Autophagy in the Degenerating Human Intervertebral Disc. Issue 11 (1st June 2015)

• Record Type: Journal Article
• Authors: Gruber, Helen E.; Hoelscher, Gretchen L.; Ingram, Jane A.; Bethea, Synthia; Hanley, Edward N.
• Is Part Of: Spine. Volume 40:Issue 11(2015)
• Publication Date: 2015-06-01
• Subjects: Spine -- Abnormalities -- Periodicals; Spine -- Diseases -- Periodicals; Spine -- Surgery -- Periodicals; 616.73005
• DOI: 10.1097/BRS.0000000000000865
• Languages: English
• ISSNs: 0362-2436

Abstract

<abstract> <title> <x xml:space="preserve">Abstract</x> </title> <sec> <title>Study Design.</title> <p>Autophagy-related gene expression and ultrastructural features of autophagy were studied in human discs.</p> </sec> <sec> <title>Objective.</title> <p>To obtain molecular/morphological data on autophagy in human disc degeneration and cultured human annulus cells exposed to proinflammatory cytokines.</p> </sec> <sec> <title>Summary of Background Data.</title> <p>Autophagy is an important process by which cytoplasm and organelles are degraded; this adaptive response to sublethal stresses (such as nutrient deprivation present in disc degeneration) supplies needed metabolites. Little is known about autophagic processes during disc degeneration.</p> </sec> <sec> <title>Methods.</title> <p>Human disc specimens were obtained after institutional review board approval. Annulus mRNA was analyzed to determine autophagy-related gene expression levels. Immunolocalization and ultrastructural studies for p62, ATG3, ATG4B, ATG4C, ATG7, L3A, ULK-2, and beclin were conducted. <italic>In vitro</italic> experiments used IL-1β- or TNF-α–treated human annulus cells to test for autophagy-related gene expression.</p> </sec> <sec> <title>Results.</title> <p>More degenerated <italic>versus</italic> healthier discs showed significantly greater upregulation of well-recognized autophagy-related genes (<italic>P</italic> ⩽ 0.028): beclin 1 (upregulated 1.6-fold); ATG8 (LC3) (upregulated 2.0-fold); ATG12 (upregulated 4.0-fold); presenilin 1 (upregulated 1.6-fold); cathepsin B (upregulated 4.5-fold). p62 was localized, and ultrastructure showed autophagic vacuolization and autophagosomes with complex, redundant whorls of membrane-derived material. <italic>In vitro</italic>, proinflammatory cytokines significantly upregulated autophagy-related genes (<italic>P</italic> ⩽ 0.04): DRAM1 (6.24-fold); p62 (4.98-fold); PIM-2 oncogene, a positive regulator of autophagy (3-fold); WIPI49 (linked to starvation-induced autophagy) (upregulated 2.3-fold).</p> </sec> <sec> <title>Conclusion.</title> <p>Data provide initial molecular and morphological evidence for the presence of autophagy in the degenerating human annulus. <italic>In vivo</italic> gene analyses showed greater autophagy-related gene expression in more degenerated than healthier discs. <italic>In vitro</italic> data suggested a mechanism implicating a role of TNF-α and IL-1β in disc autophagy. Findings suggest the importance of future work to investigate the relationship of autophagy to apoptosis, cell death, cell senescence, and mitochondrial dysfunction in the aging and degenerating disc.</p> <p> <bold>Level of Evidence:</bold> N/A</p> </sec> </abstract>