Newberry Mitchell G, Ennis Daniel B, Savage Van M
Department of Biomathematics, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, United States of America.
Department of Radiological Sciences, Biomedical Physics, and Bioengineering, University of California, Los Angeles, Los Angeles, California, United States of America.
PLoS Comput Biol. 2015 Aug 28;11(8):e1004455. doi: 10.1371/journal.pcbi.1004455. eCollection 2015 Aug.
Scientists have long sought to understand how vascular networks supply blood and oxygen to cells throughout the body. Recent work focuses on principles that constrain how vessel size changes through branching generations from the aorta to capillaries and uses scaling exponents to quantify these changes. Prominent scaling theories predict that combinations of these exponents explain how metabolic, growth, and other biological rates vary with body size. Nevertheless, direct measurements of individual vessel segments have been limited because existing techniques for measuring vasculature are invasive, time consuming, and technically difficult. We developed software that extracts the length, radius, and connectivity of in vivo vessels from contrast-enhanced 3D Magnetic Resonance Angiography. Using data from 20 human subjects, we calculated scaling exponents by four methods-two derived from local properties of branching junctions and two from whole-network properties. Although these methods are often used interchangeably in the literature, we do not find general agreement between these methods, particularly for vessel lengths. Measurements for length of vessels also diverge from theoretical values, but those for radius show stronger agreement. Our results demonstrate that vascular network models cannot ignore certain complexities of real vascular systems and indicate the need to discover new principles regarding vessel lengths.
长期以来，科学家们一直试图了解血管网络如何为全身的细胞供应血液和氧气。最近的研究工作聚焦于一些原则，这些原则限制了血管从主动脉到毛细血管分支过程中血管大小的变化，并使用标度指数来量化这些变化。著名的标度理论预测，这些指数的组合可以解释代谢、生长和其他生物速率如何随身体大小而变化。然而，由于现有的测量血管系统的技术具有侵入性、耗时且技术难度大，对单个血管段的直接测量一直受到限制。我们开发了一种软件，可从对比增强的三维磁共振血管造影中提取体内血管的长度、半径和连通性。利用来自20名人类受试者的数据，我们通过四种方法计算标度指数——两种方法源自分支点的局部特性，另外两种方法源自全网络特性。尽管这些方法在文献中经常互换使用，但我们发现这些方法之间并没有普遍的一致性，特别是在血管长度方面。血管长度的测量值也与理论值不同，但半径的测量值显示出更强的一致性。我们的结果表明，血管网络模型不能忽视真实血管系统的某些复杂性，并表明需要发现有关血管长度的新原则。
