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Abstract Background The clear visualization of 3D organization at the cellular level in plant tissues is needed to fully understand plant development processes. Imaging tools allow the visualization of the main fluorophores and in vivo growth monitoring. Confocal microscopy coupled with the use of propidium iodide (PI) counter-staining is one of the most popular tools used to characterize the structure of root meristems in A. thaliana. However, such an approach is relatively ineffective in species with more complex and thicker root systems. Results We adapted a PI counter-staining protocol to visualize the internal 3D architecture of rice root meristems using multiphoton microscopy. This protocol is simple and compatible with the main fluorophores (CFP, GFP and mCherry). The efficiency and applicability of this protocol were demonstrated by screening a population of 57 enhancer trap lines. We successfully characterized GFP expression in all of the lines and identified 5 lines with tissue-specific expression. Conclusions All of these resources are now available for the rice community and represent critical tools for future studies of root development.

Inherited retinal diseases (IRDs) are characterised by progressive vision loss. There are over 270 causative IRD genes and variants within the same gene can cause clinically distinct disorders. One example is RLBP1 that encodes CRALBP. CRALBP is an essential protein in the rod and cone visual cycles that take place primarily in the retinal pigment epithelium (RPE) but also in Müller cells of the neuroretina. RLBP1 variants lead to three clinical subtypes: Bothnia dystrophy, retinitis punctata albescens and Newfoundland rod-cone dystrophy. We modelled RLBP1-IRD subtypes using patient-specific iPSC-derived RPE and identified pathophysiological markers that served as pertinent therapeutic read-outs. We developed an AAV2/5-mediated gene supplementation strategy and performed a proof-of-concept study in the human models, which was validated in vivo in an Rlbp1 -/- murine model. Most importantly, we identified a previously unsuspected smaller CRALBP isoform that is naturally and differentially expressed both in the human and murine retina. This previously unidentified isoform is produced from an alternative methionine initiation site. This work provides further insights into CRALBP expression and RLBP1-associated pathophysiology and raises important considerations for successful gene supplementation therapy., (Copyright © 2024 The Author(s). Published by Elsevier Inc. All rights reserved.)

The cornea is a transparent tissue that covers the eye and is crucial for clear vision. It is the most innervated tissue in the body. This innervation provides sensation and trophic function to the eye and contributes to preserving corneal integrity. The pathological disruption of this innervation is termed neurotrophic keratitis. This can be triggered by injury to the eye, surgery, or disease. In this study, we propose three different protocols for inflicting damage on the innervation in ways that recapitulate the three types of cases generally encountered in the clinic. The first method consists in making an abrasion of the epithelium with an ophthalmic burr. This involves the removal of the epithelial layer, the free nerve endings, and the subbasal plexus in a manner similar to the photorefractive keratectomy surgery performed in the clinic. The second method only targets the innervation by sectioning it at the periphery with a biopsy punch, maintaining the integrity of the epithelium. This method is similar to the first steps of lamellar keratoplasty and leads to a degeneration of the innervation followed by regrowth of the axons in the central cornea. The last method damages the innervation of a transgenic mouse model using a multiphoton microscope, which specifically localizes the site of cauterization of the fluorescent nerve fibers. This method inflicts the same damage as photokeratitis, an overexposure to UV light. This study describes different options for investigating the physiopathology of corneal innervation, particularly the degeneration and regeneration of the axons. Promoting regeneration is crucial for avoiding such complications as epithelium defects or even perforation of the cornea. The proposed models can help test new pharmacological molecules or gene therapy that enhance nerve regeneration and limit disease progression.

Traumatic spinal cord injury (SCI) induces irreversible autonomic and sensory-motor impairments. A large number of patients exhibit chronic SCI and no curative treatment is currently available. Microglia are predominant immune players after SCI, they undergo highly dynamic processes, including proliferation and morphological modification. In a translational aim, we investigated whether microglia proliferation persists at chronic stage after spinal cord hemisection and whether a brief pharmacological treatment could modulate microglial responses. We first carried out a time course analysis of SCI-induced microglia proliferation associated with morphological analysis up to 84 days post-injury (dpi). Second, we analyzed outcomes on microglia of an oral administration of GW2580, a colony stimulating factor-1 receptor tyrosine kinase inhibitor reducing selectively microglia proliferation. After SCI, microglia proliferation remains elevated at 84 dpi. The percentage of proliferative microglia relative to proliferative cells increases over time reaching almost 50% at 84 dpi. Morphological modifications of microglia processes are observed up to 84 dpi and microglia cell body area is transiently increased up to 42 dpi. A transient post-injury GW2580-delivery at two chronic stages after SCI (42 and 84 dpi) reduces microglia proliferation and modifies microglial morphology evoking an overall limitation of secondary inflammation. Finally, transient GW2580-delivery at chronic stage after SCI modulates myelination processes. Together our study shows that there is a persistent microglia proliferation induced by SCI and that a pharmacological treatment at chronic stage after SCI modulates microglial responses. Thus, a transient oral GW2580-delivery at chronic stage after injury may provide a promising therapeutic strategy for chronic SCI patients., (© 2023 The Authors. GLIA published by Wiley Periodicals LLC.)

