Role of Semaphorins in Immunopathologies and Rheumatic Diseases

Downregulation of semaphorin 4A in keratinocytes reflects the features of non-lesional psoriasis

Psoriasis is a multifactorial disorder mediated by IL-17-producing T cells, involving immune cells and skin-constituting cells. Semaphorin 4A (Sema4A), an immune semaphorin, is known to take part in T helper type 1/17 differentiation and activation. However, Sema4A is also crucial for maintaining peripheral tissue homeostasis and its involvement in skin remains unknown. Here, we revealed that while Sema4A expression was pronounced in psoriatic blood lymphocytes and monocytes, it was downregulated in the keratinocytes of both psoriatic lesions and non-lesions compared to controls. Imiquimod application induced more severe dermatitis in Sema4A knockout (KO) mice compared to wild-type (WT) mice. The naïve skin of Sema4A KO mice showed increased T cell infiltration and IL-17A expression along with thicker epidermis and distinct cytokeratin expression compared to WT mice, which are hallmarks of psoriatic non-lesions. Analysis of bone marrow chimeric mice suggested that Sema4A expression in keratinocytes plays a regulatory role in imiquimod-induced dermatitis. The epidermis of psoriatic non-lesion and Sema4A KO mice demonstrated mTOR complex 1 upregulation, and the application of mTOR inhibitors reversed the skewed expression of cytokeratins in Sema4A KO mice. Conclusively, Sema4A-mediated signaling cascades can be triggers for psoriasis and targets in the treatment and prevention of psoriasis.

Conventional DMARDs therapy decreases disease activity and inflammation in newly diagnosed patients with rheumatoid arthritis by increasing FoxP3, Sema-3A, and Nrp-1 gene expression

BACKGROUND

Semaphorins are axonal guidance molecules involved in neural development and contribute to the regulation of various phases of the immune response. This study aimed to investigate the plasma levels of the pro-inflammatory cytokine interleukin-6 (IL-6) and the regulatory T (Treg) cell-related cytokine interleukin-10 (IL-10), as well as the gene expression levels of forkhead box P3 (FoxP3), Semaphorin-3A (Sema-3A), Neuropilin-1 (Nrp-1), Semaphorin-4A (Sema-4A), and Plexin-D1 (Plxn-D1), in the peripheral blood of newly diagnosed rheumatoid arthritis (RA) patients treated with conventional disease-modifying antirheumatic drugs (DMARDs) for 6 months compared with healthy controls.

METHODS

Peripheral blood samples were obtained from 40 newly diagnosed RA patients (before and after treatment) and 40 age- and sex-matched healthy subjects. The plasma concentrations of IL-6 and IL-10 were quantified via enzyme-linked immunosorbent assay (ELISA), and the mRNA expression levels of FoxP3, Sema-3A, Nrp-1, Sema-4A, and Plxn-D1 were assessed via quantitative real-time PCR.

RESULTS

Compared with those in the controls, the plasma IL-6 levels in the RA patients (both pre- and post-treatment) were significantly greater (P < 0.001). Compared with the pre-treatment levels, the plasma IL-6 levels decreased significantly after DMARD therapy (P < 0.05). Moreover, plasma IL-10 levels were significantly greater in post-treatment RA patients than in controls (P < 0.05). The gene expression of FoxP3, Sema-3A, and Nrp-1 was significantly lower in pre-treated RA patients than in controls (P < 0.001). Compared with that in pre-treatment RA patients, the gene expression of FoxP3, Sema-3A, and Nrp-1 in DMARDs-treated RA patients was strongly increased (P < 0.05, P < 0.01, and P < 0.01, respectively). There was a positive correlation between Sema-3A gene expression and the gene expression of FoxP3 (r = 0.292, P < 0.01) and Nrp-1 (r = 0.569, P < 0.0001).

CONCLUSION

Conventional DMARDs therapy effectively reduces disease activity and inflammation in newly diagnosed RA patients by increasing FoxP3, Sema-3A, and Nrp-1 gene expression.

Semaphorin 5A promotes Th17 differentiation via PI3K-Akt-mTOR in systemic lupus erythematosus

BACKGROUND

Previously, we reported that serum Semaphorin 5 A (Sema5A) levels were increased in systemic lupus erythematosus (SLE) patients compared with healthy controls (HC), and elevated Sema5A correlated with disease activity and lupus nephritis in SLE patients. In this study, we aimed to further understand the role of Sema5A in promoting Th17 cells differentiation in SLE.

