title: Biochemical properties of encapsulated high-density 3-D HepG2 aggregates formed in an ultrasound trap for application in hepatotoxicity studies : Biochemical responses of encapsulated 3-D HepG2 aggregates.
abstract: This paper describes the alginate encapsulation of preformed high-density 3-D HepG2 cell aggregates that guarantees good maintenance of liver-specific biomarker expression. The process involves forming a high-density (> or =7 x 10(4) cells/aggregate) discoid 3-D cell aggregate in an ultrasound trap, which is subsequently recovered and encapsulated in alginate/CaCl(2) hydrogel. Glucose secretion/consumption, lactate release, detoxifying enzyme capacity, cytokeratin-18 expression as well as hypoxia were characterized in encapsulated 3-D HepG2 aggregates over 10 days in culture. Encapsulated 3-D HepG2 aggregates released glucose into the media, although this ability was exhibited only after 1 day in culture and was subsequently lost over the ensuing 9 days. In contrast, lactate was constantly released into the media. Significantly more lactate was secreted after 3 days in culture indicating a more hypoxic environment and hence a higher rate of anaerobic glycolysis. Aggregates consistently expressed cytokeratin-18. Cytochrome P450-1A1 activity reached a maximum on day 1 of culture followed by a progressive reduction to basal levels, while P450-3A4 activity was up-regulated in a time-dependent manner reaching a peak on day 7 in culture. Glutathione-S-transferase activity, on the other hand, was at more physiological levels and remained constant over the 10-day culture period. The ultrasound trap allowed the rapid (within 5 min) generation of uniformly shaped and sized aggregates. The results reported here suggest that ultrasound-formed 3-D HepG2 aggregates can serve as alternative in vitro models providing a quick outlook on toxicity, in a tissue-mimetic manner, thus offering the future option of a cost-effective screening platform for pharmaceutical development.
authors.affiliation: Cardiff University, Wales, UK. Bazoud@cf.ac.uk
authors.forename: Despina
authors.initials: D
authors.lastname: Bazou
mesh_terms: D000464:Alginates; D001672:Biocompatible Materials; D002448:Cell Adhesion; D002449:Cell Aggregation / Q000502:physiology*; D018929:Cell Culture Techniques; D015687:Cell Hypoxia / Q000502:physiology; D051544:Cytochrome P-450 CYP3A; D005947:Glucose / Q000378:metabolism; D056945:Hep G2 Cells / Q000502:physiology; D022781:Hepatocytes / Q000378:metabolism*; D006801:Humans; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate; D053538:Keratin-18 / Q000378:metabolism; D019344:Lactic Acid / Q000378:metabolism; D014465:Ultrasonics
chemical_list: D000464:Alginates; D001672:Biocompatible Materials; D053538:Keratin-18; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate; D019344:Lactic Acid; D051544:Cytochrome P-450 CYP3A; C510163:CYP3A4 protein, human; D005947:Glucose