Emerging role of IκBζ in inflammation: Emphasis on psoriasis.

Psoriasis is a chronic inflammatory disorder affecting skin and joints that results from immunological dysfunction such as enhanced IL-23 induced Th-17 differentiation. IkappaB-Zeta (IκBζ) is an atypical transcriptional factor of the IκB protein family since, contrary to the other family members, it positively regulates NF-κB pathway by being exclusively localized into the nucleus. IκBζ deficiency reduces visible manifestations of experimental psoriasis by diminishing expression of psoriasis-associated genes. It is thus tempting to consider IκBζ as a potential therapeutic target for psoriasis as well as for other IL23/IL17-mediated inflammatory diseases. In this review, we will discuss the regulation of expression of NFKBIZ and its protein IκBζ, its downstream targets, its involvement in pathogenesis of multiple disorders with emphasis on psoriasis and evidences supporting that inhibition of IκBζ may be a promising alternative to current therapeutic managements of psoriasis.

Specificity of severe AKI aetiology and care in the elderly. The IRACIBLE prospective cohort study.

INTRODUCTION: Acute Kidney Injury (AKI) is increasingly common in people over 65 years of age, but its causes and management are poorly described. The purpose of this study was to describe the causes, management and prognosis of patients over 65 hospitalised for severe acute kidney injury (AKI) in all departments of a tertiary centre. METHOD: The prospective IRACIBLE (IRA: AKI in French; CIBLE: target in French) cohort included 480 patients hospitalised at a university hospital over 18 months for severe AKI or subgroup of AKIN3 (Acute Kidney Injury Network classification) defined by an acute creatinine increase > 354 µmol/L or managed with acute renal replacement therapy (RRT). The history, aetiology of AKI, management, and prognosis were compared in three age groups: < 65, 65-75, and > 75 years. RESULTS: The study population included 480 subjects (73% men) with a median body mass index (BMI) of 26.6 kg/m2 [23.3, 30.9], 176 (37%) diabetic patients, 124 (26%) patients < 65 years, 150 (31%) 65-75 years and 206 (43%) > 75 years. Increasing age class was associated with more comorbidities, a significantly lower median estimated glomerular filtration rate (eGFR) 6 months before inclusion (82; 62; 46 ml/min/1.73 m2, p < 0.05) and aetiology of AKI, which was more often obstructive (12%; 15%; 23%, p = 0.03) or part of a cardio-renal syndrome (6%; 9%; /15%, p = 0.04). Older patients were less often managed in the intensive care unit  (54%; 47%; 24%, p < 0.0001), were less frequently treated by RRT (52%; 43%; 31%, p < 0.001) and received fewer invasive treatments  (6%; 9%; 22%, p < 0.0001). Older survivors returned home less often (80%; 73%; 62%, p = 0.05) in favour of transfers to rehabilitation services (10%; 13%; 22%) with higher mortality at 3 months (35%; 32%; 50%, p < 0.0001). CONCLUSION: Older patients hospitalised for severe AKI have a specific profile with more comorbidities, lower baseline renal function, an aetiology of AKI of mainly extra-parenchymal causes and a complex pathway of care with an overall poor prognosis.

Anti-Inflammatory Activity of Bryophytes Extracts in LPS-Stimulated RAW264.7 Murine Macrophages.

Bryophytes produce rare and bioactive compounds with a broad range of therapeutic potential, and many species are reported in ethnomedicinal uses. However, only a few studies have investigated their potential as natural anti-inflammatory drug candidate compounds. The present study investigates the anti-inflammatory effects of thirty-two species of bryophytes, including mosses and liverworts, on Raw 264.7 murine macrophages stimulated with lipopolysaccharide (LPS) or recombinant human peroxiredoxin (hPrx1). The 70% ethanol extracts of bryophytes were screened for their potential to reduce the production of nitric oxide (NO), an important pro-inflammatory mediator. Among the analyzed extracts, two moss species significantly inhibited LPS-induced NO production without cytotoxic effects. The bioactive extracts of Dicranum majus and Thuidium delicatulum inhibited NO production in a concentration-dependent manner with IC50 values of 1.04 and 1.54 µg/mL, respectively. The crude 70% ethanol and ethyl acetate extracts were then partitioned with different solvents in increasing order of polarity (n-hexane, diethyl ether, chloroform, ethyl acetate, and n-butanol). The fractions were screened for their inhibitory effects on NO production stimulated with LPS at 1 ng/mL or 10 ng/mL. The NO production levels were significantly affected by the fractions of decreasing polarity such as n-hexane and diethyl ether ones. Therefore, the potential of these extracts to inhibit the LPS-induced NO pathway suggests their effective properties in attenuating inflammation and could represent a perspective for the development of innovative therapeutic agents.