Retinitis pigmentosa (RP) is the most common inherited retinal disease (IRD) and is characterized by photoreceptor degeneration and progressive vision loss. We report 4 patients presenting with RP from 3 unrelated families with variants in TBC1D32, which to date has never been associated with an IRD. To validate TBC1D32 as a putative RP causative gene, we combined Xenopus in vivo approaches and human induced pluripotent stem cell-derived (iPSC-derived) retinal models. Our data showed that TBC1D32 was expressed during retinal development and that it played an important role in retinal pigment epithelium (RPE) differentiation. Furthermore, we identified a role for TBC1D32 in ciliogenesis of the RPE. We demonstrated elongated ciliary defects that resulted in disrupted apical tight junctions, loss of functionality (delayed retinoid cycling and altered secretion balance), and the onset of an epithelial-mesenchymal transition-like phenotype. Last, our results suggested photoreceptor differentiation defects, including connecting cilium anomalies, that resulted in impaired trafficking to the outer segment in cones and rods in TBC1D32 iPSC-derived retinal organoids. Overall, our data highlight a critical role for TBC1D32 in the retina and demonstrate that TBC1D32 mutations lead to RP. We thus identify TBC1D32 as an IRD-causative gene.

Background: Human-induced pluripotent stem cell-derived retinal organoids are a valuable tool for disease modelling and therapeutic development. Many efforts have been made over the last decade to optimise protocols for the generation of organoids that correctly mimic the human retina. Most protocols use common media supplements; however, protocol-dependent variability impacts data interpretation. To date, the lack of a systematic comparison of a given protocol with or without supplements makes it difficult to determine how they influence the differentiation process and morphology of the retinal organoids., Methods: A 2D-3D differentiation method was used to generate retinal organoids, which were cultured with or without the most commonly used media supplements, notably retinoic acid. Gene expression was assayed using qPCR analysis, protein expression using immunofluorescence studies, ultrastructure using electron microscopy and 3D morphology using confocal and biphoton microscopy of whole organoids., Results: Retinoic acid delayed the initial stages of differentiation by modulating photoreceptor gene expression. At later stages, the presence of retinoic acid led to the generation of mature retinal organoids with a well-structured stratified photoreceptor layer containing a predominant rod population. By contrast, the absence of retinoic acid led to cone-rich organoids with a less organised and non-stratified photoreceptor layer., Conclusions: This study proves the importance of supplemented media for culturing retinal organoids. More importantly, we demonstrate for the first time that the role of retinoic acid goes beyond inducing a rod cell fate to enhancing the organisation of the photoreceptor layer of the mature organoid., (© 2022. The Author(s).)

The voltage-dependent anion channel (VDAC), the most abundant protein on the outer mitochondrial membrane, is implicated in ATP, ion and metabolite exchange with cell compartments. In particular, the VDAC participates in cytoplasmic and mitochondrial Ca 2+ homeostasis. Notably, the Ca 2+ efflux out of Schwann cell mitochondria is involved in peripheral nerve demyelination that underlies most peripheral neuropathies. Hexokinase (HK) isoforms I and II, the main ligands of the VDAC, possess a hydrophobic N-terminal structured in α-helix (NHKI) that is necessary for the binding to the VDAC. To gain further insight into the molecular basis of HK binding to the VDAC, we developed and optimized peptides based on the NHKI sequence. These modifications lead to an increase of the peptide hydrophobicity and helical content that enhanced their ability to prevent peripheral nerve demyelination. Our results provide new insights into the molecular basis of VDAC/HK interaction that could lead to the development of therapeutic compounds for demyelinating peripheral neuropathies.

Background: Chronic Obstructive Pulmonary Disease (COPD), a major cause of mortality and disability, is a complex disease with heterogeneous and ill-understood biological mechanisms. Human induced pluripotent stem cells (hiPSCs) are a promising tool to model human disease, including the impact of genetic susceptibility. Methods: We developed a simple and reliable method for reprogramming peripheral blood mononuclear cells into hiPSCs and to differentiate them into air−liquid interface bronchial epithelium within 45 days. Importantly, this method does not involve any cell sorting step. We reprogrammed blood cells from one healthy control and three patients with very severe COPD. Results: The mean cell purity at the definitive endoderm and ventral anterior foregut endoderm (vAFE) stages was >80%, assessed by quantifying C-X-C Motif Chemokine Receptor 4/SRY-Box Transcription Factor 17 (CXCR4/SOX17) and NK2 Homeobox 1 (NKX2.1) expression, respectively. vAFE cells from all four hiPSC lines differentiated into bronchial epithelium in air−liquid interface conditions, with large zones covered by beating ciliated, basal, goblets, club cells and neuroendocrine cells, as found in vivo. The hiPSC-derived airway epithelium (iALI) from patients with very severe COPD and from the healthy control were undistinguishable. Conclusions: iALI bronchial epithelium is ready for better understanding lung disease pathogenesis and accelerating drug discovery.

