Mitigating the Functional Deficit after Neurotoxic Motoneuronal Loss by an Inhibitor of Mitochondrial Fission.

Amyotrophic lateral sclerosis (ALS) is an extremely complex neurodegenerative disease involving different cell types, but motoneuronal loss represents its main pathological feature. Moreover, compensatory plastic changes taking place in parallel to neurodegeneration are likely to affect the timing of ALS onset and progression and, interestingly, they might represent a promising target for disease-modifying treatments. Therefore, a simplified animal model mimicking motoneuronal loss without the other pathological aspects of ALS has been established by means of intramuscular injection of cholera toxin-B saporin (CTB-Sap), which is a targeted neurotoxin able to kill motoneurons by retrograde suicide transport. Previous studies employing the mouse CTB-Sap model have proven that spontaneous motor recovery is possible after a subtotal removal of a spinal motoneuronal pool. Although these kinds of plastic changes are not enough to counteract the functional effects of the progressive motoneuron degeneration, it would nevertheless represent a promising target for treatments aiming to postpone ALS onset and/or delay disease progression. Herein, the mouse CTB-Sap model has been used to test the efficacy of mitochondrial division inhibitor 1 (Mdivi-1) as a tool to counteract the CTB-Sap toxicity and/or to promote neuroplasticity. The homeostasis of mitochondrial fission/fusion dynamics is indeed important for cell integrity, and it could be affected during neurodegeneration. Lesioned mice were treated with Mdivi-1 and then examined by a series of behavioral test and histological analyses. The results have shown that the drug may be capable of reducing functional deficits after the lesion and promoting synaptic plasticity and neuroprotection, thus representing a putative translational approach for motoneuron disorders.

Synaptic Dysfunction and Plasticity in Amyotrophic Lateral Sclerosis.

Recent evidence has supported the hypothesis that amyotrophic lateral sclerosis (ALS) is a multi-step disease, as the onset of symptoms occurs after sequential exposure to a defined number of risk factors. Despite the lack of precise identification of these disease determinants, it is known that genetic mutations may contribute to one or more of the steps leading to ALS onset, the remaining being linked to environmental factors and lifestyle. It also appears evident that compensatory plastic changes taking place at all levels of the nervous system during ALS etiopathogenesis may likely counteract the functional effects of neurodegeneration and affect the timing of disease onset and progression. Functional and structural events of synaptic plasticity probably represent the main mechanisms underlying this adaptive capability, causing a significant, although partial and transient, resiliency of the nervous system affected by a neurodegenerative disease. On the other hand, the failure of synaptic functions and plasticity may be part of the pathological process. The aim of this review was to summarize what it is known today about the controversial involvement of synapses in ALS etiopathogenesis, and an analysis of the literature, although not exhaustive, confirmed that synaptic dysfunction is an early pathogenetic process in ALS. Moreover, it appears that adequate modulation of structural and functional synaptic plasticity may likely support function sparing and delay disease progression.

Hippocampal Noradrenaline Is a Positive Regulator of Spatial Working Memory and Neurogenesis in the Rat.

Loss of noradrenaline (NA)-rich afferents from the Locus Coeruleus (LC) ascending to the hippocampal formation has been reported to dramatically affect distinct aspects of cognitive function, in addition to reducing the proliferation of neural progenitors in the dentate gyrus. Here, the hypothesis that reinstating hippocampal noradrenergic neurotransmission with transplanted LC-derived neuroblasts would concurrently normalize both cognitive performance and adult hippocampal neurogenesis was investigated. Post-natal day (PD) 4 rats underwent selective immunolesioning of hippocampal noradrenergic afferents followed, 4 days later, by the bilateral intrahippocampal implantation of LC noradrenergic-rich or control cerebellar (CBL) neuroblasts. Starting from 4 weeks and up to about 9 months post-surgery, sensory-motor and spatial navigation abilities were evaluated, followed by post-mortem semiquantitative tissue analyses. All animals in the Control, Lesion, Noradrenergic Transplant and Control CBL Transplant groups exhibited normal sensory-motor function and were equally efficient in the reference memory version of the water maze task. By contrast, working memory abilities were seen to be consistently impaired in the Lesion-only and Control CBL-Transplanted rats, which also exhibited a virtually complete noradrenergic fiber depletion and a significant 62-65% reduction in proliferating 5-bromo-2'deoxyuridine (BrdU)-positive progenitors in the dentate gyrus. Notably, the noradrenergic reinnervation promoted by the grafted LC, but not cerebellar neuroblasts, significantly ameliorated working memory performance and reinstated a fairly normal density of proliferating progenitors. Thus, LC-derived noradrenergic inputs may act as positive regulators of hippocampus-dependent spatial working memory possibly via the concurrent maintenance of normal progenitor proliferation in the dentate gyrus.

