Characteristics and efficacy of fish-derived gelatin microparticles as an embolic agent in a rabbit renal model: regulation of the degradation period by molecular weight

PURPOSE We aimed to evaluate the embolic effect of fish-derived gelatin microparticles (GMPs) and compare the degradation periods and biocompatibilities of different molecular weight (MW) GMPs in a rabbit model. METHODS GMPs were designed to degrade within 21 days (high MW GMP, 15-30 kDa) and 2 days (low MW GMP, 5-15 kDa) in vivo. Renal arteries of 24 rabbits were embolized using both high and low MW GMPs (155-350 mu m). Rabbits were sacrificed either immediately after embolization, or after follow-up angiogram on days 2 and 21 of embolization, respectively (4 rabbits in each of the 6 subgroups). Pathological changes of recanalized vessels were evaluated using the Banff classification. For the in vitro study, each type of GMP was mixed with normal saline and morphological changes were compared for 14 days. RESULTS Fish-derived GMPs showed effective embolization. On 2-day follow-up angiography, occluded vessels were more recanalized to the peripheral branches in low MW group. On day 21, parenchymal perfusion defect recovered to a greater extent in low MW group than in high MW group. Mean Banff scores for intimal arteritis on 2-day follow-up and interstitial fibrosis on 21-day follow-up were higher in high MW group (1.75 +/- 0.58 vs. 0.19 +/- 0.4 and 2.56 +/- 0.63 vs. 0.88 +/- 0.89; P <.001). On in vitro assessment, low MW GMP lost the spherical shape and degraded, and was invisible on microscopy on day 6, whereas high MW GMP was only partially degraded after 2 weeks. CONCLUSION Fish-derived GMPs showed effective embolization in a rabbit model. Low MW GMPs degraded within 2 days with a low inflammatory response.