"BACKGROUND:
Low-intensity pulsed ultrasound (LIPUS) regiment has been used to treat fractures with non-union and to promote bone union in general. The effect of LIPUS on articular cartilage metabolism has been characterized. Yet, the effect of LIPUS to repair articular cartilage injury remains unclear in vivo.
METHODS:
We designed a study to investigate the effect of LIPUS on articular cartilage repairing in a rabbit severe cartilage injury model. Eighteen rabbits were divided into three groups: Sham-operated group, operated group without-LIPUS-treatment, operated group with-LIPUS-treatment (a daily 20-minute treatment for 3 months). Full-thickness cartilage defects were surgically created on the right side distal femoral condyle without intending to penetrate into the subchondral bone, which mimicked severe chondral injury. MR images for experimental joints, morphology grading scale, and histopathological Mankin score were evaluated.
RESULTS:
The preliminary results showed that the operated groups with-LIPUS-treatment and without-LIPUS-treatment had significantly higher Mankin score and morphological grading scale compared with the sham-operated group. However, there was no significant difference between the with-LIPUS-treatment and without-LIPUS-treatment groups. Cartilage defects filled with proliferative tissue were observed in the with-LIPUS-treatment group grossly and under MR images, however which presented less up-take under Alcian blue stain. Furthermore, no new deposition of type II collagen or proliferation of chondrocyte was observed over the cartilage defect after LIPUS treatment.
CONCLUSION:
LIPUS has no significant therapeutic potential in treating severe articular cartilage injury in our animal study."
" (A) The Sham group: Intact osteochondral architecture was shown. The surface of cartilage layer is smooth and the arrangement of chondrocyte is well. (B) The without-LIPUS-treatment group: The cartilage layer was thin because of lack of superficial zone, intermediate zone and radial zone of cartilage layer. Irregular surface without proliferative layer was shown (arrow). (C) The with-LIPUS-treatment group: The layers of superficial zone, intermediate zone and radial zone were lost over the cartilage defect, instead of deposition of acellular tissue layer (arrow). SZ: superficial zone; IZ: intermediate zone; RZ: radial zone; CZ: calcification zone; SB: subchondral bone."
Chondrocyte primary cilium is mechanosensitive and responds to low-intensity-ultrasound by altering its length and orientation.
"The primary cilium has been implicated in mechanotransduction, however, its mechanosensory role in transducing signals under low-intensity ultrasound (LIUS) which has the potential to repair fractures and cartilage, remains uninvestigated. This study examined the impact of continuous-wave US, at the cell resonance frequency of 5.0MHz and pressure amplitude of either 14 or 60kPa, on the incidence, length and orientation of primary cilium in bovine articular chondrocytes. Visualization of primary cilium with acetylated α-tubulin staining demonstrated that the primary cilium was elongated, bent under US and these changes were reversible. Basal expression of phospho-ERK1/2 was lower in deciliated chondrocytes, thus implicating the role for the primary cilium in transducing signals via the MAPK/ERK pathway. This study demonstrates that the chondrocyte primary cilium is mechanosensitive and responds to US by altering its length and orientation."
[Low-intensity pulsed ultrasound promotes extracellular matrix synthesis of human osteoarthritis chondrocytes].
"Objective To investigate the effect of low-intensity pulsed ultrasound (LIPUS) on the extracellular matrix synthesis of human osteoarthritis (OA) chondrocytes and explore the underlying mechanism. Methods Human osteoarthritis chondrocytes were collected from abandoned articular cartilage. Then the cells were cultured and identified by toluidine blue staining and immunocytochemical staining of type 2 collagen. The passage 2 cells were randomly divided into 3 groups: control OA group, 30 mW/cm2 LIPUS-treated OA group, 30 mW/cm2 LIPUS combined with 5 μmol/L LY294002-treated OA group. LIPUS treatment was performed for 20 minutes per day, totally 7 days. The mRNA levels of Col2, aggrecan and matrix metalloprotease 13 (MMP-13) were determined by quantitative real-time PCR. The protein levels of Col2, aggrecan, Akt, p-Akt and MMP-13 were evaluated by Western blotting. Results Compared with the control OA group, the expressions of Col2 and aggrecan at both mRNA and protein levels significantly increased, and MMP-13 significantly reduced in the LIPUS-treated OA group. The p-Akt protein level was significantly elevated after LIPUS stimulation, but there was no significant difference in the Akt protein levels between the two groups. Moreover, LY294002, an inhibitor of PI3K/Akt, significantly suppressed the biological effect activated by LIPUS. Conclusion LIPUS enhances the synthesis and inhibits the degradation of the extracellular matrix in human osteoarthritis chondrocytes."
