Hydrogels in acellular and cellular strategies for intervertebral disc regeneration

Abstract

Low back pain is an extremely common illness syndrome causing patient’s suffering and disability which demands for urgent solutions in order to improve life quality of the patients. Treatment options aimed to regenerate the intervertebral disc (IVD) are still under development. The huge cellular complexity of IVD, and consequently its fine regulatory system, makes it a challenge to the scientific community. Biomaterials-based therapies are the most interesting solutions nowadays, wherein tissue engineering and regenerative medicine (TE&RM) strategies are included. By using such strategies, i.e., combining biomaterials, cells and biomolecules, the ultimate goal of reaching a complete integration between native and neo-tissue can be achieved. Hydrogels are promising materials to restore IVD, mainly nucleus pulposus (NP). Herein, an overview of the use of hydrogels in acellular and cellular strategies for intervertebral disc regeneration is presented. To better understand the IVD and its functioning, several topics will be focused, i.e., anatomy, pathophysiology, cellular and biomolecular performance, intrinsic healing processes and current therapies. In this review, the application of hydrogels as NP substitutes will be addressed, due to the similarity to NP mechanical properties and extracellular matrix. These hydrogels can be used in cellular strategies, when combined with cells from different sources,, or in acellular strategies, by performing the functionalization of the hydrogels with biomolecules. In addition, a brief summary of therapies based on simple injection envisaging primarily the biological repair will be tackled. At last, a special emphasis has been given to original works reporting the use of autologous cells and biomolecules (e.g.,Platelet-rich plasma) and envisioning the clinical application.