Macrophage polarization in vitro and in vivo modified by contact with fragmented chitosan hydrogel.

We have previously shown that implantation of a fragmented chitosan hydrogel suspension (chitosan-FPHS) into a traumatic spinal cord lesion in adult rats led to significant axon regrowth and functional recovery, which was associated to a modulation of inflammation. Using an in vitro culture system, we show here that polarization of bone marrow-derived macrophages is indeed modified by direct contact with chitosan-FPHS. Reducing the degree of acetylation (DA) and raising the concentration of chitosan (Cp, from 1.5% to 3%), favors macrophage polarization toward anti-inflammatory subtypes. These latter also migrate and adhere efficiently on low, but not high DA chitosan-FPHS, both in vitro and in vivo, while inflammatory macrophages rarely invade a chitosan-FPHS implant in vivo, no matter the DA. Our in vitro model setup should prove a valuable tool for screening diverse biomaterial formulations and combinations thereof for their inflammatory potential prior to implantation in vivo.

AAV2/9-mediated silencing of PMP22 prevents the development of pathological features in a rat model of Charcot-Marie-Tooth disease 1 A.

Charcot-Marie-Tooth disease 1 A (CMT1A) results from a duplication of the PMP22 gene in Schwann cells and a deficit of myelination in peripheral nerves. Patients with CMT1A have reduced nerve conduction velocity, muscle wasting, hand and foot deformations and foot drop walking. Here, we evaluate the safety and efficacy of recombinant adeno-associated viral vector serotype 9 (AAV2/9) expressing GFP and shRNAs targeting Pmp22 mRNA in animal models of Charcot-Marie-Tooth disease 1 A. Intra-nerve delivery of AAV2/9 in the sciatic nerve allowed widespread transgene expression in resident myelinating Schwann cells in mice, rats and non-human primates. A bilateral treatment restore expression levels of PMP22 comparable to wild-type conditions, resulting in increased myelination and prevention of motor and sensory impairments over a twelve-months period in a rat model of CMT1A. We observed limited off-target transduction and immune response using the intra-nerve delivery route. A combination of previously characterized human skin biomarkers is able to discriminate between treated and untreated animals, indicating their potential use as part of outcome measures.

Microglia control the glycinergic but not the GABAergic synapses via prostaglandin E2 in the spinal cord.

Microglia control excitatory synapses, but their role in inhibitory neurotransmission has been less well characterized. Herein, we show that microglia control the strength of glycinergic but not GABAergic synapses via modulation of the diffusion dynamics and synaptic trapping of glycine (GlyR) but not GABAA receptors. We further demonstrate that microglia regulate the activity-dependent plasticity of glycinergic synapses by tuning the GlyR diffusion trap. This microglia-synapse cross talk requires production of prostaglandin E2 by microglia, leading to the activation of neuronal EP2 receptors and cyclic adenosine monophosphate-dependent protein kinase. Thus, we now provide a link between microglial activation and synaptic dysfunctions, which are common early features of many brain diseases.

Ensaio sobre a melancolia: suas origens, sua dialética, seus caminhos tortuosos e seu destino inelutável / Essay on melancholy: its origins, dialectic, winding paths, and ineluctable destiny / Ensayo sobre la melancolía: sus orígenes, su dialéctica, sus caminos tortuosos y su destino ineluctable

Inspirada pela leitura do filósofo Giorgio Agamben, a autora faz uma reflexão sobre a genealogia da melancolia, a partir de referências patrísticas da época medieval - que a designavam "acidia" -, de associações com a cosmologia ocidental e de distintas teorias no decorrer da história, até suas expressões na atualidade. O cerne do trabalho respalda-se em Freud, em "Luto e melancolia", e na leitura peculiar de Agamben, que, ao cotejar a interpretação psicanalítica do mecanismo da melancolia com o complexo humoral saturnino, destaca dois elementos descritos na acidia: o recesso do objeto e o retirar-se em si mesmo da intenção contemplativa. A autora aborda os conceitos de relações de objeto, fetichismo e narcisismo para esclarecer a dialética das relações, sua tortuosa intenção em busca do objeto e a natureza melancólica que subjaz na sombra desses processos.

Inspired by the work of the Italian philosopher Giorgio Agamben, the author ponders over the genealogy of melancholy, starting from patristics references in the Middle Ages - when it was termed "acedia" -, passing through associations with western cosmology and other theories throughout history, to its current expressions. The core of this paper is based on Freud's work "Mourning and melancholy" and on the peculiar review made by Giorgio Agamben. By comparing psychoanalytic understanding of the mechanism of melancholy with the saturnine humoral complex, Agamben emphasizes two elements of acedia: recess of the object and a self-alienation from the contemplative intention. The author also writes about concepts of object relations, fetichism and narcissism, in order to clarify the relational dialectic, its tortuous intent to pursue the object, and the melancholic nature underlying these processes.

Inspirada por las obras del filósofo Giorgio Agamben, la autora hace una reflexión sobre la genealogía de la melancolía, a partir de referencias patrísticas de la época medieval - que la denominaban "acedia" -, asociaciones con la cosmología occidental y distintas teorías surgidas en el transcurso de la historia, hasta llegar a sus manifestaciones actuales. Este trabajo se respalda en Freud - "Luto y melancolía" - y en la particular lectura de Agamben, que, al cotejar la interpretación psicoanalítica del mecanismo de la melancolía con el complejo humoral saturnino, destaca dos elementos descritos en la acedia: el receso del objeto y el retirarse en sí mismo de la intención contemplativa. La autora aborda los conceptos de las relaciones de objeto, del fetichismo y del narcisismo para aclarar la dialéctica de las relaciones, su tortuosa intención en busca del objeto y la naturaleza melancólica que subyaz en la sombra de esos procesos.

