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Neonatal stroke is a leading cause of long-term disability and currently available rehabilitation treatments are insufficient to promote recovery. Activating neural precursor cells (NPCs) in adult rodents, in combination with rehabilitation, can accelerate functional recovery following stroke. Here, we describe a novel method of constraint-induced movement therapy (CIMT) in a rodent model of neonatal stroke that leads to improved functional outcomes, and we asked whether the recovery was correlated with expansion of NPCs. A hypoxia/ischemia (H/I) injury was induced on postnatal day 8 (PND8) via unilateral carotid artery ligation followed by systemic hypoxia. One week and two weeks post-H/I, CIMT was administered in the form of 3 botulinum toxin (Botox) injections, which induced temporary paralysis in the unaffected limb. Functional recovery was assessed using the foot fault task. NPC proliferation was assessed using the neurosphere assay and EdU immunohistochemistry. We found that neonatal H/I injury alone expands the NPC pool by >2.5-fold relative to controls. We determined that using Botox injections as a method to provide CIMT results in significant functional motor recovery after H/I. However, CIMT does not lead to enhanced NPC activation or migration into the injured parenchyma in vivo. At the time of functional recovery, increased numbers of proliferating inflammatory cells were found within the injured motor cortex. Together, these findings suggest that NPC activation following CIMT does not account for the observed functional improvement and suggests that CIMT-mediated modification of the CNS inflammatory response may play a role in the motor recovery.

Stroke is the leading cause of adult disability with few treatment options for stroke survivors. Astrocyte reprogramming to neurons enables the targeted in vivo generation of new cells at the site of injury and represents a novel approach for brain repair. A number of studies have demonstrated successful conversion of astrocytes to neurons in various models of brain injury and disease; however, the impact of this strategy on tissue and functional outcome following stroke is not well established. Using AAV delivery of the transcription factor NeuroD1, we reprogrammed astrocytes 7 days after endothelin-1 induced cortical stroke, and studied the long-term cellular and functional outcomes. We found that by 63 days post-stroke, 20% of neurons in the perilesional cortex were reprogrammed. Furthermore, reprogrammed neurons had matured into regionally appropriate neuronal subtypes. Importantly, this treatment was associated with improved functional outcome using the foot fault test and gait analysis. Together, our findings indicate that in vivo reprogramming is a promising regenerative approach for stroke repair.

Since the original isolation of neural stem cells (NSCs) in the adult mammalian brain, further work has revealed a heterogeneity in the NSC pool. Our previous work characterized a distinct, Oct4 expressing, NSC population in the periventricular region, through development and into adulthood. We hypothesized that this population is upstream in lineage to the more abundant, well documented, GFAP expressing NSC. Herein, we show that Oct4 expressing NSCs give rise to neurons, astrocytes and oligodendrocytes throughout the developing brain. Further, transgenic inducible mouse models demonstrate that the rare Oct4 expressing NSCs undergo asymmetric divisions to give rise to GFAP expressing NSCs in naïve and injured brains. This lineage relationship between distinct NSC pools contributes significantly to an understanding of neural development, the NSC lineage in vivo and has implications for neural repair.

Temporally distinct populations of neural stem cells (NSCs; embryonic and adult) display the cardinal stem cell properties of self-renewal and multipotentiality; however, their relative frequency and cell kinetics vary through development and into old age. We asked whether changes in NSC behavior could be accounted for by changes in environmental signals over time. We identified a prosurvival signaling cascade that enhances adult-derived NSC survival using cues released from embryonic neurons. Specifically, we demonstrate that stromal-cell-derived factor-1α (SDF-1α) released by embryonic neurons leads to upregulation of neuronal nitric oxide synthase in adult neural precursor cells. The resulting increase in nitric oxide leads to the upregulation of the stem cell factor (SCF) receptor ckit on adult NSCs (ANSCs). SCF released from embryonic neurons results in enhanced NSC survival. Using both in vitro and in vivo assays, we have demonstrated expansion of the size of the NSC pool through this pathway, indicating that ANSCs retain their ability to respond to embryonic-derived cues into adulthood.

SummaryThe mechanisms that regulate the establishment of adult stem cell pools during normal and perturbed mammalian development are still largely unknown. Here, we asked whether a maternal cytokine surge, which occurs during human maternal infections and has been implicated in cognitive disorders, might have long-lasting consequences for neural stem cell pools in adult progeny. We show that transient, maternally administered interleukin-6 (IL-6) resulted in an expanded adult forebrain neural precursor pool and perturbed olfactory neurogenesis in offspring months after fetal exposure. This increase is likely the long-term consequence of acute hyperactivation of an endogenous autocrine/paracrine IL-6-dependent self-renewal pathway that normally regulates the number of forebrain neural precursors. These studies therefore identify an IL-6-dependent neural stem cell self-renewal pathway in vivo, and support a model in which transiently increased maternal cytokines can act through this pathway in offspring to deregulate neural precursor biology from embryogenesis throughout life.

