Human nucleus pulposus intervertebral disc cells becoming senescent using different treatments exhibit a similar transcriptional profile of catabolic and inflammatory genes.

PURPOSE

Chronic low back pain has been associated with intervertebral disc (IVD) degeneration, which is characterized by the accumulation of extracellular matrix (ECM)-degrading proteases and inflammatory molecules in the degenerate tissue. IVD degeneration could be the outcome of natural organismal ageing and/or of the exposure of the disc to cumulative stressful environmental stimuli and is accompanied by an increased population of senescent cells in the tissue. On the other hand, senescent cells are known to secrete proteolytic enzymes and inflammatory molecules, which can contribute to ECM catabolism. The aim of this study was to investigate the transcriptional profile of selected metalloproteinases (MMPs) and inflammatory mediators in human nucleus pulposus IVD cells that became senescent using three different approaches: serial subculturing, exposure to ionizing radiation and p16INK4a overexpression.

METHODS

Gene expression was assessed using quantitative RT-PCR and protein levels were determined by western blot analysis. The proliferative potential of the cells, as well as the percentage of senescent cells in the population were estimated by nuclear BrdU incorporation and by senescence-associated β galactosidase staining, respectively.

RESULTS

All senescent cells showed a similar regulation of MMP-1, -2, -3, -9, interleukin (IL) 6, IL8 and interferon γ at the level of transcription, with only some quantitative differentiations observed in p16INK4a-overexpressing cells.

CONCLUSIONS

Data described here suggest that senescent cells may have similar functions in IVD homeostasis, irrespective of the origin of senescence induction.