Intracellular delivery of Parkin-RING0-based fragments corrects Parkin-induced mitochondrial dysfunction through interaction with SLP-2.

BACKGROUND: Loss-of-function mutations in the PRKN gene, encoding Parkin, are the most common cause of autosomal recessive Parkinson's disease (PD). We have previously identified mitoch ondrial Stomatin-like protein 2 (SLP-2), which functions in the assembly of respiratory chain proteins, as a Parkin-binding protein. Selective knockdown of either Parkin or SLP-2 led to reduced mitochondrial and neuronal function in neuronal cells and Drosophila, where a double knockdown led to a further worsening of Parkin-deficiency phenotypes. Here, we investigated the minimal Parkin region involved in the Parkin-SLP-2 interaction and explored the ability of Parkin-fragments and peptides from this minimal region to restore mitochondrial function. METHODS: In fibroblasts, human induced pluripotent stem cell (hiPSC)-derived neurons, and neuroblastoma cells the interaction between Parkin and SLP-2 was investigated, and the Parkin domain responsible for the binding to SLP-2 was mapped. High resolution respirometry, immunofluorescence analysis and live imaging were used to analyze mitochondrial function. RESULTS: Using a proximity ligation assay, we quantitatively assessed the Parkin-SLP-2 interaction in skin fibroblasts and hiPSC-derived neurons. When PD-associated PRKN mutations were present, we detected a significantly reduced interaction between the two proteins. We found a preferential binding of SLP-2 to the N-terminal part of Parkin, with a highest affinity for the RING0 domain. Computational modeling based on the crystal structure of Parkin protein predicted several potential binding sites for SLP-2 within the Parkin RING0 domain. Amongst these, three binding sites were observed to overlap with natural PD-causing missense mutations, which we demonstrated interfere substantially with the binding of Parkin to SLP-2. Finally, delivery of the isolated Parkin RING0 domain and a Parkin mini-peptide, conjugated to cell-permeant and mitochondrial transporters, rescued compromised mitochondrial function in Parkin-deficient neuroblastoma cells and hiPSC-derived neurons with endogenous, disease causing PRKN mutations. CONCLUSIONS: These findings place further emphasis on the importance of the protein-protein interaction between Parkin and SLP-2 for the maintenance of optimal mitochondrial function. The possibility of restoring an abolished binding to SLP-2 by delivering the Parkin RING0 domain or the Parkin mini-peptide involved in this specific protein-protein interaction into cells might represent a novel organelle-specific therapeutic approach for correcting mitochondrial dysfunction in Parkin-linked PD.

Assessing landscape aesthetic values: Do clouds in photographs influence people's preferences?

Photo-based surveys are widely applied to elicit landscape preferences and to assess cultural ecosystem services. Variations in weather and light conditions can potentially alter people's preferences, as sunny landscapes are more positively perceived than those under inclement weather conditions. To assure comparability across pictures, studies usually include photographs taken at sunny days (i.e., blue sky). However, the influence of clouds in sunny landscapes on people's preferences has been rarely considered, although color contrasts between clouds and the blue sky may attract people's attention. This study therefore aimed to assess the effects of clouds in landscape photographs on people's preferences by (1) examining differences in preference between pairs of landscape photographs (i.e., with clouds and without clouds), and (2) explaining variations through variables from eye-tracking simulation, photo content analysis, and Geographic Information System (GIS)-based analysis. Our results indicate no significant differences in preferences between pictures with and without clouds when the pictures with clouds contained a proportion of sky around 22% and a cloud cover of about 39%. However, a higher proportion of sky positively influenced landscape preferences, while a higher proportion of clouds, especially in combination with a lower proportion of sky, had negative effects. These findings suggest that landscape preference studies should pay attention not only to the appearance of the sky in terms of cloudiness, but they also should control the proportion of sky across different pictures to obtain comparable results. Future research should address limitations regarding the transferability of our findings to other types of landscapes and regarding potential differences in perceptions between respondents with different socio-cultural characteristics. Moreover, landscape preferences under changing weather conditions or different cloud types as well as diurnal and seasonal changes should be further explored.

