Prospective Approach to Deciphering the Impact of Intercellular Mitochondrial Transfer from Human Neural Stem Cells and Brain Tumor-Initiating Cells to Neighboring Astrocytes

The communication between neural stem cells (NSCs) and surrounding astrocytes is essential for the homeostasis of the NSC niche. Intercellular mitochondrial transfer, a unique communication system that utilizes the formation of tunneling nanotubes for targeted mitochondrial transfer be-tween donor and recipient cells, has recently been identified in a wide range of cell types. Intercel-lular mitochondrial transfer has also been observed between different types of cancer stem cells (CSCs) and their neighboring cells, including brain CSCs and astrocytes. CSC mitochondrial transfer significantly enhances overall tumor progression by reprogramming neighboring cells. Despite the urgent need to investigate this newly identified phenomenon, mitochondrial transfer in the central nervous system remains largely uncharacterized. In this study, we found evidence of intercellular mitochondrial transfer from human NSCs and from brain CSCs, also known as brain tumor-initiating cells (BTICs), to astrocytes in co-culture experiments. Both NSC and BTIC mito-chondria triggered similar transcriptome changes upon transplantation into the recipient astro-cytes. In contrast to NSCs, the transplanted mitochondria from BTICs had a significant prolifera-tive effect on the recipient astrocytes. This study forms the basis for mechanistically deciphering the impact of intercellular mitochondrial transfer on recipient astrocytes, which will potentially provide us with new insights into the mechanisms of mitochondrial retrograde signaling. Overall design: Astrocytes were transplanted with mitochondria that was extracted from Radia Glia (RG) cells or Brain tumor initiating cells (BTIC), that were compared with the non-transplanted astrocytes as a control. The RNA was extracted from the cells after 7 days of cell culture with the transplanted mitochondria.

神经干细胞（neural stem cells, NSCs）与周围星形胶质细胞的通讯，是维持神经干细胞巢（neural stem cell niche, NSC niche）稳态的关键。细胞间线粒体转移是一类独特的细胞通讯方式，通过形成隧道纳米管（tunneling nanotubes）实现供体细胞与受体细胞间的靶向线粒体转移，目前已在多种细胞类型中被发现。不同类型的癌症干细胞（cancer stem cells, CSCs）与其邻近细胞之间也可观察到细胞间线粒体转移现象，其中包括脑癌干细胞与星形胶质细胞。癌干细胞介导的线粒体转移可通过重编程邻近细胞，显著促进肿瘤整体进展。尽管学界亟需对这一新发现的现象开展研究，但中枢神经系统内的线粒体转移仍在很大程度上未被阐明。
本研究通过共培养实验，证实了人神经干细胞与脑癌干细胞（又称脑肿瘤起始细胞（brain tumor-initiating cells, BTICs））均可向星形胶质细胞发生细胞间线粒体转移。无论是神经干细胞还是脑肿瘤起始细胞来源的线粒体，在被移植至受体星形胶质细胞后，均会引发相似的转录组变化。与神经干细胞不同，脑肿瘤起始细胞来源的移植线粒体可对受体星形胶质细胞产生显著的增殖促进效应。本研究为解析细胞间线粒体转移对受体星形胶质细胞的影响奠定了机制研究基础，有望为线粒体逆行信号传导的机制提供全新见解。
实验整体设计：将提取自放射状胶质细胞（Radia Glia, RG）或脑肿瘤起始细胞（BTICs）的线粒体移植至星形胶质细胞，以未进行线粒体移植的星形胶质细胞作为对照。在完成线粒体移植并培养7天后，提取细胞RNA用于后续分析。