Biallelic human SHARPIN loss of function induces autoinflammation and immunodeficiency.

The linear ubiquitin assembly complex (LUBAC) consists of HOIP, HOIL-1 and SHARPIN and is essential for proper immune responses. Individuals with HOIP and HOIL-1 deficiencies present with severe immunodeficiency, autoinflammation and glycogen storage disease. In mice, the loss of Sharpin leads to severe dermatitis due to excessive keratinocyte cell death. Here, we report two individuals with SHARPIN deficiency who manifest autoinflammatory symptoms but unexpectedly no dermatological problems. Fibroblasts and B cells from these individuals showed attenuated canonical NF-κB responses and a propensity for cell death mediated by TNF superfamily members. Both SHARPIN-deficient and HOIP-deficient individuals showed a substantial reduction of secondary lymphoid germinal center B cell development. Treatment of one SHARPIN-deficient individual with anti-TNF therapies led to complete clinical and transcriptomic resolution of autoinflammation. These findings underscore the critical function of the LUBAC as a gatekeeper for cell death-mediated immune dysregulation in humans.

Recapitulating the human segmentation clock with pluripotent stem cells.

Pluripotent stem cells are increasingly used to model different aspects of embryogenesis and organ formation1. Despite recent advances in in vitro induction of major mesodermal lineages and cell types2,3, experimental model systems that can recapitulate more complex features of human mesoderm development and patterning are largely missing. Here we used induced pluripotent stem cells for the stepwise in vitro induction of presomitic mesoderm and its derivatives to model distinct aspects of human somitogenesis. We focused initially on modelling the human segmentation clock, a major biological concept believed to underlie the rhythmic and controlled emergence of somites, which give rise to the segmental pattern of the vertebrate axial skeleton. We observed oscillatory expression of core segmentation clock genes, including HES7 and DKK1, determined the period of the human segmentation clock to be around five hours, and demonstrated the presence of dynamic travelling-wave-like gene expression in in vitro-induced human presomitic mesoderm. Furthermore, we identified and compared oscillatory genes in human and mouse presomitic mesoderm derived from pluripotent stem cells, which revealed species-specific and shared molecular components and pathways associated with the putative mouse and human segmentation clocks. Using CRISPR-Cas9-based genome editing technology, we then targeted genes for which mutations in patients with segmentation defects of the vertebrae, such as spondylocostal dysostosis, have been reported (HES7, LFNG, DLL3 and MESP2). Subsequent analysis of patient-like and patient-derived induced pluripotent stem cells revealed gene-specific alterations in oscillation, synchronization or differentiation properties. Our findings provide insights into the human segmentation clock as well as diseases associated with human axial skeletogenesis.

Peripheral helper T cells, mavericks of peripheral immune responses.

Peripheral helper T (Tph) cells have been established, through intensive efforts to elucidate local immune responses in human rheumatoid arthritis (RA), as a CD4 subset intimately involved in acquired immunity in peripheral tissues. Initially, Tph cells were noted as a CD4 population that produces high levels of CXCL13 in RA synovial tissues, followed by a demonstration of their ability to help B cells. In contrast to follicular helper T (Tfh) cells, Tph cells do not express the transcription factor BCL6 but express molecules such as CXCL13, interleukin (IL)-21, and inducible T-cell costimulator (ICOS) to help B cells in peripheral tissues. Subsequent studies showed that Tph cells are associated with various diseases, including autoimmune diseases, infections, and malignancies, and with the development of early life immunity. This review summarizes the phenotype and function of Tph cells in RA and discusses their differentiation and diversity in various conditions.

Subacute stent thrombosis with spontaneously resolved secondary thrombi in paroxysmal nocturnal hemoglobinuria: a case report.