Molecular phenotypes of mitochondrial dysfunction in clinically non-manifesting heterozygous PRKN variant carriers.

Homozygous or compound heterozygous (biallelic) variants in PRKN are causal for PD with highly penetrant symptom expression, while the much more common heterozygous variants may predispose to PD with highly reduced penetrance, through altered mitochondrial function. In the presence of pathogenic heterozygous variants, it is therefore important to test for mitochondrial alteration in cells derived from variant carriers to establish potential presymptomatic molecular markers. We generated lymphoblasts (LCLs) and human induced pluripotent stem cell (hiPSC)-derived neurons from non-manifesting heterozygous PRKN variant carriers and tested them for mitochondrial functionality. In LCLs, we detected hyperactive mitochondrial respiration, and, although milder compared to a biallelic PRKN-PD patient, hiPSC-derived neurons of non-manifesting heterozygous variant carriers also displayed several phenotypes of altered mitochondrial function. Overall, we identified molecular phenotypes that might be used to monitor heterozygous PRKN variant carriers during the prodromal phase. Such markers might also be useful to identify individuals at greater risk of eventual disease development and for testing potential mitochondrial function-based neuroprotective therapies before neurodegeneration advances.

Increased Levels of the Parkinson's Disease-Associated Gene ITPKB Correlate with Higher Expression Levels of α-Synuclein, Independent of Mutation Status.

Autosomal dominant mutations in the gene encoding α-synuclein (SNCA) were the first to be linked with hereditary Parkinson's disease (PD). Duplication and triplication of SNCA has been observed in PD patients, together with mutations at the N-terminal of the protein, among which A30P and A53T influence the formation of fibrils. By overexpressing human α-synuclein in the neuronal system of Drosophila, we functionally validated the ability of IP3K2, an ortholog of the GWAS identified risk gene, Inositol-trisphosphate 3-kinase B (ITPKB), to modulate α-synuclein toxicity in vivo. ITPKB mRNA and protein levels were also increased in SK-N-SH cells overexpressing wild-type α-synuclein, A53T or A30P mutants. Kinase overexpression was detected in the cytoplasmatic and in the nuclear compartments in all α-synuclein cell types. By quantifying mRNAs in the cortex of PD patients, we observed higher levels of ITPKB mRNA when SNCA was expressed more (p < 0.05), compared to controls. A positive correlation was also observed between SNCA and ITPKB expression in the cortex of patients, which was not seen in the controls. We replicated this observation in a public dataset. Our data, generated in SK-N-SH cells and in cortex from PD patients, show that the expression of α-synuclein and ITPKB is correlated in pathological situations.

Potential of eye-tracking simulation software for analyzing landscape preferences.

Profound knowledge about landscape preferences is of high importance to support decision-making, in particular, in the context of emerging socio-economic developments to foster a sustainable spatial development and the maintenance of attractive landscapes. Eye-tracking experiments are increasingly used to examine how respondents observe landscapes, but such studies are very time-consuming and costly. For the first time, this study explored the potential of using eye-tracking simulation software in a mountain landscape by (1) identifying the type of information that can be obtained through eye-tracking simulation and (2) examining how this information contributes to the explanation of landscape preferences. Based on 78 panoramic landscape photographs, representing major landscape types of the Central European Alps, this study collected 19 indicators describing the characteristics of the hotspots that were identified by the Visual Attention Software by 3M (3M-VAS). Indicators included quantitative and spatial information (e.g., number of hotspots, probabilities of initially viewing the hotspots) as well variables indicating natural and artificial features within the hotspots (e.g., clouds, lighting conditions, natural and anthropogenic features). In addition, we estimated 18 variables describing the photo content and calculated 12 landscape metrics to quantify spatial patterns. Our results indicate that on average 3.3 hotspots were identified per photograph, mostly containing single trees and tree trunks, buildings and horizon transitions. Using backward stepwise linear regression models, the hotspot indicators increased the model explanatory power by 24%. Thus, our findings indicate that the analysis of eye-tracking hotspots can support the identification of important elements and areas of a landscape, but it is limited in explaining preferences across different landscape types. Future research should therefore focus on specific landscape characteristics such as complexity, structure or visual appearance of specific elements to increase the depth of information obtained from eye-tracking simulation software.

