Osteoblast proliferation correlates with cell morphology on dental implants and is modulated by surface parameters 


Background: Topographical and chemical properties of oral implant surfaces are critical parameters influencing initial cell response like cell adhesion and proliferation at biomaterial interfaces and play a crucial role for tissue integration during implant healing. Therefore, current research focuses on characterizing the cell function modulation by cell/biomaterial interactions to design implant surfaces that favor fast and stable osseointegration.

Aim: The present study aimed at examining early response of implant-relevant target cells, namely primary human osteoblasts derived from alveolar bone (AO), to ceria- and yttria-stabilized zirconia (Ce/Y-TZP) biomaterials with different surface modifications by examining cell attachment, morphology and proliferation.

Methods: Biomaterial disks used for cell culture involved micro-roughened Ce- and Y-TZP-surfaces with different topographies and one chemical modification with CaP. Surface topographies of the biomaterials were analyzed by scanning electron microscopy (SEM) and interferometry (IFM). Morphology and cell attachment of AO were examined by SEM and morphometry using fluorescence-based actin cytoskeleton staining at day 1 and 7. At the same time points cell proliferation was examined by DNA quantification and metabolic alamarBlue assay. Statistical evaluation of the quantitative data was performed using one-way ANOVA or Kruskal-Wallis ANOVA followed by Tukey´s HSD test and Dunn´s test respectively.

Results: At day 1 osteoblast functions were irrespectively of the chemical biomaterial composition mainly modulated by surface topography: Thereby, the osteoblasts showed increased cell spreading and proliferation on slightly-roughened surfaces when compared with rough biomaterials. This topography-dependent difference was however no longer detectable at day 7. Instead, osteoblast functions seemed rather to depend on surface chemistry at that time since cell spreading and proliferation reached higher values on Ce-TZP than on Y-TZP. These results suggest that cellular functions were modulated by surface topography and chemistry in a time-dependent manner. Furthermore, our results revealed an interdependence of cell morphology and proliferation. The correlation between cell surface area and proliferation did not follow a linear function but showed that by exceeding a critical cell size, AO showed a switch in their proliferation behavior which was characterized by a sharp increase in proliferation.

Conclusions and clinical implications: We could demonstrate that morphogenesis and proliferation of AO are influenced in a biomaterial- and time-dependent manner.  Since we could further show that proliferation of AO is a function of AO morphology, we could outline that cellular behavior on oral implant surfaces can be influenced by designing surfaces that induce cell morphologies favoring cell growth and thus improved implant healing. Therefore, investigation of cell morphology seems to be an easy and efficient method in the process of preclinical evaluation of novel biomaterials to assess further behavior of cells.

The research was supported by the European Community's Seventh Framework Programme (grant agreement n 280741).