Tingting Lan1, Hanchi Zhao2, Bilu Xiang2, Jun Wang3, Yang Liu4. 1. Department of Orthodontics, State Key Laboratory of Oral Diseases, National Clinical Research Center for Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu 610041, China. 2. Department of Prosthetics, State Key Laboratory of Oral Diseases, National Clinical Research Center for Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu 610041, China. 3. Department of Orthodontics, State Key Laboratory of Oral Diseases, National Clinical Research Center for Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu 610041, China. Electronic address: Wangjunv@163.com. 4. TMJ Department, State Key Laboratory of Oral Diseases, National Clinical Research Center for Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu 610041, China. Electronic address: Liu.yang.dds.phd@gmail.com.
Abstract
OBJECTIVE: Previous studies found bone resorption and chondrocytes loss in mouse models of mid-palatal suture when given continuous compressive force, although chondrocytes response remained unknown. Herein, we design this study to determine how continuous compression force induces chondrocytes apoptosis. METHODS: Thirty C57BL/6 male mice (aged 6 weeks) were randomly assigned into controls (not ligated to a spring), blank controls (ligated with no compression) and the compression group (ligated with 20-g compression). After 4 d, palatal tissues were sampled and stained by TB and safranin-O. Tunel staining measured the percentage of apoptotic chondrocytes, and immunohistochemistry was performed to label apoptosis-associated proteins (e.g., Bcl-2, Bcl-xl, Bax, Bak, Bid, Bad, caspase-3, caspase-8 and caspase-9). Intergroup comparison was made by the rank sum test, and P < 0.05 was defined as statistical significance. RESULTS: After 7d of induction, TB and safranin-O staining revealed that the cartilage area in the compression group was significantly decreased, while the control group remained largely unaltered. Tunel staining showed that apoptotic cell numbers in the mid-palatal suture were significantly higher than the control group. Immunohistochemistry showed that mice in the compression group had significantly increased expression of caspase-3, caspase-9, Bad, Bak, Bax and Bid; However, caspase-8 remained unaltered. No expression of Bcl-2 and Bcl-xl was detected. CONCLUSIONS: Continuous compression force induces chondrocytes apoptosis in the mid-palatal suture. This process might be associated with the mitochondrial pathway.
OBJECTIVE: Previous studies found bone resorption and chondrocytes loss in mouse models of mid-palatal suture when given continuous compressive force, although chondrocytes response remained unknown. Herein, we design this study to determine how continuous compression force induces chondrocytes apoptosis. METHODS: Thirty C57BL/6 male mice (aged 6 weeks) were randomly assigned into controls (not ligated to a spring), blank controls (ligated with no compression) and the compression group (ligated with 20-g compression). After 4 d, palatal tissues were sampled and stained by TB and safranin-O. Tunel staining measured the percentage of apoptotic chondrocytes, and immunohistochemistry was performed to label apoptosis-associated proteins (e.g., Bcl-2, Bcl-xl, Bax, Bak, Bid, Bad, caspase-3, caspase-8 and caspase-9). Intergroup comparison was made by the rank sum test, and P < 0.05 was defined as statistical significance. RESULTS: After 7d of induction, TB and safranin-O staining revealed that the cartilage area in the compression group was significantly decreased, while the control group remained largely unaltered. Tunel staining showed that apoptotic cell numbers in the mid-palatal suture were significantly higher than the control group. Immunohistochemistry showed that mice in the compression group had significantly increased expression of caspase-3, caspase-9, Bad, Bak, Bax and Bid; However, caspase-8 remained unaltered. No expression of Bcl-2 and Bcl-xl was detected. CONCLUSIONS: Continuous compression force induces chondrocytes apoptosis in the mid-palatal suture. This process might be associated with the mitochondrial pathway.