A lung-on-chip model of early Mycobacterium tuberculosis infection reveals an essential role for alveolar epithelial cells in controlling bacterial growth

Abstract

We establish a murine lung-on-chip infection model and use time-lapse imaging to reveal the dynamics of host-Mycobacterium tuberculosis interactions at an air-liquid interface with a spatiotemporal resolution unattainable in animal models and to probe the direct role of pulmonary surfactant in early infection. Surfactant deficiency results in rapid and uncontrolled bacterial growth in both macrophages and alveolar epithelial cells. In contrast, under normal surfactant levels, a significant fraction of intracellular bacteria are non-growing. The surfactant-deficient phenotype is rescued by exogenous addition of surfactant replacement formulations, which have no effect on bacterial viability in the absence of host cells. Surfactant partially removes virulence-associated lipids and proteins from the bacterial cell surface. Consistent with this mechanism, the attenuation of bacteria lacking the ESX-1 secretion system is independent of surfactant levels. These findings may partly explain why smokers and elderly persons with compromised surfactant function are at increased risk of developing active tuberculosis.

Mycobacterial infection of precision cut lung slices reveals that the type 1 interferon pathway is locally induced by Mycobacterium bovis but not M. tuberculosis in different cattle breeds

“…PCLS contain type I and type II pneumocytes, endothelial cells, and bronchial cells (Fig S4 ) and also produce key molecules like surfactant which has an established role in Mtb uptake [42]. Mtb is also capable of invading type II alveolar epithelial cells [23] that play important roles in host defense [20; 21; 22]. In our study, we did not observe intraepithelial Mb, but specific labelling of bovine epithelial cells would be required to investigate interactions between bovine lung pneumocytes and Mb in more detail.…”

“…During Mtb infection, lung epithelial cells also play key roles in the host defense (reviewed in [20; 21; 22]). Type II pneumocytes are infected by Mtb [23] and produce pro-inflammatory cytokines which augment the AMP innate resistance mechanisms [24]. The role of Type II pneumocytes during Mb infection in cattle is not well known.…”

Refining Host-Pathogen Interactions: Organ-on-Chip Side of the Coin

“…Thacker et al used lung-on-chip device to create a tailored model of early M. tuberculosis infection with alveolar epithelial cells and macrophages, including channels that mimic air and blood flow as well as surfactants. By measuring the growth of intracellular bacteria with and without surfactant via time-lapse imaging, the authors were able to define a mechanism in which pulmonary surfactants led to the removal of virulence-associated lipids from M. tuberculosis cell surface, thereby attenuating bacterial intracellular growth in macrophages [ 41 ]. Furthermore, organ chips were proposed as a promising platform for mechanistic studies of host–pathogen interaction in the context of co-infection.…”

Dynamic persistence of intracellular bacterial communities of uropathogenicEscherichia coliin a human bladder-chip model of urinary tract infections

“…The channels were then rinsed with fresh coating solution and the protocol was repeated once. The channels of the bladder-chip were then washed thoroughly with PBS before incubation with an ECM solution of 150 µg/ml bovine collagen type I and 30 µg/ml fibronectin from human plasma in PBS buffered with 15 mM HEPES solution for 1-2 hours at 37°C as described previously (Thacker et al, 2020b). If not used directly, coated chips were stored at 4°C and pre-activated before use by incubation for 30 minutes with the same ECM solution at 37°C.…”

“…Organ-on-chip models have been developed for several organs either in isolation or in combination (Novak et al, 2020;Ronaldson-Bouchard and Vunjak-Novakovic, 2018). These systems are increasingly being used to model infectious diseases including viral and bacterial infections of the respiratory tract (Nawroth et al, 2020;Si et al, 2020;Thacker et al, 2020bThacker et al, , 2020a, gut (Jalili-Firoozinezhad et al, 2019;Kim et al, 2016;Shah et al, 2016;Tovaglieri et al, 2019), kidney (Wang et al, 2019), and liver (Kang et al, 2017). Recently, bladder organoids that mimic the stratified architecture of the urothelium have been used to study infections (Horsley et al, 2018;Smith et al, 2006;Sharma et al, 2020).…”