Periluminal Expression of a Secreted Transforming Growth Factor-β Type II Receptor Inhibits In-Stent Neointima Formation Following Adenovirus-Mediated Stent-Based Intracoronary Gene Transfer

Abstract

Transforming growth factor-β1 (TGF-β1) has been shown unequivocally to enhance neointima formation in carotid and ileo-femoral arteries. In our previous studies, however, TGF-β1 expression in coronary arteries actually reduced neointima formation without affecting luminal loss postangioplasty, while expression of a TGF-β1 antagonist (RIIs) in balloon-injured coronary arteries reduced luminal loss without affecting neointima formation. These observed effects may be a consequence of the mode of coronary artery gene transfer employed, but they may also represent differences in the modes of healing of coronary, carotid, and ileo-femoral arteries after endoluminal injury. To help clarify whether a gene therapy strategy to antagonize TGF-β might have application within the coronary vasculature, we have investigated the effect of high-level periluminal expression of RIIs using stent-based adenovirus-mediated intracoronary gene transfer. Porcine coronary arteries were randomized to receive a custom-made CoverStent preloaded with saline only, or with 1×10⁹ infectious units of adenovirus expressing RIIs or β-galactosidase (lacZ). Vessels were analyzed 28 days poststenting, at which time angiographic in-stent diameter was significantly greater in RIIs-treated arteries, and in-stent luminal loss significantly reduced. Computerized morphometric minimum in-stent lumen area was ∼300% greater in RIIs-exposed vessels than in lacZ or saline-only groups. This was because of significantly reduced neointima formation in the RIIs group. RIIs had no demonstrable effect on cellular proliferation or apoptosis, but greater normalized neointimal/medial collagen content was observed in RIIs-exposed arteries. These data highlight the qualitatively similar effect of TGF-β antagonism on neointima formation in injured coronary and noncoronary arteries, and suggest that since cellular proliferation is unaffected, TGF-β1 antagonism might prevent in-stent restenosis without the delayed healing that is associated with drug-eluting stents in current clinical use.