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Urethral bulking with polymethylmethacrylate microspheres for stress urinary incontinence: tissue persistence and
Gottfried Lemperle1, Patrick B Lappin, Corbett Stone
1Surgical Animal Laboratory, University of California, San Diego, CA 92037, USA. glemperle@aol.com
Objectives:
To evaluate the safety and persistence of injectable polymethylmethacrylate (PMMA) microspheres as a long-lasting urethral bulking agent in pigs. PMMA microspheres of 2 different diameters (40 and 125 μm) were tested to investigate the potential for migration and dislocation after injection. A similar product containing 40-μm PMMA microspheres has been used as an injectable wrinkle filler for >25 years and received Food and Drug Administration approval in 2006 (ArteFill).
Methods:
A total of 22 female pigs received 4 submucosal implantations of PMMA microspheres, using either a cystoscope or a newly developed urethral injection device (UroScope). At death and necropsy at 8 days and 1, 3, and 6 months, the urethral injection site, liver, lung, spleen, and pelvic and iliac lymph nodes were processed for histologic examination and microsphere count using organ dissolution and microscopy.
Results:
All injected submucosal blebs were still present at 6 months and showed no signs of inflammation. Tissue dissolution of the local lymph nodes and major organs demonstrated the transport of some of the 40-μm microspheres to the local lymph nodes and lung but not to the liver or spleen. In contrast, no 125-μm microspheres were detected in any distant organ.
Conclusions:
The submucosal implantation of 125-μm PMMA microspheres into the urethra provided a safe and persistent bulking effect in pigs. The positive results of the present study encourage additional investigation of 125-μm PMMA microspheres as a long-lasting bulking agent for the treatment of female stress urinary incontinence. Furthermore, a newly developed urethral injection device (UroScope) proved beneficial and cost-effective to facilitate the transurethral injections of 125-μm PMMA microspheres.
Insights
Injectable polymethylmethacrylate (PMMA) microspheres are safe and persistent urethral bulking agents in pigs. Larger 125-μm PMMA microspheres showed no distant migration, supporting their use for stress urinary incontinence.
Area of Science:
- Urology
- Biomaterials Science
- Surgical Innovation
Background:
- Injectable bulking agents are used to treat stress urinary incontinence.
- Polymethylmethacrylate (PMMA) microspheres are FDA-approved for cosmetic use and have a long safety record.
- Investigating PMMA microspheres for urethral bulking requires evaluation of safety, persistence, and potential migration.
Purpose of the Study:
- To assess the safety and persistence of injectable PMMA microspheres as a long-lasting urethral bulking agent in a porcine model.
- To compare the migration potential of 40-μm and 125-μm PMMA microspheres after urethral injection.
- To evaluate a novel urethral injection device for PMMA microsphere delivery.
Main Methods:
- Submucosal implantation of PMMA microspheres (40 and 125 μm) into the urethra of 22 female pigs using a cystoscope or the UroScope device.
- Histologic examination and microsphere counting in the urethral injection site, local lymph nodes, liver, lung, and spleen at 8 days and 1, 3, and 6 months post-injection.
- Organ dissolution and microscopy were used for microsphere quantification.
Main Results:
- Injected PMMA microsphere blebs remained present and showed no inflammation at 6 months.
- Some 40-μm PMMA microspheres migrated to local lymph nodes and lungs, but not to the liver or spleen.
- No 125-μm PMMA microspheres were detected in any distant organs, indicating minimal migration.
Conclusions:
- Submucosal implantation of 125-μm PMMA microspheres is safe and provides a persistent bulking effect in the porcine urethra.
- 125-μm PMMA microspheres show promise as a long-lasting bulking agent for female stress urinary incontinence.
- The UroScope device is an effective and cost-efficient tool for transurethral PMMA microsphere injections.