Background: Articular cartilage is a complex tissue with poor healing capacities. Current approaches for cartilage repair based on mesenchymal stromal cells (MSCs) are often disappointing because of the lack of relevant differentiation factors that could drive MSC differentiation towards a stable mature chondrocyte phenotype., Results: We used a large-scale transcriptomic approach to identify genes that are modulated at early stages of chondrogenic differentiation using the reference cartilage micropellet model. We identified several modulated genes and selected neuromedin B (NMB) as one of the early and transiently modulated genes. We found that the timely regulated increase of NMB was specific for chondrogenesis and not observed during osteogenesis or adipogenesis. Furthermore, NMB expression levels correlated with the differentiation capacity of MSCs and its inhibition resulted in impaired chondrogenic differentiation indicating that NMB is required for chondrogenesis. We further showed that NMB activated the calcineurin activity through a Ca 2+ -dependent signaling pathway., Conclusion: NMB is a newly described chondroinductive bioactive factor that upregulates the key chondrogenic transcription factor Sox9 through the modulation of Ca 2+ signaling pathway and calcineurin activity., (© 2021. The Author(s).)

No curative treatment is available for any deficits induced by spinal cord injury (SCI). Following injury, microglia undergo highly diverse activation processes, including proliferation, and play a critical role on functional recovery. In a translational objective, we investigated whether a transient pharmacological reduction of microglia proliferation after injury is beneficial for functional recovery after SCI in mice and nonhuman primates. Methods: The colony stimulating factor-1 receptor (CSF1R) regulates proliferation, differentiation, and survival of microglia. We orally administrated GW2580, a CSF1R inhibitor that inhibits microglia proliferation. In mice and nonhuman primates, we then analyzed treatment outcomes on locomotor function and spinal cord pathology. Finally, we used cell-specific transcriptomic analysis to uncover GW2580-induced molecular changes in microglia. Results: First, transient post-injury GW2580 administration in mice improves motor function recovery, promotes tissue preservation and/or reorganization (identified by coherent anti-stokes Raman scattering microscopy), and modulates glial reactivity. Second, post-injury GW2580-treatment in nonhuman primates reduces microglia proliferation, improves motor function recovery, and promotes tissue protection. Finally, GW2580-treatment in mice induced down-regulation of proliferation-associated transcripts and inflammatory associated genes in microglia that may account for reduced neuroinflammation and improved functional recovery following SCI. Conclusion: Thus, a transient oral GW2580 treatment post-injury may provide a promising therapeutic strategy for SCI patients and may also be extended to other central nervous system disorders displaying microglia activation., Competing Interests: Competing Interests: The authors have declared that no competing interest exists., (© The author(s).)

Human-induced pluripotent stem cell (hiPSC)-derived retinal pigment epithelium (RPE) is a powerful tool for pathophysiological studies and preclinical therapeutic screening, as well as a source for clinical cell transplantation. Thus, it must be validated for maturity and functionality to ensure correct data readouts and clinical safety. Previous studies have validated hiPSC-derived RPE as morphologically characteristic of the tissue in the human eye. However, information concerning the expression and functionality of ion channels is still limited. We screened hiPSC-derived RPE for the polarized expression of a panel of L-type (Ca V 1.1, Ca V 1.3) and T-type (Ca V 3.1, Ca V 3.3) Ca 2+ channels, K + channels (Maxi-K, Kir4.1, Kir7.1), and the Cl - channel ClC-2 known to be expressed in native RPE. We also tested the roles of these channels in key RPE functions using specific inhibitors. In addition to confirming the native expression profiles and function of certain channels, such as L-type Ca 2+ channels, we show for the first time that T-type Ca 2+ channels play a role in both phagocytosis and vascular endothelial growth factor (VEGF) secretion. Moreover, we demonstrate that Maxi-K and Kir7.1 channels are involved in the polarized secretion of VEGF and pigment epithelium-derived factor (PEDF). Furthermore, we show a novel localization for ClC-2 channel on the apical side of hiPSC-derived RPE, with an overexpression at the level of fluid-filled domes, and demonstrate that it plays an important role in phagocytosis, as well as VEGF and PEDF secretion. Taken together, hiPSC-derived RPE is a powerful model for advancing fundamental knowledge of RPE functions., (© 2021 Federation of American Societies for Experimental Biology.)

CDK5 plays a major role in neuronal functions, and is hyperactivated in neurodegenerative pathologies as well as in glioblastoma and neuroblastoma. Although this kinase constitutes an established biomarker and pharmacological target, there are few means of probing its activity in cell extracts or in living cells. To this aim a fluorescent peptide reporter of CDK5 kinase activity, derived from a library of CDK5-specific substrates, is engineered and its ability to respond to recombinant CDK5/p25 is established and CDK5 activity in glioblastoma cell extracts is reported on through sensitive changes in fluorescence intensity. A cell-penetrating variant of this biosensor which can be implemented to image CDK5 activation dynamics in space and in time is further implemented. This original biosensor constitutes a potent tool for quantifying differences in CDK5 activity following treatment with selective inhibitors and for monitoring CDK5 activation, following inhibition or stimulation, in a physiologically relevant environment. As such it offers attractive opportunities to develop a diagnostic assay for neuronal pathologies associated with hyperactivated CDK5, as well as a companion assay to evaluate response to new therapies targeting this kinase., (© 2020 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Glioblastoma Multiforme (GBM) invasiveness renders complete surgical resection impossible and highly invasive Glioblastoma Initiating Cells (GICs) are responsible for tumour recurrence. Their dissemination occurs along pre-existing fibrillary brain structures comprising the aligned myelinated fibres of the corpus callosum (CC) and the laminin (LN)-rich basal lamina of blood vessels. The extracellular matrix (ECM) of these environments regulates GIC migration, but the underlying mechanisms remain largely unknown. In order to recapitulate the composition and the topographic properties of the cerebral ECM in the migration of GICs, we have set up a new aligned polyacrylonitrile (PAN)-derived nanofiber (NF) scaffold. This system is suitable for drug screening as well as discrimination of the migration potential of different glioblastoma stem cells. Functionalisation with LN increases the spatial anisotropy of migration and modulates its mode from collective to single cell migration. Mechanistically, equally similar to what has been observed for mesenchymal migration of GBM in vivo, is the upregulation of galectin-3 and integrin-β1 in Gli4 cells migrating on our NF scaffold. Downregulation of Calpain-2 in GICs migrating in vivo along the CC and in vitro on LN-coated NF underlines a difference in the turnover of focal adhesion (FA) molecules between single-cell and collective types of migration.

