Advances in Comparative Medical Research on Anatomy and Histological Structure of Intervertebral Discs in Humans and Other Animals

Abstract

The 2023 China Health Report on Spine Degeneration noted a significant increase in lumbar surgery among patients under 35 years old in recent years, indicating a trend towards younger onset of cervical and lumbar diseases. Lumbar intervertebral disc herniation has become a major concern, making the study of disc degeneration pathogenesis and treatment methods clinically significant. At present, human intervertebral disc diseases are primarily diagnosed through imaging due to the challenges of obtaining tissue samples from the spine. Therefore, experimental animals have emerged as alternative research subjects because they are cost-effective, have short experimental cycles, and are easily accessible. Given the structural and physiological differences between human and other animal intervertebral discs, comparing their anatomy and histological characteristics forms the foundation of research into human disc degeneration. The purpose of this paper is to collect and review relevant studies on anatomical and histological structures of intervertebral discs in different animals and conduct a comparative analysis from four aspects, namely, intervertebral disc height, lumbar disc geometry, lumbar disc cartilaginous endplate characteristics, and extracellular matrix components. The results show that humans, kangaroos, sheep, pigs, and rats exhibit similar relative heights between the sixth and seventh cervical vertebrae. Mice possess lumbar disc geometries most akin to humans. Compared to other animals, humans have the thickest cartilaginous endplates and the lowest cell densities. The collagen within the fibrous annulus differs most notably in pigs compared to humans, while water content in the nucleus pulposus is consistent across pigs, sheep, rabbits, rats, and humans. Additionally, this paper describes the commonalities and discrepancies in disc degeneration manifestations between humans and animals, and summarizes modeling methods for disc degeneration in different experimental animals. Ultimately, the aims of this paper is to provide fundamental data for selecting suitable experimental animal models for the study of intervertebral disc degeneration.

Keywords

• intervertebral disc
• degeneration
• comparative medicine
• animal model
• anatomy and histology