FDG-PET/CT findings in systemic mastocytosis: a French multicentre study.

INTRODUCTION: Mastocytosis is a clonal haematological disease characterized by uncontrolled proliferation and the activation of mast cells. The value of FDG-PET/CT (FDG-PET) in mastocytosis has yet to be determined. METHODS: We retrospectively identified patients with an established diagnosis of systemic mastocytosis (SM), according to the WHO criteria, who underwent PET using the French Reference Centre for Mastocytosis database. Semi-quantitative and visual analysis of FDG-PET was performed and compared to the clinico-biological data. RESULTS: Our cohort included 19 adult patients, median age 65 years [range 58-74], including three with smouldering SM (SSM), three with aggressive SM (ASM), 10 with an associated clonal haematological non-mast-cell lineage disease (SM-AHNMD), and three with mast cell sarcoma (MCS). FDG-PET was performed at the time of the SM diagnosis (15/19), to evaluate lymph node (LN) activity (3/19) or the efficacy of therapy (1/19). FDG uptake was observed in the bone marrow (BM) (9/19, 47%), LN (6/19, 32%), spleen (12/19, 63%), or liver (1/19, 5%). No significant FDG uptake was observed in the SSM and ASM patients. A pathological FDG uptake was observed in the BM of 6/10 patients with SM-AHNMD, appearing as diffuse and homogeneous, and in the LN of 5/10 patients. All 3 MCS patients showed intense and multifocal BM pathological uptake, mimicking metastasis. No correlation was found between the FDG-PET findings and serum tryptase levels, BM mast cell infiltration percentage, and CD30 and CD2 expression by mast cells. CONCLUSIONS: FDG uptake does not appear to be a sensitive marker of mast cell activation or proliferation because no significant FDG uptake was observed in most common forms of mastocytosis (notably purely aggressive SM). However, pathological FDG uptake was observed in the SM-AHNMD and in MCS cases, suggesting a role of FDG-PET in their early identification and as a tool of therapeutic assessment in this subgroup of patients.

The Vestibular System: A Newly Identified Regulator of Bone Homeostasis Acting Through the Sympathetic Nervous System.

The vestibular system is a small bilateral structure located in the inner ear, known as the organ of balance and spatial orientation. It senses head orientation and motion, as well as body motion in the three dimensions of our environment. It is also involved in non-motor functions such as postural control of blood pressure. These regulations are mediated via anatomical projections from vestibular nuclei to brainstem autonomic centers and are involved in the maintenance of cardiovascular function via sympathetic nerves. Age-associated dysfunction of the vestibular organ contributes to an increased incidence of falls, whereas muscle atrophy, reduced physical activity, cellular aging, and gonadal deficiency contribute to bone loss. Recent studies in rodents suggest that vestibular dysfunction might also alter bone remodeling and mass more directly, by affecting the outflow of sympathetic nervous signals to the skeleton and other tissues. This review will summarize the findings supporting the influence of vestibular signals on bone homeostasis, and the potential clinical relevance of these findings.

Heavy/light chain specific immunoglobulin ratios provides no additional information than serum proteins electrophoresis and immunofixation for the diagnosis and the follow-up of intact immunoglobulin multiple myeloma patients.

BACKGROUND: Serum protein electrophoresis (SPE) and immunofixation electrophoresis (IFE) are used for diagnosis and follow-up of patients with intact immunoglobulin multiple myeloma. However, the numerous limitations of these methods led to the development of a nephelometric immunoassay (Hevylite™) for the specific measurement of serum IgGκ, IgGλ, IgAκ and IgAλ concentrations. METHODS: In this study, we evaluated the correlation between this assay and SPE and IFE in 114 sera of 15 patients (12 IgG and 3 IgA patients) and its impact on the clinical care of patients, especially for diagnosis, for the evaluation of residual disease and for early detection of relapse. RESULTS: At inclusion and during follow-up, we found a good correlation between monoclonal immunoglobulin concentrations and SPE (R(2)=0.902 for IgA and R(2)=0.915 for IgG) and nephelometric quantification (R(2)=0.948 for IgA and R(2)=0.920 for IgG) for the evaluation of monoclonal and polyclonal immunoglobulins. Our results illustrate that the Hevylite™ test is less sensitive than the IFE for detection of residual disease: 5 patients who obtained very good partial response or complete response had normalization of the Hevylite™ ratio while IFE was still positive. A relapse had been detectable with the Hevylite™ ratio 1 to 2 months earlier than with SPE and IFE in 3 patients out of 15, but no recommendations for treating patients with only slight biological relapse are available. CONCLUSION: Our results demonstrate that heavy/light chain specific immunoglobulin ratios provides no additional information than serum proteins electrophoresis and immunofixation for the diagnosis and the follow-up of intact immunoglobulin multiple myeloma patients. We also studied the correlation between the concentration of total immunoglobulin measured by Hevylite™ (sum of Ig'κ + Ig'λ) and nephelometric measurement of total IgG or IgA. For this correlation analysis, all 114 sera were analyzed. The correlation coefficient was R(2) = 0.948 for IgA and R(2) = 0.920 for IgG.

