Microencapsulated human hepatoma (HepG2) cells: in vitro growth and protein release

The feasibility of a microencapsulation process ultimately for cell transplantation was investigated by encapsulating human hepatoma (HepG2) cells in hydroxyethyl methacrylate-methyl methacrylate (HEMA-MMA) membranes through an interfacial precipitation process. Changes in viability and metabolic activity as well as protein secretion by the encapsulated cells were studied in vitro. When encapsulated at either low or high density (1 or 5 x 10(6) cells/mL, respectively), HepG2 cells retained their active metabolic state and/or proliferated during the initial 1-week period, after which a significant drop in cell viability was obtained. Encapsulation of a biological attachment substrate, Matrigel, along with the cells, however, resulted in rapid proliferation in both low and high density capsules with prolonged maintenance of an active metabolic state. The secretion of four model proteins (alpha 1-acid glycoprotein, alpha 1-antitrypsin, haptaglobin and fibrinogen) was demonstrated during the 2-week study period for the Matrigel encapsulated cells. Furthermore, the encapsulated cells remained responsive to interleukin 6 (IL6), a physiological stimulator of plasma protein secretion, as determined by the elevated secretion of haptaglobin in response to IL6 treatment. We conclude that HEMA-MMA capsules, in the presence of an attachment substrate, provide a suitable environment for the growth and expression of differentiated functions of encapsulated hepatoma cells.