Interleukin 29 inhibits RANKL-induced osteoclastogenesis via activation of JNK and STAT, and inhibition of NF-κB and NFATc1.

Interleukin (IL)-29 is known to modulate immune functions of monocytes or macrophages. In this study, we investigated the effect and its underlying mechanism of IL-29 on receptor activator of nuclear factor κB ligand (RANKL)-induced osteoclastogenesis using murine macrophage cell line RAW264.7 cells and bone-marrow-derived monocyte/macrophage precursor cells (BMMs), and human peripheral blood mononuclear cells (PBMCs). In response to human recombinant IL-29, cell viability and apoptosis were assessed by Cell Counting Kit-8 and flow cytometry; the osteoclast formation and activity by tartrate-resistant acid phosphatase (TRAP) staining and pit formation assay, respectively; the expression and activation of molecules that associated with osteoclastogenesis by real time-PCR, immunoblotting or immunofluorescent analysis. IL-28 receptor α (IL-28Rα), a specific receptor of IL-29 was expressed on RAW264.7 cells. Although IL-29 did not affect the viability and apoptosis of RAW264.7 cells, it inhibited multinucleated cells in the differentiation of osteoclastogenesis, the bone-resorbing activity of mature osteoclasts and osteoclastic specific genes expression including TRAP, cathepsin K (CTSK), nuclear factor of activated T-cells, cytoplasmic 1 (NFATc1), C-Fos and matrix metallopeptidase 9 (MMP-9). This inhibitory effect of IL-29 was confirmed on BMMs and PBMCs and mediated via IL-28Rα through the activation of Stat1 and 3 and the suppression of nuclear factor kappa B (NF-κB) and NFATc1 nuclear translocation in RAW264.7 cells. In conclusion, IL-29 inhibited osteoclastogenesis via activation of STAT signaling pathway, prevention of NF-κB activation and NFATc1 translocation, and suppression of downstream osteoclastogenic genes expression.

Osteoclast differentiation gene expression profiling reveals chemokine CCL4 mediates RANKL-induced osteoclast migration and invasion via PI3K pathway.

The migration of osteoclasts (OCs) from circulation and bone marrow into bone surface plays a critical role in the pathogenesis of some bone resorptive diseases, such as rheumatoid arthritis and osteoporosis. To date, how the migration of OCs remains unclear. We investigated gene expression profiling in osteoclastic differentiation of bone marrow-derived macrophages (BMMs) into OCs by microarray analysis. We identified 387 genes overexpressed in osteoclastic differentiation of BMMs. Among them, chemokine CCL4 showed a robust up-regulation signal. High expression of CCL4 was validated in primary BMMs and OC precursor cell line RAW264.7 during differentiation into OCs. The CCL4 neutralization decreased RANKL-induced OC precursor cell migration and invasion in Matrigel-coated transwell membranes assay and in vitro wound healing assay. However, CCL4 inhibition did not affect OCs differentiation and differentiation associated gene expression. The CCL4 inhibition promoted the PI3K phosphorylation at 45 to 60 minutes after RANKL stimulation in RAW264.7. This study indicated that chemokine CCL4 is an important regulator for OCs migration via PI3K pathway, providing a novel therapy target for bone resorptive diseases.

Interleukin-29 Enhances Synovial Inflammation and Cartilage Degradation in Osteoarthritis.

We have recently shown that IL-29 was an important proinflammatory cytokine in pathogenesis of rheumatoid arthritis (RA). Inflammation also contributes to the pathogenesis of osteoarthritis (OA). The aim of this study was to investigate the effect and mechanism of IL-29 on cytokine production and cartilage degradation in OA. The mRNA levels of IL-29 and its specific receptor IL-28Ra in peripheral blood mononuclear cells (PBMCs) were significantly increased in OA patients when compared to healthy controls (HC). In the serum, IL-29 protein levels were higher in OA patients than those in HC. Immunohistochemistry revealed that both IL-29 and IL-28Ra were dramatically elevated in OA synovium compared to HC; synovial fibroblasts (FLS) and macrophages were the main IL-29-producing cells in OA synovium. Furthermore, recombinant IL-29 augmented the mRNA expression of IL-1ß, IL-6, IL-8, and matrix-metalloproteinase-3 (MMP-3) in OA FLS and increased cartilage degradation when ex vivo OA cartilage explant was coincubated with OA FLS. Finally, in OA FLS, IL-29 dominantly activated MAPK and nuclear factor-κB (NF-κB), but not Jak-STAT and AKT signaling pathway as examined by western blot. In conclusion, IL-29 stimulates inflammation and cartilage degradation by OA FLS, indicating that this cytokine is likely involved in the pathogenesis of OA.

