INTRODUCTION: In vitro and in vivo studies show that titanium implants with physical‐chemical modifications like micron/sub‐micron scale topographies increase osteoblast differentiation, local factor production, bone formation around the implant, and decrease healing time. Polyetheretherketone (PEEK) is used as a cage/spacer for vertebral interbody fusion to maintain spinal alignment and segmental stability while facilitating bony fusion. The aim of the present study was to elucidate whether common intervertebral materials such as PEEK and titanium induce osteoblast maturation and generate an osteogenic environment.
METHODS: MG63 cells were cultured on tissue culture polystyrene (TCPS), PEEK, smooth [sTiAlV, Sa<90nm], or rough [rTiAlV, Sa=1.81μm] TiAlV surfaces. Gene expression was measured by qPCR. Cell number, alkaline phosphatase activity (ALP), and secreted OCN, OPG, TGF‐β1, BMP2, BMP4, and BMP7 were analyzed. Data are mean±SEM (n=6/condition), analyzed by ANOVA with Bonferroni's Student's t‐test.
RESULTS: Expression of ITGA1, ITGA2, ITGAV, and ITGB1 mRNA was higher on sTiAlV and rTiAlV than on TCPS or PEEK. BMP2, BMP4, and NOG mRNA were downregulated on PEEK and upregulated on sTiAlV in comparison to TCPS; highest expression was on rTiAlV. GREM1 was upregulated on PEEK, but similar on TiAlV compared to TCPS. Cell number decreased and ALP, OCN, BMP2, BMP4, BMP7, and TGF‐β1 increased on sTiAlV and rTiAlV, but cell response to PEEK was not different from TCPS. OPG was higher on PEEK and sTiAlV than TCPS, but highest on rTiAlV.
DISCUSSION: These results indicate that osteoblasts on TiAlV surfaces present a more mature phenotype than osteoblasts grown on PEEK. Cells on TiAlV, but not PEEK, produce an osteogenic environment. Osteoblasts cultured on TiAlV produce and regulate BMP pathway molecules, increasing BMP2, BMP4, BMP7, and BMP inhibitors. The results demonstrate that TiAlV surfaces modulate osteoblast maturation and regulate BMP production.