Current methods for repairing damaged nerves are hit-and-miss and limited to short-range repair. For the first time, researchers have combined two types of silk to create a promising biocompatible method of regenerating damaged nerves over long distances.
Peripheral nerves send messages from the brain and spinal cord to other parts of the body, such as moving muscles when you walk or letting you know your feet are cold. Peripheral nerves are easily damaged, interfering with the brain’s ability to communicate with muscles and organs.
The standard treatment for repairing damaged peripheral nerves is autograft, in which a surgeon removes the damaged area and replaces it with nerves from elsewhere in the body. Nerve grafts are taken from a sensory nerve, usually the sural nerve, which provides sensation to areas of the skin where sensation is not important. However, the success rate of nerve transplantation is hit and miss.
Nerve guides, tubular structures that fill gaps by suturing the ends of severed nerves, have been around for about 30 years. However, they can only be used to fill small gaps. Currently, FDA-approved nerve guides are limited to short-range nerve defects of up to 1.2 inches (3 cm). Longer distances require an internal framework that provides the necessary structural and cellular support.
Researchers at the University of Oxford and the Medical University of Vienna have created a new nerve guide by combining two types of natural silk harvested from silkworms (Bombyx mori) and the Golden Orb Weave Spider (Trichophylla edulis) may regenerate nerves at longer distances.
Previous studies have demonstrated the benefits of using silk as a biomaterial. Silkworm cocoon filaments are composed of fibroin and sericin proteins. Both are biocompatible, stretchy and tough. Silk fibroin has been shown to induce wound healing by promoting cell proliferation and growth. Orb weaving spider dragline silk has excellent mechanical properties such as high tensile strength and flexibility.
For the first time, researchers have combined the characteristics of silk fibroin reconstituted into tubes and natural spider silk filaments to create silk-in-silk conduits. The walls of the ducts were made of silkworm silk fibroin, filled with sphere-weaving spider dragline silk fibers, and acted as internal guiding structures like nerve railings.
Nerve guides were tested in rats in which the right sciatic nerve was transected, resulting in a significant gap of 0.4 inches (10 mm). Researchers have found that damaged nerves adapt to silk nerve guides and grow along the silk threads, successfully reconnecting severed ends.
“Our study found that peripheral nerves work better when such threads are made of silk, and spider silk seems to be preferred for guide rails,” said Dr. Author Lorenz Semler says:
The researchers also gained a deeper understanding of the molecular structure of silkworm silk ducts and found that their porosity allows for the exchange of nutrients and waste products that are essential for the healing process. Moreover, cells involved in nerve regeneration were seen to adhere to both types of silk.
“As part of our research, we were not only able to successfully repair nerves, but we were also able to dissect the components of the healing process,” said Semmler.
Using natural materials for nerve guides has distinct advantages over synthetic materials. Spider silk is biodegradable and produces very little immune response in animal models. It’s also scalable. A single harvest from the orb weaving spider yields about 33 feet (10 m) of silk, enough to fill a 0.4 inch (10 mm) long nerve guide. allows the incorporation of , and may promote nerve regeneration over longer distances.
“Animal silk offers excellent mechanical and biological properties and versatile manufacturing potential to assist in tissue reengineering,” said study co-author Fritz Worrath. I’m here. “Our advanced silk-in-silk nerve guide combines the superior ability of silkworm silk to be processed into three-dimensional structures with the superior cell adhesion properties of spider dragline silk.”
The researchers hope their findings pave the way for the development of ‘off-the-shelf’ nerve guides for treating peripheral nerve injuries in humans.
The study was published in a journal advanced medical materials.
Source: Medical University of Vienna/University of Oxford
