| 1. |
- Ahlenius, Henrik, et al.
(author)
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Adaptor Protein LNK Is a Negative Regulator of Brain Neural Stem Cell Proliferation after Stroke.
- 2012
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In: The Journal of Neuroscience : the official journal of the Society for Neuroscience. - 1529-2401. ; 32:15, s. 5151-5164
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Journal article (peer-reviewed)abstract
- Ischemic stroke causes transient increase of neural stem and progenitor cell (NSPC) proliferation in the subventricular zone (SVZ), and migration of newly formed neuroblasts toward the damaged area where they mature to striatal neurons. The molecular mechanisms regulating this plastic response, probably involved in structural reorganization and functional recovery, are poorly understood. The adaptor protein LNK suppresses hematopoietic stem cell self-renewal, but its presence and role in the brain are poorly understood. Here we demonstrate that LNK is expressed in NSPCs in the adult mouse and human SVZ. Lnk(-/-) mice exhibited increased NSPC proliferation after stroke, but not in intact brain or following status epilepticus. Deletion of Lnk caused increased NSPC proliferation while overexpression decreased mitotic activity of these cells in vitro. We found that Lnk expression after stroke increased in SVZ through the transcription factors STAT1/3. LNK attenuated insulin-like growth factor 1 signaling by inhibition of AKT phosphorylation, resulting in reduced NSPC proliferation. Our findings identify LNK as a stroke-specific, endogenous negative regulator of NSPC proliferation, and suggest that LNK signaling is a novel mechanism influencing plastic responses in postischemic brain.
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| 2. |
- Parmar, Malin, et al.
(author)
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Cell-based therapy for Parkinson's disease : A journey through decades toward the light side of the Force
- 2019
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In: European Journal of Neuroscience. - : Wiley. - 0953-816X .- 1460-9568. ; 49:4, s. 463-471
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Journal article (peer-reviewed)abstract
- This review describes the history, development, and evolution of cell-based replacement therapy for Parkinson's disease (PD), from the first pioneering trials with fetal ventral midbrain progenitors to future trials using stem cells as well as reprogrammed cells. In the spirit of Tom Isaacs, the review takes parallels to the storyline of Star Wars, including the temptations from the dark side and the continuous fight for the light side of the Force. It is subdivided into headings based on the original movies, spanning from A New Hope to the Last Jedi.
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| 3. |
- Pereira, Maria J M, et al.
(author)
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Highly efficient generation of induced neurons from human fibroblasts that survive transplantation into the adult rat brain.
- 2014
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In: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 4
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Journal article (peer-reviewed)abstract
- Induced neurons (iNs) offer a novel source of human neurons that can be explored for applications of disease modelling, diagnostics, drug screening and cell replacement therapy. Here we present a protocol for highly efficient generation of functional iNs from fetal human fibroblasts, and also demonstrate the ability of these converted human iNs (hiNs) to survive transplantation and maintain their phenotype in the adult rat brain. The protocol encompasses a delay in transgene activation after viral transduction that resulted in a significant increase in conversion efficiency. Combining this approach with treatment of small molecules that inhibit SMAD signalling and activate WNT signalling provides a further increase in the conversion efficiency and neuronal purity, resulting in a protocol that provides a highly efficient method for the generation of large numbers of functional and transplantable iNs from human fibroblasts without the use of a selection step. When transplanting the converted neurons from different stages of in vitro culture into the brain of adult rats, we observed robust survival and maintenance of neuronal identity four weeks post-transplantation. Interestingly, the positive effect of small molecule treatment observed in vitro did not result in a higher yield of iNs surviving transplantation.
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| 4. |
- Pfisterer, Ulrich, et al.
(author)
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Direct conversion of human fibroblasts to dopaminergic neurons.
- 2011
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In: Proceedings of the National Academy of Sciences. - : Proceedings of the National Academy of Sciences. - 1091-6490 .- 0027-8424. ; 108:25, s. 10343-10348
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Journal article (peer-reviewed)abstract
- Recent reports demonstrate that somatic mouse cells can be directly converted to other mature cell types by using combined expression of defined factors. Here we show that the same strategy can be applied to human embryonic and postnatal fibroblasts. By overexpression of the transcription factors Ascl1, Brn2, and Myt1l, human fibroblasts were efficiently converted to functional neurons. We also demonstrate that the converted neurons can be directed toward distinct functional neurotransmitter phenotypes when the appropriate transcriptional cues are provided together with the three conversion factors. By combining expression of the three conversion factors with expression of two genes involved in dopamine neuron generation, Lmx1a and FoxA2, we could direct the phenotype of the converted cells toward dopaminergic neurons. Such subtype-specific induced neurons derived from human somatic cells could be valuable for disease modeling and cell replacement therapy.
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| 5. |
- Torper, Olof, et al.
(author)
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Generation of induced neurons via direct conversion in vivo.