GCN5 contributes to intracellular lipid accumulation in human primary cardiac stromal cells from patients affected by Arrhythmogenic cardiomyopathy.

Arrhythmogenic cardiomyopathy (ACM) is a genetic disease associated with sudden cardiac death and cardiac fibro-fatty replacement. Over the last years, several works have demonstrated that different epigenetic enzymes can affect not only gene expression changes in cardiac diseases but also cellular metabolism. Specifically, the histone acetyltransferase GCN5 is known to facilitate adipogenesis and modulate cardiac metabolism in heart failure. Our group previously demonstrated that human primary cardiac stromal cells (CStCs) contribute to adipogenesis in the ACM pathology. Thus, this study aims to evaluate the role of GCN5 in ACM intracellular lipid accumulation. To do so, CStCs were obtained from right ventricle biopsies of ACM patients and from samples of healthy cadaveric donors (CTR). GCN5 expression was increased both in ex vivo and in vitro ACM samples compared to CTR. When GCN5 expression was silenced or pharmacologically inhibited by the administration of MB-3, we observed a reduction in lipid accumulation and a mitigation of reactive oxygen species (ROS) production in ACM CStCs. In agreement, transcriptome analysis revealed that the presence of MB-3 modified the expression of pathways related to cellular redox balance. Altogether, our findings suggest that GCN5 inhibition reduces fat accumulation in ACM CStCs, partially by modulating intracellular redox balance pathways.

Generation of hiPSC-Derived Functional Dopaminergic Neurons in Alginate-Based 3D Culture.

Human induced pluripotent stem cells (hiPSCs) represent an unlimited cell source for the generation of patient-specific dopaminergic (DA) neurons, overcoming the hurdle of restricted accessibility to disease-affected tissue for mechanistic studies on Parkinson's disease (PD). However, the complexity of the human brain is not fully recapitulated by existing monolayer culture methods. Neurons differentiated in a three dimensional (3D) in vitro culture system might better mimic the in vivo cellular environment for basic mechanistic studies and represent better predictors of drug responses in vivo. In this work we established a new in vitro cell culture system based on the microencapsulation of hiPSCs in small alginate/fibronectin beads and their differentiation to DA neurons. Optimization of hydrogel matrix concentrations and composition allowed a high viability of embedded hiPSCs. Neural differentiation competence and efficiency of DA neuronal generation were increased in the 3D cultures compared to a conventional 2D culture methodology. Additionally, electrophysiological parameters and metabolic switching profile confirmed increased functionality and an anticipated metabolic resetting of neurons grown in alginate scaffolds with respect to their 2D counterpart neurons. We also report long-term maintenance of neuronal cultures and preservation of the mature functional properties. Furthermore, our findings indicate that our 3D model system can recapitulate mitochondrial superoxide production as an important mitochondrial phenotype observed in neurons derived from PD patients, and that this phenotype might be detectable earlier during neuronal differentiation. Taken together, these results indicate that our alginate-based 3D culture system offers an advantageous strategy for the reliable and rapid derivation of mature and functional DA neurons from hiPSCs.

Kinase inhibition of G2019S-LRRK2 enhances autolysosome formation and function to reduce endogenous alpha-synuclein intracellular inclusions.

