| 1. |
- Kopakkala-Tani, Milla, et al.
(author)
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Ultrasound stimulates proteoglycan synthesis in bovine primary chondrocytes.
- 2006
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In: Biorheology. - : IOS Press. - 0006-355X .- 1878-5034. ; 43:3-4, s. 271-282
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Journal article (peer-reviewed)abstract
- Mechanical forces can stimulate the production of extracellular matrix molecules. We tested the efficacy of ultrasound to increase proteoglycan synthesis in bovine primary chondrocytes. The ultrasound-induced temperature rise was measured and its contribution to the synthesis was investigated using bare heat stimulus. Chondrocytes from five cellular isolations were exposed in triplicate to ultrasound (1 MHz, duty cycle 20%, pulse repetition frequency 1 kHz) at average intensity of 580 mW/cm2 for 10 minutes daily for 1-5 days. Temperature evolution was recorded during the sonication and corresponding temperature history was created using a controllable water bath. This exposure profile was used in 10-minute-long heat treatments of chondrocytes. Heat shock protein 70 (Hsp70) levels after one-time treatment to ultrasound and heat was analyzed by Western blotting, and proteoglycan synthesis was evaluated by 35S-sulfate incorporation. Ultrasound treatment did not induce Hsp70, while heat treatment caused a slight heat stress response. Proteoglycan synthesis was increased approximately 2-fold after 3-4 daily ultrasound stimulations, and remained at that level until day 5 in responsive cell isolates. However, chondrocytes from one donor cell isolation out of five remained non-responsive. Heat treatment alone did not increase proteoglycan synthesis. In conclusion, our study confirms that pulsed ultrasound stimulation can induce proteoglycan synthesis in chondrocytes.
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| 2. |
- Leskinen, Jarkko, et al.
(author)
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Genome-wide microarray analysis of MG-63 osteoblastic cells exposed to ultrasound.
- 2008
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In: Biorheology. - : IOS Press. - 0006-355X .- 1878-5034. ; 45:3-4, s. 345-354
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Journal article (peer-reviewed)abstract
- It is well documented that low intensity pulsed ultrasound can be clinically used to accelerate bone fracture healing. Additionally, in vitro studies have shown that ultrasound can, for instance, increase mineralization, collagen production and alkaline phosphatase activity in osteoblasts. Despite the extensive research on the subject, the exact mechanism of ultrasound effect on bone cell gene regulation has not yet been deduced. In this study, we made an effort to reveal the features of genome-wide transcriptional response of osteoblast-type cells to ultrasound. MG-63 osteoblastic cell transcriptome was analyzed with whole genome microarray either 6 or 24 h after 30 min long exposure to 1.035 MHz pulsed ultrasound with three different acoustic pressures. Special attention was paid to the experimental design to minimize thermal effects and unwanted reflections of ultrasound. Microarray analysis suggested that ultrasound affects the genes involved with cellular membranes, and regulation of transcription as well. Several plasma membrane solute carriers were also regulated by ultrasound. It also changed the transcript level of several transcription factors belonging to the zinc finger proteins. However, ultrasound did not clearly promote genes involved with osteoblast differentiation.
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| 3. |
- Olkku, Anu, et al.
(author)
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Ultrasound-induced activation of Wnt signaling in human MG-63 osteoblastic cells.
- 2010
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In: Bone. - : Elsevier BV. - 8756-3282 .- 1873-2763. ; 47:2, s. 320-330
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Journal article (peer-reviewed)abstract
- The benefit from an ultrasound (US) exposure for fracture healing has been clearly shown. However, the molecular mechanisms behind this effect are not fully known. Recently, the canonical Wnt signaling pathway has been recognized as one of the essential regulators of osteoblastogenesis and bone mass, and thereby considered crucial for bone health. Mechanical loading and fluid shear stress have been reported to activate the canonical Wnt signaling pathway in bone cells, but previous reports on the effects of therapeutic US on Wnt signaling in general or in bone, in particular, have not been published yet. Therefore, activation of Wnt signaling pathway was assayed in human osteoblastic cells, and indeed, this pathway was found to be activated in MG-63 cells through the phosphoinositol 3-kinase/Akt (PI3K/Akt) and mTOR cascades following a single 10 min US exposure (2 W, 1.035 MHz). In addition to the reporter assay results, the Wnt pathway activation was also observed as nuclear localization of beta-catenin. Wnt activation showed also temperature dependence at elevated temperatures, and the expression of canonical Wnt ligands was induced under the thermal exposures. However, existence of a specific, non-thermal US component was evident as well, perhaps evidence of a potential dual action of therapeutic US on bone. Neither US nor heat exposures affected cell viability in our experiments. In summary, this is the first study to report that Wnt signaling cascade, important for osteoblast function and bone health, is one of the pathways activated by therapeutic US as well as by hyperthermia in human osteoblastic cells. Our results provide evidence for the potential molecular mechanisms behind the beneficial effects of US on fracture healing. Combinations of US, heat, and possible pharmacological treatment could provide useful flexibility for clinical cases in treating various bone disorders.
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