Healing of experimental aneurysms. II: Platelet extracts can increase the thickness of the neointima at the neck of treated aneurysms.

Purpose: To assess the effect of platelet extracts (PE) on neointima formation following gelfoam packing of experimental porcine aneurysms. A strategy involving the local delivery of platelet growth factors may potentially improve long term results of endovascular treatment of aneurysms.

Methods: Bilateral lateral wall common carotid aneurysms were constructed on 30 pigs. A collagen sponge containing a PE rich in growth factors was used to pack one aneurysm with the controlateral lesion being embolized with a sponge containing NaCl 0.9% (22 animals). In 8 animals, a control sponge was used on both sides. Animals were sacrificed at 1, 2, 3, 4 and 9 weeks and the thickness of the neointima covering the neck of PE-treated aneurysms was measured in 5 locations for each lesion at 2 and 3 weeks and compared with the control aneurysm of the same animal. Morphometric data was analysed using the paired Student's t-test.

Results: The thickness of the neointima was significantly increased in lesions treated with PE as compared to control lesions at 2 weeks (p = 0.008, n = 9). There was no significant difference at 3 weeks (p = 0.99, n = 9). There was no significant difference between lesions of control animals (p = 0.95, n = 8).

Conclusion: PE rich in growth factors can increase the thickness of the neointima at the neck of treated experimental porcine aneurysms at 2 weeks, but had no effect at 3 weeks. This accelerated neointimal formation may have some value in improving healing following endovascular treatment. This hypothesis could not be supported with this experimental model which has a spontaneous tendency to heal. Further studies using an animal model which reproduces the clinical problem of recurrences may help to define the role of the local delivery of growth factors in combination with coils in a strategy designed to improve results of endovascular treatment.