A Dominant Negative Cadherin Inhibits Osteoblast Differentiation

• Published in: Journal of bone and mineral research Vol. 15; no. 12; pp. 2362 - 2370
• Main Authors: Cheng, Su‐Li, Shin, Chan Soo, Towler, Dwight A., Civitelli, Roberto
• Format: Journal Article
• Language: English
• Published: Washington, DC John Wiley and Sons and The American Society for Bone and Mineral Research (ASBMR) 01.12.2000; American Society for Bone and Mineral Research
• Subjects: Alkaline Phosphatase - metabolism; Animals; Biological and medical sciences; Blotting, Northern; Blotting, Western; bone formation; Bone Matrix - metabolism; cadherin; Cadherins - genetics; Cadherins - metabolism; Calcification, Physiologic; Cell Adhesion; cell adhesion molecules; Cell Differentiation; Down-Regulation; Fundamental and applied biological sciences. Psychology; Glyceraldehyde-3-Phosphate Dehydrogenases - metabolism; In Vitro Techniques; Integrin-Binding Sialoprotein; Mice; osteoblast differentiation; Osteoblasts - enzymology; Osteoblasts - metabolism; Osteocalcin - metabolism; Osteopontin; RNA, Messenger - metabolism; Sialoglycoproteins - metabolism; Skeleton and joints; Up-Regulation; Vertebrates: osteoarticular system, musculoskeletal system; Rodentia; Cell adhesion molecule; Cadherin; Adhesion; Ossification; Osteoarticular system; Vertebrata; Cell line; Mammalia; Mouse; Animal; Osteoblast; Bone; Inhibition; Differentiation
• ISSN: 0884-0431; 1523-4681
• DOI: 10.1359/jbmr.2000.15.12.2362

We have previously indicated that human osteoblasts express a repertoire of cadherins and that perturbation of cadherin‐mediated cell‐cell interaction reduces bone morphogenetic protein 2 (BMP‐2) stimulation of alkaline phosphatase activity. To test whether inhibition of cadherin function interferes with osteoblast function, we expressed a truncated N‐cadherin mutant (NCadδC) with dominant negative action in MC3T3‐E1 osteoblastic cells. In stably transfected clones, calcium‐dependent cell‐cell adhesion was decreased by 50%. Analysis of matrix protein expression during a 4‐week culture period revealed that bone sialoprotein, osteocalcin, and type I collagen were substantially inhibited with time in culture, whereas osteopontin transiently increased. Basal alkaline phosphatase activity declined in cells expressing NCadΔC, relative to control cells, after 3 weeks in culture, and their cell proliferation rate was reduced moderately (17%). Finally,45Ca uptake, an index of matrix mineralization, was decreased by 35% in NCadΔC‐expressing cells compared with control cultures after 4 weeks in medium containing ascorbic acid and β‐glycerophosphate. Similarly, BMP‐2 stimulation of alkaline phosphatase activity and bone sialoprotein and osteopontin expression also were curtailed in NCadΔC cells. Therefore, expression of dominant negative cadherin results in decreased cell‐cell adhesion associated with altered bone matrix protein expression and decreased matrix mineralization. Cadherin‐mediated cell‐cell adhesion is involved in regulating the function of bone‐forming cells.