Current advances in research of semaphorin 3A:a potential target for the treatment of nospecific low back pain / 中国骨伤

Nonspecific low back pain is closely associated with afferent nerve ingrowth into degenerated IVDs and increasing the inflammatory response. Members of the class 3 semaphorins signal their response through two prominent receptors; the NRP (Neuropilin-1) and the Plexin A. Sema3A (Semaphorin3A) is primarily known for their role in modulating neuronal survival as well as neurite outgrowth and guidance via regulation of Sema3A-NRP-1-plexinA signal pathway. Also, sema3A is shown to be conductive to innervate the inner painful degenerated IVDs (Intervertebral discs). Furthermore, sema3A is thought to act as a barrier to endothelial cells survival and migration on vascular endothelial growth factor (VEGF) and inhibition of KLF5-induced (Krüppel-like factor 5) inflammatory mediators within degenerated IVDs. Therefore, Sema3A produce a new perspective of dual-action therapeutic agent for attenuating the regulator of innervation and angiogenesis into degenerated IVDs and inhibition of KLF5-induced inflammation.

Expression of Semaphorin 3A after spinal cord injury / 中国骨伤

OBJECTIVE@#To investigate expression of Semaphorin 3A in rats after spinal cord injury and explore possible mechanism of inhibiting of axonal regeneration after SCI.@*METHODS@#Forty healthy female SD rats, 8 weeks old, weighing (210.00±9.88) g, were randomly divided into control group(20 rats in group A) and model group(20 rats in group B). In control group, removal of T@*RESULTS@#After a simple spinal cord transection injury, hemorrhagic necrosis, localized edema, neurodegeneration, necrosis, and cyst formation occurred in the injured area, and glial scar formation occurred in glial cells. Semaphorin 3A expression levels in control group was low in the gray matter area. There was no expression of Semaphorin 3A in the injured area of spinal cord injury in model group 3 days after operation. On the 14th day, the expression of Semaphorin 3A in the injured area of spinal cord injury increased significantly and was at a high level. On the 28th day, the expression of Semaphorin 3A was moderate. On the 42th day, the positive expression of Semaphorin 3A returned to normal level.@*CONCLUSION@#The increased expression of Semaphorin 3A after spinal cord injury may be one of the mechanisms that inhibit axonal regeneration.

Association of Semaphorin 3A with thrombocytopenia in systemic lupus erythematosus / 北京大学学报(医学版)

