Neurogenesis continues throughout adulthood in the subventricular zone, hippocampal subgranular zone, and the hypothalamic median eminence (ME) and the adjacent medio-basal hypothalamus. The ME is one of the circumventricular organs (CVO), which are specialized brain areas characterized by an incomplete blood–brain barrier and, thus, are involved in mediating communication between the central nervous system and the periphery. Additional CVOs include the organum vasculosum laminae terminalis (OVLT) and the subfornical organs (SFO). Previous studies have demonstrated that the ME contains neural stem cells (NSCs) capable of generating new neurons and glia in the adult brain. However, it remains unclear whether the OVLT and SFO also contain proliferating cells, the identity of these cells, and their ability to differentiate into mature neurons. Here we show that glial and mural subtypes exhibit NSC characteristics, expressing the endogenous mitotic maker Ki67, and incorporating the exogenous mitotic marker BrdU in the OVLT and SFO of adult rats. Glial cells constitutively proliferating in the SFO comprise NG2 glia, while in the OVLT, both NG2 glia and tanycytes appear to constitute the NSC pool. Furthermore, pericytes, which are mural cells associated with capillaries, also contribute to the pool of cells constitutively proliferating in the OVLT and SFO of adult rats. In addition to these glial and mural cells, a fraction of NSCs containing proliferation markers Ki67 and BrdU also expresses the early postmitotic neuronal marker doublecortin, suggesting that these CVOs comprise newborn neurons. Notably, these neurons can differentiate and express the mature neuronal marker NeuN. These findings establish the sensory CVOs OVLT and SFO as additional neurogenic niches, where the generation of new neurons and glia persists in the adult brain.

中文翻译：

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成年大鼠血管器终板和穹窿下器官的组成性细胞增殖和神经发生

神经发生在整个成年期持续存在于室下区、海马颗粒下区、下丘脑正中隆起（ME）和邻近的下丘脑内侧基底区。 ME 是室周器官 (CVO) 之一，它是一种特殊的大脑区域，其特征是血脑屏障不完整，因此参与调节中枢神经系统和外周神经系统之间的沟通。其他 CVO 包括终板血管器官 (OVLT) 和穹窿下器官 (SFO)。先前的研究表明，ME 含有能够在成人大脑中产生新神经元和神经胶质细胞的神经干细胞 (NSC)。然而，目前尚不清楚 OVLT 和 SFO 是否也含有增殖细胞、这些细胞的身份以及它们分化为成熟神经元的能力。在这里，我们发现胶质细胞和壁细胞亚型表现出 NSC 特征，表达内源性有丝分裂标记 Ki67，并在成年大鼠的 OVLT 和 SFO 中纳入外源有丝分裂标记 BrdU。在 SFO 中持续增殖的神经胶质细胞包括 NG2 神经胶质细胞，而在 OVLT 中，NG2 神经胶质细胞和单胞细胞似乎构成了 NSC 池。此外，周细胞是与毛细血管相关的壁细胞，也有助于成年大鼠 OVLT 和 SFO 中持续增殖的细胞池。除了这些神经胶质细胞和壁细胞外，一部分含有增殖标记物 Ki67 和 BrdU 的 NSC 也表达早期有丝分裂后神经元标记物双皮质素，表明这些 CVO 包含新生神经元。值得注意的是，这些神经元可以分化并表达成熟的神经元标记 NeuN。这些发现将感觉 CVO OVLT 和 SFO 确立为额外的神经源性生态位，新神经元和神经胶质细胞的生成持续存在于成人大脑中。