Continuous pressure regulates the expression of energy metabolism related genes in rabbit annulus fibrosus

Xiaoqian XIONG; Shuhua YANG; Zengwu SHAO; Zirui ZHAN

ABSTRACT

BACKGROUND:

Recent studies have demonstrated that energy metabolism-related genes play important roles in intervertebral disc (IVD) cell adaptation to negative environmental factors, such as hypoxia and insufficiency of nutrient. But the effects of these genes in pressure-induced intervertebral disc degeneration remain uncertain.OBJECTTVE To investigate continuous pressure-induced expression of energy metabolism genes hypoxia-inducible factor 1α(HIF-lo), glucose transporter-1 (GLUT-1) and vascular endothelial growth factor (VEGF) in rabbit annulus fibrosus (AF).

DESIGN:

A randomized controlled experiment.

SETTING:

The Central Laboratory and the Laboratory of Department of Orthopaedics, Union Hospital Affiliated to Tongji Medical College, Huazhong University of Science and Technology.MATERIALS The experiment was carried out in the Central Laboratory and the Laboratory of Department of Orthopaedics, Union Hospital Affiliated to Tongji Medical College, Huazhong University of Science and Technology from May to October 2005. Twenty-five Japanese white rabbits(about 4 months old, weighting 2.5-3.0 kg, provided by the Experimental Animal Center of Tongji Medical College, Huazhong University of Science and Technology) were selected to establish the animal model.

METHODS:

A controllable pressure-induced rabbit intervertebral disc degeneration model was adopted to impose various pressured on rabbit IVDs in vivo. The survived animals whose IVDs were compressed successfully were divided randomly into 4 groups. The IVDs were treated with no pressure as control (control group), with 15 kg axial load for 24 hours (24hours group), 72 hours (72 hours group), and 24 hours with 48 hours free for self-reparation (reparation group). Reverse transcriptase-polymerase chain reaction was used to detect the expression of HIF-1α and GLUT-1. Western Blot and immunohistochemical test were carried out for the content and distribution of VEGF.MAIN OUTCOME

MEASURES:

Expression of HIF-1α and GLUT-1, content and distribution of VEGF.

RESULTS:

Twenty of 25 rabbits entered result analysis. Two rabbits were missed because of vertebral fracture, while death of 3 rabbits within 1-3 days postoperatively caused another loss. ①HIF-1α. A very low expression was detected in the control group, while the expression in the 24 hours group was raised over 20 times than that in the control group (t=25.022, P＜0.01). The expression in the 72 hours group and reparation group decreased as compared with the 24hours group. ②GLUT-1 expressed weakly in the control group. The expression in the 24 hours group rose a lot as compared with the control group (t=18.314, P＜0.01) and the expression in the 72 hours group rose slightly than that in the 24 hours group (t =2.819, P＜0.05). The expression in the reparation group is close to that in the 24 hours group. ③Littie VEGF content was detected in the control group, while the content rose significantly in the other 3 groups. Immunohistochemical staining showed more VEGF positive stained cells in outer AF than in inner AF.

CONCLUSION:

Continuous pressure can strongly up-regulate the expression of energy metabolism gene HIF-1α,GLUT-1 and VEGF in vivo. These genes play important roles in AF adaptation and reparation in over load-caused damage.