METHODS

Sema5A, interferon gamma (IFN-γ), interleukin 4 (IL-4), interleukin 17 A (IL-17 A) and interleukin 10 (IL-10) were measured by Enzyme Linked Immunosorbent Assay (ELISA). RNA and protein were isolated from peripheral blood mononuclear cells (PBMCs) in SLE patients and HC. Expression of PlexinA1 and PlexinB3 were measured by quantitative RT-PCR (qRT-PCR) and Western Blot. Th cell subsets were detected by flow cytometry. Treatment with recombinant human Sema5A (rhSema5A) and small interfering RNA (siRNA) were employed to examine the in vitro effect of Sema5A in CD4+T cell differentiation in SLE patients.

RESULTS

IL-17 A elevated in SLE patients and positively correlated with Sema5A. PlexinA1 was upregulated and mainly expressed in CD4+ T cells of SLE; Sema5A treatment induced the differentiation of Th17 cells, while did not affect the Th1 and Th2 skewing. These effects were associated with an upregulation of the transcription factor RORγt by Th17 cells, but not T-bet or GATA3 in Th1 and Th2 cells, respectively. Knock down PlexinA1 regulates IL-17 A production by CD4+T cells. Functional assays showed that Sema5A-PlexinA1 axis promoted Th17 cells differentiation via PI3K/Akt/mTOR signaling.

CONCLUSIONS

These findings demonstrated that Sema5A-PlexinA1 axis acts as a key mediator on Th17 differentiation, suggesting that Sema5A might be a novel therapeutic target in SLE.

The emerging role of the semaphorin family in cartilage and osteoarthritis

In the pathogenesis of osteoarthritis, various signaling pathways may influence the bone joint through a common terminal pathway, thereby contributing to the pathological remodeling of the joint. Semaphorins (SEMAs) are cell-surface proteins actively involved in and primarily responsible for regulating chondrocyte function in the pathophysiological process of osteoarthritis (OA). The significance of the SEMA family in OA is increasingly acknowledged as pivotal. This review aims to summarize the mechanisms through which different members of the SEMA family impact various structures within joints. The findings indicate that SEMA3A and SEMA4D are particularly relevant to OA, as they participate in cartilage injury, subchondral bone remodeling, or synovitis. Additionally, other elements such as SEMA4A and SEMA5A may also contribute to the onset and progression of OA by affecting different components of the bone and joint. The mentioned mechanisms demonstrate the indispensable role of SEMA family members in OA, although the detailed mechanisms still require further exploration.

The Role of Semaphorins in the Pathogenesis of Rheumatoid Arthritis

Rheumatoid arthritis (RA) is one of the most common autoimmune diseases. Inflammation of the synovial fluid propagates the pathological process of angiogenesis. Semaphorins play a crucial role in the context of endothelial cell function, and their pleiotropic nature has various effects on the further development of RA. This narrative review summarises the various roles of semaphorins in the pathology of RA and whether they could play a role in developing novel RA treatment options.

Expression of semaphorin-3A in the joint and role in osteoarthritis

Osteoarthritis (OA) is characterised by the deterioration of cartilage in the joints and pain. We hypothesise that semaphorin-3A (sema-3A), a chemorepellent for sensory nerves, plays a role in joint degradation and pain. We used the mechanical joint loading (MJL) model of OA to investigate sema-3A expression in the joint and examine its association with the development of OA and pain. We also analyse its effect on chondrocyte differentiation using the ATDC5 cell line. We demonstrate that sema-3A is present in most tissues in the healthy joint and its expression increases in highly innervated tissues, such as cruciate ligaments, synovial lining and subchondral bone, in loaded compared to nonloaded control joints. In contrast, sema-3A expression in cartilage was decreased in the severe OA induced by the application of high loads. There was a significant increase in circulating sema-3A, 6 weeks after MJL compared to the nonloaded mice. mRNA for sema-3A and its receptor Plexin A1 were upregulated in the dorsal root ganglia of mice submitted to MJL. These increases were supressed by zoledronate, an inhibitor of bone pain. Sema-3A was expressed at all stages of Chondrocyte maturation and, when added exogenously, stimulated expression of markers of chondrocyte differentiation. This indicates that sema-3A could affect joint tissues distinctively during the development of OA. In highly innervated joint tissues, sema-3A could control innervation and/or induce pain-associated neuronal changes. In cartilage, sema-3A could favour its degeneration by modifying chondrocyte differentiation.

