(15c) Elastin-Based Scaffolds for Three-Dimensional, in Vitro Liver Disease Models

Non Alcoholic Fatty Liver Disease (NAFLD) is a family of liver diseases associated with obesity. Initial stage of NAFLD is characterized by a fatty liver, referred to as steatosis, which progresses in some individuals to nonalcoholic steatohepatitis (NASH) and liver failure. Understanding the relationships amongst metabolic state (intracellular triglyceride), environmental stress (cytokine and oxidative stress), transcriptional regulation, and state-dependent stress responses (survival, necrosis or apoptosis) represent important steps in understanding the progression from steatosis to steatohepatitis. Several studies in the past have attempted to elucidate these mechanisms using primary hepatocytes or relevant hepatoma cell lines in 2-dimensional (2-D) monolayer in vitro cultures. These 2-D planar culture systems, unfortunately, do not represent the complex architecture of hepatic tissue in vivo. Therefore, we set out to design new biopolymer conjugates that will facilitate the creation of 3-D in vitro liver tissue models. To this end, we have engineered elastin-like polypeptide (ELP)-polyelectrolyte (PE) polymers and investigated their utility as suitable substrates for representative H35 rat hepatoma cells. ELPs are a family of polypeptides derived from a portion of the primary sequence of mammalian elastin, VPGXG, where V = valine, P = proline, G = glycine, and X = any amino acid except proline. ELPs and their derivatives have been used for a number of applications, including drug delivery, protein purification, and tissue engineering. We have shown that ELP-PE scaffolds are suitable for H35 cell culture and the chemical modification with PEs profoundly influenced cellular morphology to create 3-D spheroids. Further, TNF-alpha mediated activation of NFkB was investigated in both 2-D and 3-D culture settings. NFkB is a transcription factor with well established role in response to inflammatory mediators. However, its role in integrating metabolic and inflammatory stimuli is unclear. These studies therefore provide a good starting point to evaluate such relationships observed during NAFLD in a 3-D in vitro cell culture.