Nestin enhancer requirements for expression in normal and injured adult CNS

Insights from Rodent Models for Improving Bench-to-Bedside Translation in Traumatic Brain Injury

Road accidents, domestic falls, and persons associated with sports and military services exhibited the concussion or contusion type of traumatic brain injury (TBI) that resulted in chronic traumatic encephalopathy. In some instances, these complex neurological aberrations pose severe brain damage and devastating long-term neurological sequelae. Several preclinical (rat and mouse) TBI models simulate the clinical TBI endophenotypes. Moreover, many investigational neuroprotective candidates showed promising effects in these models; however, the therapeutic success of these screening candidates has been discouraging at various stages of clinical trials. Thus, a correct selection of screening model that recapitulates the clinical neurobiology and endophenotypes of concussion or contusion is essential. Herein, we summarize the advantages and caveats of different preclinical models adopted for TBI research. We suggest that an accurate selection of experimental TBI models may improve the translational viability of the investigational entity.

Combination Therapy by Tissue-Specific Suicide Gene and Bevacizumab in Intramedullary Spinal Cord Tumor

PURPOSE

Malignant gliomas are aggressive spinal cord tumors. In this study, we hypothesized that combination therapy using an anti-angiogenic agent, bevacizumab, and hypoxia-inducible glioblastoma-specific suicide gene could reduce tumor growth.

MATERIALS AND METHODS

In the present study, we evaluated the effect of combination therapy using bevacizumab and pEpo-NI2-SV-TK in reducing the proliferation of C6 cells and tumor growth in the spinal cord. Spinal cord tumor was generated by the injection of C6 cells into the T5 level of the spinal cord. Complexes of branched polyethylenimine (bPEI)/pEpo-NI2-SV-TK were injected into the spinal cord tumor. Bevacizumab was then administered by an intraperitoneal injection at a dose of 7 mg/kg. The anti-cancer effects of combination therapy were analyzed by histological analyses and magnetic resonance imaging (MRI). The Basso, Beattie and Bresnahan scale scores for all of the treatment groups were recorded every other day for 15 days to assess the rat hind-limb strength.

RESULTS

The complexes of bPEI/pEpo-NI2-SV-TK inhibited the viability of C6 cells in the hypoxia condition at 5 days after treatment with ganciclovir. Bevacizumab was decreased in the cell viability of human umbilical vein endothelial cells. Combination therapy reduced the tumor size by histological analyses and MRI. The combination therapy group showed improved hind-limb function compared to the other groups that were administered pEpo-NI2-SV-TK alone or bevacizumab alone.

CONCLUSION

This study suggests that combination therapy using bevacizumab with the pEpo-NI2-SV-TK therapeutic gene could be useful for increasing its therapeutic benefits for intramedullary spinal cord tumors.

A systems-approach reveals human nestin is an endothelial-enriched, angiogenesis-independent intermediate filament protein

The intermediate filament protein nestin is expressed during embryonic development, but considered largely restricted to areas of regeneration in the adult. Here, we perform a body-wide transcriptome and protein-profiling analysis to reveal that nestin is constitutively, and highly-selectively, expressed in adult human endothelial cells (EC), independent of proliferative status. Correspondingly, we demonstrate that it is not a marker for tumour EC in multiple malignancy types. Imaging of EC from different vascular beds reveals nestin subcellular distribution is shear-modulated. siRNA inhibition of nestin increases EC proliferation, and nestin expression is reduced in atherosclerotic plaque neovessels. eQTL analysis reveals an association between SNPs linked to cardiovascular disease and reduced aortic EC nestin mRNA expression. Our study challenges the dogma that nestin is a marker of proliferation, and provides insight into its regulation and function in EC. Furthermore, our systems-based approach can be applied to investigate body-wide expression profiles of any candidate protein.

Regulation of RhoA by STAT3 coordinates glial scar formation

The transcription factor STAT3 is known to control glial scar formation, but the underlying mechanism is unknown. Renault-Mihara et al. show that inhibition of the small GTPase RhoA by STAT3 coordinates reactive astrocyte dynamics during glial scar formation.

Understanding how the transcription factor signal transducer and activator of transcription–3 (STAT3) controls glial scar formation may have important clinical implications. We show that astrocytic STAT3 is associated with greater amounts of secreted MMP2, a crucial protease in scar formation. Moreover, we report that STAT3 inhibits the small GTPase RhoA and thereby controls actomyosin tonus, adhesion turnover, and migration of reactive astrocytes, as well as corralling of leukocytes in vitro. The inhibition of RhoA by STAT3 involves ezrin, the phosphorylation of which is reduced in STAT3-CKO astrocytes. Reduction of phosphatase and tensin homologue (PTEN) levels in STAT3-CKO rescues reactive astrocytes dynamics in vitro. By specific targeting of lesion-proximal, reactive astrocytes in Nestin-Cre mice, we show that reduction of PTEN rescues glial scar formation in Nestin-Stat3^+/− mice. These findings reveal novel intracellular signaling mechanisms underlying the contribution of reactive astrocyte dynamics to glial scar formation.