An update of murine models and their methodologies in immune-mediated joint damage and pain research

Murine models have played an indispensable role in the understanding of rheumatic and musculoskeletal disorders (RMD), elucidating the genetic, endocrine and biomechanical pathways involved in joint pathology and associated pain. To date, the available models in RMD can be classified as induced or spontaneous, both incorporating transgenic alternatives that improve specific insights. It is worth noting that the selection of the most appropriate model together with the evaluation of their specific characteristics and technical capabilities are crucial when designing the experiments. Furthermore, it is also imperative to consistently adhere to the ethical standards concerning animal experimentation. Recognizing the inherent limitation that any model can entirely encapsulates the complexity of the pathophysiology of these conditions, the aim of this review is to provide an updated overview on the methodology of current murine models in major arthropathies and their immune-mediated pathways, addressing to basic, translational and pharmacological research in joint damage and pain.

Semaphorin3B promotes an anti-inflammatory and pro-resolving phenotype in macrophages from rheumatoid arthritis patients in a MerTK-dependent manner

Previous works from our group show that Semaphorin3B (Sema3B) is reduced in RA and plays a protective role in a mouse arthritis model. In turn, MerTK plays a protective function in murine arthritis models, is expressed by synovial tissue macrophages and is linked to remission in patients with RA. In this study, we examined the role of Sema3B in the phenotypic characteristics of RA macrophages and the implication of MerTK. Peripheral blood monocytes from RA patients were differentiated into IFN-γ (RA MØIFN-γ) or M-CSF (RA MØM-CSF) macrophages and stimulated with LPS, Sema3B or their combination. Alternatively, RA fibroblast like synoviocytes (FLS) were stimulated with RA MØIFN-γ and RA MØM-CSF supernatants. Gene expression was determined by qPCR and protein expression and activation by flow cytometry, ELISA and western blot. Sema3B down-regulated the expression of pro-inflammatory mediators, in both RA MØIFN-γ and RA MØM-CSF. We observed a similar reduction in RA FLS stimulated with the supernatant of Sema3B-treated RA MØIFN-γ and RA MØM-CSF. Sema3B also modulated cell surface markers in macrophages towards an anti-inflammatory phenotype. Besides, MerTK expression and activation was up-regulated by Sema3B, just as GAS6 expression, Resolvin D1 secretion and the phagocytic activity of macrophages. Importantly, the inhibition of MerTK and neuropilins 1 and 2 abrogated the anti-inflammatory effect of Sema3B. Our data demonstrate that Sema3B modulates the macrophage characteristics in RA, inducing a skewing towards an anti-inflammatory/pro-resolving phenotype in a MerTK-dependant manner. Therefore, here we identify a new mechanism supporting the protective role of Sema3B in RA pathogenesis.

Semaphorin 3A levels in vascular and nonvascular phenotypes in systemic sclerosis

OBJECTIVE

Semaphorin 3A (Sema3A) plays a regulatory role in immune responses. The aim of this study was to evaluate Sema3A levels in patients with systemic sclerosis (SSc), especially in major vascular involvements such as digital ulcer (DU), scleroderma renal crisis (SRC), pulmonary arterial hypertension (PAH), and to compare Sema3A level with SSc disease activity.

METHODS

In SSc patients, patients with DU, SRC, or PAH were grouped as major vascular involvements and those without as nonvascular, and Sema3A levels were compared between the groups and with a healthy control group. The Sema3A levels and acute phase reactants in SSc patients, as well as their association with the Valentini disease activity index and modified Rodnan skin score, were evaluated.

RESULTS

The Sema3A values (mean ± SD) were 57.60 ± 19.81 ng/mL in the control group (n = 31), 44.32 ± 5.87 ng/mL in patients with major vascular involvement SSc (n = 21), and 49.96 ± 14.00 ng/mL in the nonvascular SSc group (n = 35). When all SSc patients were examined as a single group, the mean Sema3A value was significantly lower than controls (P = .016). The SSc with major vascular involvement group had significantly lower Sema3A levels than SSc with nonmajor vascular involvement group (P = .04). No correlation was found between Sema3A, acute phase reactants, and disease activity scores. Also, no relationship was observed between Sema3A levels and diffuse (48.36 ± 11.47 ng/mL) or limited (47.43 ± 12.38 ng/mL) SSc types (P = .775).

