Mutation in the CCAL1 locus accounts for bidirectional process of human subchondral bone turnover and cartilage mineralization.

OBJECTIVES: To study the mechanism by which the readthrough mutation in TNFRSF11B, encoding osteoprotegerin (OPG) with additional 19 amino acids at its C-terminus (OPG-XL), causes the characteristic bidirectional phenotype of subchondral bone turnover accompanied by cartilage mineralization in chondrocalcinosis patients. METHODS: OPG-XL was studied by human induced pluripotent stem cells expressing OPG-XL and two isogenic CRISPR/Cas9-corrected controls in cartilage and bone organoids. Osteoclastogenesis was studied with monocytes from OPG-XL carriers and matched healthy controls followed by gene expression characterization. Dual energy X-ray absorptiometry scans and MRI analyses were used to characterize the phenotype of carriers and non-carriers of the mutation. RESULTS: Human OPG-XL carriers relative to sex- and age-matched controls showed, after an initial delay, large active osteoclasts with high number of nuclei. By employing hiPSCs expressing OPG-XL and isogenic CRISPR/Cas9-corrected controls to established cartilage and bone organoids, we demonstrated that expression of OPG-XL resulted in excessive fibrosis in cartilage and high mineralization in bone accompanied by marked downregulation of MGP, encoding matrix Gla protein, and upregulation of DIO2, encoding type 2 deiodinase, gene expression, respectively. CONCLUSIONS: The readthrough mutation at CCAL1 locus in TNFRSF11B identifies an unknown role for OPG-XL in subchondral bone turnover and cartilage mineralization in humans via DIO2 and MGP functions. Previously, OPG-XL was shown to affect binding between RANKL and heparan sulphate (HS) resulting in loss of immobilized OPG-XL. Therefore, effects may be triggered by deficiency in the immobilization of OPG-XL Since the characteristic bidirectional pathophysiology of articular cartilage calcification accompanied by low subchondral bone mineralization is also a hallmark of OA pathophysiology, our results are likely extrapolated to common arthropathies.

Acute Calcium Pyrophosphate Crystal Arthritis of the Wrist Elicited by Anti-COVID-19 Vaccination After Carpal Tunnel Release.

BACKGROUND Calcium pyrophosphate dihydrate deposition disease includes a variety of clinical syndromes, including acute calcium pyrophosphate (CPP) crystal arthritis. Most patients with CPP crystal arthritis have a primary/idiopathic form presenting with severe pain, swelling, and stiffness. COVID-19 infection, which originated in China in December 2019, required extraordinary efforts to develop and test new vaccines to halt the pandemic. The Vaxzervria vaccine has shown excellent safety and efficacy in phase 3 trials with a mechanism based on the expression of the SARS-CoV-2 spike protein gene coding for the S-antigen, which stimulates the immune response. CASE REPORT We describe an acute event of crystal arthritis after a carpal tunnel syndrome release followed by administration of the second dose of anti-COVID-19 Vaccine Oxford-AstraZeneca (ChAdOx1 nCoV-19). Medical treatment resulted in full resolution of the symptoms in 2 weeks. CONCLUSIONS Although most episodes of acute arthritis happen spontaneously, certain factors may trigger the acute CPP crystal arthritis such as intercurrent illnesses or surgeries. Although the association between carpal tunnel syndrome and CPP arthritis has been known for over 40 years, surgical release of the carpal ligament has always been associated with full resolution of symptoms. This is the first case report describing an exacerbation after carpal canal release, concomitant with the administration of the vaccine. According to our opinion, the vaccination associated with a prior surgery in the same anatomical site could have synergically triggered the arthritis flare-up, in a predisposed patient, with a mechanism still unknown.

A case of acute calcium pyrophosphate arthritis in two rare sites of involvement: The cervical facet and atlantoaxial joint.

Calcium pyrophosphate dihydrate deposition (CPPD) disease, also known as pseudogout, in which crystals are deposited in the joints and/or soft tissues, leads to a variety of articular and periarticular disorders. Herein we report a 67-year-old female patient with neck pain who was diagnosed as CPPD disease of both the atlantoaxial joint and right C4-C5 facet joint with radiological findings. The combined use of computed tomography and magnetic resonance imaging can be helpful in establishing a diagnosis and providing the correct treatment.