Influence of vestibular input on spatial and nonspatial memory and on hippocampal NMDA receptors.

It has recently been shown that a lack of vestibular sensory information decreases spatial memory performance and induces biochemical changes in the hippocampus in rodents. After vestibular neurectomy, patients display spatial memory deficit and hippocampal atrophy. Our objectives were to explore: (a) spatial (Y maze, radial-arm maze), and non-spatial (object recognition) memory performance, (b) modulation of NMDA receptors within the hippocampus using radioligand binding, and (c) hippocampal atrophy, using MRI, in a rat model of bilateral labyrinthectomy realized in two operations. Chemical vestibular lesions (VLs) were induced in 24 animals by transtympanic injections of sodium arsanilate (30 mg/0.1 ml/ear), one side being lesioned 3 weeks after the other. The control group received transtympanic saline solution (0.1 ml/ear) (n = 24). Spatial memory performance (Y maze and radial maze) decreased after VL. Conversely, non-spatial memory performance (object recognition) was not affected by VL. No hippocampal atrophy was observed with MRI, but density of NMDA receptors were increased in the hippocampus after VL. These findings show that the lack of vestibular information induced specific deficits in spatial memory. Additionally, quantitative autoradiographic data suggest the involvement of the glutamatergic system in spatial memory processes related to vestibular information. When studying spatial memory performances in the presence of vestibular syndrome, two-step labyrinthectomy is a suitable procedure for distinguishing between the roles of the specific components of vestibular input loss and those of impaired locomotor activity.

Evaluation of the chemical model of vestibular lesions induced by arsanilate in rats.

Several animal models of vestibular deficits that mimic the human pathology phenotype have previously been developed to correlate the degree of vestibular injury to cognate vestibular deficits in a time-dependent manner. Sodium arsanilate is one of the most commonly used substances for chemical vestibular lesioning, but it is not well described in the literature. In the present study, we used histological and functional approaches to conduct a detailed exploration of the model of vestibular lesions induced by transtympanic injection of sodium arsanilate in rats. The arsanilate-induced damage was restricted to the vestibular sensory organs without affecting the external ear, the oropharynx, or Scarpa's ganglion. This finding strongly supports the absence of diffusion of arsanilate into the external ear or Eustachian tubes, or through the eighth cranial nerve sheath leading to the brainstem. One of the striking observations of the present study is the complete restructuring of the sensory epithelia into a non sensory epithelial monolayer observed at 3months after arsanilate application. This atrophy resembles the monolayer epithelia observed postmortem in the vestibular epithelia of patients with a history of lesioned vestibular deficits such as labyrinthectomy, antibiotic treatment, vestibular neuritis, or Ménière's disease. In cases of Ménière's disease, aminoglycosides, and platinum-based chemotherapy, vestibular hair cells are destroyed, regardless of the physiopathological process, as reproduced with the arsanilate model of vestibular lesion. These observations, together with those presented in this study of arsanilate vestibular toxicity, suggest that this atrophy process relies on a common mechanism of degeneration of the sensory epithelia.

[Erdheim-Chester disease: report of a case and literature review]. / Maladie d'Erdheim-Chester : à propos d'un cas et revue de la littérature.

The Erdheim-Chester disease is a rare non-Langerhans hystiocytose acquired in adults. It results from a xanthogranulomatous infiltration, consists of histioccytes foamy and is characterized by heterogeneous systemic manifestations. The most frequent clinical manifestations of the disease are the bone with a long bone uptake on bone scintigraphy99Tc (Dion et al., 2006) and urological damage with an array of pseudo retroperitoneal fibrosis. We report the case of a 64-year-old man in whom was founded in the course of acute obstructive renal disease with Erdheim-Chester pseudofibrose retroperitoneal.

Selective optogenetic stimulation of glutamatergic, but not GABAergic, vestibular nuclei neurons induces immediate and reversible postural imbalance in mice.

