-related changes (n = 8; 5-Male, 3-Female; aged 44-80 years). Confocal Raman microspectroscopy, with high spatial resolution, was used to quantify the biochemical properties of SCTB tissue of both the medial and the lateral condyle in each group. RESULTS: The ratios of peak intensity and integrated area of bone matrix mineral (Phosphate (v1), Phosphate (v2) and Phosphate (v4)), to surrogates of the organic phase of bone matrix (Amide I, Proline and Amide III), were calculated. Within the medial compartment, the mineral:organic matrix ratios were significantly lower for OA-BML, compared to Non-OA CTL. These ratios were also significantly lower for the OA-BML medial compartment, compared to the OA-BML lateral compartment. There were no group or compartmental differences for Carbonate:Phosphate (v1, v2 and v4), Amide III (α-helix):Amide III (random-coil), Hydroxyproline:Proline, or Crystallinity. CONCLUSION: As measured by Raman microspectroscopy, SCTB tissue in BML zones in KOA is significantly less mineralized than the corresponding zones in individuals without OA. These data are consistent with those obtained using other methods (e.g. Fourier transform infrared spectroscopy; FTIR) and with the increased rate of bone remodeling observed in BML zones. Reduced mineralization may change the biomechanical properties of the trabecular bone in BMLs and the mechanical interaction between subchondral bone and its overlying cartilage, with potential implications for the development and progression of OA.