Directional control of neurite outgrowth: emerging technologies for Parkinson's disease using magnetic nanoparticles and magnetic field gradients

A challenge in current stem cell therapies for Parkinson's disease (PD) is controlling neuronal outgrowth from the substantia nigra towards the targeted area where connectivity is required in the striatum. Here we present progress towards controlling directional neurite extensions through the application of iron-oxide magnetic nanoparticles (MNPs) labelled neuronal cells combined with a magnetic array generating large spatially variant field gradients (greater than 20 T m-1). We investigated the viability of this approach in both two-dimensional and organotypic brain slice models and validated the observed changes in neurite directionality using mathematical models. Results showed that MNP-labelled cells exhibited a shift in directional neurite outgrowth when cultured in a magnetic field gradient, which broadly agreed with mathematical modelling of the magnetic force gradients and predicted MNP force direction. We translated our approach to an ex vivo rat brain slice where we observed directional neurite outgrowth of transplanted MNP-labelled cells from the substantia nigra towards the striatum. The improved directionality highlights the viability of this approach as a remote-control methodology for the control and manipulation of cellular growth for regenerative medicine applications. This study presents a new tool to overcome challenges faced in the development of new therapies for PD.

The impact of the COVID-19 epidemic on primary care in South-eastern France: implementation of a real-time monitoring system based on regional health insurance system data

BACKGROUND

The spring 2020 COVID-19 epidemic severely impacted France's healthcare system. The associated lockdown (17 March- 11 May 2020) and the risk of exposure to SARS-CoV-2 led patients to change their use of healthcare. This article presents the development and implementation of a real-time system to monitor i) private doctors' activity in South-eastern France, and ii) changes in prescription of drugs for people with diabetes, mental health disorders and for certain vaccines from Mars 2020 to October 2020.

METHODS

Data extracted from the regional healthcare insurance databases for 2019 and 2020 were used to construct indicators of healthcare use. They were calculated on a weekly basis, starting from week 2 2020 and compared for the same period between 2019 and 2020.

RESULTS

Private doctors' activity decreased during the spring 2020 lockdown (by 23 % for general practitioners and 46 % for specialists), followed by an almost complete return to normal after it ended until week 41. Over the same period, a huge increase in teleconsultations was observed, accounting for 30 % of private doctors' consultations at the height of the crisis. The start of the lockdown was marked by a peak in drug prescriptions, while vaccinations declined sharply (by 39 % for the measles, mumps and rubella (MMR) vaccine in children under 5 years old, and by 54 % for human papillomavirus vaccine in girls aged 10-14 years old).

CONCLUSION

The ongoing COVID-19 epidemic may lead to health consequences other than those directly attributable to the disease itself. Specifically, lockdowns and foregoing healthcare could be very harmful at the individual and population levels. The latter issue is a concern for French public authorities, which have implemented actions aimed at encouraging patients to immediately seek treatment. However, the COVID-19 crisis has also created opportunities, such as the roll-out of teleconsultation and tele-expertise. The indicators described here as part of the monitoring system can help public decision-makers to become more responsive and to implement tailored actions to better meet the general population's healthcare needs.

[The impact of the COVID-19 pandemic on first-line primary care in southeastern France: Feedback on the implementation of a real-time monitoring system based on regional health insurance data]

Position du problème

L’épidémie de COVID-19 du printemps 2020 a fortement affecté le système de soins. Le confinement et les risques d’exposition au coronavirus ont incité les patients à modifier leur recours aux soins. L’objectif était de partager un retour d’expérience sur la mise en place d’un dispositif de surveillance en temps réel de l’activité des médecins libéraux de la région Provence-Alpes-Côte d’Azur, et de l’évolution des remboursements de médicaments prescrits aux assurés du régime général pour le diabète, pour des troubles de la santé mentale et pour certains vaccins.

Méthodes

Les données ont été extraites à partir des bases régionales de l’Assurance maladie pour les années 2019 et 2020. Elles ont permis de construire des indicateurs en date de soins pour le régime général stricto sensu, calculés de façon hebdomadaire, à partir de la semaine 2.

