Differing responses of osteogenic cell lines to β-glycerophosphate

Abstract Ascorbic acid (Asc), dexamethasone (Dex) and β-glycerophosphate (β-Gly) are commonly used to promote osteogenic behaviour by osteoblasts in vitro. According to the literature, several osteosarcoma cells lines appear to respond differently to the latter with regards to proliferation kinetics and osteogenic gene transcription. Unsurprisingly, these differences lead to contrasting data between publications that necessitate preliminary studies to confirm the phenotype of the chosen osteosarcoma cell line in the presence of Asc, Dex and β-Gly. The present study exposed Saos-2 cells to different combinations of Asc, Dex and β-Gly for 14 days and compared the response with immortalised human mesenchymal stromal/stem cells (MSCs). Cell numbers, cytotoxicity, mineralised matrix deposition and cell proliferation were analysed to assess osteoblast-like behaviour in the presence of Asc, Dex and β-Gly. Additionally, gene expression of runt-related transcription factor 2 (RUNX2); osteocalcin (OCN); alkaline phosphatase (ALP); phosphate regulating endopeptidase homolog X-linked (PHEX); marker of proliferation MKI67 and proliferating cell nuclear antigen (PCNA) was performed every two days during the 14-day cultures. It was found that proliferation of Saos-2 cells was significantly decreased by the presence of β-Gly which contrasted with hMSCs where no change was observed. Furthermore, unlike hMSCs, Saos-2 cells demonstrated an upregulated expression of late osteoblastic markers, OCN and PHEX that suggested β-Gly could affect later stages of osteogenic differentiation. In summary, it is important to consider that β-Gly significantly affects key cell processes of Saos-2 when using it as an osteoblast-like cell model

Manual versus powered toothbrushes for oral health; an update

Background: Plaque removal is a cornerstone in the prevention and treatment of periodontal diseases. Powered toothbrushes have been devised to assist in plaque removal. An earlier Cochrane systematic review found that only powered toothbrushes with a rotation-oscillation action were more effective at removing plaque and reducing gingivitis. That review requires updating to include recent trials. Objective: To compare the effects of manual and powered toothbrushes on plaque removal and gingival health. Method: We searched the Cochrane Oral Health Group Trials Register, CENTRAL; MEDLINE, EMBASE and CINAHL to 9 March 2011. Manufacturers and authors were contacted for additional data. Trials were selected for random allocation of participants to use a manual or powered toothbrush. Participants were members of the public with uncompromised manual dexterity who brushed unsupervised for at least 4 weeks. There was no language restriction. Primary outcomes were plaque and gingivitis scores at the end of the trial. Assessment of methodological quality and data extraction were conducted in duplicate. Potential sources of heterogeneity were examined, along with sensitivity analyses for quality and publication bias. Results: Fifty trials, involving 4326 participants, provided data. Effect sizes, calculated as standardized mean difference (95% confidence intervals) for brushes with a rotation oscillation action were: 1 to 3 months >3 months Plaque -0.53 (-0.74 to -0.31) -0.66 (-1.28 to -0.03) Gingivitis -0.49 (-0.73 to -0.26) -0.34 (-0.56 to -0.11) This represents approximately 27% fewer sites with bleeding on probing in the long term. No other powered designs were consistently superior to manual toothbrushes. There was considerable heterogeneity between trials. Sensitivity analyses revealed the results to be robust when selecting trials of high quality. Conclusion: Rotation-oscillation powered toothbrushes remove plaque and reduce gingivitis more than manual brushes in the short and long term

Traditional multiwell plates and petri dishes limit the evaluation of the effects of ultrasound on cells in vitro

Ultrasound accelerates healing in fractured bone; however, the mechanisms responsible are poorly understood. Experimental setups and ultrasound exposures vary or are not adequately characterized across studies, resulting in inter-study variation and difficulty in concluding biological effects. This study investigated experimental variability introduced through the cell culture platform used. Continuous wave ultrasound (45 kHz; 10, 25 or 75 mW/cm2, 5 min/d) was applied, using a Duoson device, to Saos-2 cells seeded in multiwell plates or Petri dishes. Pressure field and vibration quantification and finite-element modelling suggested formation of complex interference patterns, resulting in localized displacement and velocity gradients, more pronounced in multiwell plates. Cell experiments revealed lower metabolic activities in both culture platforms at higher ultrasound intensities and absence of mineralization in certain regions of multiwell plates but not in Petri dishes. Thus, the same transducer produced variable results in different cell culture platforms. Analysis on Petri dishes further revealed that higher intensities reduced vinculin expression and distorted cell morphology, while causing mitochondrial and endoplasmic reticulum damage and accumulation of cells in sub-G1 phase, leading to cell death. More defined experimental setups and reproducible ultrasound exposure systems are required to study the real effect of ultrasound on cells for development of effective ultrasound-based therapies not just limited to bone repair and regeneration

Traditional multiwell plates and petri dishes limit the evaluation of the effects of ultrasound on cells in vitro

Ultrasound accelerates healing in fractured bone; however, the mechanisms responsible are poorly understood. Experimental setups and ultrasound exposures vary or are not adequately characterized across studies, resulting in inter-study variation and difficulty in concluding biological effects. This study investigated experimental variability introduced through the cell culture platform used. Continuous wave ultrasound (45 kHz; 10, 25 or 75 mW/cm2, 5 min/d) was applied, using a Duoson device, to Saos-2 cells seeded in multiwell plates or Petri dishes. Pressure field and vibration quantification and finite-element modelling suggested formation of complex interference patterns, resulting in localized displacement and velocity gradients, more pronounced in multiwell plates. Cell experiments revealed lower metabolic activities in both culture platforms at higher ultrasound intensities and absence of mineralization in certain regions of multiwell plates but not in Petri dishes. Thus, the same transducer produced variable results in different cell culture platforms. Analysis on Petri dishes further revealed that higher intensities reduced vinculin expression and distorted cell morphology, while causing mitochondrial and endoplasmic reticulum damage and accumulation of cells in sub-G1 phase, leading to cell death. More defined experimental setups and reproducible ultrasound exposure systems are required to study the real effect of ultrasound on cells for development of effective ultrasound-based therapies not just limited to bone repair and regeneration