Analysis of agalacto-IgG in rheumatoid arthritis using surface plasmon resonance

It is well established that IgG from rheumatoid arthritis (RA) patients are less galactosylated than IgG from normal individuals. Determination of agalacto-IgG may therefore aid in diagnosis and treatment of RA. The decrease in galactosylation of IgG leads to an increase in terminal N-acetylglucosamine residues, which can be detected using a specific lectin from Psathyrella velutina. In the present study IgG from RA and control serum was purified using affinity chromatography. The samples were then, after reduction, analyzed on a BIOCORE® 2000 system with immobilized Psathyrella velutina lectin. Using this technique it was possible to discriminate between IgG from RA patients and IgG from control individuals with respect to its content of IgG with terminal N-acetylglucosamine. The affinity biosensor technique makes it possible to detect binding without labeling or using secondary antibodies.     

Effect of sclerostin-neutralising antibody on periarticular and systemic bone in a murine model of rheumatoid arthritis: a microCT study

Introduction

Patients with chronic inflammatory diseases have increased bone loss and bone fragility and are at increased risk of fracture. Although anti-resorptive drugs are effective in blocking inflammation-induced bone loss, they are less effective at rebuilding bone. We have previously shown that treatment with sclerostin antibody (Scl-AbI) builds bone and can prevent or restore bone loss in a murine model of inflammatory bowel disease. In this study, we tested the effect of Scl-AbI in a murine model of rheumatoid arthritis (the collagen-induced arthritis model, CIA). We hypothesised that sclerostin blockade can protect and restore bone both locally and systemically without affecting progression of inflammation.

Methods

CIA was induced in male DBA/1 mice, which were treated with either PBS or Scl-AbI (10 mg/kg, weekly) prophylactically for 55 days or therapeutically for 21 days (starting 14 days post onset of arthritis). Systemic inflammation was assessed by measuring the serum concentration of anti-CII IgG1, IgG2a and IgG2b by ELISA. Changes in bone mass and structure, either at sites remote from the joints or at periarticular sites, were measured using DEXA and microCT. Bone focal erosion was assessed in microCT scans of ankle and knee joints.

Results

Circulating anti-CII immunoglobulins were significantly elevated in mice with CIA and there were no significant differences in the levels of anti-CII immunoglobulins in mice treated with PBS or Scl-ABI. Prophylactic Scl-AbI treatment prevented the decrease in whole body bone mineral density (BMD) and in the bone volume fraction at axial (vertebral body) and appendicular (tibial proximal metaphysis trabecular and mid-diaphysis cortical bone) sites seen in PBS-treated CIA mice, but did not prevent the formation of focal bone erosions on the periarticular bone in the knee and ankle joints. In the therapeutic study, Scl-AbI restored BMD and bone volume fraction at all assessed sites but was unable to repair focal erosions.

Conclusions

Sclerostin blockade prevented or reversed the decrease in axial and appendicular bone mass in the murine model of rheumatoid arthritis, but did not affect systemic inflammation and was unable to prevent or repair local focal erosion.     

Diagnosis of rheumatoid arthritis using light: correction of motion artefacts and color visualization of multispectral images

State‐of‐the‐art image‐processing methods offer new possibilities for diagnosing diseases using scattered light. The optical diagnosis of rheumatism is taken as an example to show that the diagnostic sensitivity can be improved using overlapped pseudocolored images of different wavelengths, provided that multispectral images are recorded to compensate for any motion‐related artefacts that occur during examination. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

TWEAK and Fn14 expression in the pathogenesis of joint inflammation and bone erosion in rheumatoid arthritis

Introduction

TNF-like weak inducer of apoptosis (TWEAK) has been proposed as a mediator of inflammation and bone erosion in rheumatoid arthritis (RA). This study aimed to investigate TWEAK and TWEAK receptor (Fn14) expression in synovial tissue from patients with active and inactive rheumatoid arthritis (RA), osteoarthritis (OA) and normal controls and assess soluble (s)TWEAK levels in the synovial fluids from patients with active RA and OA. Effects of sTWEAK on osteoclasts and osteoblasts were investigated in vitro.

