Morphological assessment of hepatoma cells (HepG2) microencapsulated in a HEMA-MMA copolymer with and without Matrigel

Abstract

Hepatoma cells (HepG2), an anchorage-dependent cell line, were microencapsulated in a HEMA-MMA polyacrylate membrane to which the cells do not adhere. This environment was altered by the coencapsulation of Matrigel, a reconstituted extracellular matrix derived from the Engelbreth-Holm-Swarm (EHS) mouse tumor basement membrane, to provide sites for cell attachment. The effect on the cells of these two capsule microenvironments during a 2-week in vitro culture period was assessed by examining the spatial arrangement, morphology, and viability of the cells using light microscopy and scanning electron microscopy (SEM). In preparation for microscopy, dissolution of the polymer was prevented by the use of frozen sections embedded in a water-soluble compound. Similarly, freeze cleavage of conductively stained capsules permitted SEM observation of the capsule interior along with ultrastructural detail of the cells. In the absence of Matrigel, cells in HEMA-MMA capsules were found to form aggregates in intracapsular pockets with central necrosis occurring at day 7 in large aggregates. The coencapsulation of HepG2 cells with Matrigel, resulted in an initially uniform distribution of essentially individual cells with aggregates appearing later within the Matrigel. Many cells within these capsules had remained viable when examined up to day 14 with only limited cellular necrosis, implying a favorable environment for microencapsulated HepG2 cells.