Institute for Molecular Bioscience, The University of Queensland, St. Lucia, Brisbane, QLD 4072, Australia.
J Theor Biol. 2013 Dec 7;338:66-79. doi: 10.1016/j.jtbi.2013.08.033. Epub 2013 Sep 7.
The growth of organs results from proliferation within distinct cellular compartments. Organ development also involves transitions between cell types and variations in cell cycle duration as development progresses, and is regulated by a balance between entry into the compartment, proliferation of cells within the compartment, acquisition of quiescence and exit from that cell state via differentiation or death. While it is important to understand how environmental or genetic alterations can perturb such development, most approaches employed to date are descriptive rather than quantitative. This is because the identification and quantification of such parameters, while tractable in vitro, is challenging in the context of a complex tissue in vivo. Here we present a new framework for determining cell turnover in developing organs in vivo that combines cumulative cell-labelling and quantification of distinct cell-cycle phases without assuming homogeneity of behaviour within that compartment. A mathematical model is given that allows the calculation of cell cycle length in the context of a specific biological example and assesses the uncertainty of this calculation due to incomplete knowledge of cell cycle dynamics. This includes the development of a two population model to quantify possible heterogeneity of cell cycle length within a compartment and estimate the aggregate proliferation rate. These models are demonstrated on data collected from a progenitor cell compartment within the developing mouse kidney, the cap mesenchyme. This tissue was labelled by cumulative infusion, volumetrically quantified across time, and temporally analysed for the proportion of cells undergoing proliferation. By combining the cell cycle length predicted by the model with measurements of total cell population and mitotic rate, this approach facilitates the quantification of exit from this compartment without the need for a direct marker of that event. As a method specifically designed with assumptions appropriate to developing organs we believe this approach will be applicable to a range of developmental systems, facilitating estimations of cell cycle length and compartment behaviour that extend beyond simple comparisons of mitotic rates between normal and perturbed states.
器官的生长是由特定细胞区室中的增殖引起的。器官发育还涉及细胞类型之间的转变以及随着发育的进行细胞周期持续时间的变化，并且由进入区室的平衡、区室内细胞的增殖、静止的获得以及通过分化或死亡退出该细胞状态来调节。虽然了解环境或遗传改变如何扰乱这种发育很重要，但迄今为止采用的大多数方法都是描述性的，而不是定量的。这是因为虽然在体外可以识别和量化这些参数，但在体内复杂组织的背景下，这是具有挑战性的。在这里，我们提出了一种新的框架，用于确定体内发育器官中的细胞更替，该框架结合了累积细胞标记和对不同细胞周期阶段的定量，而无需假设该区室内行为具有同质性。给出了一个数学模型，该模型允许在特定生物学示例的背景下计算细胞周期长度，并评估由于对细胞周期动力学的不完全了解而导致该计算的不确定性。这包括开发一个两群体模型来量化一个区室内细胞周期长度的可能异质性，并估计总增殖率。这些模型在从小鼠肾脏发育过程中的祖细胞区室（帽间充质）收集的数据上进行了演示。该组织通过累积输注进行标记，随时间进行体积量化，并对进行增殖的细胞比例进行时间分析。通过将模型预测的细胞周期长度与总细胞群体和有丝分裂率的测量值相结合，这种方法无需直接标记该事件即可促进该区室的退出的量化。作为一种专门针对发育器官设计的方法，我们相信这种方法将适用于一系列发育系统，从而促进细胞周期长度和区室行为的估计，这些估计超出了正常和扰动状态之间有丝分裂率的简单比较。