Résultats

On constate une chute d’activité des médecins libéraux lors du confinement (−23 % pour les médecins généralistes ; −46 % pour les spécialistes), suivie d’un quasi retour à la normale par la suite. Dans le même temps, les téléconsultations ont connu un véritable essor : elles ont constitué 30 % des actes des médecins libéraux au plus fort de la crise. Le début du confinement a été marqué par un pic d’approvisionnement en médicaments, tandis que la vaccination a fortement diminué (−39 % concernant le vaccin contre la rougeole, les oreillons et la rubéole chez les enfants âgés de moins de 5 ans ; −54 % pour le vaccin contre les papillomavirus humains chez les filles âgées de 10–14 ans).

Conclusion

L’épidémie de COVID-19 risque d’entraîner d’autres conséquences sanitaires que celles directement imputables à la COVID-19 elle-même. Le renoncement aux soins pourrait causer des retards de soins fortement préjudiciables aux individus et à la collectivité. Ces questions inquiètent les autorités publiques, qui mettent en place des actions visant à inciter les patients à se soigner sans tarder. Mais la crise liée à la COVID-19 a aussi créé des opportunités, telles que le déploiement de la téléconsultation et de la télé-expertise. Bien que partiels, les indicateurs mis en œuvre peuvent permettre aux décideurs publics d’être réactifs et de mettre en place certaines actions afin de répondre aux besoins de santé des populations.

Kinetically Enhanced Fabrication of Homogeneous Biomimetic and Functional Emulsion Droplets

Characterized by a fluid and deformable interface, ligand-functionalized emulsion droplets are used as model probes to address biophysical, biological, and developmental questions. Functionalization protocols usually rely on the use of headgroup-modified phospholipids that are dissolved in the oil phase prior to emulsification, leading to a broad range of surface densities within a given droplet population. With the aim to coat particles homogeneously with biologically relevant lipids and proteins (streptavidin, immunoglobulins, etc.), we developed a reliable surface decoration protocol based on the use of polar cosolvents to dissolve the lipids in the aqueous phase after the droplet production. We show that the surface density of the lipids at the interface has a narrow normal distribution for droplets having the same size. We performed titration isotherms for lipids and biologically relevant proteins on these drops. Then, we studied the influence of the presence of surfactants in the medium on lipid insertion and compared the results for a range of polar cosolvents of increasing polarity. To assess both the generality and the biocompatibility of the method, we show that we can produce more sophisticated, monodisperse functional magnetic emulsions with a very high surface homogeneity. Using an oil denser than the surrounding culture medium, we show that IgG-coated droplets can be used as probes for phagocytosis experiments.

Magnetic hyperthermia-induced drug release from ureasil-PEO-γ-Fe2O3 nanocomposites

A multifunctional hybrid material suitable for cancer therapy, combining stimuli-responsive properties for drug delivery and magnetic hyperthermia.

Design of magnetic molecularly imprinted polymer nanoparticles for controlled release of doxorubicin under an alternative magnetic field in athermal conditions

An innovative magnetic delivery nanomaterial for triggered cancer therapy showing active control over drug release by using an alternative magnetic field is proposed. In vitro and In vivo release of doxorubicin (DOX) were investigated and showed a massive DOX release under an alternative magnetic field without temperature elevation of the medium.

Severe clinical toxicities are correlated with survival in patients with advanced renal cell carcinoma treated with sunitinib and sorafenib

BACKGROUND

In advanced renal cell carcinoma (RCC), sunitinib and sorafenib tyrosine kinase inhibitors (TKI) are associated with several clinical side effects, with no definitive established data concerning their clinical impact.

METHODS

From June 2006 to June 2008, main clinical TKI-induced toxicities, including digestive, cardiac, dermatologic and asthenia were retrospectively collected using the NCI-CTC version 3.0 in patients treated with TKI for an RCC.

RESULTS

The median overall survival was significantly improved in patients with grade 3-4 clinical toxicities (36 vs 12 months, P=0.009). In multivariate analysis, the Memorial Sloan-Kettering Cancer Center risk groups (good vs intermediate or poor) and clinical toxicities (grade 3-4 vs 1-2) were identified as independent prognostic factors of better survival (P=0.002 and P=0.02, respectively). The Charlson comorbidity index score (>7 vs <7) was identified as independent predictive factor of severe clinical TKI-induced toxicities (P=0.02).

CONCLUSION

In this unselected patients of RCC, clinical TKI-related severe toxicities were more frequent in patients with comorbidities and were associated with better survival.

