Inhibition of Sox2 Expression in the Adult Neural Stem Cell Niche In Vivo by Monocationic-based siRNA Delivery

Thyroid hormone action in adult neurogliogenic niches: the known and unknown

Over the last decades, thyroid hormones (THs) signaling has been established as a key signaling cue for the proper maintenance of brain functions in adult mammals, including humans. One of the most fascinating roles of THs in the mature mammalian brain is their ability to regulate adult neurogliogenic processes. In this respect, THs control the generation of new neuronal and glial progenitors from neural stem cells (NSCs) as well as their final differentiation and maturation programs. In this review, we summarize current knowledge on the cellular organization of adult rodent neurogliogenic niches encompassing well-established niches in the subventricular zone (SVZ) lining the lateral ventricles, the hippocampal subgranular zone (SGZ), and the hypothalamus, but also less characterized niches in the striatum and the cerebral cortex. We then discuss critical questions regarding how THs availability is regulated in the respective niches in rodents and larger mammals as well as how modulating THs availability in those niches interferes with lineage decision and progression at the molecular, cellular, and functional levels. Based on those alterations, we explore the novel therapeutic avenues aiming at harnessing THs regulatory influences on neurogliogenic output to stimulate repair processes by influencing the generation of either new neurons (i.e. Alzheimer's, Parkinson's diseases), oligodendrocytes (multiple sclerosis) or both (stroke). Finally, we point out future challenges, which will shape research in this exciting field in the upcoming years.

Hepatoma Derived Growth Factor Enhances Oligodendrocyte Genesis from Subventricular Zone Precursor Cells

Oligodendrocytes, the myelinating cells of the central nervous system (CNS), perform vital functions in neural protection and communication, as well as cognition. Enhanced production of oligodendrocytes has been identified as a therapeutic approach for neurodegenerative and neurodevelopmental disorders. In the postnatal brain, oligodendrocytes are generated from the neural stem and precursor cells (NPCs) in the subventricular zone (SVZ) and parenchymal oligodendrocyte precursor cells (OPCs). Here, we demonstrate exogenous Hepatoma Derived Growth Factor (HDGF) enhances oligodendrocyte genesis from murine postnatal SVZ NPCs in vitro without affecting neurogenesis or astrogliogenesis. We further show that this is achieved by increasing proliferation of both NPCs and OPCs, as well as OPC differentiation into oligodendrocytes. In vivo results demonstrate that intracerebroventricular infusion of HDGF leads to increased oligodendrocyte genesis from SVZ NPCs, as well as OPC proliferation. Our results demonstrate a novel role for HDGF in regulating SVZ precursor cell proliferation and oligodendrocyte differentiation.

Cationic lipoplexes for treatment of cancer stem cell-derived murine lung tumors

Side population (SP) cells with stem-like properties, also known as cancer stem cells (CSC) have been recognized as drivers of the resistance phenotype in many cancers. Central to the characteristic stem-like phenotype of CSCs in cancer is the activity of the SOX2 transcription factor whose upregulation has been associated with enrichment of many oncogenes. This study outlines the fabrication of a lipoplex of SOX2 small interfering RNA (CL-siSOX2) for targeted treatment of SOX2-enriched, CSC-derived orthotopic and xenograft lung tumors in CB-17 SCID mice. CL-siSOX2 induced tumor contraction in cisplatin-naïve and cisplatin-treated groups by 85% and 94% respectively. Reduction in tumor weight and volume following treatment with CL-siSOX2 was associated with reduced protein expression of SOX2 and markers of tumor initiation, inflammation, invasion and metastasis in mice tumor xenografts. In addition, histological staining of lung tumor sections showed reduction in SOX2 expression was associated with inhibition markers of epithelial-to-mesenchymal transition.

The neurofilament derived-peptide NFL-TBS.40-63 enters in-vitro in human neural stem cells and increases their differentiation

Regenerative medicine is a promising approach to treat neurodegenerative diseases by replacing degenerating cells like neurons or oligodendrocytes. Targeting human neural stem cells directly in the brain is a big challenge in such a strategy. The neurofilament derived NFL-TBS.40-63 peptide has recently been introduced as a novel tool to target neural stem cells. Previous studies showed that this peptide can be internalized by rat neural stem cells in vitro and in vivo, which coincided with lower proliferation and self-renewal capacity and increase of differentiation. In this study, we analyzed the uptake and potential effects of the NFL-TBS.40-63 peptide on human neural stem cells isolated from human fetuses. We showed that the peptide inhibits proliferation and the ability to produce neurospheres in vitro, which is consistent with an increase in cell adhesion and differentiation. These results confirm that the peptide could be a promising molecule to target and manipulate human neural stem cells and thus could serve as a strategic tool for regenerative medicine.

