Textured silicone breast implants, generally believed safe, can result in immune-related complications, including cancer. Every year, about 400,000 people in the United States receive silicone breast implants, and according to the FDA, most of these implants need to be replaced within a decade due to the buildup of scar tissue and other complications.
Silicone breast implants have been in use since the 1960s. Earlier implants had smooth surfaces, but caused a complication called capsular contracture where scar tissue formed around the implant creating pain and deformities. Textured implants introduced in the 1980s have, however, resulted in Breast Implant Associated Anaplastic Large Cell Lymphoma (BIA-ALCL) that led its manufacturer, Allergan, to recall the implants in 2019 at the FDA’s request.
Scientists at the Massachusetts Institute of Technology, Rice University, University of Texas, MD Anderson Cancer Center, and Baylor College of Medicine, have now shown that the surface architecture, specifically the roughness of silicone breast implants is responsible for the immune response to the implants. The authors also showed that the tissue surrounding human breast implants changes the individual’s immune response to the implant. Their findings indicate implants with a mean roughness of 4microns provoke the least inflammation and the buildup of fibroid scar tissue.
The study is published in the Nature Biomedical Engineering, “The surface topography of silicone breast implants mediates the foreign body response in mice, rabbits and humans,” and was funded by Establishment Labs.
“The surface topography of an implant can drastically affect how the immune response perceives it, and this has important ramifications for the [implants’] design,” said Omid Veiseh, PhD, assistant professor of bioengineering at Rice who began the research six years ago during a postdoctoral fellowship at MIT. “We hope this paper provides a foundation for plastic surgeons to evaluate and better understand how implant choice can affect the patient experience.”
As part of the study, the researchers placed miniature clinically-approved implants with different degrees of roughness into the mammary fat pads in mice or full-scale ones in rabbits and monitored the body’s immune response and the generation of fibroid tissue around the implant for up to one year.
Their results showed miniature implants with a mean roughness of 4 microns can suppress the immune response and fibrosis in normal mice but not in mice deficient in immune T cells. They also showed higher levels of immunosuppressive, FOXP3 expressing, regulatory T cells in tissue immediately surrounding these implants.
“The results show that the lightly textured surface avoided the strong negative cytokine immune response induced by the rough surface,” said H. Courtney Hodges, PhD, assistant professor of molecular and cellular biology at Baylor and an author on the study.
The researchers followed up the animal studies by examining how human patients responded to different types of silicone breast implants by collaborating with MD Anderson on the analysis of tissue samples from BIA-ALCL patients. They noted similar immune responses in humans as in animal studies. Patients with highly textured implants for many years showed signs of a chronic, long-term immune response and thick scar tissue.
The authors hope their data will help other researchers optimize the design of silicone breast implants and other types of medical silicone implants for better safety.
“We are pleased that we were able to bring new materials science approaches to better understand issues of biocompatibility in the area of breast implants,” said Robert Langer, PhD, the study’s senior author and MIT’s David H. Koch Institute professor. “We also hope the studies that we conducted will be broadly useful in understanding how to design safer and more effective implants of any type.”