BACKGROUND: Stent thrombosis (ST) is a serious complication; however, a method to prevent ST in patients with thrombophilic diseases has not been established. CASE PRESENTATION: We report a case of subacute ST in a patient with paroxysmal nocturnal hemoglobinuria (PNH) who was receiving continuous heparin treatment in addition to the usual dual antiplatelet therapy for contrast defects at the proximal site of the occluded right coronary artery and the proximal site of the left circumflex artery. Despite the resolution of thrombi in secondary lesions, subacute ST occurred. After percutaneous coronary intervention for ST, triple therapy, including oral anticoagulation for PNH-related thrombosis, was initiated. The patient subsequently underwent craniotomy hematoma removal for hemorrhagic cerebral infarction. CONCLUSIONS: Reported cases of ST in patients with PNH are very few, and this case adds evidence with respect to antithrombotic therapy in patients with thrombotic tendencies. Both thrombosis and bleeding should be considered when administering antithrombotic therapy to patients with thrombotic diseases. If there are specific treatments for thrombophilic diseases, they should be initiated early.

Combinational Elastography.

Heart failure (HF) can cause liver congestion and stiffness. Elastography is used to noninvasively measure organ stiffness. Liver fibrosis (LF) is monitored by shear wave and strain elastography. However, shear wave velocity (Vs) on shear wave elastography varies under the influence of fibrosis and congestion, and the LF index by strain elastography reflects only LF progression. Little is known about the usefulness of these methods in HF patients. This prospective study evaluated combined shear wave and strain elastography (i.e., combinational elastography) for assessing liver congestion. A total of 51 patients with HF (33 outpatients and 18 inpatients) and 10 healthy participants were included. Further, the relationships between combinational elastography and clinical characteristics in 51 patients with HF and the effects of medical treatment on these relationships in 18 inpatients with HF were investigated. Vs was significantly higher in the HF group than in the control group (1.68 ± 0.47 versus 1.21 ± 0.16, P = 0.002). The LF index did not significantly differ (1.39 ± 0.40 versus 1.33 ± 0.15, P = 0.680). Vs decreased after treatment (from 2.01 ± 0.61 to 1.62 ± 0.49 m/seconds; P = 0.026), while the LF index did not change (from 1.21 ± 0.29 to 1.26 ± 0.27; P = 0.664). Brain natriuretic peptide level (r = 0.343; P = 0.003) and composite congestion scores (r = 0.455; P < 0.001) were correlated with Vs. Combinational elastography is useful for assessing liver congestion, differentiating between liver congestion and fibrosis, and assessing therapeutic effects in HF patients.

Wide-Scale Gene Flow, Even in Insects that have Lost their Flight Ability: Presence of Dispersion Due to a Unique Parasitic Ecological Strategy of Piggybacking Hosts.

We focused on Meloe beetles that have lost all flight ability, and conducted molecular phylogeographic analyses based on their mitochondrial DNA COI and nuclear DNA EF1- α regions. Meloe beetles infiltrate bumblebee nests by attaching to bumblebees as they pollinate flowers and thereafter have a unique and specific life history as they complete their life-cycle within the host nest; flight-based dispersal is achieved by piggybacking on bumblebees. In fact, Meloe beetles, which cannot fly, even inhabit remote islands (i.e., "Oceanic Islands"). Regarding four species, i.e., Meloe coarctatus, Meloe proscarabaeus, Meloe violaceus and Meloe corvinus, the conventional morphological classification system based on morphological characteristics was strongly supported by the molecular markers. On the other hand, for two species, Meloe menoko and Meloe auriculatus, it was found that M. menoko may be evaluated as having a paraphyletic relationship with M. auriculatus. Furthermore, two other cryptic, undescribed species were also discovered in this study. One was collected in the Nikko Highland, and inhabited the area sympatrically with M. coarctatus. The other was collected from Hachijo-jima Island. These cryptic species were highly differentiated, independent lineages in terms of mitochondrial and nuclear gene regions. That is to say, a new level of species diversity was revealed among the Meloe beetle species, known for their unique and strange ecological and ethological characteristics.

