EXPERIMENTAL BRONCHIOLITIS OBLITERANS INDUCED BY IN-VIVO HVJ-LIPOSOME-MEDIATED ENDOTHELIN-1 GENE-TRANSFER

Background. Bronchiolitis obliterans (OB) is a lesion that results whe n injury to small conducting airways is repaired by a proliferation of fibrous granulation tissue. Bronchiolitis obliterans has emerged as a main cause of morbidity and mortality in the setting of lung and hear t-ling transplantation. Endothelin-1 (ET-1), initially discovered as a vasoconstrictive peptide, has a mitogenic activity on vascular smooth cells and airway epithelial cells. Overproduction of endothelin has b een reported in patients with OB or chronic rejection after lung trans plantation. It is still undetermined whether locally overexpressed ET- 1 has a potential impact in the pathogenesis of OB. Methods. We loclly overexpressed ET-1 using ultraviolet irradiation-inactivated hemagglu tinating virus of Japan (HVJ)-liposome-mediated in vivo gene transfer. Plasmid DNA of prepor-ET-1 and high mobililty group 1 protein were co encapsulated in liposomes, and were introduced into airway epithelial cells by HVJ-mediated membrane fusion. Control animals received instil lation of HVJ-liposome with an empty expression cassette. To confirm t he efficiency of transfection, HVJ liposome with beta-galactosidase ge ne was introduced. The expression of ET-1 and beta-galactosidase was a ssessed by immunohistochemistry. Results. Bronchial epithelium alveola r cells and alveolar macrophage were stained blue (X-Gal) 1 week after in vivo gene transfer of beta-galactosidase gene, indicating beta-gal activity. In animals 1 to 2 weeks after in vivo transfection of prepr o-ET-1 gene, hyperplastic connective tissue plaque was seen in the alv eolar duct and small conducting airway, indicating histologically dist inctive bronchiolitis obliterans. Strong ET-1-like immunoactivities we re seen in the airway epithelial, hyperplastic connective tissue, and alveolar cells. No histopathologic changes were seen in the control an imals. Conclusions. These results suggested that ET-1 may play an impo rtant role in the pathogenesis of OB. The effective pharmacologic anta gonist or inhibitor may possibly control the progression of disease in patients of OB. (C) 1997 by The Society of Thoracic Surgeons.