Tissue-engineered disc replacements are a potential alternative option to fusion surgery for the treatment of severe intervertebral disc (IVD) degeneration. In a new study, researchers report on the successful long-term integration and mechanical function of engineered discs in vivo, including in a large animal model, moving this approach a step towards translational feasibility.

Credit: Science Photo Library/Alamy Stock Photo

In previous short-term studies, the researchers had tested various iterations of a disc-like angle ply structure (DAPS) in a rat disc replacement model. These structures have distinct components that mimic the structure of the native disc. “Our latest iterations of the DAPS includes an ‘endplate’ that promotes integration between the native vertebral bodies and our engineered implant,” explains Robert Mauck, corresponding author of the new study.

The eDAPS sized for the rat caudal spine maintained its structure and composition 20 weeks after in vivo implantation in the rat tail. Data from various assessments including second harmonic generation (SHG) imaging suggested that the eDAPS functionally integrated with the native discs at the endplate interfaces. The mechanical properties of the eDAPS stayed the same or improved after 20 weeks, with the tensile and compressive mechanical properties reaching near-native values.

The mechanical properties of the eDAPS stayed the same or improved after 20 weeks

The researchers also tested eDAPS sized for the human cervical disc space in a goat cervical disc replacement model. The findings paralleled those of the rat model, with the eDAPS compositionally and functionally maturing after 8 weeks in vivo.

“Given these findings, translation to humans is a real and distinct possibility,” explains Mauck. “There is of course quite a lot to do in our goat model, such as longer term evaluation, aggressive remobilization and implantation into a diseased (rather than an acute defect) environment, before we can move on to human clinical trials.”