A Meta-Analysis Study of SOD1-Mutant Mouse Models of ALS to Analyse the Determinants of Disease Onset and Progression.

A complex interaction between genetic and external factors determines the development of amyotrophic lateral sclerosis (ALS). Epidemiological studies on large patient cohorts have suggested that ALS is a multi-step disease, as symptom onset occurs only after exposure to a sequence of risk factors. Although the exact nature of these determinants remains to be clarified, it seems clear that: (i) genetic mutations may be responsible for one or more of these steps; (ii) other risk factors are probably linked to environment and/or to lifestyle, and (iii) compensatory plastic changes taking place during the ALS etiopathogenesis probably affect the timing of onset and progression of disease. Current knowledge on ALS mechanisms and therapeutic targets, derives mainly from studies involving superoxide dismutase 1 (SOD1) transgenic mice; therefore, it would be fundamental to verify whether a multi-step disease concept can also be applied to these animal models. With this aim, a meta-analysis study has been performed using a collection of primary studies (n = 137), selected according to the following criteria: (1) the studies should employ SOD1 transgenic mice; (2) the studies should entail the presence of a disease-modifying experimental manipulation; (3) the studies should make use of Kaplan-Meier plots showing the distribution of symptom onset and lifespan. Then, using a subset of this study collection (n = 94), the effects of treatments on key molecular mechanisms, as well as on the onset and progression of disease have been analysed in a large population of mice. The results are consistent with a multi-step etiopathogenesis of disease in ALS mice (including two to six steps, depending on the particular SOD1 mutation), closely resembling that observed in patient cohorts, and revealed an interesting relationship between molecular mechanisms and disease manifestation. Thus, SOD1 mouse models may be considered of high predictive value to understand the determinants of disease onset and progression, as well as to identify targets for therapeutic interventions.

Intercellular communication and ion channels in neuropathic pain chronicization.

BACKGROUND: Neuropathic pain is caused by primary lesion or dysfunction of either peripheral or central nervous system. Due to its complex pathogenesis, often related to a number of comorbidities, such as cancer, neurodegenerative and neurovascular diseases, neuropathic pain still represents an unmet clinical need, lacking long-term effective treatment and complex case-by-case approach. AIM AND METHODS: We analyzed the recent literature on the role of selective voltage-sensitive sodium, calcium and potassium permeable channels and non-selective gap junctions (GJs) and hemichannels (HCs) in establishing and maintaining chronic neuropathic conditions. We finally focussed our review on the role of extracellular microenvironment modifications induced by resident glial cells and on the recent advances in cell-to-cell and cell-to-extracellular environment communication in chronic neuropathies. CONCLUSION: In this review, we provide an update on the current knowledge of neuropathy chronicization processes with a focus on both neuronal and glial ion channels, as well as on channel-mediated intercellular communication.

Neuromuscular Plasticity in a Mouse Neurotoxic Model of Spinal Motoneuronal Loss.

