Regenerative potential of human nucleus pulposus resident stem/progenitor cells declines with ageing and intervertebral disc degeneration

Numerous studies have demonstrated the presence of resident nucleus pulposus stem/progenitor cells (NPSCs) in the tissue of the intervertebral disc (IVD). However, the cellular identity of NPSCs during IVD degeneration and ageing are poorly defined at present, despite significant progress in the understanding of NPSC biology. In the present study, NPSCs were isolated from human degenerated IVD and were characterized by flow cytometry, gene expression assays and proliferation and multipotency analysis. The results of the present study demonstrated that NPSCs isolated from human degenerated IVD may be divided into two groups according to the expression of mesenchymal stern cell (MSC) surface markers: The high expression of MSC surface markers group (H-NPSCs) was highly positive for CD29, CD44, CD73, CD90 and CD105 at rates >95%, and the low expression of MSC markers surface markers group (L-NPSCs), with the expression of CD29 and CD105 exhibiting individual variability, however, all at rates <95%. The donors for H-NPSCs were aged <20 years, while the majority of donors for L-NPSCs were aged >25 years, with one exception aged <20 years. The results highlighted that the low expression of MSC surface markers in NPSCs from aged and degenerated NP tissues were associated with a low rate of proliferation and reduced differentiation potential, as well as downregulation of the NP progenitor marker Tie2 and higher expression of NP cell-specific markers. These findings demonstrated that the regenerative potential of human NPSCs declines with ageing and degeneration of the IVD.