Cytoskeletal Control of Mesenchymal Stem Cell Nuclear Deformation on Nanofibrous Scaffolds

Nanofibrous scaffolds hold great potential for tissue engineering as they recapitulate the mechanical and topographic features of fibrous tissues on both the macroscopic and microscopic level [1,2]. When seeded with cells capable of fibrous extracellular matrix (ECM) production such as mesenchymal stem cells (MSCs), the new matrix is deposited in accordance with the underlying topography, and scaffolds develop improved mechanical properties with time in free swelling culture [6]. While promising, the free swelling conditions employed in evaluating in vitro construct maturation have thus far remained insufficient in achieving native-level properties. As most fibrous tissues are subjected to loading in vivo, mechanical conditioning is considered critical in directing tissue development and subsequent homeostasis with normal use. Mechanical signals are translated from the ECM to the nucleus via the cytoskeleton, with signals culminating in the control of biosynthetic activity based upon external loading conditions. Various bioreactor systems have been developed to mimic these in vivo conditions towards enhancing the maturation of engineered constructs, with most focusing on dynamic tensile deformation [3,4]. Towards gaining further insight into the means by which mechanical cues inspire alterations in cellular behavior, this study developed methods for evaluating cell and sub-cellular deformation of MSCs seeded on randomly-oriented and aligned nanofibrous scaffolds. Using a device that enables visualization of cells seeded on nanofibrous scaffolds undergoing static tensile deformation, we examined the effect of applied strain rate on cell adhesion to scaffolds, as well as changes in nuclear shape in the context of viable actin and microtubule sub-cellular networks with applied strain. These data provide new insight into fundamental mechanisms of MSC mechanoregulation on nanofibrous scaffolds, and offer constraints for long-term bioreactor studies.