Trisomic neural progenitor cells as novel pharmacological targets in Down Syndrome

Down syndrome (DS) is the main genetic cause of intellectual disability. Decreased proliferation of Neural Progenitor Cells (NPC), widespread neurogenesis impairment and increased astrogliogenesis are considered among the major determinants of brain atrophy and intellectual disability in DS individuals. The best characterized and studied animal model for DS is the Ts65Dn mouse line which recapitulates several features of the human pathology, including cognitive impairment. In the recent years studies suggested that perinatal pharmacotherapies targeting NPC alterations may represent potential interventions in DS. However, at present, no pharmacotherapies are suitable for clinical application. Thus, the need to identify new and safe pharmacotherapies to improve intellectual disability in DS patients. Based on these data, our overall goal was to unravel novel mechanisms underlying We generated and phenotypically characterized NPC from Ts65Dn and euploid pups (P1, 2). We then targeted NPC alterations using at first a phenotypic-based approach that identified 30 FDA/EMA approved drugs able to correct trisomic NPC defective proliferation. Importantly, among the potential hits we identified the immunosuppressant cyclosporine A (CSA). We showed that a neonatal treatment with CSA (P3-P15) corrected the whole triad of defects of DS brain. In parallel, we used a target based approach, exploiting the effect of an agonist of the tropomyosin receptor kinase B, 7,8-DHF, and corn oil on neurogenesis in vitro and in vivo, also evaluating the cognitive performances. In the last part of this thesis we identified new molecular mechanisms altered in trisomic NPC in response to the key astrocytic signal thrombospondin-1. Taken together these data showed that trisomic NPC dysfunctions are pharmacologically relevant targets in DS

Neonatal therapy with clenbuterol and salmeterol restores spinogenesis and dendritic complexity in the dentate gyrus of the Ts65Dn model of Down syndrome

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Treatment with corn oil improves neurogenesis and cognitive performance in the Ts65Dn mouse model of Down syndrome

Individuals with Down syndrome (DS), a genetic condition due to triplication of Chromosome 21, are characterized by intellectual disability that worsens with age. Since impairment of neurogenesis and dendritic maturation are very likely key determinants of intellectual disability in DS, interventions targeted to these defects may translate into a behavioral benefit. While most of the neurogenesis enhancers tested so far in DS mouse models may pose some caveats due to possible side effects, substances naturally present in the human diet may be regarded as therapeutic tools with a high translational impact. Linoleic acid and oleic acid are major constituents of corn oil that positively affect neurogenesis and neuron maturation. Based on these premises, the goal of the current study was to establish whether treatment with corn oil improves hippocampal neurogenesis and hippocampus-dependent memory in the Ts65Dn model of DS. Four-month-old Ts65Dn and euploid mice were treated with saline or corn oil for 30 days. Evaluation of behavior at the end of treatment showed that Ts65Dn mice treated with corn oil underwent a large improvement in hippocampus-dependent learning and memory. Evaluation of neurogenesis and dendritogenesis showed that in treated Ts65Dn mice the number of new granule cells of the hippocampal dentate gyrus and their dendritic pattern became similar to those of euploid mice. In addition, treated Ts65Dn mice underwent an increase in body and brain weight. This study shows for the first time that fatty acids have a positive impact on the brain of the Ts65Dn mouse model of DS. These results suggest that a diet that is rich in fatty acids may exert beneficial effects on cognitive performance in individuals with DS without causing adverse effects

Neonatal treatment with cyclosporine A restores neurogenesis and spinogenesis in the Ts65Dn model of Down syndrome

Down syndrome (DS), a genetic condition due to triplication of chromosome 21, is characterized by reduced proliferation of neural progenitor cells (NPCs) starting from early life stages. This defect is worsened by areduction of neuronogenesis (accompanied by an increase in astrogliogenesis)and dendritic spineatrophy. Since this triad of defects underliesintellectual disability, it seems importantto establish whether it is possible to pharmacologically correct these alterations. In this study, we exploited the Ts65Dn mouse model of DS in order to obtain an answer to this question. In the framework of an in vitrodrug-screening campaign of FDA/EMA-approved drugs,we found that the immunosuppressant cyclosporine A (CSA) restored proliferation, acquisitionof a neuronal phenotype,and maturation of neural progenitorcells (NPCs) from the subventricular zone (SVZ) of the lateral ventricle of Ts65Dn mice. Based on these findings, we treated Ts65Dn mice with CSA in the postnatal period P3-P15. We found that treatment fully restored NPC proliferation in the SVZ and in thesubgranular zone of the hippocampal dentate gyrus,and total number of hippocampal granule cells. Moreover, CSA enhanced development of dendritic spines on the dendritic arbor of the granule cells whose density even surpassed that of euploid mice.In hippocampal homogenates fromTs65Dn mice,we found that CSA normalizedthe excessive levels of p21, akey determinant of proliferation impairment.Results show that neonatal treatment with CSA restores the whole triad of defects of the trisomic brain. In DS CSA treatmentmay pose caveats because it is an immunosuppressant that may cause adverse effects. However, CSA analogues that mimic its effect without eliciting immunosuppressionmay represent practicable tools for ameliorating brain development in individuals with DS

