Early Postnatal Migration and Development of Layer II Pyramidal Neurons in the Rodent Cingulate/Retrosplenial Cortex

The cingulate and retrosplenial regions are major components of the dorsomedial (dm) limbic cortex and have been implicated in a range of cognitive functions such as emotion, attention, and spatial memory. While the structure and connectivity of these cortices are well characterized, little is known about their development. Notably, the timing and mode of migration that govern the appropriate positioning of late-born neurons remain unknown. Here, we analyzed migratory events during the early postnatal period from ventricular/subventricular zone (VZ/SVZ) to the cerebral cortex by transducing neuronal precursors in the VZ/SVZ of newborn rats/mice with Tomato/green fluorescent protein-encoding lentivectors. We have identified a pool of postmitotic pyramidal precursors in the dm part of the neonatal VZ/SVZ that migrate into the medial limbic cortex during the first postnatal week. Time-lapse imaging demonstrates that these cells migrate on radial glial fibers by locomotion and display morphological and behavioral changes as they travel through the white matter and enter into the cortical gray matter. In the granular retrosplenial cortex, these cells give rise to a Satb2+ pyramidal subtype and develop dendritic bundles in layer I. Our observations provide the first insight into the patterns and dynamics of cell migration into the medial limbic corte

Expression of FGF-2 in neural progenitor cells enhances their potential for cellular brain repair in the rodent cortex

Strategies to enhance the capacity of grafted stem/progenitors cells to generate multipotential, proliferative and migrating pools of cells in the postnatal brain could be crucial for structural repair after brain damage. We investigated whether the over-expression of basic fibroblast growth factor 2 (FGF-2) in neural progenitor cells (NPCs) could provide a robust source of migrating NPCs for tissue repair in the rat cerebral cortex. Using live imaging we provide direct evidence that FGF-2 over-expression significantly enhances the migratory capacity of grafted NPCs in complex 3D structures, such as cortical slices. Furthermore, we show that the migratory as well as proliferative properties of FGF-2 over-expressing NPCs are maintained after in vivo transplantation. Importantly, after transplantation into a neonatal ischaemic cortex, FGF-2 over-expressing NPCs efficiently invade the injured cortex and generate an increased pool of immature neurons available for brain repair. Differentiation of progenitor cells into immature neurons was correlated with a gradual down-regulation of the FGF-2 transgene. These results reveal an important role for FGF-2 in regulating NPCs functions when interacting with the host tissue and offer a potential strategy to generate a robust source of migrating and immature progenitors for repairing a neonatal ischaemic corte

Manipulation to improve repair capacities of transplanted neural stem/progenitor cells in the cerebral cortex

Le cortex cérébral adulte possède une capacité de régénération très limitée. Néanmoins, la présence de progéniteurs neuronaux dans des zones particulières où la neurogénèse est maintenue suggère que ces cellules pourraient être utilisées à des fins thérapeutiques. Actuellement, deux stratégies sont envisagées pour régénérer les zones lésées : la transplantation cellulaire et le recrutement de progéniteurs présents dans le tissu. Dans la première partie, nous démontrons que la surexpression de FGF-2 dans les progéniteurs neuronaux transplantés augmente de manière significative leur capacité de s'associer avec les vaisseaux du tissu hôte. Dans la deuxième partie, nous démontrons que la surexpression d'EMMPRIN (extracellular matrix metalloproteinase inducer) dans les progéniteurs de la zone sous-ventriculaire augmente leur recrutement dans le cortex lésé. Pour conclure, nos résultats révèlent que la modification de l'expression génétique dans les progéniteurs neuronaux est une approche intéressante et valable pour améliorer leur potentiel en vue de thérapies cellulaires

Matrix metalloproteinases and diseases of the central nervous system with a special emphasis on ischemic brain

Matrix metalloproteinases (MMPs) are involved in the pathogenesis of several diseases of the CNS, that share common pathophysiological processes, such as blood-brain barrier (BBB) disruption, oxidative stress, remodeling of the extracellular matrix (ECM) and inflammation. In ischemic brain injury, MMPs are implicated in various stages of the disease. Early after the onset of ischemia, MMPs contribute to the disruption of the BBB leading to vasogenic edema and to the influx of leucocytes into the CNS. The ability of MMPs to digest the basal lamina of capillaries increases the risk of hemorrhagic transformation of the ischemic tissue. During the acute ischemic phase, maintenance of the ECM is essential for neuronal survival. However, ECM degradation and its reconstitution are critical to tissue recovery. MMPs as a key modulator of ECM homeostasis play a role in the cascades leading to neuronal cell death and tissue regeneration. This pleiotropic implication of MMPs in brain injury has open new areas of investigation, which should lead to innovative therapeutic strategies. Yet MMPs may have a detrimental or beneficial role depending on the stage of brain injury. Simple therapeutic strategies based on MMP inhibition have thus little chance to favorably alter prognosis

Relationship of Grafted FGF-2 Overexpressing Neural Stem/Progenitor Cells with the Vasculature in the Cerebral Cortex