Characteristics of outpatients referred for a first consultation with a nephrologist: impact of different guidelines.

INTRODUCTION: Chronic kidney disease (CKD) affects > 10% of the population but not all CKD patients require referral to a nephrologist. Various recommendations for referral to nephrologists are proposed worldwide. We examined the profile of French patients consulting a nephrologist for the first time and compared these characteristics with the recommendations of the International Kidney Disease: Improving Global Outcomes (KDIGO), the French "Haute Autorité de Santé" (HAS), and the Canadian Kidney Failure Risk Equation (KFRE). METHODS: University Hospital electronic medical records were used to study patients referred for consultation with a nephrologist for the first time from 2016 to 2018. Patient characteristics (age, sex, diabetic status, estimated glomerular filtration rate (eGFR) and urine protein-to-creatinine ratio (PCR), etiology reported by the nephrologist) and 1-year patient follow-up were analyzed and compared with the KDIGO, HAS and Canadian-KFRE recommendations for referral to a nephrologist. The stages were defined according to the KDIGO classification, based upon kidney function and proteinuria.  RESULTS: The 1,547 included patients had a median age of 71 [61-79] years with 56% males and 37% with diabetes. The main nephropathies were vascular (40%) and glomerular (20%). The KDIGO classification revealed 30%, 47%, 19%, 4% stages G1-2 to G5, and 50%, 22%, 28% stages A1-A3, respectively. According to KDIGO, HAS and KFRE scores, nephrologist referral was indicated for 42%, 57% and 80% of patients respectively, with poor agreement between recommendations. Furthermore, we observed 890 (57%) patients with an eGFR> 30 ml/min and  a urine protein to creatinine ratio 0.5 g/g, mostly aged over 65 years (67%); 40% were diabetic, and 57% had a eGFR > 45 ml/min/1.73m2, 56% were diagnosed as vascular nephropathy and 11% with unknown nephropathy. CONCLUSION: These results underline the importance of better identifying patients for referral to a nephrologist and informing general practitioners. Other referral criteria (age and etiology of the nephropathy) are debatable.

Physiological role of plasma and its components and the clinical implications of different methods of apheresis: A narrative review.

Nowadays, therapeutic plasmapheresis (TP) is accepted as part of the treatment for specific groups of diseases. The availability of different methods, including double filtration and adsorption, increases selectivity for the removal of substances. However, the use of these techniques requires a thorough understanding of the characteristics and components of plasma. By considering pivotal papers from several databases, the aim of this narrative review is to describe the characteristics of plasma related to apheresis techniques. We have tried to cover the clinical implications including physiology, estimation of plasma volume, viscosity, and a description of its components including the size, volume of distribution, and half-lives of the different substances to be removed or maintained depending on the clinical situation and applied apheresis technique. Applying this knowledge will help us to choose the right method and dosage and improve the efficacy of the procedure by preventing or addressing any complications.

Humanized anti CD-20 as an alternative in chronic management of relapsing thrombotic thrombocytopenic microangiopathy resistant to rituximab due to anti chimeric antibody.

Acquired Immune thrombotic thrombocytopenic purpura (iTTP) is considered among clinical situations that needs not only urgent treatment in acute setting but also long term management to prevent relapses. Important progresses have been made in management of these patients that are definitely associated with reduced mortality and relapse rate. However, there are still noticeable percentage of patients that may relapse despite application of modern treatment strategies including preemptive rituximab infusions. Hereby, we share our experience concerning a frequently relapsing iTTP due to development of anti-rituximab antibody. In our case administration of obinutuzumab, a humanized type II anti CD-20 antibody was associated with complete peripheral blood B cell depletion and increasing plasma ADAMTS-13 activity.