Integration of genetics and miRNA-target gene network identified disease biology implicated in tissue specificity.

MicroRNAs (miRNAs) modulate the post-transcriptional regulation of target genes and are related to biology of complex human traits, but genetic landscape of miRNAs remains largely unknown. Given the strikingly tissue-specific miRNA expression profiles, we here expand a previous method to quantitatively evaluate enrichment of genome-wide association study (GWAS) signals on miRNA-target gene networks (MIGWAS) to further estimate tissue-specific enrichment. Our approach integrates tissue-specific expression profiles of miRNAs (∼1800 miRNAs in 179 cells) with GWAS to test whether polygenic signals enrich in miRNA-target gene networks and whether they fall within specific tissues. We applied MIGWAS to 49 GWASs (nTotal = 3 520 246), and successfully identified biologically relevant tissues. Further, MIGWAS could point miRNAs as candidate biomarkers of the trait. As an illustrative example, we performed differentially expressed miRNA analysis between rheumatoid arthritis (RA) patients and healthy controls (n = 63). We identified novel biomarker miRNAs (e.g. hsa-miR-762) by integrating differentially expressed miRNAs with MIGWAS results for RA, as well as novel associated loci with significant genetic risk (rs56656810 at MIR762 at 16q11; n = 91 482, P = 3.6 × 10-8). Our result highlighted that miRNA-target gene network contributes to human disease genetics in a cell type-specific manner, which could yield an efficient screening of miRNAs as promising biomarkers.

Soluble Lectin-like Oxidized Low-Density Lipoprotein Receptor 1 Predicts the Changes of Rheumatoid Factor Titers in Rheumatoid Arthritis.

OBJECTIVE: The aim of this longitudinal study was to examine the clinical significance of soluble lectin-like oxidized low-density lipoprotein receptor 1 (sLOX-1) in patients with rheumatoid arthritis. METHODS: We gathered demographic and clinical data for a large rheumatoid arthritis cohort at 3 time points. Blood samples were collected at each time point; the number of samples was 282 cases in 2012, 431 cases in 2013, and 500 cases in 2014. Plasma sLOX-1 was measured by enzyme-linked immunosorbent assay. Correlations between sLOX-1 and clinical data were analyzed. Predictive factors associated with changes in sLOX-1 and rheumatoid factor (RF) were analyzed by multivariate linear regression. RESULTS: Plasma sLOX-1 level was significantly correlated with RF titer and other clinical parameters. The longitudinal analyses showed that changes in sLOX-1 were significantly correlated with changes in RF titers and with those at baseline. Multivariate linear regression analysis revealed that changes in RF and baseline RF were predictive factors for changes in sLOX-1. Conversely, the changes in RF were significantly correlated with the changes in sLOX-1 in all years. A stepwise regression analysis showed that the change in sLOX-1 was a predictive factor for the change in RF. CONCLUSIONS: The change in sLOX-1 has predictive value for assessing the change in RF, indicating the usefulness of sLOX-1 in clinical practice.

Constitutive Activation of Integrin α9 Augments Self-Directed Hyperplastic and Proinflammatory Properties of Fibroblast-like Synoviocytes of Rheumatoid Arthritis.

