Gene Delivery Using Physical Methods - Challenges in Delivery of Therapeutic Genomics and Proteomics - page 86

erythropoietin (EPO) and leptin, with encouraging results. Isner, in 1999, proposed
intramuscular gene transfer for therapeutic angiogenesis [12] by delivering the plas-
mid DNA for vascular endothelial growth factor (VEGF). This method promotes
the development of supplemental collateral blood vessels that constitute endoge-
nous bypass conduits around occluded native arteries, to treat critical limb ischemia
[13,14] and myocardial ischemia [15] .
Apart from that attained for skeletal muscles, efficient transgene expression was
achieved on direct injection of DNA to the liver [16,17] , solid tumors [18] , epidermis
[19] , hair follicles [19] , and lung airways [20] .
Scientists studied the direct intratumoral injection of various cytokine and
tumor growth inhibitory genes, with satisfactory results for tumor vaccination [21] .
Antitumor immunity was achieved by direct injection of tumor growth inhibitory
genes, which inhibited the tumor growth and elicited an immune response via the
uptake of apoptotic tumor cells by antigen-presenting cells [21] .
Direct intratracheal administration of plasmid DNA also showed gene expression
in mouse airways [20] . Administration of plasmid DNA encoding the chlorampheni-
col acetyltransferase gene (CAT) in sterile water has shown CAT transgene expres-
sion with 1 and 3 days peak expression and detectable up to 28 days after DNA
administration [20] . Zheng et al. [22] showed luciferase transgene expression with
6-12 h post-DNA instillation peak level and detectable up to 72 h. However, pro-
longed gene expression was achieved by repeated dosing [22] . Recently, significantly
improved naked DNA-mediated lung gene transfer via the use of nuclease inhibi-
tor aurintricarboxylic acid was also reported by Glasspool and Malone [23] . Due to
the excellent safety profile, free plasmid-based respiratory gene transfer may find its
applications in the treatment of a variety of pulmonary diseases [23] .
Systemic plasmid DNA injection has also shown a small amount of transgene
expression in all major organs. However, highest gene expression has been achieved
in the liver because of portal vein uptake of naked DNA by nonparenchymal, proba-
bly Kupffer cells, following interaction of DNA with scavenger receptors for polyan-
ions [24] . However, the intravascular injection of naked DNA under high hydrostatic
pressure with high injection volume leads to a high level of foreign gene expression
throughout all of the muscles of the targeted limb [25] and the liver [26] . These stud-
ies led to the development of the hydrodynamic method of gene delivery.
Recently, direct retrograde injection of naked plasmid into the renal vein in rats
has been shown to transfer the DNA efficiently into renal interstitial fibroblasts near
the peritubular capillaries (PTC) [27] . The plasmids inserted were mouse interleukin
( IL )- 10 gene using IL-10 and immunoglobulin fusion protein ( IL-10 /Fc) (96-kDa)
expression plasmid, pCAGGS- IL10 /Fc. A dose-response relationship between serum
IL-10 levels and the amount of injected DNA was observed, with transgene expres-
sion sustained up to 2 weeks [27] .
Gene delivery by plasmid injection was also explored in corneal tissue [28] .
Intrastromal injection was used to deliver naked DNA plasmids into the cornea for
gene expression in the corneal epithelium of mice [29,30] . The expression of pCMV-
Lac Z reporter gene for -gal protein was observed 1 h after the intrastromal injec-
tion, and the expression was observed for up to 10 days [29] . Rapid gene expression