In Vitro Investigation of Lung Connective Tissue Stiffness Under Various Oxygen Tensions and Gradients

This study introduces a three-dimensional (3D) in vitro model to examine the impact of oxygen microenvironments on lung tissue stiffness. The microfluidic platform creates oxygen gradients via a spatially confined chemical reaction channel, enabling non-invasive stiffness measurements with biological atomic force microscopy (Bio-AFM). Experimental results indicate that low oxygen levels (1% [O<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>]) significantly increase hydrogel stiffness compared to normoxia (21% [O<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>]). Under oxygen gradients, stiffness decreases by approximately 45% compared to the uniform hypoxia condition, and the cell-matrix stiffness gradually declines as oxygen tension decreases. This model provides valuable insights into the link between oxygen microenvironments and lung fibrosis progression, utilizing a simple microfluidic approach for stiffness studies.