ABSTRACT
This study investigated the effects of ultrasound (US) at different frequencies on fracture healing over a three-week period in a rabbit fibular fracture model. Forty-five adult New Zealand White rabbits were divided into five groups: a control group and four groups treated with US frequencies of 0.5, 1.0, 1.5 and 2.0 MHz (0.5 W/cm(2), 200-µs burst, pulsed 1:4). After anesthesia, transverse osteotomy was performed on the fibula bone. This was followed by intravital staining and fluorescence microscopic examination of new bone formation and biomechanical tests of torsional stiffness at the osteotomy site. Results showed that total new bone formation and torsional stiffness of the fibula were greater in all US-treated groups than in the control group. No significant difference was found between any of the four US-treated groups. The US treatment also enhanced bone growth of the sham-treated contralateral fracture site. These results suggest that US treatment at 0.5, 1.0, 1.5 or 2.0 MHz can enhance fracture healing in a rabbit model. Furthermore, the effects of US on fracture healing at present parameters might not be confined locally.
Subject(s)
Fibula , Fracture Healing/radiation effects , Ultrasonic Therapy , Animals , Biomechanical Phenomena , Disease Models, Animal , Male , Microscopy, Fluorescence , Osteotomy , Rabbits , Random Allocation , Staining and Labeling , Statistics, Nonparametric , TorqueABSTRACT
We report the fluorescent labeling of osteoblast cells using the biocompatible hydroxyapatite (HA) grown with nucleating seed of hydrophilic CdSe/ZnS quantum dots (QDs) allowing the real-time observation of cell under confocal microscope. We found that the MC3T3-E1 osteoblast cells can engulf HA with surface-tailored QDs showing fluorescent spots in the cytoplasm, while HA and QDs nanoparticles were not engulfed. It is interesting to see that the fluorescence was only displayed in the cytoplasm of MC3T3-E1 osteoblast cells. It can be envisioned that the nano-sized hydroxyapatite bearing fluorescent QD can only be internalized in the cytoplasm. Therefore, it is worth utilizing these composite particles to observe cellular physiology with minimal toxicity to the osteoblast cells.
Subject(s)
Cadmium Compounds/metabolism , Durapatite/chemistry , Nanoparticles/chemistry , Osteoblasts/cytology , Quantum Dots , Selenium Compounds/metabolism , Sulfides/metabolism , Zinc Compounds/metabolism , 3T3 Cells , Animals , Biological Transport , Cadmium Compounds/chemistry , Cell Survival , Durapatite/metabolism , Fluorescence , Mice , Microscopy, Confocal , Nanoparticles/ultrastructure , Osteoblasts/metabolism , Selenium Compounds/chemistry , Staining and Labeling/methods , Sulfides/chemistry , Zinc Compounds/chemistryABSTRACT
We use an in-vitro osteoblast cell culture model to investigate the effects of low-frequency (7.5 Hz) pulsed electromagnetic field (PEMF) stimulation on osteoblast population, cytokines (prostaglandin E(2) (PGE(2)), transforming growth factor beta1(TGFbeta1), and alkaline phosphatase (ALP) activity to find the optimal intensity of PEMF for osteoblast growth. The results demonstrate that PEMF can stimulate osteoblast growth, release of TGFbeta1, and, in addition, an increase of ALP activity. The synthesis and release of PGE(2) in the culture medium are reduced with increasing numbers of cells. Higher intensity does not necessarily mean increased osteoblast growth, and the most efficient intensity is about 2 mV/cm in this case. Although the lower intensities of the PEMF are yet to be determined, the results of this study can shed light on the mechanisms of PEMF stimulation on non union fracture therapy and osteoporosis prevention in the future.
Subject(s)
Cytokines/metabolism , Osteoblasts/physiology , Osteoblasts/radiation effects , Animals , Animals, Newborn , Cell Proliferation/radiation effects , Cell Survival/radiation effects , Cells, Cultured , Dose-Response Relationship, Radiation , Electromagnetic Fields , Gene Expression/physiology , Gene Expression/radiation effects , Radiation Dosage , Rats , Rats, WistarABSTRACT
This study compares the mechanisms of ultrasound (US) on osteoblast proliferation with those of pulsed electromagnetic field (PEMF), by different signal transduction pathway inhibitors. The cells were stimulated for 15 min under US or for 2 h under PEMF exposure. Twenty-four h after the beginning of stimulation, the cells were harvested and used for mitochondrial activity test (MTT) analysis. The results showed that there are different transduction pathways for US and PEMF stimulation that lead to an upgrade of osteoblast proliferation, although their pathways all lead to an increase in cytocolic Ca2+ and activation of calmodulin. These findings offer a biochemical mechanism to support the process of ultrasound and PEMF-induced enhanced healing of bone fractures.
