Novel Nitrogen Rich Polymers and Chitosan for Tissue Engineering of Intervertebral Discs

Degenerative disc disease has been implicated as a major component of spine pathology. However, though biological repair of the degenerate disc would be the ideal treatment, there is a lack of a universally accepted scaffold for tissue engineering of intervertebral discs (IVD) and little is known of how to differentiate mesenchymal stem cells (MSCs) to a disc-like phenotype. We show that 2.5% Protasan® UP G213 cross-linked to 5% genipin might be a promising scaffold for disc tissue engineering. Furthermore, we have developed extremely N-rich plasma polymer layers, which we call "PPE:N" (N-doped plasma-polymerized ethylene, containing up to 36% [N]). We show that PPE:N almost completely suppresses the expression not only of type X collagen, but also of osteogenic marker genes such as alkaline phosphatase (ALP), bone sialoprotein (BSP) and osteocalcin (OC). In contrast, neither aggrecan nor types 1 collagen expression were significantly affected. These results indicate that PPE:N coatings may be suitable surfaces for inducing MSCs to a chondrocyte or disc-like phenotype for tissue engineering of cartilage or IVDs, in which hypertrophy and osteogenesis are suppressed.