Methods

TWEAK and Fn14 expression were detected in synovial tissues by immunohistochemistry (IHC). Selected tissues were dual labelled with antibodies specific for TWEAK and lineage-selective cell surface markers CD68, Tryptase G, CD22 and CD38. TWEAK mRNA expression was examined in human peripheral blood mononuclear cells (PBMC) sorted on the basis of their expression of CD22. sTWEAK was detected in synovial fluid from OA and RA patients by ELISA. The effect of sTWEAK on PBMC and RAW 264.7 osteoclastogenesis was examined. The effect of sTWEAK on cell surface receptor activator of NF Kappa B Ligand (RANKL) expression by human osteoblasts was determined by flow cytometry.

Results

TWEAK and Fn14 expression were significantly higher in synovial tissue from all patient groups compared to the synovial tissue from control subjects (P < 0.05). TWEAK was significantly higher in active compared with inactive RA tissues (P < 0.05). TWEAK expression co-localised with a subset of CD38⁺ plasma cells and with CD22⁺ B-lymphocytes in RA tissues. Abundant TWEAK mRNA expression was detected in normal human CD22⁺ B cells. Higher levels of sTWEAK were observed in synovial fluids isolated from active RA compared with OA patients. sTWEAK did not stimulate osteoclast formation directly from PBMC, however, sTWEAK induced the surface expression of RANKL by human immature, STRO-1⁺ osteoblasts.

Conclusions

The expression of TWEAK by CD22⁺ B cells and CD38⁺ plasma cells in RA synovium represents a novel potential pathogenic pathway. High levels of sTWEAK in active RA synovial fluid and of TWEAK and Fn14 in active RA tissue, together with the effect of TWEAK to induce osteoblastic RANKL expression, is consistent with TWEAK/Fn14 signalling being important in the pathogenesis of inflammation and bone erosion in RA.     

Design and validation of a testing system to assess torsional cancellous bone failure in conjunction with time-lapsed micro-computed tomographic imaging

When compressed axially, cancellous bone often fails at an oblique angle along well-defined bands, highlighting the importance of cancellous bone shear properties. Torsion testing to determine shear properties of cancellous bone has often been conducted under conditions appropriate only for axis-symmetric specimens comprised of homogeneous and isotropic materials. However, most cancellous bone specimens do not meet these stringent test conditions. Therefore, the aim of this study was to design and validate a uniaxial, incremental torsional testing system for non-homogeneous orthotropic or non-axis-symmetric specimens.Precision and accuracy of the newly designed torsion system was validated by using Plexiglas rods and beams, where obtained material properties were compared to those supplied by the manufacturer. Additionally, the incremental step-wise application of angular displacement and simultaneous time-lapsed μCT imaging capability of the system was validated using whale cancellous bone specimens, with step-wise application of angular displacement yielding similar torsional mechanical properties to continuous application of angular displacement in a conventional torsion study.In conclusion, a novel torsion testing system for non-homogeneous, orthotropic materials using the incremental step-wise application of torsion and simultaneous time-lapsed μCT imaging was designed and validated.     

Mechanical analysis of a rodent segmental bone defect model: The effects of internal fixation and implant stiffness on load transfer

Segmental bone defect animal models are often used for evaluating the bone regeneration performance of bone substituting biomaterials. Since bone regeneration is dependent on mechanical loading, it is important to determine mechanical load transfer after stabilization of the defect and to study the effects of biomaterial stiffness on the transmitted load. In this study, we assess the mechanical load transmitted over a 6 mm femur defect that is stabilized with an internal PEEK fixation plate. Subsequently, three types of selective laser melted porous titanium implants with different stiffness values were used to graft the defect (five specimens per group). In one additional group, the defect was left empty. Micro strain gauges were used to measure strain values at four different locations of the fixation plate during external loading on the femoral head. The load sharing between the fixation plate and titanium implant was highly variable with standard deviations of measured strain values between 31 and 93% of the mean values. As a consequence, no significant differences were measured between the forces transmitted through the titanium implants with different elastic moduli. Only some non-significant trends were observed in the mean strain values that, consistent with the results of a previous finite element study, implied the force transmitted through the implant increases with the implant stiffness. The applied internal fixation method does not standardize mechanical loading over the defect to enable detecting small differences in bone regeneration performances of bone substituting biomaterials. In conclusion, the fixation method requires further optimization to reduce the effects of the operative procedure and make the mechanical loading more consistent and improve the overall sensitivity of this rat femur defect model.     

