[Show abstract][Hide abstract] ABSTRACT: Substantial advances have been made in the last decade on our understanding of the basic physiology underlying neurogenesis in the postnatal mammalian brain. The bulk of the work in this area has been based on analysis of the adult brain. Relatively less is known about the capacity for neurogenesis in specific structures within the neonatal brain. Here we report that the production of medium spiny striatal projection neurons extends into the early neonatal period under normal physiological conditions in the rat brain. Birth-dating of newborn cells with bromo-deoxy-uridine at postnatal days 0, 2 and 5 showed a peak production close to birth, which sharply declined at the later time-points. Additionally, there was a low-level but stable contribution of neurons with interneuron identity over the same time-period. Importantly, retroviral labeling of new striatal projection neurons with green fluorescent protein showed long term survival and terminal differentiation with characteristic morphology, including highly elaborated spiny dendrites, and appropriate axonal targeting of the globus pallidus and midbrain. This latent period of striatal neurogenesis in the early neonatal brain represents an interesting target for regenerative approaches aimed at restoring striatal circuitry in perinatal pathologies, such as hypoxic and ischemic damage associated with cerebral palsy.
The Journal of Physiology 11/2012; 591(1). DOI:10.1113/jphysiol.2012.246397 · 5.04 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Human pluripotent stem cells have the capacity for directed differentiation into a wide variety of neuronal subtypes that may be useful for brain repair. While a substantial body of research has lead to a detailed understanding of the ability of neurons in fetal tissue grafts to structurally and functionally integrate after intra-cerebral transplantation, we are only just beginning to understand the in vivo properties of neurons derived from human pluripotent stem cells. Here we have utilized the human embryonic stem (ES) cell line Envy, which constitutively expresses green fluorescent protein (GFP), in order to study the in vivo properties of neurons derived from human ES cells. Rapid and efficient neural induction, followed by differentiation as neurospheres resulted in a GFP+ neural precursor population with traits of neuroepithelial and dorsal forebrain identity. Ten weeks after transplantation into neonatal rats, GFP+ fiber patterns revealed extensive axonal growth in the host brain, particularly along host white matter tracts, although innervation of adjacent nuclei was limited. The grafts were composed of a mix of neural cell types including differentiated neurons and glia, but also dividing neural progenitors and migrating neuroblasts, indicating an incomplete state of maturation at 10 weeks. This was reflected in patch-clamp recordings showing stereotypical properties appropriate for mature functional neurons, including the ability to generate action potentials, as well profiles consistent for more immature neurons. These findings illustrate the intrinsic capacity for neurons derived from human ES cells to integrate at a structural and functional level following transplantation.