Seki Tatsunori
Department of Anatomy, Juntendo University School of Medicine, Tokyo, Japan.
Anat Sci Int. 2003 Jun;78(2):69-78. doi: 10.1046/j.0022-7722.2003.00043.x.
Neurogenesis continues into adulthood in two distinct regions, the subventricular zone of the forebrain and the subgranular zone of the dentate gyrus. Transplantation experiments have suggested that the two neurogenic regions have a special microenvironment to support the proliferation and differentiation of stem or progenitor cells. As the candidates of the microenvironment, three elements have so far been proposed: (i) astrocytes; (ii) polysialyl neural cell adhesion molecule (PSA-NCAM)-expressing immature neurons; and (iii) blood vessels. In the early developmental process of neurogenesis, newly born cells make clusters within the neurogenic regions and the clusters are found to interact structurally with astrocytes, polysialic acid-expressing immature cells, endothelium and extravascular basal laminae of blood vessels. Furthermore, recent reports have shown that astrocytes support the proliferation and differentiation of stem cells in vitro. These results suggest that these microenvironmental elements contribute to the cell proliferation and differentiation of stem or progenitor cells. However, it remains to be determined how the microenvironmental elements support adult neurogenesis functionally and coordinate with each other.
神经发生在成年期仍会在两个不同区域持续进行，即前脑的室下区和齿状回的颗粒下区。移植实验表明，这两个神经发生区域具有特殊的微环境，以支持干细胞或祖细胞的增殖和分化。作为微环境的候选因素，目前已提出三个要素：（i）星形胶质细胞；（ii）表达多唾液酸神经细胞黏附分子（PSA-NCAM）的未成熟神经元；（iii）血管。在神经发生的早期发育过程中，新生细胞在神经发生区域内形成细胞簇，并且发现这些细胞簇在结构上与星形胶质细胞、表达多唾液酸的未成熟细胞、血管内皮和血管外基膜相互作用。此外，最近的报告表明，星形胶质细胞在体外支持干细胞的增殖和分化。这些结果表明，这些微环境要素有助于干细胞或祖细胞的增殖和分化。然而，微环境要素如何在功能上支持成体神经发生以及它们之间如何相互协调仍有待确定。
