Effect of hydrogel elasticity and ephrinB2-immobilized manner on Runx2 expression of human mesenchymal stem cells.

The objective of this study is to design the manner of ephrinB2 immobilized onto polyacrylamide (PAAm) hydrogels with varied elasticity and evaluate the effect of hydrogels elasticity and the immobilized manner of ephrinB2 on the Runx2 expression of human mesenchymal stem cells (hMSC). The PAAm hydrogels were prepared by the radical polymerization of acrylamide (AAm), and N,N'-methylenebisacrylamide (BIS). By changing the BIS concentration, the elasticity of PAAm hydrogels changed from 1 to 70kPa. For the bio-specific immobilization of ephrinB2, a chimeric protein of ephrinB2 and Fc domain was immobilized onto protein A-conjugated PAAm hydrogels by making use of the bio-specific interaction between the Fc domain and protein A. When hMSC were cultured on the ephrinB2-immobilized PAAm hydrogels with varied elasticity, the morphology of hMSC was of cuboidal shape on the PAAm hydrogels immobilized with ephrinB2 compared with non-conjugated ones, irrespective of the hydrogels elasticity. The bio-specific immobilization of ephrinB2 enhanced the level of Runx2 expression. The expression level was significantly high for the hydrogels of 3.6 and 5.9kPa elasticity with bio-specific immobilization of ephrinB2 compared with other hydrogels with the same elasticity. The hydrogels showed a significantly down-regulated RhoA activity. It is concluded that the Runx2 expression of hMSC is synergistically influenced by the hydrogels elasticity and their immobilized manner of ephrinB2 immobilized. STATEMENT OF SIGNIFICANCE: Differentiation fate of mesenchymal stem cells (MSC) is modified by biochemical and biophysical factors, such as elasticity and signal proteins. However, there are few experiments about combinations of them. In this study, to evaluate the synergistic effect of them on cell properties of MSC, we established to design the manner of Eph signal ligand, ephrinB2, immobilized onto polyacrylamide hydrogels with varied elasticity. The gene expression level of an osteogenic maker, Runx2, was enhanced by the immobilized manner, and significantly enhanced for the hydrogels of around 4kPa elasticity with bio-specific immobilization of ephrinB2. This is the novel report describing to demonstrate that the Runx2 expression of MSC is synergistically influenced by the hydrogels elasticity and their manner of ephrinB2 immobilized.

Effects of fluoride-modified titanium surfaces with the similar roughness on RUNX2 gene expression of osteoblast-like MG63 cells.

Chemical modification of titanium surfaces by hydrofluoric acid (HF) is an effective method to improve bone responses on titanium implant surfaces. In this study, titanium disks were sandblasted with titanium oxide grits and modified with 0.2% and 0.4% of diluted HF under different exposure times of 40 and 60 s. Surface characteristics, such as surface chemical composition, surface topography, and surface wettability, were investigated. To examine MG63 osteoblast-like cell responses to fluoride-modified titanium surfaces with roughness similar to that of nonmodified surfaces, a cell proliferation assay was performed and gene expression levels of Runx2 were evaluated using real-time PCR. Fluoride-modified titanium surfaces revealed no significant roughness difference but with hydrophilic properties than control group SB. Moreover, the relative atomic concentration percentages of fluoride were 0.7, 1.5, and 2.8. As fluoride concentrations increased, surface wettability increased and cell proliferation began earlier. However, the gene expression levels of Runx2 increased earlier on surfaces with 1.5% fluoride, with significantly high surface skewness. There seems to be an optimal fluoride concentration percentage when gene expression levels of Runx2 were taken into consideration. In addition, surface parameters, such as surface wettability and surface skewness, seem to be important factors in the enhancement of osteoblast differentiation by HF. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 3102-3109, 2017.

Trabecular titanium can induce in vitro osteogenic differentiation of human adipose derived stem cells without osteogenic factors.

Trabecular Titanium (TT) is an innovative highly porous structure that imitates the morphology of trabecular bone with good mechanical properties. Adipose-derived stem cells are a multipotent cell population that can be used in regenerative medicine, in particular, for bone therapeutic applications. The ability of TT to induce the osteogenic differentiation of human adipose derived stem cells (hASCs) in the absence of osteogenic factors was evaluated using molecular biological, biochemical, and immunohistochemical methods. At 7 and 21 days from differentiation, the hASCs grown on TT scaffolds showed similar expressions of alkaline phosphatase (ALP) and Runx-2 both in the presence and in the absence of osteogenic factors, as well as at transcript and protein levels. hASCs cultured on monolayer in the presence of the medium obtained from the wells where hASCs/scaffold constructs were cultured in the absence of osteogenic factors differentiated towards the osteogenic phenotype: their gene and protein expression of ALP and Runx-2 was similar to that of the same cells cultured in the presence of osteogenic factors, and significantly higher than that of the ones cultured in growth medium.