The Adhesion Behaviour of Primary Human Osteoblasts and Fibroblasts on Polyetheretherketone Versus Titanium Under Induced Inflammatory Conditions - A Pilot Study

Introduction: The previous standard material for bone implants is titanium and its composite materials. The high rigidity of titanium causes compressive forces to be transmitted unchanged to the surrounding bone. A possible alternative is the plastic polyetheretherketone (PEEK), which also has a high biocompatibility and a comparable bone strength. The aim of this in vitro pilot study was to analyse the viability, morphology, and adhesion behaviour of human osteoblasts and fibroblasts on PEEK versus titanium surfaces. The focus of this study was on an induced inflammatory condition by incubation with the bacterial toxin lipopolysaccharide (LPS; 10μg / ml, 24 hours). Primary human osteoblasts (NHOst, LONZA) and fibroblasts (NHDF, PromoCell) were cultured on titanium and PEEK samples from MEDICON. The viability testing of the cells on the two materials compared to PLL-coated glass coverslips (reference) was carried out by MTT method. To examine the growth behaviour of the two cell types on the different materials, SEM images were taken. Real-time PCR measurements were used to analyse gene expression of the LBS binding protein (LBP) and the LPS receptor (TLR4). The detection at the protein level and additionally of phalloidin (actin detection) and vinculin (ECM binding protein) was carried out by immunocytochemical (ICC) labelling. Results: The osteoblasts and fibroblasts had the highest viability on the coverslips, followed by the titanium and PEEK samples. In the SEM images, the two cell types on PEEK surfaces showed comparable adhesion properties to titanium. After LPS stimulation, significantly increased LBP gene expression was found in the NHOst. This could also be seen at the protein level after growth on the three materials. While no increased mRNA concentration in the NHOst could be detected under LPS incubation for TLR4, a marked increase in the antibody response on all materials was observed in the ICC markers. For fibroblasts, LPS stimulation had no effect on their LBP and TLR4 gene / protein expression. Under control conditions, the NHOst grew on all materials with parallel actin fibers. After LPS incubation, the osteoblasts contracted. In particular on the coverslips, a punctual intensification of the adhesive contacts was observed. After LPS incubation of the NHDF, the coverslips and titanium samples showed a redistribution of the vinculin detection from perinuclear to the periphery of the cell processes. Discussion: The material PEEK has proven to be highly histologically compatible with the standard material titanium. Like titanium, human osteoblasts and fibroblasts can be colonized on PEEK samples even under pro-inflammatory conditions (LPS). Further studies are needed to clarify whether the material PEEK is suitable as material for dental implants. Keywords: Adhesive behaviour, Osteoblasts, Fibroblasts, PEEK, Lipopolysaccharide