Despite advances in the treatment of rheumatoid arthritis (RA), currently approved medications can have significant side effects due to their direct immunosuppressive activities. Additionally, current therapies do not address residual synovial inflammation. In this study, we evaluated the role of integrin α9 and its ligand, tenascin-C (Tn-C), on the proliferative and inflammatory response of fibroblast-like synoviocytes (FLSs) from RA patients grown in three-dimensional (3D)-micromass culture. FLSs from osteoarthritis patients, when grown in the 3D-culture system, formed self-directed lining-like structures, whereas FLSs from RA tissues (RA-FLSs) developed an abnormal structure of condensed cellular accumulation reflective of the pathogenic features of RA synovial tissues. Additionally, RA-FLSs grown in 3D culture showed autonomous production of proinflammatory mediators. Predominant expression of α9 and Tn-C was observed in the condensed lining, and knockdown of these molecules abrogated the abnormal lining-like structure formation and suppressed the spontaneous expression of matrix metalloproteinases, IL-6, TNFSF11/RANKL, and cadherin-11. Disruption of α9 also inhibited expression of Tn-C, suggesting existence of a positive feedback loop in which the engagement of α9 with Tn-C self-amplifies its own signaling and promotes progression of synovial hyperplasia. Depletion of α9 also suppressed the platelet-derived growth factor-induced hyperplastic response of RA-FLSs and blunted the TNF-α-induced expression of matrix metalloproteinases and IL-6. Finally, α9-blocking Ab also suppressed the formation of the condensed cellular lining by RA-FLSs in 3D cultures in a concentration-related manner. This study demonstrates the central role of α9 in pathogenic behaviors of RA-FLSs and highlights the potential of α9-blocking agents as a nonimmunosuppressive treatment for RA-associated synovitis.

Permanent Pacing in a Patient with Left Ventricular Mid-Cavity Obstruction and Apical Aneurysm.

Hypertrophic cardiomyopathy with left ventricular (LV) mid-cavity obstruction and LV apical aneurysm is associated with high morbidity and mortality rates. However, consensus is lacking on the treatment modality for LV mid-cavity obstruction and LV apical aneurysm. Here, we report a case of reduced LV mid-cavity pressure gradient and symptoms, treated using permanent pacing. The effect of permanent pacing on pressure gradient and symptoms lasted for 4 years. As pacing is relatively non-invasive compared to surgical therapy, permanent pacing is a good option, especially in the elderly patients with LV mid-cavity obstruction and apical aneurysm.

Factors influencing spinal sagittal balance, bone mineral density, and Oswestry Disability Index outcome measures in patients with rheumatoid arthritis.

PURPOSE: To identify the factors influencing spinal sagittal alignment, bone mineral density (BMD), and Oswestry Disability Index (ODI) outcome measures in patients with rheumatoid arthritis (RA). METHODS: We enrolled 272 RA patients to identify the factors influencing sagittal vertical axis (SVA). Out of this, 220 had evaluation of bone mineral density (BMD) and vertebral deformity (VD) on the sagittal plane; 183 completed the ODI questionnaire. We collected data regarding RA-associated clinical parameters and standing lateral X-ray images via an ODI questionnaire from April to December 2012 at a single center. Patients with a history of spinal surgery or any missing clinical data were excluded. Clinical parameters included age, sex, body mass index, RA disease duration, disease activity score 28 erythrocyte sedimentation rate (DAS28-ESR), serum anti-cyclic citrullinated peptide antibody, serum rheumatoid factor, serum matrix metalloproteinase-3, BMD and treatment type at survey, such as methotrexate (MTX), biological disease-modifying anti-rheumatic drugs, and glucocorticoids. We measured radiological parameters including pelvic incidence (PI), lumbar lordosis (LL), and SVA. We statistically identified the factors influencing SVA, BMD, VD, and ODI using multivariate regression analysis. RESULTS: Multivariate regression analysis showed that larger SVA correlated with older age, higher DAS28-ESR, MTX nonuse, and glucocorticoid use. Lower BMD was associated with female, older age, higher DAS28-ESR, and MTX nonuse. VD was associated with older age, longer disease duration, lower BMD, and glucocorticoid use. Worse ODI correlated with older age, larger PI-LL mismatch or larger SVA, higher DAS28-ESR, and glucocorticoid use. CONCLUSIONS: In managing low back pain and spinal sagittal alignment in RA patients, RA-related clinical factors and the treatment type should be taken into consideration.

