The intervertebral discs of the spine are one of many small body parts that one will never put any thought into until they start to fail, at which point pain and disability ensure that they are never far from mind. One section of the large regenerative medicine community is focused on the spine and its supporting tissues; this open access paper is a review of approaches intended to repair damaged and worn intervertebral discs, from the expected stem cell therapies to more esoteric and novel options. This is all work in progress, and sadly it remains the case that benefits for patients as a result of these lines of work are still modest and unreliable for many of the possible forms of deterioration.
Low back pain (LBP) is one of the most common causes of activity limitations, neurological deficit, and disability in affected individuals. Intervertebral disc (IVD) disorders contribute to LBP and neck pain in multiple ways with few available treatments. New approaches are urgently needed for the treatment of degenerative disc disease (DDD). In the past decades, diverse strategies have been developed aiming to ameliorate IVD degeneration and promote its regeneration. While considerable progress has been achieved in treatment and regeneration of nucleus pulposus (NP) in the center of the disk, much less is achieved in that of the surrounding annulus fibrosus (AF). As a crucial supporting component in the biomechanical constitution of IVD, the structural and mechanical integrity of AF is highly essential in confining NP, and tears or fissures in AF are closely associated with the onset and development of DDD.
Various biotherapies have been proposed, including molecular therapies, nucleic acid-based therapies and mechano-regulated cell based therapies. These therapies, aiming at supplementing biologics including growth factors, genes, and cells in AF, have shown promising results in vitro and in vivo. Nevertheless, their clinical uses still remain a major concern due to the short-term efficacy and insufficient stability of them. These limitations may be, at least partially, overcome by biomaterials-based tissue engineering (TE) using a combination of cells and biomolecules to restore AF anabolism.
Scaffolds are one of the most important elements in AF TE by providing appropriate mechanical properties, adequate space, and biochemical cues for seeded cells to grow, differentiate, and produce extracellular matrix (ECM) to regenerate AF tissue. Various kinds of scaffolds have been designed for AF engineering. The scaffolds can be made from natural materials or synthetic materials. These scaffolds can be fabricated and processed using various techniques depending on the desired structure characteristics and mechanical properties of the final engineered tissue. Among the techniques, electrospinning is preferred for AF TE by researchers for its ability to produce micro- and nanofibers which largely recapitulate the structural characters of native AF tissue. The mechanical properties of scaffolds remarkably affects the biochemical and biomechanical properties of cultured AF-derived stem cells and the ECM they produce.