Objective To investigate the role of bone morphogenetic protein 2 (BMP-2) combined with hypoxic microenvironment in chondrogenic phenotype differentiation of bone marrow mesenchymal stem cells (BMSCs) of rat in vitro. Methods BMSCs were harvested from 4-week-old female Sprague Dawley rats. BMSCs at passage 2 were divided into 4 groups according different culture conditions: normoxia control group (group A), normoxia and BMP-2 group (group B), hypoxia control group (3% oxygen, group C), and hypoxia and BMP-2 group (group D). Then the cellular morphology was observed under inverted phase contrast microscope. Alcian blue immunohistochemical staining was used to detect the glycosaminoglycans (GAG), Western blot to detect collagen type II and hypoxia-inducible factor 1α (HIF-1α), and RT-PCRto detect the expressions of chondrogenic related genes, osteogenic related genes, and hypoxia related genes. Results At 21 days after induction of BMP-2 and hypoxia (group D), BMSCs became round, cell density was significantly reduced, and lacuna-l ike cells were wrapped in cell matrix, while the changes were not observed in groups A, B, and C. Alcian blue staining in group D was significantly bluer than that in other groups, and staining became darker with induction time, and the cells were stained into pieces of deeply-stained blue at 21 days. Light staining was observed in the other groups at each time point. The expression level of collagen type II protein in group D was significantly higher than those in other groups (P lt; 0.05). HIF-1α protein expression levels of groups C and D were significantly higher than those of groups A and B (P lt; 0.05). The expressions of collagen II α1 (COL2 α1) and aggrecan mRNA (chondrogenic related genes) were highest in group D, while the expressions of COL1 α1, alkaline phosphatase, and runt-related transcri ption factor 2 mRNA (osteogenic related genes) were the highest in group B (P lt; 0.05). Compared with groups A and B, HIF-1α (hypoxic related genes) in groups C and D significantly increased (P lt; 0.05). Conclusion BMP-2 combined with hypoxia can induce differentiation of BMSCs into the chondrogenic phenotype, and inhibit osteoblast phenotype differentiation. HIF-1α is an important signaling molecule which is involved in the possible mechanism to promote chondrogenic differentiation process.
Objective To observe the effect of pilose antler polypeptides(PAP)on the apoptosis of rabbit marrow mesenchymal stem cells (MSCs) differentiated into chondrogenic phenotype by interleukin 1β (IL-1β) so as to optimize the seeding cells in cartilage tissue engineering. Methods The MSCs were separated from the nucleated cells fraction of autologus bone marrow by density gradient centrifuge and cultured in vitro. The MSCs were induced into chondrogenic phenotype by transforming growth factor β1(TGF-β1) and basic fibroblast growth factor(bFGF). According to different medias, the MSCs were randomly divided into four groups: group A as black control group, group B(100 ng IL-1β)，group C(10 μg/ml PAP+100 ng IL-1β) and group D(100 ng/ml TGF-β1 +100 ng IL-1β). The samples were harvested and observed by morphology, flow cytometry analysis, RT-PCR and ELISA at 24, 48 and 72 hours. Results The intranuclear chromatin agglutinated into lump and located under nulear membranes which changed into irregular shapeat 24 hours. The intranuclear chromatin agglutinated intensifily at 48 hours. Then the nucear fragments agglutinated into apoptosic corpuscles at 72 hours in group B. The structure change of cells in groups C and D was later than that in group B, and the number of cells changed shape was fewer than that in group B. The structure change of cells in group A was not significant. The apoptosic rate of cells, the mRNA expression of Caspase-3 and the enzymatic activity of Caspase-3 gradually increased in group B, and there were significant differences compared with groups A,C and D(Plt;0.01). Conclusion Caspase-3 is involved in aoptosis of the MSCs differentiated into chondrogenic phenotype cultured in vitro. PAP could prevent from or reverse apoptosis of these MSCs by decreasing the expression of Caspase-3 and inhibiting the activity of Caspase-3.