In this thesis, the effects of extracellular matrix rigidity on TGFβ-induced histone modifications and α-smooth muscle actin (α-SMA) expression in mammary epithelial cells was studied. A cavitation rheology methodology for characterization of mechanical properties of polyacrylamide hydrogels began to be developed for the research group. Hydrogels of known stiffness were analyzed by this method, and the elastic modulus was calculated using two different relationships. Equation 2 (Hutchens) was found to yield a more accurate result, and gel geometry was found to have an effect on the calculated modulus. Next, mammary epithelial cells were grown on polyacrylamide hydrogel substrata that mimicked the rigidity of normal epithelial tissue (330 Pa) and cancerous breast tissue (6320 Pa). The methyltransferase inhibitor BIX- 01338 was used to inhibit methylation of lysines on histones, and expression level of α-SMA, a mesenchymal marker, was quantified to determine the extent to which epithelial-mesenchymal transition (EMT) occurred in cells. TGFβ-treated cells expressed higher levels of α-SMA when not treated with BIX-01338, indicating a relationship between histone methylation and EMT. TGFβ-treated cells grown on stiffer substrata (6320 Pa) expressed higher levels of α-SMA than cells grown on softer substrata (330 Pa), suggesting that a higher extracellular matrix rigidity further induces EMT.
