Vascular implantation: new therapeutic approach

Granulation encapsulated stent: a new therapeutic approach for vascular implantation

Lilong Tang1, Xiaochao Chen1, Shuangbo Tang3, Thomas LaLonde2 and Julius M Gardin2
1) Division of Cardiology, The Fifth Affiliated Hospital to Sun Yat-Sen University, Zhuhai, Guangdong, China
2) Division of Cardiology, St. John Hospital and Medical Center, Detroit, MI, USA
3) Division of Forensic Pathology, Preclinical School of Sun Yat-Sen, Guangzhou, Guangdong, China

Objectives: To determine if stents could be encapsulated with immunocompatible granulation tissue for the treatment of vascular diseases.
Methods: Bare metal stents were implanted in New Zealand white rabbits so they would be encapsulated with immunocompatible granulation tissue. The granulation encapsulated stents (GES) were then treated with either mitomycin C or saline, and implanted into rabbit iliac arteries for 4 weeks. To test whether the effect of mitomycin C was retained, we co-cultured smooth muscle cells for 3 h with subcutaneous tissue (as control) or with granulation tissue from GES treated with mitomycin C and saline.
Results: Vessels with GES treated with mitomycin C (MS) and washed with saline had significantly less neointimal area (NA) after 4 weeks (0.27 (SD 0.03) mm2 than vessels containing bare metal stents (B) (1.15 (SD 0.10) mm2, n = 5, p<0.05) or GES treated with saline (S) (4.78 (SD 0.72) mm2, n = 5, p<0.05). The average vessel injury score was not significantly different among these three groups (S: 1.98 (SD 0.51), MS: 1.46 (SD 0.18) and B: 1.51 (SD 0.32)). GES treated with saline had significantly less NA than the other two groups and also blocked blood flow in the contralateral iliac artery in the abdominal aortic bifurcation immediately after implantation and 4 weeks later. Histology also showed neointimal overgrowth in the vessel wall over the contralateral iliac artery.
Conclusions: GES treated with mitomycin C can significantly inhibit neointimal formation in rabbit arteries due to the formation of granulation tissue. GES treated with saline demonstrated significantly increased NA and resisted normal rabbit artery pressures.
Abbreviations: DMEM, Dulbecco’s modified Eagle’s medium; EIA, external iliac artery; GES, granulation encapsulated stent; GT, granulation tissue; NA, neointimal area; VIS, vessel injury scores; VSMC, vascular smooth muscle cells
Keywords: aneurysm; granulation tissue; restenosis; stent

Heart 2007;93:238-243
© 2007 by BMJ Publishing Group Ltd & British Cardiovascular Society