粒線體數目與細胞大小忠實性關聯建立之探討

Abstract

細胞生長(cell growth)是細胞有組織的將外界營養分子合成大量巨分子以增加細胞質量(biomass)的過程，也是驅動細胞增生(cell proliferation)重要的力量。細胞增生過程中，遺傳物質(chromosomes)的複製與內在胞器（e.g., 粒線體、核糖體）之數量變化，以及諸多相關的調節機制都必須保有忠實性(fidelity)，保證所有增生的細胞均與原細胞類似。而盛裝這些物質的容器也就是細胞本體，其大小的調控(size control)亦會受到細胞內、外的動態系統所影響。為達到有效率的累積細胞質量(biomass)之目的，粒線體由原本負責能量提供的角色，轉變為巨分子合成中心，以代謝重整(metabolic reprogram)的途徑支應細胞生長過程的需求。 Saccharomyces cerevisiae可藉由母細胞當作細胞生長的模版，但在哺乳類細胞的生長過程並無此依據，而我們推論哺乳類細胞生長到兩倍大小的過程，可能與粒線體所進行的營養代謝重整有關；此外，粒線體擁有自己的DNA，在細胞生長週期中遵守複製一次且只有一次的原則，其數量亦需符合細胞複製的忠實性。 本篇研究目的為建立粒線體數目(mitochondrial number)與細胞大小控制(cell size control)的連結關係。利用Resveratrol作為影響粒線體數目的主要工具，藉此促使粒線體生合成(biogenesis)增加。 研究結果顯示，當以Resveratrol處理 HeLa細胞時，利用螢光染劑NAO透過流式細胞儀測量粒線體總量，並同時測量forward scatter-width (FSC-W) 來代表細胞大小，發現細胞大小有隨粒線體數目增加呈現變大的現象；而於24小時後移除Resveratrol再進行培養，則發現粒線體數目與細胞大小可恢復正常。若將Resveratrol的處理時間增加至48小時並移除Resveratrol後再次培養，粒線體數目與細胞大小仍維持增加的現象。 藉由建立粒線體數目與細胞大小的關係，發現粒線體在哺乳類細胞可作為細胞生長的模板之一，且可更進一步將經過48小時Resveratrol處理再移除所培養出的細胞，視為新的對照組來發展其他的實驗觀察。

Cell growth, the driving force to cell proliferation, is the process of up-regulating macromolecular synthesis and thereby increasing biomass. In proliferating cells, the chromosome replication, the quantitative change of organelles, and all related regulating mechanisms must comply with fidelity. This is to ensure that every single copy cell is similar to the original cell. Cell containing these substances whose size control could also be affected by the inside and outside dynamical systems. To efficiently accumulate biomass, mitochondria switch the role of TCA cycle from producing energy to exporting much of the intermediates for biomass synthesis. Saccharomyces cerevisiae can use its mother cell as template during cell growth, however mammalian cells do not coordinate their growing process in the same way. We suggest that mammalian cells gradually growing to twice the size may be associated with mitochondrial metabolism. In addition, the quantitative change of mitochondria in cell growth session should not only comply with the cell replication fidelity, but also abide by the principle of once-and-only-once replication. The purpose of this study was to establish the correlation of mitochondrial numbers and cell size control by using Resveratrol as the main tool to promote mitochondrial biogenesis. The results of this study reveal that: (1)Under the treatment with Resveratrol in HeLa cells, using the fluorescent dye NAO on flow cytometry to measure the mitochondrial number, and using forward scatter-width (FSC-W) to obtain the cell size, the cell size increases as the number of mitochondria increases. (2)After treating with Resveratrol for 24 hours and then removing it, we find that the number of mitochondria and cell size can return to the same degree of those in normal cells. (3)The number of mitochondria and cell size keep on increasing after the Resveratrol removed from the 48-hour treated object. In this study, we establish the correlation between mitochondrial numbers and cell size control, and also discover mitochondria can be used as a template during the cell growth of mammalian cells. Moreover, we can use those cells whose Resveratrol influence has been removed after the 48-hour treatment as a whole new control group to develop other experiments.