The Parkinson's disease (PD)-associated kinase Leucine-Rich Repeat Kinase 2 (LRRK2) is a crucial modulator of the autophagy-lysosome pathway, but unclarity exists on the precise mechanics of its role and the direction of this modulation. In particular, LRRK2 is involved in the degradation of pathological alpha-synuclein, with pathogenic mutations precipitating neuropathology in cellular and animal models of PD, and a significant proportion of LRRK2 patients presenting Lewy neuropathology. Defects in autophagic processing and lysosomal degradation of alpha-synuclein have been postulated to underlie its accumulation and onset of neuropathology. Thus, it is critical to obtain a comprehensive knowledge on LRRK2-associated pathology. Here, we investigated a G2019S-LRRK2 recombinant cell line exhibiting accumulation of endogenous, phosphorylated alpha-synuclein. We found that G2019S-LRRK2 leads to accumulation of LC3 and abnormalities in lysosome morphology and proteolytic activity in a kinase-dependent fashion, but independent from constitutively active Rab10. Notably, LRRK2 inhibition was ineffective upon upstream blockade of autophagosome-lysosome fusion events, highlighting this step as critical for alpha-synuclein clearance.

Aesthetic preference is related to organized complexity.

There is extensive evidence today linking exposure to natural environments to favorable changes in mental and even physical health. There is also a growing body of work indicating that there are specific geometric properties of natural scenes that mediate these effects, and that these properties can also be found in artificial structures like buildings, especially those designed before the emergence of modernism. These geometries are also associated with aesthetic preference-we seem to like what is good for us. Here, using a questionnaire-based survey, we have tried to elucidate some of the parameters that play a role in formulating a preference for one form over the other. The images used were nature scenes from the Alpine landscape with various manipulations to alter their complexity, or with additions of computer graphics or various buildings. In all cases, the presence of a natural scaling hierarchy and of either fractal graphics or of ornate, non-local pre-modern buildings was always preferable to the alternative. We discuss these findings under the light of recent evidence in the field and conclude that they support the idea of the existence of a preference of our perceptive system for certain types of visual organization.

Parkin Interacts with Apoptosis-Inducing Factor and Interferes with Its Translocation to the Nucleus in Neuronal Cells.

Mutations in the PRKN gene (encoding parkin) have been linked to the most frequent known cause of recessive Parkinson's disease (PD), and parkin dysfunction represents a risk factor for sporadic PD. Parkin is widely neuroprotective through different cellular pathways, as it protects dopaminergic neurons from apoptosis in a series of cellular and animal models of PD. The mitochondrial protein apoptosis-inducing factor (AIF) is an important cell death effector, which, upon cellular stress in many paradigms, is redistributed from the mitochondria to the nucleus to function as a proapoptotic factor, mostly independent of caspase activity, while in normal mitochondria it functions as an antiapoptotic factor. AIF is known to participate in dopaminergic neuron loss in experimental PD models and in patients with PD. We, therefore, investigated possible crosstalk between parkin and AIF. By using immunoprecipitation and proximity ligation assays, we demonstrated a physical interaction between the two proteins. Nuclear AIF translocation was significantly reduced by parkin expression in neuroblastoma SH-SY5Y cells after exposure to an apoptogenic stimulus. These results were confirmed in primary murine cortical neurons, which showed a higher nuclear translocation of AIF in parkin-deficient neurons upon an excitotoxic stimulus. Our results indicate that the interaction of parkin with AIF interferes with the nuclear translocation of AIF, which might contribute to the neuroprotective activity of parkin.

Increased Anxiety-Related Behavior, Impaired Cognitive Function and Cellular Alterations in the Brain of Cend1-deficient Mice.

Cend1 is a neuronal-lineage specific modulator involved in coordination of cell cycle exit and differentiation of neuronal precursors. We have previously shown that Cend1-/- mice show altered cerebellar layering caused by increased proliferation of granule cell precursors, delayed radial granule cell migration and compromised Purkinje cell differentiation, leading to ataxic gait and deficits in motor coordination. To further characterize the effects of Cend1 genetic ablation we determined herein a range of behaviors, including anxiety and exploratory behavior in the elevated plus maze (EPM), associative learning in fear conditioning, and spatial learning and memory in the Morris water maze (MWM). We observed significant deficits in all tests, suggesting structural and/or functional alterations in brain regions such as the cortex, amygdala and the hippocampus. In agreement with these findings, immunohistochemistry revealed reduced numbers of γ amino butyric acid (GABA) GABAergic interneurons, but not of glutamatergic projection neurons, in the adult cerebral cortex. Reduced GABAergic interneurons were also observed in the amygdala, most notably in the basolateral nucleus. The paucity in GABAergic interneurons in adult Cend1-/- mice correlated with increased proliferation and apoptosis as well as reduced migration of neuronal progenitors from the embryonic medial ganglionic eminence (MGE), the origin of these cells. Further we noted reduced GABAergic neurons and aberrant neurogenesis in the adult dentate gyrus (DG) of the hippocampus, which has been previously shown to confer spatial learning and memory deficits. Our data highlight the necessity of Cend1 expression in the formation of a structurally and functionally normal brain phenotype.

