Date of Award

2014

Document Type

Thesis

Degree Name

Master of Science (MS)

First Advisor

Aravamudhan, Shyam Dr.

Abstract

Cells are constantly subjected to mechanical stress during various physical activities. Understanding the role of the resultant mechanical stresses on cellular mechanotransduction is critical for considerate various cellular activities in the body such as control of cell growth, migration, differentiation, apoptosis and wound repair. The long-term goal is to understand whether it is possible to control cell functions through mechanical forces. Specifically, in this work, we report on the cellular and mechanistic response of NIH/3T3 fibroblastic cells (cultured on silicone membrane), when subjected to cyclic biaxial stretch generated in a custom-built stretching system, as described in Karumbaiah et al (Karumbaiah et al., 2012). The silicone membrane was first plasma-treated to increase its hydrophilicity, followed by coating a layer of Collagen type-I to increase cell adhesion to the membrane. Cell viability and morphological changes at the cell surface were studied in response to cyclic biaxial forces to determine the effect of time and amplitude on cell responses. In particular, the cell responses have been studied at 5% up to 10% strain with keeping frequency constant as low as 0.05 cycles/sec along with variable stretching time (6 and 24 hours) to model a situation closer to in vivo. Our results indicate that stretching cells under applied conditions have no considerable negative effect on cells viability while significantly increase the proliferation of cells. Also, there is a migration happened for cells from inner parts of the membrane to the corners which might be a result of the combination of shear stress (resulted from liquid movements during stretch) and the localized bending stress at the range of bending forces (when the membrane bends over glass indenters). Additionally, there is no evidence of alignment of the actin filament of cells under biaxial force whereas the spreading factor which is an indication of actin filament's response to the cell's mechanical environment was increased for stretched samples compared to the control.

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