Inflammatory lesions in the bone marrow of rheumatoid arthritis patients: a morphological perspective

The synovial tissue stands at the epicenter of joint pathology in rheumatoid arthritis (RA). As a primary target of the disease, studies on the synovium have provided invaluable insights into the mechanisms involved in disease pathogenesis. Recent work has, however, revealed the importance of a previously unseen anatomic compartment in direct contact with the joint space, namely the subchondral bone marrow. Bone marrow edema (BME) visible on magnetic resonance imaging (MRI) is clinically meaningful in both early and late RA as it associates with future development of bone erosions and poor functional outcomes. Although the histopathologic correlates of MRI-based BME in early RA remain obscure, studies in advanced disease are consistent in describing lymphocytic inflammatory infiltrates within the subchondral marrow cavity of affected joints. In this review, we discuss the nature of bone marrow lesions in patients with RA, analyze their relationship with synovitis, and explore their potential contribution to the pathological processes of the disease.Rheumatoid arthritis (RA) is traditionally regarded as an archetypal disease of the synovial tissue. The synovial membrane indeed undergoes early inflammatory changes, which include increased vascularity as well as intimal lining layer hyperplasia and accumulation of macrophages, plasma cells, T cells, B cells, dendritic cells, natural killer cells and mast cells in the sublining, among other changes [1]. Collectively, localization of inflammation to the synovium is primarily responsible for the dysregulated cellular and molecular mechanisms that ultimately lead to the typical signs and symptoms of RA, including joint pain, stiffness, swelling and structural changes. Although the pathogenic and clinical importance of synovitis is beyond question, it is becoming increasingly apparent that a ''synovio-centric'' model of RA could be limiting. Indeed, other anatomic compartments appear to be involved at all stages of the disease. The most important example comes from the recognition that clinical arthritis and subclinical synovitis are anticipated by a pre-articular immunologic phase possibly developing in lymphoid tissues as well as in the lungs [2,3]. Full-blown joint disease itself spreads well beyond synovial tissue inflammation. Established arthritis can be characterized by the involvement of at least two other compartments that are in direct contact with the joint space. These include the draining lymph nodes (LNs) [4,5] and, of special relevance, the subchondral bone marrow (BM) [6].As dysregulated B cell responses are central pathogenic events in RA and B-cell autoreactivity originates, at least in part, from defective checkpoints within the BM (a primary lymphoid organ) [7], the role of this compartment in the immunopathogenesis of RA has attracted great attention over the years. Data supporting the existence of BM abnormalities were mainly derived from studies on marrow aspirates/biopsies from the sternum and the iliac crest, which are primary hematopoietic and immunologic sites in adult life. The role that the ''red marrow'' might play in the immunologic disturbances of RA thus appears interesting but not completely unexpected. Less predictably, evidence has accumulated supporting the additional involvement of the BM adjacent to inflamed joints at peripheral sites. This is normally a fat-rich tissue (''yellow marrow'') where hematopoiesis is not prominent. In RA, the fat can be replaced by a vascularized, cell-rich inflammatory tissue. Combined with imaging data coming from magnetic resonance imaging (MRI) studies, histopathologic changes described within the subchondral BM have been postulated to be intimately involved in the pathological processes producing local inflammation and tissue remodeling in RA joints [6,8-10]. Here we will discuss the most relevant findings related to BM alterations in RA, focusing on their morphological characteristics and pathologic significance. In view of the clinical relevance of MRI findings, special emphasis is given to the subchondral BM.     