Differences in intracellular localisation of ANKH mutants that relate to mechanisms of calcium pyrophosphate deposition disease and craniometaphyseal dysplasia.

ANKH mutations are associated with calcium pyrophosphate deposition disease and craniometaphyseal dysplasia. This study investigated the effects of these ANKH mutants on cellular localisation and associated biochemistry. We generated four ANKH overexpression-plasmids containing either calcium pyrophosphate deposition disease or craniometaphyseal dysplasia linked mutations: P5L, E490del and S375del, G389R. They were transfected into CH-8 articular chondrocytes and HEK293 cells. The ANKH mutants dynamic differential localisations were imaged and we investigated the interactions with the autophagy marker LC3. Extracellular inorganic pyrophosphate, mineralization, ENPP1 activity expression of ENPP1, TNAP and PIT-1 were measured. P5L delayed cell membrane localisation but once recruited into the membrane it increased extracellular inorganic pyrophosphate, mineralization, and ENPP1 activity. E490del remained mostly cytoplasmic, forming punctate co-localisations with LC3, increased mineralization, ENPP1 and ENPP1 activity with an initial but unsustained increase in TNAP and PIT-1. S375del trended to decrease extracellular inorganic pyrophosphate, increase mineralization. G389R delayed cell membrane localisation, trended to decrease extracellular inorganic pyrophosphate, increased mineralization and co-localised with LC3. Our results demonstrate a link between pathological localisation of ANKH mutants with different degrees in mineralization. Furthermore, mutant ANKH functions are related to synthesis of defective proteins, inorganic pyrophosphate transport, ENPP1 activity and expression of ENPP1, TNAP and PIT-1.

Recurrent pseudogout after therapy with immune checkpoint inhibitors: a case report with immunoprofiling of synovial fluid at each flare.

BACKGROUND: Despite ground-breaking clinical success in the treatment of different cancers, immune checkpoint inhibitors can cause profound inflammatory and immune-related adverse events. Autoimmune inflammatory arthritis following immune checkpoint inhibitor treatment has been reported; however, to date, no cases of crystal arthritis following immune checkpoint inhibitors have been identified. CASE PRESENTATION: We report the first case of recurrent pseudogout, an inflammatory crystal arthritis, in a patient treated with nivolumab, a PD-1 inhibitor, for renal cell carcinoma. The patient had recurrent pseudogout flares about week to 10 days after each nivolumab infusion. After treatment with prophylactic colchicine, the patient well tolerated additional nivolumab infusions without adverse events. In parallel, we characterized immune cells of synovial fluid at each flare. Immunoprofiling of synovial fluid showed that the proportion of inflammatory IL-17-producing CD4+ T cells and amount of IL-17 were notably increased in synovial fluid with every recurrent flair, and correlated with the increase in number of synovial neutrophils, suggesting a potential role of T helper 17 (Th17) cells in neutrophil-driven inflammation during pseudogout arthritis. CONCLUSIONS: This case suggests a potential influence of Th17 cells on the neutrophil recruitment and neutrophil-driven inflammatory events leading to pseudogout induced by immune checkpoint inhibitor therapy.

[A muscular calcium pyrophosphate deposition pseudo-abscess: An atypical localization of chondrocalcinosis]. / Pseudo-abcès musculaire d'origine microcristalline : une localisation exceptionnelle de chondrocalcinose.

INTRODUCTION: Chondrocalcinosis results from calcium pyrophosphate crystals deposition in the joints. We report an exceptional case of aseptic psoas abscess with a deposition of calcium pyrophosphate crystals. CASE REPORT: A 92-year-old man presented to our department for an acute onset of inflammatory pain in the left hip. Computed tomography detected a coxofemoral arthritis and multiple intramuscular collections located in the iliopsoas muscle and the gluteus minimus. A sample of the fluid was obtained with a guided aspiration, and its analysis revealed an inflammatory liquid with no bacteria but numerous calcium pyrophosphate crystals. The final diagnosis was thus a muscular calcium pyrophosphate deposition pseudo-abscess, associated with a hip arthritis. CONCLUSION: Hip chondrocalcinosis is unusual, and the association with intramuscular deposition of calcium pyrophosphate crystals seems extremely rare as we found only four other published cases. A microcrystalline arthritis could have spread from the coxofemoral joint through the iliopsoas bursa and into the muscle. However, the imaging aspect with an abscess and a predominant muscular injury might suggest a mechanism of crystal formation originating directly within the muscle. The outcome was always favourable even if some patients required surgery.