Stroke is a neurological disorder that currently has no cure. Intrathecal delivery of growth factors, specifically recombinant human epidermal growth factor (rhEGF), stimulates endogenous neural precursor cells in the subventricular zone (SVZ) and promotes tissue regeneration in animal models of stroke. In this model, rhEGF is delivered with an invasive minipump/catheter system, which causes trauma to the brain. A less invasive strategy is to deliver rhEGF from the brain cortex; however, this requires the protein to diffuse through the brain, from the site of injection to the SVZ. Although this method of delivery has great potential, diffusion is limited by rapid removal from the extracellular space and hence for successful translation into the clinic strategies are needed to increase the diffusion distance. Using integrative optical imaging we investigate diffusion of rhEGF vs. poly(ethylene glycol)-modified rhEGF (PEG-rhEGF) in brain slices of both uninjured and stroke-injured animals. For the first time, we quantitatively show that PEG modification reduces the rate of growth factor elimination by over an order of magnitude. For rhEGF this corresponds to a two to threefold increase in predicted brain penetration distance, which we confirm with in vivo data.

1. The Standard Critique of Structural Adjustment Programmes Outside the field of economics, it is customary among social scientists to deride the World Bank for its neoliberalism. The standard argument is that the structural adjustment programmes (SAPs) favoured by the bank in the 1980s and 1990s sought to impose free market conditions on the less developed countries. However, offering aid in exchange for more international trade, foreign investment, privatization of commerce and industry, the elimination of tariffs and agricultural subsidies, and so forth, did little to stimulate economic growth. World Bank researchers themselves recognize that median per capita income in the less developed countries grew 2.5% in the period 1960-79 (before the advent of SAPs) but languished at 0.0% in the period 1980-98 (in the era of SAPs) (Easterly, 2001). The growing debt burden of less developed countries and falling export commodity prices cancelled out any positive effects the SAPs might have had. Moreover, in many countries, SAPs hurt the poor, which is why in Zambia, for instance, SAP came to stand for satana ali pano, "the devil is among us" (Kufekisa-Akapelwa, 2001), and why some critics thought it ironic that the President of the World Bank, James D. Wolfensohn, should be awarded the Order of the Golden Fleece by the government of Georgia in 1999. Critics also underline the double standard maintained by the wealthy countries that finance the World Bank's activities and support its policies. For example, while in a less developed country like Mexico agricultural subsidies amounted to $1,000 per farmer in 2002, the comparable figures for American, European Union, and Japanese farmers were, respectively, $16,000, $17,000, and $27,000: hardly evidence the rich countries are willing to swallow the medicine they prescribe for the poor. (3) These disparities are no small matter because the reduction or elimination of farm subsidies by the wealthy countries would greatly stimulate agricultural exports and economic growth in the less developed countries (Saunders, 2003). Feminist criticism of SAPs takes a different tack. In the 1980s, UNICEF researchers, among others, noted that mothers with young children are especially vulnerable to the negative effects of structural adjustment (Cornia, Jolly, and Stewart, 1987). In less developed countries, such women are typically saddled with reproductive and domestic work, including buying and preparing food, ensuring the good health of their children, and maximizing their children's educational opportunities. Since the privatization of government services sometimes involves the elimination of basic food subsidies and the introduction of user fees for education and health services, the burden of SAPs falls disproportionately on women with young children. UNICEF therefore called for safety nets that would protect mothers with young children from the whip of the market: free basic health services, literacy programmes, and the like. A more recent and radical feminist critique of SAPs holds that such safety nets reinforce traditional gender roles. From this point of view, young mothers who can take advantage of free basic health services and literacy programmes may be better able to perform their domestic responsibilities, but that only helps to reproduce existing patterns of gender inequality in the household and the larger society. According to the recent feminist critique, the key to reducing gender inequalities in less developed countries lies in identifying and eliminating the male biases of the economic models underlying SAPs (Elson, 1995; Pearson, 2000). These economic models ignore rigidities in the gender division of labour, both in the paid work force and the household. Especially in less developed societies, women and men tend to perform different work roles. Some kinds of work are considered appropriate for women but not for men, and vice-versa. …