OBJECTIVE@#To measure the level of serum Semaphorin 3A (Sema3A) and to analyze the relationship between serum Sema3A and systemic lupus erythematosus (SLE) with thrombocytopenia.@*METHODS@#The concentration of serum Sema3A was detected by enzyme-linked immuno sorbent assay (ELISA) in 170 SLE patients, 50 Sjögren's syndrome (SS) patients, 19 hypersplenism (HS) patients and 150 healthy controls (HC). Based on the presence of thrombocytopenia and whether the thrombocytopenia was in remission, the SLE patients were divided into three groups: SLE with thrombocytopenia (41 cases), SLE with thrombocytopenia remission (28 cases), and SLE without thrombocytopenia (101 cases). According to whether there was thrombocytopenia, the SS patients were divided into SS with thrombocytopenia (18 cases) and SS without thrombocytopenia (32 cases). The 28 SLE patients who underwent bone marrow aspiration biopsy were divided into two groups from the aspect of whether the bone marrow hyperplasia was normal (19 cases) or low (9 cases), as well as from the aspect of whether the maturity disturbance of megakaryocyte was positive (8 cases) or negative (20 cases). The serum Sema3A levels in SLE, SS, HS with HC were compared, meanwhile, the correlation between serum Sema3A level and platelet (PLT) in the patients with different diseases analyzed.@*RESULTS@#(1) Serum Sema3A levels in SLE were significantly lower than in HC [(3.84±2.76) μg/L vs. (6.96±2.62) μg/L, P < 0.001], serum Sema3A levels in SS were also obviously lower than in HC [(4.35±3.57) μg/L vs. (6.96±2.62) μg/L, P < 0.001], and in HS it was lower than HC at a certain extant [(5.67±2.26) μg/L vs. (6.96±2.62) μg/L, P=0.041]. (2) Serum Sema3A levels in SLE were slightly lower than in SS, but there was no significant difference [(3.84±2.76) μg/L vs. (4.35±3.57) μg/L, P=0.282]. However, when compared with HS, serum Sema3A levels in SLE were significantly lower [(3.84±2.76) μg/L vs. (5.67±2.26) μg/L, P=0.006]. (3) Serum Sema3A concentration in SLE with thrombocytopenia was significantly lower than in SLE with thrombocytopenia remission [(1.28±1.06) μg/L vs. (3.83±2.65) μg/L, P < 0.001], and in SLE patients without thrombocytopenia [(1.28±1.06) μg/L vs. (4.87±2.60) μg/L, P < 0.001]. There was no significant difference between SLE with thrombocytopenia remission and SLE without thrombocytopenia [(3.83±2.65) μg/L vs. (4.87±2.600 μg/L, P=0.123]. Serum Sema3A concentration in SLE with thrombocytopenia was slightly lower than in SS with thrombocytopenia, but there was no significant difference [(1.28±1.06) μg/L vs. (1.68±1.11) μg/L, P=0.189]. (4) Strong positive correlations were found between serum Sema3A and PLT in SLE (r=0.600, P < 0.001). Positive correlations were also found between serum Sema3A and PLT in SS (r=0.573, P < 0.001). However, there was no such correlation showed in HS patients (P=0.393). (5) There was no significant difference of serum Sema3A concentration in SLE whether the bone marrow hyperplasia was normal or low. And the same situation appeared in the patients whether the maturity disturbance of megakaryocyte was positive or negative (P>0.05).@*CONCLUSION@#Serum Sema3A was significantly reduced in SLE patients, and it was highly correlated with the blood damage. Similar conclusions could be drawn in patients with SS. The serum level of Sema3A was generally decreasing in desmosis which merged thrombocytopenia, and was obviously positive correlated with platelet counts.

Anti-SEMA3A Antibody: A Novel Therapeutic Agent to Suppress Glioblastoma Tumor Growth / Journal of the Korean Cancer Association, 대한암학회지

PURPOSE: Glioblastoma (GBM) is classified as one of the most aggressive and lethal brain tumor. Great strides have been made in understanding the genomic and molecular underpinnings of GBM, which translated into development of new therapeutic approaches to combat such deadly disease. However, there are only few therapeutic agents that can effectively inhibit GBM invasion in a clinical framework. In an effort to address such challenges, we have generated anti-SEMA3A monoclonal antibody as a potential therapeutic antibody against GBM progression. MATERIALS AND METHODS: We employed public glioma datasets, Repository of Molecular Brain Neoplasia Data and The Cancer Genome Atlas, to analyze SEMA3A mRNA expression in human GBM specimens. We also evaluated for protein expression level of SEMA3A via tissue microarray (TMA) analysis. Cell migration and proliferation kinetics were assessed in various GBM patient-derived cells (PDCs) and U87-MG cell-line for SEMA3A antibody efficacy. GBM patient-derived xenograft (PDX) models were generated to evaluate tumor inhibitory effect of anti-SEMA3A antibody in vivo. RESULTS: By combining bioinformatics and TMA analysis, we discovered that SEMA3A is highly expressed in human GBM specimens compared to non-neoplastic tissues. We developed three different anti-SEMA3A antibodies, in fully human IgG form, through screening phage-displayed synthetic antibody library using a classical panning method. Neutralization of SEMA3A significantly reduced migration and proliferation capabilities of PDCs and U87-MG cell line in vitro. In PDX models, treatment with anti-SEMA3A antibody exhibited notable tumor inhibitory effect through down-regulation of cellular proliferative kinetics and tumor-associated macrophages recruitment. CONCLUSION: In present study, we demonstrated tumor inhibitory effect of SEMA3A antibody in GBM progression and present its potential relevance as a therapeutic agent in a clinical framework.

