Micro-Scale Strain Transfer in Fiber-Reinforced Native Tissue Is Distinct From Cell-Seeded Aligned Nanofibrous Scaffolds

Mechanical signals influence cell viability, differentiation, proliferation, and extracellular matrix (ECM) production in load-bearing tissues. However, the current understanding of how macroscopic tissue level strain is transferred to cells is confounded by the highly variable strain fields that arise within the ECM of these tissues. In tendon and outer annulus fibrosus (AF), microscale strains in the ECM can be significantly lower than the applied strains.1,2,3 In meniscus, both strain amplification and attenuation were observed at the microscale level.4

Biaxial Mechanical Testing of Single Annulus Fibrosus Layers

The intervertebral disc (IVD), consisting of the inner nucleus pulposus and the outer annulus fibrosus, is subjected to multiaxial stress in vivo. The disc undergoes degenerative changes that account for impairment and disability in middle-aged and older individuals.4 In addition to age-related degeneration, the intervertebral disc is subject to the development of lesions due to partial displacement or rupture of the annulus fibrosus. Such occurrences, typically resulting from physical trauma, can yield disabling effects from impingement on spinal nerve structures. A greater understanding of the IVD and how it functions mechanically is crucial in prevention and repair of debilitating spinal disorders.