Myelin sheath produced by Schwann cells covers and nurtures axons to speed up nerve conduction in peripheral nerves. Demyelinating peripheral neuropathies result from the loss of this myelin sheath and so far, no treatment exists to prevent Schwann cell demyelination. One major hurdle to design a therapy for demyelination is the lack of reliable measures to evaluate the outcome of the treatment on peripheral myelin in patients but also in living animal models. Non-linear microscopy techniques which include second harmonic generation (SHG), third harmonic generation (THG) and coherent anti-stokes Raman scattering (CARS) were used to image myelin ex vivo and in vivo in the sciatic nerve of healthy and demyelinating mice and rats. SHG did not label myelin and THG required too much light power to be compatible with live imaging. CARS is the most reliable of these techniques for in vivo imaging and it allows for the analysis and quantification of myelin defects in a rat model of CMT1A disease. This microscopic technique therefore constitutes a promising, reliable and robust readout tool in the development of new treatments for demyelinating peripheral neuropathies., (© 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Central nervous system (CNS) injury has been observed to lead to microglia activation and monocytes infiltration at the lesion site. Ex vivo diffusion magnetic resonance imaging (diffusion MRI or DWI) allows detailed examination of CNS tissues, and recent advances in clearing procedures allow detailed imaging of fluorescent-labeled cells at high resolution. No study has yet combined ex vivo diffusion MRI and clearing procedures to establish a possible link between microglia/monocytes response and diffusion coefficient in the context of spinal cord injury (SCI). We carried out ex vivo MRI of the spinal cord at different time-points after spinal cord transection followed by tetrahydrofuran based clearing and examined the density and morphology of microglia/monocytes using two-photon microscopy. Quantitative analysis revealed an early marked increase in microglial/monocytes density that is associated with an increase in the extension of the lesion measured using diffusion MRI. Morphological examination of microglia/monocytes somata at the lesion site revealed a significant increase in their surface area and volume as early as 72 hours post-injury. Time-course analysis showed differential microglial/monocytes response rostral and caudal to the lesion site. Microglia/monocytes showed a decrease in reactivity over time caudal to the lesion site, but an increase was observed rostrally. Direct comparison of microglia / monocytes morphology, obtained through multiphoton, and the longitudinal apparent diffusion coefficient (ADC), measured with diffusion MRI, highlighted that axonal integrity does not correlate with the density of microglia/monocytes or their somata morphology. We emphasize that differential microglial/monocytes reactivity rostral and caudal to the lesion site may thus coincide, at least partially, with reported temporal differences in debris clearance. Our study demonstrates that the combination of ex vivo diffusion MRI and two-photon microscopy may be used to follow structural tissue alteration. Lesion extension coincides with microglia/monocytes density; however, a direct relationship between ADC and microglia/monocytes density and morphology was not observed. We highlighted a differential rostro-caudal microglia/monocytes reactivity that may correspond to a temporal difference in debris clearance and axonal integrity. Thus, potential therapeutic strategies targeting microglia/monocytes after SCI may need to be adjusted not only with the time after injury but also relative to the location to the lesion site.

Background: Neurons have intrinsic capability to regenerate after lesion, though not spontaneously. Spinal cord injury (SCI) causes permanent neurological impairments partly due to formation of a glial scar that is composed of astrocytes and microglia. Astrocytes play both beneficial and detrimental roles on axonal re-growth, however, their precise role after SCI is currently under debate., Methods: We analyzed molecular changes in astrocytes at multiple stages after two SCI severities using cell-specific transcriptomic analyses., Results: We demonstrate that astrocyte response after injury depends on both time after injury and lesion severity. We then establish that injury induces an autologous astroglial transdifferentiation where over 10 % of astrocytes express classical neuronal progenitor markers including βIII-tubulin and doublecortin with typical immature neuronal morphology. Lineage tracing confirmed that the origin of these astrocytes is resident mature, rather than newly formed astrocytes. Astrocyte-derived neuronal progenitors subsequently express GABAergic, but not glutamatergic-specific markers. Furthermore, we have identified the neural stem cell marker fibroblast growth factor receptor 4 (Fgfr4) as a potential autologous modulator of astrocytic transdifferentiation following SCI. Finally, we establish that astroglial transdifferentiation into neuronal progenitors starts as early as 72 h and continues to a lower degrees up to 6 weeks post-lesion., Conclusion: We thus demonstrate for the first time autologous injury-induced astroglial conversion towards neuronal lineage that may represent a therapeutic strategy to replace neuronal loss and improve functional outcomes after central nervous system injury.

