Scientists uncover biological underpinnings of synthetic mesh failures

By Eva Martin, MD of Elm Tree Medical Inc.

How much time have you spent thinking about urinary incontinence? Chances are, if you are experiencing it, you’ve spent quite a lot of time considering your treatment options. After menopause, as many as 50% of women may experience urinary incontinence. Many women have turned to mesh implants that are inserted during a simple procedure. These synthetic mesh devices have been used to treat both urinary incontinence and pelvic organ prolapse, often with great results. Unfortunately, the implants were not without side effects. In 2008, the FDA issued a Public Health Notification warning of severe complications from these implantable meshes. Many women experienced “mesh erosion” in which the mesh wore through the vaginal lining, causing significant pain and often necessitating repeat surgeries. Scientists from the University of Pittsburg have now published new data on exactly how the body interacts with these implants.

In Microbiology 101, we all learned about our body’s response to substances that don’t belong: foreign bodies. Our immune system recognizes the foreign body (whether it’s vaginal mesh or a bone screw) and sends macrophages- the body’s soldiers- to respond. Scientists have further divided macrophages into two legions, M1 and M2. M1s cause chronic inflammation, potentially causing an unending onslaught of tissue damage and destruction. When they first arrive, M2s tend to help integrate the foreign body into tissue. However, if M2s stick around too long and are too active, they can create scarring.

Do women who experience complications after vaginal mesh placements have M1 or M2 responses? Scientists enrolled 27 women who were scheduled to have surgical removal of mesh into their study. The women had previously had the mesh placed to treat either prolapse or urinary incontinence. Fifteen of these women experienced mesh exposure (the mesh eroded through the vaginal wall), and 12 experienced pain without mesh exposure. The scientists also collected 30 biopsy samples from women without mesh, undergoing surgery for other reasons.

Were the destructive M1s or integrating M2s predominant? For the women with failed mesh, the M1 macrophages ruled. Compared to the biopsy samples without mesh exposure, both M1 and M2 macrophages were more common in the biopsy samples with mesh exposure.

The scientists found one notable difference between meshes removed for exposure versus those removed for pain. Mesh implants that eroded had 88% higher levels of a protein called pro-MMP-9 than those removed for pain. Pro-MMP-9 is part of the body’s demolition crew, breaking down tissue. This means that the mesh caused degradation of the vaginal tissue- for years after it was implanted.

What exactly should we take away from this mess of proteins? In women with complications, vaginal mesh causes an inflammatory response, triggering the actions of destruction cells and proteins. Most interestingly, this response persists for years. The women in the study were years out from the initial mesh placement, and yet these proteins were still wreaking havoc. The study is missing one element: samples from women with mesh and no complications. Perhaps some bodies don’t launch this massive inflammatory response and the mesh does its job without causing pain. We want to hear from you! Do you think this research spells the end for vaginal mesh implants? Would you try this treatment for urinary incontinence or prolapse?