ABSTRACT
BACKGROUND: Under indirect co-culture conditions, chondrocytes can induce bone marrow mesenchymal stem cells to differentiate into chondrocytes. Osteocytes are the seed cells of chondrocytes, but co-culture of osteocytes with chondrocytes is rarely reported. OBJECTIVE: To induce the chondrogenic differentiation of periosteum-derived cells (PDCs) by indirect co-culture with chondrocytes. METHODS: Chondrocytes were isolated from the rabbits by trypsin and collagenase Ⅱ digestion. Rabbit PDCs were obtained by the explants culture method. Passage 2 chondrocytes and PDCs underwent indirect co-culture at 1:1 in Transwell system as experimental group. PDCs cultured alone were as control group. After 2 weeks of culture, the cellular morphological changes were observed by inverted contrast phase microscope. The expression levels of collagen type Ⅱ and proteoglycan were detected by collagen type Ⅱ immunohistochemistry and toluidine blue staining. The mRNA expression levels of proteoglycan, collagen type Ⅱ and SRY-related protein-9 were detected by RT-PCR. RESULTS AND CONCLUSION: After 2 weeks of culture, PDCs in the experimental group were gradually transformed to chondrocyte-like cells, while PDCs in the control group still remained long spindle-shaped. Collagen type Ⅱ immunohistochemistry staining and toluidine blue staining were positive in the experimental group, while the results were negative in the control group. Additionally, RT-PCR results indicated that the relative mRNA expression levels of proteoglycan, collagen type Ⅱ and SRY-related protein-9 in the experimental group were significantly higher than those in the control group. Therefore, chondrocytes can induce PDCs to differentiate into chondrocytes under indirect co-culture conditions.