CONCLUSION

Our study suggests that Sema3A may play a significant role in the pathogenesis of vasculopathy and can be used as a biomarker in SSc patients with vascular complications such as DU and PAH.

HOXA5 is a key regulator of class 3 semaphorins expression in the synovium of rheumatoid arthritis patients

OBJECTIVE

Class 3 semaphorins are reduced in the synovial tissue of RA patients and these proteins are involved in the pathogenesis of the disease. The aim of this study was to identify the transcription factors involved in the expression of class 3 semaphorins in the synovium of RA patients.

METHODS

Protein and mRNA expression in synovial tissue from RA and individuals at risk (IAR) patients, human umbilical vein endothelial cells (HUVEC) and RA fibroblast-like synoviocytes (FLS) was determined by ELISA, immunoblotting and quantitative PCR. TCF-3, EBF-1 and HOXA5 expression was knocked down using siRNA. Cell viability, migration and invasion were determined using MTT, calcein, wound closure and invasion assays, respectively.

RESULTS

mRNA expression of all class 3 semaphorins was significantly lower in the synovium of RA compared with IAR patients. In silico analysis suggested TCF-3, EBF-1 and HOXA5 as transcription factors involved in the expression of these semaphorins. TCF-3, EBF-1 and HOXA5 silencing significantly reduced the expression of several class 3 semaphorin members in FLS and HUVEC. Importantly, HOXA5 expression was significantly reduced in the synovium of RA compared with IAR patients and was negatively correlated with clinical disease parameters. Additionally, TNF-α down-regulated the HOXA5 expression in FLS and HUVEC. Finally, HOXA5 silencing enhanced the migratory and invasive capacities of FLS and the viability of HUVEC.

CONCLUSION

HOXA5 expression is reduced during the progression of RA and could be a novel therapeutic strategy for modulating the hyperplasia of the synovium, through the regulation of class 3 semaphorins expression.

Practical Significance of Biomarkers in Axial Spondyloarthritis: Updates on Diagnosis, Disease Activity, and Prognosis

Axial spondyloarthritis (axSpA) is a chronic inflammatory disease that can lead to ankylosis by secondary ossification of inflammatory lesions, with progressive disability and a significant impact on quality of life. It is also a risk factor for the occurrence of comorbidities, especially cardiovascular diseases (CVDs), mood disorders, osteoporosis, and malignancies. Early diagnosis and treatment are needed to prevent or decrease functional decline and to improve the patient's prognosis. In respect of axSpA, there is an unmet need for biomarkers that can help to diagnose the disease, define disease activity and prognosis, and establish personalized treatment approaches. The aim of this review was to summarize the available information regarding the most promising biomarkers for axSpA. We classified and identified six core categories of biomarkers: (i) systemic markers of inflammation; (ii) molecules involved in bone homeostasis; (iii) HLA-B27 and newer genetic biomarkers; (iv) antibody-based biomarkers; (v) microbiome biomarkers; and (vi) miscellaneous biomarkers. Unfortunately, despite efforts to validate new biomarkers, few of them are used in clinical practice; however, we believe that these studies provide useful data that could aid in better disease management.

Effectiveness and Safety of Iguratimod Monotherapy or Combined With Methotrexate in Treating Rheumatoid Arthritis: A Systematic Review and Meta-Analysis

Objectives: We aimed to estimate the effectiveness and safety of iguratimod (IGU) monotherapy or in combination with methotrexate (MTX) in treating rheumatoid arthritis (RA) to provide an evidence-primarily-based foundation for clinical application.

Methods: We conducted a systematic review of the meta-analysis using eight databases and two clinical trial websites searching for randomized controlled trials (RCTs) from conception to 15 March 2022, based on outcomes of patients with RA treated with IGU. The evidence quality assessment of primary outcomes was evaluated by the GRADE tool, and RevMan 5.3 and StataMP 14.0 were used to perform this research.

