Low-intensity pulsed ultrasound stimulates matrix metabolism of human annulus fibrosus cells mediated by transforming growth factor β1 and extracellular signal-regulated kinase pathway.

Abstract
Abstract Purpose: There are limited strategies to restore the damaged annulus fibrosus of the intervertebral disc. Low-intensity pulsed ultrasound has positive effects on the proliferation of several types of cells and the repair of damage tissue in vivo. However, scientific evidence of therapeutic effects of low-intensity pulsed ultrasound on annulus fibrosus cells remains limited. The purpose of this study is to evaluate the feasibility of applying low-intensity pulsed ultrasound to the repair of the annulus fibrosus. Materials and Methods: We used an in vitro model of human annulus fibrosus cells subjected to low-intensity pulsed ultrasound stimulation to examine its effects on cell proliferation and matrix metabolism. Cell viability, synthesis of collagen and glycosaminoglycan, expression of matrix metalloproteinases and transforming growth factor β1, and pathways involving mitogen-activated protein kinases were investigated. Results: Low-intensity pulsed ultrasound significantly enhanced proliferation of annulus fibrosus cells after 5 days of treatment. Low-intensity pulsed ultrasound with an intensity of 0.5 W/cm2 increased the collagen and glycosaminoglycan synthesis and decreased the expressions of matrix metalloproteinase -1 and -3 of human annulus fibrosus cells. Real-time polymerase chain reactions and western blotting analysis revealed that low-intensity pulsed ultrasound could increase transforming growth factor β1 (TGF- β1) and activate extracellular signal-regulated kinase (ERK) pathway. In addition, transforming growth factor β receptor kinase inhibitor could suppress the ultrasound-induced alterations in cell viability and matrix metabolism. Conclusions: The findings suggested that low-intensity pulsed ultrasound could be useful as a physical stimulation of cell metabolism for the repair of the annulus fibrosus.
KEYWORDS:
TGF-β1; annulus fibrosus; collagen; glycosaminoglycan; low-intensity pulsed ultrasound; matrix metalloproteinase
PMID: 25658041