Transplants from pigs

Cryopreservation of primarily isolated porcine hepatocytes with UW solution

Development of liver-targeted cell therapies, such as hepatocyte transplantation and bioartificial livers, requires a large amount of functional hepatocytes as needed. To achieve this development, establishing an excellent cryopreservation method of hepatocytes is an extremely important issue. Therefore, we performed a comparative review of cryoprotective effects of various cryopreservation solutions using primarily isolated porcine hepatocytes. Porcine hepatocytes were isolated with a four-step dispase and collagenase perfusion method. The obtained hepatocytes with the initial viabilities of 76%, 84%, and 96% were assigned to the following four groups for cryopreservation at -80 degrees C: Dulbecco's modified Eagle's medium (DMEM) + 10% fetal bovine serum (FBS) + 12% dimethyl sulfoxide (DMSO) (group A), University of Wisconsin (UW) solution + 12% DMSO (group B), Cell Banker 1 (group C), and Cell Banker 2 (group D). The hepatocytes in each group were thawed at 3 days, 10 days, and 5 months of cryopreservation and subjected to comparative analyses, including viability, plating efficiency, LDH release, ammonia removal test, and lentiviral gene transfer. These parameters were the most favorable in the hepatocytes cryopreserved with UW solution. Approximately 5% of thawed cryopreserved porcine hepatocytes expressed LacZ activity after lentiviral transduction. Intrasplenic transplantation of UW solution-cryopreserved hepatocytes improved the survival of rats treated with D-galactosamine. UW solution maintained the functions of cryopreserved porcine hepatocytes.

Xenografts: are the risks so great that we should not proceed?

Animal organs could save patients needing transplants, but further research is necessary to resolve remaining problems with organ rejection. Furthermore, xenotransplantation risks transmitting animal pathogens to patients and to the general population. It would be unethical to proceed with clinical trials before principles and procedures for dealing with this risk are in place.

Monitoring xenotransplant recipients for infection by PERV

OBJECTIVES

Concerns have been raised over the possibility of transmission of porcine endogenous retrovirus (PERV) to porcine xenograft recipients.

METHODS

To help assess this risk, diagnostic assays capable of detection of an active, latent or cleared PERV infection, and the presence of pig cell microchimerism have been developed by a number of groups. Retrospective studies of patients exposed to living pig tissues have been performed using these assays to look for evidence of cross species transmission.

RESULTS

To date no evidence of PERV infection has been found in studies of humans exposed to pig tissues, despite evidence of long lived microchimerism.

CONCLUSIONS

These data suggest that PERV infection has not occurred in a clinical setting. However, as infection has been seen in a small animal model further investigation of the risk from PERV is warranted.