Putting Your Back into It

Used for the treatment of back pain caused by (advanced) degenerative disc disease, “spinal fusion” doesn’t sound like a walk in the park – for the surgeon or the patient. Though it can offer pain relief where other (less invasive) efforts have failed, it can result in reduced mobility and the need for successive surgery to treat increasingly stressed adjacent discs. As ever, better alternatives are sought – and the restoration or replacement of intervertebral discs is one clear direction; however, the pace of development in the field has been slow. Recent work by a collaboration of researchers across the USA demonstrates the feasibility of disc replacement with a bioengineered construct (1).

The group designed an “endplate-modified disc-like angle ply structure” – eDAPS, for short – to copy the native structure of intervertebral discs. The discs are “grown” out of mesenchymal stem cells that infiltrate a hydrogel and polymer scaffold matrix that sits between two polymer endplates. In a rat caudal disc replacement model, the bioengineered eDAPS showed the same compressive mechanistic properties as native disc tissue after 20 weeks in vivo. Implantation of larger eDAPS in a goat cervical disc replacement model showed similarly positive results after eight weeks. As one of the project leads, Professor Harvey Smith of the University of Pennsylvania explains, this is an important translational step: “What’s significant about the goat model is that the dimensions are analogous to the human cervical spine […] We’ve shown that we’re able to scale up our implant to the dimensions of a human.”

The researchers are continuing to assess integration of eDAPS and the long-term effects of implantation in the goat model, and will start considering human trials in earnest; Smith is already mulling tweaks to the process: “In humans, we would likely use harvested homologous stem cells to grow these implants with a patient’s own cells,” he says.

Will the crude “welding” of spinal fusion be replaced by a subtler biomimetic approach? Perhaps the goats (or rats) have the answer