TIME-COURSE OF RECOMBINANT PROTEIN SECRETION AFTER LIPOSOME-MEDIATED GENE-TRANSFER IN A RABBIT ARTERIAL ORGAN-CULTURE MODEL

BACKGROUND: Little information exists regarding the time course of gene expression after arterial transfection. Accordingly, we sought to determine the time course of gene expression after liposome-mediated arterial gene transfer (lipofection) using an arterial organ culture model. EXPERIMENTAL DESIGN: Explanted segments of rabbit descending thoracic aorta were maintained in organ culture. Arterial gene transfer, facilitated by cationic liposomes (Lipofectin), was performed with the plasmid pXGH5 encoding the human growth hormone (hGH) under the control of mouse metallothionein-l promoter. RESULTS: The time course of hGH production after transfection with the plasmid pXGH5 was evaluated. Significant levels (181.0 +/- 33.9 ng/24 hours/gm) of hGH were detected within 24 hours post-transfection, reached a peak on day 7 (238.4 +/- 35.3 ng/24 hours/gm), and declined after day 10. At day 21, hGH could be observed in 50% of the arteries. Immunostaining with a monoclonal antibody for hGH revealed that only a small number of arterial cells (<1%) were responsible for production of hGH. CONCLUSIONS: The organ culture model is a feasible and efficient means for investigating the kinetics of arterial gene transfer. Transfection of pXGH5 results in significant levels of hGH for up to 3 weeks, despite anatomic evidence of only limited gene expression. These data thus support the notion that the magnitude and/or duration of gene expression may be disproportionately high, relative to anatomic assessment of transfection efficiency in the case of a transgene encoding for a secreted protein.