Diagnosis of rheumatoid arthritis: multivariate analysis of biomarkers

Objective. To test if a combination of biomarkers can increase the classification power of autoantibodies to cyclic citrullinated peptides (anti-CCP) in the diagnosis of rheumatoid arthritis (RA) depending on the diagnostic situation. Methods. Biomarkers were subject to three inclusion/exclusion criteria (discrimination between RA patients and healthy blood donors, ability to identify anti-CCP-negative RA patients, specificity in a panel with major non-rheumatological diseases) before univariate ranking and multivariate analysis was carried out using a modelling panel (n=906). To enable the evaluation of the classification power in different diagnostic settings the disease controls (n=542) were weighted according to the admission rates in rheumatology clinics modelling a clinic panel or according to the relative prevalences of musculoskeletal disorders in the general population seen by general practitioners modelling a GP panel. Results. Out of 131 biomarkers considered originally, we evaluated 32 biomarkers in this study, of which only seven passed the three inclusion/exclusion criteria and were combined by multivariate analysis using four different mathematical models. In the modelled clinic panel, anti-CCP was the lead marker with a sensitivity of 75.8% and a specificity of 94.0%. Due to the lack in specificity of the markers other than anti-CCP in this diagnostic setting, any gain in sensitivity by any marker combination is off-set by a corresponding loss in specificity. In the modelled GP panel, the best marker combination of anti-CCP and interleukin (IL)-6 resulted in a sensitivity gain of 7.6% (85.9% vs. 78.3%) at a minor loss in specificity of 1.6% (90.3% vs. 91.9%) compared with anti-CCP as the best single marker. Conclusions. Depending on the composition of the sample panel, anti-CCP alone or anti-CCP in combination with IL-6 has the highest classification power for the diagnosis of established RA.     

Circulating mediators of bone remodeling in psoriatic arthritis: implications for disordered osteoclastogenesis and bone erosion

Introduction  

Diverse bone pathologies are observed in patients with psoriatic arthritis (PsA). Uncoupling of bone remodeling with disordered osteoclastogenesis has been implicated in the pathogenesis of PsA. The aim of this study was to examine the role of soluble mediators of bone remodeling within the circulation of patients with PsA.     

Circulating mediators of bone remodeling in psoriatic arthritis: implications for disordered osteoclastogenesis and bone erosion

Introduction

Rheumatoid arthritis (RA) is a systemic disease manifested by chronic inflammation in multiple articular joints, including the knees and small joints of the hands and feet. We have developed a unique modification to a clinically accepted method for delivering therapies directly to the synovium. Our therapy is based on our previous discovery of an analog peptide (A9) with amino acid substitutions made at positions 260 (I to A), 261 (A to B), and 263 (F to N) that could profoundly suppress immunity to type II collagen (CII) and arthritis in the collagen-induced arthritis model (CIA).

Methods

We engineered an adenoviral vector to contain the CB11 portion of recombinant type II collagen and used PCR to introduce point mutations at three sites within (CII_{124-402, 260A, 261B, 263D}), (rCB11-A9) so that the resulting molecule contained the A9 sequence at the exact site of the wild-type sequence.

Results

We used this construct to target intra-articular tissues of mice and utilized the collagen-induced arthritis model to show that this treatment strategy provided a sustained, local therapy for individual arthritic joints, effective whether given to prevent arthritis or as a treatment. We also developed a novel system for in vivo bioimaging, using the firefly luciferase reporter gene to allow serial bioluminescence imaging to show that luciferase can be detected as late as 18 days post injection into the joint.

Conclusions

Our therapy is unique in that we target synovial cells to ultimately shut down T cell-mediated inflammation. Its effectiveness is based on its ability to transform potential inflammatory T cells and/or bystander T cells into therapeutic (regulatory-like) T cells which secrete interleukin (IL)-4. We believe this approach has potential to effectively suppress RA with minimal side effects.     

Age-related changes in arthritis susceptibility and severity in a murine model of rheumatoid arthritis

Background

Rheumatoid arthritis (RA) most often begins in females in the fourth-fifth decade of their life, suggesting that the aging of the immune system (immunosenescence) has a major role in this disease. Therefore, in the present study, we sought to investigate the effect of age on arthritis susceptibility in BALB/c mice using the proteoglycan (PG)-induced arthritis (PGIA) model of RA.

Results

We have found that young, 1-month-old female BALB/c mice are resistant to the induction of PGIA, but with aging they become susceptible. PG-induced T cell responses decline with age, whereas there is a shift toward Th1 cytokines. An age-dependent decrease in T cell number is associated with an increased ratio of the memory phenotype, and lower CD28 expression. Antigen-presenting cells shifted from macrophages and myeloid dendritic cells in young mice toward B cells in older mice. The regulatory/activated T cell ratio decreases in older mice after PG injections indicating impaired regulation of the immune response.

Conclusion

We conclude that immunosenescence could alter arthritis susceptibility in a very complex manner including both adaptive and innate immunities, and it cannot be determined by a single trait. Cumulative alterations in immunoregulatory functions closely resemble human disease, which makes this systemic autoimmune arthritis model of RA even more valuable.     

