Circulation of the cerebrospinal fluid (CSF) contributes to body axis formation and brain development. Here, we investigated the unexplained origins of the CSF flow bidirectionality in the central canal of the spinal cord of 30 hpf zebrafish embryos and its impact on development. Experiments combined with modeling and simulations demonstrate that the CSF flow is generated locally by caudally-polarized motile cilia along the ventral wall of the central canal. The closed geometry of the canal imposes the average flow rate to be null, explaining the reported bidirectionality. We also demonstrate that at this early stage, motile cilia ensure the proper formation of the central canal. Furthermore, we demonstrate that the bidirectional flow accelerates the transport of particles in the CSF via a coupled convective-diffusive transport process. Our study demonstrates that cilia activity combined with muscle contractions sustain the long-range transport of extracellular lipidic particles, enabling embryonic growth.

中文翻译：

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脑脊液双向流动在中央管中的起源和作用

脑脊液（CSF）的循环有助于体轴形成和大脑发育。在这里，我们调查了30 hpf斑马鱼胚胎的脊髓中央管中CSF流双向的无法解释的起源及其对发育的影响。实验与建模和模拟相结合表明，脑脊液血流是由沿中心管腹壁的尾极化运动性纤毛局部产生的。运河的封闭几何形状使平均流速为零，从而解释了所报告的双向性。我们还证明，在此早期阶段，活动性纤毛可确保中央管的正确形成。此外，我们证明了双向流通过耦合的对流-扩散传输过程加速了CSF中粒子的传输。