C20-05 In Vivo and Ex Vivo Lobar Ventilation Model for Probing the Role of Lung Mechanics in Metastasis

Rationale The lung is a common target of cancer metastasis. Although cancer and immune cells are exposed to mechanical stimuli during a breathing cycle, the role of these forces in lung metastasis remains unclear. In vitro systems allow the precise control of mechanical stimuli, but they lack key physiological features such as lung immunity and complex vascular-alveolar architecture. In vivo models are beneficial for investigating tumor-immune crosstalk. However, selective modulation of lung mechanics at the lobe level in vivo is challenging, yet it is essential for establishing internal controls where biological and biochemical factors are shared. Here, we developed an in vivo and an ex vivo lobar breathing-ventilation models, with unique capabilities in selectively regulating breathing mechanics in target lung lobes of mice (Figure 1A and 1B). Methods Custom-designed plugs were fabricated using a high-resolution 3D printer (BMF S240) followed by coating with hydrogel for biocompatibility and sealing purposes. For the in vivo lobar breathing model, a plug was inserted into the bronchus of the target lobe for localized airflow suppression (Figure 1A and 1C). The airflow restriction can be controlled by the geometry of the air channel (Figure 1D). For ex vivo lobar ventilation, plugs were inserted into the bronchi of the left and right lobes, connected to two separate ventilators. The lung was encapsulated in the ex vivo crystal ribcage setup for high-resolution real-time imaging (Figure 1B). Green fluorescent protein (GFP)-labeled YUMMER1.7 melanoma cells were injected intravenously into a C57BL/6 wild-type mouse, and lungs were harvested after one hour. The lung vasculature was labeled with Evans blue. The fluorescent images were obtained using an X1 spinning confocal microscope. Results The alveoli in the lobe with the plug were barely expanded by the increased air pressure, in contrast to the unplugged lobes (Figure 1E). The ex vivo lobar ventilation system enables independent control of ventilation in each lobe (Figure 1F). We further found that a greater number of cancer cells were trapped within the microvasculature of the lobe under higher tidal volume at 1 hr after injection (Figure 1G and 1H). Conclusionand Future Work We developed two complementary in vivo and ex vivo lobar breathing and ventilation platforms that enable the lobe-scale control of lung mechanics. We found that breathing mechanics can influence cancer cell trapping in capillaries. We will further explore the role of mechanical stimuli in later metastatic processes, including extravasation, proliferation, and tumor-immune interactions.