Bioactive glass-induced osteoblast differentiation: a noninvasive spectroscopic study.

Here, we report on a rapid, noninvasive biophotonics system using Raman spectroscopy to detect real-time biochemical changes in foetal osteoblasts (FOBs) following exposure to 45S5 Bioglass (BG)-conditioned media. Bio-Raman spectroscopy, combined with multivariate statistical analysis techniques (principal component analysis and least squares analysis), was able to noninvasively identify biochemical differences in FOBs cultured for different time periods and between FOBs exposed/or not to BG-conditioned media. Gene and protein expression studies were also performed for known markers of osteoblastic differentiation, namely, alkaline phosphatase, bone sialoprotein, and collagen type I. Quantitative RT-PCR confirmed upregulation of genes associated with osteoblast differentiation after exposure to BG-conditioned media. These results suggest that Raman spectroscopy can noninvasively detect biochemical changes in FOBs associated with differentiation. This technique could have important applications in the field of regenerative medicine by enabling rapid characterization of cell or organoid behavior on novel bioactive scaffolds without damage to either cell or biomaterial.

Titanium dioxide (TiO(2)) nanoparticles filled poly(D,L lactid acid) (PDLLA) matrix composites for bone tissue engineering.

Titanium dioxide (TiO(2)) nanoparticles were investigated for bone tissue engineering applications with regard to bioactivity and particle cytotoxicity. Composite films on the basis of poly(D,L lactid acid) (PDLLA) filled with 0, 5 and 30 wt% TiO(2) nanoparticles were processed by solvent casting. Bioactivity, characterised by formation of hydroxyapatite (HA) on the materials surface, was investigated for both the free TiO(2) nanoparticles and PDLLA/TiO(2) composite films upon immersion in supersaturated simulated body fluid (1.5 SBF) for up to 3 weeks. Non-stoichiometric HA nanocrystals (ns-HA) with an average diameter of 40 nm were formed on the high content (30 wt% TiO(2)) composite films after 2 weeks of immersion in 1.5 SBF. For the pure PDLLA film and the low content composite films (5 wt% TiO(2)) trace amounts of ns-HA nanocrystals were apparent after 3 weeks. The TiO(2) nanopowder alone showed no bioactivity. The effect of TiO(2) nanoparticles (0.5-10,000 microg/mL) on MG-63 osteoblast-like cell metabolic activity was assessed by the MTT assay. TiO(2) particle concentrations of up to 100 microg/mL had no significant effect on MG-63 cell viability.

Gene activation by bioactive glasses.

Bioactive glasses have been shown to regulate gene expression in both hard and soft tissue repair. New resorbable bioactive glass constructs are now being developed that can influence gene expression in the local environment by manipulating material properties such as the surface chemistry, topography and the release of dissolution ions. The success of these scaffolds, however, may depend upon a greater understanding of the bioactive glass stimulated gene expression pathways. This will allow the construction of tissue specific scaffolds with tailored surface chemistry, topography and ion release rates. This paper summarises the advances made in understanding gene expression in response to bioactive glasses and discusses the future steps required for further insights into these molecular mechanisms.

Immune-dependent thrombocytopaenia in mice infected with Schistosoma mansoni.

As has been shown previously, immunologically intact mice with patent Schistosoma mansoni infections had a significantly lower mean platelet number than intact uninfected mice (P<0.0001). However, platelet numbers in T-cell deprived mice with patent infections were not significantly different from those in uninfected T-cell deprived mice. Also, platelet counts in both the infected and uninfected T-cell deprived groups were not significantly different from those in intact uninfected mice. The S. mansoni-induced thrombocytopaenia in mice is thus seemingly immune dependent. Immunologically intact mice with chronic 12-week-old S. mansoni infections had IgG antibodies that were reactive in an ELISA-type assay with whole fixed platelets of both mouse and human origin. In Western immunoblots the IgG antibodies from chronically-infected mice reacted in particular against mouse and human platelet antigens of 90, 37 and 30 kDa. Antisera raised from 2 rabbits, immunized respectively with mouse and human platelet antigens, cross-reacted with antigens of the larval, adult worm and egg stages of S. mansoni. These results support the hypothesis that an anti-platelet antibody response may be the cause of the thrombocytopaenia observed in mice with patent schistosome infections.

Does a pro-angiogenic state exist in the bone-implant interface of aseptically loosened joint prosthesis?

Neovascularization is indispensable to both bone remodeling and the development of chronic inflammation. A pro-angiogenic state in the periprosthetic tissue may augment the inflammatory response to wear debris. To investigate if a pro-angiogenic state exists in the bone-implant interface of aseptically loosened joint prosthesis, the expression of vascular endothelial growth factor (VEGF) and its receptor Flk-1/KDR were studied by immunohistochemistry. The VEGF-Flk/KDR pathway has been implicated as a key signaling requirement for pathological angiogenesis. The level of vascularization in periprosthetic tissue was semi-quantitatively compared to osteoarthritic (OA) and rheumatoid arthritic (RA) synovium. The level of vascularization in areas of periprosthetic tissue with heavy or low/moderate wear debris were also compared semi-quantitatively by image analysis. High levels of VEGF expression (16/16 cases) particularly in the implant synovial-like lining layer together with Flk-1/KDR expression by endothelial cells (13/16), suggests that neovascularization is occurring. Morphometric comparison of periprosthetic tissue with RA and OA synovium revealed no significant difference in microvessel density, but did reveal significantly increased microvessel area in RA synovium (P > 0.05). Areas of high wear debris infiltrate also contained a significantly smaller microvessel area (P > 0.01). Suggesting that wear debris may cause behavioral modification of microvessels. Modifying angiogenesis in the periprosthetic tissue could be a potential therapeutic target in reducing inflammation.