Cryopreservation of hepatocyte monolayers

The ability to cryopreserve hepatocytes would be useful both to the pharmaceutical industry and for bioartificial liver support systems. Unfortunately, suspension cryopreservation protocols typically result in low attachment efficiencies of cells upon thawing. To circumvent this problem, we have frozen rat hepatocytes as monolayers on collagen substrates, and attempted to optimise this cryopreservation protocol. A variety of parameters were measured in non-frozen and post-thaw frozen monolayer cultures, including viability, total protein and intracellular reduced glutathione (GSH) concentration, kaempherol glucuronidation, and testosterone hydroxylation. The effect of altering cryopreservation media composition (% of foetal calf serum varying between 0-90%) or freezing (0.4-3.8ºC/min) and thawing rates (26-128ºC/min) on these parameters was investigated. Under optimal conditions, post thaw cryopreserved cells maintained 72±4% viability, 65±4% total protein, 46±8% GSH, 48±8% kaempherol glucuronidation, and 16±11% testosterone hydroxylation of their corresponding non-frozen controls (mean ±SEM, n=3). Cryopreservation of hepatocyte monolayers as opposed to suspensions results in a more representative population of cells, with high viability, function, and recovery rates.