The meniscus is a fibrous tissue essential to healthy knee mechanics. It functions to redirect vertical forces laterally, converting compressive into tensile loads which are taken up by an array of highly organized collagen fibers. Load transmission is not only the operative mode of the meniscus, but is also required for normal development and homeostatic maintenance [1]. With injury, disruption of the aligned collagen fiber architecture impairs function, altering joint loading and initiating osteoarthritis. Toward engineering replacement meniscus tissue, we have investigated scaffolds of aligned electrospun nanofibers that direct cell orientation and provide a suitable microenvironment for the deposition of organized extracellular matrix (ECM) (Fig 1) [2]. In previous work, human meniscus fibrochondrocytes (MFCs) seeded on such scaffolds formed robust ECM with commensurate increases in tensile properties [3]. After 10-weeks of static, free-floating culture, however, mechanical properties still fell short of native tissue values. Over this time course, full-thickness MFC colonization was not observed due to the tight packing of nanofibers, although better infiltrated constructs revealed larger improvements in tensile properties. To accelerate cell ingress, we next explored composite scaffolds containing slow eroding poly(e-caprolactone) (PCL) fibers and water-soluble poly(ethylene oxide) (PEO) fibers that augment pore size when removed (Fig 4A-D) [4]. Based on this precedent, the current study explored two strategies for improving the maturation of MFC-laden nanofibrous constructs: dynamic tensile loading mimicking the in vivo mechanical environment and inclusion of sacrificial PEO fibers to enhance cell infiltration. We hypothesized that dynamic control of the mechanical and material microenvironment would improve matrix production and lead to enhanced mechanical properties.

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