Primary antiphospholipid syndrome associated with anti-phospholipase A2 receptor antibody-positive membranous nephropathy.

BACKGROUND: The kidney is a major target in primary antiphospholipid syndrome. Several types of nephropathy have been reported, the most frequent being acute or chronic specific vascular nephropathies and membranous nephropathy. CASE PRESENTATION: A 59-year-old male presented in our unit with nephrotic syndrome. He had a history of primary antiphospholipid syndrome with lupus anticoagulant treated with vitamin K antagonist therapy. On admission, antiphospholipid (lupus anticoagulant) and anti-PLA2R antibodies were positive. Screening for secondary etiologies was negative. In the context of primary antiphospholipid syndrome treated with vitamin K antagonist therapy, we did not perform a biopsy and we treated the patient with angiotensin-converting-enzyme inhibitor. No remission was observed at 6 months with persistent anti-PLA2R antibodies while antiphospholipid antibody level became negative. Consequently, kidney biopsy was performed showing both membranous nephropathy with PLA2R in deposits on immunohistochemistry with IgG4 dominance and antiphospholipid syndrome chronic vascular nephropathy. Following that, treatment with rituximab was started with secondarily a decrease in serum PLA2R antibody levels and partial remission. CONCLUSION: We report the first association between primary antiphospholipid syndrome and membranous nephropathy with anti-PLA2R antibodies. Our observations could suggest a causal link between primary antiphospholipid syndrome and PLA2R-related membranous nephropathy. Consequently, it would be interesting to screen for anti-PLA2R antibodies for further cases of nephrotic syndrome in patients with primary antiphospholipid syndrome and to search antiphospholipid antibodies in all membranous nephropathies.

Galectin 3 Deficiency Alters Chondrocyte Primary Cilium Formation and Exacerbates Cartilage Destruction via Mitochondrial Apoptosis.

Mechanical overload and aging are the main risk factors of osteoarthritis (OA). Galectin 3 (GAL3) is important in the formation of primary cilia, organelles that are able to sense mechanical stress. The objectives were to evaluate the role of GAL3 in chondrocyte primary cilium formation and in OA in mice. Chondrocyte primary cilium was detected in vitro by confocal microscopy. OA was induced by aging and partial meniscectomy of wild-type (WT) and Gal3-null 129SvEV mice (Gal3-/-). Primary chondrocytes were isolated from joints of new-born mice. Chondrocyte apoptosis was assessed by Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL), caspase 3 activity and cytochrome c release. Gene expression was assessed by qRT-PCR. GAL3 was localized at the basal body of the chondrocyte primary cilium. Primary cilia of Gal3-/- chondrocytes were frequently abnormal and misshapen. Deletion of Gal3 triggered premature OA during aging and exacerbated joint instability-induced OA. In both aging and surgery-induced OA cartilage, levels of chondrocyte catabolism and hypertrophy markers and apoptosis were more severe in Gal3-/- than WT samples. In vitro, Gal3 knockout favored chondrocyte apoptosis via the mitochondrial pathway. GAL3 is a key regulator of cartilage homeostasis and chondrocyte primary cilium formation in mice. Gal3 deletion promotes OA development.

Use of double filtration plasmapheresis for the treatment of acquired thrombocytopenic thrombotic purpura.

Double filtration plasmapheresis (DFPP) could be an alternative method to simple plasma exchange plasmapheresis in the treatment of acquired thrombotic thrombocytopenic purpura (aTTP). In a retrospective single center case series, we studied clinical presentation, management care, and prognosis of aTTP patients from our academic center treated with DFPP and IV infusion of fresh frozen plasma (FFP) between 2009 and 2018. Nine patients were included for 11 episodes. Median age was 38 years old (IQR 26-53) with 78% women. Six episodes (55%) required admission to the ICU, four of which required mechanical ventilation. Median FFP volume transfused was 35.2 mL/kg/d of session. Response was complete for nine episodes (82%). Four patients presented an early relapse, two a late relapse. Four patients died: one had an active untreated HCV infection, and two were over 80-year-old polymorbid patients. DFPP seems to be an efficient method of therapeutic plasmapheresis in TTP when combined with FFP transfusion and immunosuppressive treatments.

