Distribution of small integrin-binding ligand, N-linked glycoproteins (SIBLING) in the articular cartilage of the rat femoral head.

The small integrin-binding ligand, N-linked glycoprotein (SIBLING) family is closely related to osteogenesis. Until recently, little was known about their existence in articular cartilage. In this study, we systematically evaluated the presence and distribution of four SIBLING family members in rat femoral head cartilage: dentin matrix protein 1 (DMP1), bone sialoprotein (BSP), osteopontin (OPN), and dentin sialophosphoprotein (DSPP). First, non-collagenous proteins were extracted and then separated by ion-exchange chromatography. Next, the protein extracts eluted by chromatography were analyzed by Stains-all staining and Western immunoblotting. IHC was used to assess the distribution of these four SIBLING family members in the femoral head cartilage. Both approaches showed that all the four SIBLING family members are expressed in the femoral head cartilage. IHC showed that SIBLING members are distributed in various locations throughout the articular cartilage. The NH2-terminal fragments of DMP1, BSP, and OPN are present in the cells and in the extracellular matrix, whereas the COOH-terminal fragment of DMP1 and the NH2-terminal fragment of DSPP are primarily intracellularly localized in the chondrocytes. The presence of the SIBLING family members in the rat femoral head cartilage suggests that they may play important roles in chondrogenesis.

Expression of FAM20C in the osteogenesis and odontogenesis of mouse.

Mutations in FAM20C were recently identified as the cause of lethal osteosclerotic bone dysplasia, which highlighted the important role of this molecule in biomineralization. No systematic studies have been performed to evaluate the expression pattern of this relatively new molecule in the developmental processes of bone and tooth. In the present study, we analyzed in detail the expression profile of FAM20C during osteogenesis and odontogenesis using ISH and IHC approaches. The specimens analyzed were mouse tissues spanning embryonic day 13.5 (E13.5) to postnatal 8 weeks. The earliest presence of FAM20C was observed at E14.5. During osteogenesis, FAM20C mRNA was detected in the chondrocytes and osteoblasts of the long bone, whereas its protein was observed in the extracellular matrix (ECM) of bone and in the cytoplasm of the chondrocytes, osteoblasts, and osteocytes. During odontogenesis, FAM20C mRNA was detected in the ameloblasts, odontoblasts, cementoblasts, and periodontal ligament fibroblasts, whereas its protein was observed in the matrices of dentin, enamel, and alveolar bone and in the cytoplasm of the aforementioned cells. The temporospatial expression profile revealed in this study indicates that FAM20C is an ECM protein that may play an important role in controlling the mineralization of bone and tooth.