Abstract

Docosahexaenoic acid (DHA, 22:6n-3), a predominant, omega-3 (n-3) structural polyunsaturated fatty acid (PUFA) in the brain, has been shown to play an important role in the development and function of neural cells, and is obtained from dietary sources. Recent studies suggest that DHA can promote the formation of new neurons from adult rat NSCs in vivo, but it has not yet been determined how DHA affects embryonic NSCs in vivo. This is particularly of interest since dietary DHA supplementation is recommended during pregnancy by many clinicians, but the exact action of DHA is unknown. This study examined the specific role of DHA and other PUFAs on NSCs of chick embryos in vivo to better understand the impact DHA has on neuronal cell birth (neurogenesis). By administering PUFA solutions of DHA, alpha-linolenic acid (ALA, 18:3n-3), arachidonic acid (ARA, 20:4n-6), and linoleic acid (LA, 18:2n-6) directly into the neural tube of in vivo chick embryos, the effects that these different PUFAs have on the NSCs of the neural tube compared to a vehicle control (bovine albumin serum) have been examined. With the use of immunohistochemistry, we monitored changes in the number of mature neurons using neuronal marker NeuN and changes in cell cycle arrest using cell cycle inhibitor marker p27kip1 to gain better insight on how DHA affects neurogenesis. After allowing embryonic development for 44 hours and analyzing samples using standard anatomical quantification techniques, we were able to conclude the following: introducing the PUFA directly to the neural tube, compared to the control, resulted in a significant change in the number of NeuN positive cells in the DHA condition, a greater number of NeuN positive cells in the ALA condition, and greater numbers of p27kip1 positive cells in the DHA condition. This data suggests that DHA and its chemical precursor, ALA, may have an effect on neurogenesis of embryonic neural stem cells in vivo. Other evidence shows that DHA influences neurogenesis in vivo in adult rat stem cells and in vitro in embryonic stem cells, but our unique experiment observes the effects of DHA and its precursor on neuronal embryonic stem cells that are developing in vivo when n-3 PUFA is introduced. An increase in neurogenesis under these conditions could suggest that using n-3 PUFAs DHA or ALA as prenatal supplements may be beneficial for promoting the birth of neurons in developing embryos. However, a variation in the size of embryos between conditions in this experiment could account for the significant increase in NeuN positive cells and greater number of p27kip1 positive cells in the DHA condition compared to the control condition. For this reason, this experiment has room for further investigation to control such variables.