Enhanced Gene Expression in Mouse Lung after PEI–DNA Aerosol Delivery

Abstract

Aerosol gene delivery to the pulmonary system has vast potential for many diseases, including cystic fibrosis and lung cancer. We recently reported that polyethyleneimine (PEI), a cationic polymer, holds promise as a gene delivery vector for transfection in lung by aerosol. To further optimize the gene expression in the lung by aerosol, we utilized 5% CO(2) in air for the nebulization of PEI-DNA complexes. Five percent CO(2)-in-air gave a threefold higher gene expression compared to normal air using the chloramphenicol acetyl transferase (CAT) reporter gene delivered by Aerotech II nebulizer. The delivery of DNA by PEI was dose dependent with the highest expression obtained when 2 mg of DNA in 10 ml was nebulized at a PEI nitrogen:DNA phosphate (N:P) ratio of 10:1. The optimal N:P ratio for lung transfection was found to be between 10:1 and 20:1 using the CAT and luciferase reporter genes. The time-course studies showed the highest expression at 24 h after aerosol delivery and 40-50% of peak level was detectable even after a week. Tissue distribution indicates the expression to be specific to the lung with no detectable expression in any other tissue examined. Histological and biochemical analysis of lungs revealed no evidence of acute inflammation.

Growth suppression of established human osteosarcoma lung metastases in mice by aerosol gene therapy with PEI– p53 complexes

“…In addition, there were no significant differences in weights between nontumor animals and tumor-bearing animals treated with PEI -p53 or PEIp53CD( 1-366), providing additional evidence of the relative health of the animals undergoing long -term aerosol PEI treatment. This is in agreement with our previous reports of the lack of an acute inflammatory response 15 and a reduction in pulmonary cytokine response 19 after short -term aerosol exposure to PEI -DNA formulations when compared to other delivery vectors or modes of plasmid DNA delivery.…”

“…15 The efficiency of expression of aerosol-delivered p53 and p53CD( 1 -366) in airway epithelial cells is nearly 100% with evidence of staining in alveolar cells. A detailed description of the deposition of aerosolized PEI and transgene expression in the lungs is described elsewhere.…”

“…Aerosol was delivered using 5% CO 2 in air as described previously by this laboratory. 15 The exposure required approximately 30 minutes, during which time the mice were allowed to move freely about the chamber.…”

“…We have previously found that polyethyleneimine:DNA (PEI -DNA ) complexes are stable during the process of jet nebulization and deposit uniformly throughout the lung. We have recently shown that aerosol delivery of PEI -DNA complexes results in significant levels of gene expression in the lungs of mice, 14,15 and is associated with minimal inflammatory response. 15 Use of this technology produced substantial serum antibody responses to human growth hormone gene 14 and, in addition, produced significant antitumor effects in a mouse pulmonary model of murine melanoma.…”

“…We have recently shown that aerosol delivery of PEI -DNA complexes results in significant levels of gene expression in the lungs of mice, 14,15 and is associated with minimal inflammatory response. 15 Use of this technology produced substantial serum antibody responses to human growth hormone gene 14 and, in addition, produced significant antitumor effects in a mouse pulmonary model of murine melanoma. 7 For these reasons, we have chosen to examine the effect of p53 and p53CD( 1 -366 ) gene therapy for treating human osteosarcoma lung metastases in the SAOS -LM6 -nude mouse model using aerosol PEI -p53 delivery.…”