Transgenic mouse models for studying adult neurogenesis

The mammalian hippocampus shows a remarkable capacity for continued neurogenesis throughout life. Newborn neurons, generated by the radial neural stem cells (NSCs), are important for learning and memory as well as mood control. During aging, the number and responses of NSCs to neurogenic stimuli diminish, leading to decreased neurogenesis and age-associated cognitive decline and psychiatric disorders. Thus, adult hippocampal neurogenesis has garnered significant interest because targeting it could be a novel potential therapeutic strategy for these disorders. However, if we are to use neurogenesis to halt or reverse hippocampal-related pathology, we need to understand better the core molecular machinery that governs NSC and their progeny. In this review, we summarize a wide variety of mouse models used in adult neurogenesis field, present their advantages and disadvantages based on specificity and efficiency of labeling of different cell types, and review their contribution to our understanding of the biology and the heterogeneity of different cell types found in adult neurogenic niches.

Unmasking the responses of the stem cells and progenitors in the subventricular zone after neonatal and pediatric brain injuries

There is great interest in the regenerative potential of the neural stem cells and progenitors that populate the subventricular zone (SVZ). However, a comprehensive understanding of SVZ cell responses to brain injuries has been hindered by the lack of sensitive approaches to study the cellular composition of this niche. Here we review progress being made in deciphering the cells of the SVZ gleaned from the use of a recently designed flow cytometry panel that allows SVZ cells to be parsed into multiple subsets of progenitors as well as putative stem cells. We review how this approach has begun to unmask both the heterogeneity of SVZ cells as well as the dynamic shifts in cell populations with neonatal and pediatric brain injuries. We also discuss how flow cytometric analyses also have begun to reveal how specific cytokines, such as Leukemia inhibitory factor are coordinating SVZ responses to injury.

Transgenic increase of Wnt7b in neural progenitor cells decreases expression of T-domain transcription factors and impairs neuronal differentiation

Wnt/beta-catenin signaling plays an important role in neural development, instructing both progenitor cell division and differentiation. During early corticogenesis, Wnt7b is expressed in a restricted expression pattern in the ventricular zone progenitor cells. However, its influence on progenitor cell behavior has not been fully studied. We report that transgenic overexpression of Wnt7b in neural progenitor cells impairs neuronal differentiation and the development of forebrain structures at embryonic day 10.5 (E10.5). This was accompanied by a decreased expression of T-domain transcription factors Tbr1 and Tbr2, in both progenitor cells and post-mitotic neurons. However, proliferation, apoptosis and the overall proportion of pax6(+) neural progenitor cells were similar to wild-type litter mates. These results suggest that Wnt signaling may affect early neural progenitor differentiation by regulating the expression of pro-neural transcription factors.

Nestin protein is phosphorylated in adult neural stem/progenitor cells and not endothelial progenitor cells

An intermediate filament protein, Nestin, is known as a neural stem/progenitor cell marker. It was shown to be required for the survival and self-renewal of neural stem cells according to the phenotypes of Nestin knockout mice. Nestin expression has also been reported in vascular endothelial cells, and we recently reported Nestin expression in proliferating endothelial progenitor cells, but not in mature endothelial cells. Using quantitative phosphoproteome analysis, we studied differences in phosphorylation levels between CNS Nestin in adult neural stem cells and vascular Nestin in adult bone-marrow-derived endothelial progenitor cells. We detected 495 phosphopeptides in the cell lysates of adult CNS stem/progenitor cells and identified 11 significant phosphorylated amino acid residues in the Nestin protein. In contrast, endothelial progenitor cells showed no significant phosphorylation of Nestin. We also measured neoplastic endothelial cells of the mouse brain and identified 13 phosphorylated amino acid residues in the Nestin protein. Among the 11 phosphorylated amino acids of adult CNS Nestin, five (S565, S570, S819, S883, and S886) were CNS Nestin-specific phosphorylation sites. Detection of the CNS-specific phosphorylation sites in Nestin, for example, by a phospho-specific Nestin antibody, may allow the expression of CNS Nestin to be distinguished from vascular Nestin.

Platelet-derived growth factor over-expression in retinal progenitors results in abnormal retinal vessel formation

Platelet-derived growth factor (PDGF) plays an important role in development of the central nervous system, including the retina. Excessive PDGF signaling is associated with proliferative retinal disorders. We reported previously that transgenic mice in which PDGF-B was over-expressed under control of the nestin enhancer, nes/tk-PdgfB-lacZ, exhibited enhanced apoptosis in the developing corpus striatum. These animals display enlarged lateral ventricles after birth as well as behavioral aberrations as adults. Here, we report that in contrast to the relatively mild central nervous system phenotype, development of the retina is severely disturbed in nes/tk-PdgfB-lacZ mice.

In transgenic retinas all nuclear layers were disorganized and photoreceptor segments failed to develop properly. Since astrocyte precursor cells did not populate the retina, retinal vascular progenitors could not form a network of vessels. With time, randomly distributed vessels resembling capillaries formed, but there were no large trunk vessels and the intraocular pressure was reduced. In addition, we observed a delayed regression of the hyaloid vasculature. The prolonged presence of this structure may contribute to the other abnormalities observed in the retina, including the defective lamination.

