Inflammation Intensity-Dependent Expression of Osteoinductive Wnt Proteins Is Critical for Ectopic New Bone Formation in Ankylosing Spondylitis

LncRNA HOTTIP enhances human osteogenic BMSCs differentiation via interaction with WDR5 and activation of Wnt/β-catenin signalling pathway

To uncover the underlying molecular mechanism of long non-coding RNA in the osteogenic differentiation process of bone marrow mesenchymal stem cells (BMSCs), HOXA transcript at the distal tip (HOTTIP) was selected by using a lncRNA microarray assay. Results showed that HOTTIP was significantly upregulated during osteogenic differentiation of human BMSCs. Downregulation of HOTTIP by shRNA inhibited the osteogenic differentiation of BMSCs. Overexpression of HOTTIP by lentiviral vector promoted human BMSCs osteogenic differentiation by increasing the transcription of β-catenin. RIP assay and RNA pulldown assay confirmed the interaction between HOTTIP and WDR5, a transcription factor binding to the promoter of β-catenin. The interaction promoted the translocation of WDR5 into the nucleus and increased the transcription of β-catenin. Implanted HOTTIP-overexpressing BMSCs increased ectopic bone formation in nude mice. HOTTIP is a conservative long noncoding RNA that is essential for osteogenic differentiation of BMSC. HOTTIP enhances osteogenic differentiation via interaction with WDR5 and up-regulation of β-catenin gene expression, therefore activating Wnt/β-catenin signalling pathway.

DKK1 Induced by 1,25D3 Is Required for the Mineralization of Osteoblasts

1α,25-dihydroxyvitamin D3 (1,25D3), the most popular drug for osteoporosis treatment, drives osteoblast differentiation and bone mineralization. Wnt/β-catenin signaling is involved in commitment and differentiation of osteoblasts, but the role of the Dickkopf-related protein 1 (DKK1), a Wnt antagonist, in osteoblasts remains unknown. Here, we demonstrate the molecular mechanism of DKK1 induction by 1,25D3 and its physiological role during osteoblast differentiation. 1,25D3 markedly promoted the expression of both CCAAT/enhancer binding protein beta (C/EBPβ) and DKK1 at day 7 during osteoblast differentiation. Interestingly, mRNA and protein levels of C/EBPβ and DKK1 in osteoblasts were elevated by 1,25D3. We also found that C/EBPβ, in response to 1,25D3, directly binds to the human DKK1 promoter. Knockdown of C/EBPβ downregulated the expression of DKK1 in osteoblasts, which was partially reversed by 1,25D3. In contrast, overexpression of C/EBPβ upregulated DKK1 expression in osteoblasts, which was enhanced by 1,25D3. Furthermore, 1,25D3 treatment in osteoblasts stimulated secretion of DKK1 protein within the endoplasmic reticulum to extracellular. Intriguingly, blocking DKK1 attenuated calcified nodule formation in mineralized osteoblasts, but not ALP activity or collagen synthesis. Taken together, these observations suggest that 1,25D3 promotes the mineralization of osteoblasts through activation of DKK1 followed by an increase of C/EBPβ.

Gene-gene interaction and association of Wnt/Β-catenin signalling pathway gene polymorphisms with ankylosing spondylitis susceptibility in the Chinese Han population

