Objective Toreview theresearch progress of nucleus pulposus cells phenot ypic markers. Methods The domestic and international l iterature about nucleus pulposus cells phenotypic markers was reviewed extensively and summarized. Results Due to different biomechanical properties，nucleus pulposus cells and articular chondrocytes have differences in morphology and extracellular components such as the ratio of aggrecan to collagen type II α1. Nucleus pulposus cells can be identified by surface marker (CD24), gene markers (hypoxia inducible factor 1α, glucosetransporter protein 1, matrix metalloproteinase 2, vascular endothel ial growth factor A, etc), and various markers (keratin 19 and glypican 3，paired box 1, forkhead box F1 and integrin-binding sialoprotein, etc). Conclusion Nucleus pulposus cells and articular chondrocytes have different phenotypic markers, but nucleus pulposus cells are still lack of specific markers.
Objective To examine the biological characteristic changes in thededifferenciated human articular chondrocytes by the bioreactor culturing in vitvo.Methods The cartilage tissue was obtained from the joints of the adult human. The chondrocytes were isolated from the cartilage tissue with the type Ⅱ collagenase digestion（0.2%, 37℃, 3 h）and were cultured in DMEMF12 supplemented with 20% fetal bovine serum (FBS) with 1 ng/ml of TGF-β1and 5 ng/mlof FGF-2. After about 20 passages by the monolayer culture，the cells were then transferred to the bioreactor culturing of the rotational cell culture system (RCCS) for a 3-week sequence culture. The cell counting was performed with the platelet counter, and the doubling time for each passage of thecells was determined. The frozen section was stained with HE. The differentiated phenotype was evaluated by histochemistry or immunohistochemistry. Results When the monolayer culture was performed without any growth factors, the chondrocytes were rapidly proliferated within 3 passages (average doubling time, 59 h),but at the same time, dedifferentiation was also progressing rapidly. After the4th passage, most of the cells were dedifferenciated and the proliferation was decreased. With the growth factors (TGF-β1/FGF-2), the speed of the expansion was accelerated (average doubling time, 47 h), but the speed of the dedifferentiation was slowed down. After 20 passages were performed with the monolayer culture, the dedifferentiated chondrocytes could be redifferentiated when they were cultured for 3 weeks with RCCS. Then, the Safranine-O staining was bly positive for the cells, positive for aggrecan and collagen Ⅱ, but negative for collagen Ⅰ, with a wellregained phenotype. Conclusion The bioreactor culturing of the dedifferenciated human articular condrocytes can regain the differentiated phenotype and it is a useful method of obtaining the human articular chondrocytes in large amounts and in a differentiated phenotype in vitro.