Reactive astrocytes (RAs) have been reported to convert to multipotent neural stem cells (NSCs) capable of neurosphere (NS) formation and multilineage differentiation invitro. Using genetic tagging, wedetermined that subventricular zone (SVZ) NSCs give rise to NSs derived from the stroke-injured cortex. We demonstrate that these cells can be isolated from the cortex in two different models of stroke and from different stroke-lesioned cortical regions. Interestingly, SVZ NSCs give rise to a subpopulation of RAs in the cortex that contribute to astrogliosis and scar formation. Last, we show that these SVZ derived RAs can be converted to neurons invivo by forced expression of Ascl1. Identifying the contribution of cells originating from the SVZ to injury repair has implications for neural regeneration strategies.

Stroke is a leading cause of disability with no effective regenerative treatment. One promising strategy for achieving tissue repair involves the stimulation of endogenous neural stem/progenitor cells through sequential delivery of epidermal growth factor (EGF) followed by erythropoietin (EPO). Yet currently available delivery strategies such as intracerebroventricular (ICV) infusion cause significant tissue damage. We designed a novel delivery system that circumvents the blood brain barrier and directly releases growth factors to the brain. Sequential release of the two growth factors is a key in eliciting tissue repair. To control release, we encapsulate pegylated EGF (EGF-PEG) in poly(lactic-co-glycolic acid) (PLGA) nanoparticles and EPO in biphasic microparticles comprised of a PLGA core and a poly(sebacic acid) coating. EGF-PEG and EPO polymeric particles are dispersed in a hyaluronan methylcellulose (HAMC) hydrogel which spatially confines the particles and attenuates the inflammatory response of brain tissue. Our composite-mediated, sequential delivery of EGF-PEG and EPO leads to tissue repair in a mouse stroke model and minimizes damage compared to ICV infusion.

Summary Adult forebrain definitive neural stem cells (NSCs) comprise a subpopulation of GFAP-expressing subependymal cells that arise from embryonic fibroblast growth factor (FGF)-dependent NSCs that are first isolated from the developing brain at E8.5. Embryonic FGF-dependent NSCs are derived from leukemia inhibitory factor (LIF)-responsive, Oct4-expressing primitive NSCs (pNSCs) that are first isolated at E5.5. We report the presence of a rare population of pNCSs in the periventricular region of the adult forebrain. Adult-derived pNSCs (AdpNSCs) are GFAP−, LIF-responsive stem cells that display pNSC properties, including Oct4 expression and the ability to integrate into the inner cell mass of blastocysts. AdpNSCs generate self-renewing, multipotent colonies that give rise to definitive GFAP+ NSCs in vitro and repopulate the subependyma after the ablation of GFAP+ NSCs in vivo. These data support the hypothesis that a rare population of pNSCs is present in the adult brain and is upstream of the GFAP+ NSCs., Highlights • Rare, multipotent, self-renewing, Oct4+ AdpNSCs in the adult brain • AdpNSCs lie upstream of definitive, GFAP-expressing adult NSCs • AdpNSCs repopulate the SE after ablation of GFAP-expressing NSCs • The AdpNSC pool is activated and expands after injury or LIF infusion in vivo, The identification of primitive NSCs that persist in the adult brain redefines the adult NSC lineage. Morshead and colleagues show that these adult-derived primitive NSCs, similar to primitive NSCs found in the developing embryo, express the pluripotency marker Oct4 in vitro and in vivo and give rise to GFAP+ definitive NSCs.

Adult tissues are known to contain rare populations of stem cells with multilineage differentiation potential that are distinct from other resident tissue-specific stem cells. However, whether multilineage stem cells are involved in tissue development is uncertain, primarily because the identification and characterization of these cells in embryonic tissue primordia is not well established. We tested whether stem cells with multilineage potential are present within the early post-gastrula somite tissue. We show that clonally derived precursor cells generate colonies with self-renewal capacity and have both neurogenic and myogenic lineage potential. Somite colonies contain cells that express Sox2, nestin, and Sca1, but do not express genes indicative of somitic mesoderm specification. Furthermore, we demonstrate that this multilineage potential is not due to colony cells with a pluripotent epiblast identity or the selection of p75 receptor-positive neural crest stem cells. Despite utilizing a highly undifferentiated tissue source, colony formation was not enhanced relative to reported estimates of multilineage stem cells from adult muscle, a derivative of the embryonic somite. Thus, our findings suggest that a permissive in vitro environment is sufficient for the isolation of a discrete population of stem cells in the embryonic somite that may represent the earliest developmental precursor to adult muscle multilineage stem cells.