Laser scanning microscopes combining a femtosecond Ti:sapphire laser and an optical parametric oscillator (OPO) to duplicate the laser line have become available for biologists. These systems are primarily designed for multi-channel two-photon fluorescence microscopy. However, without any modification, complementary non-linear optical microscopy such as second-harmonic generation (SHG) or third harmonic generation (THG) can also be performed with this set-up, allowing label-free imaging of structured molecules or aqueous medium-lipid interfaces. These techniques are well suited for in-vivo observation, but are limited in chemical specificity. Chemically selective imaging can be obtained from inherent vibration signals based on Raman scattering. Confocal Raman microscopy provides 3D spatial resolution, but it requires high average power and long acquisition time. To overcome these difficulties, recent advances in laser technology have permitted the development of nonlinear optical vibrational microscopy, in particular coherent anti-Stokes Raman scattering (CARS). CARS microscopy has therefore emerged as a powerful tool for biological and live cell imaging, by chemically mapping lipids (via C-H stretch vibration), water (via O-H stretch vibrations), proteins or DNA. In this work, we describe the implementation of the CARS technique on a standard OPO-coupled multiphoton laser scanning microscope. It is based on the in-time synchronization of the two laser lines by adjusting the length of one of the laser beam path. We present a step-by-step implementation of this technique on an existing multiphoton system. A basic background in experimental optics is helpful and the presented system does not require expensive supplementary equipment. We also illustrate CARS imaging obtained on myelin sheaths of sciatic nerve of rodent, and we show that this imaging can be performed simultaneously with other nonlinear optical imaging, such as standard two-photon fluorescence technique and second-harmonic generation.

The effect of a 645 nm Light Emitting Diode (LED) light irradiation on the neurite growth velocity of adult Dorsal Root Ganglion (DRG) neurons with peripheral axon injury 4-10 days before plating and without previous injury was investigated. The real amount of light reaching the neurons was calculated by taking into account the optical characteristics of the light source and of media in the light path. The knowledge of these parameters is essential to be able to compare results of the literature and a way to reduce inconsistencies. We found that 4 min irradiation of a mean irradiance of 11.3 mW/cm(2) (corresponding to an actual irradiance reaching the neurons of 83 mW/cm(2)) induced a 1.6-fold neurite growth acceleration on non-injured neurons and on axotomized neurons. Although the axotomized neurons were naturally already in a rapid regeneration process, an enhancement was found to occur while irradiating with the LED light, which may be promising for therapy applications. Dorsal Root Ganglion neurons (A) without previous injury and (B) subjected to a conditioning injury., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Mitochondrial activity is central to tissue homeostasis. Mitochondria dysfunction constitutes a hallmark of many genetic diseases and plays a key role in tumor progression. The essential role of mitochondria, added to their recently documented capacity to transfer from cell to cell, obviously contributes to their current interest. However, determining the proper role of mitochondria in defined biological contexts was hampered by the lack of suitable experimental tools. We designed a protocol (MitoCeption) to directly and quantitatively transfer mitochondria, isolated from cell type A, to recipient cell type B. We validated and quantified the effective mitochondria transfer by imaging, fluorescence-activated cell sorting (FACS) and mitochondrial DNA analysis. We show that the transfer of minute amounts of mesenchymal stem/stromal cell (MSC) mitochondria to cancer cells, a process otherwise occurring naturally in coculture, results in cancer cell enhanced oxidative phosphorylation (OXPHOS) activity and favors cancer cell proliferation and invasion. The MitoCeption technique, which can be applied to different cell systems, will therefore be a method of choice to analyze the metabolic modifications induced by exogenous mitochondria in host cells.

For many years, a great deal of interest has been focusing on the optimization of peptide presentation by dendritic cells (DCs) using peptide-encapsulated particles, in order to enhance the immune response. Nowadays, DCs are also known to be involved in peripheral tolerance, inducing anergy or regulatory T lymphocytes. To preserve the plasticity of DCs, we formulated non-cytotoxic pH-sensitive polyion complex micelles based on an original tripartite association of polymethacrylic acid-b-polyethylene oxide, poly-L-lysine and fluorescent-peptide: OVAFITC peptide, as a model drug. We demonstrated that the OVAFITC peptide was successfully entrapped into the micelles, released into DC endosomes thanks to the pH-sensitivity property of the micelles, and efficiently loaded onto MHC class II molecules. The phenotype as well as the cytokinic secretion profile of the mature and immature DCs loaded with peptide-encapsulated micelles was unaltered by the tripartite polyion micelles. The efficient loading of the peptide by immature and mature DCs was shown by the in vitro proliferation of OVA-specific transgenic T cells. Therefore, the present results show that the tripartite polyion complex micelles can be used as efficient peptide vectors immunogically inert for ex vivo DCs engineering without modifying their intrinsic immune plasticity., (Copyright © 2011 Elsevier B.V. All rights reserved.)