Inhibition of nucleotide pyrophosphatase/phosphodiesterase 1: implications for developing a calcium pyrophosphate deposition disease modifying drug.

Objectives: Calcium pyrophosphate deposition (CPPD) is associated with osteoarthritis and is the cause of a common inflammatory articular disease. Ecto-nucleotide pyrophosphatase/phosphodiesterase 1 (eNPP1) is the major ecto-pyrophosphatase in chondrocytes and cartilage-derived matrix vesicles (MVs). Thus, eNPP1 is a principle contributor to extracellular pyrophosphate levels and a potential target for interventions aimed at preventing CPPD. Recently, we synthesized and described a novel eNPP1-specific inhibitor, SK4A, and we set out to evaluate whether this inhibitor attenuates nucleotide pyrophosphatase activity in human OA cartilage. Methods: Cartilage tissue, chondrocytes and cartilage-derived MVs were obtained from donors with OA undergoing arthroplasty. The effect of SK4A on cell viability was assayed by the XTT method. eNPP1 expression was evaluated by western blot. Nucleotide pyrophosphatase activity was measured by a colorimetric assay and by HPLC analysis of adenosine triphosphate (ATP) levels. ATP-induced calcium deposition in cultured chondrocytes was visualized and quantified with Alizarin red S staining. Results: OA chondrocytes expressed eNPP1 in early passages, but this expression was subsequently lost upon further passaging. Similarly, significant nucleotide pyrophosphatase activity was only detected in early-passage chondrocytes. The eNPP1 inhibitor, SK4A, was not toxic to chondrocytes and stable in culture medium and human plasma. SK4A effectively inhibited nucleotide pyrophosphatase activity in whole cartilage tissue, in chondrocytes and in cartilage-derived MVs and reduced ATP-induced CPPD. Conclusion: Nucleotide analogues such as SK4A may be developed as potent and specific inhibitors of eNPP1 for the purpose of lowering extracellular pyrophosphate levels in human cartilage with the aim of preventing and treating CPPD disease.

The role of ANKH in pathologic mineralization of cartilage.

PURPOSE OF REVIEW: ANKH is the human homolog of a gene whose dysfunction in a mutant mouse strain results in progressive ankylosis of the spine as well as soft tissue mineralization. ANKH mutations have been reported in inherited human disorders such as familial calcium pyrophosphate deposition disease (CPPD) and cranial metaphyseal dysplasia; however, research into the function of the ANKH protein has been more challenging. Progress has recently been made to understand the role of ANKH in the regulation of physiological and pathological mineralization. RECENT FINDINGS: ANKH expression is regulated by intracellular levels of oxygen, phosphate and calcium as well as by the growth factor TGF-ß. In addition, ANKH expression affects chondrogenesis, osteoblastogenesis and osteoclastogenesis. ANKH appears to interact with several cellular proteins, including the phosphate transporter PiT-1, and with proteins involved in NF-kappa ß signaling, suggesting that ANKH may play an important non-PPi transporter role. ANKH has also been shown to regulate ATP efflux from chondrocytes. SUMMARY: ANKH expression, as well as its potential non-PPi transporter functions, plays a variety of roles in the regulation of cellular events that surround differentiation and mineralization in bone and cartilage. Additional studies are warranted to further elucidate the contributions of ANKH to human health and disease, and to determine if ANKH deserves targeting for the treatment of diseases such as CPPD.

Senescence marker killer cell lectin-like receptor G1 (KLRG1) contributes to TNF-α production by interaction with its soluble E-cadherin ligand in chronically inflamed joints.

