C-Type Natriuretic Peptide Inhibits Constrictive Remodeling Without Compromising Re-Endothelialization in Balloon-Dilated Renal Arteries

Abstract

To investigate the long-term effect of local, liposome-mediated gene transfer of C-type natriuretic peptide (CNP) plasmid versus CNP protein on restenosis in porcine renal arteries following balloon angioplasty. The renal arteries of 15 pigs were dilated and the adventitia at the site of balloon injury injected with CNP protein, pCR3.1 plasmid encoding CNP, or the beta-galactosidase gene (control) via a needle injection catheter. Five animals receiving the CNP and control genes in dilated arteries were sacrificed after 3 weeks to analyze re-endothelialization, proliferation, and early CNP expression. Ten animals designated for the long-term experiments (3 months) were treated with the CNP gene versus CNP protein (n=3), the CNP gene versus the control gene (n=3), and the CNP protein versus the control gene (n=3). One animal served as a dilated non-treated control. Transfection and expression of CNP and beta-galactosidase were measured by polymerase chain reaction (PCR) and reverse transcription PCR. Renal arterial lumen narrowing was measured with angiography and histology. Endothelialization was assessed using Evans blue stain; vWF, CD31, factor VIII, and Ki67 were markers for immunohistochemical analysis. An intact endothelial layer was seen at 3 weeks following angioplasty in all transfected arteries. Three months following treatment, computer-assisted morphometric analysis revealed significant enlargement of the arterial cross-sectional areas in CNP plasmid- treated vessels compared to dilated but untreated arteries (CNP plasmid +34.8%+/-13.9% versus CNP protein -1.75%+/-19.9% versus beta-galactosidase -47.0%+/-13.9%, p<0.01). Angiographic analysis showed significant enlargement of the arterial diameter compared to dilated, untreated arteries (CNP plasmid +20.8%+/-6.8% versus CNP protein +5.7%+/-6.0% versus beta-galactosidase -24.5%+/-10.2%, p<0.01). Local application of CNP plasmid proved superior to CNP protein in producing rapid re-endothelialization and significantly enlarging the renal arterial lumen following dilation.