[Coronary embolism due to an adherent right atrium thrombus through a patent foramen ovale]

This observation relates to the discovery of native coronary paradoxical embolism secondary to thrombus adherent to the right atrium through a patent foramen ovale (PFO). A patient of 64 years, with a history of mitral regurgitation not followed, was hospitalized for acute respiratory distress due to a mitral insufficiency (MI) with a ruptured chordae and pulmonary embolism. Coronary angiography was performed and revealed two typical images of coronary embolism associated to a non-atheromatous coronary tree. The patient underwent a mitral valve replacement. After the establishment of cardiopulmonary bypass, adherent fibrin and cruoric thrombus of the right atrium and a PFO were found. The analysis of the valves did not reveal any arguments for infective endocarditis. A CT scan, performed as the patient remained unconscious after surgery, showed several cerebral infarcts. Paradoxical embolism coronary was diagnosed in front of the combination of adherent thrombus in the right atrium, pulmonary embolism and systemic coronary and cerebral embolism with a PFO. Coronary embolism rarely happens. It is mainly due to three causes: iatrogenic origin in most cases, direct causes due to micro emboli, particularly from infectious endocarditis and paradoxical embolic origin. There are two types of right atrial thrombus; the most common is the mobile thrombus from the peripheral venous system. The other one, which is more rare, is the adherent thrombus, which occurs in situ. Coronary embolism of paradoxical origin represents a small proportion of the causes of coronary embolism. However, this diagnosis must be considered.

Anterograde transport of TrkB in axons is mediated by direct interaction with Slp1 and Rab27

The neurotrophin receptors TrkA, TrkB, and TrkC are localized at the surface of the axon terminus and transmit key signals from brain-derived neurotrophic factor (BDNF) for diverse effects on neuronal survival, differentiation, and axon formation. Trk receptors are sorted into axons via the anterograde transport of vesicles and are then inserted into axonal plasma membranes. However, the transport mechanism remains largely unknown. Here, we show that the Slp1/Rab27B/CRMP-2 complex directly links TrkB to Kinesin-1, and that this association is required for the anterograde transport of TrkB-containing vesicles. The cytoplasmic tail of TrkB binds to Slp1 in a Rab27B-dependent manner, and CRMP-2 connects Slp1 to Kinesin-1. Knockdown of these molecules by siRNA reduces the anterograde transport and membrane targeting of TrkB, thereby inhibiting BDNF-induced ERK1/2 phosphorylation in axons. Our data reveal a molecular mechanism for the selective anterograde transport of TrkB in axons and show how the transport is coupled to BDNF signaling.

Polysialylation increases lateral diffusion of neural cell adhesion molecule in the cell membrane

Polysialic acid (PSA) is a polymer of N-acetylneuraminic acid residues added post-translationally to the membrane-bound neural cell adhesion molecule (NCAM). The large excluded volume created by PSA polymer is thought to facilitate cell migration by decreasing cell adhesion. Here we used live cell imaging (spot fluorescence recovery after photobleaching and fluorescence correlation spectroscopy) combined with biochemical approaches in an attempt to uncover a link between cell motility and the impact of polysialylation on NCAM dynamics. We show that PSA regulates specifically NCAM lateral diffusion and this is dependent on the integrity of the cytoskeleton. However, whereas the glial-derivative neurotrophic factor chemotactic effect is dependent on PSA, the molecular dynamics of PSA-NCAM is not directly affected by glial-derivative neurotrophic factor. These findings reveal a new intrinsic mechanism by which polysialylation regulates NCAM dynamics and thereby a biological function like cell migration.

Sterically stabilized superparamagnetic liposomes for MR imaging and cancer therapy: pharmacokinetics and biodistribution

