The recent hypothesis that postnatal microglia are maintained independently of circulating monocytes by local precursors that colonize the brain before birth has relevant implications for the treatment of various neurological diseases, including lysosomal storage disorders (LSDs), for which hematopoietic cell transplantation (HCT) is applied to repopulate the recipient myeloid compartment, including microglia, with cells expressing the defective functional hydrolase. By studying wild-type and LSD mice at diverse time-points after HCT, we showed the occurrence of a short-term wave of brain infiltration by a fraction of the transplanted hematopoietic progenitors, independently from the administration of a preparatory regimen and from the presence of a disease state in the brain. However, only the use of a conditioning regimen capable of ablating functionally defined brain-resident myeloid precursors allowed turnover of microglia with the donor, mediated by local proliferation of early immigrants rather than entrance of mature cells from the circulation.

We report a novel method to generate morphologically, antigenically and transcriptionally dependable microglia-like cells in vivo.

Cell-selective drug release Modulation of neuroinflammation in the central nervous system (CNS) holds great promise for the treatment of several neurodegenerative diseasesmany CNS disorders but it is still challenging. However, selective cell targeting remains challenging. We previously exploited demonstrated that polymeric nanoparticles (NPs) injected intra-parenchyma in the brain can be internalized specifically in to obtain cell specific uptake in microglia/macrophages surrounding the injection site, upon intra-parenchyma administration in mice. Here, we explored NPs administration in the cerebrospinal fluid (CSF) to achieve a wider spreading and increased cell targeting throughout the CNS, generated new NPs variants and studied the effect of modifying size and surface charge on NPs biodistribution and cellular uptake. As hypothesized, intra-cerebroventricular administration resulted in a widespread NPs brain distribution throughout the CNS with prevalent localization in proximity to stemcell niches, such as around the lateral ventricles, the subventricular zone and the rostral migratory stream. Formattato: Non Evidenziato Formattato: Non Evidenziato Formattato: Non Evidenziato Formattato: Non Evidenziato Formattato: Non Evidenziato Formattato: Non EvidenziatoNPs dimensions of 37-39 nm allowed extensive penetration in the brain parenchyma and targeting of up to 15% of microglia. Transient Ddisruption of the blood-brain barrier with mannitol improved NPs brain penetration leading to their internalization in up to 25% of microglia cells. A fraction of the targeted cells was positive for markers of proliferation or stained positive for stemness / progenitor-cell markers such as Nestin, c-kit, or NG2. Interestingly, through these newly formulated NPs we obtained controlled and selective release of chemotherapeutics otherwise difficult to formulate (such as busulfan and etoposide) toloaded drugs (such as the chemotherapeutics busulfan or etoposide) efficiently and could release them selectivity in the target cells, preventing unwanted side effects and the toxicity obtained by direct brain delivery of the same not encapsulated drugs. Overall, these data provide proof of concept of the applicability of these novel NP-based drug formulationss for targeting not only mature microglia but also possibly progenitor cells in the brain and paves the way for brain-restricted microglia-targeted drug delivery regimens.

Hematopoietic stem and progenitor cells (HSPCs) can establish a long‐lasting microglia‐like progeny in the central nervous system of properly myeloablated hosts. We exploited this approach to treat the severe CLN1 neurodegenerative disorder, which is the most aggressive form of neuronal ceroid lipofuscinoses due to palmitoyl‐protein thioesterase‐1 (PPT1) deficiency. We here provide the first evidence that (i) transplantation of wild‐type HSPCs exerts partial but long‐lasting mitigation of CLN1 symptoms; (ii) transplantation of HSPCs over‐expressing hPPT1 by lentiviral gene transfer enhances the therapeutic benefit of HSPCs transplant, with first demonstration of such a dose–effect benefit for a purely neurodegenerative condition like CLN1 disease; (iii) transplantation of hPPT1 over‐expressing HSPCs by a novel intracerebroventricular (ICV) approach is sufficient to transiently ameliorate CLN1‐symptoms in the absence of hematopoietic tissue engraftment of the transduced cells; and (iv) combinatorial transplantation of transduced HSPCs intravenously and ICV results in a robust therapeutic benefit, particularly on symptomatic animals. Overall, these findings provide first evidence of efficacy and feasibility of this novel approach to treat CLN1 disease and possibly other neurodegenerative conditions, paving the way for its future clinical application.

Hematopoietic stem and progenitor cells (HSPCs) can lead to the establishment of a long-lasting microglia-like progeny in the brain of properly myeloablated hosts. We exploited this approach to treat the severe CLN1 neurodegenerative disorder, which is the most aggressive form of neuronal ceroid lipofuscinoses, due to deficiency of palmitoyl-protein thioesterase 1 (hPPT1). We here provide first evidence that: i) transplantation of wild type HSPCs exerts a partial but long-lasting mitigation of the symptoms; ii) transplantation of HSPCs over-expressing hPPT1 by lentiviral gene transfer enhances therapeutic benefit as compared to wild type cell transplant, with first demonstration of such a dose-effect benefit for a purely neurodegenerative condition like CLN1 disease; iii) transplantation of hPPT1 over-expressing HSPCs by a novel intracerebroventricular (ICV) approach is sufficient to transiently ameliorate CLN1 disease symptomatology in the absence of hematopoietic tissue engraftment of the transduced cells; and iv) the combinatorial transplantation of transduced HSPCs intravenously and ICV results in the most robust therapeutic benefit among the tested approaches on both pre-symptomatic as well as symptomatic animals. Overall, these findings provide first evidence of the efficacy and feasibility of this novel approach to treat CLN1 disease and possibly other neurodegenerative conditions, paving the way for its future clinical application.