Dynamic Tensile Loading Improves the Mechanical Properties of MSC-Laden Aligned Nanofibrous Scaffolds

Fibrocartilaginous tissues such as the meniscus and annulus fibrosus serve critical load-bearing roles, relying on arrays of highly organized collagen fibers to resist tensile loads experienced with normal physiologic activities [1]. As these specialized structures are often injured, there exists great demand for engineered tissues for repair or replacement. Towards recreating the structural and mechanical features of these anisotropic tissues in vitro, we fabricate scaffolds composed of co-aligned, ultra-fine biodegradable polymer fibers. These 3D micro-patterns direct mesenchymal stem cell (MSC) orientation and the subsequent formation of organized extracellular matrix (ECM) [2]. As this cell-produced matrix continually develops with time in culture, the mechanical properties of the construct gradually increase. In previous studies aimed at engineering human meniscus tissue, constructs achieved moduli of ∼40MPa after 10 weeks of culture, representing a two-fold increase in the starting properties of the scaffold [3]. Despite this demonstrable increase, this value remains well below that of the native tissue. As mechanical forces are essential to the maintenance of musculoskeletal tissues, this work examined the effect of cyclic tensile loading on MSC-laden nanofibrous constructs to enhance their in vitro maturation. We hypothesized that this loading modality would modulate the transcriptional behavior of seeded MSCs, spur the deposition of collagen-rich matrix, and lead to additional improvements in construct mechanical properties.