CD24 expression indicates healthier phenotype and less tendency of cellular senescence in human nucleus pulposus cells

Abstract

Identification of specific cell markers is crucial for recognizing functionally healthy nucleus pulposus (NP) cells. The objective of this study was to investigate the role of CD24 expression in adult human NP cells. Cells were retrieved from NP tissues of 20 patients (aged 17–44) operated on for lumbar disc herniation. Based on CD24 expression, NP cells were separated by sorting and then used to examine phenotypic behavior, the effects of culture conditions and cellular senescence pathway related proteins. CD24 expression was positive in 35.5 ± 3.7% (range 9.1–65.2%) of NP cells. Consistently, normoxic expansion and serial passages in monolayers decreased percentage positivity for CD24 in NP cells. CD24^– NP cells showed a markedly decreased GSK-3β activity and increased mitogen-activated protein kinase phosphorylation accompanying by an increased β-catenin expression. Higher levels of matrix metalloproteinases, as well as lower levels of ACAN and COL2 in CD24^– cells, indicated the breakdown and reduced the formation of key extracellular matrix components. CD24⁺ NP cells presented a more favorable phenotype while CD24^– cells showed a more prominent cellular senescence fate. CD24 in NP cells may be a surrogate marker of healthy cells, in the cell-based therapeutic treatment of degenerative disc disorders.

Keywords:

• Nucleus pulposus
• cell therapy
• CD24
• phenotype
• cellular senescence

Acknowledgements

The authors are grateful for the technical support provided by the image core at the First Core Lab of National Taiwan University College of Medicine and the Microscopy Core Facility, Department of Medical Research, National Taiwan University Hospital. The authors thank Department of Medical Research in the National Taiwan University Hospital for technical assistance.

Disclosure statement

The authors confirm that there are no conflicts of interest.

Additional information

Funding

This work was supported by the Ministry of Science and Technology, Taiwan, [grant Nos. [104–2314-B-002–049 and 105–2341-B-002–014-MY2].