Healthy and Diseased Tensile Mechanics of Mouse Lung Parenchyma

This study establishes biaxial tensile protocols for murine lung parenchyma and compares healthy tissue to COPD models—chronic agricultural dust–induced fibrosis (short- and long-term) and elastase-induced emphysema. Using planar biaxial testing, the authors quantify nonlinear elasticity, strain-energy, stiffness tangents at 15/25/35% strain, directional anisotropy (ventral–dorsal vs cranial–caudal), rate dependence (0.1, 0.5, 2.5 %/s), and preconditioning effects. Parenchyma is highly elastic and nearly isotropic after preconditioning, with minimal hysteresis beyond the first cycle. Long-term fibrosis exhibits increased maximum stress, higher 35% stiffness tangents, greater strain energy, and increased anisotropy (often stiffer in the cranial–caudal direction), whereas emphysema trends toward reduced maximum stress with preserved near-isotropy. Faster loading generally elevates stiffness and maximum stress, most prominently in fibrotic tissues—implicating collagen deposition in rate-dependent mechanics. These tissue-scale characterizations supply benchmark parameters for computational models and link disease remodeling to altered pulmonary mechanics.