Visualization and genetic manipulation of adult neurogenesis using transgenic mice

Many laboratories have focused efforts on the creation of transgenic mouse models to study adult neurogenesis. In the last decade several constitutive reporter, as well as inducible transgenic lines have been published that allowed for visualization, tracking and alteration of specific neurogenic cell populations in the adult brain. Given the popularity of this approach, multiple mouse lines are available, and this review summarizes the differences in the basic techniques that have been used to create these mice, highlighting the different constructs and reporter proteins used, as well as the strengths and limitations of each of these models. Representative examples from the literature demonstrate some of the diverse and seminal findings that have come to fruition through the laborious, yet highly rewarding work of creating transgenic mouse lines for adult neurogenesis research.

Primary culture of neurospheres obtained from fetal mouse central nervous system and generation of inner ear hair cell immunophenotypes in vitro

OBJECTIVE

To investigate whether hair cell immunophenotypes can be derived from the central nervous system.

DESIGN

We established in vitro cell cultures from embryonic day 14.5 fetal rat brain tissue, and analysed changes in the immunohistochemical features of these cell cultures following differentiation.

RESULT

The immature neural progenitors obtained from the fetal mouse central nervous system generated cell immunophenotypes which expressed epitopes of the hair cell marker proteins myosin VIIa and Brn-3c and the supporting cell marker pan-cytokeratin.

CONCLUSION

Neural progenitors have the potential to differentiate into inner ear hair cell and supporting cell phenotypes, and thus may be a useful material for cell transplantation therapy aiming to replace damaged inner ear hair cells.

Expression of candidate markers for stem/progenitor cells in the inner ears of developing and adult GFAP and nestin promoter-GFP transgenic mice

Loss of hair cells in the mammalian cochlea leads to permanent sensori-neural hearing loss. Hair cells degenerate and their places are taken by phalangeal scars formed by non-sensory supporting cells. Current data indicate that early postnatal post-mitotic supporting cells can proliferate and differentiate into hair cell-like cells in culture. In this study, we used GFAP and nestin promoter-GFP transgenic mice in combination with other stem cell markers to characterize supporting cell subtypes in the postnatal day-3 (P3) and adult organs of Corti with potential stem/progenitor cell phenotype. In P3 organ of Corti, we show GFAP-GFP signal in all the supporting cell subtypes while the nestin-GFP was restricted to the supporting cells in the inner hair cell area. At this stage, GFAP and selected stem/progenitor markers displayed overlapping expression pattern in the supporting cell population. In the adult, GFAP expression is down-regulated from the supporting cells in the outer hair cell area and nestin expression is down-regulated in the supporting cells of the inner hair cell area. Sox2 and Jagged1 expression is maintained in the mature supporting cells, while Abcg2 was down-regulated in these cells. In contrast, GFAP and Abcg2 expression was up-regulated in the inner sulcus limbal cells outside the mature organ of Corti's area. Using quantitative reverse transcription-PCR, we found a decrease in transcripts for Jagged1 and Sox2 in adult cochleae. Our findings suggest that the loss of regenerative capacity of the adult organ of Corti is related to down-regulation of stem/progenitor key-markers from the mature supporting cells.

Generation of human embryonic stem cell reporter lines expressing GFP specifically in neural progenitors

Generation of lineage-specific human embryonic stem cell (hESC) reporter lines will facilitate the real time monitoring of differentiation in live cells and the identification of factors governing these processes. It will also enable researchers to purify specific cell populations from heterogeneous differentiated hESC progeny. Here we report the generation of clonally derived nestin-EGFP reporter hESC lines that express GFP under the control of the neuroepithelial specific nestin 2nd intron enhancer. We show that the nestin-EGFP hESC reporter lines retain the features of undifferentiated hESCs, are able to self-renew in hESC culture conditions and to differentiate into cells of all three germ layers. The nestin-EGFP reporter exhibited high expression in neural progenitor cells upon differentiation, although it is detectable at a low level in the undifferentiated state. Furthermore, the expression of the transgene is exclusively confined to the neural progenitors after differentiation. The specific expression of the transgene is determined by collaborative binding motifs of POU and SOX transcription factors in the nestin enhancer. Deletion of either of the binding elements resulted in a significant reduction of enhancer/promoter activity. Taken together, the nestin-EGFP reporter hESC lines are invaluable not only for the study of the neural differentiation process from hESCs but also for the enrichment of neural progenitor cells from other cell lineages.

Imaging and recording subventricular zone progenitor cells in live tissue of postnatal mice

The subventricular zone (SVZ) is one of two regions where neurogenesis persists in the postnatal brain. The SVZ, located along the lateral ventricle, is the largest neurogenic zone in the brain that contains multiple cell populations including astrocyte-like cells and neuroblasts. Neuroblasts migrate in chains to the olfactory bulb where they differentiate into interneurons. Here, we discuss the experimental approaches to record the electrophysiology of these cells and image their migration and calcium activity in acute slices. Although these techniques were in place for studying glial cells and neurons in mature networks, the SVZ raises new challenges due to the unique properties of SVZ cells, the cellular diversity, and the architecture of the region. We emphasize different methods, such as the use of transgenic mice and in vivo electroporation that permit identification of the different SVZ cell populations for patch clamp recording or imaging. Electroporation also permits genetic labeling of cells using fluorescent reporter mice and modification of the system using either RNA interference technology or floxed mice. In this review, we aim to provide conceptual and technical details of the approaches to perform electrophysiological and imaging studies of SVZ cells.

