Tacrolimus and cyclosporine A inhibit human osteoclast formation via targeting the calcineurin-dependent NFAT pathway and an activation pathway for c-Jun or MITF in rheumatoid arthritis

Machine Learning Accelerates Screening of Osteoclast Differentiation Inhibitors from Natural Products

Natural products that inhibit osteoclast differentiation are promising therapeutic and preventive agents for osteoporosis. Conventionally, identifying osteoclast differentiation involves visual inspection of the microscope images of stained osteoclasts. In this study, a supervised machine learning model was developed to classify bright-field microscope images of osteoclasts without staining. The model was used to screen a compound library, and osteoclast differentiation inhibitors were identified, demonstrating the validity of our method. Next, an in-house library of fungal extracts was screened, and pinolidoxin was revealed as an inhibitor of osteoclast differentiation. Our machine learning method enabled accurate, objective, and high-throughput evaluation of osteoclast differentiation and efficient screening of the inhibitors from natural product extracts. This study represents the first machine learning classification developed to evaluate the inhibitory activity of natural products in osteoclast differentiation.

Cell-specific gene networks and drivers in rheumatoid arthritis synovial tissues

Rheumatoid arthritis (RA) is a common autoimmune and inflammatory disease characterized by inflammation and hyperplasia of the synovial tissues. RA pathogenesis involves multiple cell types, genes, transcription factors (TFs) and networks. Yet, little is known about the TFs, and key drivers and networks regulating cell function and disease at the synovial tissue level, which is the site of disease. In the present study, we used available RNA-seq databases generated from synovial tissues and developed a novel approach to elucidate cell type-specific regulatory networks on synovial tissue genes in RA. We leverage established computational methodologies to infer sample-specific gene regulatory networks and applied statistical methods to compare network properties across phenotypic groups (RA versus osteoarthritis). We developed computational approaches to rank TFs based on their contribution to the observed phenotypic differences between RA and controls across different cell types. We identified 18 (fibroblast-like synoviocyte), 16 (T cells), 19 (B cells) and 11 (monocyte) key regulators in RA synovial tissues. Interestingly, fibroblast-like synoviocyte (FLS) and B cells were driven by multiple independent co-regulatory TF clusters that included MITF, HLX, BACH1 (FLS) and KLF13, FOSB, FOSL1 (B cells). However, monocytes were collectively governed by a single cluster of TF drivers, responsible for the main phenotypic differences between RA and controls, which included RFX5, IRF9, CREB5. Among several cell subset and pathway changes, we also detected reduced presence of Natural killer T (NKT) cells and eosinophils in RA synovial tissues. Overall, our novel approach identified new and previously unsuspected Key driver genes (KDG), TF and networks and should help better understanding individual cell regulation and co-regulatory networks in RA pathogenesis, as well as potentially generate new targets for treatment.

Galectin-9 expression correlates with therapeutic effect in rheumatoid arthritis

Galectin-9 (Gal-9) is a multifunctional immunomodulatory factor highly expressed in RA. This study aimed to investigate the expression of Gal-9 and its correlation with disease activity and therapeutic response in RA patients. Active RA patients were enrolled and treated with tacrolimus (TAC) alone or in combination therapy for 12 weeks in a prospective cohort study. Clinical and immunological parameters were recorded at baseline and week 12. We measured Gal-9 expression in different T cell subsets and in plasma. The disease activity of RA patients decreased after treatment. At baseline, the Gal-9 expression percentage was higher in the group with severe disease than in mild or moderate groups. After treatment, the Gal-9 expression in CD3⁺, CD4⁺, CD8⁺ and CD4^-CD8⁻ cell subsets decreased, as well as Gal-9 mean fluorescence intensity in CD3⁺, CD4⁺ and CD8⁺ T cells. Similarly, plasma Gal-9 levels were lower at week 12 than at baseline. Good responders showed significantly lower Gal-9 expression on CD3⁺ and CD4⁺ T cell subsets and lower plasma Gal-9 levels than poor responders. Gal-9 expression positively correlates with disease activity in RA patients. Gal-9 can be regarded as a new biomarker for evaluating RA activity and therapeutic effect, including TAC.

Osteoclastogenesis from bone marrow cells during estrogen-induced medullary bone formation in Japanese quails

Osteoclasts are differentiated from hematopoietic mononuclear cells by regulation of the receptor activator of nuclear factor kappa-B (RANK)/receptor activator of nuclear factor kappa-B ligand (RANKL)/osteoprotegerin (OPG) system. Medullary bone (MB) that forms in the bone marrow of female birds is remodeled under the control of circulating estrogen (E2) during the laying period. Although the osteoclasts of MB are differentiated from mononuclear cells, the mechanism of osteoclastogenesis is not known. We investigated whether MB osteoclastogenesis is regulated by the RANK/RANKL/OPG system using MB from male quails induced with E2. Bone marrow cells (BMCs) differentiate into osteoclasts that have the ability of bone resorption via stimulation of RANKL/M-CSF, but this ability is suppressed by OPG and differentiation is inhibited by calcinurin inhibitors. We found that BMCs at 3 days after E2 administration had high bone osteoclastogenesis ability and colony forming unit-granulocyte/macrophage (CFU-GM)/colony forming unit-macrophage (CFU-M) formation abilities. We conclude that MB osteoclasts are differentiated from BMCs by the RANK/RANKL/OPG system, and that precursor cells of osteoclasts are increased during MB formation.

FK506 prevented bone loss in streptozotocin-induced diabetic rats via enhancing osteogenesis and inhibiting adipogenesis

Background

Type 1 diabetes mellitus (DM) is associated with severe osteoporosis, which is still a great challenge in the clinic. This work aimed to investigate the skeletal effects of FK506 in a rat model of streptozocin induced type 1 DM.

Methods

Rats were divided into three groups: control (CTL), DM rats and DM rats treated with FK506. Dual energy X-ray absorption, micro-computed tomography, bone mechanics and bone histology were used for skeletal analysis. Bone marrow adipocytes infiltrations were detected by oil red O stain and H&E stain. In addition, the protein expression of adipocyte-specific makers (PPAR-γ, C/EBP-αβ), osteoblast-specific markers (Runx2, Osterix) and nuclear translocation of β-catenin in femurs were determined by western blot.

