Endoscopic injection of bulking agents has been gaining attention as a therapy for urinary incontinence and vesicoureteral reflux because this therapy is simpler, less operation time-consuming and less painful than traditional surgical operations. The ideal bulking agent for the injection
therapies must be easily injectable, biocompatible, volume-stable, non-antigenic and non-migratory. We evaluated poly(lactic-co-glycolic acid) (PLGA) microspheres as an injectable bulking agent for urologic injection therapies. To determine whether PLGA microspheres meet the requirements of
an ideal bulking agent, PLGA microspheres were injected into the submucosal sites of a rabbit bladder wall. The microspheres were easily injectable. Two and five weeks post-implantation, histological examinations indicated that host cells from the surrounding bladder tissues migrated to the
space between the injected microspheres and formed new hybrid tissue structures. Lymphocyte migration was noted around the implanted microspheres, but the inflammatory reaction diminished at 5 weeks. The hybrid tissue volume did not significantly decrease over time. There was no evidence of
microsphere migration to the distant organs. Although long-term studies are needed to evaluate the therapeutic potential of this method, these preliminary results suggest the possibility of PLGA microspheres as a potentially useful injection material for urinary injection therapies.