Enlarged lateral ventricles and aberrant behavior in mice overexpressing PDGF-B in embryonic neural stem cells

Platelet-derived growth factor (PDGF) is important in central nervous system (CNS) development, and aberrant expression of PDGF and its receptors has been linked to developmental defects and brain tumorigenesis. We previously found that neural stem and progenitor cells in culture produce PDGF and respond to it by autocrine and/or paracrine signaling. We therefore aimed to examine CNS development after PDGF overexpression in neural stem cells in vivo. Transgenic mice were generated with PDGF-B under control of a minimal nestin enhancer element, which is specific for embryonic expression and will not drive adult expression in mice. The resulting mouse showed increased apoptosis in the developing striatum, which suggests a disturbed regulation of progenitor cells. Later in neurodevelopment, in early postnatal life, mice displayed enlarged lateral ventricles. This enlargement remained into adulthood and it was more pronounced in male mice than in transgenic female mice. Nevertheless, there was an overall normal composition of cell types and numbers in the brain and the transgenic mice were viable and fertile. Adult transgenic males, however, showed behavioral aberrations and locomotor dysfunction. Thus, a tightly regulated expression of PDGF during embryogenesis is required for normal brain development and function in mice.

The neural stem/progenitor cell marker nestin is expressed in proliferative endothelial cells, but not in mature vasculature

Nestin is an intermediate filament protein that is known as a neural stem/progenitor cell marker. It is expressed in undifferentiated central nervous system (CNS) cells during development, but also in normal adult CNS and in CNS tumor cells. Additionally, nestin is expressed in endothelial cells (ECs) of CNS tumor tissues and of adult tissues that replenish by angiogenesis. However, the regulation of nestin expression in vascular endothelium has not been analyzed in detail. This study showed that nestin expression was observed in proliferating endothelial progenitor cells (EPCs), but not in mature ECs. In adherent cultured cells derived from bone marrow cells, EPCs that highly expressed nestin also expressed the endothelial marker CD31 and the proliferation marker Ki67. ECs cultured without growth factors showed attenuated nestin immunoreactivity as they matured. Transgenic mice that carried the enhanced green fluorescent protein under the control of the CNS-specific second intronic enhancer of the nestin gene showed no reporter gene expression in EPCs. This indicated that the mechanisms of nestin gene expression were different in EPCs and CNS cells. Immunohistochemistry showed nestin expression in neovascular cells from two distinct murine models. Our results demonstrate that nestin can be used as a marker protein for neovascularization.

Conditional ablation and recovery of forebrain neurogenesis in the mouse

Forebrain neurogenesis persists throughout life in the rodent subventricular zone (SVZ) and hippocampal dentate gyrus (DG). Several strategies have been employed to eliminate adult neurogenesis and thereby determine whether depleting adult-born neurons disrupts specific brain functions, but some approaches do not specifically target neural progenitors. We have developed a transgenic mouse line to reversibly ablate adult neural stem cells and suppress neurogenesis. The nestin-tk mouse expresses herpes simplex virus thymidine kinase (tk) under the control of the nestin 2nd intronic enhancer, which drives expression in neural progenitors. Administration of ganciclovir (GCV) kills actively dividing cells expressing this transgene. We found that peripheral GCV administration suppressed SVZ-olfactory bulb and DG neurogenesis within 2 weeks but caused systemic toxicity. Intracerebroventricular GCV infusion for 28 days nearly completely depleted proliferating cells and immature neurons in both the SVZ and DG without systemic toxicity. Reversibility of the effects after prolonged GCV infusion was slow and partial. Neurogenesis did not recover 2 weeks after cessation of GCV administration, but showed limited recovery 6 weeks after GCV that differed between the SVZ and DG. Suppression of neurogenesis did not inhibit antidepressant responsiveness of mice in the tail suspension test. These findings indicate that SVZ and DG neural stem cells differ in their capacity for repopulation, and that adult-born neurons are not required for antidepressant responses in a common behavioral test of antidepressant efficacy. The nestin-tk mouse should be useful for studying how reversible depletion of adult neurogenesis influences neurophysiology, other behaviors, and neural progenitor dynamics.

Direct isolation of neural stem cells in the adult hippocampus after traumatic brain injury

Recently, we have manipulated endogenous neural stem/progenitor cells (NSCs) in situ in the adult mouse to undergo neurogenesis and anatomic circuit re-formation de novo in the neocortex, where it does not normally occur, by using a highly targeted brain injury model. However, how the NSCs respond to injury in the adult mouse brain is poorly understood. While studying the molecular mechanisms that regulate NSC fates after brain injury, it is important to develop a strategy to identify NSCs in niches and isolate them directly from fresh tissue after brain injury. Here we report that we directly isolated NSCs from adult brains after traumatic brain injury by genetically labeling NSCs with EGFP combined with fluorescence-activated cell sorting (FACS) technique without an intervening cell culture and with high concentrations of growth factors. The isolated EGFP-positive cells can self-renew and have the potential to differentiate into both neurons and glia in vitro, confirming that the FACS-sorted EGFP-positive cells are NSCs. This unique approach provides a useful tool to isolate large amounts of endogenous NSCs in situ for identifying the critical molecules that regulate fate decision and neurogenesis in the adult brain after injury.