Despite the relevant research efforts, the causes of amyotrophic lateral sclerosis (ALS) are still unknown and no effective cure is available. Many authors suggest that ALS is a multi-system disease caused by a network failure instead of a cell-autonomous pathology restricted to motoneurons. Although motoneuronal loss is the critical hallmark of ALS given their specific vulnerability, other cell populations, including muscle and glial cells, are involved in disease onset and progression, but unraveling their specific role and crosstalk requires further investigation. In particular, little is known about the plastic changes of the degenerating motor system. These spontaneous compensatory processes are unable to halt the disease progression, but their elucidation and possible use as a therapeutic target represents an important aim of ALS research. Genetic animal models of disease represent useful tools to validate proven hypotheses or to test potential therapies, and the conception of novel hypotheses about ALS causes or the study of pathogenic mechanisms may be advantaged by the use of relatively simple in vivo models recapitulating specific aspects of the disease, thus avoiding the inclusion of too many confounding factors in an experimental setting. Here, we used a neurotoxic model of spinal motoneuron depletion induced by injection of cholera toxin-B saporin in the gastrocnemius muscle to investigate the possible occurrence of compensatory changes in both the muscle and spinal cord. The results showed that, following the lesion, the skeletal muscle became atrophic and displayed electromyographic activity similar to that observed in ALS patients. Moreover, the changes in muscle fiber morphology were different from that observed in ALS models, thus suggesting that some muscular effects of disease may be primary effects instead of being simply caused by denervation. Notably, we found plastic changes in the surviving motoneurons that can produce a functional restoration probably similar to the compensatory changes occurring in disease. These changes could be at least partially driven by glutamatergic signaling, and astrocytes contacting the surviving motoneurons may support this process.

Clobetasol Modulates Adult Neural Stem Cell Growth via Canonical Hedgehog Pathway Activation.

Sonic hedgehog (Shh) signaling is a key pathway within the central nervous system (CNS), during both development and adulthood, and its activation via the 7-transmembrane protein Smoothened (Smo) may promote neuroprotection and restoration during neurodegenerative disorders. Shh signaling may also be activated by selected glucocorticoids such as clobetasol, fluocinonide and fluticasone, which therefore act as Smo agonists and hold potential utility for regenerative medicine. However, despite its potential role in neurodegenerative diseases, the impact of Smo-modulation induced by these glucocorticoids on adult neural stem cells (NSCs) and the underlying signaling mechanisms are not yet fully elucidated. The aim of the present study was to evaluate the effects of Smo agonists (i.e., purmorphamine) and antagonists (i.e., cyclopamine) as well as of glucocorticoids (i.e., clobetasol, fluocinonide and fluticasone) on NSCs in terms of proliferation and clonal expansion. Purmorphamine treatment significantly increased NSC proliferation and clonal expansion via GLI-Kruppel family member 1 (Gli1) nuclear translocation and such effects were prevented by cyclopamine co-treatment. Clobetasol treatment exhibited an equivalent pharmacological effect. Moreover, cellular thermal shift assay suggested that clobetasol induces the canonical Smo-dependent activation of Shh signaling, as confirmed by Gli1 nuclear translocation and also by cyclopamine co-treatment, which abolished these effects. Finally, fluocinonide and fluticasone as well as control glucocorticoids (i.e., prednisone, corticosterone and dexamethasone) showed no significant effects on NSCs proliferation and clonal expansion. In conclusion, our data suggest that Shh may represent a druggable target system to drive neuroprotection and promote restorative therapies.

MiR-19a Overexpression in FTC-133 Cell Line Induces a More De-Differentiated and Aggressive Phenotype.

In recent years, microRNAs (miRNAs) have received increasing attention for their important role in tumor initiation and progression. MiRNAs are a class of endogenous small non-coding RNAs that negatively regulate the expression of several oncogenes or tumor suppressor genes. MiR-19a, a component of the oncogenic miR-17-92 cluster, has been reported to be highly expressed only in anaplastic thyroid cancer, the most undifferentiated, aggressive and lethal form of thyroid neoplasia. In this work, we evaluated the putative contribution of miR-19a in de-differentiation and aggressiveness of thyroid tumors. To this aim, we induced miR-19a expression in the well-differentiated follicular thyroid cancer cell line and evaluated proliferation, apoptosis and gene expression profile of cancer cells. Our results showed that miR-19a overexpression stimulates cell proliferation and alters the expression profile of genes related to thyroid cell differentiation and aggressiveness. These findings not only suggest that miR-19a has a possible involvement in de-differentiation and malignancy, but also that it could represent an important prognostic indicator and a good therapeutic target for the most aggressive thyroid cancer.

