A collagen-based coil for embolization of saccular aneurysms in a New Zealand White rabbit model.
OBJECTIVE
In the treatment of cerebral aneurysms, platinum coils often fail to elicit a fibrotic response. We tested the hypothesis that a new, collagen-based endovascular coil would improve angiographic and histologic outcomes as compared with those achieved with platinum coils in a rabbit model of saccular aneurysms.


METHODS
Elastase-induced aneurysms were created in 12 New Zealand White rabbits (body weight, 3-4 kg). Embolization was performed either by use of collagen-based coils (n = 6) or platinum coils (n = 6). In both coil groups, subjects were kept alive for either 2 weeks (n = 3 [collagen], n = 3 [platinum]) or 10 weeks (n = 3 [collagen], n = 3 [platinum]) after embolization and then were sacrificed. Digital subtraction angiography (DSA) was performed immediately after embolization and immediately before sacrifice. Postmortem histologic analysis of all coils was performed.


RESULTS
Collagen-based coils were loosely packed in all cases because of limitations in size of coils available for embolization. In all six aneurysms packed with collagen-based coils, progressive thrombosis was noted at follow-up (DSA). Platinum coil samples were densely packed in all six cases. Progressive thrombosis was seen in one case, and interval regrowth was present in one case. Two weeks after embolization, collagen-based coil samples showed a marked peri-coil cellular response. Ten weeks after embolization, collagen-based samples had dense connective tissue matrix deposition in two of three cases. Platinum coils had unorganized thrombus at 2 weeks; loose-matrix deposition was only seen in the 10-week samples. Smooth muscle actin-positive cells were seen across the neck of the aneurysm in four of six collagen-based coil cases.


CONCLUSIONS
Collagen-based coils show a marked cellular response in animal-model aneurysms, with resultant high rates of progressive occlusion after embolization. Dense matrix deposition is commonly seen with collagen-based coils. This contrasts with low rates of progressive thrombosis and high rates of loose matrix deposition seen with platinum coils.
Kallmes
David F
DF
Department of Radiology, Mayo Clinic, Rochester, MN, USA.
Fujiwara
Naomi H
NH
Yuen
Debbie
D
Dai
Daying
D
Li
Shu-Tung
ST
D015901:Angiography, Digital Subtraction; D000818:Animals; D001672:Biocompatible Materials; D002533:Cerebral Angiography; D002536:Cerebral Arteries / Q000473:pathology; D003094:Collagen; D003238:Connective Tissue / Q000473:pathology; D004195:Disease Models, Animal; D004621:Embolization, Therapeutic / Q000295:instrumentation*; D002532:Intracranial Aneurysm / Q000473:pathology / Q000628:therapy*; D008422:Materials Testing; D019736:Prostheses and Implants; D011817:Rabbits; D013635:Tantalum; D014945:Wound Healing / Q000502:physiology
D001672:Biocompatible Materials; D013635:Tantalum; D003094:Collagen