Glutamatergic and GABAergic neurons represent the neural components of the medial vestibular nuclei. We assessed the functional role of glutamatergic and GABAergic neuronal pathways arising from the vestibular nuclei (VN) in the maintenance of gait and balance by optogenetically stimulating the VN in VGluT2-cre and GAD2-cre mice. We demonstrate that glutamatergic, but not GABAergic VN neuronal subpopulation is responsible for immediate and strong posturo-locomotor deficits, comparable to unilateral vestibular deafferentation models. During optogenetic stimulation, the support surface dramatically increased in VNVGluT2+ mice, and rapidly fell back to baseline after stimulation, whilst it remained unchanged during similar stimulation of VNGAD2+ mice. This effect persisted when vestibular tactilo kinesthesic plantar inputs were removed. Posturo-locomotor alterations evoked in VNVGluT2+ animals were still present immediately after stimulation, while they disappeared 1 h later. Overall, these results indicate a fundamental role for VNVGluT2+ neurons in balance and posturo-locomotor functions, but not for VNGAD2+ neurons, in this specific context. This new optogenetic approach will be useful to characterize the role of the different VN neuronal populations involved in vestibular physiology and pathophysiology.

The ventrolateral surgical approach to labyrinthectomy in rats: anatomical description and clinical consequences.

UNLABELLED: Destruction of the inner ear in rats for medical research has been performed since 1936. Nevertheless, descriptions of the technique used and clinical analysis are poor and often involve coagulation of the stapedial artery. We suggest a description of a surgical ventrolateral approach to labyrinthectomy in rats, with preservation of the stapedial artery. METHODS: Twenty-five Wistar rats were operated on via a right ventrolateral approach to the bulla, followed by labyrinthectomy with preservation of the stapedial artery. Clinical observation and tests were carried out from the time of the surgery until day one. Twenty-four hours after the surgery on the right side, the same surgery was performed on the left side, followed by clinical observation. Twenty-five other rats were used as controls, with sham surgery. Histologic analysis of the vestibular nerve with silver staining was performed in six rats 3 or 7 days after the labyrinthectomy. RESULTS: The ventrolateral approach made it possible to reach the middle- and inner-ear with preservation of nervous and vascular elements such as the facial nerve and stapedial artery. Unilateral labyrinthectomy induced ocular skew deviation, head torsion and limb asymmetry. Dynamic signs were first rolling, then rotation, which increased considerably during tail suspension. Bilateral labyrinthectomy produces instability with major body oscillation. Animals show head and neck dorsiflexion with limb extension, sometimes followed by fast backward walking. CONCLUSION: The ventrolateral approach is an efficient technique for surgical labyrinthectomy with stapedial artery preservation. Clinical analysis shows a wide range of signs to evaluate the functional destruction of the vestibular organ.

Stimulation of the rat medullary raphe nuclei induces differential responses in respiratory muscle activity.

Neural control circuits that coordinate the motor activity of the diaphragm (DIA) and the geniohyoid muscle (GH) are potentially involved in pathological conditions such as various forms of sleep apnea. Here we investigated a differential role of the raphe magnus (RMg), pallidus (RPa) and the obscurus (ROb) nuclei in the neural control of DIA and GH muscle activity in rats under volatile anesthesia. In order to characterize a topographical organization of the raphe nuclei we analyzed changes in DIA and GH during high-frequency stimulation (HFS, 10-130 Hz, 60 micros pulse width, 40-160 microA, 30s). HFS of the RMg and the ROb induced apnea, in the latter case apnea was associated with massive tonic discharge in the GH. By contrast, HFS of the RPa induced tachypnea. At caudal stimulation sites the tachypnea was accompanied by tonic DIA activity and cessation of GH. These data suggest a differential distribution of inhibitory and excitatory drives of DIA and GH muscles within distinct raphe nuclei.

Sympathetic B antagonist prevents bone mineral density decrease induced by labyrinthectomy.

We previously showed that bilateral vestibular lesion in rats induces a bone loss in weight bearing bones. To determine whether this effect is mediated by the sympathetic nervous system (SNS), bone mineral density (BMD) was measured in 4 groups of 10 female Wistar rats: bilateral labyrinthectomy (Bilab), Bilab with propranolol treatment, sham operated with or withoutpropranolol. In untreated rats, 30 days after lesion Bilab animals showed a reduced BMD in distal femoral metaphysis comparatively to intact rats (p < 0.001). In treated rats, there was no difference in BMD 30 days after lesion. This protective effect of propranolol against bone loss suggests that the vestibular system influence on bone remodeling is mediated by SNS. If this hypothesis is correct, this could have important consequences in devising countermeasures to spaceflight induced bone loss.

