Morphological Characterization of Acinar Cluster in Mouse Lung Using a Multiscale‐based Segmentation Algorithm on Synchrotron Micro‐CT Images

Abstract

Understanding the three-dimensional morphology of pulmonary acini is essential when exploring the biomechanics of respiratory function. In this study, we characterized the morphology of individual acini and a cluster of acini stemming from the same terminal conducting airway using a quantitative approach based on the semi-automatic segmentation of synchrotron micro-CT images of mouse lung. The volume and surface area of five clusters of mouse acini including 50 individual acini were estimated based on the voxel and surface mesh of segmented acini at FRC. The pathway length and width were estimated for one cluster including 15 acini based on the skeleton of segmented acini. The acinar volume was 0.09 ± 0.07 mm(3) (mean ± SD), and the surface area was 6.82 ± 4.49 mm(2) , in agreement with previous studies. The volume of the acinar clusters was 0.89 ± 0.34 mm(3) , and the surface area was 68.18 ± 17.66 mm(2) . The largest volume acinus per cluster was found in the distal region of the terminal conducting airway, and apparent respiratory bronchioles were observed only in large-volume acini. The generation number of pathways per acinus was 8 ± 2 (range: 6-12). The pathway length at lower generations (generations 2-6) increased with the generation number in a single cluster, while did not significantly change at lower generations in some acinar groups. The pathway width increased with increasing generation numbers. Our approach characterized the quantitative morphology of pulmonary acinar clusters in mouse lung, and the results can be used in further biomechanical simulation studies. Anat Rec, 299:1424-1434, 2016. © 2016 Wiley Periodicals, Inc.

How high resolution 3-dimensional imaging changes our understanding of postnatal lung development

“…To achieve the required resolution high-resolution bench-top µCT or synchrotron radiation based X-ray tomographic microscopy (SRXTM) was applied. A spatial resolution of 2 µm or less allows not only a detailed recognition and characterization of the conducting airways (Lee et al 2008), but also a (semi)automated segmentation of acini, followed by their morphological and/or stereological characterization (Vasilescu et al 2012; Kumar et al 2013; Haberthur et al 2013; Xiao et al 2013, 2016; Kizhakke Puliyakote et al 2016a). Comparing µCT and SRXTM, SRXTM possesses the advantage of being operated with a ~ 1 billion times brighter and nearly parallel beam instead of the cone beam of the µCT.…”

“…In addition, ventilation and perfusion distributions, as well as ventilation induced lung injury present another field of the application of SRXTM (Bayat et al 2001, 2013; Ito et al 2013; Broche et al 2017). The characterization of the size, number, surface area, and skeleton of the acini in adults and during development should also be named (Haberthur et al 2010; Lovric et al 2013, 2017a, b; Kizhakke Puliyakote et al 2016a, b; Scott et al 2015; Vasilescu et al 2013; Xiao et al 2016). At last but not at least SRXTM is also used to characterize the alveolar microvasculatur during development, repair, and disease (Ackermann et al 2014; Schittny et al 2008).…”

Control Interventions Can Impact Alveolarization and the Transcriptome in Developing Mouse Lungs

“…Studies on alveolarization generally rely on the identification and validation of pathways that direct lung development, using pharmacological and genetic approaches. Small‐molecule and proteinaceous modulators of developmental pathways have been administered via the enteral or parenteral routes, and subsequently, the impact on the development of the lung structure might be assessed microscopically (Valenzuela et al, ) or radiologically (Xiao et al, ); alongside screens for transcriptomic changes (Mariani, ), by microarray, or more recently, RNA‐Seq (Bhattacharya et al, ; Lingappan et al, ) technology. Small‐molecule interventions have, in the past, relied on enzyme inhibitors to block enzyme function (Reviewed in Madurga et al, ; Silva et al, ; Surate Solaligue et al, ); but have recently been expanded to include chemical chaperones (Nguyen and Uhal, ; Siddesha et al, ) and genetic interference, through sequence‐specific modulation of microRNA function using antagomiRs (Nardiello and Morty, ) or microRNA mimics (Olave et al, ; Durrani‐Kolarik et al, ).…”

Three-Dimensional Whole-Organ Characterization of the Regional Alveolar Morphology in Normal Murine Lungs

“…These values are smaller than the ones found in this study for all groups ( Table 1 ) but coincide in the order of magnitude. Similarly, Xiao et al (2016) studied the acini of A/J mouse in situ using synchrotron-based micro-CT. They found surface-to-volume ratio values of 79.8 ± 8.9 mm –1 , which are very close to those reported in this work in Table 1 .…”