Osteoblast Attachment, Proliferation and Differentiation on Implant Surfaces

Abstract

Introduction. Countless numbers of implants with different surface treatment techniques exist commercially around the world. Cell adhesion, proliferation and differentiation on all these different implant surfaces have different effects at the microscopic level.

Purpose. The purpose of this project is to expand on previous osteoblast attachment studies and investigate the osteoblast attachment, proliferation, and differentiation on five different types of implant surfaces: (1) Machined surface of surface roughness (Sa) of 0.3 – 0.4 µm; (2) Anodized yellow surface 0.3 – 0.5 µm; (3) anodized yellow surface 0.8 µm; (4) SLA surface of 1.6 µm; and (5) Biodenta surface treated (BST) surface of 1 µm. BST surface (Biodenta Swiss AG, Berneck, Switzerland) is anodized during the manufacturing process to have an amorphous titanium oxide layer. This process allows the BST surface to have its surface roughness enhanced via open porosity to promote osteoconduction.

Materials and Method. Human fetal osteoblast stem cells were cultured for two weeks on the five different types of implant surfaces. Three genes were examined: Collagen Type 2 (COL1A2), Runt-related transcription factor 2 (RUNX2) and Osteocalcin (BGLAP) because of their role as genetic markers of osteoblast attachment, proliferation, and differentiation. The quality of the mRNA was checked with a spectrophotometer and cDNA was synthesized for quantitative RT-PCR. Genes were analyzed by means of melting curve analysis and relative quantitative Ct calculation to determine fold change.

Results. The anodized 0.3 – 0.5 µm surface displayed up-regulation of COL1A2 (n-fold of +1.589) but down-regulation of RUNX2 and BGLAP (n-fold of -1.109 and -2.624, respectively). However, the anodized 0.8 µm surface presented opposite trends for all three genes. RUNX2 and BGLAP were both up-regulated (n-fold of +1.406 and +1.778, respectively) while, COL1A2 exhibited the greatest down-regulation trend with respect to all surfaces (n-fold of -4.801). The BST specimens were the only surface type to exhibit up-regulation for all three genes. Of the three genes, COL1A2 and RUNX2 displayed the greatest fold change for the BST surface (n-fold of +2.462 and +2.688, respectively).

Conclusions. mRNA expression of RUNX2, COL1A2, and BGLAP in human fetal osteoblast stem cells, cultured on five different surfaces, indicated various expression profiles. The expression of COL1A2 and BGLAP, characteristics of a more mature osteogenic phenotype, were exhibited on the rougher surface implants. Following this trend, the BST surface expressed the most mature osteogenic phenotype in this study.