Effect of Interleukin-1b on Syndecan Family Expression in Osteosarcoma Cells

Objectives: Bone cells are regulated by interaction with growth factors and components of the extracellular matrix. Syndecans are transmembrane heparan sulfate proteoglycans known to bind both other extracellular matrix molecules and certain growth factors, thus playing a unique role as a regulator of growth factor behavior. In this study, we investigated mRNA expression of syndecan family in osteosarcoma cells exposed to interleukin (IL)-1b as a bone resorptive agent. Methods: The human osteoblastic osteosarcoma cell line, SaOS-2, was used for this experiment. The subconfluent cells, which cultured in DMEM containing low concentration of FCS, showed high alkaline phosphatase activity. Total RNA was extracted from the cultured cells 3-48 hr after IL-1b addition. The mRNA expression level was measured using real-time quantitative RT-PCR technique. Results: RT-PCR analysis demonstrated the expression of transcripts for syndecan-1, -2 and -4. The expression levels in the non-stimulated control cells were syndecan-2, syndecan-4 and syndecan-1 in descending order. When osteosarcoma cells were incubated with IL-1b, there was a significant decrease in mRNA level for syndecan-2 at 12 hr. In contrast, the expression of syndecan-4 was markedly increased at 3 hr followed by a gradual decrease over 48 hr. There appeared to be no overall changes in syndecan-1. Conclusions: These results demonstrate that syndecan-1, -2 and -4 are synthesized in human osteoblastic osteosarcoma cells, and syndecan-4 gene transcription is rapidly responsive to an inflammatory mediator. Hence, it is indicated that the controlled expression of syndecan family may be important in the regulation of osteoblastic function.