Differentiation of liver progenitor cell line to functional organotypic cultures in 3D nanofibrillar cellulose and hyaluronan-gelatin hydrogels.

Physiologically relevant hepatic cell culture models must be based on three-dimensional (3D) culture of human cells. However, liver cells are generally cultured in two-dimensional (2D) format that deviates from the normal in vivo morphology. We generated 3D culture environment for HepaRG liver progenitor cells using wood-derived nanofibrillar cellulose (NFC) and hyaluronan-gelatin (HG) hydrogels. Culture of undifferentiated HepaRG cells in NFC and HG hydrogels induced formation of 3D multicellular spheroids with apicobasal polarity and functional bile canaliculi-like structures, structural hallmarks of the liver tissue. Furthermore, hepatobiliary drug transporters, MRP2 and MDR1, were localized on the canalicular membranes of the spheroids and vectorial transport of fluorescent probes towards the biliary compartment was demonstrated. Cell culture in 3D hydrogel supported the mRNA expression of hepatocyte markers (albumin and CYP3A4), and metabolic activity of CYP3A4 in the HepaRG cell cultures. On the contrary, the 3D hydrogel cultures with pre-differentiated HepaRG cells showed decreasing expression of albumin and CYP3A4 transcripts as well as CYP3A4 activity. It is concluded that NFC and HG hydrogels expedite the hepatic differentiation of HepaRG liver progenitor cells better than the standard 2D culture environment. This was shown as improved cell morphology, expression and localization of hepatic markers, metabolic activity and vectorial transport. The NFC and HG hydrogels are promising materials for hepatic cell culture and tissue engineering.

Cationic amphiphilic star and linear block copolymers: synthesis, self-assembly, and in vitro gene transfection.

A series of amphiphilic star and linear block copolymers were synthesized using ATRP. The core consisted of either polystyrene (PS) or poly(n-butyl acrylate) (PBuA), having different glass-transition (T(g)) values. These polymers were used as macroinitiators in the polymerization of the cationic 2-(dimethylamino)ethyl methacrylate (DMAEMA). The polymers were used to study the effects of polymer architecture and flexibility on the self-assembling properties, DNA complexation, and transfection. All polymers formed core-shell micelles in aqueous solutions and condensed plasmid DNA. Linear PDMAEMA-PBuA-PDMAEMA has transfection efficiency comparable to PEI25K in ARPE19 cell line. Glassy state of the micellar core and star-shaped architecture decreased the DNA transfection compared with the rubbery and linear polymer structures. The polymers showed low cellular toxicity at low nitrogen/phosphate (n/p) ratios.