Pharmacokinetics of magnetic-fluid-loaded liposomes (MFLs) with mean hydrodynamic diameter of 200 nm sterically stabilized by poly(ethylene glycol) (PEG) and labelled by a fluorescent lipid probe, N-(lissamine rhodamine B sulfonyl) phosphatidylethanolamine (Rho-PE) was studied. The loading consisted in an aqueous suspension of maghemite nanocrystals close to 8 nm in size at 1.7 Fe(III)mol/mol total lipids ratio. Double tracking of MFL in blood was performed versus time after intravenous administration in mice. Lipids constituting vesicle membrane were followed by Rho-PE fluorescence spectroscopy while iron oxide was determined independently by relaxometry. MFLs circulating in the vascular compartment conserved their vesicle structure and content. The pharmacokinetic profile was characterized by two first-order kinetics of elimination with distinct plasmatic half-lives of 70 min and 12.5 h. Iron biodistribution and organ histology clearly highlighted preferential MFL accumulation within liver and spleen. The pathway in spleen supported that elimination was governed by the mononuclear phagocyte system (MPS). PEG coating was essential to prolong MFL circulation time whereas iron oxide loading tends to favour uptake by the MPS. Despite partial uptake in the earlier times after administration, MFLs exhibited long circulation behaviour over a 24-h period that, coupled to magnetic targeting, encourages further use in drug delivery.

Phosphorylation by Rho kinase regulates CRMP-2 activity in growth cones

Collapsin response mediator protein 2 (CRMP-2) enhances the advance of growth cones by regulating microtubule assembly and Numb-mediated endocytosis. We previously showed that Rho kinase phosphorylates CRMP-2 during growth cone collapse; however, the roles of phosphorylated CRMP-2 in growth cone collapse remain to be clarified. Here, we report that CRMP-2 phosphorylation by Rho kinase cancels the binding activity to the tubulin dimer, microtubules, or Numb. CRMP-2 binds to actin, but its binding is not affected by phosphorylation. Electron microscopy revealed that CRMP-2 localizes on microtubules, clathrin-coated pits, and actin filaments in dorsal root ganglion neuron growth cones, while phosphorylated CRMP-2 localizes only on actin filaments. The phosphomimic mutant of CRMP-2 has a weakened ability to enhance neurite elongation. Furthermore, ephrin-A5 induces phosphorylation of CRMP-2 via Rho kinase during growth cone collapse. Taken together, these results suggest that Rho kinase phosphorylates CRMP-2, and inactivates the ability of CRMP-2 to promote microtubule assembly and Numb-mediated endocytosis, during growth cone collapse.

PIP3 is involved in neuronal polarization and axon formation

Recent experiments in various cell types such as mammalian neutrophils and Dictyostelium discoideum amoebae point to a key role for the lipid product of PI 3-kinase, PIP(3), in determining internal polarity. In neurons, as a consequence of the elongation of one neurite, the axon is specified and the cell acquires its polarity. To test the hypothesis that PI 3-kinase and PIP(3) may play a role in neuronal polarity, and especially in axon specification, we observed localization of PIP(3) visualized by Akt-PH-GFP in developing hippocampal neurons. We found that PIP(3) accumulates in the tip of the growing processes. This accumulation is inhibited by addition of PI 3-kinase inhibitors. Those inhibitors, consistently with a role of PIP(3) in process formation and elongation, delay the transition from stage 1 neurons to stage 3 neurons, and both axon formation and elongation. Moreover, when the immature neurite contacts a bead coated with laminin, a substrate known to induce axon specification, PIP(3) accumulates in its growth cone followed by a rapid elongation of the neurite. In such conditions, the addition of PI 3-kinase inhibitors inhibits both PIP(3) accumulation and future axon elongation. These results suggest that PIP(3) is involved in axon specification, possibly by stimulating neurite outgrowth. In addition, when a second neurite contacted the beads, this neurite rapidly elongates whereas the elongation of the first laminin-contacting neurite stops, consistently with the hypothesis of a negative feedback mechanism from the growing future axon to the other neurites.

[Rho proteins: their function in neurons]

Neurons possess a polarized morphology. In general, each neuron has several dendrites but only one axon. Such morphology is the basis for directionalized rapid signaling, information flowing from the short dendrites to the long axon. The mechanisms involved in the establishment of the neuronal polarity remain largely unknown. However, recently, members of Rho family proteins have been implicated in the regulation of neuronal morphology especially development of neuronal polarity, axon outgrowth and guidance, dendritic tree elaboration and synapse formation. Moreover, the Rho GTPases have been reported to be directly or indirectly involved in some neurological conditions such as X-linked mental retardation as well as Alzheimer's and Parkinson's diseases. These findings demonstrate the importance of Rho GTPases in the development, maintenance and function of the nervous system.

