4:02 PM Abstract No. 220 - Resorption and tissue reaction of bioresorbable microspheres for transcatheter embolization

Abstract

Purpose To evaluate the resorption and tissue reaction of bioresorbable microspheres in a renal embolization model. Materials and Methods 18 adult rabbits (New Zealand, 2.9-3.3 kg) were used in the study population. Under anesthesia, the renal artery was catheterized with a 4-F Cobra catheter. Bioresorbable hydrogel microspheres (300-500 μm), were delivered with a 2.4-F microcatheter (ID=570 μm, Terumo, NJ) slowly to the lower pole of right kidney at a flow rate of 1 mL/min until total occlusion was reached. At 3, 7, 10, 14, 21 and 30 days, three rabbits were sacrificed after new angiography to evaluate the recanalization. Coronal sections (4 μm in thickness) were obtained, and histological staining (HandE) was performed. Inflammation was evaluated by identifying infiltrate of inflammatory cells. The degradation of the microspheres was graded as follows: 0, A slight deformation without an obvious reduction in the particle size; 1, Moderately evident size reduction and distortion of the particle; 2, Clearly evident size reduction and distortion of the particle and the cleft or cavity formation; 3. No microspheres observed in the specimens. Results All the embolization procedures were successfully performed and all the animals survived without any complications. Moderate degradation of the microspheres (score 1) was observed as early as day 3. On day 10, and day 14, scant microsphere materials were identified in the arteries (Score 2). No microsphere was found on days 21 and 30 (Score 3). Vessel recanalization was observed by angiography after day 7. Inflammation associated with microspheres consisted of acute, heterophilic (polymorphonuclear) infiltrate at earlier time points (day 3 to day 10, however it was resolved with the resorption of the microspheres by day 21. Inflammation and fibrosis within infarcted regions was consistent with progression of infarction. Conclusion The study confirmed that microspheres were bioreosorbable and the majority of the microspheres were resorbed before day 10. The overall tissue reaction was mild. Vessel recanalization occurred due to the resorption of the microspheres.