Silicon substituted hydroxyapatite (SiHA) has been reported to produce faster bone in- growth in vitro compared to hydroxyapatite (HA). The mechanism by which silicate ions in these materials trigger bone growth and differentiation remains unclear. In vitro models were used in this thesis to investigate human osteoblast cell responses on exposure to silicon containing materials and silicate ion solutions. The amounts of serum protein bound to SiHA was significantly higher than that in HA (p<O.OOl). Culture of both primary human osteoblast (HOB) cells and an osteosarcoma cell line (MG-63 cells) showed that SiHA discs were biocompatible to the cells; flat cell morphologies, higher degree of cellular processes, and a covering with minuscule bone mineral-like crystals were observed. To elucidate the effects of silicate ions alone on osteoblast functions, a 1000 ppm standard silicon solution was supplemented into cell culture medium to produce silicate ion concentration of 20 and 500 ~M; it was found that the former had little effect on both cell types. Significant increases in levels of total DNA (p<0.001), protein (p<0.001), and collagen (p<0.001) were observed in HOB cells, but not in MG-63 cells, in cultures with 500 ~M silicate ions. Likewise, expression of COL-J al (p<0.001), BMP-2 (p<0.05), PHOSPHO-J (p<0.001) genes were up-regulated in both cells types cultured with 500 ~M silicate ions. Further studies proposed that the activation of cell proliferation by this silicate ion-containing medium, observed as increases in total DNA, involved TGF~1 and/or IGF-I receptors. In trying to understand this, it was latterly identified that the pH changes of the serum- supplemented culture medium that occurred during supplementation with the alkali silicate ion solution and subsequent neutralisation with HCI were the actual cause of the marked enhancement in HOB cell proliferation. Silicate ions did still appear to have a direct effect on some HOB cell responses, due to observing comparable effects of 20 and 500 ~M silicate ions on e.g. TNAP and PHOSPHO-J gene expression, compared to silicate ion-free controls.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:553827 |
| Date | January 2011 |
| Creators | Ruangsuriya, Jetsada |
| Publisher | University of Aberdeen |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=179546 |
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