Low Intensity Pulsed Ultrasound Promotes the Extracellular Matrix Synthesis of Degenerative Human Nucleus Pulposus Cells through FAK/PI3K/AktPathway.

Abstract
STUDY DESIGN:
In vitroexperimental study OBJECTIVE.: To investigate the effect of low intensity pulsed ultrasound (LIPUS) on the extracellular matrixsynthesis of degenerative human nucleus pulposus cells and explorethe molecular mechanism.
SUMMARY OF BACKGROUND DATA:
LIPUS has been used successfully for bone fracture healing and been proved to be effective instimulatingextracellular matrix metabolismin animal intervertebraldisc cells.However, whether LIPUS also exerts an anabolic effect on degenerative human nucleus pulposuscells and the possible molecular mechanism is yet unclear.
METHODS:
The degenerative human nucleus pulposus cells were cultured in calcium alginate beads. In the LIPUS group, cells were exposed to an average temporal intensity of 30 mW/cm2 and a frequency of 1.5 MHz of LIPUS 20 minutesdaily for 1 week. The control group wascultured in the same way but without LIPUS stimulation. The LY294002 group was stimulated by LIPUS and treated with LY294002 simultaneously.The expression of aggrecan, collagen-II, Sox9, tissue inhibitor of metalloproteinase-1and matrix metalloproteinase-3were evaluated by ELISA, western blot orRT-PCR. Expression of signaling proteins involved in FAK/PI3K/Akt pathway was studied by Western blot analysis.
RESULTS:
LIPUS significantly upregulated expression of aggrecan, collagen-II, Sox9 and tissue inhibitor of metalloproteinase-1 compared to control group, but inhibited secretion ofmatrix metalloproteinase-3. The study further demonstrated thatthe upregulation of aggrecan, collagen-II and Sox9 was related to the activation of FAK/PI3K/Akt pathwaycaused by LIPUS. And inhibition of PI3K/Akt significantly suppressed the special biologicaleffectactivated byLIPUS.
CONCLUSION:
LIPUS promotes the extracellular matrix synthesis of degenerative human nucleus pulposus cells through activation of FAK/PI3K/Akt pathway.
PMID: 26571160 [PubMed - as supplied by publisher]