Results

In the study, bone mineral density of femurs and lumbar vertebras in diabetic rats were increased after FK506 administration. FK506 treatment resulted in higher cancellous bone volume but had no significant effect on cortical bones in diabetic rats. The ultimate force and work to failure were increased in DM+FK506 group, while they were reduced in the DM group. Compared with the CTL, the infiltration of bone marrow adipocytes was significantly increased in the DM group, which was reduced after the treatment of FK506. Besides, the expression levels of Runx2 and Osterix were up-regulated, and that of PPAR-γ and C/EBP-α were down-regulated in diabetic rats after FK506 treatment. In addition, the nuclear translocation of β-catenin protein levels were increased in diabetic rats after the treatment of FK506.

Conclusions

Our study indicated that FK506 could alleviate bone loss in diabetic rats. This effects could be due to the results of enhancing osteogenesis and inhibiting adipogenesis, which might be regulated by activation the nuclear translocation of β-catenin.

Anti-receptor activator of nuclear factor κB ligand antibody treatment increases osteoclastogenesis-promoting IL-8 in patients with rheumatoid arthritis

The receptor activator of nuclear factor κB ligand (RANKL) is an important factor for osteoclastogenesis and contributes to the pathology of rheumatoid arthritis (RA); thus, the anti-RANKL antibody (Ab) has been expected to protect joint destruction in RA patients. IL-8 also has osteoclastogenic activity; however, the role of IL-8 in the bone pathology of RA as well as the relation between IL-8 and RANKL remain unclear. In the present study, clinical observation revealed serum IL-8 levels of 611 pg ml-1 in RA patients with anti-RANKL Ab and 266 pg ml-1 in the same patients without anti-RANKL Ab. In vitro assay showed that anti-RANKL Ab induced production of IL-8 from pre-osteoclast-like cells (OCLs), and IL-8 promoted the formation of OCLs from peripheral monocytes even without RANKL activity. We further showed that treatment with FK506 (tacrolimus) possibly inhibits the increase in IL-8 levels in RA patients with anti-RANKL Ab, and in vitro assay confirmed that FK506 suppressed IL-8 production in pre-OCLs. These results suggest that inhibition of RANKL induces the change in osteoclastogenesis-promoting factor from RANKL to IL-8, and FK506 may be a valuable combination drug to support the use of anti-RANKL Ab in treatment of RA.

AP-1 and Mitf interact with NFATc1 to stimulate cathepsin K promoter activity in osteoclast precursors

Cathepsin K (CTSK) is a secreted protease that plays an essential role in osteoclastic bone resorption and osteoporotic bone loss. We have previously shown that activator protein 1 (AP-1) stimulates CTSK promoter activity and that proximal nuclear factor of activated T cells cytoplasmic 1 (NFATc1)-binding sites play a major role in the stimulation of CTSK gene expression by receptor activator of NFκB ligand (RANKL). In the present study, we have extended these observations and further dissected the effects of transcription factors involved in the regulation of CTSK gene expression. Our aim was to investigate the cooperative interplay among transcription factors AP-1, microphthalmia-associated transcription factor (Mitf), and NFATc1, and the consequent regulatory effects on CTSK transcription. Experiments were carried out in RAW 264.7 cells, which can be readily differentiated to osteoclasts upon RANKL stimulation. Our data show that AP-1, Mitf, and NFATc1 are capable of independently stimulating CTSK promoter activity. A combination of any two factors further enhances CTSK promoter activity, with the combination of AP-1 (c-fos/c-jun) and NFATc1 inducing the largest increase. We further identify a synergistic effect when all three factors cooperate intimately at the proximal promoter region, yielding maximal transcriptional upregulation of the CTSK promoter. RANKL induces temporal localization of AP-1 and NFATc1 to the CTSK promoter. These results suggest that the interaction of multiple transcription factors mediate a maximal response to RANKL-induced CTSK gene expression.

Genetic contributions to lupus nephritis in a multi-ethnic cohort of systemic lupus erythematous patients

OBJECTIVE

African Americans, East Asians, and Hispanics with systemic lupus erythematous (SLE) are more likely to develop lupus nephritis (LN) than are SLE patients of European descent. The etiology of this difference is not clear, and this study was undertaken to investigate how genetic variants might explain this effect.

METHODS

In this cross-sectional study, 1244 SLE patients from multiethnic case collections were genotyped for 817,810 single-nucleotide polymorphisms (SNPs) across the genome. Continental genetic ancestry was estimated utilizing the program ADMIXTURE. Gene-based testing and pathway analysis was performed within each ethnic group and meta-analyzed across ethnicities. We also performed candidate SNP association tests with SNPs previously established as risk alleles for SLE, LN, and chronic kidney disease (CKD). Association testing and logistic regression models were performed with LN as the outcome, adjusted for continental ancestries, sex, disease duration, and age.

RESULTS

We studied 255 North European, 263 South European, 238 Hispanic, 224 African American and 264 East Asian SLE patients, of whom 606 had LN (48.7%). In genome-wide gene-based and candidate SNP analyses, we found distinct genes, pathways and established risk SNPs associated with LN for each ethnic group. Gene-based analyses showed significant associations between variation in ZNF546 (p = 1.0E-06), TRIM15 (p = 1.0E-06), and TRIMI0 (p = 1.0E-06) and LN among South Europeans, and TTC34 (p = 8.0E-06) was significantly associated with LN among Hispanics. The SNP rs8091180 in NFATC1 was associated with LN (OR 1.43, p = 3.3E-04) in the candidate SNP meta-analysis with the highest OR among African-Americans (OR 2.17, p = 0.0035).

CONCLUSION

Distinct genetic factors are associated with the risk of LN in SLE patients of different ethnicities. CKD risk alleles may play a role in the development of LN in addition to SLE-associated risk variants. These findings may further explain the clinical heterogeneity of LN risk and response to therapy observed between different ethnic groups.