Metformin-related lactic acidosis with acute kidney injury: results of a French observational multicenter study.

Background: Metformin-associated lactic acidosis (MALA) and metformin-induced lactic acidosis (MILA) remain controversial entities. Metformin toxic effect depends on accumulation to lead to lactic acidosis (LA), particularly during an episode of acute kidney injury (AKI). In MILA, no other condition contributing to LA is found. The aims of this study were to describe the characteristics and prognosis of AKI associated with LA in metformin users and to clarify the role of this drug in the different types of LA.Methods: We performed a French multicenter retrospective study in diabetic patients treated by metformin presenting with LA in a context of AKI in 2015. 126 nephrology units (NU) and 23 intensive care units (ICU) were contacted. We individualized MILA and MALA patients in order to illustrate the role of metformin.Results: We included 173 patients (109 MILA, 64 MALA). 103 patients presented without hemodynamic instability (82 MILA and 21 MALA) whereas 70 patients were shocked including 27 MILA. The shock was associated with death with an odds ratio (OR) of 12.92 (p < .001). Digestive disorders (DD) were strongly associated with MILA (p = .0001). MALA was significantly associated with shock (p < .0001). The mortality rate was higher in MALA (26%) when compared with MILA (7%). Dialysis performed in 133 patients was significantly associated with shock, kalemia, lactate and serum creatinine levels. In multivariate analysis, metformin level was independently associated with pH or lactate level only in MILA patients.Conclusions: MILA is associated with DD and death is due to severe refractory acidosis leading to cardiovascular collapse attributed to metformin accumulation mainly via AKI. MALA patients are more frequently shocked and death is related to their underlying condition, metformin accumulation increasing LA.

Heterogeneity of Cause, Care, and Prognosis in Severe Acute Kidney Injury in Hospitalized Patients: A Prospective Observational Study.

BACKGROUND: KDIGO (Kidney Disease: Improving Global Outcomes) defines acute kidney injury (AKI) solely by serum creatinine (SCr) and urine output variation. Severe AKI is a syndrome covering various clinical situations. OBJECTIVE: To describe severe AKI heterogeneity by department of hospitalization. DESIGN: This is a prospective observational single-center study. SETTING: Adult patients hospitalized in a French tertiary hospital from August 2016 to December 2017. PATIENTS: All adults with severe AKI, defined by dialysis for AKI or an increase in SCr above 354 µmol/L. MEASUREMENTS: Patient characteristics, clinical and laboratory presentation, AKI cause, medical indication for renal replacement therapy (RRT), planned palliative care, and vital status 30 days after severe AKI. METHODS: A global description of patient characteristics, care, and prognosis and comparison by department of hospitalization: intensive care unit (ICU), nephrology, and others. RESULTS: The study included 480 patients (73% men, median age: 72 years, range: 64-83), with medical histories including cardiovascular disease, diabetes, cancer, and chronic kidney disease. Principal causes were sepsis (104; 22%), hypovolemia (98; 20%), obstructive AKI (84; 18%), acute tubular necrosis (ATN; 74; 15%), and cardiorenal syndrome (51; 11%). Severe AKI was diagnosed in the ICU for 188 (39%) patients, the nephrology department for 130 (27%), and in other wards for 162 (34%). Patient characteristics differed by department for age, comorbidity, cause, and RRT use and indications. Palliative care was planned for 72 (15%) patients, most frequently in other wards. LIMITATIONS: We studied a subgroup of stage 3 KDIGO AKI patients in a single center without cardiac surgery. CONCLUSION: Patients hospitalized for severe AKI have frequent and various comorbidities, different clinical presentations, care, hospitalization in various departments, and different prognosis. The heterogeneity of this severe AKI implies the need for personalized care, which requires prognostic tools that include information besides SCr and diuresis.