Clinical analysis of macrophage activation syndrome in adult rheumatic disease: A multicenter retrospective study.

AIM: To evaluate the clinical and laboratory characteristics, prognostic factors, and outcome of adult rheumatic disease-associated macrophage activation syndrome (MAS). METHOD: A multicenter retrospective study was performed across 4 tertiary hospitals in China between January 1, 2017 to December 31, 2019. RESULTS: There were 61 rheumatic disease patients with MAS enrolled into this retrospective clinical study. Fever and hyperferritinemia are the most frequent clinical feature and laboratory abnormality in MAS patients. Serum ferritin > 6000 ng/mL (odds ratio [OR] = 9.46, 95% CI = 2.53-47.13, P = .005) and hemophagocytosis in bone marrow smear (OR = 11.12, 95%, CI = 3.29-50.65, P = .001) were the 2 most prominent predictive factors indicating MAS occurrence. The 90-day all-cause mortality rate of all rheumatic disease patients with MAS was 22.9% (hazards ratio [HR] = 2.15, 95% CI = 0.81-6.78, P = .05). Platelets < 100 × 109 /L (HR = 3.23, 95% CI = 2.51-4.81, P = .01) and ferritin > 6000ng/mL (HR = 6.12, 95% CI = 2.93-16.27, P = .005) were independent predictors of poor outcome in rheumatic disease-associated MAS. CONCLUSION: Macrophage activation syndrome could be a fatal complication in rheumatic disease. Patients presenting with unexplained fever, serum ferritin > 6000 ng/mL, hepatosplenomegaly and cytopenia at baseline should raise the suspicion of MAS. The presence of serum ferritin > 6000 ng/mL, hepatosplenomegaly and low number of platelets was associated with poor outcome.

The Bone Marrow Edema Links to an Osteoclastic Environment and Precedes Synovitis During the Development of Collagen Induced Arthritis.

Objectives: To determine the relationship between bone marrow edema (BME), synovitis, and bone erosion longitudinally using a collagen induced arthritis mice (CIA) model and to explore the potential pathogenic role of BME in bone erosion. Methods: CIA was induced in DBA/1J mice. BME and corresponding clinical symptoms of arthritis and synovitis during the different time points of CIA development were assayed by magnetic resonance imaging (MRI), arthritis sore, and histologic analyses. The expression of osteoclasts (OCs), OCs-related cytokines, and immune cells in bone marrow were determined by flow cytometry, immunohistochemistry, immunofluorescence staining, and real-time PCR. The OCs formation was estimated using in vitro assays. Results: MRI detected BME could emerge at day 25 in 70% mice after the first immunization (n = 10), when there were not any arthritic symptoms, histological or MRI synovitis. At day 28, BME occurred in 90% mice whereas the arthritic symptom and histological synovitis were only presented in 30 and 20% CIA mice at that time (n = 10). The emergence of BME was associated with an increased bone marrow OCs number and an altered distribution of OCs adherent to subchondral bone surface, which resulted in increased subchondral erosion and decreased trabecular bone number during the CIA process. Obvious marrow environment changes were identified after BME emergence, consisting of multiple OCs related signals, including highly expressed RANKL, increased proinflammatory cytokines and chemokines, and highly activated T cells and monocytes. Conclusions: BME reflects a unique marrow "osteoclastic environment," preceding the arthritic symptoms and synovitis during the development of CIA.

Transcription Factor SOX5 Promotes the Migration and Invasion of Fibroblast-Like Synoviocytes in Part by Regulating MMP-9 Expression in Collagen-Induced Arthritis.

