Use of Stem Cells in Spinal Treatments

Abstract

The intervertebral disc (IVD) is a complex anatomic structure consisting of a nucleus pulposus (NP), annulus fibrosis (AF), and cartilaginous vertebral end plates. Like all human tissue, these structures undergo age-related degenerative changes termed IVD degeneration (IVDD). In this process, the cell biology of the IVD components is altered. The NP’s ability to synthesize its extracellular matrix components is disturbed, and the AF becomes susceptible to tearing, both of which alter the IVD’s biomechanical properties. As the IVD degenerates, patients may develop discogenic back pain from the inflammatory milieu of IVDD. The altered spinal biomechanics may also contribute to the development of facet joint arthropathy—another source of back pain. The failing AF may allow NP material to herniate resulting in nerve root and/or spinal cord compression. The hope of stem cell treatments is to use pluripotent cells to differentiate into and regenerate normally functional IVD components in order to arrest and/or reverse the degenerative changes of IVDD. Some evidence of IVD regeneration has been seen in both animal studies and small clinical trials. In addition to IVD regeneration, the pluripotent nature of stem cells also lends them to facilitate spinal fusion by differentiating into osteoblasts and creating a biologic environment more favorable for fusion. Animal studies and clinical trials have also shown some promise in facilitating spinal fusion. In general, more clinical data are needed to ascertain whether stem cells may be effective in the treatment of IVD degeneration and in positively influencing spinal fusion procedures.