In vivo and in vitro Approaches for the Study of Adult Neurogenesis in Light, Confocal, and Electron Microscopy

Since their beginning, morphological and functional studies of the mammalian central nervous system must deal with the complexity of the nervous tissue. Recent studies, by revealing the existence of neurogenesis throughout life, introduced a new aspect of complexity. Adult neurogenic sites are heterogeneous systems involving stem cell niches which contain actively dividing cells, migration routes, and processes of cell differentiation/integration within the target regions. Since the location of neurogenic sites is restricted to specific brain regions, their study in vivo requires detailed morphological analyses. Although this complexity can be reduced in many in vitro approaches, stem cells and their progeny strongly depend on the tissue environment. Thus, ex vivo approaches such as tissue explants and organotypic cultures can be employed as an alternative way to investigate stem cell niches.