New software dedicated to virtual mazes for human cognitive investigations.

BACKGROUND: Compared to previous neuropsychological investigations with standard paper-pen tests limited to test complex spatial learning and memory processes, 3-D virtual immersive technology might offer new tools for research purposes and for diagnosis in patients suffering from mild cognitive impairment or dementia. COMPARISON WITH EXISTING METHODS: Current software proposes a customizable VR environment combined with an analyser module based on regions of interest and some parameters of analysis or pre-calibrated VR mazes with raw data. NEW METHOD: We attempted to create the VRmaze software offering either turnkey mazes with automatic tracking and analysis, or more complex and specific virtual mazes for human brain-behavioural research adaptable to all desired settings and parameters of analysis. The software combines 3D pre-calibrated VR tests or free customizable VR tests with digitized neuropsychological 2D standard and validated tests or tasks. RESULTS: We have tested an ERAM, a MWM and a reverse T-maze on 44 healthy subjects, showing gender differences in terms of navigation strategy. We have observed that the choice of benchmarks, instructions, and experimental parameters influence the performances. CONCLUSION: VRmaze software offers a translational approach for research units that wish to combine animal models and patient evaluations as well as complex 3D tasks and standardized neuropsychological tests combined with an automatic analysis opening a large perspective in the neurosciences to investigate cognitive functions. A clinical module with preconfigured 2- and 3-D tasks should offer clinicians an easy way to evaluate their patients routinely.

The critical role of vestibular graviception during cognitive-motor development.

Earth's gravity acts both as a mechanical stimulus on the body and as a sensory stimulus to the vestibular organ, which is transmitted into the brain. The vestibular system has been recently highlighted as the cornerstone of the multisensory cortex and of the dorsal hippocampus related to spatial cognition. Consequently, we have hypothesized that the vestibular sensory perception of gravity by the otoliths might also play a crucial role during the first stages of development in both sensorimotor and cognitive functions and the construction and perception of the 'self' and related functions of orientation and navigation. We have investigated an original mouse model (Head Tilted mice, B6Ei.GL-Nox3het/J) suffering from a selective congenital absence of vestibular otolithic gravisensors. We report that mouse pups suffered from a delay in the acquisition of sensorimotor reflexes, spatial olfactory guidance, path integration, and ultrasonic communication, while maternal care remained normal. We demonstrate that development has a critical period dependent on the vestibular otolithic sensory perception of gravity, probably temporally between the somesthetic and visual critical periods. The symptoms expressed by the congenital otolithic-deficient mice are similar to validated mouse models of autism and highlight the significance of vestibular graviception in the pathophysiology of development.

Flow cytometry for receptor analysis from ex-vivo brain tissue in adult rat.

BACKGROUND: Flow cytometry allows single-cell analysis of peripheral biological samples and is useful in many fields of research and clinical applications, mainly in hematology, immunology, and oncology. In the neurosciences, the flow cytometry separation method was first applied to stem cell extraction from healthy or cerebral tumour tissue and was more recently tested in order to phenotype brain cells, hippocampal neurogenesis, and to detect prion proteins. However, it remains sparsely applied in quantifying membrane receptors in relation to synaptic plasticity. NEW METHOD: We aimed to optimize a flow cytometric procedure for receptor quantification in neurons and non-neurons. A neural dissociation process, myelin separation, fixation, and membrane permeability procedures were optimized to maximize cell survival and analysis in hippocampal tissue obtained from adult rodents. We then aimed to quantify membrane muscarinic acetylcholine receptors (mAChRs) in rats with and without bilateral vestibular loss (BVL). RESULTS: mAChR's were quantified for neuronal and non-neuronal cells in the hippocampus and striatum following BVL. At day 30 but not at day 7 following BVL, there was a significant increase (P ≤ 0.05) in the percentage of neurons expressing M2/4 mAChRs in both the hippocampus and the striatum. CONCLUSION: Here, we showed that flow cytometry appears to be a reliable method of membrane receptor quantification in ex-vivo brain tissue.

[Anti-HMG-CoA reductase necrotizing myopathy: A report of 4 cases]. / Myopathies nécrosantes à anti-HMG-CoA réductase : à propos de 4 observations.

