Intermittent Cyclic Mechanical Tension‐induced Down‐regulation of Ectonucleotide Pyrophosphatase Phosphodiesterase 1 Gene Expression is Mainly Dependent on TGF‐β1 in End‐plate Chondrocytes

Abstract

To investigate the relationship between ectonucleotide pyrophosphatase phosphodiesterase-1(ENPP-1) expression and transforming growth factor beta 1 (TGF-β1) of end-plate chondrocytes after stimulation with intermittent cyclic mechanical tension (ICMT) by using an FX-4000T Flexercell Tension Plus unit. Rat end-plate chondrocytes were cultured and ICMT (strain at 0.5 Hz sinusoidal curve at 10% elongation) applied for 7 days for 4 h/day and cultured for a further 2 days. End-plate chondrocytes were also exposed to 10 ng/mL of TGF-β1. Then, using small interfering RNA technology, small interfering TGF-β1 (siTGF-β1) was transfected. Expression of ENPP-1 and TGF-β1 was measured by real-time reverse-transcriptase polymerase chain reaction (RT-PCR) and western blotting. Expression of both ENPP-1 and TGF-β1 was up-regulated after ICMT. Both RT-PCR and western blot showed that ENPP-1 expression decreases with siRNA TGF-β1 after 3% elongation 40 min, and cultured for an additional 2 days. It was found that down-regulation of ENPP-1 gene expression induced by ICMT is likely dependent on TGF-β1 in end-plate chondrocytes.