T cells play a protective role in maintaining spinal health after intervertebral disc injury 2308705

Abstract Introduction The intervertebral disc (IVD) is an essential joint of the spine that is prone to injury and exhibits limited regenerative capacity, leading to degeneration and chronic back pain. While T cells are known mediators of tissue repair, the specific T cell subtypes that infiltrate the IVD following injury remain poorly defined. We previously demonstrated a temporally oscillatory T cell response after IVD injury in C57BL/6J mice, with reduced degeneration associated with γδ T cell infiltration in females only (Clayton et al., 2024). In other tissues, γδ T cells promote repair following injury; however, their presence and role in the IVD have not been explored. We hypothesize that T cells, particularly γδ T cells, are essential for IVD repair. Methods Using a mouse model of accelerated IVD degeneration, control (non-injured) and injured (needle puncture) IVDs were harvested from the same female, 4-month-old female C57BL/6J wildtype (WT) mice, WT mice treated with TCRγγ-depleting or IgG control antibodies, and T cell knockout (TCRβγKO) mice (n = 3/group). IVDs were analyzed by Safranin O/Fast Green histology (n = 3—4) and flow cytometry (n = 3). Deidentified human IVD tissue was collected from female patients undergoing spinal fusion surgery (n = 3). Results Histological analyses revealed significantly increased injury-induced degeneration in TCRβγKO mice compared to WT controls. Depletion of TCRγγ more severely exacerbated degeneration relative to IgG-treated and TCRβγKO injured mice. Comparative analyses of WT mouse and human samples showed similar proportions of infiltrating CD3+ T cells following injury, with CD4⁻CD8⁻ double-negative T cells comprising the largest population; γδ T cells represented the majority of this subset. Conclusion Collectively, these data demonstrate that γδ T cells infiltrate the injured IVD and play a protective role against degeneration. Loss of γδ T cells worsens injury-induced degeneration, indicating a key immunomodulatory function in maintaining IVD integrity following injury. Funding Source Burroughs Wellcome Fund PDEP Award, Skeletal Disorders Training Program T32 AR060719 Topic Categories Immune Response Regulation: Cellular Mechanisms (IRC)