A Case of Left Ventricular Thrombus with Superior Mesenteric Vein Thrombosis Due to Atopic Dermatitis.

A 55-year-old man was presented to the emergency room because of abdominal pain for 4 days. He had a history of atopic dermatitis. Left ventricular (LV) asynergy and thrombus was detected on echocardiography, and superior mesenteric vein thrombosis was detected by computed tomography. There are no reported cases of this combination of thrombi. We hypothesized that the reason for this complication is the combination of coagulation disorder due to atopic dermatitis, silent myocardial infarction, and exacerbation of the coagulation abnormality due to bacteremia, leading to superior mesenteric vein and LV thrombosis. Atopic dermatitis that has potential risk factors of thrombus with sepsis could provoke thrombophilic state. Atopic dermatitis is a common disease, but continuous medical care is essential.

TGF-ß induces the differentiation of human CXCL13-producing CD4(+) T cells.

In the ectopic lymphoid-like structures present in chronic inflammatory conditions such as rheumatoid arthritis, a subset of human effector memory CD4(+) T cells that lacks features of follicular helper T (Tfh) cells produces CXCL13. Here, we report that TGF-ß induces the differentiation of human CXCL13-producing CD4(+) T cells from naïve CD4(+) T cells. The TGF-ß-induced CXCL13-producing CD4(+) T cells do not express CXCR5, B-cell lymphoma 6 (BCL6), and other Tfh-cell markers. Furthermore, expression levels of CD25 (IL-2Rα) in CXCL13-producing CD4(+) T cells are significantly lower than those in FoxP3(+) in vitro induced Treg cells. Consistent with this, neutralization of IL-2 and knockdown of STAT5 clearly upregulate CXCL13 production by CD4(+) T cells, while downregulating the expression of FoxP3. Furthermore, overexpression of FoxP3 in naïve CD4(+) T cells downregulates CXCL13 production, and knockdown of FoxP3 fails to inhibit the differentiation of CXCL13-producing CD4(+) T cells. As reported in rheumatoid arthritis, proinflammatory cytokines enhance secondary CXCL13 production from reactivated CXCL13-producing CD4(+) T cells. Our findings demonstrate that CXCL13-producing CD4(+) T cells lacking Tfh-cell features differentiate via TGF-ß signaling but not via FoxP3, and exert their function in IL-2-limited but TGF-ß-rich and proinflammatory cytokine-rich inflammatory conditions.

Subsidence of total ankle component associated with deterioration of an ankle scale in non-inflammatory arthritis but not in rheumatoid arthritis.

OBJECTIVES: Modern three-component total ankle arthroplasty (TAA) has favorable clinical results and survival rates. However, radiographic deterioration and worsening of clinical symptoms may occur in patients with rheumatoid arthritis (RA) or non-inflammatory arthritis (NA). The associations between outcomes and clinical and radiological factors are not clear. We compared midterm clinical and radiographic outcomes after TAA between patients with RA and those with NA. METHODS: Twenty-six TAAs were performed using a three-component prosthesis, the FINE Total Ankle System during the study period. Fourteen TAAs with 11 RA patients undergoing primary TAA were compared with twelve TAAs with 12 NA patients. Clinical and radiographic outcomes were evaluated before and after operation, and at the final follow-up. RESULTS: The Japanese Society for Surgery of the Foot (JSSF) scale improved significantly following TAA in both groups (p = 0.0039 and 0.0156, respectively). Tibial subsidence, talar subsidence and age were significantly associated with postoperative JSSF score only in the NA group (p = 0.0027, 0.0017 and p < 0.0001, respectively). Stepwise regression analysis showed that talar subsidence was an independent predictor of a worse JSSF score in the NA group (F = 10.3). CONCLUSIONS: The final clinical outcome was negatively influenced by talar subsidence in patients with NA, but not in those with RA.

Cell-contact-dependent activation of CD4+ T cells by adhesion molecules on synovial fibroblasts.

