INNOVATION
A novel biocompatible material that mimics pelvic floor tissues to provide a safer treatment for stress urinary incontinence in women.
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RESEARCH & DEVELOPMENT TO DATE
Polypropylene meshes have been used for more than 20 years to assist surgeons in repairing tears in the muscles of the abdomen. These meshes are strong but not very flexible. Following their success in abdominal muscle repair, they were then introduced into the female pelvic floor to assist surgeons in treating women with stress urinary incontinence. Unfortunately, when used in the pelvic floor, the polypropylene meshes caused problems for some patients, including persistent inflammation, pain and even erosion of the mesh through the patient's tissues.
An alternative approach to treating stress urinary incontinence is to use a patient’s natural tissue, fascia, which is the connective tissue surrounding muscles. Surgeons have used this fascia tissue to support the urethra to reduce the symptoms of urinary incontinence. This works well with a very low complication rate, although it is a more challenging surgery and not appropriate for all women suffering from stress incontinence.
Our approach is to mimic the mechanical properties of native tissue using a medical-grade polymer that responds well to repeated distension without any loss of mechanical properties. The resulting material employs a tailored fibre architecture that is inspired by, and behaves similarly to, the native collagen fibres in a patient’s fascia.
Initial validation of this approach was performed by subjecting both our material and conventional polypropylene meshes to rapid and repeated distension over three days in a bioreactor. The mechanical properties of both materials were measured before and after the tests. Whilst the polypropylene mesh was shown to deform irreversibly within three days, our material did not exhibit any deterioration in performance.
Our material was then implanted in animals to test tissue integration and the immune response to the material. We looked at the acute inflammatory response when the material was implanted in the abdominal wall of rats for 7 days and of rabbits for 3 months. Then we looked at the inflammatory response and tissue integration when it was implanted into the vagina of sheep for 6 months. These experiments confirmed that there was an acute inflammatory response to the material which calmed down quickly and that there was good tissue integration into our material. This contrasted with the sheep response to polypropylene mesh, which a previous study had shown caused sustained inflammation with more than 50% contraction of the material in the vagina and erosion of the material through the tissues of some of the sheep.
Our recent studies have sought to investigate why the response to polypropylene leads to sustained inflammation and fibrosis in patients. Using a very sensitive surface analysis technique we have shown that polypropylene mesh subjected to just a few days of repeated distension shows early-stage formation of fine cracks in the surface of the mesh. Our ongoing work shows this is sufficient to lead to the expression of pro-inflammatory and pro-fibrotic genes in macrophages. These activated macrophages lead to further surface damage to the polypropylene mesh. Thus, in addition to our materials, we are also developing an analytical tool kit to look at the combined effect of mechanical distension and cells of the immune system on the integrity of these materials.
ONGOING DEVELOPMENT
Our ongoing work is currently focussed on demonstrating reliable, quality assured upscaled production of the material. We are also developing designs for improving approaches to the insertion, adjustment and fixing of such devices.
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