Glycosylation of DMP1 Is Essential for Chondrogenesis of Condylar Cartilage

Abstract

The mandibular condylar cartilage (MCC) shoulders force for the subchondral bone during mastication. The cartilage matrix contains various large molecules, such as type I, II, and X collagens and proteoglycans (PGs), which jointly play essential roles in maintaining cartilage characteristics. PGs play key roles in maintaining the elasticity of cartilage and providing a cushion against mastication forces. In addition to the well-known PGs, DMP1-PG, which is the PG form of dentin matrix protein 1 (DMP1), is a newly identified PG. DMP1 is proteolytically processed in vivo, and the N-terminus is glycosylated into its PG form-that is, DMP1-PG, which is highly expressed not only in tooth and bone but also in the matrix of the MCC. However, the specific functions of DMP1-PG in the MCC remain unclear. In human temporomandibular joint osteoarthritis and hyperocclusion model rat specimens, PGs are significantly downregulated, and DMP1-PG is the most prominently affected PG. To further investigate the role of DMP1-PG in condylar chondrogenesis, a glycosylation site mutant (S-G) mouse model was established with knock-in methods. In the MCC of the S89G-DMP1 mice, the glycosylation level of DMP1 was significantly downregulated, and a series of abnormal developmental and pathologic changes could be observed. The morphologic changes included thinner cartilage layers, deformations of the MCC, and disordered arrangements of the chondrocytes, and an earlier onset of temporomandibular joint osteoarthritis-like changes was observed. In addition, markers of chondrogenesis were downregulated, and the matrix of the MCC displayed OA phenotypes in the S89G-DMP1 mice. Further investigations showed that the transforming growth factor β signaling molecules were affected in the MCC after the loss of DMP1-PG. In addition, the loss of DMP1-PG significantly accelerated the progression of cartilage injuries in the hyperocclusion models. Given these findings, we investigated the significant role of DMP1-PG in the chondrogenesis and maintenance of MCC.

Aberrant Fluid Shear Stress Contributes to Articular Cartilage Pathogenesis via Epigenetic Regulation of ZBTB20 by H3K4me3

“…We adopted OARSI Score criteria to evaluate cartilage degeneration as previously stated. 23 For immunohistochemistry assay, after being deparaffinized and rehydrated, samples were immersed in 0.3% hydrogen peroxide to block endogenous peroxidase activities. Subsequently, samples were incubated with proteinase K for antigen retrieval after which blocked with 1% goat serum plus 3% BSA solution.…”

Glycosylation of DMP1 maintains cranial sutures in mice

“…Cranial skulls around sutures disserted from 1‐month‐old wild‐type and DMP1‐S89G mice were ground into homogenate by automatic homogeniser (Tissuelyser‐24, Jingxin). The homogenate was added into 1 mL 6 mol/L urea solution (PH = 7.3), and then, the sample mixtures were incubated under 4℃ for 24 hours to extract protein into the solution 23. After subjected to SDS‐PAGE, the protein components were transferred to nitrocellulose filter (NC) membranes.…”

“…The homogenate was added into 1 mL 6 mol/L urea solution (PH = 7.3), and then, the sample mixtures were incubated under 4℃ for 24 hours to extract protein into the solution. 23 After subjected to SDS-PAGE, the protein components were transferred to nitrocellulose filter (NC) membranes. The membranes were blocked with 5% BSA and then incubated with β-actin antibody (ab8226, Abcam) and…”

CircGCN1L1 promotes synoviocyte proliferation and chondrocyte apoptosis by targeting miR-330-3p and TNF-α in TMJ osteoarthritis

“…After hematoxylin counterstaining, 1% alcohol differentiation, and dehydration, use neutral gum to cover the slides. The positively stained cells were counted, and the percentage was calculated by Image-J 1.52t 25 .…”