Early anti-inflammatory intervention ameliorates axial disease in the proteoglycan-induced spondylitis mouse model of ankylosing spondylitis

Advances in experimental models of rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic systemic autoimmune disease characterized by persistent articular inflammation and joint damage. RA was first described over 200 years ago; however, its etiology and pathophysiology remain insufficiently understood. The current treatment of RA is mainly empirical or based on the current understanding of etiology with limited efficacy and/or substantial side effects. Thus, the development of safer and more potent therapeutics, validated and optimized in experimental models, is urgently required. To improve the transition from bench to bedside, researchers must carefully select the appropriate experimental models as well as draw the right conclusions. Here, we summarize the establishment, pathological features, potential mechanisms, advantages, and limitations of the currently available RA models. The aim of the review is to help researchers better understand available RA models; discuss future trends in RA model development, which can help highlight new translational and human-based avenues in RA research.

Facet Joint Involvement in Early MRI Positive Axial Spondyloarthritis

Background The disease course of non-radiographic axial spondyloarthritis (nr-axSpA), usually detected by magnetic resonance imaging (MRI), is often unclear at the time of diagnosis. We investigated which MRI findings in the sacroiliac joints (SIJs) and lumbar spine including the facet joints can be observed over a two-year period in patients with newly diagnosed active inflammatory lesions in the SIJs fufilling the Assessment of SpondyloArthritis International Society criteria (ASAS) for Axial Spondyloarthritis (axSpA).

Methods Patients (n=56, age<45 years, 30 female and 26 male, symptom duration 3–30 months) consecutively diagnosed with unilateral or bilateral sacroiliitis through MRI during an 18-month period and meeting the ASAS criteria for axial SpA were followed up for two years. Clinical examination, laboratory tests and an MRI of the sacroiliac joints (SIJs), lumbar spine and facet joints were performed at diagnosis (t0), after one year (t1) and after two years (t2).

Results At t0, 31 patients (55%) with a bone marrow edema (BME) in the SIJs already had detectable changes in the facet joints, including signs of inflammation or degenerative changes. At t2, patients with facet joint involvement in t0 not only had more significant changes in the SIJs but also significantly more changes in the vertebral bodies, including BME, fat lesions and vertebral body erosions than patients without changes in the facet joints at t0. All vertebral changes described might be potential indicators of progression to radiographic axSpA (r-axSpA). These MRI findings are seen more frequently over a short period of time than previously thought.

Conclusions MRI progression in the SIJs over a two-year period is associated with increasing damage to the facet joints and vertebral bodies. Involvement of the facet joints in the early stages of the disease may indicate increasing changes in the vertebral bodies and thus a less favourable course of axSpA.

T cell Repertoire Profiling and the Mechanism by which HLA-B27 Causes Ankylosing Spondylitis

Purpose of Review

Ankylosing spondylitis (AS) is strongly associated with the HLA-B27 gene. The canonical function of HLA-B27 is to present antigenic peptides to CD8 lymphocytes, leading to adaptive immune responses. The ‘arthritogenic peptide’ theory as to the mechanism by which HLA-B27 induces ankylosing spondylitis proposes that HLA-B27 presents peptides derived from exogenous sources such as bacteria to CD8 lymphocytes, which subsequently cross-react with antigens at the site of inflammation of the disease, causing inflammation. This review describes findings of studies in AS involving profiling of T cell expansions and discusses future research opportunities based on these findings.

Recent Findings

Consistent with this theory, there is an expanding body of data showing that expansion of a restricted pool of CD8 lymphocytes is found in most AS patients yet only in a small proportion of healthy HLA-B27 carriers.

Summary

These exciting findings strongly support the theory that AS is driven by presentation of antigenic peptides to the adaptive immune system by HLA-B27. They point to new potential approaches to identify the exogenous and endogenous antigens involved and to potential therapies for the disease.

Glucocorticoids in spondyloarthritis-systematic review and real-world analysis

OBJECTIVE

The objective of this study was to identify and summarize the efficacy and safety of systemic glucocorticoids (GCs) and local injections of GC in SpA.

METHODS

PubMed (Medline) and EMBASE were searched with pre-defined keywords for relevant articles in English reporting randomized controlled trials (RCTs), non-randomized interventional studies and non-randomized observational studies of the efficacy of GC in SpA, with five or more patients, for inclusion in a systematic literature review. Local injections of GC included IA and entheseal injections, but excluded SI joint injections.

RESULTS

Out of 9657 records identified, there were 14 studies on the use of systemic GCs in SpA (364 patients), including two RCTs of oral prednisolone. On pooling data from two placebo-controlled RCTs (≤24 weeks), BASDAI 50 was 4.2 times more likely (95% CI: 1.5, 11.5) and Ankylosing Spondylitis Assessment Group (ASAS) 20 was twice more likely (95% CI: 1.1, 3.64) to occur in patients on high-dose oral prednisolone (± taper). Pulsed GCs led to dramatic improvements that lasted a few weeks to a few months. There were no deaths or major adverse events. There were 10 studies (560 patients) on local GCs in SpA. IA injection was effective in achieving a sustained response in 51.5-90% of joints at 6 months. Entheseal injections led to reduced pain and improved US parameters.