Results: A total of 4302 patients with RA from 38 RCTs was included in this research. Pooled results demonstrated as follows: 1) Compared with methotrexate (MTX) alone, IGU alone was superior in improving ACR20 and DAS28-ESR, while having no significant difference in ACR50 and ACR70 [ACR20: (RR 1.15, 95% CI 1.05–1.27, p = 0.004); ACR50: (RR 0.97, 95% CI 0.66–1.44, p = 0.88); ACR70: (RR 0.92, 95% CI 0.45–1.90, p = 0.83); DAS28-ESR: mean difference (MD) −0.15, 95% CI −0.27 to −0.03, p = 0.01]. 2) Compared with MTX alone, IGU + MTX was more effective in improving ACR20, ACR50, ACR70, and DAS28-ESR. [ACR20: (RR 1.24, 95% CI 1.14–1.35, p < 0.00001); ACR50: (RR 1.96, 95% CI 1.62–2.39, p <0.00001); ACR70: (RR 1.91, 95% CI 1.41–2.57, p < 0.0001)]; [DAS28-ESR: (MD) −1.43, 95% CI −1.73 to −1.12, p < 0.00001]. 3) Compared with MTX + leflunomide (LEF), ACR20, ACR50, ACR70, and DAS28-ESR of IGU + MTX had no significant difference [ACR20: (RR 1.06, 95% CI 0.94–1.19, p = 0.38); ACR50: (RR 1.10, 95% CI 0.66–1.84, p = 0.72); ACR70: (RR 1.20, 95% CI 0.45–3.20, p = 0.71); DAS28-ESR: (MD −0.02, 95% CI −0.13 to −0.10, p = 0.77)]. 4) Compared with MTX + hydroxychloroquine (HCQ), IGU + MTX was superior in improving DAS28-ESR (MD −2.16, 95% CI −2.53 to −1.79, p < 0.00001). 5) Compared with MTX + tripterygium glycosides (TGs), IGU + MTX was more effective in improving DAS28-ESR (MD −0.94, 95% CI −2.36 to 0.48, p = 0.19). 6) There were no significant differences in adverse events (AEs) between the groups of IGU vs. MTX (RR 0.96, 95% CI 0.71–1.31, p = 0.80), IGU + MTX vs. MTX (RR 1.10, 95% CI 0.90–1.35, p = 0.34), IGU + MTX vs. MTX + HCQ (RR 0.64, 95% CI 0.29–1.42, p = 0.27), and IGU + MTX vs. MTX + TGs (RR 0.75, 95% CI 0.28–2.02, p = 0.57). The incidence of AEs in the IGU + MTX group was lower than the MTX + LEF group (RR 0.83, 95% CI 0.71–0.98, p = 0.03).

Conclusion: Compared to the MTX alone subgroup, IGU alone offers clear advantages in improving ACR20 and DAS28-ESR, despite the insufficient evidence for DAS28-ESR findings. IGU + MTX shows clear benefits in improving ACR20, ACR50, ACR70, and DAS28-ESR scores compared to standard therapies. When the intervention (IGU alone or IGU + MTX) lasted for 52 weeks, it demonstrated superior efficacy in improving ACR20 of patients without prominent adverse events. Notably, IGU or IGU + MTX has apparent advantages in improving ACR20 of first-visit RA, and IGU + MTX has obvious advantages in improving DAS28-ESR of refractory RA. Furthermore, IGU + MTX does not increase the risk of leukopenia, but it can decrease the risk of liver function tests (LFTs), regardless of the age or the stage of RA.

Clinical Trial Registration:https://www.crd.york.ac.uk/PROSPERO/#recordDetails, identifier CRD42022295217

Circulating Neurovascular Guidance Molecules and Their Relationship with Peripheral Microvascular Impairment in Systemic Sclerosis

Systemic sclerosis (SSc, scleroderma) is a complex connective tissue disease whose earliest clinical manifestations are microvascular tone dysregulation and peripheral microcirculatory abnormalities. Following previous evidence of an association between circulating neurovascular guidance molecules and SSc disturbed angiogenesis, here, we measured the levels of soluble neuropilin 1 (sNRP1), semaphorin 3E (Sema3E), and Slit2 by enzyme-linked immunosorbent assay in serum samples from a large case series of 166 SSc patients vs. 110 healthy controls. We focused on their possible correlation with vascular disease clinical features and applied logistic regression analysis to determine which of them could better reflect disease activity and severity. Our results demonstrate that, in SSc: (i) sNRP1 is significantly decreased, with lower sNRP1 serum levels correlating with the severity of nailfold videocapillaroscopy (NVC) abnormalities and the presence of ischemic digital ulcers (DUs); (ii) both Sema3E and Slit2 are increased, with Sema3E better reflecting early NVC abnormalities; and (iii) higher Sema3E correlates with the absence of DUs, while augmented Slit2 associates with the presence of DUs. Receiver operator characteristics curve analysis revealed that both circulating sNRP1 and Sema3E show a moderate diagnostic accuracy. Moreover, logistic regression analysis allowed to identify sNRP1 and Sema3E as more suitable independent biomarkers reflecting the activity and severity of SSc-related peripheral microvasculopathy.

