Blockade of TGF-β by catheter-based local intravascular gene delivery does not alter the in-stent neointimal response, but enhances inflammation in pig coronary arteries

Background: Extracellular matrix (ECM) accumulation significantly contributes to in-stent restenosis. In this regard, transforming growth factor (TGF)-β, a positive regulator of ECM deposition, may be implicated in in-stent restenosis. The goal of this study was to assess the effect of blockade of TGF-β on stent-induced restenosis in porcine coronary arteries. Methods: An adenovirus expressing the ectodomain of the TGF-β type II receptor (AdTβ-ExR) was applied onto a coronary arterial segment of a pig (n = 10) using an Infiltrator^TM, followed by stent deployment. Controls consisted of adenoviruses expressing β-galactosidase (AdLacZ) or phosphate-buffered saline (PBS) applied onto the other segment (n = 10) of the same pig. Results: Computer-based pathological morphometric analysis of stented coronary arteries, performed 4 weeks after stenting, demonstrated no significant difference in morphometric parameters such as in-stent neointimal area and % area stenosis between the AdTβ-ExR group and control (n = 7 for each). However the AdTβ-ExR group had increased neointimal cell density, infiltration of inflammatory cells mostly consisting of CD3⁺ T cell, accumulation of hyaluronan, cell proliferation rate, and adventitial matrix metalloproteinase-1 (MMP-1) expression compared with control. The expression of connective tissue growth factor mRNA, measured by reverse transcription PCR, in cultured rat arterial smooth muscle cells was inhibited by AdTβ-ExR at moi 60. Conclusions: Blockade of TGF-β by catheter-based local intravascular gene delivery does not reduce stent-induced neointima formation 4 weeks after stenting in spite of modest inhibition of ECM accumulation, but it induces vascular inflammation and associated pathological changes that may potentially aggravate lesion progression.