An Ex Vivo Intervertebral Disc Slice Culture Model for Studying Disc Degeneration and Immune Cell Interactions

Intervertebral disc degeneration is a leading cause of back and leg pain and a major contributor to disability worldwide. Despite its prevalence, treatments remain limited due to incomplete understanding of its pathology. In vivo models pose challenges for controlled conditions, while in vitro cell cultures lack key cell-cell and cell-matrix interactions. To address these limitations, we developed a novel tissue slice culture model of mouse discs, in which intact mouse discs were sliced down to 300 μm thickness with a vibratome and cultured ex vivo at various time points. The cell viability, matrix components, structure integrity, inflammatory responses, and macrophage interactions were evaluated with biochemistry, gene expression, histology, and 3D imaging analyses. Disc slices maintained structural integrity and cell viability, with preserved extracellular matrix in the annulus fibrosus (AF) and mild degeneration in nucleus pulposus (NP) by day 5. Interleukin-1 (IL-1) induced disc degeneration manifested by increased glycosaminoglycan release in media and reduced <i>aggrecan</i> and <i>collagen II</i> mRNA levels in disc cells. Cultured disc slices promoted macrophages towards pro-inflammatory phenotype with elevated mRNA levels of <i>il-1α</i>, <i>il-6</i>, and <i>inos</i>. Macrophage overlay and 3D imaging demonstrated macrophage infiltration into the NP and AF tissues up to ~100 µm in depth. The disc tissue slice model captures key features of intervertebral discs and can be used for investigating mechanisms of disc degeneration and therapeutic evaluation.