Gene carrier system by means of alveolar macrophage to the lung : an attempt of gene therapy for lung diseases.

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A novel gene delivery system to lung has been established in mice. The method employs intravenous injection of syngeneic viable cells that are transfected with a target gene in ex vivo.In a series of preliminary studies, attempts of transfecting syngeneic alveolar macrophages with a reporter gene by means of non-viral methods, i.e. calcium-phosphate co-precipitation, electropolation and lipofectin have failed, In the next step, syngeneic fibroblasts instead of alveolar macrophages were utilized to reveal high efficacy of gene transfection. Eventually, a plasmid that had bacterial beta-galactosidase (beta-gal) gene under the control of a beta-actin promoter was transfected to an established Balb/c mouse derived fibroblast cell line, A3 1, by the calcium-phosphate co-precipitation method in vitro. The cells were propagated in vitro and administrated to syngeneic Balb/c mice by intra tracheal (I.T.) or intra venous (I.V.) method. After the administrations, each organ, induding lung, heart, kidney, liver, brain and spleen was removed from the sacrificed mice, and the beta-gal activity in the each organ was assessed by ELISA.A high level of beta -gal expression was observed in lung tissues, lasting as long as about two weeks, with a peak at 2 hours after the administration. Kinetic differences of the gene expression between I.T.and I.V.administration were comparatively evaluated. All other organs, except for hearts, showed no detectable expression after either I.T.or I.V.administration, when evaluated by ELISA and RT-PCR.Histological examinations with beta -gal staining showed identification and localization of the administrated cells those showed high expression of the introduced gene in the lung. Other histological examination with hematoxylin-eosin staining disclosed no significant lesions such as inflammation and fibrosis in the lungs.In conclusion, this study demonstrated potential clinical capability and safety of this gene delivery system for lung diseases.