Dynamic elastic modulus assessment of the early degeneration model of an intervertebral disc in cynomolgus monkeys with one strike loading.

OBJECTIVE: Disc degeneration has long been associated with excessive mechanical loading or acute disc injury. Our goal is to perform a shock load on the functional units of the cynomolgus monkey intervertebral disc and analyze the degree of degeneration of the intervertebral disc through image analysis and comprehensive analysis. The organ model establishes a standard organ culture model and a non-invasive biomechanical evaluation protocol close to the early degeneration of the human intervertebral disc. METHODS: After modeling, the cynomolgus monkey intervertebral discs were collected and loaded into the dynamic mechanical culture system. The physiological group was loaded with 10% high compressive deformation load for one second, the injury group was punctured with annulus fibrosus, the model group was loaded with 20-50% high compressive deformation, and the nutritional components were a high-glucose group and low-glucose group. After day 3 (short term) and day 10 (long term), samples were collected to analyze cell viability, histomorphology, image analysis for imaging and biomechanical changes. RESULTS: Both the injury group and the 30-50% strain model group showed signs of early degeneration, including decreased instantaneous compressive stiffness, percent change in gray value, decreased cell viability, AF fissure, and percent increase in dynamic elastic modulus. The glucose-restricted group also showed signs of early disc degeneration in long-term cultures. CONCLUSION: This study shows that a single shock load can induce early degeneration of healthy cynomolgus monkey intervertebral discs, and 30% strain may be the nociceptive threshold for early degeneration of healthy intervertebral discs. More importantly, a non-invasive biomechanical evaluation scheme of Percentage change in dynamic modulus of elasticity is established, which solves the key scientific problem of how to non-invasively, quantitatively and sensitively detect the development process of early intervertebral disc degeneration and its degree of degeneration in an in vitro organ model.

One strike loading organ culture model to investigate the post-traumatic disc degenerative condition.

BACKGROUND: Acute trauma on intervertebral discs (IVDs) is thought to be one of the risk factors for IVD degeneration. The pathophysiology of IVD degeneration induced by single high impact mechanical injury is not very well understood. The aim of this study was using a post-traumatic IVD model in a whole organ culture system to analyze the biological and biomechanical consequences of the single high-impact loading event on the cultured IVDs. METHODS: Isolated healthy bovine IVDs were loaded with a physiological loading protocol in the control group or with injurious loading (compression at 50% of IVD height) in the one strike loading (OSL) group. After another 1 day (short term) or 8 days (long term) of whole organ culture within a bioreactor, the samples were collected to analyze the cell viability, histological morphology and gene expression. The conditioned medium was collected daily to analyze the release of glycosaminoglycan (GAG) and nitric oxide (NO). RESULTS: The OSL IVD injury group showed signs of early degeneration including reduction of dynamic compressive stiffness, annulus fibrosus (AF) fissures and extracellular matrix degradation. Compared to the control group, the OSL model group showed more severe cell death (P â€‹< â€‹0.01) and higher GAG release in the culture medium (P â€‹< â€‹0.05). The MMP and ADAMTS families were up-regulated in both nucleus pulposus (NP) and AF tissues from the OSL model group (P â€‹< â€‹0.05). The OSL injury model induced a traumatic degenerative cascade in the whole organ cultured IVD. CONCLUSIONS: The present study shows a single hyperphysiological mechanical compression applied to healthy bovine IVDs caused significant drop of cell viability, altered the mRNA expression in the IVD, and increased ECM degradation. The OSL IVD model could provide new insights into the mechanism of mechanical injury induced early IVD degeneration. THE TRANSLATIONAL POTENTIAL OF THIS ARTICLE: This model has a high potential for investigation of the degeneration mechanism in post-traumatic IVD disease, identification of novel biomarkers and therapeutic targets, as well as screening of treatment therapies.