OBJECTIVES: Killer cell lectin-like receptor G1 (KLRG1) is an NK cell marker also expressed on T cells showing an immunosenescent phenotype. KLRG1 binding to its ligand E-cadherin inhibits functional responses. It was recently shown that soluble E-cadherin (sE-cadherin) also influences KLRG1 signalling, although its involvement in arthritis is unknown. Our goal was to evaluate the contribution of KLRG1(+) T cells to synovitis. METHODS: Paired peripheral blood (PB) and synovial fluid (SF) mononuclear cells from 21 patients with spondyloarthritis (SpA) or rheumatoid arthritis (RA), eight with crystal-induced arthritis and 10 controls were obtained. T cells were characterised for KLRG1 expression directly ex vivo, while TNF-α/IFN-γ production was assessed after polyclonal stimulation. Assays of chemotaxis response towards SF were conducted. Additionally, sE-cadherin levels in our paired samples were determined. Moreover, TNF-α/IFN-γ production by antigen-specific T cells was evaluated in the presence of sE-cadherin. RESULTS: KLRG1(+) T cells were enriched in SF as opposed to PB of SpA and RA patients, which contrasts with results obtained in crystal-induced arthritides. KLRG1(+) T cells were more functionally active as opposed to KLRG1(-) T cells and migrated preferentially towards SpA and RA SF. sE-cadherin levels were higher in SF versus plasma. The presence of sE-cadherin enhanced the number of KLRG1(+) CD4(+) T cells able to produce TNF-α but not IFN-γ. CONCLUSIONS: sE-cadherin contributes to the local proinflammatory environment in the joint by favouring TNF-α production by KLRG1(+) CD4(+) T cells. This pathway seems to be operational in both SpA and RA, but not in crystal-induced arthritis.

Characterization of nitrotyrosine as a biomarker for arthritis and joint injury.

OBJECTIVES: To characterize the utility of nitrotyrosine (NT) as a biomarker for arthritis and joint injury. DESIGN: Synovial fluid, plasma, and urine from patients diagnosed with osteoarthritis (OA), rheumatoid arthritis (RA), anterior cruciate ligament (ACL) injury, meniscus injury and pseudogout, and knee-healthy volunteers were analyzed for concentrations of NT, nitrate and nitrite (NO(x)), matrix metalloproteinase (MMP)-3, MMP-1, MMP-9, more than 40 chemokines and cytokines. RESULTS: In OA, plasma and synovial fluid NT were increased versus healthy volunteers. Synovial fluid to plasma NT ratios were elevated in OA patients. Synovial fluid from patients with ACL and meniscus injury and pseudogout had increased levels of NT (P < 0.001). In these samples, NT levels significantly correlated with ARGS-aggrecan neoepitope generated by aggrecanase cleavage of aggrecan (P ≤ 0.001), cross-linked C-telopeptides of type II collagen (P < 0.001), MMP-1 (P = 0.008), and MMP-3 (P ≤ 0.001). In RA, plasma NT decreased following 6 months of anti-tumor necrosis factor (TNF) treatment. For every 1.1% change in log(10) NT, there was a 1.0% change in the log(10) disease activity scores (DAS28-3 CRP). Both predicted and observed DAS28-3 CRP showed a robust linear relationship with NT. RA plasma NT positively correlated with CRP, MMP-3 and interferon γ-induced protein 10. CONCLUSIONS: NT may serve as a useful biomarker for arthritis and joint injury. In RA, NT is highly correlated with several biomarkers and clinical correlates of disease activity and responds to anti-TNF therapy.

Rheumatoid and pyrophosphate arthritis synovial fibroblasts induce osteoclastogenesis independently of RANKL, TNF and IL-6.

