transfer in the WHHL rabbit, factor IX gene transfer 
in a canine model of hemophilia B, and ornithine 
transcarbamylase gene transfer in a mouse model of 
hyperammonemia. The use of this technology to 
treat ornithine transcarbamylase deficiency has 
been supported by the National Institutes of Health. 
Cystic Fibrosis 
The recent isolation of the gene responsible for 
cystic fibrosis (CF) has provided exciting opportuni- 
ties to study the pathogenesis of the disease and to 
design new strategies for therapy based on somatic 
gene transfer. 
CF is an autosomal recessive disease marked by 
defective salt and water transport across epithelia of 
a variety of organs. The protein product of the CF 
gene, the cystic fibrosis transmembrane conduc- 
tance regulator (CFTR) , functions in part as a chlo- 
ride channel in the plasma membrane. 
Soon after the isolation of the CF gene by other 
investigators. Dr. Wilson began a series of projects 
whose long-range goal is to treat the pulmonary 
manifestations of CF by gene therapy directed to the 
airway epithelial cells. The first step was to recon- 
struct a normal CF gene and clone it into a recombi- 
nant retrovirus capable of efficiently transducing 
human cells. Pancreatic cells isolated from a CF pa- 
tient regained normal physiologic functions (i.e., 
cAMP-regulated transpon of chloride) when ex- 
posed to the CFTR-transducing retrovirus. 
In order to design rational strategies for reconsti- 
tuting CFTR expression in the lungs of CF patients, 
it was necessary to define precisely the distribution 
of endogenous CFTR expression in the human lung. 
Techniques of in situ hybridization and immunocy- 
tochemistry were used to localize CFTR in human 
lung specimens. Analysis of the proximal airway re- 
vealed low levels of CFTR expression in the surface 
epithelium, with substantially higher expression in 
cells of submucosal glands, structures that produce 
large quantities of mucus. High levels of CFTR were 
also detected in a subpopulation of surface epithe- 
lial cells that populate bronchioles of the distal air- 
way as well as a minority of the cells that line 
alveoli. 
Critical to the study of CF lung pathogenesis and 
the development and characterization of ap- 
proaches to gene therapy is the availability of an 
authentic animal model of the human airway. Epi- 
thelial cells derived from human non-CF and CF air- 
ways are harvested from lung tissue and seeded into 
denuded rat trachea, which are then implanted into 
athymic {nu/nu) mice. Xenografts develop fully 
diff'erentiated human epithelium within 3-4 weeks. 
This model has been used to evaluate the feasibility 
of gene therapy with several recombinant viruses. 
Efficient and stable genetic reconstitution was only 
obtained with recombinant retroviruses when they 
were delivered to an undifferentiated, regenerating 
xenograft; essentially no gene transfer was detected 
when the xenograft epithelium was fully diff'eren- 
tiated at the time of gene transfer. In contrast, recom- 
binant adenoviruses were capable of efficiently 
transferring a CFTR transgene into cells of a fully 
differentiated epithelium. Furthermore, transgene 
expression was stable for the lifetime of the grafts, 
which was usually 4-6 weeks. 
Dr. Wilson is also Associate Professor of Inter- 
nal Medicine and Biological Chemistry at the Uni- 
versity of Michigan Medical School. 
Articles 
Askari, F., and Wilson, J.M. 1992. Provocative gene 
therapy strategy for the treatment of hepatocellu- 
lar carcinoma. Hepatology 16:273-274. 
Chowdhury, J.R., Grossman, M., Gupta, S., 
Chowdhury, N.R., Baker, J.R., Jr., and Wilson, 
J.M. 1991. Long-term improvement of hypercho- 
lesterolemia after ex vivo gene therapy in LDLR- 
deficient rabbits. Science 254:1802-1805. 
Collins, F.S., and Wilson, J.M. 1992. Cystic fibro- 
sis. A welcome animal model. Nature 358:708- 
709. 
Engelhardt, J.F., Allen, E.D., and Wilson, J.M. 
1991. Reconstitution of tracheal grafts with a ge- 
netically modified epithelium. Proc Natl Acad 
Sci USA 88:11192-11196. 
Grossman, M., Raper, S.E., and Wilson, J.M. 1991. 
Towards liver-directed gene therapy: retrovirus- 
mediated gene transfer into human hepatocytes. 
Somat Cell Mol Genet 17:601-607. 
Grossman, M., and Wilson, J.M. 1 992. Frontiers in 
gene therapy: LDL receptor replacement for hy- 
percholesterolemia. / Z«fc Clin Med 119:457- 
460. 
Jiwa, A., and Wilson, J.M. 1991. Selection of rare 
event cells expressing /3-galactosidase. Methods 
[companion to Methods Enzymol] 2:272-281 . 
Krauss,J.C., Bond, L.M., Todd, R.F., III, and Wilson, 
J.M. 1991. Expression of retroviral transduced 
human CD 18 in murine cells: an in vitro model of 
gene therapy for leukocyte adhesion deficiency. 
Hum Gene Ther 2:221-228. 
Krauss, J.C., Mayo-Bond, L.A., Rogers, C.E., Weber, 
K.L., Todd, R.F., III, and Wilson, J.M. 1991. An 
in vivo animal model of gene therapy for leuko- 
cyte adhesion deficiency. / Clin Invest 88: 1 4 1 2- 
1417. 
Raper, S.E., Wilson, J.M., and Grossman, M. 1992. 
CELL BIOLOGY AND REGULATION 
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