Transcriptomic and Functional Comparison of Cells Isolated From Healthy and Degenerated Ovine Intervertebral Discs

Intervertebral disc degeneration (IVDD) is a leading cause of chronic low back pain, yet its cellular and molecular mechanisms remain incompletely understood. Sheep represent a valuable in vivo and ex vivo model for IVDD due to their anatomical and biomechanical similarities with humans and the possibility to access disc samples at early stages of degeneration. In vitro, isolated annulus fibrosus (AF) and nucleus pulposus (NP) cells may provide insights into age-associated degenerative processes; this work investigates how well they capture senescence and metabolic alterations observed in vivo. Transcriptomic profiling of AF and NP cells from healthy young lambs and mildly degenerated aged sheep revealed distinct age- and tissue-specific signatures, with upregulation of inflammatory mediators, ECM-remodelling enzymes, and senescence-associated genes in aged cells. Cross-species deconvolution using a human single-cell RNA-sequencing reference confirmed conserved transcriptional modules between aged sheep and human degenerated discs, underscoring the model's translational relevance. However, functional assays demonstrated comparable responses of young and aged cells under basal conditions and after exposure to pro-degenerative stressors (IL-1β, senescence induction). Altogether, these findings validate sheep cells as a suitable in vitro model for studying disc degeneration mechanisms and for preclinical testing, although aged donors offer no clear additional functional benefits.