[Perforated gastric ulcer in the child: a rare complication, a case report]

Perforated gastric ulcer is unusual in children. We report a case in a girl with an unexpected evolution.

CASE REPORT

A 13-year-old girl was admitted for abdominal pain. She had no particular personal history but her father had a perforated ulcer. On admission she was not painful, her abdomen was soft on palpation. The white blood cell count was 1.7 x 10(3)/mm3. A right pneumoperitoneum was seen on an abdominal X-ray film. Because of her good general status and the normalization of the abdominal X ray film six hours later, no surgical exploration was performed. On the fourth day, a gastrointestinal endoscopy showed an anterior gastric ulcer which was perforated. Biopsies did not isolate H. pylori. The patient was given a treatment with amoxicillin-metronidazole (7 d) and oméprazole (7 weeks). An endoscopic control, one month later, showed a total healing of the gastric ulcer.

CONCLUSION

Peptic ulcerations and their complications are underdiagnosed in childhood. This could lead to delay in diagnosis or inappropriate treatment specially in case of perforation.

CRMP-2 binds to tubulin heterodimers to promote microtubule assembly

Regulated increase in the formation of microtubule arrays is thought to be important for axonal growth. Collapsin response mediator protein-2 (CRMP-2) is a mammalian homologue of UNC-33, mutations in which result in abnormal axon termination. We recently demonstrated that CRMP-2 is critical for axonal differentiation. Here, we identify two activities of CRMP-2: tubulin-heterodimer binding and the promotion of microtubule assembly. CRMP-2 bound tubulin dimers with higher affinity than it bound microtubules. Association of CRMP-2 with microtubules was enhanced by tubulin polymerization in the presence of CRMP-2. The binding property of CRMP-2 with tubulin was apparently distinct from that of Tau, which preferentially bound microtubules. In neurons, overexpression of CRMP-2 promoted axonal growth and branching. A mutant of CRMP-2, lacking the region responsible for microtubule assembly, inhibited axonal growth and branching in a dominant-negative manner. Taken together, our results suggest that CRMP-2 regulates axonal growth and branching as a partner of the tubulin heterodimer, in a different fashion from traditional MAPs.

[Procalcitonin and viral meningitis: reduction of unnecessary antibiotics by measurement during an outbreak]

OBJECTIVE

Viral meningitis are often treated with antibiotics in emergency because routine analysis of CSF is not always efficient for distinguishing between viral and bacterial infection. The aim of the study was to evaluate the usefulness of procalcitonin (PCT) to reduce antibiotic treatments.

METHODS AND RESULTS

A blood PCT level < 0.5 ng/mL was prospectively used for the diagnosis of viral origin of meningitis in 58 patients (two months-14 years), in which enterovirus was isolated by culture or PCR during an outbreak (May-June 2000). CSF cells range was 10 to 2800/mL (m: 244), PMN 5 to 2464/mL and CSF proteins range was 0.19 to 0.92 mg/dL (m: 0.37). Seventeen patients received antibiotic therapy in admission. In nine patients, PCT (dosage was routinely measured 3/week) result < 0.5 ng/mL was obtained in 24 h and in 48 h in six: treatment was then stopped and children led hospital. In two patients, PCT was > 1 ng/mL because of bacterial coinfection. CSF and PCT values were similar to those of an already published control group.

CONCLUSION

PCT dosage allowed to shorten hospitalization of 4.47 (controls) to 2.06 (patients) days in patients receiving unnecessary antibiotic treatments. During this outbreak, PCT dosage allowed to reduce 40 days of hospitalization.

Magnetic phospholipid tubes connected to magnetoliposomes: Pearling instability induced by a magnetic field

We propose here a method to modify the membrane tension of phospholipid tubes with an applied magnetic field. The tubes are connected to giant liposomes capping the tubes at both ends. Tubes and liposomes are all filled with a magnetic fluid. The tension of the tube membrane is tuned by the deformation of the ending liposomes under the applied field. We modelize the magnetoliposome deformation and we are then able to describe the tube evolution. At low magnetic fields, the tube remains at equilibrium with a cylindrical shape and a uniform radius. It responds to an increase of membrane tension by a diameter reduction. Above a magnetic-field threshold, the cylindrical shape becomes unstable with respect to a pearling deformation. The tube shape then selected by the system is an unduloid, with a constant mean curvature equal to C 0, the spontaneous curvature of the membrane.