Dietary iron loading negatively affects liver mitochondrial function.

Iron is an essential co-factor for several metabolic processes, including mitochondrial respiration, and mitochondria are the major sites of iron-utilization. Cellular iron homeostasis must be tightly regulated, as intracellular iron deficiency can lead to insufficient energy production, whereas iron overload triggers ROS (reactive oxygen species) formation via the Fenton reaction. So far little is known on how iron imbalances affect mitochondrial function in vivo and the impact of the genotype on that, we studied the effects of dietary iron loading on mitochondrial respiratory capacity in liver by comparing two genetically divergent mouse strains, namely C57BL/6N and FVB mice. Both mouse strains differed in their basal iron levels and their metabolic responses to iron loading as determined by expression of iron trafficking proteins (ferritin was increased in livers of animals receiving high iron diet) as well as tissue iron content (2-fold increase, FVB p = 0.0013; C57BL/6N p = 0.0022). Dietary iron exposure caused a significant impairment of mitochondrial oxidative phosphorylation, especially regarding OXPHOS capacity (FVB p = 0.0006; C57BL/6N p = 0.0087) and S-ETS capacity (FVB p = 0.0281; C57BL/6N p = 0.0159). These effects were more pronounced in C57BL/6N than in FVB mice and were paralleled by an iron mediated induction of oxidative stress in mitochondria. The increased susceptibility of C57BL6/N mice to iron loading may be due to reduced expression of anti-oxidant defense mechanisms and altered iron trafficking upon dietary challenge pointing to a role of genetic modifiers for cellular and mitochondrial iron trafficking. Finally, iron-mediated induction of mitochondrial oxidative stress and reduction of oxidative phosphorylation may underlie fatigue in subjects with iron loading diseases.

SLP-2 interacts with Parkin in mitochondria and prevents mitochondrial dysfunction in Parkin-deficient human iPSC-derived neurons and Drosophila.

Mutations in the Parkin gene (PARK2) have been linked to a recessive form of Parkinson's disease (PD) characterized by the loss of dopaminergic neurons in the substantia nigra. Deficiencies of mitochondrial respiratory chain complex I activity have been observed in the substantia nigra of PD patients, and loss of Parkin results in the reduction of complex I activity shown in various cell and animal models. Using co-immunoprecipitation and proximity ligation assays on endogenous proteins, we demonstrate that Parkin interacts with mitochondrial Stomatin-like protein 2 (SLP-2), which also binds the mitochondrial lipid cardiolipin and functions in the assembly of respiratory chain proteins. SH-SY5Y cells with a stable knockdown of Parkin or SLP-2, as well as induced pluripotent stem cell-derived neurons from Parkin mutation carriers, showed decreased complex I activity and altered mitochondrial network morphology. Importantly, induced expression of SLP-2 corrected for these mitochondrial alterations caused by reduced Parkin function in these cells. In-vivo Drosophila studies showed a genetic interaction of Parkin and SLP-2, and further, tissue-specific or global overexpression of SLP-2 transgenes rescued parkin mutant phenotypes, in particular loss of dopaminergic neurons, mitochondrial network structure, reduced ATP production, and flight and motor dysfunction. The physical and genetic interaction between Parkin and SLP-2 and the compensatory potential of SLP-2 suggest a functional epistatic relationship to Parkin and a protective role of SLP-2 in neurons. This finding places further emphasis on the significance of Parkin for the maintenance of mitochondrial function in neurons and provides a novel target for therapeutic strategies.