CONCLUSION

There were limited studies on either systemic or local injections of GCs in SpA. However, there was good evidence of efficacy with the use of high-dose systemic GCs in the short term (≤6 months) in SpA. Both IA and entheseal injections seemed safe and effective.

Proper animal experimental designs for preclinical research of biomaterials for intervertebral disc regeneration

Low back pain is a vital musculoskeletal disease that impairs life quality, leads to disability and imposes heavy economic burden on the society, while it is greatly attributed to intervertebral disc degeneration (IDD). However, the existing treatments, such as medicines, chiropractic adjustments and surgery, cannot achieve ideal disc regeneration. Therefore, advanced bioactive therapies are implemented, including stem cells delivery, bioreagents administration, and implantation of biomaterials etc. Among these researches, few reported unsatisfying regenerative outcomes. However, these advanced therapies have barely achieved successful clinical translation. The main reason for the inconsistency between satisfying preclinical results and poor clinical translation may largely rely on the animal models that cannot actually simulate the human disc degeneration. The inappropriate animal model also leads to difficulties in comparing the efficacies among biomaterials in different reaches. Therefore, animal models that better simulate the clinical charateristics of human IDD should be acknowledged. In addition, in vivo regenerative outcomes should be carefully evaluated to obtain robust results. Nevertheless, many researches neglect certain critical characteristics, such as adhesive properties for biomaterials blocking annulus fibrosus defects and hyperalgesia that is closely related to the clinical manifestations, e.g., low back pain. Herein, in this review, we summarized the animal models established for IDD, and highlighted the proper models and parameters that may result in acknowledged IDD models. Then, we discussed the existing biomaterials for disc regeneration and the characteristics that should be considered for regenerating different parts of discs. Finally, well-established assays and parameters for in vivo disc regeneration are explored.

Aberrant upregulation of CaSR promotes pathological new bone formation in ankylosing spondylitis

Pathological new bone formation is a typical pathological feature in ankylosing spondylitis (AS), and the underlying molecular mechanism remains elusive. Previous studies have shown that the calcium‐sensing receptor (CaSR) is critical for osteogenic differentiation while also being highly involved in many inflammatory diseases. However, whether it plays a role in pathological new bone formation of AS has not been reported. Here, we report the first piece of evidence that expression of CaSR is aberrantly upregulated in entheseal tissues collected from AS patients and animal models with different hypothetical types of pathogenesis. Systemic inhibition of CaSR reduced the incidence of pathological new bone formation and the severity of the ankylosing phenotype in animal models. Activation of PLCγ signalling by CaSR promoted bone formation both in vitro and in vivo. In addition, various inflammatory cytokines induced upregulation of CaSR through NF‐κB/p65 and JAK/Stat3 pathways in osteoblasts. These novel findings suggest that inflammation‐induced aberrant upregulation of CaSR and activation of CaSR‐PLCγ signalling in osteoblasts act as mediators of inflammation, affecting pathological new bone formation in AS.

Notoginsenoside R1 suppresses miR-301a via NF-κB pathway in lipopolysaccharide-treated ATDC5 cells

BACKGROUND

Notoginsenoside R1 (NG-R1) exhibits a pharmacological activity against excessive inflammation. Here, we aimed to ascertain the anti-inflammatory role of NG-R1 in ankylosing spondylitis (AS) as well as the possible mechanism which is still under to be elucidated.

METHODS

In this study, lipopolysaccharide (LPS) was applied to evoke extreme inflammation in ATDC5 cells. To investigate the anti-inflammatory property of NG-R1, ATDC5 cells were exposed to NG-R1 prior to LPS stimulation. microRNA-301a (miR-301a)-overexpressed ATDC5 cells were established which confirmed by qRT-PCR. Then, inflammatory lesions were indicated by cell viability, apoptosis and inflammatory factors, including interleukin-1 beta (IL-1β), IL-6 and tumor necrosis factor-alpha (TNF-α). Nuclear factor-kappa B (NF-κB) pathway was determined by Western blotting assay.

RESULTS

We found NG-R1 dramatically dampened the decrease of cell viability, facilitation of apoptosis and abundance of inflammatory factors induced by LPS. Additionally, NG-R1 pre-incubation impeded LPS-induced accumulation of miR-301a. However, the protective capacity of NG-R1 was impaired by miR-301a overexpression. Of note, LPS-caused phosphorylation of p65 and inhibitor of nuclear factor kappa-B alpha (IκBα) was repressed by NG-R1, while further enhanced in miR-301-transfected ATDC5 cells.

CONCLUSION

NG-R1 relived LPS-elicited inflammatory damages via blocking NF-κB in a miR-301a-silenced manner.