Urinary semaphorin 3A as an early biomarker to predict contrast-induced acute kidney injury in patients undergoing percutaneous coronary intervention

Contrast-induced acute kidney injury (CI-AKI) is a serious complication of diagnostic coronary angiograph and percutaneous coronary intervention (PCI). However, the exact pathophysiological mechanisms underlying CI-AKI development are largely unknown. The present study examined whether urinary semaphorin 3A levels predict the development of CI-AKI in patients undergoing PCI. This study enrolled 168 patients with stable angina undergoing elective PCI. Serial urine samples, obtained at baseline and 2, 6, 12, 24, 36, and 48 h post-PCI were analyzed by semaphorin 3A and neutrophil gelatinase-associated lipocalin (NGAL) ELISA kit. AKI was defined as an increase in serum creatinine beyond 50% according to the RIFLE classification system. Receiver operator characteristic (ROC) curve analyses identified optimal semaphorin 3A and NGAL values for diagnosing CI-AKI. CI-AKI occurred in 20 of 168 patients. There were no significant differences in the baseline clinical characteristics and angiographic findings between non-AKI patients group and AKI patients group. Both urinary semaphorin 3A and NGAL levels significantly increased at 2 and 6 h post-PCI. ROC analysis showed that the cut-off value of 389.5 pg/mg semaphorin 3A at 2 h post-PCI corresponds to 94% sensitivity and 75% specificity and the cut-off value of 94.4 ng/mg NGAL at 2 h post-PCI corresponds to 74% sensitivity and 82% specificity. Logistic regression showed that semaphorin 3A levels at 2 and 6 h post-PCI were the significant predictors of AKI in our cohort. Urinary semaphorin 3A may be a promising early biomarker for predicting CI-AKI in patients undergoing PCI.

Neuroprotective Effect of Lacosamide on Hypoxic-Ischemic Brain Injury in Neonatal Rats

BACKGROUND AND PURPOSE: Lacosamide (LCM) is an antiepileptic drug that enhances the slow inactivation of sodium channels and modulates collapsin response mediator protein-2. LCM was recently demonstrated to exert a neuroprotective effect in a murine model of traumatic brain injury and status epilepticus. Assuming the same underlying excitotoxicity-related brain injury mechanism, we hypothesized that LCM would have a neuroprotective effect in hypoxic-ischemic brain injury. METHODS: We divided rats into three groups at each testing session: pre- or postfed with LCM, fed with normal saline, and sham. A hypoxic-ischemic brain injury was induced by subjecting 7-day-old rats to right carotid artery coagulation followed by 2.5 h of exposure to 8% oxygen. The animals were killed on postnatal day 12 to evaluate the severity of brain damage. Open field testing was also performed between week 2 and week 6, and the Morris water maze test was performed in week 7 after hypoxia-ischemia. RESULTS: The incidence of liquefactive cerebral infarction was lower in rats prefed with LCM at 100 mg/kg/dose, with the mortality rate being higher at higher doses (200 and 300 mg/kg/dose). The infarct areas were smaller in LCM-prefed rats in several brain regions including the hemisphere, hippocampus, cortex, and striatum. Spatial learning and memory function were better in LCM-prefed rats (p<0.05). No effect was observed in postfed rats. CONCLUSIONS: This study suggests that LCM pretreatment exerts a neuroprotective effect on hypoxia-ischemia in neonatal rats. The obtained results suggest that LCM pretreatment could be used as an effective neuroprotective method for neonates under hypoxic-ischemic conditions including heart surgery.