Neuroplasticity and Repair in Rodent Neurotoxic Models of Spinal Motoneuron Disease.

Retrogradely transported toxins are widely used to set up protocols for selective lesioning of the nervous system. These methods could be collectively named "molecular neurosurgery" because they are able to destroy specific types of neurons by using targeted neurotoxins. Lectins such as ricin, volkensin, or modeccin and neuropeptide- or antibody-conjugated saporin represent the most effective toxins used for neuronal lesioning. Some of these specific neurotoxins could be used to induce selective depletion of spinal motoneurons. In this review, we extensively describe two rodent models of motoneuron degeneration induced by volkensin or cholera toxin-B saporin. In particular, we focus on the possible experimental use of these models to mimic neurodegenerative diseases, to dissect the molecular mechanisms of neuroplastic changes underlying the spontaneous functional recovery after motoneuron death, and finally to test different strategies of neural repair. The potential clinical applications of these approaches are also discussed.

Potential Effect of CD271 on Human Mesenchymal Stromal Cell Proliferation and Differentiation.

The Low-Affinity Nerve Growth Factor Receptor (LNGFR), also known as CD271, is a member of the tumor necrosis factor receptor superfamily. The CD271 cell surface marker defines a subset of multipotential mesenchymal stromal cells and may be used to isolate and enrich cells derived from bone marrow aspirate. In this study, we compare the proliferative and differentiation potentials of CD271+ and CD271- mesenchymal stromal cells. Mesenchymal stromal cells were isolated from bone marrow aspirate and adipose tissue by plastic adherence and positive selection. The proliferation and differentiation potentials of CD271+ and CD271- mesenchymal stromal cells were assessed by inducing osteogenic, adipogenic and chondrogenic in vitro differentiation. Compared to CD271+, CD271- mesenchymal stromal cells showed a lower proliferation rate and a decreased ability to give rise to osteocytes, adipocytes and chondrocytes. Furthermore, we observed that CD271+ mesenchymal stromal cells isolated from adipose tissue displayed a higher efficiency of proliferation and trilineage differentiation compared to CD271+ mesenchymal stromal cells isolated from bone marrow samples, although the CD271 expression levels were comparable. In conclusion, these data show that both the presence of CD271 antigen and the source of mesenchymal stromal cells represent important factors in determining the ability of the cells to proliferate and differentiate.

Beyond the Clinic Walls: Examining Radiology Technicians' Experiences in Home-Based Radiography.

In recent years, the landscape of diagnostic imaging has undergone a significant transformation with the emergence of home radiology, challenging the traditional paradigm. This shift, bringing diagnostic imaging directly to patients, has gained momentum and has been further accelerated by the global COVID-19 pandemic, highlighting the increasing importance and convenience of decentralized healthcare services. This study aims to offer a nuanced understanding of the attitudes and experiences influencing the integration of in-home radiography into contemporary healthcare practices. The research methodology involves a survey administered through Computer-Aided Web Interviewing (CAWI) tools, enabling real-time engagement with a diverse cohort of medical radiology technicians in the health domain. A second CAWI tool is submitted to experts to assess their feedback on the methodology. The survey explores key themes, including perceived advantages and challenges associated with domiciliary imaging, its impact on patient care, and the technological intricacies specific to conducting radiologic procedures outside the conventional clinical environment. Findings from a sample of 26 medical radiology technicians (drawn from a larger pool of 186 respondents) highlight a spectrum of opinions and constructive feedback. Enthusiasm is evident for the potential of domiciliary imaging to enhance patient convenience and provide a more patient-centric approach to healthcare. Simultaneously, this study suggests areas of intervention to improve the diffusion of home-based radiology. The methodology based on CAWI tools proves instrumental in the efficiency and depth of data collection, as evaluated by 16 experts from diverse professional backgrounds. The dynamic and responsive nature of this approach allows for a more allocated exploration of technicians' opinions, contributing to a comprehensive understanding of the evolving landscape of medical imaging services. Emphasis is placed on the need for national and international initiatives in the field, supported by scientific societies, to further explore the evolving landscape of teleradiology and the integration of artificial intelligence in radiology. This study encourages expansion involving other key figures in this practice, including, naturally, medical radiologists, general practitioners, medical physicists, and other stakeholders.