Tacrolimus regulates endoplasmic reticulum stress-mediated osteoclastogenesis and inflammation: In vitro and collagen-induced arthritis mouse model

Tacrolimus is an immunosuppressive drug that inhibits the release of inflammatory cytokines involved in rheumatoid arthritis development by blocking T cell activation. "Endoplasmic reticulum stress," an imbalance between protein folding load and capacity leading to the accumulation of unfolded proteins in the endoplasmic reticulum lumen, has been implicated in rheumatoid arthritis and other inflammatory and metabolic diseases. We aimed to investigate the effect of tacrolimus on endoplasmic reticulum stress-mediated osteoclastogenesis and inflammation and elucidate the underlying mechanisms. In vitro studies were performed using mouse bone marrow cells that were cultured with or without interleukin-1β, thapsigargin, or tacrolimus to induce osteoclast differentiation. A mouse model of arthritis was established by immunizing mice with bovine type II collagen. Tacrolimus was orally administered to mice from day 20 to 45 following the initial immunization, and histopathological changes and expression of specific biomarkers of endoplasmic reticulum stress-mediated inflammatory signaling pathways were examined. In vitro, tacrolimus inhibited receptor activator of nuclear factor-κB ligand-mediated osteoclast formation augmented by interleukin-1β, thapsigargin, or both. Furthermore, tacrolimus inhibited glucose-regulated protein (GRP78), protein kinase R-like endoplasmic reticulum kinase, inositol-requiring enzyme 1 (IRE 1), and activating transcription factor 6 (ATF6) augmented by interleukin-1β, thapsigargin, or both. Tacrolimus significantly ameliorated osteolysis and endoplasmic reticulum stress intensity in mice. Simultaneously, it reduced inflammatory cell infiltration, osteoclastogenesis, and inflammatory responses by inhibiting GRP78, IRE 1, and ATF6. These findings suggest that tacrolimus exhibits an anti-inflammation effect in rheumatoid arthritis and might inhibit joint damage progression by inhibiting endoplasmic reticulum stress.

Impairment of early fracture healing by skeletal muscle trauma is restored by FK506

Background

Heightened local inflammation due to muscle trauma or disease is associated with impaired bone regeneration.

Methods

We hypothesized that FK506, an FDA approved immunomodulatory compound with neurotrophic and osteogenic effects, will rescue the early phase of fracture healing which is impaired by concomitant muscle trauma in male (~4 months old) Lewis rats. FK506 (1 mg/kg; i.p.) or saline was administered systemically for 14 days after an endogenously healing tibia osteotomy was created and fixed with an intermedullary pin, and the overlying tibialis anterior (TA) muscle was either left uninjured or incurred volumetric muscle loss injury (6 mm full thickness biopsy from middle third of the muscle).

Results

The salient observations of this study were that 1) concomitant TA muscle trauma impaired recovery of tibia mechanical properties 28 days post-injury, 2) FK506 administration rescued the recovery of tibia mechanical properties in the presence of concomitant TA muscle trauma but did not augment mechanical recovery of an isolated osteotomy (no muscle trauma), 3) T lymphocytes and macrophage presence within the traumatized musculature were heightened by trauma and attenuated by FK506 3 days post-injury, and 4) T lymphocyte but not macrophage presence within the fracture callus were attenuated by FK506 at 14 days post-injury. FK506 did not improve TA muscle isometric torque production

Conclusion

Collectively, these findings support the administration of FK506 to ameliorate healing of fractures with severe muscle trauma comorbidity. The results suggest one potential mechanism of action is a reduction in local T lymphocytes within the injured musculoskeletal tissue, though other mechanisms to include direct osteogenic effects of FK506 require further investigation.

Electronic supplementary material

The online version of this article (doi:10.1186/s12891-017-1617-y) contains supplementary material, which is available to authorized users.

The effectiveness of new triple combination therapy using synthetic disease-modifying anti-rheumatic drugs with different pharmacological function against rheumatoid arthritis: the verification by an in vitro and clinical study

The study aims to confirm the feasibility of new oral triple combination therapy using methotrexate (MTX), mizoribine (MZR), and tacrolimus (TAC) in patients with rheumatoid arthritis (RA) by in vitro and clinical analyses. Triple therapy with a combination of MTX, MZR, and TAC was used for an in vitro study with osteoclasts and a prospective clinical study in order to show the efficacy of these agents against refractory RA. In particular, low-dose TAC or MZR was added to treat 14 patients with RA that was resistant to MTX + MZR or MTX + TAC dual therapy. The combination of three pharmacological agents showed statistically significant differences to reduce differentiation induction and activity of osteoclasts compared with single and double agents. In clinical use, triple therapy showed a statistically significant difference in the improvement of Disease Activity Score-28-erythrocyte sedimentation rate and the Simple Disease Activity Index score at around 8 months. Additionally, the serum matrix metalloproteinase-3 level significantly decreased. No patients dropped out because of adverse effects. Based on this in vitro and prospective clinical study, oral triple therapy might be effective against refractory RA. Furthermore, this therapy might be safe and economical for clinical practice.

Randomized controlled studies on the efficacy of antiarthritic agents in inhibiting cartilage degeneration and pain associated with progression of osteoarthritis in the rat

Background

As an initial step in the development of a local therapeutic to treat osteoarthritis (OA), a number of agents were tested for their ability to block activation of inflammation through nuclear factor κ-light-chain-enhancer of activated B cells (NF-κB), subchondral bone changes through receptor activator of nuclear factor κB ligand (RANKL)-mediated osteoclastogenesis, and proteolytic degradation through matrix metalloproteinase (MMP)-13 activity. Candidates with low toxicity and predicted efficacy were further examined using either of two widely accepted models of OA joint degeneration in the rat: the monoiodoacetic acid (MIA) model or the medial meniscal tear/medial collateral ligament tear (MMT/MCLT) model.

Methods

Potential therapeutics were assessed for their effects on the activation of nuclear factor (NF)-κB, RANKL-mediated osteoclastogenesis, and MMP-13 activity in vitro using previously established assays. Toxicity was measured using HeLa cells, a synovial cell line, or primary human chondrocytes. Drugs predicted to perform well in vivo were tested either systemically or via intraarticular injection in the MIA or the MMT/MCLT model of OA. Pain behavior was measured by mechanical hyperalgesia using the digital Randall-Selitto test (dRS) or by incapacitance with weight bearing (WB). Joint degeneration was evaluated using micro computed tomography and a comprehensive semiquantitative scoring of cartilage, subchondral bone, and synovial histopathology.

Results

Several agents were effective both in vitro and in vivo. With regard to pain behavior, systemically delivered clonidine was superior in treating MIA-induced changes in WB or dRS, while systemic clonidine, curcumin, tacrolimus, and fluocinolone were all somewhat effective in modifying MMT/MCLT-induced changes in WB. Systemic tacrolimus was the most effective in slowing disease progression as measured by histopathology in the MMT/MCLT model.

Conclusions

All of the agents that demonstrated highest benefit in vivo, excepting clonidine, were found to inhibit MMP-13, NF-κB, and bone matrix remodeling in vitro. The MIA and MMT/MCLT models of OA, previously shown to possess inflammatory characteristics and to display associated pain behavior, were affected to different degrees by the same drugs. Although no therapeutic was remarkable across all measures, the several which showed the most promise in either model merit continued study with alternative dosing and therapeutic strategies.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-016-0921-5) contains supplementary material, which is available to authorized users.

