Human Gene Therapy Subcommittee - 4/5/91 
therapy. There are four basic science components. The first takes place in Dr. Woo's 
laboratory, which studies animal models for hepatic gene therapy. TTie second is in Dr. 
Darlington's lab, which involves hepatocellular cultivation. The third takes place in Dr. 
Mary Brandt's laboratory, which addresses the surgical aspects of hepatocellular 
transplantation. The last, which is beginning to take place in Dr. Ledley's lab, is the 
application of this technology to human cells. In development of this project there are 
many clinical problems to address. The first is whether one can perform hepatocyte 
transplantation. The second is to determine whether the patients could benefit. The 
third is to evaluate safety as well as the psychosocial implications. 
Dr. Ledley said that the basic scheme for targeting gene therapy to the liver is to treat a 
patient who has a genetic defect in his or her liver by doing a partial hepatectomy, 
separating out the liver cells from that surgical specimen, growing them in culture, 
introducing a recombinant gene by gene transduction, perhaps selecting those cells, and 
then transplanting those cells back into the patient as an autologous transplant. The 
problem with these experiments, and one of the reasons this technology has never been 
applied to humans, is that once the liver cell is returned to the liver, it looks like every 
other cell. Previous investigators have never been able to prove that the transplant 
worked. Genetic markers have not been available for use in animal experiments in the 
past. When this project was developed. Dr. Woo's laboratory had made two transgenic 
mice. One was a transgenic mouse which expressed the human alpha- 1 -antitrypsin gene, 
and did so in a tissue-specific manner, meaning that this gene is only expressed in the 
liver cells of this mouse. The second mouse had the E. coli beta-galactosidase gene 
under control of a liver-specific promoter, so that this gene was only expressed in the 
liver cells of this mouse. When these two mice were bred together, the hybrid mouse 
had a liver which produced both human alpha- 1 -anti tripysin which was secreted into the 
blood, and could be quantitated by drawing blood, and beta-galactosidase which can be 
stained by histochemical methods. Using this mouse, it was possible to do the same 
transplant experiments that others had done, and now actually see whether the 
experiment worked. When transplants were performed into a splenic site, the human 
protein was present, showing that the cells with the genetic marker had been 
transplanted successfully, had engrafted, and were stable. With histochemical staining, it 
was determined that when the cells were injected into the spleen, they migrated to the 
liver, and none remained in the spleen. 
Dr. Ledley presented data on patient referrals, and said many of these children die. He 
described a psychosocial study that assesses whether patients really know enough to give 
informed consent and also to provide long-term follow-up to make sure that there are no 
ill effects to the patient or the community. 
Dr. Ledley indicated that the protocol proposes to take patients with fulminant hepatitis 
for whom liver transplantation is not available and to try hepatocellular transplant to 
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Recombinant DNA Research, Volume 14 