Elevated levels of alpha-synuclein blunt cellular signal transduction downstream of Gq protein-coupled receptors.

Alpha-synuclein is central to Parkinson's disease pathogenesis and pathology, however its precise functions are still unclear. It has been shown to bind both PLCß1 and MAPKs, but how this property influences the downstream signaling of Gq protein-coupled receptors has not been elucidated. Here we show that recombinant expression of alpha-synuclein in human neuroblastoma cells enhances cellular levels of PLCß1 but blunts its signaling pathway, preventing the agonist-dependent rise of cytoplasmic Ca2+. In addition, overexpressing alpha-synuclein abolishes the activation of ERK1/2 upon agonist stimulation, indicating an upstream action in the signal transduction pathway. This data demonstrates that alpha-synuclein, when recombinantly expressed, interferes with the normal signaling of Gq-protein coupled receptors, which are then dysfunctional. Since many neurotransmitter systems utilize these receptor signaling pathways to mediate different abilities affected in Parkinson's disease, we argue this novel perspective might be helpful in designing treatment strategies for some of the non-motor symptoms in Parkinson's disease and synucleinopathies.

Generation of Induced Pluripotent Stem Cells from Frozen Buffy Coats using Non-integrating Episomal Plasmids.

Somatic cells can be reprogrammed into induced pluripotent stem cells (iPSCs) by forcing the expression of four transcription factors (Oct-4, Sox-2, Klf-4, and c-Myc), typically expressed by human embryonic stem cells (hESCs). Due to their similarity with hESCs, iPSCs have become an important tool for potential patient-specific regenerative medicine, avoiding ethical issues associated with hESCs. In order to obtain cells suitable for clinical application, transgene-free iPSCs need to be generated to avoid transgene reactivation, altered gene expression and misguided differentiation. Moreover, a highly efficient and inexpensive reprogramming method is necessary to derive sufficient iPSCs for therapeutic purposes. Given this need, an efficient non-integrating episomal plasmid approach is the preferable choice for iPSC derivation. Currently the most common cell type used for reprogramming purposes are fibroblasts, the isolation of which requires tissue biopsy, an invasive surgical procedure for the patient. Therefore, human peripheral blood represents the most accessible and least invasive tissue for iPSC generation. In this study, a cost-effective and viral-free protocol using non-integrating episomal plasmids is reported for the generation of iPSCs from human peripheral blood mononuclear cells (PBMNCs) obtained from frozen buffy coats after whole blood centrifugation and without density gradient separation.

Cell adhesion molecules in gene and cell therapy approaches for nervous system repair.

The inability of the central nervous system (CNS) to efficiently repair damages results in severe functional impairment after trauma or neurodegenerative/demyelinating diseases. Regeneration failure is attributed to inhibitory molecules creating a nonpermissive environment for axonal regrowth, and dictates the necessity for the development of novel therapeutic strategies. An emerging approach for improving regeneration is the use of gene therapy to manipulate cell adhesion molecule expression in experimental animal models of degeneration. Alternatively, cell transplantation to replace lost neurons and the grafting of myelinating cells to repair demyelinating lesions are promising approaches for treating CNS injuries and demyelination. Schwann cells (SCs), oligodendrocyte progenitors, olfactory ensheathing cells and embryonic and neural stem cells have been shown to form myelin after transplantation into the demyelinated CNS. The repair capacity of the peripheral nervous system (PNS) is much higher, but there is still a limit to the amount of nerve loss that can be bridged after injury, and longer nerve gaps call for the use of conduits populated with living cells. In both cases, the interaction of grafted cells with the host environment is of paramount importance for the incorporation and functional integration of these cells and the manipulation of cell adhesion molecules is an attractive approach towards achieving this goal. In this review we summarize data from the recent literature regarding the manipulation of cell adhesion molecule expression towards CNS and PNS repair and discuss the prospects for future therapeutic applications.

Soluble forms of the cell adhesion molecule L1 produced by insect and baculovirus-transduced mammalian cells enhance Schwann cell motility.