Novel heterocyclic ring-fused oleanolic acid derivatives as osteoclast inhibitors for osteoporosis

A series of novel oleanolic acid (OA) derivatives were synthesized via modifications of the A-ring and C28-amides of OA, and their anti-bone resorption activities were evaluated in vitro and in vivo.

Concomitant methotrexate and tacrolimus augment the clinical response to abatacept in patients with rheumatoid arthritis with a prior history of biological DMARD use

This observational retrospective study examined whether abatacept efficacy could be augmented with concomitant methotrexate (MTX) or tacrolimus (TAC) in patients with rheumatoid arthritis (RA) who experienced failure with prior biological disease-modifying antirheumatic drugs (DMARDs) and in whom favorable therapeutic efficacy is difficult to achieve. All patients with a prior biological DMARD history who were treated with abatacept for 52 weeks and registered in a Japanese multicentre registry were included. Clinical efficacy and safety of abatacept according to the concomitant drug used, i.e., none (ABT-mono), MTX (ABT-MTX), and TAC (ABT-TAC), were compared. A greater mean percent change of DAS28-ESR was observed in the ABT-TAC group compared with the ABT-mono group at weeks 12 (-20.5 vs. -5.4 %, p = 0.035) and 24 (-25.0 vs. -11.0 %, p = 0.036). ABT-MTX and ABT-TAC groups had a significantly higher proportion of patients who achieved low disease activity (LDA) within 52 weeks compared with the respective baselines, while no significant change was observed in the ABT-mono group. A higher proportion of patients in the ABT-TAC group achieved EULAR moderate response compared with the ABT-mono group at week 52 (66.7 vs. 35.0 %, p = 0.025). Multivariate logistic regression analysis revealed that concomitant TAC use was independently associated with the achievement of LDA and EULAR response at 52 weeks, while concomitant MTX use was not. Concomitant TAC use may offer a suitable option for RA patients treated with abatacept after prior biological DMARD failure, likely because both abatacept and TAC affect T cell activation.

The calcineurin inhibitor tacrolimus as a new therapy in severe cherubism

Cherubism is a rare genetic disorder characterized by extensive growth of a bilateral granuloma of the jaws, resulting in facial disfigurement. Cherubism is caused by gain-of-function mutations in the SH3BP2 gene, leading to overactivation of nuclear factor of activated T cells, cytoplasmic 1 (NFATc1)-dependent osteoclastogenesis. Recent findings in human and mouse cherubism have suggested that calcineurin inhibitors might be drug candidates in cherubism medical treatment. A 4-year-old boy with aggressive cherubism was treated with the calcineurin inhibitor tacrolimus for 1 year, and clinical, radiological, and molecular data were obtained. Immunohistologic analysis was performed to compare preoperative and postoperative NFATc1 staining and tartrate resistant acid phosphatase (TRAP) activity. Real-time PCR was performed to analyze the relative expression levels of OPG and RANKL. After tacrolimus therapy, the patient showed significant clinical improvement, including stabilization of jaw size and intraosseous osteogenesis. Immunohistologic analyses on granuloma showed that tacrolimus caused a significant reduction in the number of TRAP-positive osteoclasts and NFATc1 nuclear staining in multinucleated giant cells. Molecular analysis showed that tacrolimus treatment also resulted in increased OPG expression. We present the first case of effective medical therapy in cherubism. Tacrolimus enhanced bone formation by stimulating osteogenesis and inhibiting osteoclastogenesis.

Praeruptorin A inhibits in vitro migration of preosteoclasts and in vivo bone erosion, possibly due to its potential to target calmodulin

Excessive activity and/or increased number of osteoclasts lead to bone resorption-related disorders. Here, we investigated the potential of praeruptorin A to inhibit migration/fusion of preosteoclasts in vitro and bone erosion in vivo. Praeruptorin A inhibited the RANKL-induced migration/fusion of preosteoclasts accompanied by the nuclear translocation of NFATc1, a master regulator of osteoclast differentiation. Antimigration/fusion activity of praeruptorin A was also confirmed by evaluating the mRNA expression of fusion-mediating molecules. In silico binding studies and several biochemical assays further revealed the potential of praeruptorin A to bind with Ca(2+)/calmodulin and inhibit its downstream signaling pathways, including the Ca(2+)/calmodulin-CaMKIV-CREB and Ca(2+)/calmodulin-calcineurin signaling axis responsible for controlling NFATc1. In vivo application of praeruptorin A significantly reduced lipopolysaccharide-induced bone erosion, indicating its possible use to treat bone resorption-related disorders. In conclusion, praeruptorin A has the potential to inhibit migration/fusion of preosteoclasts in vitro and bone erosion in vivo by targeting calmodulin and inhibiting the Ca(2+)/calmodulin-CaMKIV-CREB-NFATc1 and/or Ca(2+)/calmodulin-calcineurin-NFATc1 signaling axis.

Adverse skeletal effects of drugs - beyond Glucocorticoids

Osteoporotic fractures are an important public health problem with significant individual and societal costs. In addition to the major risk factors for osteoporotic fracture, low bone mineral density (BMD), age, low body weight and history of fracture or falls, some drugs are now considered to be important secondary risk factor for bone loss and fracture, particularly amongst predisposed individuals. Currently available data are often generated from small observational clinical studies, making risk assessment and development of management guidelines difficult. In many cases, the exposed population has a low baseline risk for fracture and additional assessment and treatment may not be necessary. In this review, we focus on drugs other than glucocorticoids identified as potentially causing adverse skeletal effects, summarizing the existing evidence from preclinical and clinical studies, and suggest recommendations for patient management.

Medication-induced osteoporosis: screening and treatment strategies

Drug-induced osteoporosis is a significant health problem and many physicians are unaware that many commonly prescribed medications contribute to significant bone loss and fractures. In addition to glucocorticoids, proton pump inhibitors, selective serotonin receptor inhibitors, thiazolidinediones, anticonvulsants, medroxyprogesterone acetate, aromatase inhibitors, androgen deprivation therapy, heparin, calcineurin inhibitors, and some chemotherapies have deleterious effects on bone health. Furthermore, many patients are treated with combinations of these medications, possibly compounding the harmful effects of these drugs. Increasing physician awareness of these side effects will allow for monitoring of bone health and therapeutic interventions to prevent or treat drug-induced osteoporosis.

