TRANSPLANTATION OF GUNN-RATS WITH AUTOLOGOUS FIBROBLASTS EXPRESSING BILIRUBIN UDP-GLUCURONOSYLTRANSFERASE - CORRECTION OF GENETIC DEFICIENCY AND TUMOR-FORMATION

The end product of the breakdown of the heme group of hemoglobin and o ther heme-containing proteins is bilirubin, Bilirubin is hydrophobic a nd cannot be excreted as such, Therefore, mammals have a liver enzyme bilirubin UDP-glucuronosyltransferase (B-UGT), which conjugates biliru bin with glucuronic acid, thereby making the molecule much more water soluble, Bilirubin glucuronides are secreted into bile, Patients with Crigler-Najjar (CN) disease have a deficiency in bilirubin UDP-glucuro nosyltransferase and acummulate high serum levels of bilirubin, An ani mal model for CN disease is the Gunn rat, The obvious target for gene therapy for CN disease is the liver, but because liver cells do only d ivide infrequently, they are difficult to transduce, To investigate wh ether cells that are easily transduced can be used to develop gene the rapy for CN disease, we have transduced Gunn rat fibroblasts with B-UG T, using a recombinant retrovirus. Gunn rat fibroblasts expressing B-U GT were able to glucuronidate bilirubin present in cell culture media, In this study, we describe the intraperitoneal transplantation of Gun n rats with Gunn rat fibroblasts expressing B-UGT, Transplantation of the fibroblasts corrected the genetic deficiency of the Gunn rats, ser um bilirubin concentrations of the transplanted Gunn rats were reduced to normal, and bilirubin glucuronides appeared in bile, However, due to the prolonged period of cell culture, the transplanted fibroblasts were transformed, and the experimental animals developed tumors after transplantation.