OBJECTIVE: To determine how cell-cell contact with synovial fibroblasts (SF) influence on the proliferation and cytokine production of CD4+ T cells. METHODS: Naïve CD4+ T cells were cultured with SF from rheumatoid arthritis patients, stimulated by anti-CD3/28 antibody, and CD4+ T cell proliferation and IFN-γ/IL-17 production were analyzed. To study the role of adhesion molecules, cell contact was blocked by transwell plate or anti-intracellular adhesion molecule-1 (ICAM-1)/vascular cell adhesion molecule-1(VCAM-1) antibody. To study the direct role of adhesion molecules for CD4+ T cells, CD161+ or CD161- naïve CD4+ T cells were stimulated on plastic plates coated by recombinant ICAM-1 or VCAM-1, and the source of IFN-γ/IL-17 were analyzed. RESULTS: SF enhanced naïve CD4+ T cell proliferation and IFN-γ/IL-17 production in cell-contact and in part ICAM-1-/VCAM-1-dependent manner. Plate-coated ICAM-1 and VCAM-1 enhanced naïve CD4+ T cell proliferation and IFN-γ production, while VCAM-1 efficiently promoting IL-17 production. CD161+ naïve T cells upregulating LFA-1 and VLA-4 were the major source of IFN-γ/IL-17 upon interaction with ICAM-1/VCAM-1. CONCLUSION: CD4+ T cells rapidly expand and secrete IFN-γ/IL-17 upon cell-contact with SF via adhesion molecules. Interfering with ICAM-1-/VCAM-1 may be beneficial for inhibiting RA synovitis.

Limited extension after linked total elbow arthroplasty in patients with rheumatoid arthritis.

OBJECTIVE: Total elbow arthroplasty (TEA) has become an established procedure to relieve pain and to increase the range of motion of the destructed elbow in patients with rheumatoid arthritis (RA). However, some patients still have limited extension after TEA, and the causes of limited extension after TEA have yet to be elucidated. METHODS: To examine whether widening of the joint space can cause such limited extension, we retrospectively analyzed 55 cases of linked TEA in patients with RA. There were seven male and 40 female with a mean age of 63.8 years (range, 30-80 years) and a mean follow-up of 7.5 ± 4.2 years (range, 2.5-15.6 years). The Mayo Elbow Performance Score (MEPS) and radiological measurements were recorded. Widening of the joint space was calculated by subtracting the length measured on postoperative radiograph from preoperative radiograph. RESULTS: MEPS and range of motion were significantly improved after surgery except for extension. The degree of extension was significantly correlated with radiological widening of the joint space in the limited extension group. Correlation analyses showed that postoperative limited extension was correlated with lower MEPS daily function. CONCLUSIONS: Limited extension after linked TEA is partly derived from perioperative widening of the joint space and potentially limits daily function in patients with RA.

Awareness of salt restriction is not reflected in the actual salt intake in Japanese hypertensive patients.

OBJECTIVES: The Japanese guidelines for hypertension management recommend reducing salt intake to <6 g/day for hypertensive patients. However, it is not currently known whether hypertensive patients' awareness of the recommended reduced salt diet correlates with their actual intake. Therefore, the purpose of this study was to investigate the relationship between actual salt intake of Japanese hypertensive patients and their awareness of the recommended guidelines for reduced dietary salt intake. METHODS: In total, 236 outpatients (146 males and 90 females) with a mean age 69.7 ± 12.5 years were included in this study. Daily dietary salt intake was estimated using sodium and creatinine concentrations detected in spot urine samples. The patients filled out a questionnaire regarding their awareness of recommended salt restriction for hypertension management. The questionnaire distinguished the patients' awareness of recommended salt restriction in four levels (low, moderate, high and very high). RESULTS: The mean estimated salt intake was 9.72 ± 2.43 g/day. Patients' awareness regarding salt intake in all levels provided in the questionnaire did not correlate with actual salt intake (p = 0.731). CONCLUSION: Our results demonstrated that Japanese hypertensive outpatients consumed higher levels of salt than the target value recommended by Japanese guidelines. There was no correlation between actual salt intake and patients' awareness of the recommended reduction in salt. These results suggest that monitoring salt intake and informing patients of their actual salt intake are necessary for effective hypertension management.