Identification of novel transcription factors in osteoclast differentiation using genome-wide analysis of open chromatin determined by DNase-seq

Clarification of the mechanisms underlying osteoclast differentiation enables us to understand the physiology of bone metabolism as well as the pathophysiology of bone diseases such as osteoporosis. Recently, it has been reported that epigenetics can determine cell fate and regulate cell type-specific gene expression. However, little is known about epigenetics during osteoclastogenesis. To reveal a part of epigenetics, especially focused on chromatin dynamics, during early osteoclastogenesis and to identify novel transcription factors involved in osteoclastogenesis, we performed a genome-wide analysis of open chromatin during receptor activator of NF-κB ligand (RANKL)-induced osteoclastogenesis using DNase I hypersensitive sites sequencing (DNase-seq). DNase-seq was performed using the extracted nuclei from RAW264 cells treated with or without RANKL for 24 hours, followed by several bioinformatic analyses. DNase I hypersensitive sites (DHSs) were dynamically changed during RANKL-induced osteoclastogenesis and they accumulated in promoter regions. The distributions of DHSs among cis-regulatory DNA regions were identical regardless of RANKL stimulation. Motif discovery analysis successfully identified well-known osteoclastogenic transcription factors including Jun, CREB1, FOS, ATF2, and ATF4, but also novel transcription factors for osteoclastogenesis such as Zscan10, Atf1, Nrf1, and Srebf2. siRNA knockdown of these identified novel transcription factors impaired osteoclastogenesis. Taken together, DNase-seq is a useful tool for comprehension of epigenetics, especially chromatin dynamics during osteoclastogenesis and for identification of novel transcription factors involved in osteoclastogenesis. This study may reveal underlying mechanisms that determine cell type-specific differentiation of bone cells and may lead to investigation of novel therapeutic targets for osteoporosis.

Role of suppressors of cytokine signaling 3 in bone inflammatory responses

Suppressor of cytokine signaling 3 (SOCS3) is a potent regulator of cytokine signaling in macrophages and T cells. In recent studies, evidence has been provided for SOCS3 activation in all major bone cells including osteoclasts, chondrocytes, synoviocytes, and osteoblasts. The investigation of SOCS3 function in bone remodeling systems implicates SOCS3 as a key signaling molecule in bone cell-mediated inflammatory responses. Both pro- and anti-inflammatory functions of SOCS3 have been demonstrated in different types of bone cells. This review provides an overview of the important role of SOCS3 in inflammatory responses of various bone cells and in bone inflammatory disorders such as periodontal disease and arthritis. Understanding the roles of SOCS3 in inflammatory diseases of bone and joints such as arthritis, osteomyelitis, and periodontal diseases is critical to revealing insights into signaling pathways that can be manipulated in potential therapeutic approaches.

Inhibitory effect of tacrolimus on progression of joint damage in patients with rheumatoid arthritis

AIM

To examine the inhibitory effect of tacrolimus on radiographic joint damage in patients with rheumatoid arthritis (RA).

METHODS

Thirty-eight patients with RA resistant or intolerant to conventional disease-modifying anti-rheumatic drugs were administered tacrolimus and analyzed retrospectively. Disease activity and clinical response were evaluated by Disease Activity Score in 28 joints and C-reactive protein (DAS28-CRP) and European League Against Rheumatism (EULAR) response criteria. The progression of joint destruction was evaluated by an estimated yearly change in modified Total Sharp Score (mTSS).

RESULTS

Good or moderate response rate according to EULAR response criteria was seen in 63.2%, 63.2%, 73.7% and 65.8% of patients at 3, 6, 12, and 24 months, respectively. The rate of patients with low disease activity or remission reached 47.3% and 50.0% at 12 and 24 months, respectively. Progression of joint damage, evaluated as yearly change in mTSS (ΔmTSS), significantly decreased from 11.4 at baseline to 2.63 in the first year and 0.69 in the second year of tacrolimus treatment.

CONCLUSION

These findings suggest tacrolimus has the potential to inhibit progression of joint damage in established RA.

Regulatory effect of calcineurin inhibitor, tacrolimus, on IL-6/sIL-6R-mediated RANKL expression through JAK2-STAT3-SOCS3 signaling pathway in fibroblast-like synoviocytes

Introduction

This study investigated whether the calcineurin inhibitor, tacrolimus, suppresses receptor activator of NF-κB ligand (RANKL) expression in fibroblast-like synoviocytes (FLS) through regulation of IL-6/Janus activated kinase (JAK2)/signal transducer and activator of transcription-3 (STAT3) and suppressor of cytokine signaling (SOCS3) signaling.

Methods

The expression of RANKL, JAK2, STAT3, and SOCS3 proteins was assessed by western blot analysis, real-time PCR and ELISA in IL-6 combined with soluble IL-6 receptor (sIL-6R)-stimulated rheumatoid arthritis (RA)-FLS with or without tacrolimus treatment. The effects of tacrolimus on synovial inflammation and bone erosion were assessed using mice with arthritis induced by K/BxN serum. Immunofluorescent staining was performed to identify the effect of tacrolimus on RANKL and SOCS3. The tartrate-resistant acid phosphatase staining assay was performed to assess the effect of tacrolimus on osteoclast differentiation.

Results

We found that RANKL expression in RA FLS is regulated by the IL-6/sIL-6R/JAK2/STAT3/SOCS3 pathway. Inhibitory effects of tacrolimus on RANKL expression in a serum-induced arthritis mice model were identified. Tacrolimus inhibits RANKL expression in IL-6/sIL-6R-stimulated FLS by suppressing STAT3. Among negative regulators of the JAK/STAT pathway, such as CIS1, SOCS1, and SOCS3, only SOCS3 is significantly induced by tacrolimus. As compared to dexamethasone and methotrexate, tacrolimus more potently suppresses RANKL expression in FLS. By up-regulating SOCS3, tacrolimus down-regulates activation of the JAK-STAT pathway by IL-6/sIL-6R trans-signaling, thus decreasing RANKL expression in FLS.

Conclusions

These data suggest that tacrolimus might affect the RANKL expression in IL-6 stimulated FLS through STAT3 suppression, together with up-regulation of SOCS3.

