Department of Cell Biology, University of Connecticut Health Center, Farmington, CT, 06030, USA.
Laboratory for Systems Medicine, University of Florida Health, Gainesville, FL, 32610, USA.
Sci Rep. 2020 Nov 23;10(1):20334. doi: 10.1038/s41598-020-77211-x.
The capillary network of the kidney glomerulus filters small molecules from the blood. The glomerular 3D structure should help to understand its function, but it is poorly characterized. We therefore devised a new approach in which an automated tape collecting microtome (ATUM) was used to collect 0.5 μm thick serial sections from fixed mouse kidneys. The sections were imaged by scanning electron microscopy at ~ 50 nm/pixel resolution. With this approach, 12 glomeruli were reconstructed at an x-y-z resolution ~ 10 × higher than that of paraffin sections. We found a previously undescribed no-cross zone between afferent and efferent branches on the vascular pole side; connections here would allow blood to exit without being adequately filtered. The capillary diameters throughout the glomerulus appeared to correspond with the amount of blood flow within them. The shortest path (minimum number of branches to travel from afferent to efferent arterioles) is relatively independent of glomerular size and is present primarily on the vascular pole size. This suggests that new branches and longer paths form on the urinary pole side. Network analysis indicates that the glomerular network does not form by repetitive longitudinal splitting of capillaries. Thus the 3D structure of the glomerular capillary network provides useful information with which to understand glomerular function. Other tissue structures in the body may benefit from this new three dimensional approach.
肾小球的毛细血管网络从血液中滤除小分子。肾小球的 3D 结构有助于理解其功能，但它的特征描述很差。因此，我们设计了一种新的方法，使用自动带收集切片机（ATUM）从固定的小鼠肾脏中收集 0.5μm 厚的连续切片。这些切片通过扫描电子显微镜以50nm/像素的分辨率进行成像。通过这种方法，在 x-y-z 分辨率上重建了 12 个肾小球，分辨率比石蜡切片高10 倍。我们在血管极侧发现了一个以前未描述的输入和输出分支之间的无交叉区；这里的连接允许血液在没有被充分过滤的情况下排出。整个肾小球的毛细血管直径似乎与其中的血流量相对应。最短路径（从输入小动脉到输出小动脉的分支数量最少）相对独立于肾小球大小，主要存在于血管极侧。这表明新的分支和更长的路径在尿极侧形成。网络分析表明，肾小球网络不是通过毛细血管的重复纵向分裂形成的。因此，肾小球毛细血管网络的 3D 结构为理解肾小球功能提供了有用的信息。身体的其他组织结构可能也会受益于这种新的三维方法。