Semaphorin 3A: A potential target for prevention and treatment of nickel allergy

Metal allergy is one of the typical immune disorders encountered during the application of dental/medical materials and has a highly complex pathogenic mechanism. Semaphorin 3A (Sema3A), a member of the semaphorin family, is reported to be involved in various immune disorders. However, its role in metal allergy has not been clarified yet. Herein, we show that Sema3A expression was upregulated in nickel (Ni) allergy-induced mouse ear tissue and in NiCl₂-stimulated mouse keratinocytes. Moreover, Sema3A regulated tumor necrosis factor-alpha production and mitogen-activated protein kinase activation in keratinocytes. The specific deletion of Sema3A in keratinocytes did not affect immune cell infiltration but reduced edema and ear swelling; it also impeded Th1 responses to cause a slight alleviation in Ni allergy in mice. Our results demonstrate that Sema3A promotes the development of metal allergy and should be explored as a potential target for the prevention and treatment of metal allergy.

Semaphorin 3A is upregulated in keratinocytes upon nickel exposure, subsequently promoting Th1 cytokine responses and driving nickel allergic reactions.

Remote ischemic preconditioning causes transient cell-cycle arrest and renal protection by a NF-kB-dependent Sema5B pathway

Acute kidney injury increases morbidity and mortality, and previous studies have shown that remote ischemic preconditioning (RIPC) reduces the risk of acute kidney injury after cardiac surgery. RIPC increases urinary high mobility group box protein-1 (HMGB1) levels in patients, and this correlates with kidney protection. Here, we show that RIPC reduces renal ischemia-reperfusion injury and improves kidney function in mice. Mechanistically, RIPC increases HMGB1 levels in the plasma and urine, and HMGB1 binds to TLR4 on renal tubular epithelial cells, inducing transcriptomic modulation of renal tubular epithelial cells and providing renal protection, whereas TLR4 activation on nonrenal cells was shown to contribute to renal injury. This protection is mediated by activation of induction of AMPKα and NF-κB; this induction contributes to the upregulation of Sema5b, which triggers a transient, protective G₁ cell cycle arrest. In cardiac surgery patients at high risk for postoperative acute kidney injury, increased HMGB1 and Sema5b levels after RIPC were associated with renal protection after surgery. The results may help to develop future clinical treatment options for acute kidney injury.

Identification of mechanics-responsive osteocyte signature in osteoarthritis subchondral bone

Aims

Osteoarthritis (OA) is a common degenerative joint disease. The osteocyte transcriptome is highly relevant to osteocyte biology. This study aimed to explore the osteocyte transcriptome in subchondral bone affected by OA.

Methods

Gene expression profiles of OA subchondral bone were used to identify disease-relevant genes and signalling pathways. RNA-sequencing data of a bone loading model were used to identify the loading-responsive gene set. Weighted gene co-expression network analysis (WGCNA) was employed to develop the osteocyte mechanics-responsive gene signature.

Results

A group of 77 persistent genes that are highly relevant to extracellular matrix (ECM) biology and bone remodelling signalling were identified in OA subchondral lesions. A loading responsive gene set, including 446 principal genes, was highly enriched in OA medial tibial plateaus compared to lateral tibial plateaus. Of this gene set, a total of 223 genes were identified as the main contributors that were strongly associated with osteocyte functions and signalling pathways, such as ECM modelling, axon guidance, Hippo, Wnt, and transforming growth factor beta (TGF-β) signalling pathways. We limited the loading-responsive genes obtained via the osteocyte transcriptome signature to identify a subgroup of genes that are highly relevant to osteocytes, as the mechanics-responsive osteocyte signature in OA. Based on WGCNA, we found that this signature was highly co-expressed and identified three clusters, including early, late, and persistently responsive genes.

Conclusion

In this study, we identified the mechanics-responsive osteocyte signature in OA-lesioned subchondral bone.

Cite this article: Bone Joint Res 2022;11(6):362–370.

