Osteoprotegerin reduces the loss of periarticular bone mass in primary and secondary spongiosa but does not influence inflammation in rat antigen-induced arthritis

Osteoprotegerin Prevents Intracranial Aneurysm Progression by Promoting Collagen Biosynthesis and Vascular Smooth Muscle Cell Proliferation

Background Decreased extracellular matrix formation and few vascular smooth muscle cells (VSMCs) in cerebral vascular walls are the main characteristics of intracranial aneurysm (IA) pathogenesis. Recently, osteoprotegerin was reported to activate collagen biosynthesis and VSMC proliferation via the TGF-β1 (transforming growth factor-β1) signaling. This study aimed to investigate whether osteoprotegerin can prevent IA progression in rats through enhanced collagen expression and VSMC proliferation. Methods and Results IAs were surgically induced in 7-week-old male Sprague-Dawley rats; at 1-week post-operation, recombinant mouse osteoprotegerin or vehicle control was continuously infused for 4 weeks into the lateral ventricle using an osmotic pump. In the osteoprotegerin-treatment group, the aneurysmal size was significantly smaller (37.5 μm versus 60.0 μm; P<0.01) and the media of IA walls was thicker (57.1% versus 36.0%; P<0.01) than in the vehicle-control group. Type-I and type-III collagen, TGF-β1, phosphorylated Smad2/3, and proliferating cell nuclear antigen were significantly upregulated in the IA walls of the osteoprotegerin group than that in the control group. No significant difference was found in the expression of proinflammatory genes between the groups. In mouse VSMC cultures, osteoprotegerin treatment upregulated the expression of collagen and TGF-β1 genes, and activated VSMC proliferation; the inhibition of TGF-β1 signaling nullified this effect. Conclusions Osteoprotegerin suppressed the IA progression by a unique mechanism whereby collagen biosynthesis and VSMC proliferation were activated via TGF-β1 without altering proinflammatory gene expression. Osteoprotegerin may represent a novel therapeutic target for IAs.

Zoledronic acid ameliorates the effects of secondary osteoporosis in rheumatoid arthritis patients

Background

Secondary osteoporosis may occur in patients with rheumatoid arthritis (RA), causing irreversible joint damage and disability. Bisphosphonates, the recently developed bone resorption inhibitors, have demonstrated significant therapeutic effects on senile and postmenopausal osteoporosis. This study evaluated the efficacy and safety of zoledronic acid (ZOL), with or without methotrexate (MTX), for the prevention and treatment of bone destruction in RA patients.

Methods

We recruited 66 RA patients with symptoms of secondary osteoporosis. They were randomized into three treatment groups—combined treatment with MTX and ZOL, ZOL monotherapy, or MTX monotherapy—in two consecutive 6-month periods. The participants were followed for 12 months. At the end of each treatment period, improvement in disease activity, bone destruction, and fracture risk were evaluated.

Results

Combined treatment with ZOL and MTX had significantly better clinical efficacy compared with either ZOL or MTX monotherapy (P < 0.05). The combination significantly improved the lumbar spine and hip BMD and reduced FRAX scores, suggesting that ZOL combined with MTX reduces bone loss and risk of hip fracture in RA patients with secondary osteoporosis.

Conclusion

ZOL has a synergistic effect when combined with MTX, inhibiting RA disease activity, reducing fracture risk, and improving quality of life in RA patients with secondary osteoporosis.

Trial registration

Chinese Clinical Trial Registry, ChiCTR1800019290. Registered 3 November 2018–Retrospective registered, http://www.chictr.org.cn/showproj.aspx?proj = 31758

A Clinical Study Evaluating the Effects of Fluvastatin on Serum Osteoprotegerin Levels in Rheumatoid Arthritis Patients

Osteoprotegerin (OPG), a member of the tumor necrosis factor receptor family, has been identified as a critical regulator of bone resorption. Considering the possible role of OPG in rheumatoid arthritis (RA) and in the osteoclastogenesis suppression effects of statins, the present study aims to investigate the effects of fluvastatin on serum levels OPG and disease activity score (DAS) in patients with RA. Forty patients with RA were randomized in a placebo-controlled trial to receive 40 mg fluvastatin or placebo as an adjunct to existing disease-modifying antirheumatic drug (DMARD) therapy (methotrexate, leflunomide, hydroxychloroquine). Patients were followed up over 12 weeks. OPG and disease activity variables were measured at baseline and after 12 weeks of treatment. After 12 weeks, the OPG level was significantly increased in the fluvastatin group compared to the placebo group. DAS-28 was significantly decreased in the fluvastatin group compared to the placebo group. C-reactive protein (CRP), morning stiffness, swollen joint count (SJC), and tender joint count (TJC) were significantly decreased in the fluvastatin group compared to the placebo group; however, erythrocyte sedimentation rate (ESR), modified health assessment questionnaire (MHAQ), and visual analogue screen (VAS) were not changed significantly. In conclusion, fluvastatin administration could increase the OPG levels and improve disease activity variables in patients with RA. Therefore, fluvastatin may serve a potential benefit in the treatment of RA patients.