CONTEXTE: Le KDIGO définit l'insuffisance rénale aigüe (IRA) uniquement par une variation de la créatinine sérique (SCr) et de la diurèse. L'IRA grave est un syndrome couvrant diverses situations cliniques. OBJECTIF: Décrire l'hétérogénéité de l'IRA grave selon l'unité d'hospitalisation. TYPE D'ÉTUDE: Étude observationnelle prospective menée dans un seul centre. SUJETS: Des adultes hospitalisés entre août 2016 et décembre 2017 dans un centre de soins tertiaires en France. PARTICIPANTS: Tous les adultes atteints d'IRA grave, définie par un traitement de dialyse ou un taux de SCr au-delà de 354 µmol/l. MESURES: Les caractéristiques du patient, le tableau clinique et de laboratoire, l'étiologie de l'IRA, l'indication médicale pour une thérapie de remplacement rénal (TRR), le plan de soins palliatifs et le statut vital 30 jours après l'épisode d'IRA grave. MÉTHODOLOGIE: Une description globale des caractéristiques des patients, des soins et du pronostic, ainsi qu'une comparaison selon l'unité d'hospitalisation: unité de soins intensifs (USI), néphrologie et autres. RÉSULTATS: L'étude portait sur 480 patients (73 % d'hommes) âgés de 64 à 83 ans (âge médian: 72 ans) avec des antécédents incluant maladies cardiovasculaires, diabète, cancer ou insuffisance rénale chronique. Les principales causes de l'IRA grave étaient une septicémie (104, 22 %), une hypovolémie (98, 20 %), une IRA obstructive (84, 18 %), une nécrose tubulaire aigüe (74, 15 %) ou un syndrome cardio-rénal (51, 11 %). Le diagnostic avait été posé à l'USI pour 188 patients (39 %), en néphrologie pour 130 patients (27 %) et dans d'autres unités pour 162 patients (34 %). Les caractéristiques des patients différaient entre les unités de soins en ce qui concerne l'âge, les comorbidités, l'étiologie et les indications de TRR. Un plan de soins palliatifs existait pour 72 patients (15 %), le plus souvent dans les autres unités. LIMITES: Nous avons étudié un sous-groupe de patients atteints d'IRA de stade 3 (classification KDIGO) dans un seul centre sans chirurgie cardiaque. CONCLUSION: Les patients hospitalisés pour une IRA grave présentent des comorbidités, des tableaux cliniques, des soins et des pronostics variés et sont admis dans différentes unités d'hospitalisation. Cette hétérogénéité de l'IRA grave met en relief le besoin de soins personnalisés qui nécessitent des outils pronostics basés sur des informations autres que la SCr et la diurèse.

CRDSAT Generated by pCARGHO: A New Efficient Lectin-Based Affinity Tag Method for Safe, Simple, and Low-Cost Protein Purification.

Purification of recombinant proteins remains a bottleneck for downstream processing. The authors engineered a new galectin 3 truncated form (CRDSAT ), functionally and structurally characterized, with preserved solubility and lectinic activity. Taking advantage of these properties, the authors designed an expression vector (pCARGHO), suitable for CRDSAT -tagged protein expression in prokaryotes. CRDSAT binds to lactose-Sepharose with a high specificity and facilitates solubilization of fusion proteins. This tag is structurally stable and can be easily removed from fusion proteins using TEV protease. Furthermore, due to their basic isoelectric point (pI), CRDSAT , and TEV are efficiently eliminated using cationic exchange chromatography. When pI of the protein of interest (POI) and CRDSAT are close, other chromatographic methods are successfully tested. Using CRDSAT tag, the authors purified several proteins from prokaryote and eukaryote origin and demonstrated as examples, the preservation of both Escherichia coli Thioredoxin 1 and human CDC25Bcd activities. Overall, yields of proteins obtained after tag removal are about 5-50 mg per litre of bacterial culture. Our purification method displays various advantages described herein that may greatly interest academic laboratories, biotechnology, and pharmaceutical companies.

Galectin-3: A key player in arthritis.