Semaphorin3B plays a central role in serum-induced arthritis model and is reduced in patients with rheumatoid arthritis

Objective

Semaphorin 3B (Sema3B) decreases the migratory and invasive capacities of fibroblast‐like synoviocytes (FLS) in rheumatoid arthritis (RA) and suppresses expression of matrix metalloproteinases. We undertook this study to examine the role of Sema3B in a mouse model of arthritis and its expression in RA patients.

Methods

Clinical responses, histologic features, and FLS function were examined in wild‐type (WT) and Sema3B^−/− mice in a K/BxN serum transfer model of arthritis. Protein and messenger RNA expression of Sema3B in mouse joints and murine FLS, as well as in serum and synovial tissue from patients with arthralgia and patients with RA, was determined using enzyme‐linked immunosorbent assay, immunoblotting, quantitative polymerase chain reaction, and RNA sequencing. FLS migration was determined using a wound closure assay.

Results

The clinical severity of serum‐induced arthritis was significantly higher in Sema3B^−/− mice compared to WT mice. This was associated with increased expression of inflammatory mediators and increased migratory capacity of murine FLS. Administration of recombinant mouse Sema3B reduced the clinical severity of serum‐induced arthritis and the expression of inflammatory mediators. Sema3B expression was significantly lower in the synovial tissue and serum of patients with established RA compared to patients with arthralgia. Serum Sema3B levels were elevated in patients with arthralgia that later progressed to RA, but not in those who did not develop RA; however, these levels drastically decreased 1 and 2 years after RA development.

Conclusion

Sema3B expression plays a protective role in a mouse model of arthritis. In RA patients, expression levels of Sema3B in the serum depend on the disease stage, suggesting different regulatory roles in disease onset and progression.

Soluble neuropilin-1 in gingival crevicular fluid is associated with rheumatoid arthritis: An exploratory case-control study

BACKGROUND

To explore the soluble Neuropilin-1 (sNRP-1) concentrations in gingival crevicular fluid (GCF) and the periodontal clinical status of patients with Rheumatoid Arthritis (RA).

MATERIALS AND METHODS

We conducted an exploratory study with 40 study participants, 20 with RA, and 20 healthy controls. Clinical and periodontal data were recorded, and GCF samples were obtained. sNRP-1 levels in GCF were determined by ELISA assay. Descriptive statistics, Mann-Whitney U test, Unpaired t-test, logistic regression model, and Area Under Receiver Operating Characteristic Curve (AUC-ROC) were made to explore the diagnostic performance accuracy.

RESULTS

RA patients had significantly higher levels of sNRP-1 in GCF (p ​= ​0.0447). The median levels of GCF-sNRP-1 were 208.85 ​pg/μl (IQR 131.03) in the RA group compared to 81.46 ​pg/μl (IQR 163.73) in the control group. We observed an association between the GCF-sNRP-1 concentrations and the RA diagnosis (OR:1.009; CI 1.00-1.001; p ​= ​0.047). The diagnosis of chronic periodontitis was also associated with RA (OR: 6.9; CI 1.52-31.37; p ​= ​0.012). Moreover, the AUC-ROC of GCF-sNRP-1 concentrations combined with periodontal clinical parameters such as periodontal probing depth and periodontal inflamed surface area was 0.80.

CONCLUSION

This exploratory case-control study shows that RA patients had significantly higher levels of sNRP-1 in GCF. New longitudinal studies are necessary to evaluate the role of NRP-1 in periodontal tissues and consider it an oral biomarker with clinical value in RA.

Signalling and putative therapeutic molecules on the regulation of synoviocyte signalling in rheumatoid arthritis

Rheumatoid arthritis (RA) is an autoimmune disease characterized by symmetrical and chronic polyarthritis. Fibroblast-like synoviocytes are mainly involved in joint inflammation and cartilage and bone destruction by inflammatory cytokines and matrix-degrading enzymes in RA. Approaches that induce various cellular growth alterations of synoviocytes are considered as potential strategies for treating RA. However, since synoviocytes play a critical role in RA, the mechanism and hyperplastic modulation of synoviocytes and their motility need to be addressed. In this review, we focus on the alteration of synoviocyte signalling and cell fate provided by signalling proteins, various antioxidant molecules, enzymes, compounds, clinical candidates, to understand the pathology of the synoviocytes, and finally to achieve developed therapeutic strategies of RA.

Cite this article: Bone Joint Res 2021;10(4):285–297.