Bone destruction is a common feature of inflammatory arthritis and is mediated by osteoclasts, the only specialized cells to carry out bone resorption. Aberrant expression of receptor activator of nuclear factor kappa ß ligand (RANKL), an inducer of osteoclast differentiation has been linked with bone pathology and the synovial fibroblast in rheumatoid arthritis (RA). In this manuscript, we challenge the current concept that an increase in RANKL expression governs osteoclastogenesis and bone destruction in autoimmune arthritis. We isolated human fibroblasts from RA, pyrophosphate arthropathy (PPA) and osteoarthritis (OA) patients and analyzed their RANKL/OPG expression profile and the capacity of their secreted factors to induce osteoclastogenesis. We determined a 10-fold increase of RANKL mRNA and protein in fibroblasts isolated from RA relative to PPA and OA patients. Peripheral blood mononuclear cells (PBMC) from healthy volunteers were cultured in the presence of RA, PPA and OA synovial fibroblast conditioned medium. Osteoclast differentiation was assessed by expression of tartrate-resistant acid phosphatase (TRAP), vitronectin receptor (VNR), F-actin ring formation and bone resorption assays. The formation of TRAP(+), VNR(+) multinucleated cells, capable of F-actin ring formation and lacunar resorption in synovial fibroblast conditioned medium cultures occured in the presence of osteoprotegerin (OPG) a RANKL antagonist. Osteoclasts did not form in these cultures in the absence of macrophage colony stimulating factor (M-CSF). Our data suggest that the conditioned medium of pure synovial fibroblast cultures contain inflammatory mediators that can induce osteoclast formation in human PBMC independently of RANKL. Moreover inhibition of the TNF or IL-6 pathway was not sufficient to abolish osteoclastogenic signals derived from arthritic synovial fibroblasts. Collectively, our data clearly show that alternate osteoclastogenic pathways exist in inflammatory arthritis and place the synovial fibroblast as a key regulatory cell in bone and joint destruction, which is a hallmark of autoimmune arthritis.

The mechanisms of inflammation in gout and pseudogout (CPP-induced arthritis).

Recent advances have stimulated new interest in the area of crystal arthritis, as microcrystals can be considered to be endogenous "danger signals" and are potent stimulators of immune as well as non-immune cells. The best known microcrystals include urate (MSU), and calcium pyrophosphate (CPP) crystals, associated with gout and pseudogout, respectively. Acute inflammation is the hallmark of the acute tissue reaction to crystals in both gout and pseudogout. The mechanisms leading to joint inflammation in these diseases involve first crystal formation and subsequent coating with serum proteins. Crystals can then interact with plasma cell membrane, either directly or via membrane receptors, leading to NLRP3 activation, proteolytic cleavage and maturation of pro-interleukin-1ß (pro-IL1ß) and secretion of mature IL1ß. Once released, this cytokine orchestrates a series of events leading to endothelial cell activation and neutrophil recruitment. Ultimately, gout resolution involves several mechanisms including monocyte differentiation into macrophage, clearance of apoptotic neutrophils by macrophages, production of Transforming Growth Factor (TGF-ß) and modification of protein coating on the crystal surface. This review will examine these different steps.

Ankylosing spondylitis, late osteoarthritis, vascular calcification, chondrocalcinosis and pseudo gout: toward a possible drug therapy.

In this review we consider diseases associated with pathological mineralization/ossification, namely, ankylosing spondylitis (AS), osteoarthritis (OA), generalized artery calcification of infancy (GACI), vascular calcification as well as chondrocalcinosis (CC) and pseudo gout. Deciphering the key enzymes implicated in the calcification process is an objective of prime importance and the ultimate goal is to synthesize inhibitors of these enzymes in order to provide efficient alternate therapeutic strategies that will slow down the pathologic mineralization and complement the arsenal of anti-inflammatory drugs. One of the difficulties in the definition of diseases associated with pathologic mineralization/ossification lies in the controversial relationship between the type of calcification and the nature of the disease. Here, we propose to clarify this relationship by making a distinction between diseases associated with hydroxyapatite (HA) and calcium pyrophosphate dihydrate (CPPD) deposits. AS, OA, GACI and vascular calcification are usually characterized by mineralization/ossification associated with HA deposits, while CC and pseudo gout are mostly characterized by CPPD deposits. Although both HA and CPPD deposits may occur concomitantly, as in chronic pyrophosphate arthritis or in OA with CPPD, they are formed as a result of two antagonistic processes indicating that treatment of distinct diseases can be only achieved by disease-specific drug therapies. The hydrolysis of PPi, an inhibitor of HA formation, is mostly controlled by tissue non-specific alkaline phosphatase TNAP, while PPi production in the extracellular medium is controlled by ANK, a PPi transporter, and/or NPP1 which generates PPi from nucleotide triphosphates. Low PPi concentration may lead to a preferential deposition of HA while high PPi concentration will favor the formation of CPPD deposits. Thus, HA and CCPD deposition cannot occur concomitantly because they are determined by the Pi/PPi ratio which, in turn, depends on the relative activities of antagonistic enzymes, TNAP hydrolyzing PPi or ANK and NPP1 producing PPi. TNAP inhibitors could prevent HA formation in AS, in late OA, in GACI, as well as in vascular calcifications, while ANK or NPP1 inhibitors could slow down CCPD deposition in CC and pseudo gout.