1,25-Dihydroxyvitamin D3 prevents bone loss of the secondary spongiosa in arthritic rats by an increase of bone formation and mineralization and inhibition of bone resorption

Background

Active vitamin D metabolites have been shown to have protective effects in experimental arthritis especially when used as preventive treatment. However, because the direct effects of 1,25-dihydroxyvitamin D3 (1,25(OH) ₂D₃) on bone formation and resorption are very complex, the net effect of 1,25(OH)₂D₃ on histomorphometric parameters of bone turnover and mineralisation should be investigated. Therefore, we examined the influence of 1,25(OH)₂D₃ therapy on arthritis-induced alterations of periarticular and axial bone as well as disease activity, inflammation and joint destruction in antigen-induced arthritis (AIA) of the rat.

Methods

AIA was induced in 20 eight-week-old female Wistar rats. 10 rats without arthritis were used as healthy controls. AIA rats received 1,25(OH)₂D₃ (0.2 μg/kg/day, i.p., n = 10) or vehicle (n = 10) at regular intervals for 28 consecutive days beginning 3 days before arthritis induction. Bone structure of the secondary spongiosa of the periarticular and axial bone was analyzed using histomorphometry. Parameters of mineralization were investigated using tetracycline labelling. Clinical disease activity, inflammation and joint destruction were measured by joint swelling and histological investigation, respectively.

Results

AIA led to significant periarticular bone loss. 1,25(OH)₂D₃ treatment resulted in a highly significant increase in trabecular bone volume and bone formation rate in comparison to both vehicle-treated AIA and healthy controls at periarticular (p < 0.01 and p < 0.001, respectively) and axial bone (p < 0.001 and p < 0.001, respectively). In addition, bone resorption was reduced by 1,25(OH)₂D₃ at the axial bone (p < 0.05 vs. vehicle-treated AIA). Joint swelling as well as histological signs of inflammation and joint destruction were not influenced by 1,25(OH)₂D₃.

Conclusions

The results of the study indicate a marked osteoanabolic effect of 1,25(OH)₂D₃ presumably due to a substantial increase in mineralization. Thus, 1,25(OH)₂D₃ may be an effective osteoanabolic treatment principle to antagonize the inflammation-associated suppression of bone formation in rheumatoid arthritis.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2474-15-345) contains supplementary material, which is available to authorized users.

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.

RANKL-targeted therapy inhibits bone resorption in experimental Staphylococcus aureus-induced arthritis

INTRODUCTION

Bacterial arthritis causes rapidly progressing joint destruction in humans. We have shown that addition of bisphosphonates or corticosteroids to conventional antimicrobial agents decreases the activity of osteoclasts, thereby reducing bone destruction. Here we assess the effect of RANKL-targeted treatments using soluble receptor decoy and osteprotegerin (OPG) on the course and outcome of staphylococcal arthritis.

METHODS

Treatment was initiated 3 days after Staphylococcus aureus inoculation and included RANK-Fc, OPG-Fc, and OPG-Fc in combination with antibiotics. Control groups were treated with antibiotics, huFc, and PBS. Joints were evaluated for clinical signs of arthritis and histologically for bone and cartilage destruction. Bone mineral density (BMD) was evaluated using a peripheral quantitative computed tomography. Circulating markers of bone metabolism, inflammatory cytokines, and chemokines were analyzed in each group.

RESULTS

Mice treated with RANK-Fc or OPG-Fc in combination with antibiotics preserved total BMD and trabecular bone as compared to huFc or antibiotics. Treatment with RANK-Fc or OPG-Fc diminished the levels of bone resorption markers (osteocalcin, CTX-I, and TRACP5b). Neither RANK-Fc nor OPG-Fc influenced significantly the frequency and severity of arthritis.

CONCLUSIONS

Inhibition of RANKL signalling efficiently prevents bone loss in the mouse model of bacterial arthritis even when started in the overt phase of infection.

RANKL inhibition for the management of patients with benign metabolic bone disorders

The receptor activator of NF-kappaB ligand (RANKL) is a member of the TNF receptor superfamily, essential for osteoclastogenesis. It binds to its receptor activator of NF-kappaB on the surface of osteoclast precursors and enhances their differentiation, survival and fusion, while it activates mature osteoclasts and inhibits their apoptosis. The effects of RANKL are counteracted by osteoprotegerin (OPG), a neutralizing decoy receptor. Derangement of the balance in RANKL/OPG action is implicated in the pathophysiology of metabolic bone diseases, including osteoporosis. Current therapies used to prevent or treat metabolic bone diseases are thought to act, at least in part, through modification of the RANKL/OPG dipole. The idea of using a molecule that could specifically bind and neutralize RANKL to decrease bone resorption and subsequent bone loss is appealing. Recombinant OPG was initially tested. Denosumab, a fully human monoclonal antibody against RANKL, is a promising antiresorptive agent under investigation. It rapidly decreases bone turnover markers resulting in a significant increase in bone mineral density and reduction in fracture risk. However, because receptor activator of NF-kappaB activation by RANKL is also essential for T-cell growth and dendritic-cell function, inhibition of its action could simultaneously affect the immune system, leading to susceptibility in infections or malignancies.

