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Researchers at Baylor College of Medicine used a 3D bioprinter to create a biomesh using a polymer called phosphate-crosslinked polyvinyl alcohol polymer (X-PVA) for an innovative new treatment for hernias. The full study was published in Advanced Materials.
The hernia is one of the most common soft tissue injuries that occurs when intra-abdominal contents, such as a bowel loop, are squeezed through weak, broken, or injured areas of the abdominal wall. The condition can develop serious complications, so hernia repair may be recommended. The repair consists of the surgical implantation of a prosthetic mesh to support and strengthen the damaged abdominal wall and facilitate the healing process. However, mesh implants currently in use are associated with potentially deleterious post-operative complications.
Through thorough experiments, the researchers optimized the mechanical properties so that the mesh withstands the maximum abdominal pressure repeatedly for several months without its mechanical strength deteriorating. They also showed that their Biomesh did not deteriorate or decrease its elastic properties over time and was not toxic to human cells.
“Although hernia mesh implants are mechanically strong and support the abdominal tissue, which makes the patient comfortable at first, a common problem is that the implant can trigger inflammation around three days after surgery, which can affect nearby organs in two to three weeks “said Dr. Crystal Shin, Assistant Professor of Surgery at Baylor College of Medicine and lead author on this study seeking a solution to postoperative hernia complications. “To address these complications, we developed a non-pharmacological approach by designing a novel mesh that, in addition to providing mechanical support to the injury site, also acts as an inflammation-modulating system. A major innovation in our design is the development of a biomesh that can reduce inflammation and, as a result, minimize tissue adhesion to the mesh, resulting in pain and surgery failure. “
Mesh implants usually fail because they promote adhesion of the intestine, liver, or other visceral organs to the mesh. As the adhesions grow, the mesh shrinks and hardens, potentially leading to chronic pain, intestinal obstruction, bleeding, and poor quality of life. Some patients may need a second operation to repair the unsuccessful first one. “Inflammation is also a serious problem,” said Dr. Ghanashyam Acharya, Associate Professor of Surgery in Baylor. “Currently inflammation is controlled with drugs or anti-inflammatory drugs, but these drugs also interfere with the healing process by blocking immune cells from migrating to the injury site.”
Inflammatory mediators called cytokines occur where the mesh is implanted a few days after the operation. Some of the major cytokines in the implant, IL1-β, IL6 and TNF-α, have a positive surface charge due to the presence of the amino acids lysine and arginine.
“We hypothesized that Biomesh with a negative surface charge would capture the positively charged cytokines because opposing electrical charges are attracted to each other,” Acharya said. “We expected that trapping the cytokines in the web would reduce their inflammatory effects and improve hernia repair and healing.”
Shin, Acharya and their colleagues have confirmed in the laboratory that this biomesh can capture positively charged cytokines. Encouraged by these results, the researchers tested their Biomesh in a rat model of hernia repair and compared it to a type of mesh that is commonly used clinically for surgical hernia repair.
The newly developed Biomesh effectively minimized the postoperative complications of hernia repair in an animal model. The researchers examined the biomesh four weeks after implantation and found that it had captured about three times the amount of cytokines that were captured by the commonly used mesh. Cytokines are short lived in the body. As they break down, they allow the web to capture more cytokines.
“This biomesh is unique and is designed to improve outcomes and reduce acute and long-term complications and symptoms associated with hernia repair. With more than 400,000 hernia repair surgeries performed in the US each year, the new Biomesh would meet a huge unmet need, ”Shin said. “There is no such thing as a multifunctional surgical mesh, and the development of a broadly applicable biomesh would be a major step forward in the surgical repair of hernias and other soft tissue defects. We are conducting more pre-clinical studies before our approach can be carried over to the clinic. The production of the Biomesh is highly reproducible, scalable and modifiable. “
It is important that no visceral tissue adhered to the new biomesh, while the degree of tissue adhesion was extreme in the case of the mesh commonly used. These results confirmed that this biomesh was effective in reducing the effects of the inflammatory response and preventing visceral adhesions. In addition, the new mesh did not hinder the healing of the abdominal wall after surgical hernia repair in animal models.
“This concept of controlling inflammation through the physicochemical properties of the materials is new. The net was originally designed for mechanical strength. We wondered if we could create a new type of network using the physical and chemical properties of materials. “Said Acharya. “In the 1950s, Dr. Francis C. Usher of the Baylor Department of Surgery developed the first polypropylene mesh for hernia repair. We have developed a next generation mesh that not only provides mechanical support, but also plays a physiological role in reducing the inflammatory response that causes significant clinical problems. “