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OBJECTIVES:
Cartilage is a highly mechano-responsive tissue. Chondrocytes undergo a series of complex changes, including proliferation and metabolic alteration as the target of external biomechanical and biochemical stimuli. IL-1β is known to regulate chondrocyte metabolism and plays an important role in the pathogenesis of osteoarthritis (OA). The objective of this study was to employ low-intensity pulsed ultrasound (LIPUS) as a localized mechanical stimulus and assess its effects on chondrocyte migration, proliferation, metabolism, and differentiation, as well as its ability to suppress IL-1β mediated catabolism in cartilage.
METHODS:
Human cartilage explants and chondrocytes were stimulated by LIPUS in the presence and absence of IL-1β to asses cartilage degradation, chondrocytes metabolism, migration, and proliferation. Western blot analyses were conducted to study IL-1β the associated NFκB pathway in chondrocytes.
RESULTS:
LIPUS stimulation increased the proteoglycan content in human cartilage explants and inhibited IL-1β induced loss of proteoglycans. LIPUS stimulation increased rates of chondrocyte migration and proliferation, and promoted chondrogenesis in mesenchymal stem cells (MSC). Further, LIPUS suppressed IL-1β induced activation of phosphorylation of NFκB-p65 and IĸBα leading to reduced expression of MMP13 and ADAMT5 in chondrocytes.
CONCLUSIONS:
Collectively, these data demonstrate the potential therapeutic effects of LIPUS in preventing cartilage degradation and treating OA via a mechanical stimulation that inhibits the catabolic action of IL-1β and stimulates chondrocyte migration, proliferation, and differentiation."
OBJECTIVES:
Cartilage is a highly mechano-responsive tissue. Chondrocytes undergo a series of complex changes, including proliferation and metabolic alteration as the target of external biomechanical and biochemical stimuli. IL-1β is known to regulate chondrocyte metabolism and plays an important role in the pathogenesis of osteoarthritis (OA). The objective of this study was to employ low-intensity pulsed ultrasound (LIPUS) as a localized mechanical stimulus and assess its effects on chondrocyte migration, proliferation, metabolism, and differentiation, as well as its ability to suppress IL-1β mediated catabolism in cartilage.
METHODS:
Human cartilage explants and chondrocytes were stimulated by LIPUS in the presence and absence of IL-1β to asses cartilage degradation, chondrocytes metabolism, migration, and proliferation. Western blot analyses were conducted to study IL-1β the associated NFκB pathway in chondrocytes.
RESULTS:
LIPUS stimulation increased the proteoglycan content in human cartilage explants and inhibited IL-1β induced loss of proteoglycans. LIPUS stimulation increased rates of chondrocyte migration and proliferation, and promoted chondrogenesis in mesenchymal stem cells (MSC). Further, LIPUS suppressed IL-1β induced activation of phosphorylation of NFκB-p65 and IĸBα leading to reduced expression of MMP13 and ADAMT5 in chondrocytes.
CONCLUSIONS:
Collectively, these data demonstrate the potential therapeutic effects of LIPUS in preventing cartilage degradation and treating OA via a mechanical stimulation that inhibits the catabolic action of IL-1β and stimulates chondrocyte migration, proliferation, and differentiation."
"Low-intensity pulsed ultrasound (LIPUS) has been studied frequently for its beneficial effects on the repair of injured articular cartilage. We hypothesized that these effects are due to stimulation of chondrogenic progenitor cell (CPC) migration toward injured areas of cartilage through focal adhesion kinase (FAK) activation. CPC chemotaxis in bluntly injured osteochondral explants was examined by confocal microscopy, and migratory activity of cultured CPCs was measured in transwell and monolayer scratch assays. FAK activation by LIPUS was analyzed in cultured CPCs by Western blot. LIPUS effects were compared with the effects of two known chemotactic factors: N-formyl-methionyl-leucyl-phenylalanine (fMLF) and high-mobility group box 1 (HMGB1) protein. LIPUS significantly enhanced CPC migration on explants and in cell culture assays. Phosphorylation of FAK at the kinase domain (Tyr 576/577) was maximized by 5 min of exposure to LIPUS at a dose of 27.5 mW/cm(2) and frequency of 3.5 MHz. Treatment with fMLF, but not HMBG1, enhanced FAK activation to a degree similar to that of LIPUS, but neither fMLF nor HMGB1 enhanced the LIPUS effect. LIPUS-induced CPC migration was blocked by suppressing FAK phosphorylation with a Src family kinase inhibitor that blocks FAK phosphorylation. Our results imply that LIPUS might be used to promote cartilage healing by inducing the migration of CPCs to injured sites, which could delay or prevent the onset of post-traumatic osteoarthritis."