Analysis of the Flexion Gap on In Vivo Knee Kinematics Using Fluoroscopy.

There is a paucity of information on the relationships between postoperative knee laxity and in vivo knee kinematics. The correlations were analyzed in 22 knees with axial radiographs and fluoroscopy based 3D model fitting approach after a tri-condylar total knee arthroplasty. During deep knee bend activities, the medial flexion gap had significant correlations with the medial contact point (r=0.529, P=0.011) and axial rotation at full extension. During kneeling activities, a greater medial flexion gap caused larger anterior translation at complete contact (r=0.568, P=0.011). Meanwhile, the lateral flexion gap had less effect. In conclusion, laxity of the medial collateral ligament should be avoided because the magnitude of medial flexion stability was crucial for postoperative knee kinematics.

Outcome of shortened extra-small ulnar component in linked total elbow arthroplasty for patients with rheumatoid arthritis.

OBJECTIVE: We compared the clinical and radiological results of the 3-inch shortened ulnar stem of the extra-small component of Coonrad-Morrey prosthesis with those of the other ulnar components for patients with rheumatoid arthritis (RA). METHODS: A total of 33 Coonrad-Morrey total elbow arthroplasty (TEA) procedures were performed. Of these, 27 elbows of 25 patients with RA underwent primary TEA. The results of the clinical and radiological findings were compared between groups of patients receiving the shortened ulnar stem of extra-small components (shortened group) and of those receiving the components of the other sizes (control group). RESULTS: The mean follow-up was 6.2 ± 2.8 years in the shortened group and 7.2 ± 2.5 years in the control group. The Mayo elbow performance score and range of motion results were substantially improved after the operation for both groups. We encountered several peri- and postoperative complications, but no significant differences in clinical results were found between the groups. The control group had three cases of osteolysis around the implant, while the shortened group did not. CONCLUSIONS: TEA with a shortened ulnar implant of the extra-small size of the Coonrad-Morrey prosthesis gave satisfactory mid-term results among patients with RA.

TNFα, PDGF, and TGFß synergistically induce synovial lining hyperplasia via inducible PI3Kδ.

OBJECTIVES: To determine the mechanism underlying hypertrophic synovium in rheumatoid arthritis (RA). METHODS: We examined micromass cultures of fibroblast-like synoviocytes (FLSs) stimulated with tumor necrosis factor α (TNFα), platelet-derived growth factor (PDGF), and/or transforming growth factor ß (TGFß). The hypertrophic architecture of the micromasses, expression of phosphoinositide 3 kinase (PI3K) isoforms, and persistent activation of PI3K-Akt pathways were investigated. FLSs transfected with siRNA were also examined in the micromass cultures. RESULTS: The combination of TNFα, PDGF, and TGFß (TPT condition) induced obvious hypertrophic architecture of the intimal lining layer in FLSs in micromass cultures, and was accompanied by upregulated expression of matrix metalloproteinase-3 (MMP3), Cadherin-11, and PI3Kδ. In monolayer FLSs, the TPT condition enhanced the expression of PI3Kδ and persistent activation of the PI3K-Akt pathway. Knockdown of PI3Kδ significantly inhibited the formation of the hypertrophic synovial lining in the TPT condition. CONCLUSIONS: These results collectively indicate that inducible PI3Kδ plays a crucial role in persistent activation of PI3K-Akt in FLSs, and in the formation of a hypertrophic synovial lining. PI3Kδ may be an alternative treatment target for the regulation of proliferative synovium in RA.