RANKL inhibition by osteoprotegerin prevents bone loss without affecting local or systemic inflammation parameters in two rat arthritis models: comparison with anti-TNFalpha or anti-IL-1 therapies

INTRODUCTION

Rat adjuvant-induced arthritis (AIA) and collagen-induced arthritis (CIA) feature bone loss and systemic increases in TNFalpha, IL-1beta, and receptor activator of NF-kappaB ligand (RANKL). Anti-IL-1 or anti-TNFalpha therapies consistently reduce inflammation in these models, but systemic bone loss often persists. RANKL inhibition consistently prevents bone loss in both models without reducing joint inflammation. Effects of these therapies on systemic markers of bone turnover and inflammation have not been directly compared.

METHODS

Lewis rats with established AIA or CIA were treated for 10 days (from day 4 post onset) with either PBS (Veh), TNFalpha inhibitor (pegsunercept), IL-1 inhibitor (anakinra), or RANKL inhibitor (osteoprotegerin (OPG)-Fc). Local inflammation was evaluated by monitoring hind paw swelling. Bone mineral density (BMD) of paws and lumbar vertebrae was assessed by dual X-ray absorptiometry. Markers and mediators of bone resorption (RANKL, tartrate-resistant acid phosphatase 5b (TRACP 5B)) and inflammation (prostaglandin E2 (PGE2), acute-phase protein alpha-1-acid glycoprotein (alpha1AGP), multiple cytokines) were measured in serum (day 14 post onset).

RESULTS

Arthritis progression significantly increased paw swelling and ankle and vertebral BMD loss. Anti-TNFalpha reduced paw swelling in both models, and reduced ankle BMD loss in AIA rats. Anti-IL-1 decreased paw swelling in CIA rats, and reduced ankle BMD loss in both models. Anti-TNFalpha and anti-IL-1 failed to prevent vertebral BMD loss in either model. OPG-Fc reduced BMD loss in ankles and vertebrae in both models, but had no effect on paw swelling. Serum RANKL was elevated in AIA-Veh and CIA-Veh rats. While antiTNFalpha and anti-IL-1 partially normalized serum RANKL without any changes in serum TRACP 5B, OPG-Fc treatment reduced serum TRACP 5B by over 90% in both CIA and AIA rats. CIA-Veh and AIA-Veh rats had increased serum alpha1AGP, IL-1beta, IL-8 and chemokine (C-C motif) ligand 2 (CCL2), and AIA-Veh rats also had significantly greater serum PGE2, TNFalpha and IL-17. Anti-TNFalpha reduced systemic alpha1AGP, CCL2 and PGE2 in AIA rats, while anti-IL-1 decreased systemic alpha1AGP, IL-8 and PGE2. In contrast, RANKL inhibition by OPG-Fc did not lessen systemic cytokine levels in either model.

CONCLUSIONS

Anti-TNFalpha or anti-IL-1 therapy inhibited parameters of local and systemic inflammation, and partially reduced local but not systemic bone loss in AIA and CIA rats. RANKL inhibition prevented local and systemic bone loss without significantly inhibiting local or systemic inflammatory parameters.

Receptor activator of nuclear factor kappaB ligand and osteoprotegerin regulation of bone remodeling in health and disease

Osteoclasts and osteoblasts dictate skeletal mass, structure, and strength via their respective roles in resorbing and forming bone. Bone remodeling is a spatially coordinated lifelong process whereby old bone is removed by osteoclasts and replaced by bone-forming osteoblasts. The refilling of resorption cavities is incomplete in many pathological states, which leads to a net loss of bone mass with each remodeling cycle. Postmenopausal osteoporosis and other conditions are associated with an increased rate of bone remodeling, which leads to accelerated bone loss and increased risk of fracture. Bone resorption is dependent on a cytokine known as RANKL (receptor activator of nuclear factor kappaB ligand), a TNF family member that is essential for osteoclast formation, activity, and survival in normal and pathological states of bone remodeling. The catabolic effects of RANKL are prevented by osteoprotegerin (OPG), a TNF receptor family member that binds RANKL and thereby prevents activation of its single cognate receptor called RANK. Osteoclast activity is likely to depend, at least in part, on the relative balance of RANKL and OPG. Studies in numerous animal models of bone disease show that RANKL inhibition leads to marked suppression of bone resorption and increases in cortical and cancellous bone volume, density, and strength. RANKL inhibitors also prevent focal bone loss that occurs in animal models of rheumatoid arthritis and bone metastasis. Clinical trials are exploring the effects of denosumab, a fully human anti-RANKL antibody, on bone loss in patients with osteoporosis, bone metastasis, myeloma, and rheumatoid arthritis.