Materials for cell delivery in degenerated intervertebral disc

Several polymers have been investigated as potential cell delivery carriers for intervertebral disc (IVD) regeneration, which can be divided into natural and synthetic biopolymers and can be used in the form of hydrogels or solid scaffolds. Biomaterials provide a stable threedimensional (3D) environment for cell proliferation and extracellular matrix (ECM) synthesis, by serving as a load bearing structure to support IVD biomechanical forces. Ideally, it should degrade in parallel with neo-tissue formation, without forming toxic subproducts. Also, biomaterials enable better reproduction of the native tissue by providing clearly defined microstructures and macrostructures. Although some approaches to IVD regeneration consider the use of
cell-free materials and growth factors, cell delivery to the degenerated disc by using a biomaterial carrier seems to be among the most promising research directions. As the native disc has low cellular content, and in the process of IVD degeneration the existing cells become senescent, cell-based tissue engineering approaches are focusing on the transplantation of different cell types, including IVD cells, mesenchymal stem cells (MSCs), and other chondrocytic cells. The advantages of using polymer biomaterials include inexpensive production, facility and flexibility of the manufacturing process, and accessibility to an extensive diversity of properties. Scaffolds composed by natural and synthetic polymers have been investigated for in vitro cell–biomaterial interaction and in vivo implantation in animal models of IVD degeneration. Some of the most studied and promising natural and synthetic polymer-based biomaterials for cell delivery in the degenerated IVD will be discussed herein.