title: Mineralization and collagen orientation throughout aging at the vertebral endplate in the human lumbar spine.
abstract: The human vertebral body and intervertebral disc interface forms the region where the cartilaginous endplate, annulus fibrosis and bone of the vertebral body are connected through an intermediate calcified cartilage layer. While properties of both the vertebral body and components of the disc have been extensively studied, limited quantitative data exists describing the microstructure of the vertebral body-intervertebral disc interface in the spine throughout development and degeneration. Quantitative backscattered scanning electron and second harmonic generation confocal imaging were used to collect quantitative data describing the mineral content and collagen fiber orientation across the interface, respectively. Specimens spanned ages 56 days to 84 years and measurements were taken across the vertebral endplate at the outer annulus, inner annulus and nucleus pulposis. In mature and healthy endplates, collagen fibers span the calcified cartilage layer in all regions, including the endplate adjacent to the central nucleus pulposis. We also observed an abrupt transition from high mineral volume fractions (35-50%) to 0% over short distances measuring 3-15 microns in width across the transition from calcified cartilage to unmineralized cartilage. The alignment of collagen fibers at the outer annulus and thickness of the CC layer indicated that collagen fiber mineralization adjacent to the bone may serve to anchor the soft tissue without a gradual change in material properties. Combining backscattered scanning electron microscopy and second harmonic generation imaging on the same sections thus enable a novel assessment of morphology and properties in both mineralized and soft tissues at the vertebral body-intervertebral disc throughout development and aging.
authors.affiliation: Department of Mechanical Engineering, University of Colorado at Boulder, United States.
authors.forename: Rachel C
authors.initials: RC
authors.lastname: Paietta
authors.forename: Evalina L
authors.initials: EL
authors.lastname: Burger
authors.forename: Virginia L
authors.initials: VL
authors.lastname: Ferguson
mesh_terms: D000293:Adolescent; D000328:Adult; D000369:Aged, 80 and over; D000375:Aging; D002113:Calcification, Physiologic; D003094:Collagen / Q000378:metabolism / Q000648:ultrastructure; D005260:Female; D006801:Humans; D007223:Infant; D007403:Intervertebral Disc / Q000000981:diagnostic imaging / Q000502:physiology* / Q000648:ultrastructure; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging / Q000502:physiology* / Q000648:ultrastructure; D008297:Male; D008875:Middle Aged; D055114:X-Ray Microtomography
chemical_list: D003094:Collagen
keywords: AF; Aging; Annulus fibrosis; BV/TV; Bone; CC; CEP; Cartilage endplate; IAF; IVD; MinVf; NP; Nucleus pulposis; OAF; OC; Osteochondral; Quantitative backscattered scanning electron imaging; RA; SCB; SHG; SMI; Second harmonic generation; VB; WMGL; annulus fibrosis; calcified cartilage; cartilage endplate; inner annulus fibrosis; intervertebral disc; mineral volume fraction; nucleus pulposis; osteochondral; outer annulus fibrosis; qBSE; quantitative backscattered scanning electron; ratio of bone volume to total volume; ring apophysis; second harmonic generation; structural model index; subchondral bone; vertebral body; weighted mean grey level