An emerging non-pharmacological treatment for bone degenerative diseases is whole body vibration (WBV), a mechanical signal composed of low-magnitude, high-frequency (LMHF) vibrations that when applied to bone, have osteogenic and anti-resorptive effects. Currently, the cellular and molecular mechanism underlying the effect of WBV on bone is unclear. In this study, we investigated the response of osteocytes, the putative mechanosensor in bone, under LMHF vibration. As bone cells differentiate from mesenchymal stromal cells (MSCs), we also studied the osteogenic differentiation of rat MSCs in the presence of vibration loading. We found that vibrated osteocytes show gene and protein expression changes suggestive of an anti-osteoclastogenic response, and secrete soluble factors that inhibit osteoclast formation and activity. In contrast, rat MSCs showed moderate to no response to LMHF vibration during osteogenic differentiation. Our data suggest that in vivo effects of LMHF vibration are mediated through mechanosensing and biochemical responses by osteocytes.

An emerging non-pharmacological treatment for bone degenerative diseases is whole body vibration (WBV), a mechanical signal composed of low-magnitude, high-frequency (LMHF) vibrations that when applied to bone, have osteogenic and anti-resorptive effects. Currently, the cellular and molecular mechanism underlying the effect of WBV on bone is unclear. In this study, we investigated the response of osteocytes, the putative mechanosensor in bone, under LMHF vibration. As bone cells differentiate from mesenchymal stromal cells (MSCs), we also studied the osteogenic differentiation of rat MSCs in the presence of vibration loading. We found that vibrated osteocytes show gene and protein expression changes suggestive of an anti-osteoclastogenic response, and secrete soluble factors that inhibit osteoclast formation and activity. In contrast, rat MSCs showed moderate to no response to LMHF vibration during osteogenic differentiation. Our data suggest that in vivo effects of LMHF vibration are mediated through mechanosensing and biochemical responses by osteocytes.

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A promising structural health monitoring (SHM) method for implementation on real world structures is impedance-based health monitoring. An in-service system is envisioned to include on board processing and perhaps wireless transfer of data. Ideally, a system could be produced as a slap-on or automatically installed addition to a structure. The research presented in this dissertation addresses issues that will help make such a system a reality. Although impedance-based SHM does not typically use an analytical model for basic damage identification, a model is necessary for more advanced features of SHM, such as damage prognosis, and to evaluate system parameters when installing on various structures. A model was developed based on circuit analysis of the previously proposed low-cost circuit for impedance-based SHM in combination with spectral elements. When a three-layer spectral element representing a piezoceramic bonded to a base beam is used, the model can predict the large peaks in the impedance response due to resonances of the bonded active sensor. Parallel and series connections of distributed sensor systems are investigated both experimentally and with the developed model. Additionally, the distribution of baseline damage metrics is determined to assess how the large quantities of data produced by a monitoring system can be handled statistically. A modification of the RMSD damage metric has also been proposed that is essentially the squared sum of the Z-statistic for each frequency point. Preferred excitation frequencies for macro-fiber composite (MFC) active sensors are statistically determined for a long composite boom under development for use in rigidizable inflatable space structures. / Ph. D.