A novel embryonic nestin-expressing radial glia-like progenitor gives rise to zonally restricted olfactory and vomeronasal neurons

Persistent neurogenesis is maintained throughout development and adulthood in the mouse olfactory epithelium (OE). Despite this, the identity and origin of different embryonic OE progenitors, their spatiotemporal induction and contribution to patterning during development, has yet to be delineated. Here, we show that the embryonic OE contains a novel nestin-expressing radial glia-like progenitor (RGLP) that is not found in adult OE, which is antigenically distinct from embryonic CNS radial glia. Nestin-cre-mediated lineage tracing with three different reporters reveals that only a subpopulation of nestin-expressing RGLPs activate "CNS-specific" nestin regulatory elements, and produce spatially restricted olfactory receptor neurons (ORNs) in zone 1 of the OE, and vomeronasal receptor neurons restricted to the VR1 zone. This dorsal-medial restriction of transgene-activating cells is also seen in the embryonic OE of Nestin-GFP transgenic mice, in which green fluorescent protein (GFP) is found in a subpopulation of GFP+Mash1+ neuronal progenitors, despite the fact that endogenous Nestin expression is found in RGLPs throughout the OE. Embryonic OE progenitors produce three biologically distinct colony subtypes in vitro, a subpopulation of which include nestin-expressing RGLPs during in vitro colony formation. When generated from Nestin-cre/ZEG mice, neurogenic colonies also produce GFP+Mash1+ progenitors and ORNs. We thus identify a novel neurogenic precursor, the RGLP of the OE and vomeronasal organ (VNO), and provide the first evidence for intrinsic differences in the origin and spatiotemporal potential of distinct progenitors during development of the OE and VNO.

Nestin expression in the kidney with an obstructed ureter

Nestin is an intermediate filament protein originally identified in neuroepithelial stem cells. This cytoskeletal-associated protein is also expressed in some non-neuronal organs including renal tubular cells and glomerular endothelial cells during kidney development. Little is known, however, about nestin expression in the kidney during injury. In this study, we find nestin expression induced in renal tubular and interstitial myofibroblasts in the adult rat kidney following unilateral ureteral obstruction. The degree of nestin expression was well correlated with the degree of tubulointerstitial fibrosis. Immunohistochemical identification of specific nephron segments showed that nestin was primarily expressed by proximal tubules, partially by distal tubules and thick ascending limbs of Henle but not by collecting ducts. The nestin-positive tubular cells also expressed vimentin and heat-shock protein 47 (HSP47) suggesting these cells reverted to a mesenchymal phenotype. Not all vimentin- or HSP-expressing cells expressed nestin; however, suggesting that nestin is distinct from these conventional mesenchymal markers. Nestin expression was also found associated with phenotypical changes in cultured renal cells induced by hypoxia or transforming growth factor-beta. Nestin expression was located in hypoxic regions of the kidney with an obstructed ureter. Our results indicate that nestin could be a novel marker for tubulointerstitial injury.

Notch signaling enhances nestin expression in gliomas

Recent findings suggest that Notch signaling is active in brain tumors and stem cells, and that stem cells or cells with progenitor characteristics contribute to brain tumor formation. These stem cells are marked by expression of several markers, including nestin, an intermediate filament protein. We have studied how the Notch signaling pathway affects nestin expression in brain tumors. We find that Notch receptors and ligands are expressed in vitro and in human samples of glioblastomas, the highest grade of malignant gliomas. In culture, Notch activity activates the nestin promoter. Activation of the Notch pathway also occurs in a glioblastoma multiforme mouse model induced by Kras, with translational regulation playing a role in Notch expression. Combined activation of Notch and Kras in wild-type nestin-expressing cells leads to their expansion within the subventricular zone and retention of proliferation and nestin expression. However, activation of Notch alone is unable to induce this cellular expansion. These data suggest that Notch may have a contributing role in the stem-like character of glioma cells.

Nestin-GFP reporter expression defines the quiescent state of skeletal muscle satellite cells

Repair of adult skeletal muscle depends on satellite cells, quiescent myogenic stem cells located beneath the myofiber basal lamina. Satellite cell numbers and performance decline with age and disease, yet the intrinsic molecular changes accompanying these conditions are unknown. We identified expression of GFP driven by regulatory elements of the nestin (NES) gene within mouse satellite cells, which permitted characterization of these cells in their niche. Sorted NES-GFP+ cells exclusively acquired a myogenic fate, even when supplemented with media supporting non-myogenic development. Mutual and unique gene expression by NES-GFP+ cells from hindlimb and diaphragm muscles demonstrated intra- and inter-muscular heterogeneity of satellite cells. NES-GFP expression declined following satellite cell activation and was reacquired in late stage myogenic cultures by non-proliferating Pax7+ progeny. The dynamics of this expression pattern reflect the cycle of satellite cell self-renewal. The NES-GFP model reveals unique transcriptional activity within quiescent satellite cells and permits novel insight into the heterogeneity of their molecular signatures.

Electrical stimulation modulates fate determination of differentiating embryonic stem cells

A clear understanding of cell fate regulation during differentiation is key in successfully using stem cells for therapeutic applications. Here, we report that mild electrical stimulation strongly influences embryonic stem cells to assume a neuronal fate. Although the resulting neuronal cells showed no sign of specific terminal differentiation in culture, they showed potential to differentiate into various types of neurons in vivo, and, in adult mice, contributed to the injured spinal cord as neuronal cells. Induction of calcium ion influx is significant in this differentiation system. This phenomenon opens up possibilities for understanding novel mechanisms underlying cellular differentiation and early development, and, perhaps more importantly, suggests possibilities for treatments in medical contexts.