Regulation of ITAM adaptor molecules and their receptors by inhibition of calcineurin-NFAT signalling during late stage osteoclast differentiation

Osteoclasts are specialised bone resorptive cells responsible for both physiological and pathological bone loss. Osteoclast differentiation and activity is dependent upon receptor activator NF-kappa-B ligand (RANKL) interacting with its receptor RANK to induce the transcription factor, nuclear factor of activated T-cells, cytoplasmic, calcineurin-dependent 1 (NFATc1). The immunoreceptor tyrosine-based activation motif (ITAM)-dependent pathway has been identified as a co-stimulatory pathway in osteoclasts. Osteoclast-associated receptor (OSCAR) and triggering receptor expressed in myeloid cells (TREM2) are essential receptors that pair with adaptor molecules Fc receptor common gamma chain (FcRγ) and DNAX-activating protein 12kDa (DAP12) respectively to induce calcium signalling. Treatment with calcineurin-NFAT inhibitors, Tacrolimus (FK506) and the 11R-VIVIT (VIVIT) peptide, reduces NFATc1 expression consistent with a reduction in osteoclast differentiation and activity. This study aimed to investigate the effects of inhibiting calcineurin-NFAT signalling on the expression of ITAM factors and late stage osteoclast genes including cathepsin K (CathK), Beta 3 integrin (β3) and Annexin VIII (AnnVIII). Human peripheral blood mononuclear cells (PBMCs) were differentiated with RANKL and macrophage-colony stimulating factor (M-CSF) over 10days in the presence or absence of FK506 or VIVIT. Osteoclast formation (as assessed by tartrate resistant acid phosphatase (TRAP)) and activity (assessed by dentine pit resorption) were significantly reduced with treatment. Quantitative real-time polymerase chain reaction (qRT-PCR) analysis demonstrated that FK506 treatment significantly (p<0.05) reduced the expression of NFATc1, CathK, OSCAR, FcRγ, TREM2 and DAP12 during the terminal stage of osteoclast formation. VIVIT treatment significantly (p<0.05) decreased CathK, OSCAR, FcRγ, and AnnVIII, gene expression. This data suggest FK506 and VIVIT act differently in targeting the calcineurin-NFAT signalling cascade to suppress key mediators of the ITAM pathway during late stage osteoclast differentiation and this is associated with a reduction in both osteoclast differentiation and activity.

Effect of additional administration of tacrolimus in patients with rheumatoid arthritis treated with biologics

OBJECTIVE

To explore the effect of additional administration of tacrolimus to rheumatoid arthritis patients treated with biologics, in whom the effect of biologics is unsatisfactory.

METHODS

Tacrolimus was administered if the effect of biologics was unsatisfactory for 24 weeks at least in terms of laboratory data or DAS28 level: ESR, CRP level and DAS28 level were not below 15 mm/h, 0.2 mg/dl or 2.6, respectively.

RESULTS

Tacrolimus administered in addition to biologics was significantly effective for suppressing the activity of rheumatoid arthritis in our study. The significant effect of tacrolimus appeared at the 4th week. The effect of tacrolimus achieved quite significant level at the 54th week (p< 0.0001).

CONCLUSION

Tacrolimus may be a promising candidate to suppress the disease activity of rheumatoid arthritis refractory to the conventional treatment with biologics.

Tacrolimus potently inhibits human osteoclastogenesis induced by IL-17 from human monocytes alone and suppresses human Th17 differentiation

Tacrolimus (FK506, Prograf®) is an orally available, T cell specific and anti-inflammatory agent that has been proposed as a therapeutic drug in rheumatoid arthritis (RA) patients. It has been known that T cells have a critical role in the pathogenesis of RA. Recent studies suggest that Th17 cells, which mainly produce IL-17, are involved in many autoimmune inflammatory disease including RA. The present study was undertaken to assess the effect of tacrolimus on IL-17-induced human osteoclastogenesis and human Th17 differentiation. Human CD14(+) monocytes were cultured in the presence of macrophage-colony stimulating factor (M-CSF) and IL-17. From day 4, tacrolimus was added to these cultures. Osteoclasts were immunohistologically stained for vitronectin receptor 10days later. IL-17 production from activated T cells stimulated with IL-23 was measured by enzyme-linked immunosorbent assay (ELISA). Th17 differentiation from naïve T cells was assayed by flow cytometry. Tacrolimus potently inhibited IL-17-induced osteoclastogenesis from human monocytes and osteoclast activation. Addition of tacrolimus also reduced production of IL-17 in human activated T cells stimulated with IL-23. Interestingly, the population of human IL-17(+)IFN-γ(-) CD4 T cells or IL-17(+)TNF-α(+) CD4 T cells were decreased by adding of tacrolimus. The present study demonstrates that the inhibitory effect of tacrolimus on IL-17-induced osteoclastogenesis from human monocytes. Tacrolimus also inhibited expression of IL-17 or TNF-α by reducing the proportion of Th17, suggesting that therapeutic effect on Th17-associated disease such as RA, inflammatory bowel disease, multiple sclerosis, psoriasis, or allograft rejection.

A calcium-sensitive promoter construct for gene therapy

Targeting diseased cells is a challenging issue in both pharmacological and biological therapeutics. Gene therapy is emerging as a novel approach for treating rare diseases and for illnesses for which there is no other alternative. An important limitation of gene therapy has been the off-target effects and therefore efforts have been focused on increasing the specificity of gene transfer to the targeted organ. Here, we describe a promoter containing six nuclear factor of activated T cells (NFAT) consensus sequences, which is as efficient as the cytomegalovirus (CMV) promoter to drive expression in vascular smooth muscle cells both in vitro and in vivo. In contrast to the CMV promoter it is activated in a Ca(2+)-dependent manner after endoplasmic reticulum depletion and allows the transgene expression only in proliferative/diseased cells. Overexpression of sarco/endoplasmic reticulum (SR/ER) Ca(2+) ATPase 2a under the control of this NFAT promoter inhibits restenosis after angioplasty in rats. In conclusion, this promoter may be useful for gene therapy in vascular proliferative diseases and other diseases involving upregulation of the NFAT pathway.

Tacrolimus treatment increases bone formation in patients with rheumatoid arthritis

Tacrolimus is a calcineurin inhibitor, and it is used for the treatment of rheumatoid arthritis (RA). It works by inhibiting nuclear factor of activated T cells and inducting immunosuppression. This study aims to evaluate the influence of tacrolimus on the bone metabolism of patients with RA. Twenty-eight RA patients in three centers received tacrolimus 3 mg once daily for 24 weeks. Blood samples for evaluating bone metabolism and cytokines were collected at Weeks 0 and 24. We measured the serum C-telopeptide of type I collagen (sCTx-I), osteocalcin and inflammatory cytokines. We analyzed the data using the Kruskal-Wallis test and Spearman's correlation. IL-2 and IL-6 were significantly decreased after the administration of tacrolimus (p = 0.027 and p = 0.024). There was no significant difference in the serum level of sCTx-I before and after treatment. The level of serum osteocalcin at Week 24 was significantly increased compared to the level at Week 0 (p = 0.002). The increase of osteocalcin was correlated with the reductions of IL-2 and IFN-γ (r = 0.405, p = 0.033 and r = 0.380, p = 0.046, respectively). Tacrolimus treatment increased bone formation markers in RA patients. This suggests that tacrolimus may play a role to inhibit bone erosion by increasing bone formation as well as improving the clinical symptoms of RA.

