Low back pain, which is commonly caused by intervertebral disc (IVD) degeneration, is the most common source of chronic pain in Veterans. Current clinical treatments for disc degeneration, including spinal fusion, are limited in that they do not restore healthy disc structure or function. To overcome this limitation, our group has developed a whole, tissue engineered endplate-modified disc-like angle ply structure (eDAPS) composed of engineered annulus fibrosus, nucleus pulposus and endplate regions. To date, we have completed the long-term evaluation of the eDAPS in a small animal model, in addition to short-term evaluation in a large animal, goat cervical disc replacement model. The parent Merit Award will evaluate how these engineered discs function in a degenerative model, as well as their maturation over longer implantation times and with remobilization of the spinal motion segment. Despite the promise of these engineered implants, the inflammatory responses within the eDAPs and their potential for modulating inflammatory biological processes within the intervertebral disc have yet to be evaluated. Thus, the overarching goal of this supplemental Award is to evaluate the inflammatory milieu of the degenerating IVD in a large animal model, and to determine the potential for an eDAPS implant to reset this milieu to enhance regeneration with remobilization. We will achieve this goal via the following Specific Aims: Specific Aim 1: Evaluate the inflammatory responses during intervertebral disc degeneration in a large animal model. In this Aim we will induce degeneration in the goat cervical intervertebral disc via a previously validated chondroitinase ABC injection degeneration model. Following induced degeneration, at 3 months, we will then perform an in-depth analysis of the inflammatory responses involved in degenerative pathology by utilizing next generation sequencing at the single cell level. Specific Aim 2: Determine the immunomodulatory effect of an engineered disc replacement either following injury or following remobilization of the disc replacement. To evaluate the immunomodulatory effect of engineered disc replacements following degeneration (Aim 2a) we will again induce degeneration in the goat cervical intervertebral disc. After the induced degeneration, at 3 months, a second surgery will be performed to implant the eDAPS. Animals will be euthanized after 1 year of eDAPs implantation, and compared to animals which underwent chondroitinase ABC injection but did not have eDAPs implantation. At the 1 year study endpoints, immunophenotyping and inflammatory assessment will be carried out via single cell sequencing followed by validation of specific cellular markers by immunohistochemical analysis. To evaluate whether the mechanical loading environment influences the immunomodulatory effect of eDAPs (Aim 2b), we will utilize remobilization surgeries following implantation. eDAPs will be implanted in the goat cervical spine and immobilize...