Surface roughness parameters as predictors of anchorage strength in bone: a critical analysis

The surface roughness of a bone implant was defined parametrically. The values of the parameters defining the surface were varied. Some traditionally used surface roughness parameters were calculated. By means of a theoretical model the bone-implant interfacial shear strength was estimated. No simple correlation between the values of the surface roughness parameters and the estimated interfacial shear strength was found. It was concluded that the value of the traditional surface roughness parameters as predictors of interfacial shear strength is limited. If however a change of the surface topography of an implant is restricted to scale a positive correlation was found between the theoretical interfacial shear strength and some surface roughness parameters. It is suggested that the bone-implant interfacial shear strength in the general case be estimated by means of strength analyses based upon a study of the size, shape and density of the individual elements constituting the rough surface.     

Chicken model of steroid-induced bone marrow adipogenesis using proteome analysis: a preliminary study

Background  

Steroid-induced adipogenesis increases fat-cell volume and pressure in bone marrow. This may be a contributing factor in some forms of osteonecrosis. In this observational study, we aimed to determine the protein expression relating to steroid-induced adipogenesis of femoral bone marrow with use of a chicken model. We compared the histologic features of the femoral marrow of eight methylprednisolone (MP)-treated chickens with those of three control chickens and assessed differential proteins with 2-dimensional gel electrophoresis and differential proteins were identified by MALDI-TOF MS.     

Impact of Schistosoma japonicum infection on collagen-induced arthritis in DBA/1 mice: a murine model of human rheumatoid arthritis

Background

The hygiene hypothesis suggests that helminth infections prevent a range of autoimmune diseases.

Methodology/Principal Findings

To investigate the effects of S. japonicum infection on collagen-induced arthritis (CIA), male DBA/1 mice were challenged with unisexual or bisexual S. japonicum cercariae two weeks prior to bovine type II collagen (CII) immunization or at the onset of CIA. S. japonicum infection prior to CII immunization significantly reduced the severity of CIA. ELISA (enzyme linked immunosorbent assay) showed that the levels of anti-CII IgG and IgG2a were reduced in prior schistosome-infected mice, while anti-CII IgG1 was elevated. Splenocyte proliferation against both polyclonal and antigen-specific stimuli was reduced by prior schistosome infection as measured by tritiated thymidine incorporation (³H-TdR). Cytokine profiles and CD4⁺ T cells subpopulation analysis by ELISA and flow cytometry (FCM) demonstrated that prior schistosome infection resulted in a significant down-regulation of pro-inflammatory cytokines (IFN-γ, TNF-α, IL-1β and IL-6) and Th1 cells, together with up-regulation of the anti-inflammatory cytokine IL-10 and Th2 cells. Interestingly, the expansion of Treg cells and the reduction of Th17 cells were only observed in bisexually infected mice. In addition, prior schistosome infection notably reduced the expression of pro-inflammatory cytokines and receptor activator of NF-κB ligand (RANKL) in the inflamed joint. However, the disease was exacerbated at one week after infection when established CIA mice were challenged with bisexual cercariae.

Conclusion/Significance

Our data provide direct evidence that the Th2 response evoked by prior S. japonicum infection can suppress the Th1 response and pro-inflammatory mediator and that bisexual infection with egg-laying up-regulates the Treg response and down-regulates the Th17 response, resulting in an amelioration of autoimmune arthritis. The beneficial effects might depend on the establishment of a Th2-dominant response rather than the presence of the eggs. Our results suggest that anti-inflammatory molecules from the parasite could treat autoimmune diseases.     

Diagnosis of rheumatoid arthritis: multivariate analysis of biomarkers.

