Spatiotemporal quantification of cell dynamics in the lung following influenza virus infection

Lu Yin,Hanry Yu,Shuoyu Xu,Jianzhu Chen,Gino V Limmon,Jagath C Rajapakse,Dahai Zheng,Jierong Cheng,Nicola H N Leung,Vincent T K Chow

doi:10.1117/1.jbo.18.4.046001

Abstract

Lung injury caused by influenza virus infection is widespread. Understanding lung damage and repair progression post infection requires quantitative spatiotemporal information on various cell types mapping into the tissue structure. Based on high content images acquired from an automatic slide scanner, we have developed algorithms to quantify cell infiltration in the lung, loss and recovery of Clara cells in the damaged bronchioles and alveolar type II cells (AT2s) in the damaged alveolar areas, and induction of pro-surfactant protein C (pro-SPC)-expressing bronchiolar epithelial cells (SBECs). These quantitative analyses reveal: prolonged immune cell infiltration into the lung that persisted long after the influenza virus was cleared and paralleled with Clara cell recovery; more rapid loss and recovery of Clara cells as compared to AT2s; and two stages of SBECs from Scgb1a1⁺ to Scgb1a1⁻. These results provide evidence supporting a new mechanism of alveolar repair where Clara cells give rise to AT2s through the SBEC intermediates and shed light on the understanding of the lung damage and repair process. The approach and algorithms in quantifying cell-level changes in the tissue context (cell-based tissue informatics) to gain mechanistic insights into the damage and repair process can be expanded and adapted in studying other disease models.

Highlights

The pulmonary airway successively branches from trachea to bronchi; the bronchi continue to divide within the lung to bronchioles and to alveoli
Based on high content images acquired from an automatic slide scanner, we have developed algorithms to quantify cell infiltration in the lung, loss and recovery of Clara cells in the damaged bronchioles and alveolar type II cells (AT2s) in the damaged alveolar areas, and induction of pro-surfactant protein C-expressing bronchiolar epithelial cells (SBECs)
We have developed automated algorithms, using high content images obtained from the automatic slide scanner, to quantify cellular dynamics in lung damage and repair following the influenza virus infection to gain mechanistic insights into the lung damage and repair process

Summary

Introduction

The pulmonary airway successively branches from trachea to bronchi; the bronchi continue to divide within the lung to bronchioles and to alveoli. Bronchioles are covered with Clara cells whereas alveoli are covered with alveolar type I cells (AT1s) interspersed with alveolar type II cells (AT2s). The lung is constantly exposed to environmental assaults, such as chemicals and infectious agents, leading to significant tissue damages. Studies with bleomycin- and naphthalene-induced lung injury have shown that Clara cells, which express secretoglobin family 1A member 1 [Scgb1a1 or Clara cell secretory protein (CCSP)], can repair damaged bronchiolar epithelium by selfrenewal and give rise to bronchiolar ciliated cells.[1,2,3] AT2s, which express pro-surfactant protein C (pro-SPC), can selfrenew as well as differentiate into AT1s in response to alveolar. Based on the sickness scores of inflammation, edema, or fibrosis, a semi-quantitative grading system has been used to classify different levels of lung damage.[7,8,9,10,11,12,13,14] The average size of the alveolar sac has been used to quantify hyperoxia-induced lung injury, where alveolar

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