Nuclear connectivity in mesenchymal stem cell differentiation and its role in mechanotransduction

Mechanical forces transmitted through the cellular microenvironment are critically important for tissue development, homeostasis, and degeneration, particularly for tissues in the musculoskeletal system that play primary load bearing roles. When these tissues degenerate, their limited healing capacity has lead many to propose tissue engineering strategies in order to provide functional replacements. While native tissue structural and mechanical benchmarks are commonly used to quantify and validate outcomes for tissue engineering and to refine experimental approaches, these same benchmarks have not yet been extended to the cellular and sub-cellular level. This is true despite the fact that it is at this length scale where tissue specific mechanotransduction occurs. With this motivation, and building on an established biomaterial framework for engineering fibrocartilagenous tissues, this thesis further refines macro-scale functional benchmarks and defines new micro-scale benchmarks that are operative at the cellular and sub-cellular level. In doing so, we identify a number of structural attributes of the cellular cytoskeleton and its attachments to the nucleus that are important for mechanotransduction. In normal functioning tissues, maintenance of phenotype in mechanically active microenvironments requires appropriately tuned mechanotransduction machinery. Understanding how these sub-cellular mechanoactive species (including the cytoskeleton, the nucleus, and nuclear connectivity) change with differentiation and development, as well as their role in mechanical signaling, will be of primary importance for the success of tissue engineering strategies.