Conditional ablation of Stat3 or Socs3 discloses a dual role for reactive astrocytes after spinal cord injury

In the injured central nervous system (CNS), reactive astrocytes form a glial scar and are considered to be detrimental for axonal regeneration, but their function remains elusive. Here we show that reactive astrocytes have a crucial role in wound healing and functional recovery by using mice with a selective deletion of the protein signal transducer and activator of transcription 3 (Stat3) or the protein suppressor of cytokine signaling 3 (Socs3) under the control of the Nes promoter-enhancer (Nes-Stat3(-/-), Nes-Socs3(-/-)). Reactive astrocytes in Nes-Stat3(-/-) mice showed limited migration and resulted in markedly widespread infiltration of inflammatory cells, neural disruption and demyelination with severe motor deficits after contusive spinal cord injury (SCI). On the contrary, we observed rapid migration of reactive astrocytes to seclude inflammatory cells, enhanced contraction of lesion area and notable improvement in functional recovery in Nes-Socs3(-/-) mice. These results suggest that Stat3 is a key regulator of reactive astrocytes in the healing process after SCI, providing a potential target for intervention in the treatment of CNS injury.

Differential expression of the intermediate filament protein nestin during renal development and its localization in adult podocytes

Nestin, an intermediate filament protein, is widely used as stem cell marker. Nestin has been shown to interact with other cytoskeleton proteins, suggesting a role in regulating cellular cytoskeletal structure. These studies examined renal nestin localization and developmental expression in mice. In developing kidney, anti-nestin antibody revealed strong immunoreactivity in vascular cleft of the S-shaped body and vascular tuft of capillary loop-stage glomerulus. The nestin-positive structures also were labeled by endothelial cell markers FLK1 and CD31 in immature glomeruli. Nestin was not detected in epithelial cells of immature glomeruli. In contrast, in mature glomerular, nestin immunoreactivity was observed only outside laminin-positive glomerular basement membrane, and co-localized with nephrin, consistent with podocyte nestin expression. In adult kidney, podocytes were the only cells that exhibited persistent nestin expression. Nestin was not detected in ureteric bud and its derivatives throughout renal development. Cell lineage studies, using a nestin promoter-driven Cre mouse and a ROSA26 reporter mouse, showed a strong beta-galactosidase activity in intermediate mesoderm in an embryonic day 10 embryo and all of the structures except those that were derived from ureteric bud in embryonic kidney through adult kidney. These studies show that nestin is expressed in progenitors of glomerular endothelial cells and renal progenitors that are derived from metanephric mesenchyme. In the adult kidney, nestin expression is restricted to differentiated podocytes, suggesting that nestin could play an important role in maintaining the structural integrity of the podocytes.

The Sox2 regulatory region 2 functions as a neural stem cell-specific enhancer in the telencephalon

Sox2 is expressed at high levels in neuroepithelial stem cells and persists in neural stem/progenitor cells throughout adulthood. We showed previously that the Sox2 regulatory region 2 (SRR2) drives strong expression in these cells. Here we generated transgenic mouse strains with the beta-geo reporter gene under the control of the SRR2 in order to examine the spatiotemporal function of this regulatory region. We show that the SRR2 functions specifically in neural stem/progenitor cells. However, unlike Nestin 2nd intronic enhancer, the SRR2 shows strong regional specificity functioning only in restricted areas of the telencephalon but not in any other portions of the central nervous system such as the spinal cord. We also show by in vitro clonogenic assay that at least some of these SRR2-functioning cells possess the hallmark properties of neural stem cells. In adult brains, we could detect strong beta-geo expression in the subventricular zone of the lateral ventricle and along the rostral migrating stream where actively dividing cells reside. Chromatin immunoprecipitation assays reveal interactions of POU and Sox factors with SRR2 in neural stem/progenitor cells. Our data also suggest that the specific recruitment of these proteins to the SRR2 in the telencephalon defines the spatiotemporal activity of the enhancer in the developing nervous system.

Isolation of neural stem cells from damaged rat cerebral cortex after traumatic brain injury

Nestin-positive cells were seen around the damaged area at 24 h, 72 h and 7 days after rat traumatic brain injury. Tissue was isolated from around the damaged area at 72 h after injury and spheres were cultured with basic fibroblast growth factor and epidermal growth factor. These spheres could not be isolated at 24 h and 7 days after injury. Isolated spheres consisted of nestin-positive neural stem cells. Neurospheres differentiated into Tuj1-positive, glial fibrillary acidic protein-positive and O4-positive cells after 4 days in culture without basic fibroblast growth factor and epidermal growth factor. These results indicate that isolated and cultured neurospheres can differentiate into neurons and glia. An increase in nestin-positive cells around a cerebral cortical damaged area might contribute to neurogenesis and neuroplasticity.