CCR6 is a chemokine receptor that is expressed at the cell surface of Th17 cells, an IL-17- and IL-22-secreting population of CD4(+) T cells with antipathogenic, as well as inflammatory, properties. In the current study, we have determined the involvement of CCR6 in human Th17 lymphocyte migration toward inflamed tissue by analyzing the capacity of its ligands to induce arrest of these cells onto inflamed endothelium in vitro under flow conditions. We show that polarized, in situ-differentiated, skin-derived Th17 clones activated via the TCR-CD3 complex produce CCL20 in addition to IL-17 and IL-22. The latter cytokines induce, in a synergic fashion, the production of human β-defensin (hBD)-2, but neither hBD-1 nor hBD-3, by epidermal keratinocytes. Both CCL20 and hBD-2 are capable of inducing the arrest of Th17 cells, but not Th1 or Th2 cells, on HUVEC in an CD54-dependent manner that is CCR6 specific and independent from the expression of CXCR4, reported to be an alternative receptor for hBD-2. In addition, Ag-specific activation induces a transient loss of CCR6 expression, both at the transcriptional and protein level, which occurs with slow kinetics and is not due to endogenous CCL20-mediated internalization of CCR6. Together, these results indicate that Ag-specific activation will initially contribute to CCR6-mediated Th17 cell trafficking toward and sequestration in inflamed tissue, but that it eventually results in a transitory state of nonresponsiveness to further stimulation of these cells with CCR6 ligands, thus permitting their subsequent migration out of the inflamed site.

Cell penetrating peptides constitute a potent approach to overcome the limitations of in vivo siRNA delivery. We recently proposed a peptide-based nanoparticle system, CADY, for efficient delivery of siRNA into numerous cell lines. CADY is a secondary amphipathic peptide that forms stable complexes with siRNA thereby improving both their cellular uptake and biological response. With the aim of understanding the cellular uptake mechanism of CADY:siRNA complexes, we have combined biochemical, confocal and electron microscopy approaches. In the present work, we provide evidence that the major route for CADY:siRNA cellular uptake involves direct translocation through the membrane but not the endosomal pathway. We have demonstrated that CADY:siRNA complexes do not colocalize with most endosomal markers and remain fully active in the presence of inhibitors of the endosomal pathway. Moreover, neither electrostatic interactions with cell surface heparan sulphates nor membrane potential are essential for CADY:siRNA cell entry. In contrast, we have shown that CADY:siRNA complexes clearly induce a transient cell membrane permeabilization, which is rapidly restored by cell membrane fluidity. Therefore, we propose that direct translocation is the major gate for cell entry of CADY:siRNA complexes. Membrane perturbation and uptake are driven mainly by the ability of CADY to interact with phospholipids within the cell membrane, followed by rapid localization of the complex in the cytoplasm, without affecting cell integrity or viability.

Eukaryotic cells harbor a small multiploid mitochondrial genome, organized in nucleoids spread within the mitochondrial network. Maintenance and distribution of mitochondrial DNA (mtDNA) are essential for energy metabolism, mitochondrial lineage in primordial germ cells, and to prevent mtDNA instability, which leads to many debilitating human diseases. Mounting evidence suggests that the actors of the mitochondrial network dynamics, among which is the intramitochondrial dynamin OPA1, might be involved in these processes. Here, using siRNAs specific to OPA1 alternate spliced exons, we evidenced that silencing of the OPA1 variants including exon 4b leads to mtDNA depletion, secondary to inhibition of mtDNA replication, and to marked alteration of mtDNA distribution in nucleoid and nucleoid distribution throughout the mitochondrial network. We demonstrate that a small hydrophobic 10-kDa peptide generated by cleavage of the OPA1-exon4b isoform is responsible for this process and show that this peptide is embedded in the inner membrane and colocalizes and coimmunoprecipitates with nucleoid components. We propose a novel synthetic model in which a peptide, including two trans-membrane domains derived from the N terminus of the OPA1-exon4b isoform in vertebrates or from its ortholog in lower eukaryotes, might contribute to nucleoid attachment to the inner mitochondrial membrane and promotes mtDNA replication and distribution. Thus, this study places OPA1 as a direct actor in the maintenance of mitochondrial genome integrity.

Low-threshold mechanoreceptor neurons (LTMs) of the dorsal root ganglia (DRG) are essential for touch sensation. They form highly specialized terminations in the skin and display stereotyped projections in the spinal cord. Functionally defined LTMs depend on neurotrophin signaling for their postnatal survival and functioning, but how these neurons arise during development is unknown. Here, we show that specific types of LTMs can be identified shortly after DRG genesis by unique expression of the MafA transcription factor, the Ret receptor and coreceptor GFRalpha2, and find that their specification is Ngn2 dependent. In mice lacking Ret, these LTMs display early differentiation defects, as revealed by reduced MafA expression, and at later stages their central and peripheral projections are compromised. Moreover, in MafA mutants, a discrete subset of LTMs display altered expression of neurotrophic factor receptors. Our results provide evidence that genetic interactions involving Ret and MafA progressively promote the differentiation and diversification of LTMs., (2009 Elsevier Inc. All rights reserved.)

