Effects of cyclic dynamic tensile strain on previously compressed inner annulus fibrosus and nucleus pulposus cells of human intervertebral disc-an in vitro study

Abstract

Our objective was to investigate whether dynamic tensile strain on previously compressed human intervertebral disc (IVD) cells can restore the biosynthetic effects of collagen and glycosaminoglycan. Inner annulus fibrosus (AF) and nucleus pulposus (NP) tissues of adolescent idiopathic scoliosis cases undergoing thoracoscopic discectomy and fusion were cultured on compressive plates. Compressive stress was applied using 0.4 MPa at 1 Hz, for 2 h twice a day for 7 days, to the inner AF and NP tissues, followed by equibiaxial cyclic tensile strain to deform the released cells onto the plate's flexible bottom. With 10% elongation at a rate of 1 Hz, for 2 h twice a day for 7 days, a significant increase in the level of collagen and glycosaminoglycan of the previously compressed inner AF, as well as the level of glycosaminoglycan of the previously compressed NP cells were found. The DNA content and number of endoplasmic reticulum under transmission electron micrograph of the previously compressed inner AF and NP cell were also significantly increased. The results suggested that equibiaxial cyclic tensile strain at a rate of 1 Hz with 10% tensile strain was capable of increasing collagen and glycosaminoglycan synthesis of previously compressed inner AF cells, and glycosaminoglycan synthesis of previously compressed NP cells.