Objectives: To explore the genetic interaction between Wnt/β-catenin signalling pathway genes and ankylosing spondylitis (AS) in the Chinese population.Methods: Six single-nucleotide polymorphisms (SNPs) in DKK1, LRP5, LRP6, and SOST genes were genotyped in 673 AS patients and 687 healthy controls by using SNPs can Technic. Single marker genetic association analysis was performed. Haplotypes were constructed after linkage disequilibrium analysis; additive, multiplicative, and higher-order interactions were analysed.Results: The DKK1 gene rs1569198 polymorphism was significantly associated with AS susceptibility in females (χ² = 4.55, p = .03), but the association disappeared after Bonferroni correction. Moreover, a haplotype (T-G) in the DKK1 gene showed a protective role in AS susceptibility in females (p = .04). Significant additive interactions were observed between DKK1: rs1896368 and LRP5: rs3736228, relative excess risk due to interaction (RERI) = 0.40, 95% CI = 0.08 - 0.71; attributable proportion due to interaction (AP) = 51%, 95% CI = 0.07 - 0.94, DKK1: rs1569198 and LRP5: rs3736228 (RERI = 0.49, 95% CI = 0.12 - 0.86; AP = 49%, 95% CI = 0.17 - 0.82), LRP5: rs3736228 and SOST: rs4792909 (RERI = 0.33, 95% CI = 0.002 - 0.65; AP = 41%, 95% CI = 0.01 - 0.81) in the dominant model.Conclusions: Our research implies a potential gene-gene interaction, thus revealing the importance of the Wnt/β-catenin signalling pathway for understanding the genetic architecture of AS.

Bilobalide alleviates IL-17-induced inflammatory injury in ATDC5 cells by downregulation of microRNA-125a

Ankylosing spondylitis (AS) is a high disability and greatly destructive disease. In this study, we preliminarily studied the function and mechanism of bilobalide (BIL) on interleukin (IL)-17-induced inflammatory injury in ATDC5 cells. CCK-8 and migration assays were used to detect the functions of IL-7, BIL, and microRNA (miR)-125a on cell viability and migration. The miR-125a level was changed by transfection, and tested by real-time quantitative polymerase chain reaction. Additionally, Western blot tested the levels of inflammatory factors (IL-6 and tumor necrosis factor-α), matrix metalloproteinases (MMPs), and pathway-related proteins. Moreover, the enzyme-linked immunosorbent assay also was used to detect inflammatory factor levels. IL-7 was used to construct an inflammatory injury model in ATDC5 cells. Based on this, BIL inhibited IL-17-induced cell viability, migration, and expressions of inflammatory factors and MMPs. Furthermore, we found BIL negatively regulated miR-125a, and the miR-125a mimic could partly reverse the effects of BIL on IL-17-injury. Finally, we showed that BIL inhibited the c-Jun N-terminal kinase (JNK) and nuclear factor kappa B (NF-κB) pathways, and the miR-125a mimic had the opposite effect. BIL inhibited IL-17-induced inflammatory injury in ATDC5 cells by downregulation of miR-125a via JNK and NF-κB signaling pathways.

Biomechanical Factors in Psoriatic Disease: Defective Repair Exertion as a Potential Cause. Hypothesis Presentation and Literature Review

Joining main clinical manifestations of psoriatic skin disorder are inflammatory arthritis and nail lesions. Repetitive microdamage has been postulated as a main triggering factor in lesions of psoriatic arthritis. This concept of psoriatic disease might also be admissible for triggering nail lesions because the nail is a frequently traumatized structure. Here, we aimed to describe the conjectural injury mechanisms of nail complex with regard to acting biomechanical factors. Tissue repair response to physical microdamage may be altered in psoriatic disease. It is plausible to consider that a defective repair process in the dysregulated prepsoriatic tissue may lead to innate immune activation and further development of autoinflammatory lesions, although excessive inflammation is known to impair wound healing. Recently published data have revealed the importance of mechanosensitive Wingless-type (Wnt) signaling in the pathophysiology of psoriasis and ankylosing spondylitis. The Wnt signaling system is involved in morphogenesis, repair, and regeneration as a biologic process main regulator. Wnt5a seems to be a dominating mediator in both psoriatic plaques and during the spondylitis process that might also be a linking molecule of psoriatic response to mechanical stress. Future studies should focus on complex responsive interactions of tissue repair regulators regarded in psoriatic disease.