The Use of ex Vivo Rodent Platforms in Neuroscience Translational Research With Attention to the 3Rs Philosophy

The principles of the 3Rs—Replacement, Reduction, and Refinement—are at the basis of most advanced national and supranational (EU) regulations on animal experimentation and welfare. In the perspective to reduce and refine the use of these animals in translational research, we here discuss the use of rodent acute and organotypically cultured central nervous system slices. We describe novel applications of these ex vivo platforms in medium-throughput screening of neuroactive molecules of potential pharmacological interest, with particular attention to more recent developments that permit to fully exploit the potential of direct genetic engineering of organotypic cultures using transfection techniques. We then describe the perspectives for expanding the use ex vivo platforms in neuroscience studies under the 3Rs philosophy using the following approaches: (1) Use of co-cultures of two brain regions physiologically connected to each other (source-target) to analyze axon regeneration and reconstruction of circuitries; (2) Microinjection or co-cultures of primary cells and/or cell lines releasing one or more neuroactive molecules to screen their physiological and/or pharmacological effects onto neuronal survival and slice circuitry. Microinjected or co-cultured cells are ideally made fluorescent after transfection with a plasmid construct encoding green or red fluorescent protein under the control of a general promoter such as hCMV; (3) Use of “sniffer” cells sensing the release of biologically active molecules from organotypic cultures by means of fluorescent probes. These cells can be prepared with activatable green fluorescent protein, a unique chromophore that remains in a “dark” state because its maturation is inhibited, and can be made fluorescent (de-quenched) if specific cellular enzymes, such as proteases or kinases, are activated.

Nogo receptor inhibition enhances functional recovery following lysolecithin-induced demyelination in mouse optic chiasm

BACKGROUND

Inhibitory factors have been implicated in the failure of remyelination in demyelinating diseases. Myelin associated inhibitors act through a common receptor called Nogo receptor (NgR) that plays critical inhibitory roles in CNS plasticity. Here we investigated the effects of abrogating NgR inhibition in a non-immune model of focal demyelination in adult mouse optic chiasm.

METHODOLOGY/PRINCIPAL FINDINGS

A focal area of demyelination was induced in adult mouse optic chiasm by microinjection of lysolecithin. To knock down NgR levels, siRNAs against NgR were intracerebroventricularly administered via a permanent cannula over 14 days, Functional changes were monitored by electrophysiological recording of latency of visual evoked potentials (VEPs). Histological analysis was carried out 3, 7 and 14 days post demyelination lesion. To assess the effect of NgR inhibition on precursor cell repopulation, BrdU was administered to the animals prior to the demyelination induction. Inhibition of NgR significantly restored VEPs responses following optic chiasm demyelination. These findings were confirmed histologically by myelin specific staining. siNgR application resulted in a smaller lesion size compared to control. NgR inhibition significantly increased the numbers of BrdU+/Olig2+ progenitor cells in the lesioned area and in the neurogenic zone of the third ventricle. These progenitor cells (Olig2+ or GFAP+) migrated away from this area as a function of time.

CONCLUSIONS/SIGNIFICANCE

Our results show that inhibition of NgR facilitate myelin repair in the demyelinated chiasm, with enhanced recruitment of proliferating cells to the lesion site. Thus, antagonizing NgR function could have therapeutic potential for demyelinating disorders such as Multiple Sclerosis.

In vivo identity of tendon stem cells and the roles of stem cells in tendon healing

We investigated the spatial distribution of stem cells in tendons and the roles of stem cells in early tendon repair. The relationship between tendon-derived stem cells (TDSCs) isolated in vitro and tendon stem cells in vivo was also explored. Iododeoxyuridine (IdU) label-retaining method was used for labeling stem cells in rat patellar tendons with and without injury. Co-localization of label-retaining cells (LRCs) with different markers was done by immunofluorescent staining. TDSCs were isolated from patellar tendon mid-substance after IdU pulsing, and the expression of different markers in fresh and expanded cells was done by immunofluorescent staining. More LRCs were found at the peritenon and tendon-bone junction compared with the mid-substance. Some LRCs at the peritenon were located at the perivascular niche. The LRC number and the expression of proliferative, tendon-related, pluripotency, and pericyte-related markers in LRCs in the window wound increased. Most of the freshly isolated TDSCs expressed IdU, and some TDSCs expressed pericyte-related markers, which were lost during expansion. Both freshly isolated and subcultured TDSCs expressed pluripotency markers, which were absent in LRCs in intact tendons. In conclusion, we identified LRCs at the peritenon, mid-substance, and tendon-bone junction. There were both vascular and non-vascular sources of LRCs at the peritenon, while the source of LRCs at the mid-substance was non-vascular. LRCs participated in tendon repair via migration, proliferation, activation for tenogenesis, and increased pluripotency. Some LRCs in the window wound were pericyte like. Most of the mid-substance TDSCs were LRCs. The pluripotency markers and pericyte-related marker in LRCs might be important for function after injury.