Researchers observed how different magnitudes of compressive stress affected human intervertebral disc cell biosynthesis. The findings of this study 1 indicate that biosynthetic characteristics of human inner annulus fibrosus and nucleus pulposus cells may depend on the degree of compressive stress applied, which may result in the secretion of varying amounts of extracellular matrix.
Past studies using animal intervertebral disc tissue have indicated that intervertebral disc cells have different biological responses to compressive stress depending on its type, magnitude, duration, and anatomic zone of intervertebral disc cell origin. The purpose of this study is to assess how human intervertebral disc tissue responds to compressive stress.
Human thoracic intervertebral disc samples were taken from 15 patients with adolescent idiopathic scoliosis who were undergoing anterior thoracoscopic discectomy and fusion. These samples were cultured under 0.2 or 0.4 MPa of compressive stress at 1 Hz for 2 hours twice a day for 7 days. These were compared to the control group samples, which did not undergo compressive stress. The outcome was measured by examining cell morphology, cell proliferation assay, and collagen and glycosaminoglycan content in vitro.
Cells cultured under 0.2 MPa of compressive stress showed a higher collagen and glycosaminoglycan content in the inner annulus fibrosus and nucleus pulposus cells than in the control cells, while cells cultured under 0.4 MPa of compressive stress showed lower collagen and glycosaminoglycan content than in the control cells. Cells cultured under 0.2 MPa of compressive stress showed higher numbers of endoplasmic reticulum compared to the control group, while cells cultured under 0.2 MPa of compressive stress showed lower numbers of endoplasmic reticulum.
When inner annulus fibrosus and nucleus pulposus cells were exposed to moderate compressive stress magnitudes, increased biosynthesis occurred, whereas high compressive stress magnitudes lead to decreased biosynthesis in the inner annulus fibrosus and nucleus pulposus cells. These results suggest that compressive stress is important for the regulation of collagen and glycosaminoglycan content.
KEYWORDS: Intervertebral disc, Annulus fibrosus, Nucleus pulposus, Compressive Stress, Biosynthesis, Collagen, Glycosaminoglycan, Endoplasmic reticulum