Reimagining Radiology: A Comprehensive Overview of Reviews at the Intersection of Mobile and Domiciliary Radiology over the Last Five Years.

(Background) Domiciliary radiology, which originated in pioneering studies in 1958, has transformed healthcare, particularly during the COVID-19 pandemic, through advancements such as miniaturization and digitization. This evolution, driven by the synergy of advanced technologies and robust data networks, reshapes the intersection of domiciliary radiology and mobile technology in healthcare delivery. (Objective) The objective of this study is to overview the reviews in this field with reference to the last five years to face the state of development and integration of this practice in the health domain. (Methods) A review was conducted on PubMed and Scopus, applying a standard checklist and a qualification process. The outcome detected 21 studies. (Key Content and Findings) The exploration of mobile and domiciliary radiology unveils a compelling and optimistic perspective. Notable strides in this dynamic field include the integration of Artificial Intelligence (AI), revolutionary applications in telemedicine, and the educational potential of mobile devices. Post-COVID-19, telemedicine advances and the influential role of AI in pediatric radiology signify significant progress. Mobile mammography units emerge as a solution for underserved women, highlighting the crucial importance of early breast cancer detection. The investigation into domiciliary radiology, especially with mobile X-ray equipment, points toward a promising frontier, prompting in-depth research for comprehensive insights into its potential benefits for diverse populations. The study also identifies limitations and suggests future exploration in various domains of mobile and domiciliary radiology. A key recommendation stresses the strategic prioritization of multi-domain technology assessment initiatives, with scientific societies' endorsement, emphasizing regulatory considerations for responsible and ethical technology integration in healthcare practices. The broader landscape of technology assessment should aim to be innovative, ethical, and aligned with societal needs and regulatory standards. (Conclusions) The dynamic state of the field is evident, with active exploration of new frontiers. This overview also provides a roadmap, urging scholars, industry players, and regulators to collectively contribute to the further integration of this technology in the health domain.

Acetylcholine and noradrenaline differentially regulate hippocampus-dependent spatial learning and memory.

Severe loss of cholinergic neurons in the basal forebrain nuclei and of noradrenergic neurons in the locus coeruleus are almost invariant histopathological hallmarks of Alzheimer's disease. However, the role of these transmitter systems in the spectrum of cognitive dysfunctions typical of the disease is still unclear, nor is it yet fully known whether do these systems interact and how. Selective ablation of either neuronal population, or both of them combined, were produced in developing animals to investigate their respective and/or concurrent contribution to spatial learning and memory, known to be severely affected in Alzheimer's disease. Single or double lesions were created in 4-8 days old rats by bilateral intraventricular infusion of two selective immunotoxins. At about 16 weeks of age, the animals underwent behavioural tests specifically designed to evaluate reference and working memory abilities, and their brains were later processed for quantitative morphological analyses. Animals with lesion to either system alone showed no significant reference memory deficits which, by contrast, were evident in the double-lesioned subjects. These animals could not adopt an efficient search strategy on a given testing day and were unable to transfer all relevant information to the next day, suggesting deficits in acquisition, storage and/or recall. Only animals with single noradrenergic or double lesions exhibited impaired working memory. Interestingly, ablation of cholinergic afferents to the hippocampus stimulated a robust ingrowth of thick fibres from the superior cervical ganglion which, however, did not appear to have contributed to the observed cognitive performance. Ascending cholinergic and noradrenergic afferents to the hippocampus and neocortex appear to be primarily involved in the regulation of different cognitive domains, but they may functionally interact, mainly at hippocampal level, for sustaining normal learning and memory. Moreover, these transmitter systems are likely to compensate for each other, but apparently not via ingrowing sympathetic fibres.

Selective Noradrenaline Depletion in the Neocortex and Hippocampus Induces Working Memory Deficits and Regional Occurrence of Pathological Proteins.

