From whole-organ imaging to in-silico blood flow modeling: A new multi-scale network analysis for revisiting tissue functional anatomy

We present a multi-disciplinary image-based blood flow perfusion modeling of a whole organ vascular network for analyzing both its structural and functional properties. We show how the use of Light-Sheet Fluorescence Microscopy (LSFM) permits whole-organ micro-vascular imaging, analysis and modelling. By using adapted image post-treatment workflow, we could segment, vectorize and reconstruct the entire micro-vascular network composed of 1.7 million vessels, from the tissue-scale, inside a ∼ 25 × 5 × 1 = 125mm3 volume of the mouse fat pad, hundreds of times larger than previous studies, down to the cellular scale at micron resolution, with the entire blood perfusion modeled. Adapted network analysis revealed the structural and functional organization of meso-scale tissue as strongly connected communities of vessels. These communities share a distinct heterogeneous core region and a more homogeneous peripheral region, consistently with known biological functions of fat tissue. Graph clustering analysis also revealed two distinct robust meso-scale typical sizes (from 10 to several hundred times the cellular size), revealing, for the first time, strongly connected functional vascular communities. These community networks support heterogeneous micro-environments. This work provides the proof of concept that in-silico all-tissue perfusion modeling can reveal new structural and functional exchanges between micro-regions in tissues, found from community clusters in the vascular graph.

本研究提出了一种基于多学科成像的全器官血管网络血流灌注建模方法，用于分析其结构与功能特性。本研究展示了光片荧光显微镜（Light-Sheet Fluorescence Microscopy, LSFM）如何实现全器官微血管的成像、分析与建模。通过优化后的图像处理工作流，我们可在小鼠脂肪垫约25×5×1=125mm³的组织体积（该体积较以往研究大数百倍）中，从组织尺度直至微米级分辨率的细胞尺度，完成由170万个血管组成的完整微血管网络的分割、矢量化与重建，并实现全血灌注建模。经优化的网络分析显示，中尺度组织的结构与功能组织表现为高度连通的血管群落。这些血管群落具有特征性的异质性核心区域与更趋均一的外周区域，这与脂肪组织已知的生物学功能相符。图形聚类分析还揭示了两种截然不同且稳定的中尺度典型尺寸（为细胞尺寸的10至数百倍），首次发现了高度连通的功能性血管群落。这类群落网络支撑着异质性的微环境。本研究完成了概念验证：通过计算机模拟（in silico）的全组织灌注建模，可揭示组织内微区域间此前未被发现的结构与功能交流，这类交流可通过血管图的群落聚类得以发现。