Surface microarchitectural design in biomedical applications: In vivo analysis of tissue ingrowth in excimer laser-directed micropored scaffold for cardiovascular tissue engineering

A micropatterned microporous segmented polyurethane film (20 x 12 mm in siz e, 30 mu m thick) with four regions was prepared by excimer laser microproc essing to provide an in vivo model of transmural tissue ingrowth in an open cell-structured scaffold specially designed for cardiovascular tissue engi neering. Three microporous regions had the same circular micropores (30 mu m diameter) but different pore density arrangements (percentage of total po re area against unit area was 0.3%, 1.1%, and 4.5%), and the other region r emained nonporous. The covered stent, prepared by wrapping the regionally d ifferent density-microporous film on an expandable metallic stent (approxim ately 3.1 mm in diameter), was delivered to the luminal surface of canine c ommon carotid arteries and placed after expansion of the stent to a diamete r of approximately 8 mm using a balloon catheter. At 4 weeks of implantatio n, all the covered stents (n = 10) were patent. The luminal surfaces of the covered stents were almost confluently endothelialized both in nonporous a nd microporous regions. Histological examination showed that the neointimal wall was formed by tissue ingrowth from host through micropores (transmura l) and anastomotic sites. Thrombus formation occurred frequently in the low est density porous region and nonporous region. With an increase in pore de nsity, the thickness of the neointimal wall decreased. This study demonstra ted how the micropore density of implanted devices influences tissue ingrow th in arterial implantation. (C) 2000 John Wiley a Sons, Inc.