Elsevier

The Spine Journal

Volume 5, Issue 6, Supplement, November–December 2005, Pages S267-S279
The Spine Journal

II. Disc Regeneration
Animal models for human disc degeneration

https://doi.org/10.1016/j.spinee.2005.02.016Get rights and content

Abstract

Despite the significant impairment associated with degenerative disc disease, a clear understanding of its pathogenesis is still lacking. Currently, no particular model parallels the complex nature of human disc degeneration. Naturally occurring animal models have the drawback that the basis for the high rate of disc degeneration is not known. Although the interventions in artificial animal models that create disc degeneration are known, the relationship of those to the events leading to disc degeneration in humans is not. With the recent progress in biomechanics, cell biology and molecular biology, an easily reproducible and valid animal model may help unlock the complex cascade of events surrounding human disc degeneration.

Introduction

Intervertebral disc degeneration is a chief cause of musculoskeletal disability in humans [1]. The macroscopic features characterizing disc degeneration include the formation of tears within the anulus substance and progressive fraying and dehydration of the nucleus pulposus (NP) [2], [3], [4]. Despite the significant impairment associated with this disease, a clear understanding of the basic mechanisms of disease pathogenesis and specific therapeutic agents is still lacking. Unquestionably, disc degeneration is a multifactorial process influenced by genetics, lifestyle conditions (including obesity, occupation, smoking and alcohol consumption) [1], [2], [3], [4], [5], [6], biomechanical loading and activities, and other health factors (diabetes and aging). The availability of an experimental animal model that consistently reproduces the disease would facilitate the investigations of intervertebral disc degeneration. This paper is an overview of the reported animal models that have been used to evaluate human disc degeneration.

Section snippets

Intervertebral disc anatomy

The intervertebral disc acts as a load-bearing structure with two distinct components; the NP and the anulus fibrosus (AF). Each component has distinct biomechanical properties. The NP, rich in proteoglycan, acts as an internal semifluid mass, whereas the AF, rich in collagen, acts as a laminar fibrous container [5]. The hydrostatic properties of the disc arise from its high water content. The NP, when palpated in a young adult, acts as a viscid fluid under applied pressure but also exhibits

Animal models: requirements and selection

Animal models are essential in making the transition from scientific concepts to clinical applications. In vitro studies or computer simulations may initially test emerging technology concepts to minimize the use of animals. However, the safety and effectiveness of these paradigms need to be validated using appropriate animal models. Certain fundamental principles must be adhered to for an animal model to be effective. The animal model must be ethical, controllable, reproducible and

Categories of animal models for disc degeneration

Animal models of human disc degeneration can be subdivided into two main categories: naturally occurring and experimentally induced (Table 1).

Conclusion

Many techniques have been applied to develop a successful, experimental animal model of human disc degeneration. However, no particular model currently parallels the complex nature of human disc degeneration. Naturally occurring animal models have the drawback that the basis for the high rate of disc degeneration is not known. The availability of animals is based on the rate of occurrence, and so a predictable experiment is difficult. Although the interventions in artificial animal models are

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