ABSTRACT
BACKGROUND:The reported time of bone marrow mesenchymal stem cel s induced to differentiate into chondrocytes is different. Few studies have observed and compared the cel s’ dynamic transformation during the induction process. OBJECTIVE:To observe the dynamic differentiation and the mature time of rabbit bone marrow mesenchymal stem cel s which were directional y induced to chondroblasts for 8, 11, 14, 17, 20 days. METHODS:Bone marrow was aspirated from the femur of New Zeal rabbits, and bone marrow mesenchymal stem cel s were isolated by gradient centrifugation. After cultivation and amplification, bone marrow mesenchymal stem cel s at passage 3 were directional y induced to chondrocytes by the serum-free medium containing transforming growth factor beta-1. The experiments were divided into five groups according to different induction time points:8 days, 11 days, 14 days, 17 days, 20 days. Then cel ular morphology, toluidine blue staining, typeⅡ col agen immunohistochemistry, aggrecan content in induction medium, and chondrogenic differentiation in each group were observed and compared. RESULTS AND CONCLUSION:Bone marrow mesenchymal stem cel s had apparently transformed in morphology at 8 days of induction, and presented obvious chondrocytes’ morphology at 14 days. The aggrecan in induction medium could be detected at a low level at 4 days, significantly increased at 8 days, and maintained slow increasing at 20 days. At 14 days, the metachromatic particles could be found by toluidine blue staining, and the col agen type Ⅱimmunohistochemistry was significantly positive in cel climbing slice. Experimental findings indicate that, bone marrow mesenchymal stem cel s that are monolayer cultured in a high density can be induced into chondroblasts at the effect of transforming growth factor beta-1 and other factors. There are a few chondroblasts in the early induction process, then cel s begin to have chondrocytes morphology and function after induced for 8 days, and may differentiate to mature chondrocytes at 14 days. In addition, they can keep a high biological activity in the induction process.