Neonatal therapy with clenbuterol and salmeterol restores spinogenesis and dendritic complexity in the dentate gyrus of the Ts65Dn model of Down syndrome

Down syndrome (DS), a neurodevelopmental disorder caused by triplication of chromosome 21, is characterizedby intellectual disability. In DS, defective neurogenesis causes an overall reduction in the number of neuronspopulating the brain and defective neuron maturation causes dendritic hypotrophy and reduction in the densityof dendritic spines. No effective therapy currently exists for the improvement of brain development in in-dividuals with DS. Drug repurposing is a strategy for identifying new medical use for approved drugs. A drugscreening campaign showed that the \u3b22-adrenergic receptor (\u3b22-AR) agonists clenbuterol hydrochloride (CLEN)and salmeterol xinafoate (SALM) increase the proliferation rate of neural progenitor cells from the Ts65Dnmodel of DS. The goal of the current study was to establish their efficacyinvivo, in the Ts65Dn model. We foundthat, at variance with theinvitroexperiments, treatment with CLEN or SALM did not restore neurogenesis in thehippocampus of Ts65Dn mice treated during the postnatal (P) period P3-P15. In Ts65Dn mice treated with CLENor SALM, however, dendritic spine density and dendritic arborization of the hippocampal granule cells wererestored and the lowest dose tested here (0.01 mg/kg/day) was sufficient to elicit these effects. CLEN and SALMare used in children as therapy for asthma and, importantly, they pass the blood-brain barrier. Our study sug-gests that treatment with these \u3b22-AR agonists may be a therapy of choice in order to correct dendritic devel-opment in DS but is not suitable to rescue neurogenesis

A flavonoid agonist of the TrkB receptor for BDNF improves hippocampal neurogenesis and hippocampus-dependent memory in the Ts65Dn mouse model of DS

Intellectual disability is the unavoidable hallmark of Down syndrome (DS), with a heavy impact on public health. Reduced neurogenesis and impaired neuron maturation are considered major determinants of altered brain function in DS. Since the DS brain starts at a disadvantage, attempts to rescue neurogenesis and neuron maturation should take place as soon as possible. The brain-derived neurotrophic factor (BDNF) is a neurotrophin that plays a key role in brain development by specifically binding to tropomyosin-related kinase receptor B (TrkB). Systemic BDNF administration is impracticable because BDNF has a poor blood-brain barrier penetration. Recent screening of a chemical library has identified a flavone derivative, 7,8-dihydroxyflavone (7,8-DHF), a small-molecule that crosses the blood-brain barrier and binds with high affinity and specificity to the TrkB receptor. The therapeutic potential of TrkB agonists for neurogenesis improvement in DS has never been examined. The goal of our study was to establish whether it is possible to restore brain development in the Ts65Dn mouse model of DS by targeting the TrkB receptor with 7,8-DHF. Ts65Dn mice subcutaneously injected with 7,8-DHF in the neonatal period P3-P15 exhibited a large increase in the number of neural precursor cells in the dentate gyrus and restoration of granule cell number, density of dendritic spines and levels of the presynaptic protein synaptophysin. In order to establish the functional outcome of treatment, mice were treated with 7,8-DHF from P3 to adolescence (P45-50) and were tested with the Morris Water Maze. Treated Ts65Dn mice exhibited improvement of learning and memory, indicating that the recovery of the hippocampal anatomy translated into a functional rescue. Our study in a mouse model of DS provides novel evidence that treatment with 7,8-DHF during the early postnatal period restores the major trisomy-linked neurodevelopmental defects, suggesting that therapy with 7,8-DHF may represent a possible breakthrough for Down syndrome