Cell properties of nucleus pulposus progenitor cells declines with intervertebral disc degeneration

Abstract

Endogenous repair of nucleus pulposus progenitor cells (NPPCs) has exhibited encouraging regenerative potential for treating intervertebral disc degeneration (IDD). However, few studies have explored the properties of NPPCs during the progression of IDD. Hence, additional studies are needed to characterize NPPCs from human degenerated intervertebral disc (IVDs) at different Pfirrmann grades. In this study, human NPPCs were isolated and identified from human IVDs with different Pfirrmann grades. Then, cell biological characteristics, including proliferation, colony formation, cell senescence, migration capacity and chondrogenic ability, were compared. NPPCs were successfully harvested from grade I to IV IVDs, but not from grade V IVD due to the marked loss of nucleus pulposus tissue at grade V, leading to poor cell cultures. All four grades of NPPCs were identified as mesenchymal stem cells (MSCs) based on the criteria of the International Society for Cellular Therapy (ISCT) and shared similar cell morphological characteristics. In addition decreasing trends in proliferation, colony-formation capacity, migration, and chondrogenic ability and increasing levels of cell senescence; were detected in cells from grade I to IV IVDs, with significant changes between NPPCs of grade II and III. In summary, compared with NPPCs from normal IVDs (grade I), cells from degenerated IVDs (grades II to IV) exhibited gradually decreased cell properties and increased cell senescence. Grade II NPPCs displayed the optimal regeneration potential, suggesting that these NPPCs are an ideal candidate for endogenous repair of IDD.

Fluorescence-Activated Cell Sorting Is More Potent to Fish Intervertebral Disk Progenitor Cells Than Magnetic and Beads-Based Methods

“…Noteworthily, the number of CFUs was found to be correlated with Pfirrmann grading scheme of disk degeneration in human NPPC. 16,24 The Tie2 immune staining of 3D pellet culture (Fig. 8) was expected to stain specifically the membranes as it is a surface marker also known as CD202b.…”

“…[21][22][23] Recently, it was reported that the ability to form colonies of isolated NPPCs from human surgical samples is dependent on Pfirrmann grading of the disk. 24,25 Despite their early fading, the study of this marginal subpopulation within the NP might give rise to a better understanding of how these cells affect IVD health, and what conditions are required to maintain them longer. Moreover, a deeper understanding might lead to new approaches for regeneration of the IVD.…”