[Dengue in New Caledonia. Study of 68 pediatric cases]

New Caledonia is a French territory of Pacific Ocean, where frequent dengue outbreaks occur. In 1995 and 1996, 3042 cases (including 18.3% children) were diagnosed in Pasteur Institute of Noumea.

PATIENTS AND METHODS

This work was a clinical and biological study of 68 in-patients of different ethnical groups in children. Among these young patients, 14 cases of dengue hemorrhagic fever occurred.

RESULTS

The children were admitted to hospital after an average of 2.7 days of complaint, and during 6.7 days. The most important symptoms were fever at 39 degrees C (100%) during 2.2 days, sweatings (100%), malaise (57%) and headache (50%). Forty children had, at least, one hemorrhagic symptom. Leucopenia was noticed in 42 children, on an average of 4.2 days. A thrombocytopenia (mean 114,746 platelets/mm3) occurred in 5.3 days in 34 children (six cases with less than 10,000 platelets/mm3). A bacterial infection arised in 23.5% of children.

CONCLUSION

Dengue is an important problem of public health, which occurs in all population, including the young children. The fight against dengue fever by a rapid destruction of larvae and adult mosquitoes led to the decrease of the outbreak.

CRMP-2 induces axons in cultured hippocampal neurons

In cultured hippocampal neurons, one axon and several dendrites differentiate from a common immature process. Here we found that CRMP-2/TOAD-64/Ulip2/DRP-2 (refs. 2-4) level was higher in growing axons of cultured hippocampal neurons, that overexpression of CRMP-2 in the cells led to the formation of supernumerary axons and that expression of truncated CRMP-2 mutants suppressed the formation of primary axon in a dominant-negative manner. Thus, CRMP-2 seems to be critical in axon induction in hippocampal neurons, thereby establishing and maintaining neuronal polarity.

Shape transitions of giant liposomes induced by an anisotropic spontaneous curvature

We explore how a magnetic field breaks the symmetry of an initially spherical giant liposome filled with a magnetic colloid. The condition of rotational symmetry along the field axis leads either to a prolate or to an oblate ellipsoid. We demonstrate that an electrostatic interaction between the nanoparticles and the membrane triggers the shape transition.

Phosphorylation of collapsin response mediator protein-2 by Rho-kinase. Evidence for two separate signaling pathways for growth cone collapse

We previously identified Rho-associated protein kinase (Rho-kinase) as a specific effector of Rho. In this study, we identified collapsin response mediator protein-2 (CRMP-2), as a novel Rho-kinase substrate in the brain. CRMP-2 is a neuronal protein whose expression is up-regulated during development. Rho-kinase phosphorylated CRMP-2 at Thr-555 in vitro. We produced an antibody that specifically recognizes CRMP-2 phosphorylated at Thr-555. Using this antibody, we found that Rho-kinase phosphorylated CRMP-2 downstream of Rho in COS7 cells. Phosphorylation of CRMP-2 was observed in chick dorsal root ganglion neurons during lysophosphatidic acid (LPA)-induced growth cone collapse, whereas the phosphorylation was not detected during semaphorin-3A-induced growth cone collapse. Both LPA-induced CRMP-2 phosphorylation and LPA-induced growth cone collapse were inhibited by Rho-kinase inhibitor HA1077 or Y-32885. LPA-induced growth cone collapse was also blocked by a dominant negative form of Rho-kinase. On the other hand, semaphorin-3A-induced growth cone collapse was not inhibited by a dominant negative form of Rho-kinase. Furthermore, overexpression of a mutant CRMP-2 in which Thr-555 was replaced by Ala significantly inhibited LPA-induced growth cone collapse. These results demonstrate the existence of Rho-kinase-dependent and -independent pathways for growth cone collapse and suggest that CRMP-2 phosphorylation by Rho-kinase is involved in the former pathway.

Silica Coating on Colloidal Maghemite Particles

Maghemite colloidal particles are coated with a silica layer using a silicon alkoxide as silica precursor. The coating process is studied by electrophoresis, quasi-elastic light scattering, nitrogen adsorption, and infrared spectrometry analyses. The conditions of complete coverage of the iron oxide particles by silica and the nature of the maghemite-silica interface are discussed. Copyright 1999 Academic Press.