Somatic Cell Gene Transfer 
James M. Wilson, M.D., Ph.D. — Assistant Investigator 
Dr. Wilson is also Associate Professor of Internal Medicine and Biological Chemistry at the University of 
Michigan Medical School. He received his undergraduate degree in chemistry from Albion College and his 
Ph.D. (biological chemistry) and M.D. degrees from the University of Michigan. He completed a residency 
and clinical fellowship at Massachusetts General Hospital, Boston, and conducted postdoctoral research 
with Richard Mulligan at the Whitehead Institute, Massachusetts Institute of Technology. Dr. Wilson is 
investigating ways to treat genetic diseases by correcting the basic defects. 
GENE replacement therapies are being consid- 
ered for the treatment of a variety of ac- 
quired and inherited diseases. These novel thera- 
peutic modalities involve the transfer of genetic 
material into somatic tissues of affected individ- 
uals. The development of new therapies for car- 
diopulmonary diseases, based on gene transfer 
into hepatocytes and airway epithelial cells, is a 
major focus of my laboratory. 
Familial hypercholesterolemia (FH) is an auto- 
somal dominant disorder in humans that is an ex- 
cellent model for developing gene replacement 
therapies of hyperlipidemic states. Patients with 
the homozygous deficient form of FH have severe 
hypercholesterolemia and suffer life-threatening 
coronary artery disease in childhood that is refrac- 
tory to conventional medical therapies. The mo- 
lecular basis of this disorder is a systemic defi- 
ciency in the receptor that degrades low-density 
lipoprotein (LDL) , the primary carrier of choles- 
terol in the blood. Hepatocytes are the appro- 
priate target for gene transfer in this disease, 
since the liver is the organ primarily responsible 
for LDL metabolism and cholesterol excretion. 
We have used an animal model for FH — the 
Watanabe heritable hyperlipidemic (WHHL) rab- 
bit — to develop different types of liver-directed 
gene replacement therapies. One approach is sim- 
ilar in concept to the well-described bone 
marrow-directed gene therapies. This ex vivo 
method involves isolating hepatocytes from a ge- 
netically deficient animal, transferring functional 
genetic material into the hepatocytes in vitro, 
and returning the corrected cells to the affected 
recipient. We have used recombinant retrovi- 
ruses to transfer a functional gene for the human 
LDL receptor stably into hepatocytes derived 
from WHHL rabbits. Transplantation of these 
cells into WHHL rabbits leads to substantial de- 
creases in serum cholesterol for over four 
months. A similar approach may be therapeutic in 
patients with homozygous FH. 
An alternative and less invasive approach is to 
deliver a functional LDL receptor gene into the 
hepatocytes in vivo. We have developed an in 
vivo gene delivery system that is based on inter- 
actions with hepatocyte-specific receptors. Using 
this approach we can deliver reporter genes spe- 
cifically to hepatocytes in vivo and obtain ex- 
pression of the recombinant gene in liver for at 
least four months. Administration of a gene 
transfer substrate containing the LDL receptor 
gene into the circulation of WHHL rabbits led to 
significant reductions in the level of serum cho- 
lesterol. Hepatic overexpression of LDL receptor 
by gene transfer can potentially prevent the ath- 
erosclerotic disease in FH and other hyperlipid- 
emic states. This work is also supported by a grant 
from the National Institutes of Health. 
Cystic fibrosis (CF) is an inherited disease 
characterized by abnormal salt and water trans- 
port that leads to pathology within the pancreas 
and lung. CF is the most common lethal congeni- 
tal disease among Caucasians, with a prevalence 
of 1 in 2,000 births. The primary defect in the 
lung appears to be the production of thick abnor- 
mal mucus that plugs the airways and leads to 
infections. The recent discovery of the gene that 
causes CF suggests a new therapeutic strategy in 
which normal functioning CF genes are directly 
introduced into pancreatic or respiratory cells of 
affected patients. 
As a first step in the development of a genetic 
cure for CF, we have attempted to correct the 
physiological abnormality in cells from a CF pa- 
tient by introducing into them a CF gene that 
encodes CFTR (cystic fibrosis transmembrane reg- 
ulator), a normal functioning product. Replica- 
tion-defective viruses were used to shuttle a nor- 
mal CF gene into pancreatic cells from a patient 
with CF. Prior to gene transfer, the cells mani- 
fested the typical abnormalities associated with 
this disease (i.e., decreased transport of salt 
across the membrane). Following gene transfer, 
the cells regained normal regulation of salt trans- 
port. This demonstrates the feasibility of gene 
therapy in CF at a cellular level. 
Rational development of approaches for recon- 
stituting CFTR expression in vivo requires a defi- 
nition of endogenous CFTR expression in the 
normal human airway as well as an understanding 
of the biology of the epithelial cells that line the 
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