Physically enhanced coating of a titanium plasma-spray surface with human SAOS-2 osteoblasts and extracellular matrix

On the quantification of local power densities in a new vibration bioreactor

We investigate the power densities which are obtainable locally in a vibration bioreactor. These reactor systems are of great relevance for research about oncological or antibacterial therapies. Our focus lies on the local liquid pressure caused by resonance vibration in the fluid contained by the reactor's petri dish. We use for the excitation one piezoelectric patch which offer advantages concerning controllability and reproducibility, when compared to ultrasound. The experimental work is extended by finite element analyses of bioreactor details. The peaks of the vibration response for water, sodium chloride (0.1N Standard solution), and McCoy's 5A culture medium are in good alignment. Several natural frequencies can be observed. Local power density can reach multiple times the magnitude used in ultrasound studies. Based on the observed local power densities, we are planning future work for the exposure of cell cultures to mechanical vibration.

In Vitro Production of Calcified Bone Matrix onto Wool Keratin Scaffolds via Osteogenic Factors and Electromagnetic Stimulus

Pulsed electromagnetic field (PEMF) has drawn attention as a potential tool to improve the ability of bone biomaterials to integrate into the surrounding tissue. We investigated the effects of PEMF (frequency, 75 Hz; magnetic induction amplitude, 2 mT; pulse duration, 1.3 ms) on human osteoblast-like cells (SAOS-2) seeded onto wool keratin scaffolds in terms of proliferation, differentiation, and production of the calcified bone extracellular matrix. The wool keratin scaffold offered a 3D porous architecture for cell guesting and nutrient diffusion, suggesting its possible use as a filler to repair bone defects. Here, the combined approach of applying a daily PEMF exposure with additional osteogenic factors stimulated the cells to increase both the deposition of bone-related proteins and calcified matrix onto the wool keratin scaffolds. Also, the presence of SAOS-2 cells, or PEMF, or osteogenic factors did not influence the compression behavior or the resilience of keratin scaffolds in wet conditions. Besides, ageing tests revealed that wool keratin scaffolds were very stable and showed a lower degradation rate compared to commercial collagen sponges. It is for these reasons that this tissue engineering strategy, which improves the osteointegration properties of the wool keratin scaffold, may have a promising application for long term support of bone formation in vivo.

Short Exposures to an Extremely Low-Frequency Magnetic Field (ELF MF) Enhance Protein but not mRNA Alkaline Phosphatase Expression in Human Osteosarcoma Cells

Background

Among electromagnetic fields treatments used in orthopedics, extremely low-frequency magnetic fields (ELF MF) need more detailed information about the molecular mechanisms of their effects and exposure conditions.

Objective

Evaluation of the effects of an ELF MF exposure system, recently introduced among current clinical treatments for fracture healing and other bone diseases, on Alkaline Phosphatase (ALP) activity and expression in a human osteosarcoma cell line (SaOS-2), as marker typically associated to osteogenesis and bone tissue regeneration.

Method

Cells were exposed to the ELF MF physical stimulus (75 Hz, 1.5 mT) for 1h. Cell viability, enzymatic activity, protein and mRNA expression of alkaline phosphatase were then measured at different times after exposure (0, 4 and 24 h).

Results

Data demonstrate that this signal is active on an osteogenic process already one hour after exposure. Treatment was, in fact, capable, even after an exposure shorter than those commonly used in clinical applications, to significantly up-regulate alkaline phosphatase enzymatic activity. This regulation is produced essentially through an increase of ALP protein level, without changes of its mRNA concentration, while assessed magnetic field did not affect cell growth and viability and did not produce temperature variations.

Conclusion

Tested low-frequency magnetic field affects cellular ALP expression with a posttranslational mechanism, without the involvement of regulations at gene transcription and mRNA level. This molecular effect is likely produced even within treated tissues during therapies with this signal and may be implicated in the induction of observed effects in treated patients.

Ultrasound stimulus to enhance the bone regeneration capability of gelatin cryogels

In the present study, gelatin-based cryogels have been seeded with human SAOS-2 osteoblasts. In order to overcome the drawbacks associated with in vitro culture systems, such as limited diffusion and inhomogeneous cell-matrix distribution, this work describes the application of ultrasounds (average power, 149 mW; frequency, 1.5 MHz) to physically enhance the cell culture in vitro. The results indicate that the physical stimulation of cell-seeded gelatin-based cryogels upregulates the bone matrix production.