Figure 2. "Open-ended" xenografts. (A) Xenografts were ligated to flexible 
plastic tubing and implanted subcutaneously. Implants were sutured such that 
the ends of the tubing exited through the back of the neck. (B) Transmission 
electron micrograph of a fully differentiated bronchial xenograft epithelium. 
Xenograft was seeded with 2 x lCr cells and allowed to develop for 3 weeks. C, 
ciliated cell; G, goblet cell; and B, basal cell, (bar = 20 jum). 
Primary airway epithelial cells are released from lung tissue obtained in the 
setting of lung transplantation. CF cells are obtained from the bronchi of diseased 
lung that has been removed, and non-CF cells are obtained from proximal airway of 
the lung that is being transplanted into the CF patient. The cells are cultured for 
several days in the presence of antibiotics, released with trypsin, and seeded into the 
lumen of rat trachea that have been stripped of their epithelium by freeze thawing. 
The seeded grafts are then implanted subcutaneously into the flanks of nu/nu mice 
with the proximal and distal ports of the graft open to the environment via tubing 
ligated to the ends. The grafts are irrigated with normal saline biweekly to remove 
accumulations of mucus. 
The grafts are allowed to mature in vivo for 3 weeks after which a fully 
differentiated pseudostratified epithelium has developed. We have now generated 
Recombinant DNA Research, V olume 17 
[449] 