Giant scaffolding protein AHNAK1 interacts with ß-dystroglycan and controls motility and mechanical properties of Schwann cells.

The profound morphofunctional changes that Schwann cells (SCs) undergo during their migration and elongation on axons, as well as during axon sorting, ensheathment, and myelination, require their close interaction with the surrounding laminin-rich basal lamina. In contrast to myelinating central nervous system glia, SCs strongly and constitutively express the giant scaffolding protein AHNAK1, localized essentially underneath the outer, abaxonal plasma membrane. Using electron microscopy, we show here that in the sciatic nerve of ahnak1(-) (/) (-) mice the ultrastructure of myelinated, and unmyelinated (Remak) fibers is affected. The major SC laminin receptor ß-dystroglycan co-immunoprecipitates with AHNAK1 shows reduced expression in ahnak1(-) (/) (-) SCs, and is no longer detectable in Cajal bands on myelinated fibers in ahnak1(-) (/) (-) sciatic nerve. Reduced migration velocity in a scratch wound assay of purified ahnak1(-) (/) (-) primary SCs cultured on a laminin substrate indicated a function of AHNAK1 in SC motility. This was corroborated by atomic force microscopy measurements, which revealed a greater mechanical rigidity of shaft and leading tip of ahnak1(-) (/) (-) SC processes. Internodal lengths of large fibers are decreased in ahnak1(-) (/) (-) sciatic nerve, and longitudinal extension of myelin segments is even more strongly reduced after acute knockdown of AHNAK1 in SCs of developing sciatic nerve. Together, our results suggest that by interfering in the cross-talk between the transmembrane form of the laminin receptor dystroglycan and F-actin, AHNAK1 influences the cytoskeleton organization of SCs, and thus plays a role in the regulation of their morphology and motility and lastly, the myelination process.

Extensive structural remodeling of the injured spinal cord revealed by phosphorylated MAP1B in sprouting axons and degenerating neurons.

Spinal cord injury (SCI) results in loss of sensory and motor function because injured axons do not regenerate and neurons that die are not replaced. Nevertheless, there is evidence for spontaneous reorganization of spared pathways (i.e. sprouting) that could be exploited to improve functional recovery. The extent of morphological remodeling after spinal cord injury is, however, not understood. We have previously shown that a phosphorylated form of microtubule-associated protein-1B, MAP1B-P, is expressed by growing axons, but is detected in intact adult SC in fibers exhibiting a somatotopic distribution of myelinated sensory fibers. We now demonstrate that after adult SCI, MAP1B-P is up-regulated in other classes of axons. We used immunohistochemistry to show changing levels and distributions of MAP1B-P after a right thoracic hemisection of adult rat spinal cord. MAP1B-P labeling suggests rearrangements of the axonal circuitry that go well beyond previous descriptions. MAP1B-P-positive fibers are present in ectopic locations in gray matter in both dorsal and ventral horns and around the central canal. Double staining reveals that primary sensory and descending serotonergic and corticospinal axons are MAP1B-P positive. In white matter, high MAP1B-P expression is found on terminal enlargements near the injury, reflecting retraction of transected axons. MAP1B-P also accumulates in pre-apoptotic neuronal somata axotomized by the lesion, indicating association of MAP1B-P not only with axon extension and retraction, but also with neuronal degeneration. Finally, we provide evidence that MAP1B phosphorylation is correlated with activation of JNK MAP-kinase, providing a step towards unraveling the mechanisms of regulation of this plasticity-related cytoskeletal protein.

Spinal cord injury-induced up-regulation of AHNAK, expressed in cells delineating cystic cavities, and associated with neoangiogenesis.

To investigate the molecular basis for the poor regenerative capacity of the mammalian central nervous system (CNS) after injury, we searched for genes whose expression was affected by an adult rat spinal cord hemi-section. Differential screening of a rat spinal cord expression library was performed using polyclonal antibodies raised against lesioned spinal cord tissue. A striking overexpression was found for ahnak, encoding a 700-kDa protein, in normal CNS present only in the blood-brain barrier (BBB) forming vascular endothelial cells. Indeed, very early after spinal cord injury (SCI), high levels of membrane-associated AHNAK are observed on non-neuronal cells invading the lesion site. With time, AHNAK distribution spreads rostrally and caudally concomitant with the process of tissue inflammation and axon degeneration, delineating the interior surface of cystic cavities, mainly in front of barrier-forming astrocytes. Strong overexpression is also observed on vascular endothelial cells reacting to BBB breakdown. Based on our detailed analysis of its spatiotemporal and cellular expression, and its previously described function in BBB, we suggest that AHNAK expression is associated with cell types displaying tissue-protective barrier properties. Our study may thus contribute to the elucidation of the precise molecular and cellular events that eventually render traumatic spinal cord tissue non-permissive for regeneration.

Mash1 specifies neurons and oligodendrocytes in the postnatal brain.

Progenitors in the telencephalic subventricular zone (SVZ) remain mitotically active throughout life, and produce different cell types at embryonic, postnatal and adult stages. Here we show that Mash1, an important proneural gene in the embryonic telencephalon, is broadly expressed in the postnatal SVZ, in progenitors for both neuronal and oligodendrocyte lineages. Moreover, Mash1 is required at birth for the generation of a large fraction of neuronal and oligodendrocyte precursors from the olfactory bulb. Clonal analysis in culture and transplantation experiments in postnatal brain demonstrate that this phenotype reflects a cell-autonomous function of Mash1 in specification of these two lineages. The conservation of Mash1 function in the postnatal SVZ suggests that the same transcription mechanisms operate throughout life to specify cell fates in this structure, and that the profound changes in the cell types produced reflect changes in the signalling environment of the SVZ.