Inhibitory effects of activin-a on osteoblast differentiation during cultures of fetal rat calvarial cells

✍ Scribed by Takashi Ikenoue; Seiya Jingushi; Ken Urabe; Ken Okazaki; Yukihide Iwamoto

• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: English
• Weight: 266 KB
• Volume: 75
• Category: Article
• ISSN: 0730-2312
• DOI: 10.1002/(sici)1097-4644(19991101)75:2<206::aid-jcb3>3.0.co;2-t

✦ Synopsis

Activin-A is a member of the transforming growth factor-␤ (TGF-␤) superfamily and is expressed by osteoblasts. However, the role of activin-A on osteoblasts is not clearly understood. We examined the effects of activin-A on osteoblast proliferation or differentiation, and mineralization by the osteoblasts in the first subcultures of fetal rat osteoblasts obtained from calvarial bones. Exogenous activin-A led to impaired formation of bone nodules in a dose-dependent manner, although it did not influence cell proliferation using an MTT assay. This inhibitory effect depended upon the time at which activin-A was added to the culture media, and the effect was most significant when addition took place at the early phase of the culture. In addition, exogenous activin-A inhibited gene expression of type I procollagen, alkaline phosphatase, osteonectin, and osteopontin in the cultured cells using Northern blot analysis. The peak of osteocalcin mRNA was delayed. Gene expression for TGF-␤ was not influenced by exogenous activin-A. The ␤A subunit (activin-A) mRNA was detected during the early phase of this culture. These results indicate that activin-A inhibited early differentiation of the fetal rat calvarial cells, or osteoblasts.