Cyclosporine immunomodulation retards regeneration of surgically transected corneal nerves

PURPOSE

To determine whether immunomodulation with cyclosporine (CsA) affects reinnervation after surgical transection of stromal nerves.

METHODS

Thy1-YFP+ neurofluorescent mice underwent lamellar corneal surgery and 3 days later, received artificial tears or CsA eye drops for 6 weeks. Serial in vivo wide-field stereofluorescent microscopy was performed to determine changes in nerve fiber density (NFD). Real-time quantitative PCR was performed to determine the expression of neurotrophins and cytokines (IL6 and TNF-α). Compartmental culture of trigeminal ganglion neurons was performed in Campenot devices to determine whether CsA directly affects neurite outgrowth.

RESULTS

Yellow fluorescent protein (YFP)-positive cells significantly increased at 3 and 7 days after surgery. The number of YFP-positive cells in the cornea was significantly lower in the CsA group than that in the control group. The percentage increase in NFD between 2 to 6 weeks was greater in the control group (80% ± 10%, P = 0.05) than that in the CsA group (39% ± 21%). The CsA group also exhibited lower expression of IL6 and TNF-α (P = 0.01). In compartmental culture experiments, neurite outgrowth toward side compartments containing CsA was significantly less (2.29 ± 0.4 mm, P = 0.01) than that toward side compartments containing vehicle (3.97 ± 0.71 mm).

CONCLUSIONS

Immunomodulation with CsA reduces the expression of cytokines (IL6) in the cornea and retards regenerative sprouting from transected corneal stromal nerve trunks. In addition, CsA has a direct growth inhibitory action on neurites as well.

[Effects of rat serum containing Chinese herbal medicine Sangen Decoction on osteoclastogenesis and bone resorption of osteoclasts induced by polymethylmethacrylate particles]

OBJECTIVE

To investigate the effects of Sangen Decoction, a compound Chinese herbal medicine, on osteoclastogenesis and bone resorption function of osteoclasts induced by polymethylmethacrylate particles in vitro.

METHODS

Macrophage colony stimulating factor (M-CSF) and receptor activator of nuclear factor-κB ligand (RANKL) were used to induce differentiation of bone marrow-derived macrophages (BMMs) towards osteoclasts. BMMs and polymethylmethacrylate particles with ratio of 1:3 were added to the 24-well plate and 96-well plate with bone slices respectively. A total of 50 male SD rats were divided into 5 groups randomly with each group containing 10 rats. After being treated with different drugs, serum samples of rats in each group were extracted, i.e., the blank serum, Western medicine (ibandronate) serum and high-, medium-, and low-dose Sangen Decoction serum and were added to the medium respectively. The tartrate-resistant acid phosphatase (TRAP) staining was used to identify the differentiation of BMMs and for counting of osteoclasts. Area of lacuna induced by osteoclast bone resorption on the bone slices was measured by computer image processing.

RESULTS

Numbers of osteoclasts of treatment groups were less than that of blank group by TRAP staining (P<0.05); numbers of osteoclasts of positive control group and high-dose Sangen Decoction group were much lower than those of medium- and low-dose Sangen Decoction groups (P<0.05), and no difference was found between Western medicine group and high-dose Sangen Decoction group (P>0.05). In bone resorption assay, area of lacuna of blank group was larger than those of treatment groups (P<0.05); areas of lacuna of Western medicine group and high-dose Sangen Decoction group were much smaller than those of medium- and low-dose Sangen Decoction groups (P<0.05), and no difference was found between Western medicine group and high-dose Sangen Decoction group (P>0.05).

CONCLUSION

Sangen Decoction can inhibit osteoclastogenesis induced by polymethylmethacrylate particles as well as bone resorption function of osteoclasts.

Is there a role for NFAT inhibitors in the prevention of bone destruction?

Pathologic conditions resulting from excessive bone destruction include osteoporosis, rheumatoid arthritis, metastases, periprosthetic osteolysis, cherubism, and others. A scarcity of molecular targets in bone has thwarted the development of drugs to combat these conditions. Nuclear factor of activated T-cells (NFAT) is a master regulator of osteoclastogenesis and is induced by RANKL. The immunosuppressive drugs, Cyclosporin A and Tacrolimus, inhibit osteoclast formation by targeting the NFAT/calcineurin pathway. These NFAT inhibitors should be considered in the treatment of osteoclastic hyper-resorptive syndromes.

A possible suppressive role of galectin-3 in upregulated osteoclastogenesis accompanying adjuvant-induced arthritis in rats

Galectin-3 is a beta-galactoside-binding animal lectin having pleiotropic effects on cell growth, differentiation, and apoptosis. This lectin has been shown to be involved in phagocytosis by macrophages and in inflammation. Here we investigated an involvement of galectin-3 in the regulatory process of inflammatory bone resorption in rats with adjuvant-induced arthritis (AA rats) accompanying severe bone destruction in the ankle joints. The protein level of galectin-3 in the ankle-joint extracts was markedly augmented at week 3 after adjuvant injection, at the time when severe bone destruction was observed. Immunohistochemical analysis revealed an extremely high expression of galectin-3 in macrophages and granulocytes infiltrated in the area of severe bone destruction. To estimate the role of galectin-3 in osteoclastogenesis and osteoclastic bone resorption, recombinant galectin-3 was added to in vitro culture systems. Galectin-3 markedly inhibited the formation of osteoclasts in cultures of murine osteoclast precursor cell line as well as in rat bone marrow culture systems. This inhibition was not observed by heat-inactivated galectin-3 or by galectin-7. Although recombinant galectin-3 did not affect signaling through mitogen-activated protein kinase (MAPK) or nuclear factor-kappaB (NF-kappaB), it specifically suppressed the induction of nuclear factor of activated T-cells c1 (NFATc1). Galectin-3 significantly inhibited dentine resorption by mature osteoclasts in vitro. Furthermore, in vivo studies clearly showed a significant suppression of bone destruction and osteoclast recruitment accompanying arthritis, when galectin-3 was injected into the cavity of ankle joint of AA rats. Thus, abundant galectin-3 observed in the area of severe bone destruction may act as a negative regulator for the upregulated osteoclastogenesis accompanying inflammation to prevent excess bone destruction.