For biotechnological applications, insect cell lines are primarily known as hosts for the baculovirus expression system that is capable to direct synthesis of high levels of recombinant proteins through use of powerful viral promoters. Here, we demonstrate the implementation of two alternative approaches based on the baculovirus system for production of a mammalian recombinant glycoprotein, comprising the extracellular part of the cell adhesion molecule L1, with potential important therapeutic applications in nervous system repair. In the first approach, the extracellular part of L1 bearing a myc tag is produced in permanently transformed insect cell lines and purified by affinity chromatography. In the second approach, recombinant baculoviruses that express L1-Fc chimeric protein, derived from fusion of the extracellular part of L1 with the Fc part of human IgG1, under the control of a mammalian promoter are used to infect mammalian HEK293 and primary Schwann cells. Both the extracellular part of L1 bearing a myc tag accumulating in the supernatants of insect cultures as well as L1-Fc secreted by transduced HEK293 or Schwann cells are capable of increasing the motility of Schwann cells with similar efficiency in a gap bridging bioassay. In addition, baculovirus-transduced Schwann cells show enhanced motility when grafted on organotypic cultures of neonatal brain slices while they retain their ability to myelinate CNS axons. This proof-of-concept that the migratory properties of myelin-forming cells can be modulated by recombinant protein produced in insect culture as well as by means of baculovirus-mediated adhesion molecule expression in mammalian cells may have beneficial applications in the field of CNS therapies.

Lentivirus-mediated expression of insulin-like growth factor-I promotes neural stem/precursor cell proliferation and enhances their potential to generate neurons.

Strategies to enhance neural stem/precursor cell (NPC) capacity to yield multipotential, proliferative, and migrating pools of cells that can efficiently differentiate into neurons could be crucial for structural repair after neurodegenerative damage. Here, we have generated a lentiviral vector for expression of insulin-like growth factor-I (IGF-1) and investigated the impact of IGF-1 transduction on the properties of cultured NPCs (IGF-1-NPCs). Under proliferative conditions, IGF-1 transduction promoted cell cycle progression via cyclin D1 up-regulation and Akt phosphorylation. Remarkably upon differentiation-inducing conditions, IGF-1-NPCs cease to proliferate and differentiate to a greater extent into neurons with significantly longer neurites, at the expense of astrocytes. Moreover, using live imaging we provide evidence that IGF-1 transduction enhances the motility and tissue penetration of grafted NPCs in cultured cortical slices. These results illustrate the important consequence of IGF-1 transduction in regulating NPC functions and offer a potential strategy to enhance the prospective repair potential of NPCs.

Schwann cells engineered to express the cell adhesion molecule L1 accelerate myelination and motor recovery after spinal cord injury.

Functional recovery after spinal cord lesion remains an important goal. A combination of inhibitory molecules and lack of appropriate permissive factors in the lesioned spinal cord results in failure of fiber tract reconnection and function. Experimental transplantation in rodent and primate models of CNS injuries has led to the idea that Schwann cells (SCs) are promising candidates for autologous transplantation to assist myelination of lesions and to deliver therapeutic agents in the CNS. In this study, we used retroviral transduction to genetically modify SCs from transgenic GFP-mice in order to overexpress the cell adhesion molecule L1, a protein promoting neurite outgrowth and implicated in myelination. SCs transduced to express L1 or its chimeric secreted form L1-Fc were mixed and grafted rostrally to the lesion site of adult mice immediately after spinal cord compression injury. Our results indicate that 3 weeks postoperatively, but not thereafter, mice transplanted with L1/L1-Fc-expressing SCs exhibited faster locomotor recovery as compared to animals which received SCs transduced with a control vector or no cells at all. Morphological analysis indicated that the accelerated functional recovery correlated with earlier and enhanced myelination by both grafted and host SCs. Moreover, increased sprouting of serotonergic fibers into and across the lesion site was observed in the L1/L1-Fc group as compared with controls. Our results suggest that transplantation of L1-overexpressing SCs enhances early events in spinal cord repair after injury and may be considered in combinatorial strategies together with other regeneration-promoting molecules.