Novel MR-Visible, Biodegradable Microspheres for Transcatheter Arterial Embolization: Experimental Study in a Rabbit Renal Model

Purpose

: To assess feasibility, embolization success, biodegradability, reperfusion, biocompatibility and in vivo visibility of novel temporary microspheres (MS) for transcatheter arterial embolization.

Material and Methods

: In 9 New Zealand white rabbits unilateral superselective embolization of the lower kidney pole was performed with biodegradable MS made of polydioxanone (PDO) (size range 90–300 and 200–500 µm) impregnated with super-paramagnetic iron oxide (SPIO). Magnetic resonance imaging (MRI) was performed post-interventionally to assess in vivo visibility. Embolization success was assessed on digital subtraction angiography, MRI and gross pathology. One animal was killed immediately after embolization to assess original particle appearance. 8 animals were randomly assigned to different observation periods (1, 4, 8, 12 and 16 weeks), after which control angiography and MRI were obtained to determine recanalization. Histopathological analysis was performed to determine biodegradability and biocompatibility by using dedicated quantitative assessment analysis.

Results

: Ease of injection was moderate. Embolization was technically successful in 7 of 8 animals, one rabbit received non-selective embolization of the whole kidney and abdominal off-target embolization. Arterial occlusion was achieved in all kidneys, infarct areas in macro- and microscopic analysis confirmed embolization success. Control angiograms showed evidence of partial reperfusion. The microspheres showed extensive degradation over the course of time along with increasing inflammatory response and giant cell formation. SPIO-loaded MS were visible on MRI at all time points.

Conclusions

: SPIO-impregnated biodegradable PDO-MS achieved effective embolization with in vivo visibility on MRI and increasing biodegradation over time while demonstrating good biocompatibility, i.e., a physiologically immune response without transformation into chronic inflammation. Further studies are needed to provide clinical applicability.