Publication: Estudio de la neurogénesis en necropsias procedentes de pacientes con esclerosis lateral amiotrófica
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2017-10-03
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Universidad Complutense de Madrid
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Abstract
Ramón y Cajal introdujo el concepto de que la carga de neuronas del sistema nervioso central se mantiene inmutable tras el nacimiento (Ramon y Cajal 1928) y esta idea se consideró uno de los axiomas de las neurociencias hasta nuestros días. La posibilidad de que la neurogénesis se mantuviera en la edad adulta se apuntó por primera vez en estudios realizados en la zona subgranular del giro dentado del hipocampo de pájaros (Nottebohm 1989) y precisó de tiempo y numerosos estudios hasta que se aceptó en el total de los mamíferos y en el humano (Altman 1962, Yuan et al. 2014). Existen dos nichos neurogénicos claramente establecidos y conservados a lo largo de las especies a los que se llama nichos neurogénicos clásicos: la zona subventricular y la zona subgranular del giro dentado. La zona subventricular se encuentra adyacente al ventriculo lateral y está formada por tres capas: la capa ependimaria, la capa hipocelular o GAP y la capa astrocitaria o ribbon. La neurogénesis en la SVZ pasa por una serie de fases celulares partiendo de las células neurales progenitoras proliferativas que se encuentran en una fase de división y proliferación y que tienen marcadores gliales (Kriegstein y Alvarez- Buylla 2009), células tipo B, a las células neurales progenitoras que todavía mantienen alguna carácterística glial pero ya presentan alguna diferenciación neuronal (células tipo C) a los neuroblastos (tipo A)...
The number of neurons in the central nervous system was considered immutable after Ramon y Cajal’s works (Ramon y Cajal 1928). The concept of adult neurogenesis was introduced after some studies in the brain of adult birds (Nottebohm 1989), more evidence was needed until this concept was accepted for all mammals and even in humans (Altman 1962, Yuan et al. 2014). Two neurogenic niches are widely accepted: subventricular zone and subgranular zone in girus dentatus. These niches are conserved along the evolution of species. Subventricular zone is located near the lateral ventricle. It is formed by three layers: ependymal layer, GAP layer (hypocellular) and ribbon layer (astrocytic). Three types of stem cells are described in the SVZ: neural proliferative progenitor cells (that stain for glial markers) (Kriegstein y Alvarez-Buylla 2009) -type B-, neural pluripotential cells with some glial characteristics but also some neuronal differentiation (type C cells) and neuroblasts (type A cells). Some of these cells die after their formation and this survival phase is probably the most important one in the regulation of neurogenesis (Ribeiro Xavier et al. 2015). Those cells that are able to survive migrate and, at least in mammals, take the rostral migratory stream (RMS) to olfactory bulb (Liu y Rao 2003). RMS existence in humans is not accepted for all authors (Curtis et al. 2007c). Proliferation rate in SVZ is much more bigger than in SGZ and the number of stem cells in the niche is also bigger. However this fact is discussed in the healthy human. Subgranular zone is the second classic neurogenic niche. In this niche neural there are also three types of stem cells and they also come of glial cells: neural progenitor proliferative stem cells, type 1 or type A, neural pluripotential cells, type 2 or type D1 and neurobasts, type 3 or type D3. Again these stem cells have a survival phase and then they integrate as granular neurons...
The number of neurons in the central nervous system was considered immutable after Ramon y Cajal’s works (Ramon y Cajal 1928). The concept of adult neurogenesis was introduced after some studies in the brain of adult birds (Nottebohm 1989), more evidence was needed until this concept was accepted for all mammals and even in humans (Altman 1962, Yuan et al. 2014). Two neurogenic niches are widely accepted: subventricular zone and subgranular zone in girus dentatus. These niches are conserved along the evolution of species. Subventricular zone is located near the lateral ventricle. It is formed by three layers: ependymal layer, GAP layer (hypocellular) and ribbon layer (astrocytic). Three types of stem cells are described in the SVZ: neural proliferative progenitor cells (that stain for glial markers) (Kriegstein y Alvarez-Buylla 2009) -type B-, neural pluripotential cells with some glial characteristics but also some neuronal differentiation (type C cells) and neuroblasts (type A cells). Some of these cells die after their formation and this survival phase is probably the most important one in the regulation of neurogenesis (Ribeiro Xavier et al. 2015). Those cells that are able to survive migrate and, at least in mammals, take the rostral migratory stream (RMS) to olfactory bulb (Liu y Rao 2003). RMS existence in humans is not accepted for all authors (Curtis et al. 2007c). Proliferation rate in SVZ is much more bigger than in SGZ and the number of stem cells in the niche is also bigger. However this fact is discussed in the healthy human. Subgranular zone is the second classic neurogenic niche. In this niche neural there are also three types of stem cells and they also come of glial cells: neural progenitor proliferative stem cells, type 1 or type A, neural pluripotential cells, type 2 or type D1 and neurobasts, type 3 or type D3. Again these stem cells have a survival phase and then they integrate as granular neurons...
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Tesis inédita de la Universidad Complutense de Madrid, Facultad de Medicina, Departamento de Psiquiatría, leída el 14/01/2016