Young rabbit adipose-derived mesenchymal stem cells (rADSCs) demonstrated strong chondrogenic differentiation potential and osmotic stress responses mirroring native nucleus pulposus cells — a key compatibility marker for disc regeneration. Senescent rADSCs, by contrast, exhibited complete loss of chondrogenic capacity alongside a markedly catabolic transcriptional profile: upregulation of matrix metalloproteinases MMP1, MMP3, and MMP13, and downregulation of the structural proteoglycan aggrecan. When injected intradiscally into rabbit lumbar discs, senescent cells worsened tissue quality at 8 weeks compared to young cell controls.
This finding directly confronts a practical bottleneck in regenerative medicine: achieving clinically viable cell numbers requires extensive ex vivo passaging, which drives replicative senescence. The study is the first to directly compare intradiscal injection outcomes between young and passage-senescent ADSCs in a live model, making it more than confirmatory — it closes a critical translational knowledge gap. The MMP upregulation pattern mirrors the endogenous catabolic milieu already present in degenerating discs, suggesting senescent cells could amplify, rather than reverse, the degenerative cascade. Limitations include the rabbit model's anatomical differences from human lumbar anatomy, the 8-week observation window (which may miss longer regenerative effects), and the absence of pain or functional biomechanical endpoints. For clinicians and bioengineers developing cell therapies, the implication is clear: passage number and senescence screening are non-negotiable quality controls before any disc regeneration application reaches human trials.
