Discoidin Domain Receptor-1 Gene Expression of Osteoblasts on Fibronectin Coated Titanium Disks

Abstract

Enhancement of osteoblastic adhesion and migration on a titanium (Ti) surface increases the successful rate of osseointegration in implant therapy by stimulating osteoblastic differentiation. It has been reported that Ti surfaces coated with fibronectin (FN) or GRGDSP peptide derived from FN had improved initial cell attachment and supported osteoblastic cell differentiation. However, the differences in gene expression by osteoblasts grown on FN and GRGDSP coated Ti disks have not been elucidated. Ti disks were coated with FN or GRGDSP peptide, then MC3T3-E1 osteoblastic cells were cultured on those surfaces. After 15 days, the levels of gene expression of the cells were examined. Those levels were mostly similar between the FN and GRGDSP coated disks, though that of discoidin domain receptor-1 (DDR-1) was significantly greater in cells cultured on the FN coated disks. The elevated mRNA level of the DDR-1 gene was then confirmed by reverse transcription-polymerase chain reaction (RT-PCR) and real-time PCR assays. In addition to the ability of the RGD domain to bind with integrins, FN also binds to fibrillin, proteoglycan, and collagen by their specific binding domains, thus the higher level of DDR-1 gene expression seen in our experiments may have been induced by those and not by the RGD domain. For future developing biomaterial as coating for Ti implants using synthetic peptides, binding domains other than the RGD domain in FN may be useful and important.