Transforming growth factor beta-coated platinum coils for endovascular treatment of aneurysms: An animal study

Objective: To test the hypothesis that coating platinum coils with transfor ming growth factor beta (TGF beta) would improve the cellular proliferation within experimental aneurysms relative to uncoated coils. Materials and methods: Elastase-induced saccular aneurysms were created in 12 New Zealand White rabbits. These aneurysms were embolized with platinum coils, either "control" (unmodified) coils or "test" (coated with TGF beta) coils. Subjects were killed either 2 weeks (n = 3, control; n = 3, test) o r 6 weeks (n = 3, control; n = 3, test) after embolization. Aneurysm tissue was embedded in plastic, sectioned, and stained with hematoxylin and eosin . The thickness of tissue covering the coils at the coil-lumen interface wa s measured by use of a digital microscope, and was compared between groups by use of the Student's t test (P less than or equal to 0.05). Results: Two-week implantation samples demonstrated mean thickness of tissu e overlying TGF beta -coated coils of 36 +/- 15 mum and mean thickness of o verlying control coils of 3 +/-5 mum, indicating significantly thicker tiss ue growth covering test versus control coils (P = 0.02). Six-week implantat ion samples demonstrated mean thickness of tissue overlying TGF beta -coate d coils of 86 +/- 74 mum versus mean thickness overlying control coils of 3 7 +/-6 mu; this difference did not reach statistical significance (P = 0.30 ). Thickness of tissue covering TGF beta -coated coils did not change signi ficantly from 2 to 6 weeks (P = 0.31). Tissue thickness over control coils increased significantly between 2 and 6 weeks (P = 0.002). Conclusion: TGF beta -coated platinum coils undergo earlier cellular covera ge than standard platinum coils, but differences in coverage between coated and control coils are no longer present at later time points. These data s uggest that improvements in intra-aneurysmal cellular proliferation resulti ng from coil modifications, although significant in the early postembolizat ion phase, may dissipate over time.