[Toward a non-empirical treatment for rheumatoid arthritis based on its molecular pathology]

Rheumatoid arthritis (RA) is a chronic, disabbling disease that affects individuals during the productive years of their lives. Modern treatment for RA includes the so called "biologic" therapy, which is based on recombinant proteins that modify the biologic processes. These agents have potent therapeutic effects and different mechanisms of action. Nevertheless, therapeutic failure still prevails. Treatment that prevents disability in RA must be started in an early manner, before the development of complications and, ideally, with a minimum possibility of therapeutic failure. As yet, there are no clinical or laboratory criteria to identify those patients with a higher probability of responding to particular types of therapy, delaying control of RA ad affecting the prevention of incapacity. Research into gene diversity through single-nucleotide polymorphisms (SNPs) by means of microarray systems, allows the detailed analysis of gene factors associated to a given disease. SNPs have been recently applied to the study of RA, where the major polymorphisms associated to RA occur primarily in genes that code for proteins related to the initiation of an immune response and/or the control of cellular activity in the immune system, in addition to genes related to tissue repair. The specific meaning of these findings is in its initial stages of research. On the other hand, proteomics relate to the analysis of protein expression profiles at multiple levels. Both types of studies will contribute to the knowledge of patterns of gene expression in RA compared to the general population, and will allow an understanding of the pathogenesis of RA. Moreover, proteomic and genomic profiles can be employed to designs probes that identify individuals with the risk of developing RA, individually predict the response to different therapeutic modalities (pharmacogenomics) and for the follow-up of the biologic response to therapy.

The effect of Cyclosporine A on cardiomyocytes differentiation

Cyclosporine A (CsA) is a powerful immunosuppressive drug which significantly improved the success of organ transplantation; however, the major limiting factors for the drug's clinical use are its long and short term adverse effects. The present study was conducted to examine, in a dose-dependent manner, in a model of cardiogenesis, the effect of CsA on cardiomyocytes differentiation.

T cells are involved in the development of arthritis induced by anti-type II collagen antibody

T cells play an important role in initiating autoimmune responses and maintaining synovial inflammation in rheumatoid arthritis. Although, anti-type II collagen antibody-induced arthritis (CAIA) is generally believed to be a T cell- and B cell-independent model, the detailed pathogenesis of CAIA remains unclear. In the present study, to elucidate the contribution of T cells to the pathogenesis of CAIA, we evaluated the effects of CTLA4 Ig and cyclosporin (CsA). Arthritis was induced in mice by intravenous injection of anti-type II collagen antibody followed by intraperitoneal injection of lipopolysaccharide. CTLA4 Ig was intraperitoneally administered and CsA was subcutaneously administered; then the severity of arthritis was evaluated by scoring the edema and erythema of paws and by measuring hind paw thickness. Paw samples were collected 12 days after the antibody injection, and the mRNA expression levels were analyzed by real-time quantitative polymerase chain reaction. Administration of CTLA4 Ig ameliorated the increases in arthritic score and paw thickness in the later phase, but not in the early phase of arthritis. CsA suppressed the increases in arthritic score and paw thickness in both the early and later phases of arthritis. CTLA4 Ig and CsA suppressed mRNA up-regulation of T-cell markers, CD3 and CD25, and immune response-related mediators, IFN-gamma and IL-12. They also suppressed the up-regulation of macrophage marker, F4/80, and proinflammatory cytokines, TNF-alpha, IL-1beta and IL-6. The results provide direct evidence that arthritis in this model is T-cell activation dependent.

Cyclosporine and tacrolimus for the treatment of rheumatoid arthritis

PURPOSE OF REVIEW

The calcineurin inhibitors cyclosporine and tacrolimus are important treatments for patients with active rheumatoid arthritis, especially in cases of resistance or intolerance to methotrexate or other disease-modifying antirheumatic drugs. Here, we discuss the mechanism, efficacy and safety of cyclosporine and tacrolimus in the treatment of rheumatoid arthritis.

RECENT FINDINGS

Recent clinical trials of cyclosporine have shown the advantages of its combination with methotrexate, glucocorticoids and leflunomide in the treatment of active rheumatoid arthritis. In Japan, tacrolimus monotherapy was found to be quite effective and combination therapy with methotrexate had positive results in an American study. The inhibitory effects of both drugs not only on T lymphocytes, but also on human osteoclast formation, have been demonstrated in basic studies.

SUMMARY

Cyclosporine and tacrolimus are clinically available disease-modifying antirheumatic drugs. Numerous clinical studies have shown the usefulness of these calcineurin inhibitors in monotherapy and also when combined with methotrexate. Although these drugs have similar effects, there are some differences in adverse reactions.

Gingival crevicular fluid levels of RANKL and OPG in periodontal diseases: implications of their relative ratio

AIM

Receptor activator of NF-kappaB ligand (RANKL) and osteoprotegerin (OPG) are a system of molecules that regulate bone resorption. This study aims to compare the levels of RANKL, OPG and their relative ratio in gingival crevicular fluid (GCF) of healthy and periodontal disease subjects.

MATERIAL AND METHODS

GCF was obtained from healthy (n=21), gingivitis (n=22), chronic periodontitis (n=28), generalized aggressive periodontitis (n=25) and chronic periodontitis subjects under immunosuppressant therapy (n=11). RANKL and OPG concentrations in GCF were measured by enzyme-linked immunosorbent assays.

RESULTS

RANKL levels were low in health and gingivitis groups, but increased in all three forms of periodontitis. OPG levels were higher in health than all three periodontitis, or gingivitis groups. There were no differences in RANKL and OPG levels between chronic and generalized aggressive periodontitis groups, whereas these were lower in the immunosuppressed chronic periodontitis group. The RANKL/OPG ratio was significantly elevated in all three periodontitis forms, compared with health or gingivitis, and positively correlated to probing pocket depth and clinical attachment level.

CONCLUSION

GCF RANKL and OPG levels were oppositely regulated in periodontitis, but not gingivitis, resulting in an enhanced RANKL/OPG ratio. This ratio was similar in all three periodontitis groups and may therefore predict disease occurrence.