The etiology of benign paroxysmal positional vertigo (BPPV) remains obscure in many cases and women are affected more often than men. A recent prospective study, performed in women >50 years of age suffering from recurrent BPPV, showed associated osteopenia or osteoporosis in a large percentage of these patients. These results suggested the possible relationship between recurrent BPPV and a decreased fixation of calcium in bone in women >50 years. To test this hypothesis, an experimental study was performed in adult female rats. Utricular otoconia of female rats in which osteopenia/osteoporosis was induced by bilateral ovariectomy (OVX) were compared to those of sham-operated adult females rats (SHAM), as control group. FIRST STUDY: The morphology of theutricles of OVX and SHAM rats was analyzed with scanning electron microscopy. In osteopenic/osteoporotic rats, the density of otoconia (i.e. the number of otoconia per unit area) was decreased (p = 0.036)and their size was increased (p = 0.036) compared to the control group. SECOND STUDY: To test the role of calcium turnover in such morphological changes, utricular otoconia of 2 other groups of OVX and SHAM rats, previously injected with calcein subcutaneously, were examined by conventional and epifluorescence microscopy. In epifluorescence microscopy, labeling with calcein showed no significant fluorescence in either group. This finding was interpreted as a lack of external calcium turnover into otoconia of adult female rats. The ultrastructural modifications of otoconia in osteopenic/osteoporotic female adult rats as well as the role of estrogenic receptors in the inner ear are discussed. The possible pathophysiological mechanisms which support the relationship between recurrent BPPV in women and the disturbance of the calcium metabolism of osteopenia/osteoporosis are debated., (Copyright 2008 S. Karger AG, Basel.)

In addition to its inhibitory action, reports have shown that, in sensory neurons, GABA can be responsible for excitatory effects leading to painful behavior. The cellular mechanisms for these excitatory effects remain largely unknown. Although the high intracellular chloride concentration allows GABA(A) receptor activation to depolarize all adult sensory neurons, we show that GABA, acting through GABA(A) receptors, can generate, in vitro, action potential and intracellular Ca(2+) increase only in a subset of neurons expressing a prominent T-type Ca(2+) current. When recorded from Cav3.2(-/-) mice, T-type Ca(2+) current was totally abolished in this morphologically identified subset of neurons and GABA(A) receptors activation did not induce electrical activity nor intracellular Ca(2+) increase. In addition to gene inhibition, pharmacological analysis of Ca(2+) channel subunits shows the amplifying role of T-current in GABA(A) current-induced membrane depolarization and the involvement of both T-current and high voltage activated Ca(2+) current in GABA(A)-induced intracellular Ca(2+) increase. Altogether, these data establish that the Cav3.2/alpha1H, T-current is responsible for GABA-induced cell excitability and intracellular Ca(2+) increase. Our results reveal a positive cross-talk between T-channel and GABA(A) receptor in adult sensory neurons and indicate that Cav3.2/alpha1H, T-type Ca(2+) channel may be the molecular determinant for excitatory effects of GABA in peripheral somatosensory system.

Functional NMDA and AMPA ionotropic glutamate receptors are expressed in embryonic hippocampal glutamatergic pyramidal neurons prior to synapse formation but their function and mechanisms of action are still unclear. At the same time, these neurons develop their calbindin-D(28k) phenotype through an activity-dependent NT-3 autocrine loop. Using single-neuron microcultures, we show here that immature pyramidal neurons spontaneously secreted glutamate and that chronic blockade of either NMDA or AMPA receptors down-regulated the number of calbindin-D(28k)-positive pyramidal neurons without affecting neuronal survival. This antagonistic effect of glutamate ionotropic receptors was mimicked by anti-TrkC antibodies and reversed by the application of NT-3. Similar results were obtained in ex vivo embryonic hippocampal slice cultures. Moreover, glutamate receptor blockade inhibited the generation of spontaneous sodium-driven action potentials which, in turn, regulate both the endogenous secretion of NT-3 and the calbindin-D(28k) phenotype acquisition. Altogether, these results suggest an unexpected role for glutamate in the development of the physiological and biochemical properties of hippocampal pyramidal neurons and support the idea that glutamate may underlie an activity-dependent mode of differentiation prior to synapse formation.

We report the case of a patient with severe partial epilepsy associated with a focal rolandic, pathologically proven, cortical dysplasia. By measuring intracellular calcium concentrations, functional antiglial non-glutamate receptor 3 (GluR3) autoantibodies were identified in the serum of this patient. Antineuronal autoantibodies, which interfere with GluR3-receptor function, also were detected. This observation provides new clues about the involvement of immunologic mechanisms in epileptic disorders.

Different subsets of dorsal root ganglion (DRG) mechanoreceptors transduce low- and high-intensity mechanical stimuli. It was shown recently that, in vivo, neurotrophin-4 (NT-4)-dependent D-hair mechanoreceptors specifically express a voltage-activated T-type calcium channel (Ca(v)3.2) that may be required for their mechanoreceptive function. Here we show that D-hair mechanoreceptors can be identified in vitro by a rosette-like morphology in the presence of NT-4 and that these rosette neurons are almost all absent in DRG cultures taken from NT-4 knock-out mice. In vitro identification of the D-hair mechanoreceptor allowed us to explore the electrophysiological properties of these cells. We demonstrate that the T-type Ca(v)3.2 channel induced slow membrane depolarization that contributes to lower the voltage threshold for action potential generation and controls spike latency after stimulation of D-hair mechanoreceptors. Indeed, the properties of the T-type amplifier are particularly well suited to explain the high sensitivity of D-hair mechanoreceptors to slowly moving stimuli.

