Effect of docosahexaenoic acid on the differentiation of neural steam cells

二十二碳六烯酸（DHA）是哺乳动物脑内的主要结构脂质之一，对脑神经元的发育和功能起着至关重要的作用。我们以前报道过，长期给予DHA可增强年轻和老年大鼠的长期记忆，膳食DHA对淀粉样蛋白b注入大鼠的空间认知学习能力障碍具有预防和改善作用。这些发现表明，DHA在整个生命过程中对CNS的发育和功能起着至关重要的作用。在这项研究中，我们研究了1）DHA在体内和体外对神经干细胞（NSCs）神经分化的影响，以及2）对培养细胞的碱性螺旋-环-螺旋（bHLH）转录因子表达的影响。<Methods>从15.5日龄大鼠胚胎中获得的神经干细胞作为神经球繁殖，并在有或无DHA的不同条件下培养。从含有或不含DHA的每种培养物中制备总RNA，并进行RT-PCR（Hes 1，Hes 5，neurog ...更多信息 enin1、Mash1或NeuroD）。<Results and Conclusions>1）与对照组相比，DHA能显著增加培养的NSCs上Tuj 1阳性神经元的数量，且DHA组新生神经元的形态较对照组成熟，DHA能显著降低有丝分裂标记物5-溴-2-脱氧尿苷的掺入率。此外，饮食中给予DHA显著增加了成年大鼠齿状回颗粒细胞层中5-溴-2-脱氧尿苷（+）/NeuN（+）新生神经元的数量。2）与对照组相比，DHA处理NSCs后Hes1 mRNA表达降低，提示DHA通过调节bHLH转录因子的表达水平促进神经元分化，提示DHA具有调节海马功能的新特性。少

Docosahexaaenoic acid (DHA), one of the main structural lipids in the mammalian brain, plays crucial roles in the development and function of brain neurons. We previously reported that chronic administration of DHA enhances long-term memory in young and aged rats, and dietary DHA has preventive and ameliorative effects on the impairment of spatial cognition learning ability in amyloid b-infused rats. These findings suggest that DHA plays crucial roles in the development and function of the CNS throughout life. In this study, we examined the 1) effect of DHA on neural differentiation of neural stem cells (NSCs) in vivo and in vitro, and 2) on the expression of basic helix-loop-helix (bHLH) transcriptional factors of the cultured cells.<Methods> NSCs obtained from 15.5-day-old rat embryos were propagated as neurospheres and cultured under differential conditions with or without DHA. Total RNA was prepared from each culture with or without DHA, and was performed RT-PCR (Hes1, Hes5, neurog … More enin1, Mash1 or NeuroD).<Results and Conclusions> 1) DHA significantly increased the number of Tuj 1-positive neurons compared with the control on cultured NSCs, and the newborn neurons in the DHA groups were morphologically more mature than in the control, DHA significantly decreased the incorporation ratio of 5-bromo-2-deoxyuridine, the mitotic division marker, during the first 24h periods. Furthermore, dietary administration of DHA significantly increased the number of 5-bromo-2-deoxyuridine(+)/NeuN(+) newborn neurons in the granule cell layer of the dentate gyrus in adult rats. These results suggested that DHA effectively promotes nuerogenesis both in vitro and in vivo.2) Treatment of NSCs with DHA decreased the expression of Hes1 mRNA compared with that of control, suggesting that DHA stimulates neuronal differentiation by modulating expression levels of bHLH transcription factors.The present study suggests that DHA has the new property of modulating hippocampal function regulated by neurogenesis. Less