Arthritis is more and more considered as the leading reason for the disability in the world, particularly regarding its main entities, rheumatoid arthritis and osteoarthritis. The common feature of arthritis is inflammation, which is mainly supported by synovitis (synovial inflammation), although the immune system plays a primary role in rheumatoid arthritis and a secondary one in osteoarthritis. During the inflammatory phase of arthritis, many pro-inflammatory cytokines and mediators are secreted by infiltrating immune and resident joint cells, which are responsible for cartilage degradation and excessive bone remodeling. Amongst them, a ß-galactoside-binding lectin, galectin-3, has been reported to be highly expressed and secreted by inflamed synovium of rheumatoid arthritis and osteoarthritis patients. Furthermore, galectin-3 has been demonstrated to induce joint swelling and osteoarthritis-like lesions after intra-articular injection in laboratory animals. However, the mechanisms underlying its pathophysiological role in arthritis have not been fully elucidated. This review deals with the characterization of arthritis features and galectin-3 and summarizes our current knowledge of the contribution of galectin-3 to joint tissue lesions in arthritis.

The infrapatellar fat pad induces inflammatory and degradative effects in articular cells but not through leptin or adiponectin.

OBJECTIVES: Based on a novel approach suggesting a role of adipose tissue in osteoarthritis (OA), we aimed to determine whether the infrapatellar fat pad (IFP) may affect joint cell functions through adipokines. METHODS: The conditioned media of IFP and subcutaneous adipose tissue from OA patients were used to determine the production of leptin and adiponectin, and to stimulate chondrocytes and fibroblast-like synoviocytes (FLS). Blocking experiments were carried out to evaluate the contribution of adipokines to IFP effects. The gene expression of inflammatory and degradative proteins, growth factors and components of the extracellular matrix, and the production of inflammatory mediators and metalloproteases were determined to evaluate cell response to fat-conditioned media. RESULTS: IFP releases elevated amounts of leptin and adiponectin independently of the body mass index and the gender. The conditioned media from IFP strongly induce the expression of inflammatory genes in both articular cells and the expression of degradative genes in chondrocytes, but remain ineffective in regulating the expression of aggrecan, type 2 collagen or growth factors. Blocking leptin or adiponectin does not change the cell response to IFP. A great variability between patients is found when compared the inflammatory activity of paired samples of IFP and subcutaneous adipose tissue. CONCLUSIONS: IFP may trigger both cartilage destruction and inflammation of the synovium, but not through leptin or adiponectin. The data suggest also that IFP may have specific inflammatory phenotypic features independent from the general phenotype found in obesity.

Basic science of osteoarthritis.

Osteoarthritis (OA) is a prevalent, disabling disorder of the joints that affects a large population worldwide and for which there is no definitive cure. This review provides critical insights into the basic knowledge on OA that may lead to innovative end efficient new therapeutic regimens. While degradation of the articular cartilage is the hallmark of OA, with altered interactions between chondrocytes and compounds of the extracellular matrix, the subchondral bone has been also described as a key component of the disease, involving specific pathomechanisms controlling its initiation and progression. The identification of such events (and thus of possible targets for therapy) has been made possible by the availability of a number of animal models that aim at reproducing the human pathology, in particular large models of high tibial osteotomy (HTO). From a therapeutic point of view, mesenchymal stem cells (MSCs) represent a promising option for the treatment of OA and may be used concomitantly with functional substitutes integrating scaffolds and drugs/growth factors in tissue engineering setups. Altogether, these advances in the fundamental and experimental knowledge on OA may allow for the generation of improved, adapted therapeutic regimens to treat human OA.

Identification of two populations of osteoarthritic osteoblasts according to the 1,25[OH]2 vitamin D3 potency to stimulate osteocalcin.