MiR-495 targeting dvl-2 represses the inflammatory response of ankylosing spondylitis

Ankylosing spondylitis (AS) is a type of rheumatic inflammatory disease. miRNAs participate in the process of regulating inflammatory response and bone differentiation. Herein, we aimed to test the effect of miR-495 on AS. The serum and tissues were obtained from traumatic fracture (health) and AS patients. The human fibroblast-like synovial (HFLS) cells were extracted from AS tissues. The contents of inflammatory factors and dishevelled 2 (DVL-2) were examined using enzyme-linked immunosorbent assay (ELISA). The ossification factors were detected by immunohistochemistry assay. Osteoclast was assessed by tartaric acid acid phosphatase (TRAP) assay. The cell viability and luciferase activity were measured using cell counting kit-8 (CCK-8) and dual-luciferase reporter system. The levels of factors were evaluated using quantitative real-time PCR (qRT-PCR) and western blotting. DVL-2 was a target gene for miR-495, according to the MicroRNA.org website and luciferase activity assay. The expressions of miR-495 and DVL-2 were negative corrected in AS. miR-495 and si-DVL-2 did not affect the cell viability. miR-495 and si-DVL-2 obviously inhibited inflammatory response by down-regulating tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β) and IL-6 levels, and facilitated bone differentiation by up-regulating osteoprotegerin (OPG) and receptor activator for nuclear factor-κB ligand (RANKL) levels in HFLS cells. Besides, miR-495 and si-DVL-2 increased the expression of wnt3a, runt-related transcription factor 2 (RUNX-2) and β-catenin and reduced the phosphorylation of β-catenin. Collectively, miR-495 depressed inflammatory response and promoted bone differentiation of HFLS cells, and this was accompanied by mediating wnt/β-catenin/Runx-2 pathway by targeting DVL-2.

Wnt4 signaling mediates protective effects of melatonin on new bone formation in an inflammatory environment

Growing evidence shows that the inhibitory effect of inflammatory cytokines on new bone formation by osteogenic precursor cells is a critical cause of net bone-density reduction. Melatonin has been proven to be a potential therapeutic candidate for osteoporosis. However, whether it is capable of antagonizing the suppressing effect of inflammatory cytokines on osteogenic precursor cells is so far elusive. In this study, using the cell culture system of human bone marrow stromal cells and MC3T3-E1 preosteoblasts, we recorded the following vital observations that provided insights of melatonin-induced bone formation: 1) melatonin induced bone formation in both normal and inflammatory conditions; 2) Wnt4 was essential for melatonin-induced bone formation in inflammatory stimulation; 3) melatonin- and Wnt4-induced bone formation occurred via activation of β-catenin and p38-JNK MAPK pathways by interaction with a distinct frizzled LDL receptor-related protein complex; 4) melatonin suppressed the inhibitory effect of NF-κB on osteogenesis in a Wnt4-dependent manner; and 5) melatonin induced Wnt4 expression through the ERK1/2-Pax2-Egr1 pathway. In summary, we showed a novel mechanism of melatonin-induced bone formation in an inflammatory environment. Melatonin-induced Wnt4 expression is essential for its osteoinductive effect and the inhibitory effect of NF-κB on bone formation. Our novel findings may provide useful information for its potential translational application.-Li, X., Li, Z., Wang, J., Li, Z., Cui, H., Dai, G., Chen, S., Zhang, M., Zheng, Z., Zhan, Z., Liu, H. Wnt4 signaling mediates protective effects of melatonin on new bone formation in an inflammatory environment.

Targeting inflammatory pathways in axial spondyloarthritis

The triggers and pathogenesis of axial spondyloarthritis (axSpA) are not yet completely understood. However, therapeutic agents targeting tumor necrosis factor-α and interleukin-17 inflammatory pathways have proven successful in suppressing many of the clinical symptoms and signs of axSpA, giving us an indication of which pathways are responsible for initiating and maintaining the inflammation. The mechanisms that eventuate in syndesmophytes and ankyloses are less clear. This review addresses these two critical pathways of inflammation, discussing their nature and these factors that may activate or enhance the pathways in patients with axSpA. In addition, genetic and other markers important to the inflammatory pathways implicated in axSpA are explored, and prognostic biomarkers are discussed. Treatment options available for the management of axSpA and their associated targets are highlighted.