HIF1α inhibition facilitates Leflunomide-AHR-CRP signaling to attenuate bone erosion in CRP-aberrant rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic inflammatory disorder characterized by progressive bone erosion. Leflunomide is originally developed to suppress inflammation via its metabolite A77 1726 to attenuate bone erosion. However, distinctive responsiveness to Leflunomide is observed among RA individuals. Here we show that Leflunomide exerts immunosuppression but limited efficacy in RA individuals distinguished by higher serum C-reactive protein (CRP^Higher, CRP^H), whereas the others with satisfactory responsiveness to Leflunomide show lower CRP (CRP^Lower, CRP^L). CRP inhibition decreases bone erosion in arthritic rats. Besides the immunomodulation via A77 1726, Leflunomide itself induces AHR-ARNT interaction to inhibit hepatic CRP production and attenuate bone erosion in CRP^L arthritic rats. Nevertheless, high CRP in CRP^H rats upregulates HIF1α, which competes with AHR for ARNT association and interferes Leflunomide-AHR-CRP signaling. Hepatocyte-specific HIF1α deletion or a HIF1α inhibitor Acriflavine re-activates Leflunomide-AHR-CRP signaling to inhibit bone erosion. This study presents a precision medicine-based therapeutic strategy for RA.

Leflunomide is used for the treatment of rheumatoid arthritis. Here, the authors show that effectiveness is limited in patients with higher levels of serum c-reactive protein (CRP). Using animal models, they show that higher CRP induces HIF1a expression, which in turn interferes with Leflunomide signalling, and that effectiveness of the drug is restored when HIF1a is pharmacologically inhibited.

Anti-TNF-α therapy alters the gut microbiota in proteoglycan-induced ankylosing spondylitis in mice

Ankylosing spondylitis is a chronic, progressive disease, and its treatment is relevant to the gut microbiota. Anti-tumor necrosis factor-alpha (anti-TNF-α) therapy alters the gut microbiota in many diseases, including inflammatory bowel disease. However, little is known about the effect of TNF-α blocker treatment on the gut microbiota in ankylosing spondylitis. Herein, the effect of a TNF-α blocker on the gut microbiota in proteoglycan-induced arthritis was investigated. Proteoglycan-induced mice were treated with an rhTNFR:Fc solution of etanercept (5 µg/g) for 4 weeks. rhTNFR:Fc treatment attenuated the arthritis incidence and severity of arthritis in the proteoglycan-induced mice and decreased inflammation in the ankle joints and ameliorated ileal tissue destruction. Moreover, high gut permeability occurred, and zonula occludens-1 and occludin protein levels were reduced in proteoglycan-induced mice. These levels were significantly restored by the administration of rhTNFR:Fc. The serum TNF-α and IL-17 levels were also decreased. In addition, flora analysis via 16S rDNA high-throughput sequencing revealed that rhTNFR:Fc treatment restored the gut microbiota composition to a composition similar to that in control mice. In conclusion, anti-TNF-α therapy attenuated proteoglycan-induced arthritis progression and modulated the gut microbiota and intestinal barrier function. These results provide new insights for anti-TNF-α therapy strategies via regulating the gut microbiota in ankylosing spondylitis.

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

OBJECTIVE

To investigate the molecular mechanism underlying inflammation-related ectopic new bone formation in ankylosing spondylitis (AS).

METHODS

Spinal tissues and sera were collected from patients with AS and healthy volunteers and examined for the expression of Wnt proteins. An in vitro cell culture system mimicking the local inflammatory microenvironment of bone-forming sites was established to study the relationship between inflammation and Wnt expression, the regulatory mechanism of inflammation-induced Wnt expression, and the role of Wnt signaling in new bone formation. Modified collagen-induced arthritis (CIA) and proteoglycan-induced spondylitis (PGIS) animal models were used to confirm the key findings in vivo.

RESULTS

The levels of osteoinductive Wnt proteins were increased in sera and spinal ligament tissues from patients with AS. Constitutive low-intensity tumor necrosis factor (TNF) stimulation, but not short-term or high-intensity TNF stimulation, induced persistent expression of osteoinductive Wnt proteins and subsequent bone formation through NF-κB (p65) and JNK/activator protein 1 (c-Jun) signaling pathways. Furthermore, inhibition of either the Wnt/β-catenin or Wnt/protein kinase Cδ (PKCδ) pathway significantly suppressed new bone formation. The increased expression of Wnt proteins was confirmed in both the modified CIA and PGIS models. A kyphotic and ankylosing phenotype of the spine was seen during long-term observation in the modified CIA model. Inhibition of either the Wnt/β-catenin or Wnt/PKCδ signaling pathway significantly reduced the incidence and severity of this phenotype.

CONCLUSION

Inflammation intensity-dependent expression of osteoinductive Wnt proteins is a key link between inflammation and ectopic new bone formation in AS. Activation of both the canonical Wnt/β-catenin and noncanonical Wnt/PKCδ pathways is required for inflammation-induced new bone formation.