Human induced pluripotent stem cell (hiPSC)-derived in vitro neural and organoid models resemble fetal, rather than adult brain properties, indicating that currently applied cultivation media and supplements are insufficient to achieve neural maturation beyond the fetal stage. In vivo, cerebrospinal fluid molecules are regulating the transition of the immature fetal human brain into a mature adult brain. By culturing hiPSC-3D neural aggregates in human cerebrospinal fluid (hCSF) obtained from healthy adult individuals, we demonstrate that hCSF rapidly triggers neurogenesis, gliogenesis, synapse formation, neurite outgrowth, suppresses proliferation of residing neural stem cells, and results in the formation of synchronously active neuronal circuits in vitro within 3 days. Thus, a physiologically relevant and adult brain-like milieu triggers maturation of hiPSC-3D neural aggregates into highly functional neuronal circuits in vitro. The approach presented here opens a new avenue to identify novel physiological factors for the improvement of hiPSC neural in vitro models.

人类诱导的多能干细胞（hiPSC ）衍生的体外神经和类器官模型类似于胎儿，而不是成年人的大脑特性，这表明当前使用的培养基和补充剂不足以在胎儿期后实现神经成熟。在体内，脑脊液分子调节着未成熟的胎儿人脑向成年成人脑的过渡。通过在从健康成人个体获得的人脑脊髓液（hCSF）中培养hiPSC-3D神经聚集体，我们证明了hCSF快速触发神经发生，神经胶质生成，突触形成，神经突向外生长，抑制驻留的神经干细胞的增殖并导致神经干细胞的形成。体外同步活动神经元回路在3天内。因此，在生理上相关且成年的脑样环境触发了hiPSC-3D神经聚集体在体外成熟为高功能神经元回路。本文介绍的方法为鉴定新的生理因素改善hiPSC神经体外模型开辟了一条新途径。