- 2013
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In: Proceedings of the National Academy of Sciences. - : Proceedings of the National Academy of Sciences. - 1091-6490 .- 0027-8424. ; 110:17, s. 7038-7043
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Journal article (peer-reviewed)abstract
- Cellular reprogramming is a new and rapidly emerging field in which somatic cells can be turned into pluripotent stem cells or other somatic cell types simply by the expression of specific combinations of genes. By viral expression of neural fate determinants, it is possible to directly reprogram mouse and human fibroblasts into functional neurons, also known as induced neurons. The resulting cells are nonproliferating and present an alternative to induced pluripotent stem cells for obtaining patient- and disease-specific neurons to be used for disease modeling and for development of cell therapy. In addition, because the cells do not pass a stem cell intermediate, direct neural conversion has the potential to be performed in vivo. In this study, we show that transplanted human fibroblasts and human astrocytes, which are engineered to express inducible forms of neural reprogramming genes, convert into neurons when reprogramming genes are activated after transplantation. Using a transgenic mouse model to specifically direct expression of reprogramming genes to parenchymal astrocytes residing in the striatum, we also show that endogenous mouse astrocytes can be directly converted into neural nuclei (NeuN)-expressing neurons in situ. Taken together, our data provide proof of principle that direct neural conversion can take place in the adult rodent brain when using transplanted human cells or endogenous mouse cells as a starting cell for neural conversion.
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| 6. |
- Torper, Olof
(author)
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Generation of induced neurons via direct conversion in vivo and in vitro
- 2014
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Doctoral thesis (other academic/artistic)abstract
- Cellular reprogramming is when one cell is changed into another. This involves structural modifications on the DNA of a cell resulting in a transcriptional change. This occurs naturally during development when early pluripotent cells gradually differentiate into more specialized cells that finally result in a complete organism. This is a finely orchestrated event that includes both extrinsic and intrinsic signaling. Cellular reprogramming can be induced artificially by exposing a somatic cell to a foreign microenvironment or by the forced expression of various transcription factors. Recent studies have shown the possibility to revert a somatic cell back into a pluripotent stem cell, termed induced pluripotent stem cell (iPS) or directly to a different somatic cell using this strategy. In this thesis I focus on the direct reprogramming where one terminally differentiated cell is directly converted into another without passing a pluripotent state. Using lentiviral vectors we could convert embryonic and postnatal human fibroblasts into functional neurons (iN) by the forced expression of Ascl1, Brn2 and Myt1L (ABM). By including the additional factors, Foxa2 and Lmx1a, subtype specific neurons could be obtained that release dopamine, express specific markers and exhibit electrophysiological properties characteristic of dopaminergic neurons. Further we show the possibility to transplant fibroblasts and astrocytes into brains of adult rats and then convert them into neurons in vivo. These cells expressed pan- neuronal markers and converted at similar rates as reported in vitro. Using Cre inducible lentiviral vectors, coding for ABM and inject these into the brains of transgenic mice expressing Cre under the GFAP promoter, we could specifically target astrocytes and convert these into neurons in vivo. Using the same strategy we cloned the three factors, Ascl1, Lmx1a and Nurr1 (ALN) together with GFP, into Cre inducible recombinant adeno associated viral vectors (rAAV) with the aim to convert NG2 glia into dopaminergic neurons. rAAV vectors are interesting tools for clinical applications because of their low pathogenicity and their ability to infect both dividing and non-dividing cells. By including a synapsin promoter for the GFP reporter we could specifically visualize converted cells that expressed the pan neuronal markers NeuN and MAP2 but failed to induce a dopaminergic phenotype. More studies aim to study these cells after a longer maturation time and their functional properties in terms of electrophysiology and synaptic formation. Cellular reprogramming of somatic cells is an interesting option to previously studied sources in cell replacement therapies that often are associated with logistical and ethical concerns. They are readily available cells that can be obtained from the skin of a patient and direct conversion offers further advantages over iPS cells as they are non-proliferating cells eliminating the risk of forming tumors when transplanted. Further, in vivo reprogramming offers an alternative to traditional cell therapy by creating new neurons in the brain removing the need of an exogenous cell source. The brain is of particular interest for cell replacement therapies as its capacity to repair itself after injuries like stroke is limited and treatments for neurological disorders like Parkinson’s disease (PD) progressively decline in effectiveness and are associated with severe side effects. In summary, this thesis shows the possibility to directly convert human, adult fibroblasts into functional dopaminergic neurons by the forced expression of transcription factors important in neural development. We further show the possibility to transplant fibroblasts and astrocytes into the brains of rats and convert them into neurons in situ. We also show the possibility to convert two types of glia cells, astrocytes and NG2 glia residing in the brain into neurons by using transgenic mice and Cre inducible vectors. This could also be done by using a rAAV vector commonly used in clinical trials. Future studies should focus on factors involved in the specificity of the required cell and how well the cell that is formed correspond genetically, functionally and viably to its endogenous counterpart.
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| 7. |
- Torper, Olof, et al.
(author)
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In Vivo Reprogramming of Striatal NG2 Glia into Functional Neurons that Integrate into Local Host Circuitry.
- 2015
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In: Cell Reports. - : Elsevier BV. - 2211-1247. ; 12:3, s. 474-481
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Journal article (peer-reviewed)abstract
- The possibility of directly converting non-neuronal cells into neurons in situ in the brain would open therapeutic avenues aimed at repairing the brain after injury or degenerative disease. We have developed an adeno-associated virus (AAV)-based reporter system that allows selective GFP labeling of reprogrammed neurons. In this system, GFP is turned on only in reprogrammed neurons where it is stable and maintained for long time periods, allowing for histological and functional characterization of mature neurons. When combined with a modified rabies virus-based trans-synaptic tracing methodology, the system allows mapping of 3D circuitry integration into local and distal brain regions and shows that the newly reprogrammed neurons are integrated into host brain.
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