Department of Pathology and Laboratory Medicine, David Geffen School of Medicine at the University of California at Los Angeles, USA.
Biophys J. 2013 Aug 6;105(3):593-601. doi: 10.1016/j.bpj.2013.06.041.
Somatic cell reprogramming to pluripotency requires an immediate increase in cell proliferation and reduction in cell size. It is unknown whether proliferation and biomass controls are similarly coordinated with early events during the differentiation of pluripotent stem cells (PSCs). This impasse exists because PSCs grow in tight clusters or colonies, precluding most quantifying approaches. Here, we investigate live cell interferometry as an approach to quantify the biomass and growth of HSF1 human PSC colonies before and during retinoic acid-induced differentiation. We also provide an approach for measuring the rate and coordination of intracolony mass redistribution in HSF1 clusters using live cell interferometry images. We show that HSF1 cells grow at a consistent, exponential rate regardless of colony size and display coordinated intracolony movement that ceases with the onset of differentiation. By contrast, growth and proliferation rates show a decrease of only ∼15% decrease during early differentiation despite global changes in gene expression and previously reported changes in energy metabolism. Overall, these results suggest that cell biomass and proliferation are regulated independent of pluripotency during early differentiation, which is distinct from what occurs with successful reprogramming.
体细胞重编程为多能性需要细胞增殖的立即增加和细胞大小的减少。目前尚不清楚增殖和生物量控制是否与多能干细胞（PSCs）分化过程中的早期事件同样协调。之所以存在这种僵局，是因为 PSCs 生长在紧密的簇或菌落中，排除了大多数定量方法。在这里，我们研究活细胞干涉测量法，以定量测量 HSF1 人 PSC 菌落在视黄酸诱导分化前后的生物量和生长。我们还提供了一种使用活细胞干涉测量图像测量 HSF1 簇内质量重新分布的速率和协调性的方法。我们发现，HSF1 细胞无论菌落大小如何，均以一致的指数速率生长，并显示出协调的菌落内运动，这种运动在分化开始时停止。相比之下，尽管基因表达发生了全局变化，并且之前报道了能量代谢的变化，但在早期分化过程中，生长和增殖速率仅下降了约 15%。总的来说，这些结果表明，在早期分化过程中，细胞生物量和增殖是独立于多能性调节的，这与成功重编程时的情况不同。
