title: Acute mechanical injury of the human intervertebral disc: link to degeneration and pain.
abstract: Excessive mechanical loading or acute trauma to intervertebral discs (IVDs) is thought to contribute to degeneration and pain. However, the exact mechanisms by which mechanical injury initiates and promotes degeneration remain unclear. This study investigates biochemical changes and extracellular matrix disruption in whole-organ human IVD cultures following acute mechanical injury. Isolated healthy human IVDs were rapidly compressed by 5% (non-injured) or 30% (injured) of disc height. 30% strain consistently cracked cartilage endplates, confirming disc trauma. Three days post-loading, conditioned media were assessed for proteoglycan content and released cytokines. Tissue extracts were assessed for proteoglycan content and for aggrecan integrity. Conditioned media were applied to PC12 cells to evaluate if factors inducing neurite growth were released. Compared to controls, IVD injury caused significant cell death. Injury also caused significantly reduced tissue proteoglycan content with a reciprocal increase of proteoglycan content in culture media. Increased aggrecan fragmentation was observed in injured tissue due to increased matrix metalloproteinase and aggrecanase activity. Injured-IVD conditioned media contained significantly elevated interleukin (IL)-5, IL-6, IL-7, IL-8, MCP-2, GROα, and MIG, and ELISA analysis showed significantly increased nerve growth factor levels compared to non-injured media. Injured-disc media caused significant neurite sprouting in PC12 cells compared to non-injured media. Acute mechanical injury of human IVDs ex vivo initiates release of factors and enzyme activity associated with degeneration and back pain. This work provides direct evidence linking acute trauma, inflammatory factors, neo-innervation and potential degeneration and discogenic pain in vivo.
authors.affiliation: McGill University Health Centre, Department of Surgery, Montreal General Hospital, Room C9.173, 1650 Cedar Ave, Montreal, QC H3G 1A4, Canada.lisbet.haglund@mcgill.ca.
authors.forename: B
authors.initials: B
authors.lastname: Alkhatib
authors.forename: D H
authors.initials: DH
authors.lastname: Rosenzweig
authors.forename: E
authors.initials: E
authors.lastname: Krock
authors.forename: P J
authors.initials: PJ
authors.lastname: Roughley
authors.forename: L
authors.initials: L
authors.lastname: Beckman
authors.forename: T
authors.initials: T
authors.lastname: Steffen
authors.forename: M H
authors.initials: MH
authors.lastname: Weber
authors.forename: J A
authors.initials: JA
authors.lastname: Ouellet
authors.forename: L
authors.initials: L
authors.lastname: Haglund
mesh_terms: D000328:Adult; D016923:Cell Death; D017077:Culture Media, Conditioned / Q000494:pharmacology; D016207:Cytokines / Q000378:metabolism; D016326:Extracellular Matrix Proteins / Q000378:metabolism*; D050724:Fractures, Cartilage / Q000150:complications / Q000378:metabolism; D006801:Humans; D007403:Intervertebral Disc / Q000293:injuries / Q000378:metabolism*; D055959:Intervertebral Disc Degeneration / Q000209:etiology* / Q000378:metabolism; D008875:Middle Aged; D016501:Neurites / Q000187:drug effects; D010146:Pain / Q000209:etiology / Q000378:metabolism; D013314:Stress, Mechanical
chemical_list: D017077:Culture Media, Conditioned; D016207:Cytokines; D016326:Extracellular Matrix Proteins