Noradrenaline (NA) depletion occurs in Alzheimer's disease (AD); however, its relationship with the pathological expression of Tau and transactive response DNA-binding protein 43 (TDP-43), two major hallmarks of AD, remains elusive. Here, increasing doses of a selective noradrenergic immunotoxin were injected into developing rats to generate a model of mild or severe NA loss. At about 12 weeks post-lesion, dose-dependent working memory deficits were detected in these animals, associated with a marked increase in cortical and hippocampal levels of TDP-43 phosphorylated at Ser 409/410 and Tau phosphorylated at Thr 217. Notably, the total levels of both proteins were largely unaffected, suggesting a direct relationship between neocortical/hippocampal NA depletion and the phosphorylation of pathological Tau and TDP-43 proteins. As pTD43 is present in 23% of AD cases and pTau Thr217 has been detected in patients with mild cognitive impairment that eventually would develop into AD, improvement of noradrenergic function in AD might represent a viable therapeutic approach with disease-modifying potential.

The Cybersecurity and the Care Robots: A Viewpoint on the Open Problems and the Perspectives.

Care robots represent an opportunity for the health domain. The use of these robots has important implications. They can be used in surgery, rehabilitation, assistance, therapy, and other medical fields. Therefore, care robots (CR)s, have both important physical and psychological implications during their use. Furthermore, these devices, meet important data in clinical applications. These data must be protected. Therefore, cybersecurity (CS) has become a crucial characteristic that concerns all the involved actors. The study investigated the collocation of CRs in the context of CS studies in the health domain. Problems and peculiarities of these devices, with reference to the CS, were faced, investigating in different scientific databases. Highlights, ranging also from ethics implications up to the regulatory legal framework (ensuring safety and cybersecurity) have been reported. Models and cyber-attacks applicable on the CRs have been identified.

Digital Contact Tracing and COVID-19: Design, Deployment, and Current Use in Italy.

The technological innovation of digital contact tracing (DCT) has certainly characterized the COVID-19 pandemic, as compared to the previous ones. Based on the first studies, considerable support was expected from smartphone applications ("apps") for DCT. This commentary focuses on digital contact tracing. Its contributions are threefold: (a) Recall the initial expectations of these technologies and the state of diffusion. (b) Deal with the introduction of the app "Immuni" in Italy, while also highlighting the initiatives undertaken at the government level. (c) Report the state of diffusion and use of this App. The commentary ends by proposing some reflections on the continuation of this investigation in Italy.

Opportunities and Problems of the Consensus Conferences in the Care Robotics.

Care robots represent an opportunity for the health domain. The use of these devices has important implications. They can be used in surgical operating rooms in important and delicate clinical interventions, in motion, in training-and-simulation, and cognitive and rehabilitation processes. They are involved in continuous processes of evolution in technology and clinical practice. Therefore, the introduction into routine clinical practice is difficult because this needs the stability and the standardization of processes. The agreement tools, in this case, are of primary importance for the clinical acceptance and introduction. The opinion focuses on the Consensus Conference tool and: (a) highlights its potential in the field; (b) explores the state of use; (c) detects the peculiarities and problems (d) expresses ideas on how improve its diffusion.

Clobetasol promotes neuromuscular plasticity in mice after motoneuronal loss via sonic hedgehog signaling, immunomodulation and metabolic rebalancing.

Motoneuronal loss is the main feature of amyotrophic lateral sclerosis, although pathogenesis is extremely complex involving both neural and muscle cells. In order to translationally engage the sonic hedgehog pathway, which is a promising target for neural regeneration, recent studies have reported on the neuroprotective effects of clobetasol, an FDA-approved glucocorticoid, able to activate this pathway via smoothened. Herein we sought to examine functional, cellular, and metabolic effects of clobetasol in a neurotoxic mouse model of spinal motoneuronal loss. We found that clobetasol reduces muscle denervation and motor impairments in part by restoring sonic hedgehog signaling and supporting spinal plasticity. These effects were coupled with reduced pro-inflammatory microglia and reactive astrogliosis, reduced muscle atrophy, and support of mitochondrial integrity and metabolism. Our results suggest that clobetasol stimulates a series of compensatory processes and therefore represents a translational approach for intractable denervating and neurodegenerative disorders.

