Internalization of microparticles by endothelial cells promotes platelet/endothelial cell interaction under flow

BACKGROUND

Microparticles (MPs) released by activated or apoptotic cells increase in number in the blood of subjects with vascular or metabolic diseases and may contribute to thrombotic complications.

OBJECTIVES

In this study, we investigated whether MPs promoted platelet recruitment to endothelial cells in flow conditions, and by which mechanism.

METHODS

Human umbilical vein endothelial cells (HUVECs) grown in microslide perfusion chambers were exposed to MPs prepared in vitro from HUVECs, monocytes or platelets.

RESULTS

Videomicroscopy of DIOC-labelled blood perfused at arterial rate on human umbilical vein ECs demonstrated that, irrespective of their cell origin, MPs promoted the formation of platelet strings at the surface of HUVECs. This platelet/endothelial cell interaction was dependent on von Willebrand factor (VWF) expression at the HUVEC surface and involved Glycoprotein Ib and P-selectin. Interestingly, HUVECs internalized MPs within a few hours through a process involving anionic phospholipids, lactadherin and αvβ3 integrin. This uptake generated the production of reactive oxygen species via the xanthine/xanthine oxidase system (inhibited by allopurinol and the ROCK inhibitor Y-27632) and the NADPH oxidase (inhibited by SOD). Reactive oxygen species appeared essential for VWF expression at the endothelial cell surface and subsequent platelet/endothelial cell interaction under flow. The pathophysiological relevance of this process is underlined by the fact that circulating MPs from Type I diabetic patients induced platelet/endothelial cell interaction under flow, with an intensity correlated with the severity of the vasculopathy.

Structure and rheological properties of model microemulsion networks filled with nanoparticles

Model microemulsion networks of oil droplets stabilized by non-ionic surfactant and telechelic polymer C18 -PEO(10k)- C18 have been studied for two droplet-to-polymer size ratios. The rheological properties of the networks have been measured as a function of network connectivity and can be described in terms of simple percolation laws. The network structure has been characterised by Small Angle Neutron Scattering (SANS). A Reverse Monte Carlo (RMC) approach is used to demonstrate the interplay of attraction and repulsion induced by the copolymer. These model networks are then used as matrix for the incorporation of silica nanoparticles (R = 10 nm), individual dispersion being checked by scattering. A strong impact on the rheological properties is found for silica volume fractions up to 9%. q(A-1).

[Laryngeal schwannomas]

Laryngeal schwannoma is a rare benign tumour of the larynx. Schwannomas derive from the Schwann cells. The majority occurs in supraglottic area and may arise at any age. Magnetic resonance imaging (MRI) is the best imaging tool for suggesting the diagnosis in the appropriate clinical context. Conservative surgery is the treatment of choice. These tumors have to be distinguished from neurofibromas. We report 2 cases of laryngeal schwannoma. The first one concerned an 8-month-old baby with a laryngeal stridor history which seemed to be related to laryngomalacia. The second case was a 22-year-old man with a 5-year history of dysphonia. On nasofibroscopic examination, a sub mucosal mass enlarged the posterior part of the right false vocal cord in both cases. Both CT scan and MRI sequences showed a well margined lesion in the same place. Histological biopsies identified a schwannoma. External surgeries were subsequently and successfully performed. Diagnosis (imaging), specific treatment (endoscopic or external surgery), and possible association of laryngeal schwannomas are discussed.

Angiopathie amyloïde cérébrale sporadique

INTRODUCTION

Sporadic cerebral amyloid angiopathy (CAA) is a microangiopathy identified by neuropathological examination in more than 30 percent of patients over 85 years of age.

STATE OF ART

Boston criteria for diagnosis of CAA--related hemorrhage are as follows: "definite CAA", "Probable CAA with supporting pathology", "Probable CAA" and "Possible CAA". Clinical manifestations of CAA are either lobar, cortical, corticosubcortical or cerebellar hemorrhages associated with progressive dementia. Dementia, corresponding either to Alzheimer disease, vascular or mixed dementia, precedes hemorrhages in 25 to 40 percent of cases. Brain MRI can demonstrate microbleeding.

PERSPECTIVES

This review compares data regarding CAA prevalence, intracranial hemorrhages, and their risk factors in old patients. Diagnosis and preventive strategies are discussed. It would be useful to identify those affected by CAA among elderly demented patients with atrial fibrillation requiring anticoagulation therapy.

CONCLUSIONS

CAA is suspected in the presence of recurrent lobar or cerebellar hemorrhages, and moreover if associated with pre-existing dementia. In elderly demented patients, MRI criteria to detect CAA should be considered in order to prevent hemorrhage risk, particularly after anticoagulation therapy.