Animal models of head trauma

Animal models of traumatic brain injury (TBI) are used to elucidate primary and secondary sequelae underlying human head injury in an effort to identify potential neuroprotective therapies for developing and adult brains. The choice of experimental model depends upon both the research goal and underlying objectives. The intrinsic ability to study injury-induced changes in behavior, physiology, metabolism, the blood/tissue interface, the blood brain barrier, and/or inflammatory- and immune-mediated responses, makes in vivo TBI models essential for neurotrauma research. Whereas human TBI is a highly complex multifactorial disorder, animal trauma models tend to replicate only single factors involved in the pathobiology of head injury using genetically well-defined inbred animals of a single sex. Although such an experimental approach is helpful to delineate key injury mechanisms, the simplicity and hence inability of animal models to reflect the complexity of clinical head injury may underlie the discrepancy between preclinical and clinical trials of neuroprotective therapeutics. Thus, a search continues for new animal models, which would more closely mimic the highly heterogeneous nature of human TBI, and address key factors in treatment optimization.

A perspective on pancreatic stem/progenitor cells

The prevalence of both type 1 and type 2 diabetes mellitus is increasing throughout the world along with the ensuant morbidity and early mortality because of premature microvascular and macrovascular disease. Current insulin and drug therapies control diabetes, but do not cure it. Cell-based therapies offer the possibilities of a permanent cure for diabetes. Recently, success in the transplantation of pancreatic islets in the livers of type 1 diabetics has afforded the opportunity for a potential cure. However, the severe shortage of donor islets for transplantation limits the usefulness of this therapy. One approach is to exploit the use of stem cells, either embryo-derived or adult tissue-derived, as substrates to create islet tissue suitable for transplantation. Cells isolated from embryo blastocysts and from adult pancreas, liver, and bone marrow can be expanded extensively in vitro and differentiated into islet-like clusters that produce insulin, and, in some instances, can achieve glycemic control when transplanted into streptozotocin-induced diabetic mice. It is, now, also possible to envision the direct systemic administration of stem cells that would home in on and regenerate injured islets, or to administer stem cell stimulators that would enhance endogenous pancreatic stem cells to expand and differentiate into functional, insulin-producing beta-cells. This perspective discusses the potential applications of cellular medicines, in the new discipline of regenerative medicine, to achieve a cure for diabetes.

Different regions of the mouse nestin enhancer may function differentially in nestin expression in an NSC-like cell line and astrocytes

Nestin is a characteristic intermediate filament protein expressed in neural stem cells (NSCs). Evidence has shown that it is also found in reactive astrocytes. Previous studies have demonstrated that the second intron of the human and rat nestin genes harbors the central nervous system (CNS) enhancer and the midbrain enhancer, which regulate nestin expression in different regions of CNS during development. In this study, using an NSC-like cell line C17.2 and primarily cultured astrocytes, we show that both C17.2 cells and astrocytes express nestin. To characterize the nestin enhancer in further detail, we cloned the second intron of the mouse nestin gene, which is homologous to the human and rat counterparts as shown by DNA sequencing. Reporter assay indicated that the full-length nestin enhancer was active in both C17.2 cells and astrocytes, consistent with the immunocytochemistry results. However, in C17.2 cells, the enhancer activity was attributed to the highly conserved 3' part, and the 5' part of the enhancer was suppressive to the transcription activation activity of the full-length enhancer. While in astrocytes, both 3' and 5' parts were able to enhance the reporter gene expression. Our data suggested that different regions of the nestin enhancer might have different functions in C17.2 cells and astrocytes: while the 3' region activates transcription in both cell types, the 5' region suppresses in C17.2 cells but activates in astrocytes nestin expression.

Characterization of an intronic enhancer that regulates myelin proteolipid protein (Plp) gene expression in oligodendrocytes

The myelin proteolipid protein (Plp) gene is expressed in oligodendrocytes and encodes the most abundant protein (approximately 50%) present in mature myelin from the central nervous system (CNS). Plp gene activity is low to nonexistent early in development but sharply increases, concurrently with the active myelination period of CNS development. Work from our laboratory suggests that the temporal regulation of Plp gene expression in mice is mediated by a positive regulatory element located within Plp intron 1 DNA. We have termed this regulatory element/region ASE (for antisilencer/enhancer). The ASE is situated approximately 1 kb downstream of exon 1 DNA and encompasses nearly 100 bp. To understand the mechanisms by which the ASE augments Plp gene expression in oligodendrocytes, Plp-lacZ constructs were generated and transfected into a mouse oligodendroglial cell line (N20.1). Results presented here demonstrate that upstream regulatory elements in the Plp promoter/5'-flanking DNA are not required for ASE activity; the ASE worked perfectly well when the thymidine kinase (TK) promoter was substituted for the Plp promoter. However, the relative location of the ASE appears to be important. When placed upstream of 2.4 kb of Plp 5'-flanking DNA, or downstream of the lacZ expression cassette, the ASE was no longer effective. Thus, the ASE might have to be in the context of the intron in order to function. To begin to identify the crucial nucleotides within the ASE, orthologous sequences from rat, human, cow, and pig Plp genes were swapped for the mouse sequence. Results presented here demonstrate that the orthologous sequence from rat can substitute for the mouse ASE, unlike those from human, cow, or pig.