Calcium deposition in osteoarthritic meniscus and meniscal cell culture.

INTRODUCTION: Calcium crystals exist in the knee joint fluid of up to 65% of osteoarthritis (OA) patients and the presence of these calcium crystals correlates with the radiographic evidence of hyaline cartilaginous degeneration. This study sought to examine calcium deposition in OA meniscus and to investigate OA meniscal cell-mediated calcium deposition. The hypothesis was that OA meniscal cells may play a role in pathological meniscal calcification. METHODS: Studies were approved by our human subjects Institutional Review Board. Menisci were collected during joint replacement surgeries for OA patients and during limb amputation surgeries for osteosarcoma patients. Calcium deposits in menisci were examined by alizarin red staining. Expression of genes involved in biomineralization in OA meniscal cells was examined by microarray and real-time RT-PCR. Cell-mediated calcium deposition in monolayer culture of meniscal cells was examined using an ATP-induced (45)calcium deposition assay. RESULTS: Calcium depositions were detected in OA menisci but not in normal menisci. The expression of several genes involved in biomineralization including ENPP1 and ANKH was upregulated in OA meniscal cells. Consistently, ATP-induced calcium deposition in the monolayer culture of OA meniscal cells was much higher than that in the monolayer culture of control meniscal cells. CONCLUSIONS: Calcium deposition is common in OA menisci. OA meniscal cells calcify more readily than normal meniscal cells. Pathological meniscal calcification, which may alter the biomechanical properties of the knee meniscus, is potentially an important contributory factor to OA.

Tophaceous calcium pyrophosphate dihydrate deposition disease of the temporomandibular joint.

Tophaceous pseudogout is a rare manifestation of calcium pyrophosphate dihydrate (CPPD) deposition disease that particularly affects the temporomandibular joint (TMJ). We describe a case of tophaceous pseudogout and review the literature. Thirty-four cases of chronic CPPD deposition disease affecting the TMJ are described. Symptoms usually included pain and swelling. Most patients required surgery because of extensive crystal deposits, usually localized to the joint and adjacent structures but occasionally invasive. For many patients, malignancy was the preoperative diagnosis. Although patients with acute pseudogout of the TMJ may have involvement of other joints, tophaceous pseudogout was predominantly isolated to the TMJ.

Inorganic pyrophosphate generation by transforming growth factor-beta-1 is mainly dependent on ANK induction by Ras/Raf-1/extracellular signal-regulated kinase pathways in chondrocytes.

