Behaviour of moderately differentiated osteoblast-like cells cultured in contact with bioactive glasses

Abstract

Bioactive glasses have been shown to stimulate osteogenesis both in vivo and in vitro. However, the molecular mechanisms underlying this process are still poorly understood. In this study, we have investigated the behaviour of osteoblast-like cells (MG63), cultured in the presence of bioglass particles. Three types of granules were used: 45S5 ® bioactive glass, 45S5 ® granules preincubated in tris buffer and 60S non-reactive glass, used as control. Phase contrast microscopy permitted step-by-step visualization of cell cultures in contact with the particles. Ultrastructural observations of undecalcified sections revealed direct contacts of the cells and an electron-dense layer located at the periphery of the material. Protein synthesis was evaluated biochemically and showed a gradual increase throughout the culture time in the three types of cultures. Alkaline phosphatase was detected in situ, in clusters of packed cells either in contact with the material or in the background cell layer. Semi-quantitative RT-PCR analysis of the main osteoblastic markers showed that gene expression was maintained in all three cultures. The fact that osteocalcin was not detected, supports the fact that the MG63 cell line is composed of less differentiated osteogenic cells rather than mature osteoblasts. We also demonstrated for the first time in this cell line, the expression of Msx-2, Dlx-3 and Dlx-7 homeogenes, known to regulate in vivo foetal skeletogenesis as well as adult skeletal regeneration. However, no significant differences could be recognised in the expression pattern of bone markers between the three types of cultures. Yet these preliminary results indicate that bioactive glasses provided a suitable environment for the growth and proliferation of osteoblasts in vitro, since no drastic changes in phenotype expression of pre-osteoblasts was noted.

The in vivo behaviour of a sol–gel glass and a glass-ceramic during critical diaphyseal bone defects healing

“…A positive effect of bioactive glasses on attachment, proliferation, differentiation and mineralisation of bone cells, compared to non-reactive surfaces has been demonstrated in vitro [25], but the knowledge about the cellular and molecular events underlying is scarce [26]. In our study, both bioactive materials allow healing of critical diaphyseal bone defects in rabbits.…”

“…Results indicate that there are considerable differences in healing potential between the control group and the groups that received cylinders of both types, showing an adequate viability of receiver bone, with absence of inflammatory response around implants as evidence of an adequate in vivo bioactivity [1]. Some bioactive glass compositions (o55 mol% of SiO 2 ) exhibit a high bioactive index and osteoconductivity, and are able to induce osteoproduction by stimulating the proliferation of osteoprogenitor cells [26]. Both tested materials showed osseointegration evidences, and bone growth over its surfaces and subsequent remodelling attempts include cylinders in a new-formed bone diaphysis.…”

The modulation of tissue-specific gene expression in rat nasal chondrocyte cultures by bioactive glasses

“…A number of previous studies have shown that certain bioactive glasses can promote proliferation and differentiation of osteoblasts in vitro [4,[6][7][8]19,20]. However, to our knowledge, this is the first report concerning the ability of bioactive glasses to promote differentiation and matrix mineralization in a chondrocyte cell culture system.…”

Role of non-canonical Wnt signaling in osteoblast maturation on microstructured titanium surfaces

“…MG63 cells do not calcify their extracellular matrix under the culture conditions that we used [24,25]. Osteoblasts and precursor cells can be induced to mineralize by treating them with osteogenic media containing combinations of beta-glycerophosphate, ascorbic acid and dexamethasone [26–28], but addition of these factors was an additional variable that had potential to obscure the specific roles of each Wnt protein in osteoblast differentiation.…”