Breast implants are increasingly being linked to health complications, with new research suggesting rougher materials could also trigger dangerous inflammation.
Implants in the UK tend to be made of silicone. Although these are less wrinkly and feel more natural than saline alternatives, silicone can spread to other parts of the breast, causing lumps.
Regardless of the material that is used, augmentation has been linked to so-called breast implant illness (BII). Although poorly understood, BII is thought to come about due to a patient's immune system triggering inflammation that can lead to insomnia, rashes and even hair loss.
Textured implants in particular have also been associated with a rare form of cancer known as breast implant-associated anaplastic large cell lymphoma (BIA-ALCL).
To better understand the potential side effects of implants, scientists from the Massachusetts Institute of Technology (MIT) analysed how different materials affected animals and the tissue of cancer patients.
Writing in the journal Nature Biomedical Engineering, the team found rougher implants – which help to prevent "slipping" – are linked to a higher number of inflammatory cells being released by the immune system.
These textures may irritate surrounding healthy tissue, potentially causing cancer in severe cases.
"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 co-lead author Dr Omid Veiseh, now at Rice University in Houston.
"We hope this paper provides a foundation for plastic surgeons to evaluate and better understand how implant choice can affect the patient experience."
In the 1960s, breast implants had a smooth surface. In some, this led to so-called capsular contracture, an uncomfortable condition where scar tissue forms around the implant, squeezing it. These implants could also flip after being inserted, requiring them to be surgically adjusted or removed.
Rougher implants were introduced in the late 1980s, in the hope the texture would better enable them to stay in place.
Highly textured implants – with "peaks" measuring around 0.08mm – were recalled in the US in 2019 due to a risk of BIA-ALCL, a cancer of the immune system.
The NHS warns "a very small number of people" continue to develop BIA-ALCL in the scar tissue around their implants. Although it is unclear, the implant's texture "may play a role".
So-called poly implant prostheses (PIP) implants were banned in the UK in 2010 after it was found they contained unapproved silicone gel and were more likely to split.
To combat these complications, more recently-rolled out implants tend to have a slight degree of roughness, with peaks of around 0.004mm.
To better understand the impact of an implant's texture, the MIT scientists tested five commercially available products – one that had been recalled, one that is completely smooth and three that fall somewhere in-between.
In rabbits, all the implants stimulated the release of immune cells called T cells, but in different ways. An overactive immune system can trigger inflammation that damages healthy tissue.
The rougher surfaces led to a more inflammatory T cell response, while a smoother texture – including the 0.004mm implant – led to the release of T cells that appeared to inhibit inflammation.
Rougher surfaces may rub against surrounding tissue, causing irritation. Rough material may then slough off into nearby tissue, leading to inflammation that eventually triggers cancer.
Miniaturised implants were also tested in mice. More highly-textured implants led to a higher degree of activity among macrophages, immune cells that remove foreign cells and debris. These implants were also linked to the formation of scar tissue and higher levels of inflammatory T cells.
"While completely smooth surface implants also had higher levels of macrophage response and fibrosis, it was very clear in mice that individual cells were more stressed and were expressing more of a pro-inflammatory phenotype in response to the highest surface roughness," said co-lead author Dr Joshua Doloff, now at Johns Hopkins University.
The 0.004mm implants were linked to reduced scarring and inflammation, compared to the rougher or completely smooth alternatives.
"We believe this is due to such surface architecture existing on the scale of individual cells of the body, allowing the cells to perceive them in a different way," said Dr Doloff.
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After the animal studies, the scientists analysed cancer tissue samples to determine how humans respond to different implant textures.
The results suggest similar types of immune responses occurred among the humans as the animals.
The tissue samples that were exposed to the highly textured implants for many years showed signs of a long-term immune response and thicker scar tissue.
"Doing across-the-board comparisons in mice, rabbits and then in human [tissue samples] really provides a much more robust and substantial body of evidence about how these compare to one another," said Dr Veiseh.
The scientists hope their results will lead to safer implants, made from both silicone and other medical materials.
"By demonstrating for the first time that an optimal surface architecture allows for the least possible inflammation and foreign-body response, this work is a significant contribution to the entire medical device industry," said co-author Roberto de Mezerville, from implant manufacturer Establishment Labs, which funded the study.
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