ANK is a multipass transmembrane protein transporter thought to play a role in the export of intracellular inorganic pyrophosphate and so to contribute to the pathophysiology of chondrocalcinosis. As transforming growth factor-beta-1 (TGF-beta1) was shown to favor calcium pyrophosphate dihydrate deposition, we investigated the contribution of ANK to the production of extracellular inorganic pyrophosphate (ePPi) by chondrocytes and the signaling pathways involved in the regulation of Ank expression by TGF-beta1. Chondrocytes were exposed to 10 ng/mL of TGF-beta1, and Ank expression was measured by quantitative polymerase chain reaction and Western blot. ePPi was quantified in cell supernatants. RNA silencing was used to define the respective roles of Ank and PC-1 in TGF-beta1-induced ePPi generation. Finally, selective kinase inhibitors and dominant-negative/overexpression plasmid strategies were used to explore the contribution of several signaling pathways to Ank induction by TGF-beta1. TGF-beta1 strongly increased Ank expression at the mRNA and protein levels, as well as ePPi production. Using small interfering RNA technology, we showed that Ank contributed approximately 60% and PC-1 nearly 20% to TGF-beta1-induced ePPi generation. Induction of Ank by TGF-beta1 required activation of the extracellular signal-regulated kinase (ERK) pathway but not of p38-mitogen-activated protein kinase or of protein kinase A. In line with the general protein kinase C (PKC) inhibitor calphostin C, Gö6976 (a Ca2+-dependent PKC inhibitor) diminished TGF-beta1-induced Ank expression by 60%, whereas a 10% inhibition was observed with rottlerin (a PKCdelta inhibitor). These data suggest a regulatory role for calcium in TGF-beta1-induced Ank expression. Finally, we demonstrated that the stimulatory effect of TGF-beta1 on Ank expression was inhibited by the suppression of the Ras/Raf-1 pathway, while being enhanced by their constitutive activation. Transient overexpression of Smad 7, an inhibitory Smad, failed to affect the inducing effect of TGF-beta1 on Ank mRNA level. These data show that TGF-beta1 increases ePPi levels, mainly by the induction of the Ank gene, which requires activation of Ras, Raf-1, ERK, and Ca2+-dependent PKC pathways in chondrocytes.

The crowned dens syndrome. Evaluation with CT imaging.

PURPOSE: The purpose of this study was to verify the value of computed tomography (CT) in the diagnosis of the "crowned dens" syndrome, not only in crystal deposition diseases, but also in other rheumatic or nonrheumatic conditions. MATERIALS AND METHODS: Thirty-eight patients (15 men and 23 women; mean age 55 years; age range 35-79) with neck pain were examined and divided into two groups: (1) patients already identified as rheumatic and referred for further investigation of the atlantoaxial region; (2) patients with symptoms confined to the cervical spine, with inconclusive radiographic findings. Unenhanced CT of the cervical spine (Tomoscan SR 7000 Philips, Eindhoven, Netherlands) was performed in all patients. There were 11 cases of rheumatoid arthritis (ten women and one man), two calcium pyrophosphate dihydrate crystal deposition disease (both women), one of systemic sclerosis (a woman), one of osteoarthritis (a man), one of seronegative arthritis (a man), four of neoplasm (one woman and three men) with suspected cervical involvement, one (a man) of haematological disease (lymphoma), one (a woman) of menopausal osteoporosis, ten (five men and five women) of recent or previous trauma with suspected involvement of the skull base and first cervical vertebrae and six of unknown painful cervical dysfunction (three men and three women). RESULTS: CT demonstrated calcific deposits around the dens in 12 patients (three men and nine women), in the transverse and alar ligaments, and in the anterior atlantooccipital membrane. CT revealed horseshoe- or crown-like calcification surrounding the odontoid process. In our series, other rheumatic diseases, especially rheumatoid arthritis, showed similar irregular calcifications of the atlantoaxial joint. Discussion. In calcium pyrophosphate dihydrate (CPPD) crystal deposition disease, the spine may be the only site of involvement, generally asymptomatic. Crystals located in the transverse ligament of the atlas give rise to the crowned dens syndrome, usually in patients affected by severe degenerative lesions of the atlantoaxial joint and peripheral chondrocalcinosis. Symptoms may be absent, or a neurological compressive syndrome may develop. Symptoms tend to worsen with age. The diagnosis is not always easy, as the symptoms are similar to those of other diseases, such as meningitis, cervicobrachial pain, occipitotemporal headache, calcific tendinitis of the longus colli muscle, spondylodiscitis and retropharyngeal abscess. CONCLUSION: CT is the gold standard in identifying crowned dens syndrome, as it is able to depict the shape and site of calcification and any bone erosions. Radiography of other joints (wrist, knee, pubic symphysis) may help to ascertain whether the disease is due to calcium pyrophosphate dihydrate or hydroxyapatite crystals, and is therefore recommended for routine patient management. Magnetic resonance imaging (MRI) is indicated for the study of neurological complications.