Neural stem/progenitor cells (NPCs) overexpressing fibroblast growth factor 2 (FGF-2) have the distinct tendency to associate with the vasculature and establish multiple proliferative clusters in the perivascular environment after transplantation into the cerebral cortex. Strikingly, the vascular clusters of progenitor cells give rise to immature neurons after ischemic injury, raising prospect for the formation of ectopic neurogenic niches for repair. Here, we investigated the spatial relationship of perivascular clusters with the host vascular structures. FGF-2-GFP-transduced NPCs were transplanted into the intact somatosensory rat cortex. Confocal microscopic analysis revealed that grafted cells preferentially contacted with venules at sites with aquaporin-4-positive astrocytic endfeets and avoided contacts with desmin-positive pericytes. Electronmicroscopic analysis confirmed that grafted cells preferentially contact with astroglial endfeeds and only a minority of them reaches the endothelial basal membrane. These results provide new insights into the fine structure and anatomical relation of grafted FGF-2-transduced NPCs with the host vasculature

Early postnatal migration and development of layer II pyramidal neurons in the rodent cingulate/retrosplenial cortex

The cingulate and retrosplenial regions are major components of the dorsomedial (dm) limbic cortex and have been implicated in a range of cognitive functions such as emotion, attention, and spatial memory. While the structure and connectivity of these cortices are well characterized, little is known about their development. Notably, the timing and mode of migration that govern the appropriate positioning of late-born neurons remain unknown. Here, we analyzed migratory events during the early postnatal period from ventricular/subventricular zone (VZ/SVZ) to the cerebral cortex by transducing neuronal precursors in the VZ/SVZ of newborn rats/mice with Tomato/green fluorescent protein-encoding lentivectors. We have identified a pool of postmitotic pyramidal precursors in the dm part of the neonatal VZ/SVZ that migrate into the medial limbic cortex during the first postnatal week. Time-lapse imaging demonstrates that these cells migrate on radial glial fibers by locomotion and display morphological and behavioral changes as they travel through the white matter and enter into the cortical gray matter. In the granular retrosplenial cortex, these cells give rise to a Satb2+ pyramidal subtype and develop dendritic bundles in layer I. Our observations provide the first insight into the patterns and dynamics of cell migration into the medial limbic cortex

Fibroblast growth factor-2 overexpression in transplanted neural progenitors promotes perivascular cluster formation with a neurogenic potential

Stem/progenitor cell-based therapies hold promises for repairing the damaged nervous system. However, the efficiency of these approaches for neuronal replacement remains very limited. A major challenge is to develop pretransplant cell manipulations that may promote the survival, engraftment, and differentiation of transplanted cells. Here, we investigated whether overexpression of fibroblast growth factor-2 (FGF-2) in grafted neural progenitors could improve their integration in the host tissue. We show that FGF-2-transduced progenitors grafted in the early postnatal rat cortex have the distinct tendency to associate with the vasculature and establish multiple proliferative clusters in the perivascular environment. The contact with vessels appears to be critical for maintaining progenitor cells in an undifferentiated and proliferative phenotype in the intact cortex. Strikingly, perivascular clusters of FGF-2 expressing cells seem to supply immature neurons in an ischemic environment. Our data provide evidence that engineering neural progenitors to overexpress FGF-2 may be a suitable strategy to improve the integration of grafted neural progenitor cells with the host vasculature thereby generating neurovascular clusters with a neurogenic potential for brain repair

EMMPRIN overexpression in SVZ neural progenitor cells increases their migration towards ischemic cortex

Stimulation of endogenous neurogenesis and recruitment of neural progenitors from the subventricular zone (SVZ) neurogenic site may represent a useful strategy to improve regeneration in the ischemic cortex. Here, we tested whether transgenic overexpression of extracellular matrix metalloproteinase inducer (EMMPRIN), the regulator of matrix metalloproteinases (MMPs) expression, in endogenous neural progenitor cells (NPCs) in the subventricular zone (SVZ) could increase migration towards ischemic injury. For this purpose, we applied a lentivector-mediated gene transfer system. We found that EMMPRIN-transduced progenitors exhibited enhanced MMP-2 activity in vitro and showed improved motility in 3D collagen gel as well as in cortical slices. Using a rat model of neonatal ischemia, we showed that EMMPRIN overexpressing SVZ cells invade the injured cortical tissue more efficiently than controls. Our results suggest that EMMPRIN overexpression could be suitable approach to improve capacities of endogenous or transplanted progenitors to invade the injured cortex

Asymmetric Synthesis and Catalytic Activity of 3‑Methyl-β-proline in Enantioselective <i>anti</i>-Mannich-type Reactions

Enantiomerically pure 3-methyl-β-proline was synthesized using an asymmetric phase-transfer-catalyzed alkylation of a cyanopropanoate to establish the all-carbon stereogenic center. The catalytic activity of 3-methyl-β-proline in the Mannich-type reaction between a glyoxylate imine and ketones/aldehydes was subsequently investigated. The catalyst was designed and found to be more soluble in nonpolar organic solvents relative to the unsubstituted β-proline catalyst, and as a result allowed for added flexibility during optimization efforts. This work culminated in the development of a highly <i>anti</i>-diastereo- and enantioselective process employing low catalyst loading