Preservation of microplate-attached human hepatoma cells and their use in cytotoxicity tests

We investigated the feasibility of hypothermic- orcryogenically-preserved human hepatoma Hep G2 cell preculturedin 96-well plates in cytotoxicity testings. First, we observedthat microplates precoated with both collagen (CN) and pronectin (PN) showed significantly improved living cell adhesion (71.0 +/- 5.5%) after 48 hr of cryopreservation with 10%-DMSO containing culture medium, whereas non-coated surfaces gave very low living cell adhesion (33.5 +/- 2.1%). Hypothermic preservation was most suitable for short-term storage, and cryogenic preservation at -20 degrees C allowed cells to be used within a week of the storage period. Only cryopreservation in a deep freezer (-85 degrees C) gave satisfactory results in much longer period of storage. Second, we evaluated the cytotoxicity of ten chemicals during 48 hr of exposure using hypothermically - (4 degrees C for 2 days) or cryogenically - (-85 degrees C for 7 days) preserved cells cultured inCN/PN-precoated microplates in comparison with results fromfreshly inoculated cells. Although almost the same LD(50)values were obtained, LD(10) values of relatively hydrophilic chemicals obtained with cryopreserved cell were significantly lowered. These results shown that CN/PN-precoating is effective in keeping cells attached even in recultivation of preserved cells and that the toxicities of relatively hydrophilic chemicals tend to be overestimated when we use preserved cells in that manner.