Date of this Version
Rethwisch, Mary and Srivatsan Kidambi. The Effect of Substrate Stiffness on VL-17A Proliferation and Protein Expression. University of Nebraska-Lincoln. 2018
In this work the effects of substrate stiffness were examined on cell proliferation and cytochrome P450 2D1 (CYP2E1) protein expression in VL-17A cells. While it has long been understood that liver disease is often characterized by an increase in stiffness in the liver environment, recent studies have shown that the mechanical cues from the microenvironment may influence cell function. This study uses a polydimethyl siloxane (PDMS) substrate to tune substrate stiffness to physiologically relevant levels of 2 kPa for healthy tissue, 12 kPa for mid-stage fibrosis tissue, and 25 kPa for fibrotic tissue. Substrates were coated with polyelectrolyte multilayers (PEMs) made up of a positively charged layer of poly(diallyldimethylammonium chloride) (PDAC), and a negatively charged layer of sodium dodecyl sulfate (SDS). The negatively charged SDS encourages cell adhesion. VL-17A cells were cultured for five days, and proliferation study images were recorded every 24 hours. Overall, a marked increase in cell proliferation was observed on the stiffer substrates, suggesting fibrotic cell proliferation function. No statistically relevant change in CYP2E1 data was detected on the fifth day of cell culture using Western Blot analysis and the ANOVA statistical comparison method. The lack of change in protein expression may indicate a delayed response to mechanical cues, or that decreased cellular function in ethanol oxidation may not be tied to the stiffness of a cell’s physical environment. While the tissue culture model studied could benefit from quantitative proliferation studies, and more extensive protein expression studies, this study makes a strong case for the relationship between substrate stiffness and cell function observed in fibrotic tissue.