OBJECTIVE: To test if a combination of biomarkers can increase the classification power of autoantibodies to cyclic citrullinated peptides (anti-CCP) in the diagnosis of rheumatoid arthritis (RA) depending on the diagnostic situation. METHODS: Biomarkers were subject to three inclusion/exclusion criteria (discrimination between RA patients and healthy blood donors, ability to identify anti-CCP-negative RA patients, specificity in a panel with major non-rheumatological diseases) before univariate ranking and multivariate analysis was carried out using a modelling panel (n = 906). To enable the evaluation of the classification power in different diagnostic settings the disease controls (n = 542) were weighted according to the admission rates in rheumatology clinics modelling a clinic panel or according to the relative prevalences of musculoskeletal disorders in the general population seen by general practitioners modelling a GP panel. RESULT: Out of 131 biomarkers considered originally, we evaluated 32 biomarkers in this study, of which only seven passed the three inclusion/exclusion criteria and were combined by multivariate analysis using four different mathematical models. In the modelled clinic panel, anti-CCP was the lead marker with a sensitivity of 75.8% and a specificity of 94.0%. Due to the lack in specificity of the markers other than anti-CCP in this diagnostic setting, any gain in sensitivity by any marker combination is off-set by a corresponding loss in specificity. In the modelled GP panel, the best marker combination of anti-CCP and interleukin (IL)-6 resulted in a sensitivity gain of 7.6% (85.9% vs. 78.3%) at a minor loss in specificity of 1.6% (90.3% vs. 91.9%) compared with anti-CCP as the best single marker. CONCLUSION: Depending on the composition of the sample panel, anti-CCP alone or anti-CCP in combination with IL-6 has the highest classification power for the diagnosis of established RA.     

Breakdown of cartilage proteoglycan in a tissue culture model of rheumatoid arthritis

Proteoglycan breakdown was studied in a coculture model which mimics the confrontation between synovium and cartilage that occurs in rheumatoid arthritis. Bovine nasal-septum cartilage discs radioactively labeled (³⁵SO₄^2? with or without [³H]glucosamine) and ‘chased’ in non-radioactive medium were cultured in contact with minced rheumatoid synovial membranes for intervals up to 8 days. Synovium-stimulated (2–3 fold) cartilage breakdown was unaffected by ascorbate supplementation. Labeled products (small molecules plus proteoglycan complexes) in culture media were characterized by chromatographic, sedimentation and enzymic digestion methods. Breakdown was dominated by the release of a range of proteoglycan products, fully disaggregated and incapable of reaggregation with added hyaluronate. Because constituent glycosaminoglycans were of uniform size, proteoglycan polydispersity was attributed to differences in core protein length. Hydrocortisone inhibited degradation and partially prevented the shift of proteoglycans to lower average molecular weight. An additional breakdown pattern occasionally noted during the initial 48 h of coculture was characterized by release of a subpopulation of low charge-density proteoglycan bearing shortened glycosaminoglycan chains, consistent with glycosidase action. We conclude that rheumatoid synovia exhibit two distinct cartilage degradative potencies in vitro that may be important in vivo: (a) A variable hyaluronidase-like activity at early culture times, and (b) a dominant proteolytic activity generating an array of disaggregated proteoglycann products that differ largely on the basis of their core lengths. The response to hydrocortisone is consistent with inhibition of proteolysis through the stabilization of cellular membranes.     

Alterations in the self-renewal and differentiation ability of bone marrow mesenchymal stem cells in a mouse model of rheumatoid arthritis

Introduction

Rheumatoid arthritis (RA) is a chronic systemic autoimmune disease primarily involving the synovium. Evidence in recent years has suggested that the bone marrow (BM) may be involved, and may even be the initiating site of the disease. Abnormalities in haemopoietic stem cells'' (HSC) survival, proliferation and aging have been described in patients affected by RA and ascribed to abnormal support by the BM microenvironment. Mesenchymal stem cells (MSC) and their progeny constitute important components of the BM niche. In this study we test the hypothesis that the onset of inflammatory arthritis is associated with altered self-renewal and differentiation of bone marrow MSC, which alters the composition of the BM microenvironment.

Methods

We have used Balb/C Interleukin-1 receptor antagonist knock-out mice, which spontaneously develop RA-like disease in 100% of mice by 20 weeks of age to determine the number of mesenchymal progenitors and their differentiated progeny before, at the start and with progression of the disease.

Results

We showed a decrease in the number of mesenchymal progenitors with adipogenic potential and decreased bone marrow adipogenesis before disease onset. This is associated with a decrease in osteoclastogenesis. Moreover, at the onset of disease a significant increase in all mesenchymal progenitors is observed together with a block in their differentiation to osteoblasts. This is associated with accelerated bone loss.

Conclusions

Significant changes occur in the BM niche with the establishment and progression of RA-like disease. Those changes may be responsible for aspects of the disease, including the advance of osteoporosis. An understanding of the molecular mechanisms leading to those changes may lead to new strategies for therapeutic intervention.