Fabrication of Inverted Colloidal Crystal Poly(ethylene glycol) Scaffold: A Three-dimensional Cell Culture Platform for Liver Tissue Engineering.

The ability to maintain hepatocyte function in vitro, for the purpose of testing xenobiotics' cytotoxicity, studying virus infection and developing drugs targeted at the liver, requires a platform in which cells receive proper biochemical and mechanical cues. Recent liver tissue engineering systems have employed three-dimensional (3D) scaffolds composed of synthetic or natural hydrogels, given their high water retention and their ability to provide the mechanical stimuli needed by the cells. There has been growing interest in the inverted colloidal crystal (ICC) scaffold, a recent development, which allows high spatial organization, homotypic and heterotypic cell interaction, as well as cell-extracellular matrix (ECM) interaction. Herein, we describe a protocol to fabricate the ICC scaffold using poly (ethylene glycol) diacrylate (PEGDA) and the particle leaching method. Briefly, a lattice is made from microsphere particles, after which a pre-polymer solution is added, properly polymerized, and the particles are then removed, or leached, using an organic solvent (e.g., tetrahydrofuran). The dissolution of the lattice results in a highly porous scaffold with controlled pore sizes and interconnectivities that allow media to reach cells more easily. This unique structure allows high surface area for the cells to adhere to as well as easy communication between pores, and the ability to coat the PEGDA ICC scaffold with proteins also shows a marked effect on cell performance. We analyze the morphology of the scaffold as well as the hepatocarcinoma cell (Huh-7.5) behavior in terms of viability and function to explore the effect of ICC structure and ECM coatings. Overall, this paper provides a detailed protocol of an emerging scaffold that has wide applications in tissue engineering, especially liver tissue engineering.

Phenotypic regulation of liver cells in a biofunctionalized three-dimensional hydrogel platform.

Loss of function is a major challenge for hepatocytes that are cultured on two-dimensional (2D) cell culture platforms. Biofunctionalized three-dimensional (3D) scaffolds produced by microfabrication strategies can overcome these limitations by presenting vital environmental cues, strong mechanical properties, and three-dimensional geometry to enable high-fidelity liver tissue engineering. Herein, we report the detailed investigation of hepatocarcinoma (Huh 7.5) cellular behavior in a collagen-functionalized microsphere-templated poly(ethylene glycol) (PEG) hydrogel scaffold which promotes 3D hepatic sheet morphology. Collagen conjugation led to improved liver-specific functions, including albumin production and cytochrome P450 (CYP450) activity. Importantly, the gene expression of numerous cell-adhesion markers was enhanced along with stimulated innate hepatocyte fibronectin production. Taken together, the findings reveal a close connection between hepatic cell morphology and gene expression, offering evidence that surface-coated collagen in the 3D hydrogel platform triggers the upregulation of hepatocyte-specific transcription factors and the secretion of liver metabolic markers.

Biofunctionalized Hydrogel Microscaffolds Promote 3D Hepatic Sheet Morphology.

Development of artificial tissues providing the proper geometrical, mechanical, and environmental cues for cells is highly coveted in the field of tissue engineering. Recently, microfabrication strategies in combination with other chemistries have been utilized to capture the architectural complexity of intricate organs, such as the liver, in in vitro platforms. Here it is shown that a biofunctionalized poly (ethylene glycol) (PEG) hydrogel scaffold, fabricated using a sphere-template, facilitates hepatic sheet formation that follows the microscale patterns of the scaffold surface. The design takes advantage of the excellent diffusion properties of porous, uniform 3D hydrogel platforms, and the enhanced-cell-extracellular matrix interaction with the display of conjugated collagen type I, which in turn elicits favorable Huh-7.5 response. Collectively, the experimental findings and corresponding simulations demonstrate the importance of biofunctionalized porous scaffolds and indicate that the microscaffold shows promise in liver tissue engineering applications and provides distinct advantages over current cell sheet and hepatocyte spheroid technologies.