Effect of docosahexaenoic acid on the differentiation of neural steam cells

二十二碳六烯酸(DHA)是哺乳动物大脑中的主要结构脂类之一，在脑神经元的发育和功能中起着至关重要的作用。我们先前报道，长期给予DHA可增强幼年和老年大鼠的长期记忆，饮食DHA对淀粉样蛋白b灌流大鼠的空间认知学习能力损害具有预防和改善作用。这些发现表明，DHA在终生中枢神经系统的发育和功能中起着至关重要的作用。本研究探讨了DHA对体外和体内神经干细胞(NSCs)神经分化的影响，以及对培养细胞碱性螺旋-环-螺旋(BHLH)转录因子表达的影响。方法将15.5d龄大鼠胚胎NSCs培养成神经球，在不同条件下培养。从每种培养物中提取总RNA，并进行RT-PCR(Hes1、Hes5、Neug…结果与结论1)DHA组培养的NSCs较对照组Tuj-1阳性神经元数量显著增加，新生神经元形态较对照组成熟，DHA可显著降低有丝分裂标志物5-溴-2-脱氧尿嘧啶核苷的掺入比例。此外，饮食中添加DHA可显著增加成年大鼠齿状回颗粒细胞层中5-溴-2-脱氧尿苷(+)/Neun(+)神经元的数量。这些结果表明，DHA在体外和体内均能有效地促进神经发生。2)与对照组相比，DHA处理NSCs后，Hes1基因的表达明显减少，提示DHA通过调节bHLH转录因子的表达水平，促进神经元分化。较少

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