Syndecan-4 Gene Expression in Osteoblasts on Fibronectin Coated Titanium

Abstract

Coating the titanium (Ti) surface with cell-adhesive proteins such as fibronectin (FN) improves initial cell attachment and supports osteoblastic cell differentiation. A cell-adhesive functional domain in FN, Arg-Gly-Asp (RGD), is known to be a binding motif with osteoblast integrin. Both FN and Gly-Arg-Gly-Asp-Ser-Pro (GRGDSP) peptides were coated on Ti surfaces, on which osteoblastic cells, MC3T3-E1, were cultured. Total RNA was isolated from both cells and the gene expression levels were analyzed using the Affymetrix GeneChip system. Most gene expression levels were similar between FN- and GRGDSP-coated on Ti, but a small number of genes were expressed differently. Elevated mRNA levels of the syndecan-4 (SDC4) gene were observed in MC3T3-E1 on FN-coated Ti (Fn-Ti) compared to GRGDSP-coated Ti (GRGDSP-Ti), as confirmed by reverse transcription-polymerase chain reaction (RT-PCR) and real-time PCR. Since the fibroblast growth factor (FGF) family plays major roles in osteogenesis and SDC is known to promote the binding and FGF signaling, the elevated SDC4 on FN-Ti disks may help osteoblastic differentiation. FN has not only an RGD domain, but also binding domains of fibrin, heparin and collagen; a higher SDC4 gene expression may be induced by these binding domains not RGD domain. These binding domain peptides may be useful in the further development of biomaterial modified Ti implants using synthetic peptides.