Novel elasticity measurement techniques reveal that the C. elegans cuticle is required for physical integrity with age

Changes in biomechanical properties have profound impacts on human health. C. elegans might serve as a model for studying the molecular genetics of mammalian tissue decline. Previously, we found that collagens are required for insulin signaling mutants’ long lifespan and that overexpression of specific collagens extends wild-type lifespan. However, whether these effects on lifespan are due to mechanical changes during aging has not yet been established. Here, we have developed two novel methods to study the cuticle: we measure mechanical properties of live animals using osmotic shock (OS), and we directly perform the tensile test (TT) on isolated cuticles using microfluidic technology. Using these tools, we find that cuticle, not the muscle, is responsible for changes in ‘stretchiness’ of C. elegans , and that cuticle stiffness is highly non-linear and anisotropic. We also found that collagen mutations alter integrity of the cuticle by significantly altering elasticity. Additionally, aging stiffens the cuticle under mechanical loads beyond the cuticle’s healthy stretched state. Measurements of elasticity showed that long-lived daf-2 mutants were considerably better at preventing progressive mechanical changes with age. These tests of C. elegans biophysical properties suggest that the cuticle is responsible for their resilience.