A Clinician–Engineer Approach to Improving Surgical Mesh
I recently had the opportunity to speak with Dr. Pamela A. Moalli MD, PhD and Dr. Steven Abramowitch, PhD. Dr. Moalli is the director of the Division of Urogynecology and Reconstructive Pelvic Surgery and a Professor of Obstetrics and Gynecology in the Division of Urogynecology and Reconstructive Pelvic Surgery at UPMC. Dr. Abramowitch is a Professor of Bioengineering at the University of Pittsburgh’s Swanson School of Engineering. With support from the Center for Medical Innovation (CMI), they combined their expertise to develop an auxetic mesh to treat pelvic organ prolapse. This work became more urgent after the FDA ordered the removal of surgical mesh products for transvaginal repair of pelvic organ prolapse (POP) from the U.S. market in April 2019. Manufacturers failed to demonstrate reasonable safety and long-term effectiveness compared to traditional, non-mesh repairs. Surgical repair is the only current option but carries significant risks for patients.
Pelvic organ prolapse occurs when the pelvic floor muscles and tissues become weak, and the pelvic organs drop, causing a bulge (prolapse) in the vagina. One of the most effective surgeries involves rebuilding the connective tissue or ligament support using polypropylene mesh. Around 2006, Dr. Moalli began noticing that patients were experiencing complications following these procedures. When the meshes were removed during revision surgeries, they were visibly deformed. This realization prompted Dr. Moalli and Dr. Abramowitch to investigate the mechanics of mesh behavior in the body.
Their initial research focused on understanding why this deformation was occurring, so they researched the market traits of a ‘good’ mesh. At the time, strength was heavily marketed as the most important metric. However, Dr. Abramowitch realized this did not make sense from a mechanical point of view because the meshes were not failing from being in a body. Instead, the critical issue was how the mesh deformed after forces were applied. This work led to their publication on the basic mechanics of surgical meshes. This research explains that polypropylene mesh is more than three orders of magnitude stiffer than the vagina. This mismatch resulted in stress shielding, micromotion, permanent deformation, and pore collapse, a phenomenon identified through computational modeling and experimental testing led by Katrina Knight, PhD.
From this research, they knew their device needed to be as soft as the vagina, have an elastic (return to normal after deformation) behavior, and have stable pores. This led to the idea of using an auxetic mesh structure. This means that when the material is stretched, it gets wider in the center. Therefore, instead of the pores collapsing under load, they would open and get bigger. This reduced the amount of material in contact with the host tissue and promoted better biological integration.
CMI funding helped to translate this concept into a viable technology with commercial application. The CMI seed grant provided the support needed to test feasibility, perform early simulations, and fabricate initial auxetic prototypes using emerging 3D printing techniques. This early work generated the preliminary data required to pursue larger external funding. Following CMI support, the team secured Department of Defense funding and multiple NIH R01 grants exceeding $2.5M, allowing them to conduct ex vivo and in vivo testing. In large-animal studies, the auxetic mesh demonstrated reduced inflammatory responses and eliminated pathologic cell types associated with tissue stress compared to traditional polypropylene mesh.
CMI also supported the training and advancement of students. Katrina Knight, who led much of the early computational modeling and mechanical analysis during the CMI phase, continued working on the project through her doctoral and postdoctoral training and is now a faculty member advancing this line of research independently.
Today, the team is expanding the technology by functionalizing the auxetic mesh with bioactive peptides to promote tissue integration. CMI funding facilitated the translation of a high-risk concept into a sustained, federally funded research program with significant clinical promise.
- Jana Citrenbaum