MicroRNA-143 and -145 modulate the phenotype of synovial fibroblasts in rheumatoid arthritis

Fibroblast-like synoviocytes (FLSs) constitute a major cell subset of rheumatoid arthritis (RA) synovia. Dysregulation of microRNAs (miRNAs) has been implicated in activation and proliferation of RA-FLSs. However, the functional association of various miRNAs with their targets that are characteristic of the RA-FLS phenotype has not been globally elucidated. In this study, we performed microarray analyses of miRNAs and mRNAs in RA-FLSs and osteoarthritis FLSs (OA-FLSs), simultaneously, to validate how dysregulated miRNAs may be associated with the RA-FLS phenotype. Global miRNA profiling revealed that miR-143 and miR-145 were differentially upregulated in RA-FLSs compared to OA-FLSs. miR-143 and miR-145 were highly expressed in independent RA-FLSs. The miRNA-target prediction and network model of the predicted targets identified insulin-like growth factor binding protein 5 (IGFBP5) and semaphorin 3A (SEMA3A) as potential target genes downregulated by miR-143 and miR-145, respectively. IGFBP5 level was inversely correlated with miR-143 expression, and its deficiency rendered RA-FLSs more sensitive to TNFα stimulation, promoting IL-6 production and NF-κB activity. Moreover, SEMA3A was a direct target of miR-145, as determined by a luciferase reporter assay, antagonizing VEGF165-induced increases in the survival, migration and invasion of RA-FLSs. Taken together, our data suggest that enhanced expression of miR-143 and miR-145 renders RA-FLSs susceptible to TNFα and VEGF165 stimuli by downregulating IGFBP5 and SEMA3A, respectively, and that these miRNAs could be therapeutic targets.

Effect of endostar combined with cisplatin on expression of VEGF and Sema3A of Lewis lung cancer rats

OBJECTIVE@#To evaluate the therapeutic effect of endostar (ED) combined with cisplatin(DDP) on model of C57BL/6 rats, and to further investigate the inhibiting mechanism of endostar from tumor angiogenesis.@*METHODS@#Lewis lung cancer cells were inoculated in C57BL/6 mouse, then the mouse were randomized into control group (group A), ED (group B), DDP (group C) and ED/DDP (group D). They were treated according to the plan. And the expressions of VEGF and Sema3A were evaluated by immunhistochemisty.@*RESULTS@#The weight of tumor increased in group A and B. It was decreased in group C and D. The tumor volume was increased in all the 4 groups. The VEGF expression of group D was obviously lower than the other group 3, but the Sema3A expressed of group D was significantly strengthener than the other group 3. The VEGF expression of group B and group D were obviously low especially in the 4th-8th days. Pearson correlated analysis showed that the expression VEGF and Sema3A were negatively correlated (r=-0.72, P<0.05).@*CONCLUSIONS@#ED combined with DDP could control the tumor growth effectively, and avoid weight loss. ED could reduce VEGF expression, and enhance Sema3A expression. Tumor vessel presents transient normalization. It is easy for DDP perfusion, and to kill tumor cells.

Ferulic acid regulates the AKT/GSK-3beta/CRMP-2 signaling pathway in a middle cerebral artery occlusion animal model / 한국실험동물학회지