Class-3 semaphorins: Potent multifunctional modulators for angiogenesis-associated diseases

Semaphorins, the neuronal guidance cues, were shown to have broad influences on pathophysiological processes such as bone remodeling, immune responses, and angiogenesis. In particular, Class-3 Semaphorins (SEMA3) is considered a vital regulator involved in angiogenesis. Scientific evidence has pointed to the role of angiogenesis in many diseases, and numerous efforts have been made to explore the possibilities of curing those diseases by targeting angiogenesis. Nevertheless, the efficacies are limited owing to the complex mechanisms of angiogenesis. Hence, investigating the mechanisms of SEMA3 in angiogenesis may contribute to novel therapeutics for diseases. Previous reviews mainly focused on the various functions of semaphorins in one particular disease, and the specific angiogenesis mechanism of SEMA3 in diverse diseases has not been well elucidated. Additionally, the role of SEMA3 in angiogenesis remains elusive, as contradicting results have been found in different disease types. Some evidence from recent studies implies that, while most SEMA3 molecules inhibit pathological angiogenesis in different diseases, occasionally SEMA3 may also promote angiogenesis. This review summarizes the specific role of SEMA3 in a variety of angiogenesis-associated diseases, and documents SEMA3 may be a promising therapeutic target for treating angiogenesis-associated diseases.

Sema4D/Plexin-B1 promotes the progression of osteosarcoma cells by activating Pyk2-PI3K-AKT pathway

OBJECTIVES

Osteosarcoma (OS) is one of the two most common malignant bone tumors among children and teens but it is still a rare disorder. Semaphorin 4D (Sema4D) has been reported to play a specific role in human cancers. The aim of this study was to explore the function of Sema4D in the tumorigenesis and development of OS.

METHODS

10 pairs of OS tissues and paracancerous normal tissues from human OS samples and OS cell lines were used. Western blot assay was performed to detect the protein expression of Sema4D, Plexin-B1, and associated proteins of Pyk2-PI3K/AKT pathway. To explore the effect of Sema4D in the progression of OS, we reduced the expression of Sema4D. The effect of Sema4D knockdown on cell proliferation was explored by CCK-8 assay and clone formation assay. The effect of Sema4D knockdown on cell migration and invasion was assessed by Transwell assay.

RESULTS

Sema4D was overexpressed in OS tissues and cell lines. Sema4D knockdown notably suppressed cell proliferation in OS cells. Cell migration and invasion were reduced by Sema4D knockdown. Sema4D/Plexin-B1 facilitated OS, progression by promoting Pyk2-PI3K/AKT pathway.

CONCLUSION

Sema4D/Plexin-B1 promoted the development of OS so Sema4D might be a potential target of treatment for patients with OS.

Semaphorins in health and disease

Cell-cell communication is pivotal to guide embryo development, as well as to maintain adult tissues homeostasis and control immune response. Among extracellular factors responsible for this function, are the Semaphorins, a broad family of around 20 different molecular cues conserved in evolution and widely expressed in all tissues. The signaling cascades initiated by semaphorins depend on a family of conserved receptors, called Plexins, and on several additional molecules found in the receptor complexes. Moreover, multiple intracellular pathways have been described to act downstream of semaphorins, highlighting significant diversity in the signaling cascades controlled by this family. Notably, semaphorin expression is altered in many human diseases, such as immunopathologies, neurodegenerative diseases and cancer. This underscores the importance of semaphorins as regulatory factors in the tissue microenvironment and has prompted growing interest for assessing their potential relevance in medicine. This review article surveys the main contexts in which semaphorins have been found to regulate developing and healthy adult tissues, and the signaling cascades implicated in these functions. Vis a vis, we will highlight the main pathological processes in which semaphorins are thought to have a role thereof.

Semaphorins in Angiogenesis and Autoimmune Diseases: Therapeutic Targets?

The axonal guidance molecules, semaphorins, have been described to function both physiologically and pathologically outside of the nervous system. In this review, we focus on the vertebrate semaphorins found in classes 3 through 7 and their roles in vascular development and autoimmune diseases. Recent studies indicate that while some of these vertebrate semaphorins promote angiogenesis, others have an angiostatic function. Since some semaphorins are also expressed by different immune cells and are known to modulate immune responses, they have been implicated in autoimmune disorders such as multiple sclerosis, rheumatoid arthritis, systemic lupus erythematosus and systemic sclerosis. We conclude this review by addressing strategies targeting semaphorins as potential therapeutic agents for angiogenesis and autoimmune diseases.