Pan-Tissue Scaling of Stiffness Versus Fibrillar Collagen Reflects Contractility-Driven Strain That Inhibits Fibril Degradation

The study investigates the relationship between tissue stiffness and Collagen-I levels across various animal tissues, revealing a sub-linear scaling pattern. Using second harmonic generation imaging and mass spectrometry, the research shows that tissue stiffness correlates with Collagen-I levels, similar to cellularized Collagen-I gels but not acellular ones. The study highlights that cellular myosin-II contraction and matrix metalloproteinase inhibitors indicate collagenase activity is suppressed by strain rather than stress. This suppression is observed in tissues like embryonic hearts and tendons, which differ significantly in collagen levels and stiffness. The findings suggest that tissue stiffness scaling is influenced by contractility, providing insights into organ size scaling, microgravity effects, and potential therapeutic approaches.