INTRODUCTION: Anti-3-hydroxy-3-méthylglutaryl-coenzyme A reductase antibody-associated necrotizing autoimmune myopathy has been recently described (2011). This myopathy is distinct from statin toxic myopathy. Our objective is to report on the clinical and para-clinical characteristics of this myopathy and to show the difficulties of therapeutic care. CASE REPORTS: We describe 4 cases of patients followed-up in Brittany, France. All data have been analyzed retrospectively. The mean age of our patients was 59.5 years, with a sex ratio of 1. The clinical presentation was homogeneous, with a subacute painful proximal and symmetrical weakness, without extra-muscular involvement. Other presentations have been described (including pseudo-dystrophic presentation). All patients had a previous statin medication (mean duration of 3.75 years) although this criteria is not a requisite. All patients had high levels of creatine kinase and abnormal electromyographic examination. The pathological pattern on muscular biopsy was a necrotizing myopathy without significant inflammatory cells infiltration. Cardio-respiratory function was normal and no associated neoplasia was found. Over the follow-up, we observed a marked corticosteroid-dependence, not improved by immunosuppressive drugs (azathioprine and methotrexate). The benefit of intravenous immunoglobulin was clear with, sometimes, prolonged responses. CONCLUSION: An early diagnosis of this myopathy is necessary in order to introduce an immunotherapy associated with a close monitoring. The therapeutic strategy (within which the stead of intravenous immunoglobulin seems increased) remains to be defined and long-term prospective studies are thus needed.

Increased ischemia-induced angiogenesis in the staggerer mouse, a mutant of the nuclear receptor Roralpha.

Ror alpha is an orphan nuclear receptor. In homozygous staggerer mutant mice (Ror alpha(sg/sg)), a deletion within the Ror alpha gene leads to an overexpression of inflammatory cytokines. Because inflammation and hypoxia are 2 key stimuli of ischemia-induced angiogenesis, we studied the role of Ror alpha in this setting. Ischemia was induced by ligation of the right femoral artery in C57BL/6 Ror alpha(+/+) and Ror alpha(sg/sg) mice. After 3 and 28 days, angiogenesis was evaluated by microangiography, measurement of capillary density using immunohistochemistry (anti-CD31), and measurement of blood flow by laser Doppler imaging. At day 3, angiographic score and blood flow were similar in Ror alpha(sg/sg) mice and in Ror alpha(+/+) littermates. Conversely, at day 28, Ror alpha(sg/sg) mice showed a significant 2-fold increase in angiographic score and a 3-fold increase in capillary density within the ischemic hindlimb compared with control. Functionally, this coincided with a significant rise in leg perfusion in Ror alpha(sg/sg) mice (0.83+/-0.05 for ischemic/nonischemic leg perfusion ratio) compared with Ror(+/+) mice (0.66+/-0.04, P<0.05). In addition, more extensive angiogenesis in Ror alpha(sg/sg) mice correlated with an increased expression of eNOS protein by 83+/-12% and 71+/-24% at 3 and 28 days, respectively (P<0.05), whereas the level of the antiangiogenic cytokine IL-12 was significantly reduced by 38+/-10% at day 28 (P<0.05). Conversely, no changes in VEGF expression were observed. Our study identifies for the first time a new role for Ror alpha as a potent negative regulator of ischemia-induced angiogenesis.

Protective role of interleukin-10 in atherosclerosis.

The potential role of anti-inflammatory cytokines in the modulation of the atherosclerotic process remains unknown. Interleukin (IL)-10 has potent deactivating properties in macrophages and T cells and modulates many cellular processes that may interfere with the development and stability of the atherosclerotic plaque. IL-10 is expressed in human atherosclerosis and is associated with decreased signs of inflammation. In the present study, we show that IL-10-deficient C57BL/6J mice fed an atherogenic diet and raised under specific pathogen-free conditions exhibit a significant 3-fold increase in lipid accumulation compared with wild-type mice. Interestingly, the susceptibility of IL-10-deficient mice to atherosclerosis was exceedingly high (30-fold increase) when the mice were housed under conventional conditions. Atherosclerotic lesions of IL-10-deficient mice showed increased T-cell infiltration, abundant interferon-gamma expression, and decreased collagen content. In vivo, transfer of murine IL-10 achieved 60% reduction in lesion size. These results underscore the critical roles of IL-10 in both atherosclerotic lesion formation and stability. Moreover, IL-10 appears to be crucial as a protective factor against the effect of environmental pathogens on atherosclerosis.

