Comparison of histopathological characteristics of polyacrylate polyalcohol copolymer with dextranomer/hyaluronic acid after injection beneath the bladder mucosa layer: a rabbit model.

OBJECTIVES: To compare short- and long-term local tissue reaction of polyacrylate polyalcohol copolymer (PPC) with dextranomer/hyaluronic acid (DHA) in rabbits.

METHODS: Eight healthy New Zealand rabbits were randomly divided into two groups. In group I (control group), DHA was injected just beneath the mucosal layer of the bladder wall, while PPC was injected in group II. Subcutaneous injection of both bulking agents was also performed in nude mice. Histological evaluations with leukocyte common antibody (LCA), CD68, CD31, and CD34 were conducted on biopsies 1 and 6 months postoperatively. Scanning electron microscopy (SEM) and MTT assay were also performed for these two bulking agents.

RESULTS: SEM images revealed larger particle size of PPC. LCA and CD68 staining was significantly higher in group II as compared with group I in both short- and long-term follow-ups. However, in groups I and II, expression of CD31 (101 ± 0.5 vs. 92 ± 0.25, p > 0.05) and CD34 (115 ± 0.75 vs. 103 ± 0.5, p > 0.05) was not significantly different in long-term follow-up. Remarkably, severe fibrosis was observed in group II as compared to mild fibrosis in group I one month after injection. The results of in vivo application of these bulking agents in nude mice were in accordance with the results obtained from rabbit model. MTT assay revealed that cell proliferation was significantly higher in the presence of DHA as compared with PPC.

CONCLUSION: Severe inflammation and fibrosis in PPC may be due to continued foreign body reaction, presence of alcohol polymers, or larger particle sizes.