Evaluation of CD24 as a marker to rapidly define the mesenchymal stem cell phenotype and its differentiation in human nucleus pulposus.
BACKGROUND
Recent studies have indicated that human nucleus pulposus contain mesenchymal stem cells (NP-MSCs). However, the immunophenotypic variation of NP-MSCs in vitro was unclear. The present study was conducted to address the immunophenotypic variation of mesenchymal stem cells in nucleus pulposus under continuous proliferation in vitro and show the difference between mesenchymal stem cells and nucleus pulposus cell.


METHODS
Tissue samples were obtained from thoracolumbar burst fracture patients and degenerative disc disease patients who underwent discectomy and fusion procedures. Flow cytometric and laser scanning confocal microscope (LSCM) were used to detect the variation of mesenchymal stem cells in nucleus pulposus which were expressing CD105 and CD24 in condition with or without transforming growth factor β1 (TGF-β1).


RESULTS
More than 90% of the analyzed primary cells of mesenchymal stem cells in nucleus pulposus fulfilled the general immunophenotyping criteria for MSCs, such as CD44, CD105 and CD29, but the marker of mature NP cells characterized as CD24 was negative. In continuous cultures, the proportion of mesenchymal stem cells which were expressing CD44, CD105 and CD29 in nucleus pulposus gradually decreased. The mesenchymal stem cells in nucleus pulposus cells were positive for CD105 and CD29, with slight positivity for CD44. The CD24 expression gradually increased in proliferation. Biparametric flow cytometry and laser scanning confocal microscopy confirmed the presence of cells which were expressing CD105 and CD24 independently, and only a small part of cells expressed both CD105 and CD24 simultaneously. TGF-β1 could stimulate mesenchymal stem cells in nucleus pulposus to express CD24.


CONCLUSIONS
Non-degenerative and degenerative NP contains mesechymal stem cells. The variation of CD24 can be used as a marker to identify the NP-MSCs differentiation into NP-like cells.
Department of Orthopaedics Surgery, Second Hospital, Shanxi Medical University, Taiyuan, Shanxi 030001, China; Department of Orthopaedics Surgery, Da Yi Hospital, Shanxi Medical University, Taiyuan, Shanxi 030032, China.
Xiaoming
X
Guan
Department of Orthopaedics Surgery, Da Yi Hospital, Shanxi Medical University, Taiyuan, Shanxi 030032, China. Email: maxun2532@sina.com.
Xun
X
Ma
Department of Orthopaedics Surgery, Da Yi Hospital, Shanxi Medical University, Taiyuan, Shanxi 030032, China.
Li
L
Zhang
Department of Orthopaedics Surgery, Da Yi Hospital, Shanxi Medical University, Taiyuan, Shanxi 030032, China.
Haoyu
H
Feng
Department of Orthopaedics Surgery, Da Yi Hospital, Shanxi Medical University, Taiyuan, Shanxi 030032, China.
Zhuo
Z
Ma
D000328:Adult; D015703:Antigens, CD / Q000378:metabolism; D051927:CD24 Antigen / Q000378:metabolism*; D002454:Cell Differentiation / Q000502:physiology; D002478:Cells, Cultured; D000071063:Endoglin; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D018960:Hyaluronan Receptors / Q000378:metabolism; D019012:Integrin beta1 / Q000378:metabolism; D007403:Intervertebral Disc / Q000166:cytology* / Q000378:metabolism; D008297:Male; D059630:Mesenchymal Stem Cells / Q000166:cytology* / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000378:metabolism; D055815:Young Adult
D015703:Antigens, CD; D051927:CD24 Antigen; C064206:ENG protein, human; D000071063:Endoglin; D018960:Hyaluronan Receptors; D019012:Integrin beta1; D011956:Receptors, Cell Surface