Osteoblasts generate an osteogenic microenvironment when grown on surfaces with rough microtopographies

Osteoblasts respond to microarchitectural features of their substrate. On smooth surfaces (tissue culture plastic, tissue culture glass, and titanium), the cells attach and proliferate but they exhibit relatively low expression of differentiation markers in monolayer cultures, even when confluent. When grown on microrough Ti surfaces with an average roughness (Ra) of 4-7 µm, proliferation is reduced but differentiation is enhanced and in some cases, is synergistic with the effects of surface microtopography. In addition, cells on microrough Ti substrates form hydroxyapatite in a manner that is more typical of bone than do cells cultured on smooth surfaces. Osteoblasts also respond to growth factors and cytokines in a surface-dependent manner. On rougher surfaces, the effects of regulatory factors like 1alpha,25(OH)<inf>2</inf>D<inf>3</inf> or 17beta-estradiol are enhanced. The response to the surface is mediated by integrins, which signal to the cell through many of the same mechanisms used by growth factors and hormones. Studies using PEG-modified surfaces indicate that increased differentiation may be related to altered attachment to the surface. When osteoblasts are grown on surfaces with chemistries or microarchitectures that reduce cell attachment and proliferation, and enhance differentiation, the cells tend to increase production of factors like TGF-beta1 that promote osteogenesis while decreasing osteoclastic activity. Thus, on microrough Ti surface, osteoblasts create a microenvironment conducive to new bone formation

Influence of novel nano-mesoporous bioactive glass on the regulation of IGF-II gene expression in osteoblasts

To investigate whether the mesoporous bioactive glass (MBG) exerts any in vitro bioactivity on rat osteoblasts and the potential regulatory mechanism of this bioactivity. Rat osteoblasts were incubated in the presence and absence (control) of ionic dissolution product of MBG in minimal essential medium. The osteoblast proliferation and differentiation were measured using MTT and alkaline phosphatase methods. The IGF-II mRNA expression in osteoblasts was measured by RT-PCR. IGF-II protein and IGFBP were measured by ELISA. The level of alkaline phosphatase activity was increased to 125% of control. Expression of IGF-II mRNA was increased to 125% of control. There was a 175 and 237% increase in the concentration of unbound IGF-II protein and IGFBP, respectively, in the conditioned media of treated osteoblasts. The osteoblast proliferation was 92% of control. The ionic dissolution product of MBG was able to promote the differentiation of osteoblasts, probably by inducing IGF-II expression at both mRNA and protein level