Differential Characterization of Two Kinds of Stem Cells Isolated from Rabbit Nucleus Pulposus and Annulus Fibrosus

Figure 4

Morphology and nucleostemin expression of AFSCs (a, b) and NPSCs (c, d) at passage 5. Both AFSCs and NPSCs expressed nucleostemin ((b, d), yellow arrows and inset images) at higher passages, whereas the expression levels of nucleostemin decreased (g) and much nucleostemin released from nuclei ((b, c), green arrows). Furthermore, some senescence-like cells were found in NPSCs ((c, d), white circles) and some AFSCs started differentiation and no longer expressed nucleostemin ((b), white arrows). On the other hand, fibroblasts isolated from rabbit discs were negatively stained for nucleostemin (e, f). Semiquantification showed that although more than 80% of both disc stem cells were positively stained indicating nucleostemin at passage 5 (g), about 10% of AFSCs and 23% of NPSCs were stained indicating nucleostemin in cell nuclei (b, d, and g), the other cells released nucleostemin to cytoplasm (b, d, and g), and more than 11% of AFSCs were negatively stained showing nucleostemin (b, g). However, only 2.4% of NPSCs were negatively stained for nucleostemin (d, g). Inset images were the enlarged images in the respective square. Bar: 100 μm.

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