Researchers develop bioengineered spinal disc implants

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Researchers have developed tissue-engineered intervertebral disc (IVD) implants which have been successfully implanted in rodents’ spines, according to study findings published Aug. 1 in the Proceedings of the National Academy of Sciences.

At an estimated annual cost of up to $100 billion, lower back and neck pain are among the most common physical conditions for which patients see their doctors, according to study author Lawrence J. Bonassar, PhD, associate professor of biomedical engineering and mechanical engineering at Cornell University in Ithaca, N.Y., and colleagues. The most common target for treatment of those problems is the IVD, and despite use of medication and physiotherapy, an estimated 1.5 to four million U.S. patients await surgical intervention, which includes removal of herniated tissue or the entire disc and replacement with a mechanical device, according to the authors.

The use of non-biological replacement disc implants has been associated with problems such as mechanical failures, dislodgement, polyethylene wear and implant loosening, according to the authors. “More recently, increasing attention has been turned toward creating tissue engineering strategies to restore function to the diseased or injured IVD,” authors wrote.

In their study, researchers constructed tissue-engineered total disc replacement implants and inserted them into the caudal disc space of athymic rats. Composed of collagen and a hydrogel called alginate, the implants are seeded with cells that repopulated the structures with new tissue.

“We’ve engineered discs that have the same structural components and behave just like real discs,” said Bonassar. “The hope is that this promising research will lead to engineered discs that we can implant into patients with damaged discs.”

Authors noted a number of challenges related to implanting tissue-engineered total disc replacements, such as generating functional tissue in the disc space, securing the implants in the spine, and developing an implant that can withstand complex mechanical loading of the disc space, according to the study.

“Here we demonstrated that our tissue engineered IVD disc implants were able to meet all three of these challenges in the rat caudal spine by producing a collagen and proteoglycan-rich, well-integrated, and mechanically functional tissue in the native disc space,” wrote Bonassar et al. “This study provides the first evidence that a tissue engineering IVD disc implant can replace the native IVD in the spine.”

The researchers’ work offers promise for the estimated 40 to 60 percent of U.S. adults suffering from chronic back or neck pain. Interestingly, the implants have actually been shown to improve over time, as opposed to degrade like current artificial implants.

“Our implants have maintained 70 to 80 percent of initial disc height. In fact, the mechanical properties get better with time,” said Bonassar.

The project was initially funded in 2006 with seed money from Ithaca-Weill. The researchers have since received grants from Switzerland's AO Spine foundation and NFL charities.