Browsing by Author "Sampson, Alana Cherrell"

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    Influence of Heating and Cyclic Tension on the Induction of Heat Shock Proteins and Bone-Related Proteins by MC3T3-E1 Cells
    Chung, Eunna; Sampson, Alana Cherrell; Rylander, M. Nichole (Hindawi, 2014-06-11)
    Stress conditioning (e.g., thermal, shear, and tensile stress) of bone cells has been shown to enhance healing. However, prior studies have not investigated whether combined stress could synergistically promote bone regeneration. This study explored the impact of combined thermal and tensile stress on the induction of heat shock proteins (HSPs) and bone-related proteins by a murine preosteoblast cell line (MC3T3-E1). Cells were exposed to thermal stress using a water bath (44°C for 4 or 8 minutes) with postheating incubation (37°C for 4 hours) followed by exposure to cyclic strain (equibiaxial 3%, 0.2 Hz, cycle of 10-second tensile stress followed by 10-second rest). Combined thermal stress and tensile stress induced mRNA expression of HSP27 (1.41 relative fold induction (RFI) compared to sham-treated control), HSP70 (5.55 RFI), and osteopontin (1.44 RFI) but suppressed matrix metalloproteinase-9 (0.6 RFI) compared to the control. Combined thermal and tensile stress increased vascular endothelial growth factor (VEGF) secretion into the culture supernatant (1.54-fold increase compared to the control). Therefore, combined thermal and mechanical stress preconditioning can enhance HSP induction and influence protein expression important for bone tissue healing.
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    The Response of Preosteoblasts to Combined Shear and Thermal Stress for Bone Tissue Engineering
    Sampson, Alana Cherrell (Virginia Tech, 2014-11-06)
    Due to the fact that bone cells are highly responsive to mechanical stimuli, shear stress has been extensively studied for its ability to enhance osteogenic differentiation through mechanotransduction. In addition, thermal stress has also been explored as a conditioning method to stimulate cellular proliferation, differentiation, and cytoprotection through heat shock protein induction. Despite the beneficial effects observed with individual stress on cells, there has been little focus on the potential of a combination of stresses to improve cellular response. Therefore, the aim of this study was to investigate the effect of combined shear and thermal stress on preosteoblasts to stimulate an enhanced osteogenic response. To achieve this, MC3T3-E1 cells were exposed to one of the following protocols for an hour: no stress (control), shear stress at 1 dyne/cm2 using a parallel plate flow chamber, thermal stress in a 42°C incubator, or combined shear and thermal stress (1 dyne/cm2 at 42°C). Stress treatments were applied on Day 2, Day 6, and Day 10. To assess the early response of cells to stress treatments, we measured metabolic activity, expression of signaling factors, and HSPs following stress on Day 2. Despite an initial decrease in metabolism, combined stress stimulated a strong response in VEGF (12.49 RFI) COX-2 (12.32 RFI), HSPs (2-4 RFI) and increased PGE accumulation. The long-term cellular response to stress treatments was measured on Day 15 by evaluating the ability of combined stress to stimulate late stage markers of differentiation. Combined stress increased OPN gene and protein expression, yet OCN was minimally affected by stress treatments. However, mineralization was significantly decreased with combined stress. Overall, combined stress was able to stimulate an enhanced effect across a majority of the bone-related markers measured, whereas individual shear stress or thermal stress were limited in their response. This suggests that combined stress can provide the appropriate cues to modify osteoblast differentiation and generate an enhanced osteogenic response.