An In Vivo Model of Reduced Nucleus Pulposus Glycosaminoglycan Content in the Rat Lumbar Intervertebral Disc

Abstract

Study Design-An in vivo model resembling early stage disc degeneration in the rat lumbar spine.Objective-Simulate the reduced glycosaminoglycan content and altered mechanics observed in intervertebral disc degeneration using a controlled injection of chondroitinase ABC (ChABC).Summary of Background Data-Nucleus glycosaminoglycan reduction occurs early during disc degeneration; however, mechanisms through which degeneration progresses from this state are unknown. Animal models simulating this condition are essential for understanding disease progression and for development of therapies aimed at early intervention.Methods-ChABC was injected into the nucleus pulposus, and discs were evaluated via micro-CT, mechanical testing, biochemical assays, and histology 4 and 12 weeks after injection.Results-At 4 weeks, reductions in nucleus glycosaminoglycan level by 43%, average height by 12%, neutral zone modulus by 40%, and increases in range of motion by 40%, and creep strain by 25% were found. Neutral zone modulus and range of motion were correlated with nucleus glycosaminoglycan. At 12 weeks, recovery of some mechanical function was detected as range of motion and creep returned to control levels; however, this was not attributed to glycosaminoglycan restoration, because mechanics were no longer correlated with glycosaminoglycan.Conclusion-An in vivo model simulating physiologic levels of glycosaminoglycan loss was created to aid in understanding the relationships between altered biochemistry, altered mechanics, and altered cellular function in degeneration.Keywords intervertebral disc; degeneration; nucleus pulposus; glycosaminoglycan; animal model; chondroitinase ABC Intervertebral disc degeneration is a complex progression of structural, biochemical, and biological alterations that contribute to compromised mechanical function and in some instances discogenic low back pain. Despite the prevalence of the condition, with billions of dollars in associated health care costs paid annually in the United States, 1 treatments for disc degeneration and the associated pain are limited, due in part to the lack of a thorough understanding of the mechanisms at play. Among the early degenerative changes is a NIH Public AccessAuthor Manuscript Spine (Phila Pa 1976). Author manuscript; available in PMC 2009 June 15. Published in final edited form as:Spine (Phila Pa 1976 breakdown of large aggregating proteoglycans reducing the sulfated glycosaminoglycan content in the nucleus pulposus. 2-4 This reduction of glycosaminoglycan content has an impact on the mechanical function of the disc: the ability to imbibe and bind water is diminished, pressure within the nucleus is decreased, and ultimately, the mechanical function of the nucleus and the entire motion segment is altered. 5-8 It is plausible that progressive degeneration follows this reduced glycosaminoglycan content and altered mechanics, yet this ultimately remains a hypothesis, and knowledge of specific mechanisms and interactions is limited. To this end, in vivo anima...

Emerging Technologies for Molecular Therapy for Intervertebral Disk Degeneration

“…Rabbit lumbar 76,80–83 and rat caudal discs 84–87 have been used extensively, although other animal models exist. 85,86 Both physical injury, such as stab wound 6,88 or controlled needle puncture, 89,90 and chemical degradation 83–87 approaches have been used.…”

Degenerative Anular Changes Induced by Puncture Are Associated With Insufficiency of Disc Biomechanical Function

“…Transanular approaches have been used to inject enzymatic agents for chemonucleolysis in several animal species, 17,34 -42 including rodents. [43][44][45] It has been suggested that digestion of proteoglycans induces nucleus pulposus (NP) depressurization and loss of tensional stress in the AF, resulting in altered disc mechanics 17,35,46,47 and, consequently, degeneration. Another approach has been partial or full anular stab injury, also performed in a variety of species.…”

A Nucleotomy Model with Intact Annulus Fibrosus to Test Intervertebral Disc Regeneration Strategies

“…16,[23][24][25][26] Lately, proteolytic enzymes including chymopapain, trypsin and papain, and chondroitinase ABC have been used for various applications. 16 This article has been peer-reviewed and accepted for publication, but has yet to undergo copyediting and proof correction.…”