Tissue engineering is an exact science with materials specifically designed to function in the body; at least, it was, until Dr. Andrew Pelling began chopping asparagus one night during dinner. In his Ted Talk, Pelling describes observing the nerve-like structure of the asparagus stalk and hypothesized it could help damaged spinal nerves reshape within the structure of cells .
Spinal cord injury (SCI), defined as damage to the spinal cord nerve tissue and vertebral or ligamentous injuries that comprise spinal cord integrity, is a significant contributor to the global burden of injury . In developed countries, the annual incidence of SCI is 51 million people per year with mortality rates of 48-79% , and in low and middle income countries, morbidity and mortality are even higher due to deficits in prehospital care, treatment and rehabilitation . Symptoms range from pain and numbness to paralysis and complete loss of independence .
Currently there is no treatment for the underlying problems of scar and cyst formation where the injury begins, but even if the goal of complete motor recovery isn’t achieved, a patient’s quality of life can be significantly improved with recovery of bowel, bladder, sexual and tactile functions. Many researchers are looking into fabricating biomaterials with microscale channels to guide regenerating neurons by promoting axonal regrowth, supporting formation of blood vessels and mitigating scar tissue formation. Scaffolds, which are prevalent in tissue engineering research, are materials that are designed to promote cell function with their environment and structure. There are a variety of potential natural and synthetic polymers being used in animal studies, but these often require pharmaceutical additions to produce an effect . Furthermore, the options of scaffolds from polymers, animal products or human cadavers are not cost effective, especially when considering the expenses for care of individuals with SCI .
The Pelling Lab has done previous work on decellularizing plant tissue and forming sterile, biocompatible and implantable biomaterials that promote vascularization and tissue formation. They saw potential in the geometry of plant tissue vascular bundles for stripping down the DNA and cells to leave behind natural fibers to support neural tissue regeneration .
As Pelling says, “this is a really dumb idea” . He elaborates with, “humans aren’t plants and plant tissues shouldn’t be in the spinal cord.” Scaffolds should be designed to disappear over time as normal healthy tissues are incorporated, but humans don’t have the enzymes required to break down vegetable tissue. This is exactly why the researchers had success in their experiments —the asparagus was biocompatible because plant tissue is inert and the cells are still benefiting from its shape and stability. This idea can be studied in different vegetable plants with alternate structures; however, there is not much research into the topic as of now.
When planning this experiment, Pelling talked to one of the top neurosurgeons in Canada, Dr. Eve C. Tsai, who spent some time thinking about the idea and looking at the scaffolds. She then immediately asked, “can I take these today and use them in a patient?” She cited problems with scaffolding breaking down and was excited about the prospect of a long-lasting and stable material .
The researchers then began the experimental design. First was creating the asparagus scaffold, which had the same motion and feel as human tissue. The process involved putting asparagus in a soap-like solution and shaking and spinning it for a few days to pull out all the plant cells. The result was an almost completely white structure that still held the same shape, which was then put in a petri dish and covered in cells that grew and invaded the inside of the scaffold over time .
Next, they anesthetized the rats, exposed their spinal cords and cut nerves in the T8-T9 spinal cord region to render them a paraplegic. The scaffold was implanted between the severed ends of the spinal cord to act as a bridge that would carry neural impulses. Pelling did not add therapeutic stem cells, electrostimulation, bioelectrics or any other expensive pharmaceutical products that are often used to achieve meaningful results.
About two weeks after the implants, the animals were scratching and biting their legs, giving hope they were regaining some feeling. Over the next 12 weeks, the animals went from being paralyzed from the waist down to having leg movement and then starting to lift themselves up on their back legs. These crucial signs of SCI recovery showed activation of core and leg muscles as healthy cells migrated into the scaffold and became a living tissue in the body . Furthermore, histological analysis showed minimal scarring and axonal regrowth through the scaffolds. They did not regain perfect motor function back, but for such a far-fetched initial idea, this was a success.
The FDA has designated Pelling and Tsai’s work a breakthrough medical device, and human clinical trials are being planned to start in the next two years . Pelling’s idea of going to the grocery store to find scaffolds has led to the possibility of individuals with paralysis regaining some independence in their lives.
Edited by: Lily Luu
Illustrated by: Shanthi Deivanayagam