title: Three dimensional mesoscale analysis of translamellar cross-bridge morphologies in the annulus fibrosus using optical coherence tomography.
abstract: The defining characteristic of the annulus fibrosus (AF) of the intervertebral disc (IVD) has long been the lamellar structures that consist of highly ordered collagen fibers arranged in alternating oblique angles from one layer to the next. However, a series of recent histologic studies have demonstrated that AF lamellae contain elastin- and type VI collagen-rich secondary "cross-bridge" structures across lamellae. In this study, we use optical coherence tomography (OCT) to elucidate the three-dimensional (3-D) morphologies of these translamellar cross-bridges in AF tissues. Mesoscale volumetric images by OCT revealed a 3-D network of heterogeneously distributed cross-bridges. The results of this study confirm the translamellar cross-bridge is identifiable as a distinguishable structure, which lies in the interbundle space of adjacent lamellae and crisscrosses multiple lamellae in the radial direction. In contrast to previously proposed models extrapolated from 2-D sections, results from this current study show that translamellar cross-bridges exist as a complex, interconnected network. We also found much greater variation in lengths of cross-bridges within the interbundle space of lamellae (0.8-1.4 mm from the current study versus 0.3-0.6 mm from 2-D sections). OCT-based 3-D morphology of translamellar cross-bridge provides novel insight into the AF structure.
authors.affiliation: Fischell Department of Bioengineering, University of Maryland, College Park, Maryland; Advanced Biomedical and Welfare Technology R&BD group, Korea Institute of Industrial Technology, Cheonan-si, Chungcheongnam-do, Korea.
authors.forename: Sang Kuy
authors.initials: SK
authors.lastname: Han
authors.forename: Chao-Wei
authors.initials: CW
authors.lastname: Chen
authors.forename: Jerry
authors.initials: J
authors.lastname: Wierwille
authors.forename: Yu
authors.initials: Y
authors.lastname: Chen
authors.forename: Adam H
authors.initials: AH
authors.lastname: Hsieh
mesh_terms: D000818:Animals; D005260:Female; D021621:Imaging, Three-Dimensional; D007403:Intervertebral Disc / Q000033:anatomy & histology*; D012756:Sheep; D041623:Tomography, Optical Coherence / Q000379:methods*
keywords: 3-D morphology; annulus fibrosus; optical coherence tomography; translamellar cross-bridge