By regulating voltage-dependent Ca2+ influx and intracellular Ca2+ homeostasis, electrical activity plays a central role in motoneuron development. Dissociated cultures of purified embryonic rat motoneurons were used to explore the molecular mechanisms by which Ca2+ influx control [Ca2+]i transients in these neurons. Thapsigargin (250 nm) and cyclopiazonic acid (10 micro m), which deplete Ca2+ stores in the endoplasmic reticulum, decrease by 30% the depolarization-induced [Ca2+]i transients in motoneurons without affecting voltage-activated calcium currents. This thapsigargin-sensitive intracellular Ca2+ pool differs from other previous described Ca2+ stores that are sensitive to ryanodine or caffeine, inositol triphosphate, insulin and from mitochondrial Ca2+ pools. Thapsigargin affected the Cav2.1 P-type Ca2+ channel component of the depolarization-induced [Ca2+]i transient in motoneurons but spared [Ca2+]i transient induced by Cav1 L-type and Cav2.2 N-type Ca2+ channel components, suggesting a close functional relationship between Cav2.1 subunit and this unique thapsigargin-sensitive Ca2+ store. Altogether the present results demonstrate a new pathway, used by embryonic motoneurons, to regulate Ca2+ signalling through voltage-activated (Cav2.1) Ca2+ channels.

Whole cell patch-clamp recordings of calcium-activated chloride current [ICl(Ca)] were made from adult sensory neurons of naive and axotomized mouse L4-L6 lumbar dorsal root ganglia after 1 day of culture in vitro. A basal ICl(Ca) was specifically expressed in a subset of naive medium-diameter neurons (30-40 microm). Prior nerve injury, induced by sciatic nerve transection 5 days before experiments, increased both ICl(Ca) amplitude and its expression in medium-diameter neurons. Moreover, nerve injury also induced ICl(Ca) expression in a new subpopulation of neurons, the large-diameter neurons (40-50 microm). Small-diameter neurons (inferior to 30 microm) never expressed ICl(Ca). Regulated ICl(Ca) expression was strongly correlated with injury-induced regenerative growth of sensory neurons in vitro and nerve regeneration in vivo. Cell culture on a substrate not permissive for growth, D,L-polyornithine, prevented both elongation growth and ICl(Ca) expression in axotomized neurons. Regenerative growth and the induction of ICl(Ca) expression take place 2 days after injury, peak after 5 days of conditioning in vivo, slowly declining thereafter to control values. The selective expression of ICl(Ca) within medium- and large-diameter neurons conditioned for rapid, efficient growth suggests that these channels play a specific role in postinjury behavior of sensory neuron subpopulations such as neuropathic pain and/or axonal regeneration.

Neurotrophin-3 (NT-3), its cognate receptor trkC, and voltage-gated calcium channels are coexpressed by embryonic pyramidal neurons before target contact, but their functions at this stage of development are still unclear. We show here that, in vitro, anti-NT-3 and anti-trkC antibodies blocked the increase, and NT-3 reversed the decrease in the number of calbindin-D(28k)-positive pyramidal neurons induced by, respectively, calcium channel activations and blockades. Similar results were obtained with single-neuron microcultures. In addition, voltage-gated calcium channel inhibition downregulates the extracellular levels of NT-3 in high-density cultures. Moreover, electrophysiological experiments in single-cell cultures reveal a tetrodotoxin-sensitive spontaneous electrical activity allowing voltage-gated calcium channel activation. The mouse NT-3 (-/-) mutation decreases by 40% the number of developing calbindin-D(28k)-positive pyramidal neurons, without affecting neuronal survival, both in vitro and in vivo. Thus, present results strongly support that an activity-dependent autocrine NT-3 loop provides a local, intrinsic mechanism by which, before target contact, hippocampal pyramidal-like neurons may regulate their own differentiation, a role that may be important during early CNS differentiation or after adult target disruption.

Cultured immature hippocampal neurons from embryonic 17-day-old rats were used to explore activity-dependent regulation of neuronal phenotype differentiation in the developing hippocampus. The calbindin-D28k phenotype of the pyramidal neurons appeared during the first 6 days in culture, and was expressed by 12% of the cells on day 6. Daily stimulation with 50 mM KCl during the first 5 days in vitro increased the number of calbindin-D28k-positive pyramidal neurons without affecting neuronal survival. This effect was prevented by buffering extracellular Ca2+. Omega-agatoxin-IVA-sensitive Q-type and nitrendipine-sensitive L-type voltage-gated Ca2+ channels (VGCCs) carried Ca2+ currents and Ca2+ influx in immature pyramidal neurons at somata level. Blockade of these channels inhibited calbindin-D28k phenotype induced by 50 mM KCl. Conversely, glutamate-activated Ca2+ channel antagonists did not affect the KCl-induced calbindin-D28k phenotype. Chronic blockade of Q- and/or L-type VGCCs downregulated the normal calbindin-D28k development of immature pyramidal neurons without affecting neuronal survival, the somatic area of pyramidal neurons or the number of GABAergic-positive (gamma-aminobutyric acid) interneurons. However, at later developmental stages, Q-type VGCCs lost their ability to control Ca2+ influx at somata level, and both Q- and L-type VGCCs failed to regulate calbindin-D28k phenotype. These results suggest that Q-type channels, which have been predominantly associated with neurotransmitter release in adult brain, transiently act in synergy with L-type VGCCs to direct early neuronal differentiation of hippocampal pyramidal neurons before the establishment of their synaptic circuits.