Ferulic acid, a component of the plants Angelica sinensis (Oliv.) Diels and Ligusticum chuanxiong Hort, exerts a neuroprotective effect by regulating various signaling pathways. This study showed that ferulic acid treatment prevents the injury-induced increase of collapsin response mediator protein 2 (CRMP-2) in focal cerebral ischemia. Glycogen synthase kinase-3beta (GSK-3beta) regulates CRMP-2 function through phosphorylation of CRMP-2. Moreover, the pro-apoptotic activity of GSK-3beta is inactivated by phosphorylation by Akt. This study investigated whether ferulic acid modulates the expression of CRMP-2 and its upstream targets, Akt and GSK-3beta, in focal cerebral ischemia. Male rats were treated immediately with ferulic acid (100 mg/kg, i.v.) or vehicle after middle cerebral artery occlusion (MCAO), and then cerebral cortices were collected 24 hr after MCAO. MCAO resulted in decreased levels of phospho-Akt and phospho-GSK-3beta, while ferulic acid treatment prevented the decrease in the levels of these proteins. Moreover, phospho-CRMP-2 and CRMP-2 levels increased during MCAO, whereas ferulic acid attenuated these injury-induced increases. These results demonstrate that ferulic acid regulates the Akt/GSK-3beta/CRMP-2 signaling pathway in focal cerebral ischemic injury, thereby protecting against brain injury.

Expression of Semaphorin 3A and Neuropilin 1 in Asthma

Neuropilin 1 (NP1) is a part of essential receptor complexes mediating both semaphorin3A (SEMA3A) and vascular endothelial growth factor (VEGF) which is one of important mediators involved in the pathogenesis of asthma. Therefore, it is possible that SEMA3A plays a role in the pathogenesis of asthma through attenuation of VEGF-mediated effects. In the present study, we aimed to evaluate expression levels of SEMA3A and NP1 using induced sputum of asthmatics and a murine model of asthma. Firstly, SEMA3A and NP1 expressions in induced sputum of asthmatics and SEMA3A and NP1 expression on bronchoalveolar lavage (BAL) cells and lung homogenates of asthmatic mice were determined. Then we evaluated the immunolocalization of VEGF receptor 1 (VEGFR1), VEGF receptor 2 (VEGFR2), and NP1 expressions on asthmatic mice lung tissue and their subcellular distributions using fibroblast and BEAS2B cell lines. Sputum SEMA3A and NP1 expressions were significantly higher in asthmatics than controls. Similarly, SEMA3A and NP1 expressions on BAL cells and lung homogenates were significantly elevated in asthmatic mice compared to control mice. Immunohistochemical analysis showed that VEGFR1, VEGFR2, and NP1 expressions were also uniformly increased in asthmatic mice. Our observations suggest that SEMA3A and NP1 may play important roles in the pathogenesis of asthma.

Increased expression of myocardial semaphorin 3A in isoproterenol-induced heart failure rats / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Maintenance of normal cardiac function is controlled by the autonomic nervous system. In congestive heart failure (CHF), sympathetic nerve denervation is increasingly recognized. The sympathetic fiber density depends on the balance between neurotrophins and neural guidance molecules. Semaphorin 3A (sema3a), a secreted neural guidance factor, is a well characterized member of the newly found semaphorin family. It can induce sympathetic growth cone collapse and axon repulsion. We conducted this study to investigate cell sources of sema3a in the heart, the expression level of sema3a in CHF and discuss the possible role of sema3a in CHF.</p><p><b>METHODS</b>Rats were divided into four groups: 30 days control group rats, 30 days CHF rats, 60 days control group rats, 60 days CHF rats. The heart failure model was induced by injection of isoproterenol (ISO) 340 mg/kg continuously two days. All animals underwent echocardiography and haemodynamics measurements. Cardiac expression of sema3a was determined by real time polymerase chain reaction (RT-PCR) and Western blotting analysis. Immunohistochemical analysis was used to determine the cell source of sema3a in the heart.</p><p><b>RESULTS</b>Isoproterenol induced 30 days and 60 days CHF rats displayed left ventricular dilation, systolic and diastolic function decrease. Sema3a was secreted by the cardiocytes and increased significantly in 30 days and 60 days CHF rats compared with the controls (RT-PCR: 30 days group: 0.32 ± 0.05 vs. 0.58 ± 0.06, P < 0.01; 60 days group: 0.34 ± 0.08 vs. 0.71 ± 0.07, P < 0.01. Western blotting: 30 days group: 0.25 ± 0.10 vs. 0.46 ± 0.10, P < 0.05; 60 days group: 0.29 ± 0.10 vs. 0.55 ± 0.16, P < 0.01. Immunohistochemical analysis: 30 days group: 2.91 ± 0.20 vs. 5.31 ± 0.30, P < 0.01; 60 days group: 2.94 ± 0.30 vs. 5.80 ± 0.30, P < 0.01).</p><p><b>CONCLUSIONS</b>Sema3a was expressed in the heart by cardiocytes. Increased expression of sema3a may partly account for sympathetic denervation in CHF; modulation of this pathway may prove beneficial in heart failure sympathetic remodeling.</p>

