Tata Institute of Fundamental Research Hyderabad (TIFR-H), Hyderabad, India.
Centre for BioSystems Science and Engineering, Indian Institute of Science, Bengaluru, India.
Biophys J. 2023 Oct 3;122(19):3909-3923. doi: 10.1016/j.bpj.2023.08.014. Epub 2023 Aug 19.
In the epithelium, cell density and cell proliferation are closely connected to each other through contact inhibition of proliferation (CIP). Depending on cell density, CIP proceeds through three distinct stages: the free-growing stage at low density, the pre-epithelial transition stage at medium density, and the post-epithelial transition stage at high density. Previous studies have elucidated how cell morphology, motion, and mechanics vary in these stages. However, it remains unknown whether cellular metabolism also has a density-dependent behavior. By measuring the mitochondrial membrane potential at different cell densities, here we reveal a heterogeneous landscape of metabolism in the epithelium, which appears qualitatively distinct in three stages of CIP and did not follow the trend of other CIP-associated parameters, which increases or decreases monotonically with increasing cell density. Importantly, epithelial cells established a collective metabolic heterogeneity exclusively in the pre-epithelial transition stage, where the multicellular clusters of high- and low-potential cells emerged. However, in the post-epithelial transition stage, the metabolic potential field became relatively homogeneous. Next, to study the underlying dynamics, we constructed a system biology model, which predicted the role of cell proliferation in metabolic potential toward establishing collective heterogeneity. Further experiments indeed revealed that the metabolic pattern spatially correlated with the proliferation capacity of cells, as measured by the nuclear localization of a pro-proliferation protein, YAP. Finally, experiments perturbing the actomyosin contractility revealed that, while metabolic heterogeneity was maintained in the absence of actomyosin contractility, its ab initio emergence depended on the latter. Taken together, our results revealed a density-dependent collective heterogeneity in the metabolic field of a pre-epithelial transition-stage epithelial monolayer, which may have significant implications for epithelial form and function.
在上皮组织中，细胞密度和细胞增殖通过增殖抑制的接触（CIP）紧密相连。根据细胞密度的不同，CIP 可以通过三个不同的阶段进行：低密度时的自由生长阶段、中密度时的上皮前过渡阶段和高密度时的上皮后过渡阶段。以前的研究已经阐明了这些阶段中细胞形态、运动和力学如何变化。然而，细胞代谢是否也具有密度依赖性行为仍不清楚。通过测量不同细胞密度下的线粒体膜电位，我们在这里揭示了上皮组织中代谢的异质性景观，这种景观在 CIP 的三个阶段表现出明显的不同，并且没有遵循其他与 CIP 相关的参数的趋势，这些参数随着细胞密度的增加而单调增加或减少。重要的是，上皮细胞仅在上皮前过渡阶段建立了集体代谢异质性，在该阶段出现了高电位和低电位细胞的多细胞簇。然而，在后上皮过渡阶段，代谢势场变得相对均匀。接下来，为了研究潜在的动力学，我们构建了一个系统生物学模型，该模型预测了细胞增殖在建立集体异质性方面对代谢潜力的作用。进一步的实验确实表明，代谢模式与细胞增殖能力在空间上相关，这可以通过核定位的促增殖蛋白 YAP 来测量。最后，实验扰动肌动球蛋白收缩性表明，虽然在缺乏肌动球蛋白收缩性的情况下可以维持代谢异质性，但它的初始出现取决于后者。总之，我们的结果揭示了上皮前过渡阶段上皮单层中代谢场的密度依赖性集体异质性，这可能对上皮形态和功能具有重要意义。