Selective lesion of the developing central noradrenergic system: short- and long-term effects and reinnervation by noradrenergic-rich tissue grafts.

The possibility to selectively remove noradrenergic neurons in the locus coeruleus/subcoeruleus (LC/SubC) complex by the immunotoxin anti-dopamine-beta-hydroxylase (DBH)-saporin has offered a powerful tool to study the functional role of this projection system. In the present study, the anatomical consequences of selective lesions of the LC/SubC on descending noradrenergic projections during early postnatal development have been investigated following bilateral intraventricular injections of anti-DBH-saporin or 6-hydroxydopamine to immature (4 day old) rats. Administration of increasing doses (0.25-1.0 microg) of the immunotoxin produced, about 5 weeks later, a dose-dependent loss of DBH-immunoreactive neurons in the LC/SubC complex (approximately 45-90%) paralleled by a similar reduction of noradrenergic innervation in the terminal territories in the lumbar spinal cord. Even at the highest dose used (1.0 microg) the immunotoxin did not produce any detectable effects on dopaminergic, adrenergic, serotonergic or cholinergic neuronal populations, which, by contrast, were markedly reduced after administration of 6-hydroxydopamine. The approximately 90% noradrenergic depletion induced by 0.5 and 1.0 microg of anti-DBH-saporin remained virtually unchanged at 40 weeks post-lesion. Conversely, the approximately 45% reduction of spinal innervation density estimated at 5 weeks in animals injected with the lowest dose (0.25 microg) of the immunotoxin was seen recovered up to near-normal levels at 40 weeks, possibly as a result of the intrinsic plasticity of the developing noradrenergic system. A similar reinnervation in the lumbar spinal cord was also seen promoted by grafts of fetal LC tissue implanted at the postnatal day 8 (i.e. 4 days after the lesion with 0.5 microg of anti-DBH-saporin). In these animals, the number of surviving neurons in the grafts and the magnitude of the reinnervation, with fibers extending in both the grey and white matter for considerable distances, were seen higher than those reported in previous studies using adult recipients. This would suggest that the functional interactions between the grafted tissue and the host may recapitulate the events normally occurring during the ontogenesis of the coeruleo-spinal projection system, and can therefore be developmentally regulated. Thus, the neonatal anti-DBH-saporin lesion model, with the possibility to produce graded noradrenergic depletions, holds promises as a most valuable tool to address issues of compensatory reinnervation and functional recovery in the severed CNS as well as to elucidate the mechanisms governing long-distance axon growth from transplanted neural precursors.

Expression of cell fate determinants and plastic changes after neurotoxic lesion of adult mice spinal cord by cholera toxin-B saporin.

Recent studies have attempted to repair the damaged spinal cord (SC) by stimulating neurogenesis or neuroplasticity. Sonic hedgehog (Shh), Notch-1 and Numb are involved in the stem cell functioning. Additionally, Notch-1 has a role as modulator of synaptic plasticity. However, little is known about the role of these proteins in the adult SC after removal of motoneurons. In this study, we have injected cholera toxin-B saporin into the gastrocnemius muscle to induce a depletion of motoneurons within the lumbar SC of adult mice, and analysed the expression of choline acetyltransferase (ChAT), Synapsin-I, Shh, Notch-1 and Numb proteins. The functional outcome of the lesion was monitored by grid walk and rotarod tasks. The neurotoxin lesion determined a motoneuron depletion and a transient decrease of ChAT, Synapsin-I, Shh and Numb levels in the lumbar SC. ChAT was associated with Synapsin-I expression and motor performance at 1 week but not 1 month after lesion, suggesting that the recovery of locomotion could depend on synaptic plasticity, at least in an early phase. Shh and Notch-1 were associated with Synapsin-I levels, suggesting a role in modulating synaptic plasticity. Numb expression also appeared reduced after lesion and linked to motor performance. Moreover, unlike other lesion models, we observed glial reaction but no evidence of cell proliferation within the depleted SC. Given the mentioned roles of Shh, Notch-1 and Numb, we believe that an in vivo manipulation of their signalling after lesion could represent a suitable way to improve functional recovery by modulating synaptic plasticity and/or neurogenesis.