Expression of interleukin-18 in human atherosclerotic plaques and relation to plaque instability.

BACKGROUND: Interleukin (IL)-18 is a potent proinflammatory cytokine with potential atherogenic properties. Its expression and role in atherosclerosis, however, are unknown. METHODS AND RESULTS: In the present study, we examined stable and unstable human carotid atherosclerotic plaques retrieved by endarterectomy for the presence of IL-18 using reverse transcription-polymerase chain reaction (PCR), Western blot, and immunohistochemical techniques. IL-18 was highly expressed in the atherosclerotic plaques compared with control normal arteries and was localized mainly in plaque macrophages. IL-18 receptor was also upregulated in plaque macrophages and endothelial cells, suggesting potential biological effects. To examine the role of IL-18 in atherosclerosis, we determined the relation between IL-18 mRNA expression and signs of plaque instability using real-time quantitative PCR. Interestingly, significantly higher levels of IL-18 mRNA were found in symptomatic (unstable) plaques than asymptomatic (stable) plaques (P<0.01). CONCLUSIONS: These results suggest, for the first time, a major role for IL-18 in atherosclerotic plaque destabilization leading to acute ischemic syndromes.

Vestibular loss disrupts daily rhythm in rats.

Hypergravity disrupts the circadian regulation of temperature (Temp) and locomotor activity (Act) mediated through the vestibular otolithic system in mice. In contrast, we do not know whether the anatomical structures associated with vestibular input are crucial for circadian rhythm regulation at 1 G on Earth. In the present study we observed the effects of bilateral vestibular loss (BVL) on the daily rhythms of Temp and Act in semipigmented rats. Our model of vestibular lesion allowed for selective peripheral hair cell degeneration without any other damage. Rats with BVL exhibited a disruption in their daily rhythms (Temp and Act), which were replaced by a main ultradian period (τ <20 h) for 115.8 ± 68.6 h after vestibular lesion compared with rats in the control group. Daily rhythms of Temp and Act in rats with BVL recovered within 1 wk, probably counterbalanced by photic and other nonphotic time cues. No correlation was found between Temp and Act daily rhythms after vestibular lesion in rats with BVL, suggesting a direct influence of vestibular input on the suprachiasmatic nucleus. Our findings support the hypothesis that the vestibular system has an influence on daily rhythm homeostasis in semipigmented rats on Earth, and raise the question of whether daily rhythms might be altered due to vestibular pathology in humans.

Polluter identification with spaceborne radar imagery, AIS and forward drift modeling.

This study defines and assesses a new operational concept to identify the origin of pollution at sea, based on Synthetic Aperture Radar, Automatic Identification System, and a forward drift model. As opposed to traditional methodologies where the SAR detected pollution is backtracked in the past, our approach assumes that all the vessels pollute all along their way. Based on all the AIS data flows, the forward-tracked simulated pollutions are then compared to the detected pollution, and the potential polluter can be finally identified. Case studies are presented to showcase its usefulness in a variety of maritime situations with a focus on orphan pollutions in a dense traffic area. Out of the identification of the suspected polluters, the age and eventually the type of the pollution can be retrieved.

Involvement of interleukin-6 in atherosclerosis but not in the prevention of fatty streak formation by 17beta-estradiol in apolipoprotein E-deficient mice.

Interleukin-6 (IL-6) gene expressed in bone marrow-derived stromal cells and osteoblasts contributes to the state of mineralization and its control by estradiol may be involved in the development of post-menopausal osteoporosis. Since IL-6 is also expressed in the different cell populations of the arterial wall, the purpose of this study was to gain more insight into its involvement in the atherosclerotic process and the atheroprotective effect of estradiol by studying double deficient mice at the apolipoprotein E and IL-6 loci (IL-6(-/-)/E(-/-)). At 1 year of age, IL-6(-/-)/E(-/-) mice showed similar hypercholesterolemia to IL-6(+/+)/E(-/-) mice but presented significantly larger and more calcified lesions. In younger mice (sixteen weeks of age), no significant difference in fatty streaks could be detected in IL-6(+/+)/E(-/-), IL-6(+/-)/E(-/-) and IL-6(-/-)/E(-/-) mice on a normal chow diet. Estrogen supplementation at this age induced a decrease of fatty streak formation in all three genotypes. The combined data indicate that IL-6 expression is involved at the fibrous plaque stage of the atherosclerotic process but does not constitute a direct target for estradiol to prevent fatty streak formation.