INTRODUCTION: Few studies have tried to discriminate a differential behavior between osteoarthritic (OA) osteoblasts (Obs). Based on osteocalcin level, we aimed, in the present study, to evaluate the capacity of OA Obs for producing molecules of the Wnt/ß-catenin signaling pathway. METHODS: Human primary OA Obs (n=11) were exposed or not to 50 nM of 1,25 dihydroxyvitamin D3 (VitD3) for 24 h. Osteocalcin (OCN), TGF-ß1, Dickkopf-related protein 2 (DKK2), R-spondin 2 (Rspo2), Wnt5b, and low density lipoprotein related-receptor 1 (LRP1) were evaluated by real time RT-PCR. RESULTS: All samples responded to VitD3 as validated by the increase in OCN expression. However two populations of Obs were discriminated; one called "high responders" whose OCN stimulation was higher than 100 fold (mean 881 fold, p<0.01, n=5) and the second one whose stimulation was inferior to 100 fold (mean 47 fold, p<0.01, n=6), namely "low responders". In fact, high responders have a weaker basal expression of OCN. With regards to these two cell populations and in absence of VitD3 challenge, the expression level of TGF-ß1 (15 fold, p<0.001), DKK2 (2.5 fold, p<0.002) and Wnt5b (5.5 fold, p<0.003) was higher in "high responders", meanwhile Rspo2 and LRP1 expression was unchanged. VitD3 exacerbated this pattern but corrected OCN expression and favored Wnt agonist expression. CONCLUSION: We identified 2 populations of OA Obs according to the OCN expression under the control of VitD3. In addition under basal conditions, these 2 populations expressed differently TGF-ß1, Wnt5b, DKK2, suggesting a heterogeneous differentiation and phenotype in Obs among OA patients.

Hypoxia and vitamin D differently contribute to leptin and dickkopf-related protein 2 production in human osteoarthritic subchondral bone osteoblasts.

INTRODUCTION: Bone remodelling and increased subchondral densification are important in osteoarthritis (OA). Modifications of bone vascularisation parameters, which lead to ischemic episodes associated with hypoxic conditions, have been suspected in OA. Among several factors potentially involved, leptin and dickkopf-related protein 2 (DKK2) are good candidates since they are up-regulated in OA osteoblasts (Obs). Therefore, in the present study, we investigated the hypothesis that hypoxia may drive the expression of leptin and DKK2 in OA Obs. METHODS: Obs from the sclerotic portion of OA tibial plateaus were cultured either under 20% or 2% oxygen tension in the presence or not of 50 nM of 1,25-dihydroxyvitamin D3 (VitD3). The expression of leptin, osteocalcin, DKK2, hypoxia-inducible factors (Hif)-1α and -2α was measured by real-time polymerase chain reaction and leptin production by enzyme-linked immunosorbent assay (ELISA). The expression of Hif-1α, Hif-2α, leptin and DKK2 was reduced using silencing (si) RNA technique. Signalling pathway of hypoxia-induced leptin was investigated by western blotting and mitogen-activated protein kinase (MAPK) inhibitors. RESULTS: As expected, hypoxia stimulated the expression of Hif-1 and Hif-2. The expression of leptin and DKK2 in Obs was also stimulated 7-fold and 1.8-fold respectively (p<0.05) under hypoxia. Interestingly, whereas VitD3 stimulated leptin and DKK2 expression 2- and 4.2-fold under normoxia, it further stimulated it to 28- and 6.2-fold under hypoxia (p<0.05). The hypoxia-induced leptin production was confirmed by ELISA, particularly in presence of VitD3 (p<0.02). Compared to Obs incubated in the presence of siScramble RNAs, siHif-2α inhibited VitD3-stimulated leptin mRNA and protein levels by 70% (p=0.004) and 60% (p<0.02), respectively while it failed to significantly alter the expression of DKK2. SiHif-1α has no effect on these genes. Immunoblotting showed that VitD3 greatly stabilized Hif-2α under hypoxic condition. The increase in leptin expression under hypoxia was also regulated, in addition to the role of Hif-2α, by p38 MAPK (p<0.03) and PI 3-kinase (p<0.05). Finally, we demonstrated that the expression of leptin and DKK2 were not related to each other under hypoxia. CONCLUSIONS: Hypoxic conditions via Hif-2 regulation trigger Obs to produce leptin particularly under VitD3 stimulation whereas DKK2 is mainly regulated by VitD3 rather than hypoxia.