Angiogenic endothelium-specific nestin expression is enhanced by the first intron of the nestin gene

Nestin is a member of intermediate filaments abundantly expressed in neural stem cells and glioblastomas. The nestin gene has four exons and three introns, and neural cell-specific expression is regulated by the second intron. We previously reported that nestin was invariably detected in the tumor endothelium in gliomas even though tumor cells were negative for nestin. In the present study, we further confirmed nestin immunostaining in tumor endothelium of a variety of common cancers, including lung, stomach, colon, and cervical carcinomas. We examined an endothelium-specific regulator using human umbilical vein endothelial cells (HUVECs) and human glioblastoma-derived U251 cells. In a luciferase reporter assay, the first intron plus 5' upstream promoter (5'UP) gave the highest activity, followed by 5'UP, and the second intron plus 5'UP. However, the assay values were much lower by HUVEC extracts than by U251 cell extracts. Although green fluorescent protein expression was positive over all U251 cells under either the first intron, second intron, or ubiquitously active CAG promoter, the fluorescence in HUVECs was limited to a few cells even under the first intron. This difference came from the growth feature of HUVECs which exhibit growth arrest by contact inhibition. We found that the nestin expression was specific to proliferative endothelium, by using proliferation markers in hemangioblastomas and in situ hybridization. Using an endothelial tube formation assay, tyrosine kinase domain-deleted VEGF receptor KDR effectively abolished the tube formation under the first intron. We suggest that the nestin expression in tumor endothelium is enhanced by the first intron.

Stem/progenitor cells in the postnatal inner ear of the GFP-nestin transgenic mouse

Nestin promoter-GFP (green fluorescent protein) transgenic mice were used to determine the presence of stem/progenitor cells in the mouse inner ear. We examined the inner ear of mice at the following postnatal days (P): P0, P4, P5, P15 and P60. Hair cells stereocilia were identified with the use of the histochemical marker phalloidin. Whole endorgans or cryosections were analyzed under epi-fluorescent or confocal microscopy. From P0 to P5, GFP expressing cells were found in the vestibular sensory epithelia of the macula utricle, but not in the crista ampullaris. Cells within the stroma (tissue underneath the sensory epithelia), utricle, and crista were also GFP-positive. Satellite cells in the vestibular ganglia were GFP-positive, while vestibular ganglia neurons were not. In the organ of Corti, GFP signal was found in inner border and inner phalangeal cells that surround the inner hair cells (GFP-negative), Dieters cells and cells in the great epithelial ridge. Outer hair cells were mildly positive for GFP. Satellite cells in the spiral ganglia were GFP-positive, while spiral ganglia neurons were not. Similar GFP expression was found in the vestibule and cochlea of animals at P15, however, outer hair cells showed no GFP expression. The inner ear of P60 animals contained moderate GFP expression in the stroma of the crista ampullaris and utricle, but not within the sensory epithelia. In the organ of Corti, moderate GFP expression was found in a few Deiters cells. The present data indicates that the expression of nestin in the mouse inner ear is developmentally regulated; yet in the adult inner ear there are some nestin expressing cells, suggesting an intrinsic repair potential, although to a more limited extent than during early post-natal life.

Implantation of dendritic cells in injured adult spinal cord results in activation of endogenous neural stem/progenitor cells leading to de novo neurogenesis and functional recovery

We report a treatment for spinal cord injury involving implantation of dendritic cells (DCs), which act as antigen-presenting cells in the immune system. The novel mechanisms underlying this treatment produce functional recovery. Among the immune cells tested, DCs showed the strongest activity inducing proliferation and survival of neural stem/progenitor cells (NSPCs) in vitro. Furthermore, in DC-implanted adult mice, endogenous NSPCs in the injured spinal cord were activated for mitotic de novo neurogenesis. These DCs produced neurotrophin-3 and activated endogenous microglia in the injured spinal cord. Behavioral analysis revealed the locomotor functions of DC-implanted mice to have recovered significantly as compared to those of control mice. Our results suggest that DC-implantation exerts trophic effects, including activation of endogenous NSPCs, leading to repair of the injured adult spinal cord.

Nestin expression after experimental intracerebral hemorrhage

The current study examines nestin expression after intracerebral hemorrhage (ICH), the role of different blood components in nestin upregulation, and the possibility that low doses of thrombin that induce tolerance to brain injury (thrombin preconditioning) might also induce nestin expression. Adult male Sprague-Dawley rats received an intracaudate injection of either whole blood, thrombin (1 or 5 U) or red blood cells (RBCs). Animals were sacrificed for single and double labeling immunohistochemistry to identify which cells express nestin, and for Western blotting to quantify nestin expression. By immunohistochemistry, nestin immunoreactivity was present in large numbers of astrocytes, surrounding the hematoma from day 3 to 1 week after ICH. After 2 weeks, nestin immunoreactivity was co-localized with a neuronal marker (neuronal specific enolase). By Western blot analysis, nestin was strongly expressed at day 3 (P<0.01) and 1 week (P<0.01), and expression persisted for at least 1 month (P<0.05). Intracerebral injection of thrombin or lysed RBCs resulted in a marked increase in nestin expression. Interestingly, injection of a low dose of thrombin that induces brain tolerance also upregulated nestin. The ICH-induced nestin expression in astrocytes may reflect an early response of these cells to injury, while the delayed expression in neurons might be a part of the adaptative response to injury perhaps leading to recovery of function. Nestin induction by a low dose of thrombin suggests that specific receptor-mediated pathways are involved in inducing nestin expression and that nestin may play a role in thrombin preconditioning.