Bridging Nerve Gaps for Faster Regeneration

Building bridges is nothing unusual for engineers. But for Dr. Christine Schmidt, professor of biomedical engineering, the bridges in question connect human nerves.

Dr. Christine Schmidt

Dr. Christine Schmidt

Schmidt analyzes and designs biomaterials and therapeutics that can interface with the nervous system and, ultimately, enhance an injured nerve’s ability to regrow or regenerate by physically supporting tissue growth and guiding injured nerves to reconnect. Regrowing nerves is not enough, though; they have to function.

“Because nerves communicate through electrical signaling, we work with electrically conducting polymers, and with hyaluronic acid-based hydrogels, which are naturally derived sugar molecules normally found in the body. We also work processing intact natural tissues so they are more usable from a clinical standpoint.” Schmidt, working with graduate and undergraduate students in the Cockrell School, succeeded in removing from nerve tissue its cellular lipid components, which are the predominant cause of transplant rejection.

“We were able to develop a technique that preserves the delicate micro-architecture of the nerve,” Schmidt says. “A nerve is very dense, fatty tissue, so creating decellularized tissue that can be used off the shelf wasn’t very straightforward.” In fact, it took about four years to perfect the process. Results from animal studies were published in 2004, and AxoGen, a Florida company, read the article and contacted Schmidt. AxoGen eventually licensed the decellularization technology, creating a transplant tissue called Avance®, which it provides to surgeons as a graft for injuries to peripheral nerves, such as those in the hands and face. The company also hired a graduate and an undergraduate student who had worked on the research under Dr. Schmidt.

Avance has now been used in more than 3,000 patients, Schmidt adds, and those patients are reporting functional recovery comparable to the previous treatment method. That involved using a nerve from elsewhere in the patient’s body as a graft, and while surgeons used sensory nerves to minimize loss of function, some loss still occurred. It also involved an additional surgical procedure, which is not necessary with the new material.

Schmidt is now testing use of hydrogel biomaterials on the spinal cord, and early results are promising. The prognosis for spinal cord research in general has become more positive, and she expects a combination of pharmacological, rehabilitation, and biomaterials will eventually be successful. Current research focuses on restoring function of individual organs, rather than the entire spinal cord at once.

The potential pool of those who could benefit from the biomaterials developed at the Cockrell School include soldiers, workers, car accident victims, and cancer patients. Peripheral nerve injuries are more prevalent than spinal cord injuries, Schmidt says, and while not as devastating, they do cause loss of function and control.

Schmidt lets her students lead research, helping them out as necessary. “Students do study design and data analysis,” she says. “I help with brainstorming and interpretation, and play devil’s advocate, asking if they did the right controls, for example. It’s also my role to bring in funding. But students are absolutely integral. One of my graduate students, Terry Hudson, is listed as co-inventor on the patent for the decellularized nerve tissue. I think it’s pretty impressive coming out of graduate school with a patent, especially one that’s been commercialized.”

Schmidt earned her 1988 UT bachelor's degree in chemical engineering.  Her work is supported by the BF Goodrich Endowed Professorship in Materials Engineering.