An improvement in the attaching capability of cryopreserved human hepatocytes by a proteinaceous high molecule, sericin, in the serum-free solution.

The methodology of cryopreservation of human hepatocytes remains unsatisfactory. Even when the viability of thawed cells is tolerable, the cells often lose the attaching capability to a culture dish, resulting in the cells' inability to survive. Previously, we described the effectiveness of maltose on the attachment of hepatocytes. This article demonstrates that a silk-derived high molecular protein, sericin, improves the cell-attaching capability in the serum-free freezing medium. When human hepatocytes [initial viability: 60.9 ± 3.1% (mean ± SD, n = 3)] were frozen with serum-free Dulbecco's modified Eagle medium (DMEM) containing 10% dimethyl sulfoxide (DMSO), the viability was 29.4 ± 3.2% and the cell-attaching capability 20.4 ± 4.1%. On the other hand, DMEM containing 10% DMSO and 1% sericin increased the values to 45.0 ± 0.8% and 26.2 ± 3.2%. Moreover, the addition of 0.1 mol/L maltose to the sericin-containing medium improved to 42.2 ± 3.2% and 51.1 ± 1.0%, as we demonstrated in a previous report. The present results indicated that sericin combined with maltose is a novel additive in the serum-free freezing medium for human hepatocytes.