| Craniofacial abnormalities such as cleft palate or craniosynostosis as well as other bone defects are a significant clinical problem. Patients undergo extensive surgical intervention often requiring bone grafts. Currently the ideal source for donor material for craniofacial reconstruction is autogenous bone from the iliac crest, the rib, or split calvarial grafts. A suitable alternative would mitigate the associated risks of autologous grafts, including risks to donor site integrity and increases in blood loss, operative time, and cost. The local delivery of multipotent cells to a defect site where they could form the foundation of newly regenerating tissue may constitute a viable alternative to autogenous bone and the problems associated with donor site morbidity. Adipose-derived stromal cells (ASCs) constitute a promising source of cells for bone tissue engineering. However, multipotent cells often require conditioning before they can attain fully functional osteogenic phenotypes. Typically, this conditioning has come in the form of mechanical or chemical stimuli. The purpose of this dissertation is to explore the capacity of an alternative conditioning mechanism, a noninvasive method, such as an electric field, to affect lineage commitment in ASCs.;Endogenous electric fields exert strong organizational cues during embryogenesis, regeneration, and wound repair. The vital role of stem cells in such environments suggests that they may have a specialized capacity to detect and respond to electric fields. The work here shows that murine adipose-derived stromal cells (mASCs) do respond to electric fields by migrating toward the cathode in direct current fields of physiologic strength and show dose dependence in migration rate to stronger fields. Additionally, the galvanotaxis appears to share classic chemotactic intracellular signaling pathways inherent to other migrating cell types. Human adipose-derived stromal cells (hASCs), on the other hand, show only a limited capacity to migrate in response to electric fields, but do show evidence of cytoskeletal reorganization in response to both low frequency AC and DC electric fields. Adult stem cell concentration and organization may be directed by exploiting galvanotaxis in response to externally applied electric fields. The galvanotactic response can be extrapolated to motility of cells in general, and understanding the motility of graft cells is of critical importance to designing therapies that retain cells in the proximity of the defect site.;In addition to their migratory response, mASCs demonstrated an upregulation of early osteoblast specific markers over time, accompanied by a decrease in adipogenesis. Molecular mechanisms for transducing the electric signal into cell fate commitments are relatively unknown. However, the electric field could be transduced by mASCs into cytoskeletal changes via growth factor receptor signaling that results in increased cytoskeletal stress. That increased stress state may be responsible for the observed osteogenic effects. Understanding the influence of a novel regulator of biology such as an electric field on ASCs contributes additional methods for engineering cellular responses to the field of regenerative medicine. Electric fields show preliminary promise as candidate enhancers of osteogenesis of ASCs and may be incorporated into cell-based strategies for skeletal regeneration. |
