Osteogenic properties of hydrophilic and hydrophobic titanium surfaces evaluated with osteoblast-like cells (MG63) in coculture with human umbilical vein endothelial cells (HUVEC)

Abstract

Objectives Osteogenesis on titanium (Ti) surfaces is a complex process involving cell–substrate and cell–cell interaction of osteoblasts and endothelial cells. The aim of this study was to investigate the osteogenic properties of Ti surfaces on osteoblasts in the presence of endothelial cells (ECs). Methods Osteoblast-like cells (MG63 cells) and human umbilical vein endothelial cells (HUVECs) were grown in cocultures on four kinds of Ti surfaces: acid-etched (A), coarse-grit-blasted and acid-etched (SLA), hydrophilic A (modA) and hydrophilic SLA (modSLA) surfaces. MG63 cells in single cultures served as controls. Cell ratios and cell types in cocultures were determined and isolated using flow cytometry. Cell numbers were obtained by direct cell counting. In MG63 cells, alkaline phosphatase (ALP) activity was determined and protein levels of osteocalcin (OC) and osteoprotegerin (OPG) were detected with enzyme-linked immunosorbant assay (ELISA). The mRNA levels of ALP, OC and OPG of sorted MG63 cells were determined with real time polymerase chain reaction (PCR). Results MG63 cells proliferated in the presence of HUVECs, which showed higher cell numbers on Ti surfaces (A, SLA, modSLA) after 72 h, and lower cell numbers on Ti surfaces (modA, SLA, modSLA) after 120 h in comparison to single cultures. Protein and mRNA levels of ALP and OPG were higher in cocultures than in single cultures, while OC exhibited a lower expression. These three parameters were higher expressed on modA, SLA and modSLA surfaces compared to A surfaces. Significance Cocultures of osteoblasts and endothelial cells represent the most recently developed research model for investigating osteogenesis and angiogenesis which play both a major role in bone healing. This paper investigates for the first time the osteogenic properties of titanium surfaces used for dental implants with a coculture system with osteoblast-like cells and endothelial cells: (1) In cocultures with ECs (HUVECs) osteoblast-like cells (MG63 cells) show enhanced expression of early differentiation markers and osteogenic factors on Ti surfaces compared to single cultures of MG63 cells. (2) The differentiation and the expression of an osteogenic phenotype of osteoblast-like cells (MG63 cells) in coculture with ECs (HUVECs) is enhanced by both hydrophilicity and roughness of Ti surfaces.