Effects of Sema3A derived from tumor cells on functions of dendritic cells / 浙江大学学报·医学版

<p><b>OBJECTIVE</b>To investigate the effects of tumor cell-derived Sema3A on the immunological functions of murine dendritic cells (DCs).</p><p><b>METHODS</b>Lung adenocarcinoma A549 cells were transfected with small interference RNA, Si-Sema and Si-mut, and the interference efficiency was determined by real-time PCR and Western-blot. The concentrated supernatants from cultured tumor cells, Si-Sema and Si-mut-infected tumor cells were subjected to DCs respectively. The immunophenotypes of DCs were analyzed by flow cytometry, the production of IL-12P70 and the ability of DCs to stimulate DO11. 10 T cells secreting IFN-gamma and IL-2 were detected by enzyme linked immunosorbent assay (ELISA).</p><p><b>RESULTS</b>Knockdown with Si-Sema3A significantly decreased the secretion of Sema3A by A549 cells in comparison with the Si-mut cells. DCs exposed to supernatants from Si-Sema cells showed elevated levels of MHC, CD40 and CD80, more production of IL-12P70, and enhanced capability of activating antigen-specific T cells, as evidenced by the remarkably increased levels of IFN-gamma and IL-2.</p><p><b>CONCLUSION</b>A549 cells secrete Sema3A to inhibit the maturation and functions of DCs, which might be associated with the unidentified mechanism of immune evasion by tumor cells.</p>

A Role of Staphyococcus aureus, Interleukin-18, Nerve Growth Factor and Semaphorin 3A, an Axon Guidance Molecule, in Pathogenesis and Treatment of Atopic Dermatitis