Objectives: Fibroblast-like synoviocytes (FLS) exhibit a unique aggressive phenotype in rheumatoid arthritis (RA). Increased FLS migration and subsequent invasion of the extracellular matrix are essential to joint destruction in RA. Our previous research reported that transcription factor SOX5 was highly expressed in RA-FLS. Here, the effects of SOX5 in RA-FLS migration and invasion will be investigated. Methods: The migration and invasion of RA-FLS were evaluated using a transwell chamber assay. The expression of several potential SOX5-targeted genes, including matrix metalloproteinases (MMP-1, 2, 3 and 9), chemokines (CCL4, CCL2, CCR5 and CCR2), and pro-inflammatory cytokines (TNF-α and IL-6), were examined in RA-FLS using SOX5 gain- and loss-of-function study. The molecular mechanisms of SOX5-mediated MMP-9 expressions were assayed by luciferase reporter gene and chromatin immunoprecipitation (ChIP) studies. The in vivo effect of SOX5 on FLS migration and invasion was examined using collagen-induced arthritis (CIA) in DBA/1J mice. Results: Knockdown SOX5 decreased lamellipodium formation, migration, and invasion of RA-FLS. The expression of MMP-9 was the only gene tested to be concomitantly affected by silencing or overexpressing SOX5. ChIP assay revealed that SOX5 was bound to the MMP-9 promoter in RA-FLS. The overexpression of SOX5 markedly enhanced the MMP-9 promoter activity, and specific deletion of a putative SOX5-binding site in MMP-9 promoter diminished this promoter-driven transcription in FLS. Locally knocked down SOX5 inhibited MMP-9 expression in the joint tissue and reduced pannus migration and invasion into the cartilage in CIA mice. Conclusion: SOX5 plays a novel role in mediating migration and invasion of FLS in part by regulating MMP-9 expression in RA.

Correction to: Adiponectin aggravates bone erosion by promoting osteopontin production in synovial tissue of rheumatoid arthritis.

Unfortunately, after publication of this article [1], it was noticed that the panel for Fig. 4b was inadvertently obscured during the production process. The full, correct Fig. 4 can be seen below and the original article has been corrected to reflect this.

Adiponectin aggravates bone erosion by promoting osteopontin production in synovial tissue of rheumatoid arthritis.

BACKGROUND: We have previously reported that adiponectin (AD), an adipokine that is secreted by adipocytes, correlates well with progressive bone erosion in rheumatoid arthritis (RA). The exact mechanism of AD in promoting joint destruction remains unclear. Osteopontin (OPN) is required for osteoclast recruitment. We hypothesized that AD exacerbates bone erosion by inducing OPN expression in synovial tissue. This study aimed to evaluate a novel role for AD in RA. METHODS: The serum levels of AD and OPN were determined in 38 patients with RA, 40 patients with osteoarthritis (OA), and 20 healthy controls using enzyme-linked immunosorbent assay (ELISA). AD and OPN production were measured by double immunofluorescence in RA and OA synovial tissue. Quantitative real-time PCR and immunofluorescence were used to evaluate the mRNA and protein expression levels of OPN in RA synovial fibroblasts (RASFs) and OA synovial fibroblasts after pre-incubation with AD, respectively. Migration of the RAW264.7 osteoclast precursor cell line was assessed using the Transwell migration assay and co-culture system. Bone destruction and osteoclastogenesis were assessed by immunohistochemical staining, microcomputed tomography and tartrate-resistant acid phosphatase (TRAP) staining in AD-treated collagen-induced arthritis (CIA) mice with or without OPN silencing. The expression levels of OPN and integrin αvß3 in the ankle joint tissues of the mice were examined by double immunofluorescence. RESULTS: Our results indicated that the AD and OPN expression levels increased noticeably and were associated with each other in the RA serum. The AD distribution was coincident with that of OPN in the RA synovial tissue. AD stimulation of RASFs increased OPN production in a dose-dependent manner. AD-treated RASFs promoted RAW264.7 cell migration, and the effect was blocked with a specific antibody against OPN. Silencing of OPN using lentiviral-OPN short hairpin RNA reduced the number of TRAP-positive osteoclasts and the extent of bone erosion in the AD-treated CIA mice. When bound to integrin αvß3, OPN functions as a mediator of AD and osteoclasts. CONCLUSIONS: Our study provides new evidence of AD involvement in bone erosion. AD induces the expression of OPN, which recruits osteoclasts and initiates bone erosion. These data highlight AD as a novel target for RA treatment.