Staphylococcus aureus (SA) is usually present not only in the skin lesions of atopic dermatitis (AD) but also in the atopic dry skin. SA discharges various toxins and enzymes that injure the skin, results in activation of epidermal keratinocytes, which produce and release IL-18. IL-18 that induces the super Th1 cells secreting IFN-gamma and IL-13 is supposed to be involved in development of AD and its pathogenesis. Indeed, the number of SA colonies on the skin surface and the serum IL-18 levels in patients with AD significantly correlated with the skin scores of AD lesions. Also, there is strong positive correlation between the skin scores and serum IL-18 levels in DS-Nh mice (P<0.0001, r=0.64), which develop considerable AD-like legions when they are housed under conventional conditions, but develop skin legions with less severity and less frequency under specific pathogens free (SPF) conditions. Therefore, they are well-known as model mice of AD, in which SA is presumed to be critical factor for the development of AD lesions. Also, theses DS-Nh mice pretreated with Cy developed more remarkable AD-like lesions in comparison with non-treated ones. The levels of INF-r and IL-13 in the supernatants of the lymph node cell cultures stimulated with staphylococcal enterotoxin B (SEB) or ConA were increased in the Cy-treated mice, although the serum levels of total IgE were not. In this experiment, we revealed that Cy-treated mice, to which CD25 +CD4 + reguratory T cells taken from non-treated ones had been transferred, developed the AD-like legions with less severity and less number of SA colonies on the skin surface. Therefore, it is presumed that CD25 +CD4 + reguratory T cells might be involved in the suppression of super Th1 cells which are induced by IL-18 and are involved in the development of AD-like lesions rather than IgE production. The efficient induction of CD25 +CD4 + reguratory T cells is expected for the new type of treatment of AD. We also found that farnesol (F) and xylitol (X) synergistically inhibited biofilm formation by SA, and indeed the ratio of SA in total bacteria at sites to which the FX cream containing F and X had been applied was significantly decreased 1 week later, accompanied with improvement of AD, when compared with that before application and at placebo sites. Therefore, the FX cream is a useful skin-care agent for atopic dry skin colonized by SA. The nerve growth factor (NGF) in the horny layer (the horn NGF) of skin lesions on the cubital fossa was collected by tape stripping and measured using ELISA in AD patients before and after 2 and 4 weeks treatments. Simultaneously, the itch and eruptions on the whole body and on the lesions, in which the horn NGF was measured, were recorded, and also the peripheral blood eosinophil count, serum LDH level and serum total IgE level were examined. The level of NGF was significantly higher in AD patients than in healthy controls, correlated with the severity of itch, erythema, scale/xerosis, the eosinophil count and LDH level, and also significantly decreased after treatments with olopatadine and/or steroid ointment for 2 and 4 weeks. Therefore, the measurement of the NGF by this harmless method seems to be useful to assess the severity of AD and the therapeutic effects on AD. In AD patients, C-fiber in the epidermis increase and sprout, inducing hypersensitivity, which is considered to aggravate the disease. Semaphorin 3A (Sema3A), an axon guidance molecule, is a potent inhibitor of neurite outgrowth of sensory neurons. We administered recombinant Sema3A intracutaneously into the skin lesions of NC/Nga mice, an animal model of AD, and investigated the effect of Sema3A on the skin lesions and their itch. Sema3A dose-dependently improved skin lesions and attenuated the scratching behavior in NC/Nga mice. Histological examinations revealed a decrease in the epidermal thickness, the density of invasive nerve fibers in the epidermis, inflammatory infiltrate including mast cells and CD4 +T cells, and the production of IL-4 in the Sema3A-treated lesions. Because the interruption of the itch-scratch cycle likely contributes to the improvement of the AD-like lesions, Sema3A is expected to become a promising treatment of patients with refractory AD.

Expression and Function of Plexin A1 in Rheumatoid Synoviocytes / 대한류마티스학회지

Objective: To investigate the expression and function of plexin A1, a transmembrane protein involving cell survival and cell-to cell interaction, in the rheumatoid synoviocytes. Methods: Immunohistochemical staining using anti-plexin A1 antibody was performed in the synovium of rheumatoid arthritis (RA) patients. The plexin A1 expression in cultured fibroblast-like synovioytes (FLS) was also examined by Western blot analysis and immunocytochemistry. Cell viability was determined by CCK-8 assay. Deficiency of plexin A1 was established by the method of short interfering RNA (siRNA). The productions of interleukin-6 (IL-6) and monocytes chemotactic protein-1 (MCP-1) were measured in culture supernatants by ELISA. Results: Plexin A1 was highly expressed in the lining layer of synovium and cultured FLS of RA patients. In RA FLS, basal expression of plexin A1 was higher than osteoarthritis FLS. On immunocytochemical staining, plexin A1 was co-expressed with neuropilin-1 in RA FLS. Semaphorin 3A (10 to 200 ng/mL), a specific ligand for neuropilin-1/plexin A1 complex, did not affect viability of RA FLS. The down regulation of plexin A1 mRNA by siRNA did not cause cell death, either. Co-culture of FLS with RA T cells, isolated from peripheral blood or synovial fluid, caused an increase in the productions of IL-6 and MCP-1 from FLS, but which were blocked by down-regulating plexin A1 transcripts using siRNA method. Conclusion: These data suggest that enhanced expression of plexin A1 in RA FLS may elicit over-production of IL-6 and MCP-1, and thereby contribute to perpetuation of chronic inflammation in RA.